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   8222篇
  免费   249篇
  国内免费   45篇
化学   5299篇
晶体学   52篇
力学   250篇
数学   1458篇
物理学   1457篇
  2023年   45篇
  2022年   110篇
  2021年   133篇
  2020年   137篇
  2019年   153篇
  2018年   154篇
  2017年   147篇
  2016年   244篇
  2015年   251篇
  2014年   246篇
  2013年   505篇
  2012年   573篇
  2011年   610篇
  2010年   366篇
  2009年   319篇
  2008年   468篇
  2007年   448篇
  2006年   420篇
  2005年   399篇
  2004年   344篇
  2003年   298篇
  2002年   239篇
  2001年   137篇
  2000年   121篇
  1999年   92篇
  1998年   74篇
  1997年   64篇
  1996年   70篇
  1995年   53篇
  1994年   65篇
  1993年   47篇
  1992年   50篇
  1991年   66篇
  1990年   64篇
  1989年   56篇
  1988年   49篇
  1987年   39篇
  1985年   52篇
  1984年   72篇
  1983年   37篇
  1982年   55篇
  1981年   42篇
  1980年   48篇
  1979年   37篇
  1978年   37篇
  1977年   52篇
  1976年   37篇
  1975年   39篇
  1974年   36篇
  1973年   31篇
排序方式: 共有8516条查询结果,搜索用时 23 毫秒
51.
Abstract

The synthesis of 5-O-[5-(pentanoic acid)]-phosphono-L-erythro-pent-2-ulose 2 was successfully achieved by coupling benzyl 5-hydroxypentanoate 9b and 1-O-benzyl-L-erythro-pent-2-ulose ethane- 1,2-diyl dithioacetal 13 with the enediol pyrophosphate 18. Compound 2 was coupled to carrier proteins, porcine thyroglobuline and bovine serum albumin and the conjugates were treated with KCN to give conjugates of the hapten 1, designed to raise catalytic antibodies.  相似文献   
52.
53.
54.

Abstract  

The non-enzyme-catalyzed reaction of reduced glutathione (GSH) with two tumor cell cytotoxic cyclic chalcone analogues was investigated by reversed-phase high-performance liquid chromatography (RP-HPLC). HPLC analysis of the reaction mixtures indicated the formation of two diastereomeric chalcone–GSH adducts in each case, whose structural assignments were supported by MALDI-TOF-MS and HPLC–MS with electrospray ionization (ESI) measurements. Such reactivity accounts for the previously observed effect of the two cyclic chalcone analogues on the in vivo cellular thiol level of Jurkat T cells.  相似文献   
55.
56.
The random walk of a particle on a directed Bethe lattice of constant coordinanceZ is examined in the case of random hopping rates. As a result, the higher the coordinance, the narrower the regions of anomalous drift and diffusion. The annealed and quenched mean square dispersions are calculated in all dynamical phases. In opposition to the one-dimensional (Z=2) case, the annealed and quenched mean quadratic dispersions are shown to be identical in all phases.We shall employ indifferently the expressions Bethe lattice or infinite Cayley tree to denote an infinite ramified lattice of constant coordinanceZ.(4, 5)  相似文献   
57.
58.
59.
In this work, chemically and topographically nanopatterned surfaces were produced by a top-down processing approach for biosensing devices. The nanopatterning was the result of the combination of plasma polymerisation (pp) of biofunctional materials and colloidal lithography techniques. The morphological and chemical properties induced by the plasma deposition-etching treatment were characterised by optical method combining ellipsometry and Fourier Transform Infrared spectroscopy studies. This method supported by atomic force microscopy measurements, allowed the full optical characterization of each step of the top-down process. The optical characterization of the end-up nanopatterned samples demonstrated that the chosen process is able to produce well-defined nanostructured surfaces with controlled chemical and morphological properties.  相似文献   
60.
The coherent combining of two Nd:YAG lasers using a Vernier–Michelson-type cavity has been demonstrated. The spectral behaviour and the energetic performance are reported. We firstly show that the combining efficiency is not strongly spoilt by the gain imbalance between the two amplifying media, and secondly, that despite the interferometric nature of the cavity, the Vernier–Michelson laser can withstand environmental perturbations without alteration in output power. Received: 25 April 2002 / Revised version: 18 May 2002 / Published online: 25 September 2002 RID="*" ID="*"Corresponding author. Fax: +33-5/5545-7253, E-mail: kermene@ircom.unilim.fr  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