结果:找到“SIAM”相关内容127个,排序为按回复时间降序,搜索更多相关帖子请点击“高级
2017年美国大学生数学建模竞赛O奖论文 pdf下载
1 个回复 - 2450 次查看 美国大学生数学建模竞赛(MCM/ICM)美国大学生数学建模竞赛由美国数学及其应用联合会主办,是唯一的国际性数学建模竞赛,也是世界范围内最具影响力的数学建模竞赛。赛题内容涉及经济、管理、环境、资源、生态、医学、 ...2018-2-2 15:01 - 吃瓜的shu - 现金交易版
2022年Siamgas And Petrochemicals企业数据分析
0 个回复 - 13539 次查看 2022-12-24 03:09 - ewfwedwd - 现金交易版
Siamgas And Petrochemicals企业分析报告
0 个回复 - 14788 次查看 2022-11-25 10:30 - 完全的撒 - Forum
SIAM+On uniform approximation of the binomial distribution by infintely divisibl
1 个回复 - 463 次查看 【作者(必填)】I. P. Tsaregradskii[/backcolor] 【文题(必填)】On Uniform Approximation of the Binomial Distribution by Infinitely Divisible Laws 【年份(必填)】Theory of Probability & Its Application ...2022-9-30 14:42 - scottan123456 - 求助成功区
MOS-SIAM Series on Optimization
10 个回复 - 5722 次查看 MOS-SIAM Series on Optimization MP01Trust Region MethodsAuthor(s): AndrewR. Conn, Nicholas I. M. Gould, and Philippe L. Toint,Published:2000MP02Lectures on Modern Convex Optimization: Analysis, Algor ...2017-7-20 06:49 - liucg9999 - 数据分析与数据挖掘
求助SIAM文献1篇:Relatively Stable Walks
1 个回复 - 438 次查看 【作者(必填)】B. A. Rogozin 【文题(必填)】Relatively Stable Walks 【年份(必填)】Theory Probab. Appl., 21(2), 375–379. (5 pages) 【全文链接或数据库名称(选填)】Relatively Stable Walks | Theory ...2021-12-19 20:48 - scottan123456 - 求助成功区
Numerical Linear Algebra (Siam)
4 个回复 - 2525 次查看 Numerical Linear Algebra by Lloyd Trefethen and David Bau (pdf)2013-6-19 06:03 - ParanoidAndroid - 计量经济学与统计软件
【应用数学,SIAM】 The Shapes of Things: A Practical Guide to Differential Geome
17 个回复 - 1997 次查看 The Shapes of Things: A Practical Guide to Differential Geometry and the Shape Derivative Authors: Shawn W. Walker Many things around us have properties that depend on their shape—for examp ...2016-11-18 03:26 - cmwei333 - 经济金融数学专区
The siamese twins: Do state-owned banks favor state-owned enterprises in China
2 个回复 - 770 次查看 【作者(必填)】 Shang-Jin Wei , Tao Wang 【文题(必填)】The siamese twins: Do state-owned banks favor state-owned enterprises in China 【年份(必填)】1997 【全文链接或数据库名称(选填)】http:/ ...2016-1-10 14:31 - choukoei - 求助成功区
【下载】Bayesian Statistics A Review~D.V.Lindley.SIAM.1987
5 个回复 - 2077 次查看 Bayesian statistics;: A review (Regional conference series in applied mathematics) (Unknown Binding) D. V Lindley (Author) Editorial Reviews Product Description A study of those statistical idea ...2010-6-4 08:04 - kxjs2007 - 计量经济学与统计软件
siam论文The Arithmetic of Probability Distributions
3 个回复 - 30712 次查看 【作者(必填)】I. V. Ostrovskii 【文题(必填)】The Arithmetic of Probability Distributions 【年份(必填)】1985 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/11310012013-5-16 14:39 - 352693585 - 求助成功区
A Beck, First-Order Methods in Optimization, SIAM, 2017
0 个回复 - 718 次查看 跪求A Beck, First-Order Methods in Optimization, SIAM, 2017 附件是John Hull的金融衍生品定价参考书配套答案2022-9-9 18:38 - harvester - 金融工程(数量金融)与金融衍生品
Springer & SIAM Book Series On Optimization
1 个回复 - 3641 次查看 Springer Optimization方面的书籍。 残缺的部分一旦发现会马上更新。 1.Adaptation, Learning, and Optimization【20 volumes】 下载 2.Proceedings in Adaptation, Learning and Optimization【9 volumes】下 ...2017-7-3 07:32 - liucg9999 - 数据分析与数据挖掘
基于内容的Siamese神经网络音频表示
0 个回复 - 314 次查看 摘要翻译: 本文主要研究基于内容的音频检索问题,目的是针对给定的音频剪辑查询,检索所有语义相似的音频记录。这个问题类似于音频示例查询问题,其目的是从数据库中检索媒体样本,这些样本类似于用户提供的示例。我 ...2022-3-4 15:31 - kedemingshi - Forum
2021年Asiamold广州国际模具展览会蓄势待发,揭示行业趋势新动向
0 个回复 - 415 次查看 2021年Asiamold广州国际模具展览会蓄势待发,揭示行业趋势新动向 广州国际模具展(Asiamold)将于2021年3月3至5日在广州中国进出口商品交易会展馆举办,展示来自海内外领先品牌最新的模具制造、3D 打印及压铸等技术 ...2021-1-27 15:43 - huaya2015 - 学术资源/课程/会议/讲座
The siamese-twins: Do state-owned banks favor state-owned enterprises in China?
2 个回复 - 1307 次查看 【作者(必填)】 SJ Wei, T Wang 【文题(必填)】 The siamese-twins: Do state-owned banks favor state-owned enterprises in China?【年份(必填)】 1997 【全文链接或数据库名称(选填)】 China Economic R ...2017-5-22 12:49 - yanwenshou - 求助成功区
SIAM 文献 2 篇
1 个回复 - 685 次查看 【题 名】:A Method of Second-Order Accuracy Integration of Stochastic Differential Equations 【作 者】G. N. Mil’shtein 【期刊、会议、单位名称】Theory Probab. Appl., 【年, 卷(期), 起止页码】:2 ...2015-4-30 09:52 - phdcs_2008 - 求助成功区
SIAM.Data.Clustering.Theory.Algorithms.and.Applications.May.2007
4 个回复 - 3265 次查看 第一章 Clustering,DATA,and Similarity measures 1、 DATA Clustering2、Data Types 3、Scale Conversion 4、DATA standardization and transformation 5、DATA Visualization Similarity and Dissimilarity ...2010-12-13 20:41 - rambler_hh - 商业数据分析
求助SIAM数据库文献一枚
1 个回复 - 494 次查看 【作者(必填)】 Xinsong Yang, Jinde Cao, and Zhichun Yang 【文题(必填)】 Synchronization of Coupled Reaction-Diffusion Neural Networks with Time-Varying Delays via Pinning-Impulsive Controller 【 ...2014-10-21 17:24 - lianghongjing - 求助成功区
2014年Asiamold广州国际模具展览会 聚焦3D打印及应用技术专区
0 个回复 - 969 次查看 2014-09-01 广州国际模具展 广州国际模具展览会  【广州光亚法兰克福:http://www.gymf.com.cn】Asiamold - 广州国际模具展览会一向以汇聚环球知名品牌模具方案而见称,展会结合法兰克福展 ...2014-9-1 15:51 - gymf - 休闲灌水
siam On the Accuracy of the Normal Approximation to Compound Poisson
1 个回复 - 655 次查看 【作者(必填)】I. G. Shevtsova 【文题(必填)】On the Accuracy of the Normal Approximation to Compound Poisson Distributions 【年份(必填)】2014 【全文链接或数据库名称(选填)】http://epubs.siam.o ...2014-5-9 15:33 - 352693585 - 求助成功区
siam On Poisson Sequences of Chance Events
1 个回复 - 886 次查看 【作者(必填)】A. Ya. Khinchin 【文题(必填)】On Poisson Sequences of Chance Events 【年份(必填)】1956 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/11010232014-2-5 17:40 - 352693585 - 求助成功区
siam Sequences of Chance Events without After-Effects
1 个回复 - 878 次查看 【作者(必填)】A. Ya. Khinchin 【文题(必填)】Sequences of Chance Events without After-Effects 【年份(必填)】1955 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/11010012014-2-5 17:43 - 352693585 - 求助成功区
siam On the Convergence of Sums of Random Step Processes
1 个回复 - 1096 次查看 【作者(必填)】B. Grigelionis 【文题(必填)】On the Convergence of Sums of Random Step Processes to a Poisson Process 【年份(必填)】1961 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/ab ...2014-2-5 17:44 - 352693585 - 求助成功区
siam The Distribution of the First Ladder Moment and Height and Fluctuation
1 个回复 - 909 次查看 【作者(必填)】B. A. Rogozin 【文题(必填)】The Distribution of the First Ladder Moment and Height and Fluctuation of a Rand 【年份(必填)】1970 【全文链接或数据库名称(选填)】 http://epubs.siam.or ...2014-2-3 00:53 - 352693585 - 求助成功区
siam On an Estimate of the Concentration Function of a Sum of Independent
1 个回复 - 750 次查看 【作者(必填)】V. V. Petrov 【文题(必填)】On an Estimate of the Concentration Function of a Sum of Independent Random Variables 【年份(必填)】1969 【全文链接或数据库名称(选填)】http://epubs.si ...2014-1-11 03:30 - 352693585 - 求助成功区
求文献一篇siam的
1 个回复 - 738 次查看 【作者(必填)】 C. C. Lin and L. A. Segel 【文题(必填)】 Mathematics Applied to Deterministic Problems in the Natural Sciences ...2013-12-23 00:07 - icelee - 求助成功区
siam Convergence of Random Processes and Limit Theorems in Probability Theory
1 个回复 - 1565 次查看 【作者(必填)】Yu. V. Prokhorov 【文题(必填)】Convergence of Random Processes and Limit Theorems in Probability Theory[/backcolor] 【年份(必填)】1956 【全文链接或数据库名称(选填)】http://epub ...2013-11-28 00:35 - 352693585 - 求助成功区
siam Poisson approximation via the convolution with Kornya–Presman
1 个回复 - 601 次查看 【作者(必填)】B. Roos 【文题(必填)】Poisson approximation via the convolution with Kornya–Presman signed measures 【年份(必填)】2006 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/a ...2013-11-1 14:44 - 352693585 - 求助成功区
求助SIAM资料一篇
1 个回复 - 642 次查看 【作者(必填)】Jeffrey L. Stuart 【文题(必填)】Inflation Matrices and ZME-Matrices that Commute with a Permutation Matrix 【年份(必填)】SIAM. J. Matrix Anal. & Appl., 9(3), 408–418. (11 pages) ...2013-10-20 17:24 - xinchuzu - 求助成功区
SIAM J. Optim. 20, 1885–1905 (2010)
1 个回复 - 994 次查看 【作者(必填)】Ye, J.J., Zhu, D.L. 【文题(必填)】 New necessary optimality conditions for bilevel programs by combining MPECand the value function approach. 【年份(必填)】SIAM J. Optim. 20, 1885 ...2013-9-15 17:28 - yang2009jing - 求助成功区
SIAM Journal on Optimization, 2010, 20(4): 1885-1905.
1 个回复 - 1017 次查看 【作者(必填)】Ye J J, Zhu D. 【文题(必填)】 New necessary optimality conditions for bilevel programs by combining the MPEC and value function approaches[J]. 【年份(必填)】SIAM Journal on Optimi ...2013-9-13 10:57 - yang2009jing - 求助成功区
SIAM Journal on Optimization
1 个回复 - 1002 次查看 【作者(必填)】Li W. 【文题(必填)】 Abadie's constraint qualification, metric regularity, and error bounds for differentiable convex inequalities. SIAM Journal on Optimization, 1997, 7(4): 966-978. ...2013-8-28 15:23 - yang2009jing - 求助成功区
SIAM Normal and Poisson convergencies
2 个回复 - 678 次查看 【作者(必填)】VM Kruglov 【文题(必填)】Normal and Poisson convergencies 【年份(必填)】2004 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/S0040585X979804402013-8-21 13:40 - 352693585 - 求助成功区
SIAM Journal on Optimization, 2010, 20(5): 2730-2753.
1 个回复 - 937 次查看 【作者(必填)】Kanzow C, Schwartz A. 【文题(必填)】Mathematical programs with equilibrium constraints: enhanced Fritz John-conditions, new constraint qualifications, and improved exact penalty resu ...2013-8-12 20:33 - yang2009jing - 求助成功区
siam Approximation of Binomial Distributions
1 个回复 - 713 次查看 【作者(必填)】E. L. Presman 【文题(必填)】Approximation of Binomial Distributions by Infinitely Divisible Ones 【年份(必填)】1983 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/1 ...2013-8-11 19:00 - 352693585 - 求助成功区
siam论文 Approximation of a generalized binomial distribution
3 个回复 - 814 次查看 【作者(必填)】S. Ya. Šorgin 【文题(必填)】Approximation of a generalized binomial distribution 【年份(必填)】1977 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/112 ...2013-6-2 12:15 - 352693585 - 求助成功区
求助SIAM 1993年文献一篇,非常感谢帮忙!
1 个回复 - 668 次查看 【作者(必填)】 Hettich, R. and Kortanek, K. (doi: 10.1137/1035089) 【文题(必填)】 Semi-Infinite Programming: Theory, Methods, and Applications 【年份(必填)】 1993, Vol. 35, No. 3 : pp. 380-429 ...2013-5-15 21:13 - lyx0302205 - 求助成功区
siam Quasi-Moment Functions
1 个回复 - 829 次查看 【作者(必填)】P. I. Kuznetsov 【文题(必填)】1958 【年份(必填)】Quasi-Moment Functions in the Theory of Random Processes 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/110 ...2013-5-12 01:40 - 352693585 - 求助成功区
siam On the Factorization of Infinitely Divisible Distributions
1 个回复 - 579 次查看 【作者(必填)】A. E. F. 【文题(必填)】On the Factorization of Infinitely Divisible Distributions 【年份(必填)】1975 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/11200732013-5-9 15:05 - 352693585 - 求助成功区
siam Multimodal Convolutions of Unimodal Infinitely Divisible Distributions
2 个回复 - 686 次查看 【作者(必填)】sato 【文题(必填)】Multimodal Convolutions of Unimodal Infinitely Divisible Distributions 【年份(必填)】1993 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/ ...2013-5-8 20:07 - 352693585 - 求助成功区
siam论文 On the Decomposition of the Convolution of Gaussian and Poissonian
2 个回复 - 692 次查看 【作者(必填)】Yu. V. Linnik 【文题(必填)】On the Decomposition of the Convolution of Gaussian and Poissonian 【年份(必填)】1957 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10 ...2013-5-8 10:15 - 352693585 - 求助成功区
SIAM论文一篇
4 个回复 - 961 次查看 【作者(必填)】Yu. V. Linnik 【文题(必填)】General Theorems on the Factorization of Infinitely Divisible Laws II 【年份(必填)】1957 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/ ...2013-4-26 19:20 - 352693585 - 求助成功区
siam一篇
1 个回复 - 671 次查看 【作者(必填)】Yu. V. Linnik 【文题(必填)】General Theorems on the Factorization of Infinitely Divisible Laws III 【年份(必填)】1957 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs ...2013-4-26 19:21 - 352693585 - 求助成功区
siam论文General Theorems on the Factorization
2 个回复 - 830 次查看 【作者(必填)】Yu. V. Linnik 【文题(必填)】General Theorems on the Factorization of Infinitely Divisible Laws I 【年份(必填)】1957 【全文链接或数据库名称(选填)】http://epubs.siam.org/action/sh ...2013-4-26 19:16 - 352693585 - 求助成功区
siam论文On a method of expansion of the probabilities
1 个回复 - 738 次查看 【作者(必填)】Sh. Yakshyavichus 【文题(必填)】On a method of expansion of the probabilities of lattice random variables 【年份(必填)】1998 【全文链接或数据库名称(选填)】http://epubs.siam.org/ ...2013-4-14 15:58 - 352693585 - 求助成功区
siam论文On Uniform Approximation of the Binomial Distribution
1 个回复 - 706 次查看 【作者(必填)】I. P. Tsaregradskii 【文题(必填)】On Uniform Approximation of the Binomial Distribution by Infinitely Divisible Laws 【年份(必填)】1958 【全文链接或数据库名称(选填)】http://ep ...2013-4-14 13:21 - 352693585 - 求助成功区
siam论文On the Decomposition of Lattice Distributions
1 个回复 - 752 次查看 【作者(必填)】D. N. Karymov 【文题(必填)】On the Decomposition of Lattice Distributions into Convolutions of Poisson Signed Measures 【年份(必填)】2006 【全文链接或数据库名称(选填)】http://ep ...2013-4-14 13:24 - 352693585 - 求助成功区
siam论文Cauchy Equation on Discrete Domain
1 个回复 - 655 次查看 【作者(必填)】R. Dasgupta 【文题(必填)】Cauchy Equation on Discrete Domain and Some Characterization Theorems 【年份(必填)】1991 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10 ...2013-4-13 23:36 - 352693585 - 求助成功区
siam论文Riemann–Lebesgue lemma
1 个回复 - 960 次查看 【作者(必填)】Maurice H. P. M. Van Putten 【文题(必填)】A Riemann Sum Upper Bound in the Riemann--Lebesgue Theorem 【年份(必填)】2006 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/a ...2013-4-10 13:52 - 352693585 - 求助成功区
siam论文Decomposition of the Convolution
1 个回复 - 699 次查看 【作者(必填)】Fel’dman 【文题(必填)】Decomposition of the Convolution of Two Poisson Distributions on a Locally Compact Abelian Group Read More: http://epubs.siam.org/doi/abs/10.1137/1126067 ...2013-4-10 10:30 - 352693585 - 求助成功区
siam论文Approximation by the Compound Poisson Law
1 个回复 - 751 次查看 【作者(必填)】A. K. Aleskeviciene 【文题(必填)】Approximation by the Compound Poisson Law 【年份(必填)】2005 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/S0040585X97981 ...2013-4-10 09:23 - 352693585 - 求助成功区
求siam文献The Arithmetic of Probability Distributions
1 个回复 - 661 次查看 【作者(必填)】I. V. Ostrovskii 【文题(必填)】The Arithmetic of Probability Distributions 【年份(必填)】1985 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/11310012013-3-23 19:36 - 352693585 - 求助成功区
SIAM库中关于Folkman数的外文文献一篇
4 个回复 - 730 次查看 【作者(必填)】J. Folkman 【文题(必填)】Graphs with monochromatic complete subgraphs in every edge coloring 【年份(必填)】1970 【全文链接或数据库名称(选填)】 全文链接:http://epubs.siam.org ...2013-1-26 18:22 - lzguo99 - 求助成功区
SIAM 1篇
1 个回复 - 625 次查看 【作者(必填)】Langberg, N. and Singpurwalla, N. 【文题(必填)】A Unification of Some Software Reliability Models 【年份(必填)】SIAM Journal on Scientific and Statistical Computing, 1985, Vol. 6, No ...2013-1-6 17:53 - phdcs_2008 - 求助成功区
求siam文献A Note on Infinitely Divisible Distributions
1 个回复 - 681 次查看 【作者(必填)】V. M. Kruglov 【文题(必填)】A Note on Infinitely Divisible Distributions 【年份(必填)】1968 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/11150382012-11-26 20:56 - 352693585 - 求助成功区
求siam文献A Conjectured Definite Integral
1 个回复 - 717 次查看 【作者(必填)】C. J. Bouwkamp 【文题(必填)】A Conjectured Definite Integral 【年份(必填)】1986 【全文链接或数据库名称(选填)】http://epubs.siam.org/doi/abs/10.1137/10281652012-11-26 20:57 - 352693585 - 求助成功区
30论坛币求助英文文献SIAM上的论文
0 个回复 - 769 次查看 求助SIAM中的文献1986年的,我们学校只买了1994年后的;那位帮忙找下,不胜感激; 电子连接:http://epubs.siam.org/doi/abs/10.1137/0324067?journalCode=sjcodc 基本信息: SIAM J. Control Optim ...2012-11-25 20:34 - 向修海 - 悬赏大厅
SIAM 1 篇
1 个回复 - 556 次查看 【作者(必填)】I. A. Ibragimov 【文题(必填)】A Note on the Central Limit Theorems for Dependent Random Variables 【年份(必填)】Theory Probab. Appl., 1975,20(1), 135–141. 【全文链接或数据库名 ...2012-9-11 02:29 - phdcs_2008 - 求助成功区
SIAM文献一篇 谢谢
3 个回复 - 779 次查看 【作者(必填)】Bernt Oksendal Agnès Sulem 【文题(必填)】Optimal Consumption and Portfolio with Both Fixed and Proportional Transaction Costs 【年份(必填)】SIAM Journal on Control ...2012-9-6 11:05 - weilinhy - 求助成功区
求一篇siam上的文献
2 个回复 - 869 次查看 【题目】Self-sorting in-place Fast Fourier Transforms 【链接】http://epubs.siam.org/sisc/resource/1/sjoce3/v12/i4/p808_s1?isAuthorized=no 十分感谢!2011-8-23 16:42 - rederry - 求助成功区
求助 SIAM J. on Scientific Computing 文献
2 个回复 - 874 次查看 急需Temperto在SIAM J. on Scientific Computing 写的一篇文章,文章的链接为: 【链接】http://epubs.siam.org/sisc/resource/1/sjoce3/v13/i3/p676_s1?isAuthorized=no 非常感谢!!2011-8-15 21:16 - rederry - 求助成功区
求助SIAM J. on Control and Optimization 文献
2 个回复 - 1186 次查看 【题 名】: Lipschitz Continuity of Solutions of Linear Inequalities, Programs and Complementarity Problems 【作 者】:O. L. Mangasarian and T.-H. Shiau 【期刊、会议、单位 ...2011-7-29 22:33 - takoupu - 文献求助专区
SIAM英文文献一篇
3 个回复 - 1051 次查看 作者:Wonham W M. 杂志: On a matrix riccati equation of stochastic control. 期刊:SIAM J. Control, 时间、卷号、页码:1968,6(4:)681-697 相关链接:http://epubs.siam.org/sicon/resource/1/sjcodc/v ...2011-3-11 17:04 - apple3631 - 求助成功区
SIAM英文文献一篇
2 个回复 - 1218 次查看 相关链接:http://epubs.siam.org/sisc/resource/1/sjoce3/v2/i4/p474_s1?isAuthorized=no 作者:D. P. O'LEARY AND J. A. SIMMONS 标题:A bidiagonalization-regularization procedure for large scale discret ...2011-2-27 15:22 - apple3631 - 求助成功区
SIAM Review 文献一篇
1 个回复 - 1414 次查看 题 名:Skiving Addition to the Cutting Stock Problem in the Paper Industry 作 者:M. P. Johnson, C. Rennick, and E. Zak 期刊:SIAM Review 年, 卷(期), 起止页码:1997 Volume 39, Issue 3, pp. 383-569 ...2011-2-8 16:31 - jinpenghfut - 求助成功区
如何下SIAM好书
0 个回复 - 1394 次查看 我发现SIAM站点上只能一页一页下,有点**。哪位大侠知道整本书的下载方法? 我计算了一下,差不多下载一页20秒,100页在30分钟左右。已经是很快了。2009-8-26 20:52 - zerana - 经济金融数学专区