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   360363篇
  免费   3968篇
  国内免费   1197篇
化学   195914篇
晶体学   4950篇
力学   15075篇
综合类   5篇
数学   39116篇
物理学   110468篇
  2020年   2749篇
  2019年   3082篇
  2018年   3854篇
  2017年   3829篇
  2016年   5946篇
  2015年   3901篇
  2014年   5870篇
  2013年   16142篇
  2012年   12004篇
  2011年   14764篇
  2010年   10024篇
  2009年   9947篇
  2008年   13593篇
  2007年   13472篇
  2006年   12694篇
  2005年   11721篇
  2004年   10531篇
  2003年   9502篇
  2002年   9298篇
  2001年   11527篇
  2000年   8542篇
  1999年   6736篇
  1998年   5241篇
  1997年   5353篇
  1996年   4976篇
  1995年   4647篇
  1994年   4523篇
  1993年   4398篇
  1992年   5117篇
  1991年   5224篇
  1990年   4922篇
  1989年   4854篇
  1988年   4771篇
  1987年   4670篇
  1986年   4429篇
  1985年   5912篇
  1984年   6045篇
  1983年   4937篇
  1982年   5226篇
  1981年   5008篇
  1980年   4838篇
  1979年   5158篇
  1978年   5449篇
  1977年   5288篇
  1976年   5398篇
  1975年   4896篇
  1974年   4979篇
  1973年   5297篇
  1972年   3336篇
  1971年   2595篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Journal of Structural Chemistry - Atomic and electronic structures of cyclic organosilicon compound 9,9,10,10-tetraethynyl-9,10-dihydrodisilaanthracene are studied by the density functional theory....  相似文献   
12.
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial...  相似文献   
13.
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   
14.

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   
15.
Nikazad  T.  Karimpour  M. 《Numerical Algorithms》2021,86(3):1265-1284
Numerical Algorithms - This paper considers different versions of block-column iterative (BCI) methods for solving nonnegative constrained linear least squares problems. We present the convergence...  相似文献   
16.
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   
17.
Optics and Spectroscopy - The current–voltage characteristics and photocurrent of “monolithic” diode optical pairs optically coupled by a substrate made of InAs common for them...  相似文献   
18.
Theoretical and Mathematical Physics - We consider three one-dimensional superconducting structures: 1) the one with $$p$$ -wave superconductivity; 2) the main experimental model of a nanowire with...  相似文献   
19.
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   
20.
Journal of Applied Spectroscopy - Detailed measurements of nonlinear optical properties and optical limiting for four phthalocyanine (Pc) derivatives (PcCo, PcCu, PcMn, and PcSi) are reported. The...  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