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   528681篇
  免费   4163篇
  国内免费   1283篇
化学   269045篇
晶体学   7686篇
力学   25999篇
综合类   17篇
数学   67791篇
物理学   163589篇
  2021年   5035篇
  2020年   5492篇
  2019年   6221篇
  2018年   8414篇
  2017年   8561篇
  2016年   11625篇
  2015年   6176篇
  2014年   10437篇
  2013年   23485篇
  2012年   18335篇
  2011年   21788篇
  2010年   16419篇
  2009年   16279篇
  2008年   20656篇
  2007年   20508篇
  2006年   18612篇
  2005年   16620篇
  2004年   15468篇
  2003年   13955篇
  2002年   13847篇
  2001年   14725篇
  2000年   11343篇
  1999年   8752篇
  1998年   7600篇
  1997年   7470篇
  1996年   6929篇
  1995年   6257篇
  1994年   6270篇
  1993年   6022篇
  1992年   6377篇
  1991年   6865篇
  1990年   6578篇
  1989年   6486篇
  1988年   6322篇
  1987年   6132篇
  1986年   5871篇
  1985年   7408篇
  1984年   7769篇
  1983年   6532篇
  1982年   6817篇
  1981年   6326篇
  1980年   6003篇
  1979年   6504篇
  1978年   6741篇
  1977年   6629篇
  1976年   6586篇
  1975年   6302篇
  1974年   6129篇
  1973年   6424篇
  1972年   4706篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
181.
A model of an expanding and rotating universe is constructed in the framework of general relativity. The parameters of the model are compared with the fundamental observables and shown to be in good agreement.Kaluzhsk Branch, N. É. Bauman Moscow State Technical University (MGTU). Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 71–77, June, 1993.  相似文献   
182.
A nonlinear integrodifferential equation that arises in polaron theory is considered. The integral nonlinearity is given by a convolution with the Coulomb potential. Radially symmetric solutions are sought. In the semiclassical limit, an equation for the self-consistent potential is found and studied. The potential has a logarithmic singularity at the origin, and also a turning point at 1. The phase shifts at these points are determined. The quantization rule that takes into account the logarithmic corrections gives a simple asymptotic formula for the polaron spectrum. Global semiclassical solutions of the original nonlinear equation are constructed.Moscow Institute of Electronic Engineering; Moscow Power Institute. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 97, No. 1, pp. 78–93, October, 1993.  相似文献   
183.
Investigations to the causes and effects of contaminants at the rf diode deposition of CrSi films in a non-heated high vacuum apparatus were carried out comparing an oxygen-free fusion target with an oxygen-containing cermet target. The films of the fusion target contained considerable amounts of oxygen; analogously the oxygen concentration in the films was increased in the case of the cermet target. Moreover, hydrogen was found. The concentration of the contaminants decreased with the sputtering power, however the rate of incorporation increased. For high sputtering rates the contamination process was reproducible and independent of the plant conditioning; the deposited films were depth-homogeneous. The reasons for this behaviour lie in water sources which are activated first of all by the discharge itself. The electrical properties found are explained by the contaminants and the deposition conditions.  相似文献   
184.
Translated from Matematicheskie Zametki, Vol. 50, No. 4, pp. 102–107, October, 1991.  相似文献   
185.
Raman mechanical spectroscopy was used to examine interfacial effects on the stress distribution in model polydiacetylene fiber/epoxy composites. Epoxy release agents were coated on fiber surfaces to modify the interfacial adhesion properties. The modified fiber surfaces were then characterized by scanning electron microscopy and x-ray photoelectron spectroscopy as well as optical microscopy. No difference in the maximum stress value or stress distribution was observed for the two types of fibers, coated or uncoated, used in composites. This suggests that adhesion properties at the composite interface do not affect tensile stress transfer efficiency nor, therefore, the composite tensile modulus along the fiber axis direction in uniaxial composites. Experimental data were also compared with theoretical calculations assuming perfect bonding between fiber and matrix, and idealized frictional force transfer mechanism at the fiber–matrix interface.  相似文献   
186.
Polarized light leads to an effective reorientation of the optic axis in the glassy state of liquid-crystalline side chain polymers containing azobenzene mesogenic groups, via a trans-cis and cis-trans isomerization. Using a combination of U V and IR dichroitic studies it is shown for copolymers consisting of chromophores (azobenzene) and non-chromophores (phenylbenzoate) that only the chromophores are reoriented by light as far as the glassy state is concerned. Individual chromophores are thus addressed by photoselection. Photoselection in the fluid nematic state, on the other hand, leads also to a reorientation of the non-chromophores.  相似文献   
187.
A novel method for measuring AMP-deaminase activity in human erythrocytes is presented, based on the determination of the reaction product, IMP, using high performance liquid chromatography. IMP formation was found to be proportional both to the incubation time and the amount of haemolysate over a wide range. The minimal detectable AMP-deaminase activity was more than 1000 times lower than the mean activity found in healthy controls (1083 nmol/h/mg Hb). No marked difference of activity was found in the patients with the following inherited purine disorders: familial juvenile gouty nephropathy and deficiencies of adenosine deaminase, hypoxanthine-guanine phosphoribosyltransferase or adenine phosphoribosyltransferase. The activity in the erythrocytes of patients with chronic renal failure was also similar to controls. The existence of subjects with low erythrocyte AMP-deaminase activity in the population has been confirmed.  相似文献   
188.
Translated from:Problemy Ustoichivosti Stokhasticheskikh Modelei, Trudy Seminara, 1989, pp. 20–26.  相似文献   
189.
190.
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