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   320601篇
  免费   870篇
  国内免费   480篇
化学   157597篇
晶体学   6288篇
力学   15361篇
综合类   10篇
数学   33654篇
物理学   109041篇
  2020年   3107篇
  2019年   3594篇
  2018年   4743篇
  2017年   4910篇
  2016年   6419篇
  2015年   3411篇
  2014年   5715篇
  2013年   12458篇
  2012年   9953篇
  2011年   11937篇
  2010年   9221篇
  2009年   9458篇
  2008年   11497篇
  2007年   11179篇
  2006年   10510篇
  2005年   9427篇
  2004年   8949篇
  2003年   8203篇
  2002年   8412篇
  2001年   10178篇
  2000年   7485篇
  1999年   5858篇
  1998年   4782篇
  1997年   4675篇
  1996年   4331篇
  1995年   3913篇
  1994年   3888篇
  1993年   3767篇
  1992年   4250篇
  1991年   4657篇
  1990年   4437篇
  1989年   4515篇
  1988年   4358篇
  1987年   4355篇
  1986年   4048篇
  1985年   4997篇
  1984年   5018篇
  1983年   4248篇
  1982年   4327篇
  1981年   4043篇
  1980年   3865篇
  1979年   4371篇
  1978年   4584篇
  1977年   4645篇
  1976年   4673篇
  1975年   4387篇
  1974年   4271篇
  1973年   4474篇
  1972年   3381篇
  1971年   3001篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
We consider the possibility of finding experimental evidence of the fifth force with the measurement of a phase shift of neutron beams via an interferometric apparatus and also a possible rotation of the polarization plane of polarized neutron beams when torsion is introduced in a gravitational field.  相似文献   
92.
93.
94.
95.
Bismuth, antimony and its alloys are the typical representatives of a class of semimetals, which electric conductance is lower in 102-103 times, than of usual well conducting an electrical current metals. The alloys bismuth with antimony have semi-conductor properties in wide area of compositions at temperatures below 77 °K. The semimetals are rather perspective materials from the point of view of their probable application in various devices [1,2,3].In present time the semimetal alloys BiSb have wide application in thermoelectric generators and refrigerators. In work [3] the opportunity of use of semimetals BiSb with percentage content of Bi and Sb from 8 % up to 25 % was shown as high-sensitivity and of small inertion indicators of the mm range radiation where thermoelectric effect is used. The principle of action of such indicators is based on occurrence of temperature gradient in a semimetal crystal BiSb that has two contacts of the various area with flowing electrical current. Basic element of such device is the dot contact metal - semimetal. One of the main characteristics is volt-watt sensitivity of metal-semimetal BiSb contact which calculating is shown in present work.  相似文献   
96.
A solution is constructed for an orthotropic layer with free plane faces, that corresponds to the plane elastic waves symmetric over the thickness. The dynamical reconstruction of the normal wave spectrum during rotation of the wave vector from one to another elastically equivalent direction is investigated on the basis of a numerical analysis of the dispersion equation.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 19, pp. 116–121, 1988.  相似文献   
97.
Defect formation and annealing processes in fullerene C60 at T = (4000–6000) K are studied using molecular dynamics with a tight-binding potential. The cluster lifetime until fragmentation, which proceeds, as a rule, through the loss of a C2 dimer, has been found as a function of temperature. The activation energy and the frequency factor in the Arrhenius equation for the fragmentation rate have been found to be E a = (9.2 ± 0.4) eV and A = (8 ± 1) × 1019s?1. It is shown that fragmentation can occur already after the C60 cluster loses its spherical shape. This fact must be taken into account in theoretical calculations of E a.  相似文献   
98.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 965–969, June, 1991.  相似文献   
99.
Nonlinear (at the second-harmonic frequency of the incident light) optical reflection by two-dimensional magnetic superstructures is theoretically studied. A square lattice of magnetic dots and a hexagonal lattice of magnetic bubbles (cylindrical magnetic domains) are considered. Because the periods of these structures are comparable with the wavelengths of the fundamental and the second-harmonic radiation, it would be possible to observe diffraction at the second-harmonic frequency. A polarization analysis of nonlinearly diffracted radiation is performed and the numbers of observable diffraction orders for the above structures are estimated. Received: 10 January 2002 / Published online: 11 June 2002  相似文献   
100.
A method is proposed for determining the similarities and differences between the experimental distribution of particles in a disperse system with respect to a significant feature-particle size (sample) and the corresponding distribution (likeness), selected from the diversity of theoretical distributions with positive and negative asymmetry. The aim of the comparison is to extract the necessary information about the nature of the internal processes in the disperse system evolving as a result of the Ostwald reaction coagulation of microparticles. The procedure of comparing the distributions is illustrated on the example of the histogram of disperse Al3Mg2 particles of an aluminum-magnesium alloy heated isothermally at 430°C.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 80–84, December, 1991.  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