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   1389476篇
  免费   29765篇
  国内免费   7734篇
化学   695791篇
晶体学   20936篇
力学   76264篇
综合类   127篇
数学   246749篇
物理学   387108篇
  2021年   13509篇
  2020年   15996篇
  2019年   16103篇
  2018年   15949篇
  2017年   14588篇
  2016年   29342篇
  2015年   21141篇
  2014年   30498篇
  2013年   74487篇
  2012年   40937篇
  2011年   40968篇
  2010年   39909篇
  2009年   41795篇
  2008年   39436篇
  2007年   36177篇
  2006年   38297篇
  2005年   33267篇
  2004年   33019篇
  2003年   30454篇
  2002年   30796篇
  2001年   29777篇
  2000年   25534篇
  1999年   22897篇
  1998年   21192篇
  1997年   21091篇
  1996年   21186篇
  1995年   19186篇
  1994年   18649篇
  1993年   18196篇
  1992年   18232篇
  1991年   18503篇
  1990年   17710篇
  1989年   17776篇
  1988年   17397篇
  1987年   17305篇
  1986年   16218篇
  1985年   22620篇
  1984年   23870篇
  1983年   20061篇
  1982年   21661篇
  1981年   20901篇
  1980年   20225篇
  1979年   20468篇
  1978年   21759篇
  1977年   21366篇
  1976年   21062篇
  1975年   19777篇
  1974年   19437篇
  1973年   19906篇
  1972年   14395篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Differential Equations - Galathea traps for confining plasma in a magnetic field created by current-carrying conductors immersed in the plasma volume constitute a promising class of objects for...  相似文献   
122.
Ferrarini  A.  Finotello  A.  Salsano  G.  Auricchio  F.  Palombo  D.  Spinella  G.  Pane  B.  Conti  M. 《Acta Mechanica Sinica》2021,37(7):1192-1192
Acta Mechanica Sinica - A Correction to this paper has been published: https://doi.org/10.1007/s10409-021-01066-2  相似文献   
123.
Physics of the Solid State - The interference of excited and received by current antennae magnetoelastic waves counterpropagating in an yttrium iron garnet film is experimentally studied. It is...  相似文献   
124.
Journal of Experimental and Theoretical Physics - The studies of the topological properties of systems have recently been extended due to a new concept of higher-order topological insulators and...  相似文献   
125.
Physics of Atomic Nuclei - Emission of short electron bunches with high charge in RF guns is considered. The emission mechanism in the case of picosecond laser pulses and the presence of a strong...  相似文献   
126.
Li  Y.  Shi  W. H.  Dong  L. M.  Xu  S. X.  Huang  H. J.  Yin  J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,...  相似文献   
127.
BPh3 catalyzes the N-methylation of secondary amines and the C-methylenation (methylene-bridge formation between aromatic rings) of N,N-dimethylanilines or 1-methylindoles in the presence of CO2 and PhSiH3; these reactions proceed at 30–40 °C under solvent-free conditions. In contrast, B(C6F5)3 shows little or no activity. 11B NMR spectra suggested the generation of [HBPh3]. The detailed mechanism of the BPh3-catalyzed N-methylation of N-methylaniline ( 1 ) with CO2 and PhSiH3 was studied by using DFT calculations. BPh3 promotes the conversion of two substrates (N-methylaniline and CO2) into a zwitterionic carbamate to give three-component species [Ph(Me)(H)N+CO2⋅⋅⋅BPh3]. The carbamate and BPh3 act as the nucleophile and Lewis acid, respectively, for the activation of PhSiH3 to generate [HBPh3], which is used to produce key CO2-derived species, such as silyl formate and bis(silyl)acetal, essential for the N-methylation of 1 . DFT calculations also suggested other mechanisms involving water for the generation of [HBPh3] species.  相似文献   
128.
Solar-driven interfacial vaporization by localizing solar-thermal energy conversion to the air−water interface has attracted tremendous attention. In the process of converting solar energy into heat energy, photothermal materials play an essential role. Herein, a flexible solar-thermal material di-cyan substituted 5,12-dibutylquinacridone (DCN−4CQA)@Paper was developed by coating photothermal quinacridone derivatives on the cellulose paper. The DCN−4CQA@Paper combines desired chemical and physical properties, broadband light-absorbing, and shape-conforming abilities that render efficient photothermic vaporization. Notably, synergetic coupling of solar-steam and solar-electricity technologies by integrating DCN−4CQA@Paper and the thermoelectric devices is realized without trade-offs, highlighting the practical consideration toward more impactful solar heat exploitation. Such solar distillation and low-grade heat-to-electricity generation functions can provide potential opportunities for fresh water and electricity supply in off-grid or remote areas.  相似文献   
129.
Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown...  相似文献   
130.
Doklady Mathematics - Two classes of Taylor-type formulas for arbitrary continuous functions on intervals are obtained using Bernstein polynomials. These formulas are applicable to both smooth...  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