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   35115篇
  免费   4483篇
  国内免费   3622篇
化学   14047篇
晶体学   410篇
力学   2262篇
综合类   655篇
数学   10137篇
物理学   15709篇
  2024年   60篇
  2023年   320篇
  2022年   768篇
  2021年   871篇
  2020年   868篇
  2019年   790篇
  2018年   772篇
  2017年   901篇
  2016年   1050篇
  2015年   959篇
  2014年   1467篇
  2013年   2492篇
  2012年   1635篇
  2011年   2022篇
  2010年   1864篇
  2009年   2371篇
  2008年   2455篇
  2007年   2501篇
  2006年   2255篇
  2005年   1805篇
  2004年   1493篇
  2003年   1531篇
  2002年   1442篇
  2001年   1236篇
  2000年   1126篇
  1999年   1026篇
  1998年   893篇
  1997年   696篇
  1996年   589篇
  1995年   472篇
  1994年   451篇
  1993年   391篇
  1992年   469篇
  1991年   299篇
  1990年   217篇
  1989年   220篇
  1988年   182篇
  1987年   183篇
  1986年   120篇
  1985年   167篇
  1984年   142篇
  1983年   84篇
  1982年   177篇
  1981年   217篇
  1980年   215篇
  1979年   237篇
  1978年   196篇
  1977年   135篇
  1976年   134篇
  1973年   103篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Homogeneously prepared tosylcelluloses (TC) with degrees of substitution (DS) of DSTos 0.1–1.8 were used as intermediates for the synthesis of methylaminocelluloses (MAC) by nucleophilic substitution with methylamine. TC with DSTos up to 1.1 were shown to be valuable intermediates for selective synthesis of MAC with DSMA varying from 0.1 to approximately 1. No nucleophilic substitution was observed at higher DSTos. At the chosen reaction conditions (60 °C, 48 h) residual tosyl moieties remained unchanged and little hydrolysis took place. The samples obtained were characterized by means of elemental analysis, FTIR and 13C CP/MAS NMR spectroscopy. 13C CP/MAS NMR spectroscopy was found to be an efficient tool for quantification of DSMA. Furthermore, the swelling behaviour in water was investigated and preliminary tests concerning the bilirubin adsorption capacity of MAC were carried out.  相似文献   
122.
本文用准平衡模型分析讨论了线性电压扫描下MIS器件的I/V瞬态.文中除了给出一般的处理方法以外,还给出了几种不同电压扫描率下I/Y特性的计算结果,并与已往的模型作了比较.  相似文献   
123.
In the present paper, a new two-parameter inverted equation of state (EOS) is developed which is found to be working very well in the high-pressure region. To check its success and validity, this EOS has been applied in a number of solids. The computed volume compression is found to be in very good agreement with the experimental data in the whole range of pressure in all the solids. The minimum and the maximum pressure range used in the present study is 0–320 kbar and 0–3000 kbar, respectively.  相似文献   
124.
In this paper, we prove the Hyers-Ulam-Rassias stability of homomorphisms in quasi-Banach algebras associated to the Pexiderized Cauchy functional equation. This is applied to investigate homomorphisms between quasi-Banach algebras. The concept of Hyers-Ulam-Rassias stability originated from Th.M. Rassias' stability theorem that appeared in his paper [Th.M. Rassias, On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978) 297-300].  相似文献   
125.
本文是通过对加速度的实验值和理论值进行比较和分析,给出误差的合理范围。  相似文献   
126.
There will be a review of the history of polarized proton beams, and a discussion of the unexpected and still unexplained large transverse spin effects found in several high-energy proton-proton spin experiments at the ZGS, AGS and Fermilab. Next, there will be a discussion of present and possible future experiments on the violent elastic collisions of polarized protons at IHEP-Protvino's 70GeV U-70 accelerator in Russia and the new high-intensity 50GeV J-PARC facility being built at Tokai in Japan.  相似文献   
127.
A new approach to the study of the Jaynes–Cummings sum, which determines the atomic inversion in quantum model of a single two-level atom interacting with a single mode of the quantized radiation field, based on the number theory theorems on approximation of trigonometric sums is presented.   相似文献   
128.
PURE STATE APPROACH TO C(x)_αZ_nLIBINGREN;LINQING(InstituteofMathematics,AcademiaSinica,Beijing100080,China.Projectsupportedbyth?..  相似文献   
129.
The Raman interaction of a ultracold ion trapped with two travelling wave lasers is studied analytically with series solutions, in the absence of the rotating wave approximation (RWA) and without restrictions of both the Lamb-Dicke limit and the weak excitation regime. The comparison is made between our solutions and those obtained under the RWA in order to demonstrate the validity region of the RWA. As a practical example, the preparation of Schr?dinger-cat states is proposed beyond the weak excitation regime, using our calculations. Received 12 March 2001 and Received in final form 16 October 2001  相似文献   
130.
为给转炉设计提供依据,需要计算炉液倾动的重心.利用数学方法将实际问题进行简化,通过分析炉液倾动过程中变量间的相互关系,来确定每个倾动角度对应情况下的液面位置.利用数学中三重积分的有关应用,进一步得出转炉在每个倾动角度为α∈(0,π2)时的重心计算方法及相关结论,在理论上为工程计算重心的方法提供参考.  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