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   1961篇
  免费   88篇
  国内免费   5篇
化学   1397篇
晶体学   1篇
力学   27篇
数学   400篇
物理学   229篇
  2023年   13篇
  2022年   11篇
  2021年   32篇
  2020年   32篇
  2019年   47篇
  2018年   24篇
  2017年   19篇
  2016年   59篇
  2015年   58篇
  2014年   55篇
  2013年   68篇
  2012年   115篇
  2011年   145篇
  2010年   73篇
  2009年   57篇
  2008年   81篇
  2007年   88篇
  2006年   112篇
  2005年   103篇
  2004年   65篇
  2003年   68篇
  2002年   67篇
  2001年   50篇
  2000年   48篇
  1999年   48篇
  1998年   45篇
  1997年   42篇
  1996年   39篇
  1995年   41篇
  1994年   35篇
  1993年   28篇
  1992年   40篇
  1991年   32篇
  1990年   25篇
  1989年   16篇
  1988年   14篇
  1986年   7篇
  1985年   7篇
  1984年   9篇
  1983年   14篇
  1982年   8篇
  1981年   6篇
  1979年   9篇
  1976年   9篇
  1975年   7篇
  1974年   8篇
  1973年   10篇
  1971年   5篇
  1969年   6篇
  1967年   6篇
排序方式: 共有2054条查询结果,搜索用时 31 毫秒
1.
Computational Optimization and Applications - We develop a globalized Proximal Newton method for composite and possibly non-convex minimization problems in Hilbert spaces. Additionally, we impose...  相似文献   
2.
3.
We consider normal ≡ Gaussian seemingly unrelated regressions (SUR) with incomplete data (ID). Imposing a natural minimal set of conditional independence constraints, we find a restricted SUR/ID model whose likelihood function and parameter space factor into the product of the likelihood functions and the parameter spaces of standard complete data multivariate analysis of variance models. Hence, the restricted model has a unimodal likelihood and permits explicit likelihood inference. In the development of our methodology, we review and extend existing results for complete data SUR models and the multivariate ID problem.  相似文献   
4.
Summary Conventional electron ionization (EI) mass spectrometry (MS) and MS/MS techniques were applied to the analysis of two abundant octa and nonachlorobornanes isolated from seals of the Baltic sea and originating from technical toxaphene. The exact sterical structures of the two compounds were previously determined using nuclear magnetic resonance (NMR) spectroscopy by two independent research groups. The MS and MS/MS data generated in this study allowed partial structure elucidation of these polychlorobornanes, in particular revealing the distribution of the Cl substituents between the six-membered carbon ring, the bridge and the bridgehead in the parent bornane structure. Fragmentation of the six-membered carbon ring and the bridge by retro-Diels-Alder (RDA) and related mechanisms was discovered by studying specific parent/daughter ion transitions. The detailed fragmentation pathways formulated may be applicable to the structure elucidation of other toxaphene congeners and the monitoring of strategic transitions is highly selective for the detection of these compounds in technical toxaphene and in environmental samples.  相似文献   
5.
From Kostant’s multiplicity formula for general linear groups, one can derive a formula for the Kostka numbers. In this note we give a combinatorial proof of this formula. Received January 7, 2005  相似文献   
6.
In this paper, we report on the synthesis and detailed characterization of a new semiflexible nematic liquid crystalline polyester which could serve as a 'model' polyester for a variety of physical and physico-chemical investigations. The polymer is a nematic liquid over a wide temperature range-from the glass transition temperature at ∼95°C to the isotropic transition at ∼240°C. We expect this polyester to be particularly useful for studying the effect of flow on the orientation of liquid crystalline polymers, as well as the production and removal of disclinations.  相似文献   
7.
8.
9.
10.
Investigations of the electronic and magnetic properties of oxygen adsorbed on magnetized iron films have been carried out by means of angle and spin resolving photoelectron spectroscopy. Iron, epitaxially grown on W(100) and W(110) crystals, served as the ferromagnetic substrate. Exchange splittings of the O 2px derived level have been detected, demonstrating a magnetic coupling between the chemisorbate and the iron layer. Variations of the exchange splitting have occurred as a function of the oxygen coverage, photon energy, and emission angle. High oxygen exposures have lead to a FeO overlayer at the surface.  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