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   300067篇
  免费   1569篇
  国内免费   356篇
化学   136814篇
晶体学   4651篇
力学   16868篇
综合类   3篇
数学   41998篇
物理学   99355篇
综合类   2303篇
  2021年   3098篇
  2020年   3413篇
  2019年   4190篇
  2018年   6229篇
  2017年   6449篇
  2016年   7946篇
  2015年   3522篇
  2014年   6877篇
  2013年   12105篇
  2012年   10156篇
  2011年   11849篇
  2010年   9985篇
  2009年   10129篇
  2008年   11459篇
  2007年   11271篇
  2006年   10036篇
  2005年   8664篇
  2004年   8410篇
  2003年   7822篇
  2002年   8118篇
  2001年   7766篇
  2000年   6174篇
  1999年   4540篇
  1998年   4268篇
  1997年   4126篇
  1996年   3736篇
  1995年   3298篇
  1994年   3361篇
  1993年   3375篇
  1992年   3424篇
  1991年   3831篇
  1990年   3832篇
  1989年   3833篇
  1988年   3578篇
  1987年   3669篇
  1986年   3360篇
  1985年   3896篇
  1984年   4105篇
  1983年   3513篇
  1982年   3697篇
  1981年   3388篇
  1980年   3149篇
  1979年   3655篇
  1978年   3719篇
  1977年   3888篇
  1976年   3966篇
  1975年   3708篇
  1974年   3584篇
  1973年   3705篇
  1972年   3194篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995.  相似文献   
92.
On the basis of the method of successive approximations in formal series we construct systems of particular solutions of the equations of planar and flexural harmonic vibrations of thin rectilinear anisotropic plates with a plane of symmetry of elastic properties parallel to the faces. The solutions constructed are classified as special sk-functions of generalized complex variables. Translated fromTeoreticheskaya i Prikladnaya Mekhanika No. 24, 1993, pp. 54–61.  相似文献   
93.
The characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2– was performed using17O,23Na,35Cl,133Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)2] n ·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 675–679, April, 1993.  相似文献   
94.
复数,实数及实对称数据下Bruun FFT算法的实现   总被引:3,自引:0,他引:3  
本文在复数、实数以及实对称数据下研究和实现了Bruun FFT算法。文章分析和评价了各种数据下BruunFFT的运算量和特点,提出了算法的实现结构和方法。最后给了TMS320C30上的运算时间,我们实现的算法比基2FFT速度提高35%。  相似文献   
95.
We consider tilde-geometries (orT-geometries), which are geometries belonging to diagrams of the following shape: Here the rightmost edge stands for the famous triple cover of the classical generalized quadrangle related to the group Sp4(2). The automorphism group of the cover is the nonsplit extension 3·Sp4(2) – 3 ·S 6. Five examples of flag-transitiveT-geometries were known. These are rank 3 geometries related to the groupsM 24 (the Mathieu group),He (the Held group) and and 37·Sp6(2) (a nonsplit extension); a rank 4 geometry related to the Conway groupCo 1 and a rank 5 geometry related to the Fischer-Griess Monster groupF 1. In the present paper we construct an infinite family of flag-transitiveT-geometries and prove that all the new geometries are simply connected. The automorphism group of the rankn geometry in the family is a nonsplit extension of a 3-group by the symplectic group Sp2n (2). The rank of the 3-group is equal to the number of 2-dimensional subspaces in ann-dimensional vector space over GF(2).  相似文献   
96.
The electrical conductivity of hydrosols of ultradispersed diamonds was studied. The electromembrane method for cleaning and concentrating of ultradispersed diamonds in hydrosols was considered. The influence exerted by the concentration of the dispersed phase on the electrical characteristics of the cleaning process was analyzed. A mathematical relation making it possible to evaluate the output characteristics of the process and to determine the geometrical characteristics of the apparatus was proposed.  相似文献   
97.
The radiation emitted by charged, scalar particles in a Schwarzschild field with maximal acceleration corrections is calculated classically and in the tree approximation of quantum field theory. In both instances the particles emit radiation that has characteristics similar to those of gamma-ray bursters.  相似文献   
98.
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism. Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process may be useful for the various optoelectronic applications of photoconductive a-Se layers. Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001  相似文献   
99.
This paper reports on the first experimental observation of quantum-well states and sp-type resonances in thin single-crystal gold, silver, and copper layers formed on single-crystal W(110) surfaces, which result from spatial localization of Bloch-type electronic wave functions in a quantum well with potential barriers at the vacuum/metal and metal/W(110) interfaces. The quantization of the valence-band electronic structure in Au/W(110), Ag/W(110), and Cu/W(110) systems was studied experimentally using angle-resolved photoelectron spectroscopy.  相似文献   
100.
Estimates of a rate of convergence of orderO(n –1) are obtained for integral functionals of an empirical process.Translated fromTeoriya Sluchainykh Protsessov, Vol. 15, pp. 10–16, 1987.  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