全文获取类型
收费全文 | 56233篇 |
免费 | 9297篇 |
国内免费 | 5678篇 |
专业分类
化学 | 38162篇 |
晶体学 | 499篇 |
力学 | 3596篇 |
综合类 | 373篇 |
数学 | 6519篇 |
物理学 | 22059篇 |
出版年
2024年 | 207篇 |
2023年 | 1203篇 |
2022年 | 2085篇 |
2021年 | 2193篇 |
2020年 | 2243篇 |
2019年 | 2181篇 |
2018年 | 1989篇 |
2017年 | 1768篇 |
2016年 | 2757篇 |
2015年 | 2556篇 |
2014年 | 3116篇 |
2013年 | 4174篇 |
2012年 | 4972篇 |
2011年 | 5065篇 |
2010年 | 3346篇 |
2009年 | 3250篇 |
2008年 | 3554篇 |
2007年 | 3078篇 |
2006年 | 2823篇 |
2005年 | 2381篇 |
2004年 | 1792篇 |
2003年 | 1414篇 |
2002年 | 1294篇 |
2001年 | 1038篇 |
2000年 | 991篇 |
1999年 | 1247篇 |
1998年 | 1000篇 |
1997年 | 973篇 |
1996年 | 957篇 |
1995年 | 866篇 |
1994年 | 731篇 |
1993年 | 671篇 |
1992年 | 528篇 |
1991年 | 485篇 |
1990年 | 439篇 |
1989年 | 333篇 |
1988年 | 280篇 |
1987年 | 242篇 |
1986年 | 191篇 |
1985年 | 174篇 |
1984年 | 134篇 |
1983年 | 90篇 |
1982年 | 93篇 |
1981年 | 51篇 |
1980年 | 43篇 |
1979年 | 17篇 |
1976年 | 17篇 |
1975年 | 15篇 |
1973年 | 15篇 |
1957年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Ping-xing Chen Jian-ming Cai Zheng-wei Zhou Guang-can Guo 《量子光学学报》2006,12(B08):72-73
The second law of thermodynamics is one of the most fundamental and for-reaching laws of physics. It teaches us that when a closed system undergoes a thermodynamic process the entropy of the system never decreases; it increases, or at least remains constant. If the entropy increases the thermodynamic process is irreversible, otherwise it is reversible. Only ideal thermal process is reversible. In classical world a great number of facts have proved the second law is true. But in quantum world since the quantum coherence and correlations exist we are not sure the second law is still true, at least in principle. This is because that: 1. on the microscopic level the irreversibility is conflict with the reversibility of all fundamental physical laws ; 2. there are not enough evidences to show it is true in quantum world. 相似文献
93.
94.
Some Results behind Dividend Problems 总被引:1,自引:0,他引:1
Ming Zhou Li Wei Jun-yi Guo 《应用数学学报(英文版)》2006,22(4):681-686
We consider the basic dividend problem of the compound Poisson model with constant barrierstrategy.Some results concealed behind the dividend problem are made explicit in the present work.Differentmethods and some of which are firstly given in this paper.All these results presented certain direct relationshipbetween some important actuary variables in classical risk theory is also revealed. 相似文献
95.
96.
97.
1IntroductionThispaperisconcernedwithpositivesolutionOfthesemilinearheatequationswithlocalizedreactionssubjecttoeitherinitialconditions(Cauchyproblem)ortheinitialandboundary-value(DirichletorNeumanntype)conditionswherenisaboundeddomaininRe,icEO.Equations(1.1)canbethoughtofasamodeltodescribesomephysicalphenomena(heatpropagation,chemicalreaction)inwhichthenonlinearreactionsinadynndcalsystemtakesplaceonlyatasinglesite.InthesequelforconvenienceweshallsamplycalltheCauchy,initial-Direchlet,orini… 相似文献
98.
Jipu Ma 《中国科学A辑(英文版)》1997,40(12):1233-1238
A generalized dimension is further developed. Here subtraction and addition of two generalized dimensions are defined, so
that the operations: ∞ ± n = ∞, ∞ + ∞ = ∞, which used to play an inflexible role, are refined and moreover, ∞ - ∞, which used
to be meaningless, is done in sense. Then generalized index for semi-Fred-holm operators is developed to wholeB(H), i.e. all of bounded linear operators in Hilbert spaceH. Theorem 2.2 is proved with an example, which is in contradiction to a known proposition for semi-Fredholm operators in form,
practically a refined result of the known proposition. Then, it is proved thatB(H) is the union of countably many disjoint arewise connected sets over all the generalized dimensions ofB(H).
Project supported by the National Natural Science Foundation of China 相似文献
99.
Films of polytetrafluoroethylene (PTFE) were exposed to sodium naphthalenide (Na/naphtha) etchant so as to defluorinate the surface for obtaining hydroxyl functionality. Surface-initiators were immobilized on the PTFE films by esterification of 4,4′-azobis(4-cyanopentanoic acid) (ACP) and the hydroxyl groups covalently linked to the surface. Grafting of polymer brushes on the PTFE films was carried out by the surface-initiated free radical polymerization. Homopolymers brushes of methyl methacrylate (MMA) were prepared by free radical polymerization from the azo-functionalized PTFE surface. The chemical composition and topography of the graft-functionalized PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance (ATR) FT-IR spectroscopy and atomic force microscopy (AFM). Water contact angles on PTFE films were reduced by surface grafting of MMA. 相似文献
100.