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   2000篇
  免费   170篇
  国内免费   237篇
化学   208篇
晶体学   3篇
力学   55篇
综合类   34篇
数学   1601篇
物理学   506篇
  2024年   2篇
  2023年   25篇
  2022年   38篇
  2021年   37篇
  2020年   55篇
  2019年   51篇
  2018年   56篇
  2017年   56篇
  2016年   69篇
  2015年   63篇
  2014年   109篇
  2013年   154篇
  2012年   93篇
  2011年   125篇
  2010年   93篇
  2009年   132篇
  2008年   131篇
  2007年   137篇
  2006年   130篇
  2005年   107篇
  2004年   103篇
  2003年   93篇
  2002年   88篇
  2001年   64篇
  2000年   78篇
  1999年   61篇
  1998年   45篇
  1997年   39篇
  1996年   35篇
  1995年   25篇
  1994年   20篇
  1993年   10篇
  1992年   9篇
  1991年   9篇
  1990年   4篇
  1989年   8篇
  1987年   4篇
  1986年   4篇
  1985年   8篇
  1984年   6篇
  1983年   2篇
  1982年   6篇
  1981年   5篇
  1980年   4篇
  1979年   2篇
  1976年   3篇
  1974年   3篇
  1972年   1篇
  1969年   1篇
  1936年   1篇
排序方式: 共有2407条查询结果,搜索用时 15 毫秒
971.
Bottleneck routing games are a well-studied model to investigate the impact of selfish behavior in communication networks. In this model, each user selects a path in a network for routing her fixed demand. The disutility of a user only depends on the most congested link visited. We extend this model by allowing users to continuously vary the demand rate at which data is sent along the chosen path. As our main result we establish tight conditions for the existence of pure strategy Nash equilibria.  相似文献   
972.
In the article, we present some refinements of three classes of transformation inequalities for zero-balanced hypergeometric functions by use of the updated monotonicity criterion for the quotient of power series.  相似文献   
973.
We introduce the notion of bi-parametric potential-type operators, which generalize the Bessel and Flett potentials associated to singular Laplace–Bessel differential operator. Explicit inversion formulas for them are obtained by using a special wavelet-like transform, generated by the so-called ‘modified beta-semigroup’.  相似文献   
974.
侯邦品  刘杰  胡萍 《中国物理》2002,11(1):30-34
We discuss the effects of the initial atomic coherent factors (including the phase and the distribution parameter) and the dipole-dipole interaction on the sum and two-atom dipole squeezing in the system.The results show that the maximum squeezing in both cases is determined by the phase and the distribution parameter,and the duration of squeezing becomes longer by strengthening the dipole-dipole interaction.In addition,the comparison of the two types of squeezing shows that one type of squeezing is obtained at the expense of increased fluctuations in the other squeezing function.  相似文献   
975.
对高斯形截面的微通道中的流场进行了数值分析.结果表明,在压力驱动下,对于深宽比<3的通道,存在2个流速极值,此时通道的顶部对流体的输送也具有较大的贡献.对于深宽比>3的通道却只存在一个极值,此时顶部对流体输送几乎不起作用.研究结果对微通道中流体的流动特性研究具有指导意义.  相似文献   
976.
吕建钦  李金海 《中国物理》2004,13(10):1665-1668
The Lie algebraic method is applied to the analysis of the nonlinear transport of an intense pulsed beam in cylindrically symmetrical electrostatic lenses, and particle orbits in a six-dimensional phase space (x, p_x, y, p_y, τ, p_τ) are obtained in the second order approximation. They can also be acquired in the third or higher order approximation if needed. In the analysis, we divide the electrostatic lenses into several segments. Each segment is considered as a uniform accelerating field, and each dividing point is treated as a thin lens. The particle distribution in a three-dimensional ellipsoid is of Gaussian type.  相似文献   
977.
电解制备纯铁及其RRR_H法研究   总被引:2,自引:0,他引:2  
以工业废铁屑为原料制备高纯度电解铁 ,纯度可达 99.98%以上 .应用剩余电阻率比(RRRH)法 ,在外加垂直磁场 80 0 0e下分别测定该电解铁在 4 .2K和 2 98K时的电阻率 ,并得出样品对应的剩余电阻率比 (RRRH) .研究表明 :电解铁纯度越高 ,其RRRH 越大 .通过SEM断面形貌观察 ,在Ti基片上电解制备的纯铁非常致密  相似文献   
978.
A new cubic equation of state for simple fluids: pure and mixture   总被引:1,自引:0,他引:1  
A two-parameter cubic equation of state is developed. Both parameters are taken temperature dependent. Methods are also suggested to calculate the attraction parameter and the co-volume parameter of this new equation of state. For calculating the thermodynamic properties of a pure compound, this equation of state requires the critical temperature, the critical pressure and the Pitzer’s acentric factor of the component. Using this equation of state, the vapor pressure of pure compounds, especially near the critical point, and the bubble point pressure of binary mixtures are calculated accurately. The saturated liquid density of pure compounds and binary mixtures are also calculated quite accurately. The average of absolute deviations of the predicted vapor pressure, vapor volume and saturated liquid density of pure compounds are 1.18, 1.77 and 2.42%, respectively. Comparisons with other cubic equations of state for predicting some thermodynamic properties including second virial coefficients and thermal properties are given. Moreover, the capability of this equation of state for predicting the molar heat capacity of gases at constant pressure and the sound velocity in gases are also illustrated.  相似文献   
979.
Let M denote an even-dimensional noncompact hyperbolic manifold of finite volume. We show that such manifolds are candidates for minimal volume. Generalizing H. Hopf's ideas around the Curvatura integra for compact Clifford–Klein space forms, we present an elementary combinatorial-metrical proof of the Gauss–Bonnet formula for M. In contrast to former results of G. Harder and M. Gromov, our approach doesn't make use of the arithmetical and differential geometrical machinery.  相似文献   
980.
An overview of the various transformations of isothermic surfaces and their interrelations is given using aquaternionic formalism. Applications to the theory of cmc-1 surfaces inhyperbolic space are given and relations between the two theories are discussed. Within this context, we give Möbius geometric characterizations for cmc-1 surfaces in hyperbolic space and theirminimal cousins.  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