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   704440篇
  免费   5432篇
  国内免费   1779篇
化学   347427篇
晶体学   10191篇
力学   36544篇
综合类   22篇
数学   100864篇
物理学   216603篇
  2021年   5832篇
  2020年   6361篇
  2019年   7197篇
  2018年   13641篇
  2017年   13977篇
  2016年   15539篇
  2015年   7944篇
  2014年   12509篇
  2013年   29310篇
  2012年   24893篇
  2011年   33394篇
  2010年   23513篇
  2009年   23402篇
  2008年   30696篇
  2007年   32555篇
  2006年   23323篇
  2005年   23791篇
  2004年   20939篇
  2003年   19350篇
  2002年   18074篇
  2001年   18561篇
  2000年   14593篇
  1999年   11162篇
  1998年   9535篇
  1997年   9383篇
  1996年   8903篇
  1995年   8058篇
  1994年   7933篇
  1993年   7650篇
  1992年   8207篇
  1991年   8626篇
  1990年   8275篇
  1989年   8075篇
  1988年   7988篇
  1987年   7782篇
  1986年   7408篇
  1985年   9447篇
  1984年   10041篇
  1983年   8392篇
  1982年   8788篇
  1981年   8382篇
  1980年   7944篇
  1979年   8430篇
  1978年   8778篇
  1977年   8580篇
  1976年   8634篇
  1975年   8192篇
  1974年   8013篇
  1973年   8436篇
  1972年   5987篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
New analytical formulas for the torsionL-tensor are reported, which are used in molecular normal mode analysis calculations for the nonlinear transformation of the force constants from internal coordinates to normal coordinates. The proposed formalism exhibits a relative simplicity as compared to previous reported results. Sample calculations for methanol and hydrazine are presented.  相似文献   
72.
73.
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   
74.
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed.  相似文献   
75.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective.  相似文献   
76.
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   
77.
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   
78.
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   
79.
The Al2O3−CdSe interface of a thin-film transistor is investigated in the frequency range 30 Hz-30 kHz under weak depletion and accumulation. The surface states are, most likely, located in the insulator Al2O3 with a concentration varying from 4·1018 to 1019 cm−3 eV−1. The surface states have a negligible influence on the thin-film transistor operation.  相似文献   
80.
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   
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