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   1323137篇
  免费   29821篇
  国内免费   7839篇
化学   658513篇
晶体学   16129篇
力学   74635篇
综合类   109篇
数学   241995篇
物理学   369416篇
  2021年   13454篇
  2020年   15982篇
  2019年   16107篇
  2018年   12843篇
  2016年   27988篇
  2015年   20888篇
  2014年   30530篇
  2013年   74615篇
  2012年   37638篇
  2011年   34486篇
  2010年   37152篇
  2009年   39598篇
  2008年   33864篇
  2007年   29630篇
  2006年   35391篇
  2005年   28242篇
  2004年   29354篇
  2003年   27750篇
  2002年   28874篇
  2001年   27791篇
  2000年   24453篇
  1999年   22361篇
  1998年   21023篇
  1997年   21065篇
  1996年   21114篇
  1995年   19196篇
  1994年   18658篇
  1993年   18204篇
  1992年   18032篇
  1991年   18358篇
  1990年   17508篇
  1989年   16973篇
  1988年   16557篇
  1987年   16577篇
  1986年   15444篇
  1985年   22006篇
  1984年   23371篇
  1983年   19473篇
  1982年   21241篇
  1981年   20466篇
  1980年   19803篇
  1979年   20019篇
  1978年   21388篇
  1977年   21005篇
  1976年   20760篇
  1975年   19436篇
  1974年   19081篇
  1973年   19588篇
  1972年   14111篇
  1967年   12541篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
121.
Doklady Mathematics - The integrability of certain classes of homogeneous dynamical systems on the tangent bundles of four-dimensional manifolds is shown. The force fields involved in the systems...  相似文献   
122.
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   
123.
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   
124.
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   
125.
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   
126.
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   
127.
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   
128.
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   
129.
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   
130.
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   
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