全文获取类型
收费全文 | 24228篇 |
免费 | 2730篇 |
国内免费 | 1397篇 |
专业分类
化学 | 1360篇 |
晶体学 | 146篇 |
力学 | 3676篇 |
综合类 | 311篇 |
数学 | 17815篇 |
物理学 | 5047篇 |
出版年
2024年 | 44篇 |
2023年 | 221篇 |
2022年 | 303篇 |
2021年 | 368篇 |
2020年 | 556篇 |
2019年 | 533篇 |
2018年 | 571篇 |
2017年 | 688篇 |
2016年 | 701篇 |
2015年 | 504篇 |
2014年 | 1012篇 |
2013年 | 1825篇 |
2012年 | 1145篇 |
2011年 | 1244篇 |
2010年 | 1140篇 |
2009年 | 1446篇 |
2008年 | 1543篇 |
2007年 | 1666篇 |
2006年 | 1481篇 |
2005年 | 1314篇 |
2004年 | 1120篇 |
2003年 | 1233篇 |
2002年 | 1057篇 |
2001年 | 861篇 |
2000年 | 849篇 |
1999年 | 781篇 |
1998年 | 644篇 |
1997年 | 590篇 |
1996年 | 429篇 |
1995年 | 374篇 |
1994年 | 262篇 |
1993年 | 259篇 |
1992年 | 220篇 |
1991年 | 197篇 |
1990年 | 159篇 |
1989年 | 83篇 |
1988年 | 98篇 |
1987年 | 89篇 |
1986年 | 83篇 |
1985年 | 112篇 |
1984年 | 101篇 |
1983年 | 51篇 |
1982年 | 60篇 |
1981年 | 69篇 |
1980年 | 43篇 |
1979年 | 53篇 |
1978年 | 55篇 |
1977年 | 45篇 |
1976年 | 29篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 81 毫秒
61.
L. T. Ashchepkov 《Computational Mathematics and Mathematical Physics》2006,46(7):1168-1175
A general nonlinear programming problem with interval functions is considered. Two reductions of this problem to the deterministic nonlinear programming problem are proposed, and illustrative examples are discussed. 相似文献
62.
We present a Darboux transformation for Tzitzeica equation associated with 3 × 3 matrix spectral problem. The explicit solution of Tzitzeica equation is obtained. 相似文献
63.
An implicit quasi-monotone second-order accurate method is proposed for analyzing the spiral Couette flow of a rarefied gas between coaxial cylinders. The basic advantages of the method over the conventional method of stationry iterations are that the former is conservative with respect to the collision integral, has a simple software implementation for any types of boundary conditions, and applies to a wide range of Knudsen numbers. 相似文献
64.
G. Tiana M.H. Jensen K. Sneppen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):135-140
A feedback mechanism that involves the proteins p53 and mdm2, induces cell death as a controlled response to severe DNA damage.
A minimal model for this mechanism demonstrates that the response may be dynamic and connected with the time needed to translate
the mdm2 protein. The response takes place if the dissociation constant k between p53 and mdm2 varies from its normal value. Although it is widely believed that it is an increase in k that triggers the response, we show that the experimental behaviour is better described by a decrease in the dissociation
constant. The response is quite robust upon changes in the parameters of the system, as required by any control mechanism,
except for few weak points, which could be connected with the onset of cancer.
Received 8 May 2002 / Received in final form 9 July 2002 Published online 17 September 2002 相似文献
65.
Patrick Dehornoy 《Algebra Universalis》2002,48(2):223-248
We solve the word problem of the identity x(yz) = (xy)(yz) by investigating a certain group describing the geometry of that identity. We also construct a concrete realization of the
one-generated free algebra relative to the above identity.
Received March 23, 2001; accepted in final form July 6, 2002. 相似文献
66.
Existence and Uniqueness of Endemic States for the Age-structured MSEIR Epidemic Model 总被引:1,自引:0,他引:1
Geni Gupur 《应用数学学报(英文版)》2002,18(3):441-454
The existence and uniqueness of positive steady states for the age-structured MSEIR epidemic model with age-dependent transmission coefficient is considered. Threshold results for the existence of endemic states are established; under certain conditions, uniqueness is also shown. 相似文献
67.
We investigate an operator renormalization group method to extract and describe the relevant degrees of freedom in the evolution of partial differential equations. The proposed renormalization group approach is formulated as an analytical method providing the fundamental concepts of a numerical algorithm applicable to various dynamical systems. We examine dynamical scaling characteristics in the short-time and the long-time evolution regime providing only a reduced number of degrees of freedom to the evolution process. 相似文献
68.
从立方抛物线谈起(1)--余弦型振动,椭圆余弦型振动与双曲线型非周期运动 总被引:1,自引:1,他引:0
从立方抛物线的特性谈起 ,用较初浅的方法 ,借助于雅可比椭圆函数求椭圆方程的解来说明一大类一维保守系统的余弦振动、椭圆余弦型振动与双曲线型非周期运动 .并以杜芬振子、单摆、倒摆、转动圆环上的小环运动为典型实例作了详细讨论 相似文献
69.
We establish the existence and stability of multidimensional transonic shocks for the Euler equations for steady potential compressible fluids. The Euler equations, consisting of the conservation law of mass and the Bernoulli law for the velocity, can be written as a second-order, nonlinear equation of mixed elliptic-hyperbolic type for the velocity potential. The transonic shock problem can be formulated into the following free boundary problem: The free boundary is the location of the transonic shock which divides the two regions of smooth flow, and the equation is hyperbolic in the upstream region where the smooth perturbed flow is supersonic. We develop a nonlinear approach to deal with such a free boundary problem in order to solve the transonic shock problem. Our results indicate that there exists a unique solution of the free boundary problem such that the equation is always elliptic in the downstream region and the free boundary is smooth, provided that the hyperbolic phase is close to a uniform flow. We prove that the free boundary is stable under the steady perturbation of the hyperbolic phase. We also establish the existence and stability of multidimensional transonic shocks near spherical or circular transonic shocks.
70.
利用变分法证明平面调和函数的外问题的确切形式;在此基础上,建立外问题的具有间接变量的等价边界积分方程;传统的外问题及边界积分方程不具有普遍适用性,本文对此进行了详细的讨论. 相似文献