首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   149288篇
  免费   13280篇
  国内免费   7991篇
化学   74835篇
晶体学   1422篇
力学   11140篇
综合类   343篇
数学   39807篇
物理学   43012篇
  2024年   180篇
  2023年   1592篇
  2022年   2347篇
  2021年   2748篇
  2020年   3197篇
  2019年   2979篇
  2018年   12296篇
  2017年   11945篇
  2016年   9252篇
  2015年   4253篇
  2014年   4361篇
  2013年   5679篇
  2012年   10386篇
  2011年   16979篇
  2010年   10035篇
  2009年   10151篇
  2008年   11082篇
  2007年   12703篇
  2006年   4117篇
  2005年   4557篇
  2004年   4051篇
  2003年   3917篇
  2002年   2825篇
  2001年   1809篇
  2000年   1744篇
  1999年   1776篇
  1998年   1561篇
  1997年   1505篇
  1996年   1559篇
  1995年   1215篇
  1994年   1063篇
  1993年   903篇
  1992年   766篇
  1991年   674篇
  1990年   586篇
  1989年   466篇
  1988年   414篇
  1987年   355篇
  1986年   320篇
  1985年   270篇
  1984年   196篇
  1983年   141篇
  1982年   128篇
  1981年   114篇
  1980年   118篇
  1979年   80篇
  1978年   66篇
  1977年   59篇
  1976年   46篇
  1973年   56篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
H-空间与拟向量变分不等式   总被引:2,自引:0,他引:2  
本在Hausdorff locally convex H-空间上建立了一个新的不动点定理;利用局部交性质,在Hausdorff locally convex H-空间上建立了相应的拟向量变分不等式.  相似文献   
982.
Conductivity, viscosity, turbidity, and NMR measurements were performed over most of the mole fraction range for sodium deoxycholate (SDC) with hexadecyltrimethylammonium bromide (HTAB), hexadecylpyridinium bromide (HPyBr), and hexadecylpyridinium chloride (HPyCl). All studies demonstrate that the mixed-micelle formation is more favorable in SDC plus HTAB rather than SDC plus HPyBr or SDC plus HPyCl mixtures. The results showed that the bulky pyridinium head groups of HPyBr or HPyCl create steric incompatibility with rigid SDC monomers in the mixed state.  相似文献   
983.
电磁继电器触点参数的测试   总被引:1,自引:0,他引:1  
本文介绍了电磁继电器触点电参数的测试方法,包括接触电阻、绝缘电阻参数测试。  相似文献   
984.
We define separable sets in algebraic lattices. For a finitely generated congruence distributive variety V \mathcal{V} , we show a close connection between non-separable sets in congruence lattices of algebras in V \mathcal{V} and the structure of subdirectly irreducible algebras in V \mathcal{V} . We apply the general results to some lattice varieties.  相似文献   
985.
986.
Fixed Point Theorems on Product Topological Spaces and Applications   总被引:3,自引:0,他引:3  
A new collectively fixed point theorem for a family of set-valued mappings defined on product spaces of non-compact topological spaces without linear structure is proved and some special cases are also discussed. As applications, some non-empty intersection theorems of sets with convex sections and equilibrium existence theorem of abstract economies are obtained under much weaker assumptions. Our results includes a number of known results as many special cases.  相似文献   
987.
Many food algae and red tide algae were cultivated in the f/2 medium, and the nitric oxide (NO) concentration of the medium and the cell density were determined. The experiments on algae were conducted when different concentrations of NO were added into the medium using two methods. The results show that low concentrations of NO were self-produced by marine algae during the exponential growth period and were about nmol/L level. But at the end of the period, i.e., 2 or 3 days before the cell density reaches the maximum, an NO peak appeared, with the NO concentration reaching 10 nmol/L. The NO threshold concentration exists according to the influence of exogenous NO on the marine phytoplankton growth. One type is the threshold concentration that can promote algae growth, and its value is between 10 and 1 nmol level, or even lower. The other type can inhibit the phytoplankton growth, which is about μmol level or higher. The results indicate that red tide algae are far more sensitive to NO than are food algae. The fundamental experimental outcome above may provide a new clue for red tide chemical forecast by inspecting the NO change.  相似文献   
988.
989.
§1 IntroductionAt present,boundary value problems (BVPs) are widely investigated with variousmethods and techniques. BVPs with integral boundary conditions constitute a veryinteresting class of problems such as multipoint,three-point,four-point and nonlocalboundary value problems which are considered by many authors.And the existence ofpositive solutions for these problems becomes the subjectof many papers[1—6] .In a recentpaper[7] ,the authors have studied the existence of positive solut…  相似文献   
990.
讨论了 C\+n 中有界对称域的加权Bergman空间上符号属于 L\+2\-a(Ω, dV\-λ) 的小Hankel算子, 利用符号 Φ 的某种积分变换,给出了小Hankel算子 h\-Φ 属于Schatten理想 S\-p 的特征.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号