全文获取类型
收费全文 | 381907篇 |
免费 | 2271篇 |
国内免费 | 664篇 |
专业分类
化学 | 180233篇 |
晶体学 | 5669篇 |
力学 | 20949篇 |
综合类 | 10篇 |
数学 | 55319篇 |
物理学 | 122662篇 |
出版年
2020年 | 2805篇 |
2019年 | 3283篇 |
2018年 | 11460篇 |
2017年 | 12127篇 |
2016年 | 9456篇 |
2015年 | 3824篇 |
2014年 | 5612篇 |
2013年 | 12352篇 |
2012年 | 13185篇 |
2011年 | 21747篇 |
2010年 | 14610篇 |
2009年 | 14958篇 |
2008年 | 19574篇 |
2007年 | 22384篇 |
2006年 | 10417篇 |
2005年 | 14136篇 |
2004年 | 11160篇 |
2003年 | 10675篇 |
2002年 | 9143篇 |
2001年 | 9892篇 |
2000年 | 7476篇 |
1999年 | 5542篇 |
1998年 | 4492篇 |
1997年 | 4374篇 |
1996年 | 4233篇 |
1995年 | 3815篇 |
1994年 | 3745篇 |
1993年 | 3595篇 |
1992年 | 4074篇 |
1991年 | 4458篇 |
1990年 | 4220篇 |
1989年 | 4242篇 |
1988年 | 4145篇 |
1987年 | 4160篇 |
1986年 | 3828篇 |
1985年 | 4782篇 |
1984年 | 4832篇 |
1983年 | 4028篇 |
1982年 | 4078篇 |
1981年 | 3849篇 |
1980年 | 3657篇 |
1979年 | 4242篇 |
1978年 | 4436篇 |
1977年 | 4406篇 |
1976年 | 4490篇 |
1975年 | 4166篇 |
1974年 | 4081篇 |
1973年 | 4317篇 |
1972年 | 3188篇 |
1971年 | 2802篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
941.
942.
943.
The dependence of the type of magnetic ordering in multilayer structures on the magnitude of the exchange interaction between
the magnetic layers and on the degree of roughness of the interfaces between the layers is investigated. In the case of a
three-layer system the regions of existence of the domain structure, of noncollinear ordering of the homogeneous magnetic
layers, and of the collinear ferromagnetic phase and collinear antiferromagnetic phase are found.
Fiz. Tverd. Tela (St. Petersburg) 39, 1244–1247 (July 1997) 相似文献
944.
945.
B. I. Sokil 《Ukrainian Mathematical Journal》1997,49(11):1777-1781
On the basis of periodic Ateb functions, in the resonance and nonresonance cases, we construct the asymptotic approximation of one-frequency solutions of a boundary-value problem for a nonlinear nonautonomous equation. 相似文献
946.
947.
948.
I. Nakai 《Commentarii Mathematici Helvetici》1998,73(2):177-205
A curvilinear d-web W = (F
1 , . . . , F
d
) is a configuration of d curvilinear foliations F
i
on a surface. When d = 3, Bott connections of the normal bundles of F
i
extend naturally to equal affine connection, which is called Chern connection. For 3 < d, this is the case if and only if the modulus of tangents to the leaves of F
i
at a point is constant. A d-web is associative if the modulus is constant and weakly associative if Chern connections of all 3-subwebs have equal curvature form. We give a geometric interpretation of the curvature form
in terms of fake billiard in §2, and prove that a weakly associative d-web is associative if Chern connections of triples of the members are non flat, and then the foliations are defined by members
of a pencil (projective linear family of dim 1) of 1-forms. This result completes the classification of weakly associative
4-webs initiated by Poincaré, Mayrhofer and Reidemeister for the flat case. In §4, we generalize the result for n + 2-webs of n-spaces.
Received: September 23, 1996 相似文献
949.
A highly selective solid phase extraction sorbent for pre-concentration of sameridine made by molecular imprinting 总被引:5,自引:0,他引:5
Summary A novel approach to solid phase extraction, based on the use of a highly selective molecularly imprinted polymer, is presented.
The versatility of this type of sorbent for solid phase extraction was demonstrated in a model batch-wise pre-concentration
of sameridine prior to gas chromatography. Problems associated with leakage of remaining imprint molecules during the desorption
phase could be eliminated by the use of a close structural analogue of sameridine as the imprint species. It was found that
a major benefit of the imprinted polymer was its specificity, which lead to distinctly cleaner chromatographic traces and
ability to improve sensitivity by extracting sameridine from larger sample volumes. 相似文献
950.
T. Engel M. Würtz S. Borneis St. Becker I. Klaft A. Kohl T. Kühl F. Laeri D. Marx K. Meier R. Neumann F. Schmitt P. Seelig L. Völker 《Hyperfine Interactions》1997,108(1-3):251-258
Laser spectroscopy at storage rings often suffers from a limited resolution due to Doppler-broadened resonances. Broadening
is caused by the velocity spread of the ions stored in the beam. In the following, the present status of our work on laser
systems specialized on the specific needs of laser spectroscopy at storage rings is reported.
Two pulsed laser systems were developed. One is a dye laser whose spectral bandwidth can be switched by inserting different
Littrow-prisms into the resonator. An increase in bandwidth up to a factor of 45 was achieved. This laser was used for fast
qualitative scans and high resolution measurements. The other laser system is a Nd : YAG laser pumped optical parametric oscillator.
It is a tunable laser system covering the spectral range from 410 to 4000 nm. Furthermore, a continuous wave laser with a
frequency shifted feedback cavity is described. It shows broadband emission with an adjustable bandwidth of up to 4.5 GHz.
This laser can be advantageous for laser cooling of ion beams.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献