全文获取类型
收费全文 | 905篇 |
免费 | 50篇 |
国内免费 | 9篇 |
专业分类
化学 | 606篇 |
晶体学 | 5篇 |
力学 | 28篇 |
数学 | 138篇 |
物理学 | 187篇 |
出版年
2023年 | 9篇 |
2022年 | 8篇 |
2021年 | 18篇 |
2020年 | 13篇 |
2019年 | 35篇 |
2018年 | 14篇 |
2017年 | 7篇 |
2016年 | 27篇 |
2015年 | 35篇 |
2014年 | 38篇 |
2013年 | 60篇 |
2012年 | 71篇 |
2011年 | 62篇 |
2010年 | 35篇 |
2009年 | 39篇 |
2008年 | 61篇 |
2007年 | 55篇 |
2006年 | 47篇 |
2005年 | 39篇 |
2004年 | 39篇 |
2003年 | 42篇 |
2002年 | 33篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1966年 | 4篇 |
排序方式: 共有964条查询结果,搜索用时 171 毫秒
121.
The rate of electron-positron pair production in a weak external electric field at large values of e is computed. The method is extended to compute the rate of monopole-antimonopole pair production in a weak external magnetic field at large magnetic charge. 相似文献
122.
Kyung Sam Park Soung Hie Kim Wan Chul Yoon 《The Journal of the Operational Research Society》1996,47(11):1415-1420
This paper is concerned with the use of incomplete information about utilities and weights in multiattribute decisionmaking. Because of time pressure and/or lack of knowledge, a decision maker may only be able to provide incomplete information which might be expressed as a set of linear inequalities. If the decision maker's information on both weights and utilities is imprecisely identified, then the model for establishing pairwise dominance becomes a non-linear program. A method for obtaining non-dominated alternatives without solving the non-linear program is proposed using a simple weighted-additive function. 相似文献
123.
Recently Kim has given a general method, using group-invariant orbit parameters, for determining the energy and residual symmetry of the Higgs potential minimum. In this paper we illustrate the method by working out the case of a quartic SU(5) Higgs potential with and higgsons. In this method the Gell-Mann-Slansky conjecture concerning possible little groups of the potential minimum takes a geometric form, which is verified for our case. The results are used to discuss the hierarchical symmetry breaking of SU(5) grand unification theory. We generalize our results to the SU(N) adjoint + vector models, which are all closely related. 相似文献
124.
The rate of monopole pair production in a weak external magnetic field is computed by a semiclassical method. The result is analogous to that for electron-positron pair production in an electric field. 相似文献
125.
Methyl and ethyl isocyanide undergo isomerization to the corresponding nitriles when irradiated with the focused output of a CO2 TEA laser. This process is shown to be isotopically selective for nitrogen isotopes when operating pressures are on the order of 1 to 2 torr. At higher pressures thermal isomerization becomes dominant. 相似文献
126.
Phytochemical investigation of Ginkgo biloba (Ginkgoaceae) has resulted in the isolation of two new biflavone glucosides, ginkgetin 7'-O-beta-D-glucopyranoside (1) and isoginkgetin 7-O-beta-D-glucopyranoside (2). The structures were determined on the basis of chemical and spectroscopic evidences. 相似文献
127.
Simulations on the thermal decomposition of a poly(dimethylsiloxane) polymer using the ReaxFF reactive force field 总被引:1,自引:0,他引:1
Chenoweth K Cheung S van Duin AC Goddard WA Kober EM 《Journal of the American Chemical Society》2005,127(19):7192-7202
To investigate the failure of the poly(dimethylsiloxane) polymer (PDMS) at high temperatures and pressures and in the presence of various additives, we have expanded the ReaxFF reactive force field to describe carbon-silicon systems. From molecular dynamics (MD) simulations using ReaxFF we find initial thermal decomposition products of PDMS to be CH(3) radical and the associated polymer radical, indicating that decomposition and subsequent cross-linking of the polymer is initiated by Si-C bond cleavage, in agreement with experimental observations. Secondary reactions involving these CH(3) radicals lead primarily to formation of methane. We studied temperature and pressure dependence of PDMS decomposition by following the rate of production of methane in the ReaxFF MD simulations. We tracked the temperature dependency of the methane production to extract Arrhenius parameters for the failure modes of PDMS. Furthermore, we found that at increased pressures the rate of PDMS decomposition drops considerably, leading to the formation of fewer CH(3) radicals and methane molecules. Finally, we studied the influence of various additives on PDMS stability. We found that the addition of water or a SiO(2) slab has no direct effect on the short-term stability of PDMS, but addition of reactive species such as ozone leads to significantly lower PDMS decomposition temperature. The addition of nitrogen monoxide does not significantly alter the degradation temperature but does retard the initial production of methane and C(2) hydrocarbons until the nitrogen monoxide is depleted. These results, and their good agreement with available experimental data, demonstrate that ReaxFF provides a useful computational tool for studying the chemical stability of polymers. 相似文献
128.
129.
A new mechanism for baryogenesis is proposed. It is argued that, after inflation, the scalar quarks and leptons of a supersymmetric GUT may have large expectation values. The subsequent evolution of such a system is shown to generate a significant baryon density. For typical values of the parameters, nB/nγ may be as large as 103. 相似文献
130.