全文获取类型
收费全文 | 9038篇 |
免费 | 1006篇 |
国内免费 | 769篇 |
专业分类
化学 | 759篇 |
晶体学 | 17篇 |
力学 | 955篇 |
综合类 | 174篇 |
数学 | 6802篇 |
物理学 | 2106篇 |
出版年
2024年 | 10篇 |
2023年 | 106篇 |
2022年 | 138篇 |
2021年 | 174篇 |
2020年 | 223篇 |
2019年 | 262篇 |
2018年 | 238篇 |
2017年 | 276篇 |
2016年 | 293篇 |
2015年 | 236篇 |
2014年 | 396篇 |
2013年 | 700篇 |
2012年 | 439篇 |
2011年 | 520篇 |
2010年 | 455篇 |
2009年 | 563篇 |
2008年 | 592篇 |
2007年 | 574篇 |
2006年 | 535篇 |
2005年 | 436篇 |
2004年 | 404篇 |
2003年 | 434篇 |
2002年 | 414篇 |
2001年 | 337篇 |
2000年 | 320篇 |
1999年 | 283篇 |
1998年 | 314篇 |
1997年 | 238篇 |
1996年 | 175篇 |
1995年 | 115篇 |
1994年 | 111篇 |
1993年 | 81篇 |
1992年 | 63篇 |
1991年 | 56篇 |
1990年 | 34篇 |
1989年 | 28篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 32篇 |
1984年 | 36篇 |
1983年 | 15篇 |
1982年 | 23篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1974年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
本文给出递归集的Hausdorff维数的下界估计,并由此确定了一类递归集的维数,所获结果包含并推广了Bedford,Dekking及文志英、钟红柳等人的有关结果。 相似文献
82.
Jiqin Deng 《Journal of Mathematical Analysis and Applications》2007,332(1):475-486
In this paper, by using the fixed point theory, under quite general conditions on the nonlinear term, we obtain an existence result of bounded positive solutions of Schrödinger equations in two-dimensional exterior domains. 相似文献
83.
This paper discusses a class of second-order derivative nonlinear Schrödinger equations which are used to describe the upper-hybrid oscillation propagation. By establishing a variational problem, applying the potential well argument and the concavity method, we prove that there exists a sharp condition for global existence and blow-up of the solutions to the nonlinear Schrödinger equation. In addition, we also answer the question: how small are the initial data, the global solutions exist? 相似文献
84.
Eugene Savov 《Complexity》2007,12(3):61-76
The solar wind makes the magnetosphere to expand and contract as indicated by the expansions and contractions of the auroral oval due to balancing of the dynamic pressure of the ambient space plasma at inner and outer magnetic lines. This self‐similar magnetospheric behavior elucidates the controversial magnetic storm‐substorm relationship and reveals the 3D‐spiral structure of magnetic interaction. The found self‐similarly evolving structure of one seen as fundamental interaction suggests dynamic fractal unifying interaction that builds a firework universe having 3D‐spiral code. The unifying interaction is described with equation drawn in new fundamental dynamic fractal framework. The equation of unifying interaction converges to the inverse square laws and the principle of uncertainty at laboratory scales. The dynamic fractal fundamental framework is made of one 3D‐spirally‐faster‐inward contracting and expanding, oscillating, basic matter. It simply accounts for observed constant speed of light and for the creation of bright and dark bands on a screen behind a tiny slit. The dynamic fractal framework is quantitatively confirmed with the orbital data for the Milky Way Galaxy, the Sun, the Earth, and the triple asteroid system 87 Sylvia. Many testable predictions are also made. The presented new fundamental dynamic fractal framework allows qualitative and quantitative modeling and simplification. © 2007 Wiley Periodicals, Inc. Complexity 12: 61–76, 2007 相似文献
85.
On a question of Gross 总被引:1,自引:0,他引:1
Abhijit Banerjee 《Journal of Mathematical Analysis and Applications》2007,327(2):1273-1283
Using the notion of weighted sharing of sets we prove two uniqueness theorems which improve the results proved by Fang and Qiu [H. Qiu, M. Fang, A unicity theorem for meromorphic functions, Bull. Malaysian Math. Sci. Soc. 25 (2002) 31-38], Lahiri and Banerjee [I. Lahiri, A. Banerjee, Uniqueness of meromorphic functions with deficient poles, Kyungpook Math. J. 44 (2004) 575-584] and Yi and Lin [H.X. Yi, W.C. Lin, Uniqueness theorems concerning a question of Gross, Proc. Japan Acad. Ser. A 80 (2004) 136-140] and thus provide an answer to the question of Gross [F. Gross, Factorization of meromorphic functions and some open problems, in: Proc. Conf. Univ. Kentucky, Lexington, KY, 1976, in: Lecture Notes in Math., vol. 599, Springer, Berlin, 1977, pp. 51-69], under a weaker hypothesis. 相似文献
86.
For one‐dimensional simple symmetric random walk, the Hausdorff and packing dimensions of sets of sample paths with prescribed rate of returns to the origin are determined. This gives a multifractal decomposition of the underlying sample space. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
87.
P. C. Chen 《中国化学会会志》1995,42(5):755-760
Three ab initio calculations (HF/6-3IG, HF/6-3IG*, and HF/6-3IG**) on 2,4,6-trinitrotoluene were made, The results compare well with xray data, except dihedral angles of NO2 relative to the plane of the benzene ring. The deviations are attributed to packing forces and steric effects in the crystal. The most stable structure was a torsional angle 10° of the methyl top with the benzene ring, unlike toluene. The rotational barriers of the methyl top and the 4-nitro group are small. Hydrogen bonding, dipole moments and total atomic charges arc calculated. 相似文献
88.
微裂纹扩展中的分形现象及其计算机仿真 总被引:1,自引:0,他引:1
本文探讨了采用仿真技术研究微裂纹连接过程和生成分形断口表面的可行性,发展了用于仿真微裂纹随机生长行为的GO模型的基本构相,并进行了计算机仿真实验,由此得出了一此有的结论。 相似文献
89.
We address in this paper the problem of finding an optimal strategy for dealing with bottleneck machines and bottleneck parts in the cell formation process in group technology. Three types of economic decisions are considered: subcontracting, machine duplication and intercell moves. The problem is formulated as a minimum weighted node covering problem in a hypergraph, and we show that it can be solved in polynomial time by finding a maximum weighted stable set in a bipartite graph. We extend this result to cellular manufacturing systems in which the sequence of operations of each part is known in advance. 相似文献
90.
Jaroslav Neetil 《Journal of Graph Theory》2002,39(2):108-110
A graph G is called rigid if the identical mapping V(G)→V(G) is the only homomorphism G→G. In this note we give a simple construction of a rigid oriented graph on every set. © 2002 John Wiley & Sons, Inc. J Graph Theory 39: 108–110, 2002 相似文献