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   61522篇
  免费   964篇
  国内免费   304篇
化学   29296篇
晶体学   917篇
力学   3264篇
综合类   8篇
数学   4814篇
物理学   24491篇
  2022年   429篇
  2021年   493篇
  2020年   481篇
  2019年   464篇
  2018年   601篇
  2017年   525篇
  2016年   958篇
  2015年   696篇
  2014年   1067篇
  2013年   2668篇
  2012年   2527篇
  2011年   3246篇
  2010年   2238篇
  2009年   2273篇
  2008年   2929篇
  2007年   2769篇
  2006年   2653篇
  2005年   2353篇
  2004年   2159篇
  2003年   1913篇
  2002年   1721篇
  2001年   3040篇
  2000年   2138篇
  1999年   1518篇
  1998年   1055篇
  1997年   1033篇
  1996年   849篇
  1995年   800篇
  1994年   735篇
  1993年   648篇
  1992年   980篇
  1991年   955篇
  1990年   864篇
  1989年   773篇
  1988年   750篇
  1987年   822篇
  1986年   672篇
  1985年   937篇
  1984年   879篇
  1983年   577篇
  1982年   591篇
  1981年   560篇
  1980年   528篇
  1979年   672篇
  1978年   676篇
  1977年   704篇
  1976年   616篇
  1975年   507篇
  1974年   538篇
  1973年   465篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Hanif  Y.  Sarfraz  H.  Saleem  U. 《Nonlinear dynamics》2020,100(2):1559-1569
Nonlinear Dynamics - In this article, we present a system of coupled short pulse equations as integrability condition of associated generalized linear eigenvalue problem. We obtain system of...  相似文献   
42.
Optics and Spectroscopy - Endometriosis is a benign gynecologic disorder. It is particularly common among young women and may make pregnancy difficult. In this study molecular level...  相似文献   
43.
Two new octahedral [Ni(phen)2(dppz-idzo)]2+ and [Co(phen)2(dppz-idzo)]3+ complexes have been synthesized and characterized by CHN analysis, electrospray ionization-MS, nuclear magnetic resonance, and UV–Vis spectra. The DNA-binding ability of these complexes was spectrophotometrically, hydrodynamically, and electrophoretically evaluated which indicated that they strongly intercalate into the DNA double helix, and that both induced severe DNA damage in the presence of peroxide. The complexes also showed strong antiproliferative effect against HepG2 and MDA-MB-231 cells. By contrast, they were found to be inactive against the MCF-7 cell line. The ligand itself was found to be inactive against the cells tested.  相似文献   
44.
Li  C.  Zhang  D.  Cheng  G.  Zhu  Y. 《Experimental Mechanics》2020,60(3):329-343
Experimental Mechanics - There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices....  相似文献   
45.
Yang  Y.  Wan  Z.-Q.  Zhang  J.  Jiang  H.-J.  Zhang  Z.-Q.  Ju  Y.-C. 《Crystallography Reports》2020,65(1):78-83
Crystallography Reports - The {[Sm2(FDC)2](FDC) · 10H2O}n complex, where H2FDC is a 2,5-furandicarboxylic acid, has been prepared by hydrothermal reaction and structurally characterized by...  相似文献   
46.
At DIII-D, a slot divertor concept, called small-angle-slot (SAS), is under development, aiming to enable detachment at relatively low plasma edge density. We report on simulations using the SOLPS-ITER two-dimensional edge code to examine the performance of conceptual “SAS 2” slot configurations. The focus of the analysis is on E  ×  B drift effects on upstream density at detachment (UDD), with detachment marked by electron temperature Te ≤ 3 eV at the outer strike point (OSP). With toroidal field such that radial E  ×  B drift carries particles from the OSP towards the private flux region (PFR), placing the OSP near the inner slot wall gives ≈20% lower UDD than having the OSP near the outer wall. The inner wall effectively traps the radial E  ×  B drift flux, resulting in low Te and associated radial electric field in the PFR, and thus small losses from the slot to the inner target via poloidal E  ×  B drift flux. With toroidal field reversed such that radial E  ×  B drift is reversed, OSP placement near the inner wall gives ≈10% lower UDD than OSP placement near the outer wall. Although radial E  ×  B flux is from the OSP towards the outer wall, this flux largely escapes the slot, raising the UDD. A change in the slot shaping is suggested with the goal of eliminating such E  ×  B -driven particle losses from the slot.  相似文献   
47.
Li  H.  Liang  X.L.  Wang  W.Y.  Xu  Z.  Wen  B.C. 《Experimental Mechanics》2020,60(7):949-967
Experimental Mechanics - Background: Experimental modelling techniques are still rare for composite structures under complex thermal environments. Objective: In this paper, by taking a...  相似文献   
48.
A disulfide intercalator toolbox was developed for site‐specific attachment of a broad variety of functional groups to proteins or peptides under mild, physiological conditions. The peptide hormone somatostatin (SST) served as model compound for intercalation into the available disulfide functionalization schemes starting from the intercalator or the reactive SST precursor before or after bioconjugation. A tetrazole–SST derivative was obtained that undergoes photoinduced cycloaddition in mammalian cells, which was monitored by live‐cell imaging.  相似文献   
49.
50.
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