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   7179篇
  免费   266篇
  国内免费   39篇
化学   4326篇
晶体学   39篇
力学   239篇
数学   1406篇
物理学   1474篇
  2023年   61篇
  2022年   57篇
  2021年   198篇
  2020年   177篇
  2019年   166篇
  2018年   143篇
  2017年   128篇
  2016年   276篇
  2015年   261篇
  2014年   269篇
  2013年   399篇
  2012年   476篇
  2011年   538篇
  2010年   323篇
  2009年   299篇
  2008年   448篇
  2007年   403篇
  2006年   379篇
  2005年   367篇
  2004年   291篇
  2003年   226篇
  2002年   223篇
  2001年   114篇
  2000年   85篇
  1999年   86篇
  1998年   78篇
  1997年   87篇
  1996年   61篇
  1995年   66篇
  1994年   65篇
  1993年   52篇
  1992年   38篇
  1991年   35篇
  1990年   34篇
  1989年   23篇
  1988年   30篇
  1987年   29篇
  1986年   30篇
  1985年   47篇
  1984年   52篇
  1983年   25篇
  1982年   38篇
  1981年   25篇
  1980年   31篇
  1979年   30篇
  1978年   26篇
  1977年   25篇
  1976年   21篇
  1973年   19篇
  1972年   13篇
排序方式: 共有7484条查询结果,搜索用时 296 毫秒
11.
For ϕ a δ-subharmonic function, sharp results are obtained that connectA(r, ϕ), B(r, ϕ) andT(r, ϕ), whereA(r, ϕ)=inf|z|=r ϕ(z),B(r, ϕ)=sup|z|=r ϕ(z), andT(r, ϕ) is the Nevanlinna characteristics.  相似文献   
12.
13.
Some stability results for Mountain Pass and Linking type solutions of semilinear problems involving a very general class of Dirichlet forms are stated. The non linear terms are supposed to have a suitable superlinear growth and the family of Dirichlet forms is required to be dominated from below and from above by a fixed diffusion type form. Some concrete examples are also given.  相似文献   
14.
15.
By combining frontal polymerization and radical‐induced cationic polymerization, it was possible to cure thick samples of an epoxy monomer bleached by UV light. The effect of the relative amounts of cationic photoinitiator and radical initiator was thoroughly investigated and was related to the front's velocity and its maximum temperature. The materials obtained were characterized by quantitative conversion also in the deeper layers, not reached by UV light. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2066–2072, 2004  相似文献   
16.
17.
Some nickel, copper, and silver salts or complexes are efficient catalysts for the oxidation of benzylic ethers with oxygen in 1,2-dimethoxyethane. Salts of the weakly coordinating anion trifluoroacetate are particularly efficient, approaching (and, in some cases, improving) the yields obtained with cobalt(II) chloride, the best catalyst so far reported.  相似文献   
18.
Photoinitiated cationic polymerization of mono‐ and bifunctional epoxy monomers, namely cyclohexeneoxide (CHO), 4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexanecarboxylate (EEC), respectively by using sulphonium salts in the presence of hydroxylbutyl vinyl ether (HBVE) was studied. The real‐time FTIR spectroscopic, gel content determination, and thermal characterization studies revealed that both hydroxyl and vinyl ether functionalities of HBVE take part in the polymerization. During the polymerization, HBVE has the ability to react via both active chain end (ACE) and activated monomer mechanisms through its hydroxyl and vinyl ether functionalities, respectively. Thus, more efficient curing was observed with the addition of HBVE into EEC‐containing formulations. It was also demonstrated that HBVE is effective in facilitating the photoinduced crosslinking of monofunctional epoxy monomer, CHO in the absence of a conventional crosslinker. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4914–4920, 2007  相似文献   
19.
It is routine to demonstrate in the exchange economy framework that small changes of individual preferences and endowments always result in small changes of the derived excess demand functions as one should expect. Though being as desirable for reasons of the consistency of the whole approach, however, a precise proof of the converse direction so far is still open to question. The present paper shows that it is actually true. We use a decomposition method for aggregate excess demand functions developed by Mas-Colell which is derived from the well-known decomposition method developed by Sonnenschein and perfected by Debreu and Mantel. Our result fills in a notorious gap in the line of economic justification usually given for this decomposition, or disaggregation, method in that comparative static analysis would be restricted if the decomposition of excess demand functions would not be continuous.  相似文献   
20.
Bulk carbon impurities segregate at the Fe(1 0 0) surface and, upon thermal annealing, can form metastable surface phases with local and long range order and peculiar electronic properties. We present a surface science study of C-segregated Fe(1 0 0) with scanning tunneling microscopy, angle resolved photoemission, and ab initio calculations of the surface structure and electron states. In particular the c(3√2 × √2) structure, observed for 0.67 atomic layers of C segregated at the iron surface, is found to be due to self-organized carbon stripes made of zig-zag chains. The strong hybridization between C and Fe was observed in ARPES spectra.  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