全文获取类型
收费全文 | 174216篇 |
免费 | 16939篇 |
国内免费 | 12107篇 |
专业分类
化学 | 93521篇 |
晶体学 | 1850篇 |
力学 | 11937篇 |
综合类 | 667篇 |
数学 | 43446篇 |
物理学 | 51841篇 |
出版年
2024年 | 244篇 |
2023年 | 2000篇 |
2022年 | 3082篇 |
2021年 | 3562篇 |
2020年 | 4115篇 |
2019年 | 3876篇 |
2018年 | 13088篇 |
2017年 | 12642篇 |
2016年 | 10391篇 |
2015年 | 5453篇 |
2014年 | 6067篇 |
2013年 | 7827篇 |
2012年 | 12661篇 |
2011年 | 19328篇 |
2010年 | 11920篇 |
2009年 | 11964篇 |
2008年 | 12901篇 |
2007年 | 14254篇 |
2006年 | 5772篇 |
2005年 | 5885篇 |
2004年 | 5093篇 |
2003年 | 4817篇 |
2002年 | 3622篇 |
2001年 | 2454篇 |
2000年 | 2225篇 |
1999年 | 2199篇 |
1998年 | 1922篇 |
1997年 | 1700篇 |
1996年 | 1746篇 |
1995年 | 1479篇 |
1994年 | 1314篇 |
1993年 | 1094篇 |
1992年 | 953篇 |
1991年 | 838篇 |
1990年 | 700篇 |
1989年 | 560篇 |
1988年 | 434篇 |
1987年 | 395篇 |
1986年 | 391篇 |
1985年 | 308篇 |
1984年 | 230篇 |
1983年 | 189篇 |
1982年 | 166篇 |
1981年 | 116篇 |
1980年 | 105篇 |
1979年 | 68篇 |
1978年 | 56篇 |
1973年 | 42篇 |
1914年 | 45篇 |
1909年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
Jing-na Li Xiao-feng Wang Zheng-an Yao 《应用数学学报(英文版)》2007,23(3):421-432
In this paper, we propose a model in studying soft ferromagnetic films, which is readily accessible experimentally. By using penalty approximation and compensated compactness, we prove that the dynamical equation in thin film has a local weak solution. Moreover, the corresponding linear equation is also dealt with in great detail. 相似文献
962.
D Shaw 《The Journal of the Operational Research Society》2006,57(7):830-841
Problem-structuring group workshops can be used in organizations as a consulting tool and as a research tool. One example of the latter is using a problem-structuring method (PSM) to help a group tackle an organizational issue; meanwhile, researchers collect the participants’ initial views, discussion of divergent views, the negotiated agreement, and the reasoning for outcomes emerging. Technology can help by supporting participants in freely sharing their opinions and by logging data for post-workshop analyses. For example, computers let participants share views anonymously and without being influenced by others (as well as logging those views), and video-cameras can record discussions and intra-group dynamics. This paper evaluates whether technology-supported Journey Making workshops can be effective research tools that can capture quality research data when compared against theoretical performance benchmarks and other qualitative research tools. 相似文献
963.
Alexander Semenov Aurélia Charlot Rachel Auzély-Velty Marguerite Rinaudo 《Rheologica Acta》2007,46(5):541-568
Dynamics of associating polymer solutions above the reversible gelation point are studied. Each macromolecule consists of
a soluble backbone (B) and a small fraction of specific strongly interacting groups (A or C stickers) attached to B. A mixture
of B–A and B–C associating polymers with 1:1 stoichiometric ratio is considered. As a result of AC association, the polymers
reversibly gelate above the overlap concentration. It is shown that (1) the network strands are linear complexes (double chains)
of B–A and B–C; (2) “diffusion” of the network junction points is characterized by an apparent activation energy, which can
be significantly higher than the energy of one AC bond; (3) most importantly, the randomness of sticker distribution along
the chain can significantly slow down the network relaxation leading to a markedly non-Maxwellian viscoelastic behavior. The
theory elucidates the most essential features of rheological behavior of polysaccharide associating systems (with A = adamantyl
moiety, C = β-cyclodextrin, B = either chitosan or hyaluronan) including similar behavior of G
′ and G
″ in a wide frequency range, strong temperature dependence of the characteristic frequency ω
x
, and an extremely strong effect of added free stickers (fC) on the dynamics.
This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27–29, 2006. 相似文献
964.
Jing Ping YANG Shi Hong CHENG Xiao Qian WANG 《数学学报(英文版)》2007,23(3):467-478
This paper investigates bivariate recursive equations on excess-of-loss reinsurance. For an insurance portfolio, under the assumptions that the individual claim severity distribution has bounded continuous density and the number of claims belongs to R1 (a, b) family, bivariate recursive equations for the joint distribution of the cedent's aggregate claims and the reinsurer's aggregate claims are obtained. 相似文献
965.
Meghan Griffith 《Acta Analytica》2007,22(1):16-28
In this paper, I argue that trying is the locus of freedom and moral responsibility. Thus, any plausible view of free and
responsible action must accommodate and account for free tryings. I then consider a version of agent causation whereby the
agent directly causes her tryings. On this view, the agent is afforded direct control over her efforts and there is no need
to posit—as other agent-causal theorists do—an uncaused event. I discuss the potential advantages of this sort of view, and
its challenges. 相似文献
966.
Louis Block James Keesling Shihai Li Kevin Peterson 《Journal of statistical physics》1989,55(5-6):929-939
A new algorithm is presented for computing the topological entropy of a unimodal map of the interval. The accuracy of the algorithm is discussed and some graphs of the topological entropy which are obtained using the algorithm are displayed. 相似文献
967.
本文利用85年5—6月间对乌鲁木齐市主要商业区及部分中、小商业区的实地调查资料,对乌市商业中心等级系统进行了定性和定量的分级分类,将全市商业中心划分为五个等级,八组商业中心,对已形成的商业中心分布现状进行了初步探讨,并对今后商业网点的合理布局提出了建议。 相似文献
968.
969.
We give a new independent self-dual 3-basis for the trivial variety with two binary operations.
Received October 24, 2006; accepted in final form January 25, 2007. 相似文献
970.
A mistake concerning the ultra LI-ideal of a lattice implication algebra is pointed out, and some new sufficient and necessary conditions for an LI-ideal to be an ultra LI-ideal are given. Moreover, the notion of an LI-ideal is extended to MTL-algebras, the notions of a (prime, ultra, obstinate, Boolean) LI-ideal and an ILI-ideal of an MTL-algebra are introduced, some important examples are given, and the following notions are proved to be equivalent in MTL-algebra: (1) prime proper LI-ideal and Boolean LI-ideal, (2) prime proper LI-ideal and ILI-ideal, (3) proper obstinate LI-ideal, (4) ultra LI-ideal.
This work was supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. Y605389) and K. C. Wong
Magna Fund in Ningbo University. 相似文献