全文获取类型
收费全文 | 25300篇 |
免费 | 2836篇 |
国内免费 | 1516篇 |
专业分类
化学 | 1532篇 |
晶体学 | 148篇 |
力学 | 3722篇 |
综合类 | 344篇 |
数学 | 18762篇 |
物理学 | 5144篇 |
出版年
2024年 | 44篇 |
2023年 | 231篇 |
2022年 | 315篇 |
2021年 | 398篇 |
2020年 | 591篇 |
2019年 | 564篇 |
2018年 | 599篇 |
2017年 | 723篇 |
2016年 | 731篇 |
2015年 | 535篇 |
2014年 | 1050篇 |
2013年 | 1885篇 |
2012年 | 1190篇 |
2011年 | 1288篇 |
2010年 | 1182篇 |
2009年 | 1516篇 |
2008年 | 1594篇 |
2007年 | 1730篇 |
2006年 | 1554篇 |
2005年 | 1376篇 |
2004年 | 1172篇 |
2003年 | 1293篇 |
2002年 | 1096篇 |
2001年 | 902篇 |
2000年 | 889篇 |
1999年 | 814篇 |
1998年 | 684篇 |
1997年 | 630篇 |
1996年 | 448篇 |
1995年 | 404篇 |
1994年 | 279篇 |
1993年 | 270篇 |
1992年 | 233篇 |
1991年 | 208篇 |
1990年 | 167篇 |
1989年 | 86篇 |
1988年 | 106篇 |
1987年 | 94篇 |
1986年 | 87篇 |
1985年 | 120篇 |
1984年 | 104篇 |
1983年 | 53篇 |
1982年 | 67篇 |
1981年 | 69篇 |
1980年 | 45篇 |
1979年 | 55篇 |
1978年 | 56篇 |
1977年 | 45篇 |
1976年 | 34篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
ON THE UNIQUENESS OF THE WEAK SOLUTIONS OF A QUASILINEAR HYPERBOLIC SYSTEM WITH A SINGULAR SOURCE TERM 下载免费PDF全文
This paper is a continuation of the authors'previous paper[1].In this paper the authorsprove,assuming additional conditions on the initial data,some results about the existence anduniqueness of the entropy weak solutions of the Cauchy problem for the singular hyperbolicsystem a_t+(au)_x_2au/x=0,u_t+1/2(a~2+u~2)_x=0,x>0,t≥0. 相似文献
62.
When an organization solves a portfolio problem with public projects evaluated by multiple criteria, in which the economic dimension is not essential or not well characterized, the classical methods are not useful. We propose a non-linear preference model developed from normative Value Theory and using fuzzy sets to model some sources of imprecision. This model can be considered as a generalization of the classical approaches. However, the optimization problem is very complex in order to be solved with non-linear programming techniques. Therefore, the model is exploited by an evolutionary algorithm, able to achieve a strong improvement of the quality of solution. 相似文献
63.
In this paper necessary and sufficient conditions of null-controllability and approximate null-controllability are obtained for the wave equation on a half-axis. Controls solving these problems are found explicitly. Moreover, bang-bang controls solving the approximate null-controllability problem are constructed with the aid of solutions of a frequency extinguishing problem in the restricted band (−a,a) for this equation and the Markov power moment problem. 相似文献
64.
This paper gives some global and uniform convergence estimates for a class of subspace correction (based on space decomposition) iterative methods applied to some unconstrained convex optimization problems. Some multigrid and domain decomposition methods are also discussed as special examples for solving some nonlinear elliptic boundary value problems.
65.
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
66.
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
67.
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
68.
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
69.
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
70.
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