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   414033篇
  免费   4463篇
  国内免费   2070篇
化学   218694篇
晶体学   6586篇
力学   18261篇
综合类   61篇
数学   47683篇
物理学   129281篇
  2020年   3284篇
  2019年   3619篇
  2018年   4778篇
  2017年   4734篇
  2016年   6952篇
  2015年   4472篇
  2014年   6890篇
  2013年   17578篇
  2012年   13885篇
  2011年   17127篇
  2010年   12104篇
  2009年   11957篇
  2008年   15867篇
  2007年   15997篇
  2006年   15110篇
  2005年   13729篇
  2004年   12476篇
  2003年   11006篇
  2002年   10939篇
  2001年   12284篇
  2000年   9389篇
  1999年   7123篇
  1998年   6035篇
  1997年   5925篇
  1996年   5777篇
  1995年   5160篇
  1994年   5182篇
  1993年   5134篇
  1992年   5466篇
  1991年   5633篇
  1990年   5283篇
  1989年   5154篇
  1988年   5114篇
  1987年   4974篇
  1986年   4820篇
  1985年   6503篇
  1984年   6704篇
  1983年   5581篇
  1982年   5891篇
  1981年   5685篇
  1980年   5310篇
  1979年   5647篇
  1978年   5893篇
  1977年   5847篇
  1976年   5912篇
  1975年   5410篇
  1974年   5569篇
  1973年   5630篇
  1972年   4165篇
  1971年   3397篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Preface     
Journal of Statistical Physics -  相似文献   
142.
143.
    
  相似文献   
144.
145.
146.
The kinetics of formation of an anomalous phase from a solution with a small 3He impurity was studied in the temperature range 0.2–0.7 K up to a supersaturation of ~30 mbar. The phase diagram was determined for normal and anomalous growths. It is found that, in the presence of impurities, the formation of a fast-growing state is retarded. This experimental fact indicates that the dissipative processes in fluids have an appreciable effect on the phase formation kinetics. The retardation is, possibly, caused by the direct interaction of an impurity with the crystal surface.  相似文献   
147.
We construct an integral Newton-type interpolation polynomial with a continual set of nodes. This interpolant is unique and preserves an operator polynomial of the corresponding degree.  相似文献   
148.
The ring‐opening polymerization of ε‐caprolactone (ε‐CL), initiated by carboxylic acids such as benzoic acid and chlorinated acetic acids under microwave irradiation, was investigated; with this method, no metal catalyst was necessary. The product was characterized as poly(ε‐caprolactone) (PCL) by 1H NMR spectroscopy, Fourier transform infrared spectroscopy, ultraviolet spectroscopy, and gel permeation chromatography. The polymerization was significantly improved under microwave irradiation. The weight‐average molecular weight (Mw) of PCL reached 44,800 g/mol, with a polydispersity index [weight‐average molecular weight/number‐average molecular weight (Mw/Mn)] of 1.6, when a mixture of ε‐CL and benzoic acid (25/1 molar ratio) was irradiated at 680 W for 240 min, whereas PCL with Mw = 12,100 and Mw/Mn = 4.2 was obtained from the same mixture by a conventional heating method at 210 °C for 240 min. A degradation of the resultant PCL was observed during microwave polymerization with chlorinated acetic acids as initiators, and this induced a decrease in Mw of PCL. However, the degradation was hindered by benzoic acid at low concentrations. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 13–21, 2003  相似文献   
149.
A study of the atmospheric pollution by suspended particulate lead in the city of Seville, Spain, was carried out during the period between March 1983 and February 1984. The results obtained from seven sampling stations allowed us to study the site to site variations; there are two locations with average annual concentrations higher than 2 micrograms X m-3. In one station, the meteorological and traffic effects and relationship with other traffic-related pollutants, were investigated. The regression analyses performed on the average monthly data have shown an inverse correlation with wind speed and temperature and a direct correlation with carbon monoxide and smoke concentrations, but no significant correlation was found with the lead deposition levels.  相似文献   
150.
Let F be a non-arithmetic distribution on the line , and W be the class of bounded functions w without discontinuity of the second kind such that
.In this paper, we show that the solution of the homogeneous renewal equation w = w F in the class W is a constant-function.  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