全文获取类型
收费全文 | 8096篇 |
免费 | 1318篇 |
国内免费 | 962篇 |
专业分类
化学 | 5765篇 |
晶体学 | 120篇 |
力学 | 455篇 |
综合类 | 53篇 |
数学 | 1135篇 |
物理学 | 2848篇 |
出版年
2024年 | 25篇 |
2023年 | 175篇 |
2022年 | 321篇 |
2021年 | 298篇 |
2020年 | 305篇 |
2019年 | 301篇 |
2018年 | 256篇 |
2017年 | 264篇 |
2016年 | 425篇 |
2015年 | 413篇 |
2014年 | 547篇 |
2013年 | 595篇 |
2012年 | 764篇 |
2011年 | 771篇 |
2010年 | 502篇 |
2009年 | 452篇 |
2008年 | 509篇 |
2007年 | 401篇 |
2006年 | 407篇 |
2005年 | 371篇 |
2004年 | 322篇 |
2003年 | 240篇 |
2002年 | 224篇 |
2001年 | 187篇 |
2000年 | 126篇 |
1999年 | 188篇 |
1998年 | 124篇 |
1997年 | 95篇 |
1996年 | 111篇 |
1995年 | 112篇 |
1994年 | 94篇 |
1993年 | 57篇 |
1992年 | 60篇 |
1991年 | 59篇 |
1990年 | 68篇 |
1989年 | 45篇 |
1988年 | 29篇 |
1987年 | 22篇 |
1986年 | 29篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1928年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Ching Sum Hui Lillian Sze Man Lam Chun Yin Wai Kin Chan Aleksandra B. Djurii 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1708-1715
Polyurethanes incorporated with rhenium diimine complexes were synthesized. The polymers exhibited interesting morphologies and solution properties. Results from gel permeation chromatography suggested the formation of polymer aggregates in solutions. The polymers could act as probes for metal ions. The addition of metal ions to polymer solutions led to significant changes in the electronic absorption properties of the polymer solutions. This was attributed to the interactions between the polyether moieties and metal ions. The metal complexes could also act as efficient photosensitizers. After doping with charge‐transport viologens, the photoconductivity of the polymers was greatly enhanced. The experimental quantum efficiency was simulated with Onsager's theory. The thermalization distances and the primary yields were typically 12–14 Å and 10?3, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1708–1715, 2003 相似文献
3.
Zhaoyang Yin 《Monatshefte für Mathematik》2004,141(4):337-344
We prove under quite general assumptions the existence of a bounded positive solution to the semilinear Schrödinger equation in a two-dimensional exterior domain. 相似文献
4.
For given a graph H, a graphic sequence π = (d
1, d
2,..., d
n) is said to be potentially H-graphic if there is a realization of π containing H as a subgraph. In this paper, we characterize the potentially (K
5 − e)-positive graphic sequences and give two simple necessary and sufficient conditions for a positive graphic sequence π to
be potentially K
5-graphic, where K
r is a complete graph on r vertices and K
r-e is a graph obtained from K
r by deleting one edge. Moreover, we also give a simple necessary and sufficient condition for a positive graphic sequence
π to be potentially K
6-graphic.
Project supported by National Natural Science Foundation of China (No. 10401010). 相似文献
5.
6.
Canonical correlation analysis based on information theory 总被引:2,自引:0,他引:2
In this article, we propose a new canonical correlation method based on information theory. This method examines potential nonlinear relationships between p×1 vector Y-set and q×1 vector X-set. It finds canonical coefficient vectors a and b by maximizing a more general measure, the mutual information, between aTX and bTY. We use a permutation test to determine the pairs of the new canonical correlation variates, which requires no specific distributions for X and Y as long as one can estimate the densities of aTX and bTY nonparametrically. Examples illustrating the new method are presented. 相似文献
7.
This work is devoted to near-optimal controls of large-scale discrete-time nonlinear dynamic systems driven by Markov chains; the underlying problem is to minimize an expected cost function. Our main goal is to reduce the complexity of the underlying systems. To achieve this goal, discrete-time control models under singularly-perturbed Markov chains are introduced. Using a relaxed control representation, our effort is devoted to finding near-optimal controls. Lumping the states in each irreducible class into a single state gives rise to a limit system. Applying near-optimal controls of the limit system to the original system, near-optimal controls of the original system are derived. 相似文献
8.
In this paper,the concept of the infinitesimal realization factor is extended to the parameter-dependent performance functions in closed queueing networks. Then the concepts of realization matrix (its elements are called realization factors) and performance potential are introduced,and the relations between infinitesimal realization factors and these two quantities are discussed. This provides a united framework for both IPA and non IPA approaches. Finally,another physical meaning of the service rate is given. 相似文献
9.
尹传存 《数学物理学报(A辑)》1997,17(2):145-151
设中的角域.该文绘出了A上正调和函数的Martin表示,讨论了极小调和函数与条件Brown运动的一个0—1律之间的关系,并给出了A上极小调和函数的表现形式, 相似文献
10.
Chuncheng Hao Zuolin Cui Yansheng Yin Zhikun Zhang 《Journal of nanoparticle research》2002,4(1-2):107-110
Nanostructured Fe3Al intermetallic compounds were produced by using hydrogen arc plasma method. The transmission electron microscopy experiments showed that the average particle size of the as-synthesized was about 40-nm. The change in hardness of Fe3Al nanostructured intermetallic compounds with annealing temperatures was observed and evaluated. 相似文献