全文获取类型
收费全文 | 204443篇 |
免费 | 4681篇 |
国内免费 | 2804篇 |
专业分类
化学 | 75822篇 |
晶体学 | 2612篇 |
力学 | 14709篇 |
综合类 | 112篇 |
数学 | 55859篇 |
物理学 | 62814篇 |
出版年
2023年 | 587篇 |
2022年 | 1132篇 |
2021年 | 1058篇 |
2020年 | 1094篇 |
2019年 | 1101篇 |
2018年 | 18358篇 |
2017年 | 18984篇 |
2016年 | 10395篇 |
2015年 | 2958篇 |
2014年 | 2057篇 |
2013年 | 2881篇 |
2012年 | 10444篇 |
2011年 | 24249篇 |
2010年 | 14166篇 |
2009年 | 14542篇 |
2008年 | 18660篇 |
2007年 | 23838篇 |
2006年 | 2656篇 |
2005年 | 10347篇 |
2004年 | 6464篇 |
2003年 | 6448篇 |
2002年 | 3461篇 |
2001年 | 1713篇 |
2000年 | 1625篇 |
1999年 | 1177篇 |
1998年 | 967篇 |
1997年 | 916篇 |
1996年 | 1023篇 |
1995年 | 771篇 |
1994年 | 670篇 |
1993年 | 554篇 |
1992年 | 525篇 |
1991年 | 478篇 |
1990年 | 427篇 |
1989年 | 392篇 |
1988年 | 337篇 |
1987年 | 331篇 |
1986年 | 289篇 |
1985年 | 290篇 |
1984年 | 247篇 |
1983年 | 216篇 |
1982年 | 195篇 |
1981年 | 173篇 |
1980年 | 163篇 |
1979年 | 171篇 |
1978年 | 173篇 |
1976年 | 116篇 |
1975年 | 106篇 |
1973年 | 134篇 |
1968年 | 122篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
922.
René Meziat Diego Patiño Pablo Pedregal 《Computational Optimization and Applications》2007,38(1):147-171
We propose an alternative method for computing effectively the solution of non-linear, fixed-terminal-time, optimal control
problems when they are given in Lagrange, Bolza or Mayer forms. This method works well when the nonlinearities in the control
variable can be expressed as polynomials. The essential of this proposal is the transformation of a non-linear, non-convex
optimal control problem into an equivalent optimal control problem with linear and convex structure. The method is based on
global optimization of polynomials by the method of moments. With this method we can determine either the existence or lacking
of minimizers. In addition, we can calculate generalized solutions when the original problem lacks of minimizers. We also
present the numerical schemes to solve several examples arising in science and technology. 相似文献
923.
V. M. Arzhavitin 《Technical Physics》2003,48(6):797-799
The stressed state of in metallic composite systems is analyzed. It is analytically shown that the temperature dependences of the internal friction in the composites may have extrema that are caused by internal stresses. The analytical results are supported by the experimental temperature dependences of the internal friction in (Cu-13% Sn)-30% Nb and Cu-1.3% Cr composites. 相似文献
924.
Yuk-Kam Lau 《Archiv der Mathematik》2003,81(2):169-174
We establish a mean square estimate on the weight aspect for
symmetric square L-functions at every point
on the critical line.
Received: 15 February 2002 相似文献
925.
926.
The disregard of causal inference in the methodological literature about qualitative research is highly problematic, since the category of causality is closely linked to the concept of social action. However, it is also clear that causal analysis is burdened with certain difficulties and methodological challenges in the realm of social research. Some of these problems are discussed in this article using Mackie—s concept of 3 “INUS”-conditions. Thereby it will be shown that strategies of causal analysis based on comparative methods proposed for qualitative research, namely “Analytic Induction” and “Qualitative Comparative Analysis” have great difficulties in dealing adequately with these problems. They can only be solved, if case-comparative methods are combined with explorative research strategies which support the researcher in gaining access to the local knowledge of the research field. 相似文献
927.
We investigate the connection between the dynamics of
synchronization and the modularity on complex networks. Simulating
the Kuramoto's model in complex networks we determine patterns of
meta-stability and calculate the modularity of the partition these
patterns provide. The results indicate that the more stable the
patterns are, the larger tends to be the modularity of the partition
defined by them. This correlation works pretty well in homogeneous
networks (all nodes have similar connectivity) but fails when
networks contain hubs, mainly because the modularity is never
improved where isolated nodes appear, whereas in the synchronization
process the characteristic of hubs is to have a large stability when
forming its own community. 相似文献
928.
S. Mentus Dijana Jelić Veselinka Grudić 《Journal of Thermal Analysis and Calorimetry》2007,90(2):393-397
Thermal decomposition of lanthanum nitrate to lanthanum oxide was carried out by both temperature programmed heating (TPH)
and citrate-gel combustion. The temperature programmed heating was carried out under flow of oxidizing (air), neutral (nitrogen)
and reducing (25 vol.% hydrogen+argone mixture) gases, and the processes were controlled by simultaneous thermogravimetry
and differential thermal analysis. It was shown that hydrogen atmosphere helps to reduce temperatures of all decomposition
steps. The results of TPH were utilized to check the nature of residues in the products of lanthanum nitrate-to-oxide conversion
performed via citrate-gel combustion technique. 相似文献
929.
930.