全文获取类型
收费全文 | 3600篇 |
免费 | 437篇 |
国内免费 | 315篇 |
专业分类
化学 | 1419篇 |
晶体学 | 15篇 |
力学 | 195篇 |
综合类 | 40篇 |
数学 | 1766篇 |
物理学 | 917篇 |
出版年
2024年 | 6篇 |
2023年 | 76篇 |
2022年 | 68篇 |
2021年 | 97篇 |
2020年 | 107篇 |
2019年 | 106篇 |
2018年 | 91篇 |
2017年 | 109篇 |
2016年 | 109篇 |
2015年 | 122篇 |
2014年 | 200篇 |
2013年 | 424篇 |
2012年 | 171篇 |
2011年 | 199篇 |
2010年 | 179篇 |
2009年 | 222篇 |
2008年 | 234篇 |
2007年 | 240篇 |
2006年 | 202篇 |
2005年 | 162篇 |
2004年 | 164篇 |
2003年 | 156篇 |
2002年 | 101篇 |
2001年 | 110篇 |
2000年 | 100篇 |
1999年 | 70篇 |
1998年 | 79篇 |
1997年 | 80篇 |
1996年 | 65篇 |
1995年 | 44篇 |
1994年 | 35篇 |
1993年 | 23篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 6篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1973年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有4352条查询结果,搜索用时 671 毫秒
21.
Mathematical Notes - 相似文献
22.
Ji-hong SU & Yi-cai ZHAO LMAM Department of Mathematics Jinan University Guangzhou China 《中国科学A辑(英文版)》2007,50(4):495-502
Let X be a smooth projective variety of dimension 2k-1 (k≥3) over the complex number field. Assume that fR: X→Y is a small contraction such that every irreducible component Ei of the exceptional locus of fR is a smooth subvariety of dimension k. It is shown that each Ei is isomorphic to the k-dimensional projective space Pk, the k-dimensional hyperquadric surface Qk in Pk 1, or a linear Pk-1-bundle over a smooth curve. 相似文献
23.
A review of the optimal stopping problem with more than a single decision maker (DM) is presented in this paper. We classify
the existing literature according to the arrival of the offers, the utility of the DMs, the length of the sequence of offers,
the nature of the game and the number of offers to be selected. We enumerate various definitions for this problem and describe
some dynamic approaches.
Fouad Ben Abdelaziz is on leave from the Institut Superieur de Gestion, University of Tunis, Tunisia e-mail: foued.benabdelaz@isg.run.tn. 相似文献
24.
由“从正则分布出发,在小涨落近似下得出的能量涨落分布公式”求得的能量涨落的二次矩与直接由正则分布求得的二次矩完全相同,但分别由二求得的高次矩并不完全相同。 相似文献
25.
Reaction diffusion systems on cylindrical domains with terms that vary rapidly and periodically in the unbounded direction can be analyzed by averaging techniques. Here, using iterated normal form transformations and Gevrey regularity of bounded solutions, we prove a result on exponential averaging for such systems, i.e., we show that traveling wave solutions can be described by a spatially homogenous equation and exponentially small remainders. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
26.
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
27.
There is a high correlation between molecular surface area (TSA) of triorganotin and triorganolead compounds and their toxicity towards a bacterium (Escherichia coli) and an alga (Selenastrum capricornutum). Parallel attempts to correlate other Group IVA organometals incorporating silicon or germanium were unsuccessful. It was further demonstrated, however, that a high correlation was obtainable between certain series of compounds with the same organic substituent but different metal centers involving all Group IVA elements. In both instances, the inability to obtain a quantitative structure-activity relationship (QSAR) for all systems studied appears to be a function of the solubility of the compounds. While organotin TSA values have been found to correlate well with their toxicities toward various organisms, this study clearly suggests that this type of QSAR can be readily extended to include other organometal systems, provided that there is no solubility problem and the toxicity is a function of the hydrophobicity of the organometal compounds. 相似文献
28.
本文给出Om×GLn作用于Cm,n上的复多项式环上的最高权向量环的Krull维数公式,从而改正了Aslaksen,Tan及Zhu的一个错误. 相似文献
29.
Manufacturing cell formation using similarity coefficients and a parallel genetic TSP algorithm: Formulation and comparison 总被引:2,自引:0,他引:2
J. BalakrishnanP. D. Jog 《Mathematical and Computer Modelling》1995,21(12):61-73
Many algorithms have been proposed to form manufacturing cells from component routings. However, many of these do not have the capability of solving large problems. We propose a procedure using similarity coefficients and a parallel genetic implementation of a TSP algorithm that is capable of solving large problems of up to 1000 parts and 1000 machines. In addition, we also compare our procedure with many existing procedures using nine well-known problems from the literature.
The results show that the proposed procedure compares well with the existing procedures and should be useful to practitioners and researchers. 相似文献
30.