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   418499篇
  免费   2386篇
  国内免费   794篇
化学   183154篇
晶体学   6049篇
力学   25743篇
综合类   3篇
数学   78913篇
物理学   127817篇
  2021年   3458篇
  2020年   3793篇
  2019年   4625篇
  2018年   16906篇
  2017年   16861篇
  2016年   14659篇
  2015年   4868篇
  2014年   7935篇
  2013年   14340篇
  2012年   15333篇
  2011年   23667篇
  2010年   16716篇
  2009年   17272篇
  2008年   19430篇
  2007年   21175篇
  2006年   11779篇
  2005年   11218篇
  2004年   11077篇
  2003年   10879篇
  2002年   10158篇
  2001年   9260篇
  2000年   7342篇
  1999年   5438篇
  1998年   5186篇
  1997年   4936篇
  1996年   4491篇
  1995年   3940篇
  1994年   3955篇
  1993年   3976篇
  1992年   4005篇
  1991年   4457篇
  1990年   4359篇
  1989年   4410篇
  1988年   4117篇
  1987年   4127篇
  1986年   3859篇
  1985年   4481篇
  1984年   4794篇
  1983年   4090篇
  1982年   4314篇
  1981年   3940篇
  1980年   3676篇
  1979年   4172篇
  1978年   4350篇
  1977年   4520篇
  1976年   4487篇
  1975年   4228篇
  1974年   4084篇
  1973年   4261篇
  1972年   3563篇
排序方式: 共有10000条查询结果,搜索用时 578 毫秒
931.
932.
Measurements of response, gain, and noise immunity are carried out for an underwater compensated additive receiving array with randomly spaced hydrophones that is moored at the bottom of a man-made lake with multimode sound propagation. The in-sea locating ability of a similar array is demonstrated with the sources of noiselike signals at frequencies of 5–100 Hz. A dedicated numerical processor is developed and tested for processing the signals received by a random underwater array.  相似文献   
933.
A hydrophone calibration procedure that considerably reduces the error caused by the acoustic field distortions in a hydroacoustic tank is proposed. The procedure is based on the definition of the reduced electric transfer impedances of transducers (i.e., the electric transfer impedances reduced to the spherical wave propagation law) and consists in measuring the electric transfer impedances for different distances between hydroacoustic transducers. The sensitivity of the hydrophone under calibration is calculated from the far-field values of the reduced electric transfer impedances. The latter are determined using a mathematical model of the hydrophone in the form of a system that contains a point sensing element and a finite number of point sources of acoustic signals (point reflectors). A method of determining the number and coordinates of the point reflectors from the analysis of the acoustic “images” of the hydrophone’s reflecting surface is proposed. The measuring technique, the algorithms of mathematical processing, and the results of experimental studies are considered. A comparative analysis of the results of the hydrophone calibration with respect to the field by the reciprocity method is performed for the cases of using the conventional technique and the proposed method.  相似文献   
934.
935.
936.
The phenomenon of extraordinary ray refraction in a helical liquid crystal with large (compared to the light wavelength) pitch has been studied by theoretical and experimental methods. At a sufficiently large angle of incidence relative to the pitch axis, the extraordinary ray exhibits reflection (reversal) from a certain layer of the medium. The ordinary ray, for which the system is optically isotropic, exhibits no such reflection. The experimental dependences of the transmitted and reflected (reversed) rays are described using the geometrical optics approximation taking into account the optical losses for scattering inside the liquid crystal.  相似文献   
937.
Thermoelectric effects are investigated theoretically in layered conductors with a quasi-two-dimensional electron energy spectrum of arbitrary type in a strong magnetic field. It is shown that, at temperatures sufficiently low for quantization of the orbital motion of charge carriers in a magnetic field to be required, there exist giant quantum oscillations of the thermoelectric field. Thermoelectric emf is studied as a f unction of the orientation of the magnetic field with respect to the layers; experimental investigation of this function allows one to determine the velocity distribution of conduction electrons on the Fermi surface.  相似文献   
938.
The magnetic absorption cross section of a small spherical particle with a dielectric core and a metallic shell is calculated. The general case is considered when the ratio of the radius of the dielectric core to the total radius of the particle may take arbitrary values. The condition of specular-diffuse reflection of conduction electrons from the surfaces of the metal layer of the particle is chosen as the boundary conditions of the problem. The limit cases are considered, and the results are discussed.  相似文献   
939.
Deeper insight into the features of a reactor as a source of antineutrinos is required for making further advances in studying the fundamental properties of the neutrino. The relationship between the thermal power of a reactor and the rate of the chain fission reaction in its core is analyzed.  相似文献   
940.
A phenomenological model for describing the production of Centauro events in relativistic heavy-ion collisions is discussed. The model provides quantitative predictions for kinematical variables, for the baryon number, and for the masses of a Centauro fireball and of its decay products. A Centauro fireball decays predominantly into nucleons, strange hyperons, and possibly strangelets. Centauro events in Pb + Pb collisions at the LHC energy are simulated for the CASTOR detector. The signatures of these events are discussed in detail.  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