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   436203篇
  免费   4858篇
  国内免费   1231篇
化学   233870篇
晶体学   6490篇
力学   18766篇
综合类   13篇
数学   49961篇
物理学   133192篇
  2021年   3771篇
  2020年   4193篇
  2019年   4520篇
  2018年   5853篇
  2017年   5748篇
  2016年   8842篇
  2015年   5570篇
  2014年   8549篇
  2013年   20192篇
  2012年   15665篇
  2011年   19270篇
  2010年   13506篇
  2009年   13364篇
  2008年   17658篇
  2007年   17550篇
  2006年   16260篇
  2005年   14557篇
  2004年   13526篇
  2003年   11897篇
  2002年   11730篇
  2001年   13432篇
  2000年   10086篇
  1999年   7917篇
  1998年   6571篇
  1997年   6316篇
  1996年   6083篇
  1995年   5470篇
  1994年   5393篇
  1993年   5197篇
  1992年   5828篇
  1991年   5924篇
  1990年   5665篇
  1989年   5472篇
  1988年   5493篇
  1987年   5375篇
  1986年   5092篇
  1985年   6560篇
  1984年   6697篇
  1983年   5301篇
  1982年   5387篇
  1981年   5367篇
  1980年   4955篇
  1979年   5352篇
  1978年   5491篇
  1977年   5385篇
  1976年   5328篇
  1975年   4914篇
  1974年   4886篇
  1973年   4880篇
  1972年   3455篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
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   
22.
To investigate local ordering and segregation phenomenon in a Ni91Pt9-alloy after sputtering and annealing a 3D optical atom probe (OAP) has been used. The specimen tips have been prepared from polycrystalline samples. To sputter the samples a separate preparation chamber with a scannable Ar-sputter-gun is connected to the OAP vessel. When necessary, the sample can be electrically heated to induce segregation and cure the altered layer. After a heat treatment of a Ni91 at. %Pt 9 at.% specimen at 1100 K the surface of a (111)-oriented specimen is enriched in platinum by a factor of two in relation to the bulk. The phenomenon of short-range ordering has been investigated on the surface and in the subsurface volume. A 3D reconstruction of this annealed NiPt specimen shows regions with high concentration of platinum that gives an indication at short-range ordering. Uniform sputtering of the tip without a heat treatment induces a decisive depletion of Pt on the surface and the following subatomic layers. The atom-probe results of specimens in thermal equilibrium are in close agreement to further surface sensitive results obtained from Ion Scattering Spectroscopy (ISS) and Auger Electron Spectroscopy (AES).  相似文献   
23.
We develop an approach to the solution of the spinless Bethe-Salpeter equation for the different-mass case. Although the calculations are developed for spinzero particles in any arbitratry spherically symmetric potential, the non-Coulombic effective power-law potential is used as a kernel to produce the spin-averaged bound states of the non-self-conjugate mesons. The analytical formulas are also applicable to the self-conjugate mesons in the equal-mass case. The flavor-independent case is investigated in this work. The calculations are carried out to the third-order correction of the energy series. Results are consistent with those obtained before.  相似文献   
24.
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   
25.
The problem of the vector and axial-vector dominance of weak interactions within the framework of the quark model of superconductivity type is discussed.  相似文献   
26.
27.
28.
29.
30.
One obtains a formula for the transformation of a vector with a given covariance matrix. The sum of the squares of the components of the transformed vector is equal to a chi-square type quadratic form, constructed with the aid of the initial vector. Taking into account this property, one finds the components of the Pearson statistic, Pearson-Fisher statistic, etc.Translated from Veroyatnostnye Raspredeleniya i Matematicheskaya Statistika, pp. 337–350, 1986.  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