全文获取类型
收费全文 | 857篇 |
免费 | 17篇 |
国内免费 | 9篇 |
专业分类
化学 | 361篇 |
力学 | 68篇 |
数学 | 317篇 |
物理学 | 137篇 |
出版年
2022年 | 5篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 20篇 |
2018年 | 19篇 |
2017年 | 22篇 |
2016年 | 28篇 |
2015年 | 28篇 |
2014年 | 47篇 |
2013年 | 79篇 |
2012年 | 42篇 |
2011年 | 50篇 |
2010年 | 43篇 |
2009年 | 43篇 |
2008年 | 60篇 |
2007年 | 53篇 |
2006年 | 50篇 |
2005年 | 29篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 26篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1972年 | 3篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1938年 | 2篇 |
1936年 | 4篇 |
1932年 | 2篇 |
排序方式: 共有883条查询结果,搜索用时 33 毫秒
41.
We give sufficient conditions for the rigid body in the presence of an axisymmetric force field and a gyroscopic torque to admit a Hamilton-Poisson formulation. Even if by adding a gyroscopic torque we initially lose one of the conserved Casimirs, we recover another conservation law as a Casimir function for a modified Poisson structure. We apply this frame to several well-known results in the literature. 相似文献
42.
Lucian M. Ionescu 《Applied Categorical Structures》2002,10(1):35-47
We review several known categorification procedures, and introduce a functorial categorification of group extensions (Section 4.1) with applications to non-Abelian group cohomology (Section 4.2). The obstruction to the existence of group extensions (Section 4.2.4, Equation (9)) is interpreted as a coboundary condition (Proposition 4.5). 相似文献
43.
We present exact numerical results indicating that ionization could be a useful tool to study electron correlations in artificial molecules and nanoarrays of metallic quantum dots. For nanorings consisting of Ag quantum dots of the type already fabricated, we demonstrate that the molecular orbital picture breaks down even for lowest energy ionization processes, in contrast to ordinary molecules. Our ionization results yield a transition point between localization and delocalization regimes in good agreement with various experimental data. 相似文献
44.
Vlad Ionescu 《Integral Equations and Operator Theory》1999,34(1):45-55
Based on the Ben Artzi-Gohberg result concerning the equivalence between the invertibility of theL
2-operator
and the exponential dichotomic evolution defined byA(t), the time-varying counterpart of the Redheffer theorem is considered under relaxed conditions. 相似文献
45.
A new cell is described which allows simultaneous measurement of the electrical and catalytic properties of a promoted Bi–Mo catalyst. The electrical resistance data show that the interaction of propylene with the catalyst starts at 310 °C.
, Bi–Mo. , 310°C.相似文献
46.
47.
“Real” (111) surfaces of n-type GaAs were investigated employing surface photovoltage spectroscopy and the surface piezoelectric effect. Surface states at the energy position Ec ? Et ? 0.72 eV were found on both the Ga and the As surfaces. Both types of surfaces exhibited a barrier of about 0.55 V. No variations in the surface barrier or the energy position of the surface states were observed in various ambients at atmospheric pressure (dry air, wet air, ammonia and ozone). However, the capture cross-section of the surface states for electrons, as determined from the surface piezoelectric effect transients (of the order of 10?13 cm2), was found to be sensitive to the ambient. It decreased in wet air and increased in ozone. This effect was more pronounced on the As than on the Ga surfaces. Additional surface states were found to be present in the energy region of 0.9 to 1.0 eV, below the bottom of the conduction band. However, their exact energy positions could not be determined due to interference caused by the carrier trapping of the surface states at Ec ? Et ? 0.72 eV. 相似文献
48.
49.
Channel proteins that selectively conduct molecules across cell membranes often exhibit an asymmetric structure. By means of a stochastic model, we argue that channel asymmetry in the presence of nonequilibrium fluctuations, fueled by the cell's metabolism as observed recently, can dramatically influence the transport through such channels by a ratchetlike mechanism. For an aquaglyceroporin that conducts water and glycerol, we show that a previously determined asymmetric glycerol potential leads to enhanced inward transport of glycerol, but for unfavorably high glycerol concentrations also to enhanced outward transport that protects a cell against poisoning. 相似文献
50.
Cristodor Ionescu 《代数通讯》2013,41(12):4801-4805
In this note we will prove that the Hochschild homology algebra of a topological algebra and its universally complete differential algebra are isomorphic in the case of a formally smooth morphism 相似文献