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   194891篇
  免费   1674篇
  国内免费   681篇
化学   104377篇
晶体学   3016篇
力学   7919篇
综合类   1篇
数学   21668篇
物理学   60265篇
  2020年   1589篇
  2019年   1845篇
  2018年   1999篇
  2017年   1889篇
  2016年   3112篇
  2015年   2062篇
  2014年   3132篇
  2013年   8924篇
  2012年   6439篇
  2011年   7998篇
  2010年   5249篇
  2009年   5141篇
  2008年   7148篇
  2007年   7340篇
  2006年   6625篇
  2005年   6264篇
  2004年   5608篇
  2003年   4913篇
  2002年   4917篇
  2001年   5755篇
  2000年   4267篇
  1999年   3366篇
  1998年   2820篇
  1997年   2854篇
  1996年   2614篇
  1995年   2544篇
  1994年   2359篇
  1993年   2378篇
  1992年   2594篇
  1991年   2615篇
  1990年   2517篇
  1989年   2477篇
  1988年   2489篇
  1987年   2410篇
  1986年   2326篇
  1985年   3134篇
  1984年   3322篇
  1983年   2693篇
  1982年   2995篇
  1981年   2909篇
  1980年   2855篇
  1979年   2856篇
  1978年   3019篇
  1977年   2839篇
  1976年   3074篇
  1975年   2705篇
  1974年   2877篇
  1973年   3096篇
  1972年   1852篇
  1971年   1412篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Intricate behaviour of one-electron potentials from the Euler equation for electron density and corresponding gradient force fields in crystals was studied. Channels of locally enhanced kinetic potential and corresponding saddle Lagrange points were found between chemically bonded atoms. Superposition of electrostatic and kinetic potentials and electron density allowed partitioning any molecules and crystals into atomic - and potential-based -basins; -basins explicitly account for the electron exchange effect, which is missed for -ones. Phenomena of interatomic charge transfer and related electron exchange were explained in terms of space gaps between zero-flux surfaces of - and -basins. The gap between - and -basins represents the charge transfer, while the gap between - and -basins is a real-space manifestation of sharing the transferred electrons caused by the static exchange and kinetic effects as a response against the electron transfer. The regularity describing relative positions of -, -, and - basin boundaries between interacting atoms was proposed. The position of -boundary between - and -ones within an electron occupier atom determines the extent of transferred electron sharing. The stronger an H⋅⋅⋅O hydrogen bond is, the deeper hydrogen atom's -basin penetrates oxygen atom's -basin, while for covalent bonds a -boundary closely approaches a -one indicating almost complete sharing of the transferred electrons. In the case of ionic bonds, the same region corresponds to electron pairing within the -basin of an electron occupier atom.  相似文献   
3.
The formation of transition metal (M) carbides MxCy and trends of their stability are systematically investigated using the USPEX code within the DFT.  相似文献   
4.
On the Statistical Calibration of Physical Models   总被引:1,自引:0,他引:1       下载免费PDF全文
We introduce a novel statistical calibration framework for physical models, relying on probabilistic embedding of model discrepancy error within the model. For clarity of illustration, we take the measurement errors out of consideration, calibrating a chemical model of interest with respect to a more detailed model, considered as “truth” for the present purpose. We employ Bayesian statistical methods for such model‐to‐model calibration and demonstrate their capabilities on simple synthetic models, leading to a well‐defined parameter estimation problem that employs approximate Bayesian computation. The method is then demonstrated on two case studies for calibration of kinetic rate parameters for methane air chemistry, where ignition time information from a detailed elementary‐step kinetic model is used to estimate rate coefficients of a simple chemical mechanism. We show that the calibrated model predictions fit the data and that uncertainty in these predictions is consistent in a mean‐square sense with the discrepancy from the detailed model data.  相似文献   
5.
6.
7.
8.
9.
The quantitative characteristics of the temperature effect on the rheological properties of aqueous solutions of the anionic surfactant sodium methyl oleyl taurate (SMOT) are presented. An increase in the intensity of thermal motion of surfactant molecules on heating from 25 to 45 °С was shown to decrease the average contour length of SMOT micelles from 2 μm to 700 nm. The decrease in the length of cylindrical micelles is probably one of the main reasons for a substantial decrease in the viscosity of micellar solutions of the surfactant with temperature.  相似文献   
10.
Russian Chemical Bulletin - 2,2-Bis[4-(4-nitroaryl)phenyl]hexafluoropropanes appropriate for the synthesis of monomers were prepared by the reaction of 2,2-bis[4-hydroxyphenyl)hexafluoropropane...  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