全文获取类型
收费全文 | 6940篇 |
免费 | 789篇 |
国内免费 | 834篇 |
专业分类
化学 | 5297篇 |
晶体学 | 89篇 |
力学 | 298篇 |
综合类 | 80篇 |
数学 | 1060篇 |
物理学 | 1739篇 |
出版年
2024年 | 12篇 |
2023年 | 132篇 |
2022年 | 196篇 |
2021年 | 232篇 |
2020年 | 285篇 |
2019年 | 308篇 |
2018年 | 253篇 |
2017年 | 253篇 |
2016年 | 313篇 |
2015年 | 355篇 |
2014年 | 397篇 |
2013年 | 580篇 |
2012年 | 612篇 |
2011年 | 586篇 |
2010年 | 462篇 |
2009年 | 419篇 |
2008年 | 500篇 |
2007年 | 417篇 |
2006年 | 391篇 |
2005年 | 291篇 |
2004年 | 230篇 |
2003年 | 161篇 |
2002年 | 192篇 |
2001年 | 135篇 |
2000年 | 109篇 |
1999年 | 99篇 |
1998年 | 61篇 |
1997年 | 64篇 |
1996年 | 62篇 |
1995年 | 32篇 |
1994年 | 40篇 |
1993年 | 31篇 |
1992年 | 26篇 |
1991年 | 25篇 |
1990年 | 26篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1979年 | 10篇 |
1978年 | 19篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 9篇 |
排序方式: 共有8563条查询结果,搜索用时 305 毫秒
41.
The Newton filtration and d-determination of bifurcation problems related to C~0 contact equivalence
SU Dan & ZHANG Dunmu School of Mathematics Statistics Wuhan University Wuhan China 《中国科学A辑(英文版)》2006,49(5)
In this paper, from the Newton filtration's point of view, we construct the singular Riemannian metric and use the method in singular theory to study the bifurcation problems, and give the sufficient condition of d-determination of bifurcation problems with respect to C0 contact equivalence. The special cases of the main result in this paper are the results of Sun Weizhi and Zou Jiancheng. 相似文献
42.
Previous studies using dideuterium as a solute have demonstrated the importance for orientation of the interaction between the solute molecular quadrupole moment and the average electric field gradient present in liquid crystals. With the aim of learning about additional orientational mechanisms, we have studied the temperature dependence of the 2H-NMR spectra of the liquid crystal 5CB-d19 as the solute in three liquid crystal mixtures: 55 wt % 1132/EBBA, 56·5 wt % 1132/EBBA and 70 wt % 5CB/EBBA. In these mixtures, the contribution from the environment to the average electric field gradient at the 2H nucleus of dideuterium is zero. The spectra of 5CB-d19 in the mixtures 55 wt % 1132/EBBA and 56·5 wt % 1132/EBBA are equivalent, but are different from those in 70 wt % 5CB/EBBA. The spectra of 5CB in 55 wt % 1132/EBBA and 70 wt % 5CB/EBBA are analysed using two different models for the short range potential, and param eters of the models are used to compare the potentials in the different mixtures. For a given spectral splitting of the chain C1 deuteron, the reduced short range potential is the same in all three mixtures studied. The spectral differences observed are a consequence of different nematic-isotropic phase transition temperatures combined with the effect of trans/gauche-isomerization in the hydrocarbon chain. 相似文献
43.
G. Michałek B.R. Bułka 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):121-128
The currents and their fluctuations in two capacitively coupled single electron transistors are determined in the limit of
sequential tunnelling. Our considerations are restricted to the case when the islands (dots) of the transistors are atomic-sized,
which means each of them has only one single electronic level available for the tunnelling processes. The Coulomb interactions
of accumulated charges on the both single electron transistors lead to the effect of the negative differential resistance.
An enhancement of the current shot-noise was also found. Spectral decomposition analysis indicated the two main contributions
to the shot-noise: low- and high-frequency fluctuations. It was found that the low frequency fluctuations (polarization noise)
are responsible for a strong enhancement of the current noise.
Received 9 October 2001 / Received in final form 8 March 2002 Published online 9 July 2002 相似文献
44.
45.
Sz.-Nagy's dilation theorem for a contraction on a Hilbert space has been extended by Mlak to the case of a contraction semigroup whose indices are the positive elements of a totally ordered discrete group. We generalize to this case the intertwining lifting theorem of Sz.-Nagy and Foias. Some previous interpolation results on ordered groups are obtained as consequences. 相似文献
46.
Dan Archdeacon C. Paul Bonnington Joanna A. Ellis-Monaghan 《Discrete and Computational Geometry》2007,38(3):573-594
Steinitz's theorem states that a graph is the 1-skeleton of a convex polyhedron if and only if it is 3-connected and
planar. The polyhedron is called a geometric realization of the embedded graph. Its faces are bounded by convex polygons whose
points are coplanar. A map on the torus does not necessarily have such a geometric realization. In this paper we relax the
condition that faces are the convex hull of coplanar points. We require instead that the convex hull of
the points on a face can be projected onto a plane so that the boundary of the convex hull of the projected points is the
image of the boundary of the face. We also require that the interiors of the convex hulls of different faces do not intersect.
Call this an exhibition of the map. A map is polyhedral if the intersection of any two closed faces is simply connected. Our
main result is that every polyhedral toroidal map can be exhibited. As a corollary, every toroidal triangulation has a geometric
realization. 相似文献
47.
48.
A simple and sensitive method was conducted for the determination of trace amounts of proteins with benzeneazo-8-acetylamino-1-naphthol-3,6-disulfonic acid sodium salt (azophloxine, AP) using a Rayleigh light-scattering (RLS) technique. At pH 2.60 and in the presence of an emulsifier OP microemulsion, the RLS of AP can be greatly enhanced by proteins, owing to the interaction between AP and protein. The enhanced intensity is proportional to the concentration of proteins. Four proteins, including bovine serum albumin (BSA), human serum albumin (HSA), lysozyme (Lys) and gamma globulin (gamma-G) have been tested. For example, the linear range of BSA was 0 - 0.06 microg mL(-1) with detection limits of 2.38 ng mL(-1). The method was applied to the analysis of protein in human urine and penicillin samples with satisfactory results. The relative standard deviation was in all instances less than 4.0%, and the recovery was in the range of 97.5 - 104%. 相似文献
49.
The newton filtration and d-determination of bifurcation problems related to C
0 contact equivalence
In this paper, from the Newton filtration’s point of view, we construct the singular Riemannian metric and use the method in singular theory to study the bifurcation problems, and give the sufficient condition of d-determination of bifurcation problems with respect to C 0 contact equivalence. The special cases of the main result in this paper are the results of Sun Weizhi and Zou Jiancheng. 相似文献
50.
We compute the entropyh
A
(
U
) in the sense of Connes, Narnhofer and Thirring of Bogoliubov automorphisms
U
of the CAR-algebra with respect to invariant quasifree states
A
with 0A1 having pure point spectrum.Supported in part by a grant from the National Science Foundation 相似文献