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   504394篇
  免费   4099篇
  国内免费   1159篇
化学   248684篇
晶体学   7639篇
力学   25823篇
综合类   5篇
数学   66838篇
物理学   160663篇
  2020年   4724篇
  2019年   5695篇
  2018年   7935篇
  2017年   8085篇
  2016年   10842篇
  2015年   5667篇
  2014年   9897篇
  2013年   21659篇
  2012年   16751篇
  2011年   20111篇
  2010年   15334篇
  2009年   15382篇
  2008年   18828篇
  2007年   18741篇
  2006年   17007篇
  2005年   15183篇
  2004年   14225篇
  2003年   12988篇
  2002年   13107篇
  2001年   13739篇
  2000年   10703篇
  1999年   8122篇
  1998年   7306篇
  1997年   7208篇
  1996年   6612篇
  1995年   6031篇
  1994年   5986篇
  1993年   6017篇
  1992年   6301篇
  1991年   6670篇
  1990年   6518篇
  1989年   6475篇
  1988年   6296篇
  1987年   6261篇
  1986年   5858篇
  1985年   7422篇
  1984年   7767篇
  1983年   6532篇
  1982年   7034篇
  1981年   6611篇
  1980年   6294篇
  1979年   6815篇
  1978年   7090篇
  1977年   7065篇
  1976年   7367篇
  1975年   6676篇
  1974年   6702篇
  1973年   7120篇
  1972年   5249篇
  1971年   4445篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Low-flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for MS have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow LC, the types of columns employed, and strategies for multidimensionality of separations, which are key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend toward biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy-to-use platform.  相似文献   
22.

A kinetic study of the effect of thermoheliox (inhalation of a helium and oxygen mixture, 70 °C) on the functional hemodynamics of the human brain by functional magnetic resonance imaging was carried out. The dynamic responses of the BOLD signal were found to be biphasic. An empirical equation describing the first phase of the hemodynamic response to visual stimulus was proposed. It was shown that preliminary inhalation of thermoheliox stimulates the hemodynamic responses by slowing down the vasoconstriction.

  相似文献   
23.
Siberian Mathematical Journal - Let $ \{(A_{i},B_{i})\}_{i=1}^{m} $ be a set pair system. Füredi, Gyárfás, and Király called it $ 1 $ -cross intersecting if $...  相似文献   
24.
Journal of Applied Mechanics and Technical Physics - Implicit finite-volume predictor-corrector algorithms based on the splitting method are proposed for the numerical solution of the...  相似文献   
25.
Acta Mathematica Hungarica - Minkowski’s classical existence theorem provides necessary and sufficient conditions for a Borel measure on the unit sphere of Euclidean space to be the surface...  相似文献   
26.
Siberian Mathematical Journal - Suppose that $ n $ is an integer, $ n\geq 3 $ . We prove that a periodic group saturated with a set of the finite simple groups $ O_{2n+1}(q) $ , where $ q $ is...  相似文献   
27.
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation.  相似文献   
28.
Physics of Atomic Nuclei - The muon puzzle is an excess of muon bundles generated by primary cosmic rays (PCR) at energies above 10 $${}^{17}$$ eV compared to estimations that assume even a heavy...  相似文献   
29.
Algebra and Logic - Unary functions definable in o-stable ordered groups of nonvaluational type are studied. Such functions are proved to be piecewise monotone and continuous.  相似文献   
30.
Kumar  Sanjay  Jiwari  Ram  Mittal  R. C.  Awrejcewicz  Jan 《Nonlinear dynamics》2021,104(1):661-682
Nonlinear Dynamics - In this article, the authors simulate and study dark and bright soliton solutions of 1D and 2D regularized long wave (RLW) models. The RLW model occurred in various fields such...  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