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   88227篇
  免费   909篇
  国内免费   417篇
化学   31616篇
晶体学   831篇
力学   6876篇
数学   33385篇
物理学   16845篇
  2023年   79篇
  2022年   66篇
  2021年   162篇
  2020年   246篇
  2019年   214篇
  2018年   10535篇
  2017年   10347篇
  2016年   6471篇
  2015年   1222篇
  2014年   714篇
  2013年   823篇
  2012年   4456篇
  2011年   11145篇
  2010年   6127篇
  2009年   6443篇
  2008年   7228篇
  2007年   9286篇
  2006年   774篇
  2005年   1859篇
  2004年   2011篇
  2003年   2309篇
  2002年   1334篇
  2001年   441篇
  2000年   447篇
  1999年   328篇
  1998年   318篇
  1997年   322篇
  1996年   337篇
  1995年   233篇
  1994年   187篇
  1993年   203篇
  1992年   146篇
  1991年   143篇
  1990年   94篇
  1989年   156篇
  1988年   127篇
  1987年   108篇
  1986年   110篇
  1985年   111篇
  1984年   101篇
  1983年   70篇
  1982年   107篇
  1981年   91篇
  1980年   84篇
  1979年   85篇
  1978年   76篇
  1977年   58篇
  1976年   47篇
  1975年   46篇
  1973年   53篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
2.
3.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
4.
5.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  相似文献   
6.
7.
Despite the development of targeted therapies in cancer, the problem of multidrug resistance (MDR) is still unsolved. Most patients with metastatic cancer die from MDR. Transmembrane efflux pumps as the main cause of MDR have been addressed by developed inhibitors, but early inhibitors of the most prominent and longest known efflux pump P-glycoprotein (P-gp) were disappointing. Those inhibitors have been used without knowledge about the expression of P-gp by the treated tumor. Therefore the use of inhibitors of transmembrane efflux pumps in clinical settings is reconsidered as a promising strategy in the case of the respective efflux pump expression. We discovered novel symmetric inhibitors of the symmetric efflux pump MRP4 encoded by the ABCC4 gene. MRP4 is involved in many kinds of cancer with resistance to anticancer drugs. All compounds showed better activities than the best known MRP4 inhibitor MK571 in an MRP4-overexpressing cell line assay, and the activities could be related to the various substitution patterns of aromatic residues within the symmetric molecular framework. One of the best compounds was demonstrated to overcome the MRP4-mediated resistance in the cell line model to restore the anticancer drug sensitivity as a proof of concept.  相似文献   
8.
9.
10.
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