全文获取类型
收费全文 | 50745篇 |
免费 | 1988篇 |
国内免费 | 29篇 |
专业分类
化学 | 32133篇 |
晶体学 | 238篇 |
力学 | 1620篇 |
数学 | 7668篇 |
物理学 | 10255篇 |
综合类 | 848篇 |
出版年
2023年 | 381篇 |
2022年 | 313篇 |
2021年 | 522篇 |
2020年 | 693篇 |
2019年 | 643篇 |
2018年 | 1016篇 |
2017年 | 823篇 |
2016年 | 1550篇 |
2015年 | 1411篇 |
2014年 | 1414篇 |
2013年 | 2962篇 |
2012年 | 3481篇 |
2011年 | 3598篇 |
2010年 | 2130篇 |
2009年 | 1722篇 |
2008年 | 3106篇 |
2007年 | 3097篇 |
2006年 | 2745篇 |
2005年 | 2683篇 |
2004年 | 2294篇 |
2003年 | 1855篇 |
2002年 | 1620篇 |
2001年 | 976篇 |
2000年 | 803篇 |
1999年 | 578篇 |
1998年 | 425篇 |
1997年 | 391篇 |
1996年 | 490篇 |
1995年 | 319篇 |
1994年 | 380篇 |
1993年 | 378篇 |
1992年 | 416篇 |
1991年 | 354篇 |
1990年 | 342篇 |
1989年 | 323篇 |
1988年 | 265篇 |
1987年 | 272篇 |
1986年 | 233篇 |
1985年 | 411篇 |
1984年 | 371篇 |
1983年 | 257篇 |
1982年 | 349篇 |
1981年 | 336篇 |
1980年 | 288篇 |
1979年 | 289篇 |
1978年 | 259篇 |
1976年 | 276篇 |
1975年 | 254篇 |
1974年 | 265篇 |
1973年 | 252篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
81.
A. Mahoui J. Lapasset D. G. Sannikov J. Moret P. Saint Grégoire 《Zeitschrift für Physik B Condensed Matter》1995,99(4):543-549
The crystal structure [(C2H5)4N]2CuCl4 has been determined by X-ray diffraction at 243K. The room temperature phase (phase I) belongs to the space group P42/nm [1] whereas the low temperature phase (phase II) is orthorhombic and belongs to the space group Pnna. The phase transition at Tc=258K is of improper ferroelastic type and it is associated with the ordering of the CuCl4 2? and a partial ordering of the [(C2H5)4N]+ ions which are disordered in the high temperature tetragonal phase. At lower temperature, there occurs another instability which could correspond to a complete ordering in the crystal. 相似文献
82.
Details are given of a new method allowing an exact calculation of the spontaneous magnetization in the corner as well as along the edge at an arbitrary distance of the corner for a rectangular planar Ising ferromagnet. 相似文献
83.
F. Grisch P. Bouchardy M. Péalat B. Chanetz T. Pot M. C. Coët 《Applied physics. B, Lasers and optics》1993,56(1):14-20
Rotational temperature and nitrogen number density are measured in the shock wave/boundary layer interaction region in the vicinity of a two-dimensional compression corner disposed in a low pressure, 55 K, Mach 10 hypersonic air flow. Spatially-resolved data are recorded using a nonlinear optical technique named dual-line coherent anti-Stokes Raman scattering (DLCARS). Averaged temperature and density profiles are compared with those predicted by a Navier-Stokes solver. Good agreement is found. 相似文献
84.
G. Principi A. Maddalena Ajay Gupta R. Dal Maschio S. Diré 《Hyperfine Interactions》1992,69(1-4):619-622
Conversion electron Mössbauer spectroscopy (CEMS) has been used to study tin oxide films prepared by sol-gel dipping and sputtering. The spectra of films prepared by sol-gel route result close to that of crystalline SnO2 after heat treatment at a temperature as low as 150°C. The Mössbauer parameters of as sputter deposited films indicate that the structure of the deposited stannic oxide has an amorphous character more pronounced for thinner samples. The structure becomes predominantly that of crystalline SnO2 by heating at 550°C for 30 min provided the film thickness is higher than 10 nm. 相似文献
85.
Summary. This paper introduces and analyzes the convergence properties of a method that computes an approximation to the invariant
subspace associated with a group of eigenvalues of a large not necessarily diagonalizable matrix. The method belongs to the
family of projection type methods. At each step, it refines the approximate invariant subspace using a linearized Riccati's
equation which turns out to be the block analogue of the correction used in the Jacobi-Davidson method. The analysis conducted
in this paper shows that the method converges at a rate quasi-quadratic provided that the approximate invariant subspace is
close to the exact one. The implementation of the method based on multigrid techniques is also discussed and numerical experiments
are reported.
Received June 15, 2000 / Revised version received January 22, 2001 / Published online October 17, 2001 相似文献
86.
Abnormal pattern detected in fragile-X patients by pulsed-field gel electrophoresis. 总被引:26,自引:0,他引:26
The fragile-X syndrome is the most frequent inherited form of mental retardation, with an incidence of 1 in 1,500 males. It is characterized by the presence of a fragile site at Xq27.3 induced in vitro by folate deprivation or by inhibitors of deoxynucleotide synthesis. Its mode of inheritance is unusual for an X-linked trait, with incomplete penetrance in both males and females. Some phenotypically normal males transmit the mutation to all their daughters who rarely express any symptoms, but penetrance is high in sons and daughters of these carrier women. Genetic and physical mapping of the Xq27-q28 region has confirmed that the disease locus is located at or very near the fragile site. Hypotheses proposed to account for the abnormalities in the inheritance of the disease include sequence rearrangements by meiotic recombination or a mutation that affects reactivation of an inactive X chromosome during differentiation of female germ cells. To detect such rearrangements, or methylation changes that may reflect a locally inactive X chromosome, we used pulsed-field gel analysis of DNA from fragile-X patients with probes close to the fragile-X locus. The probe Do33 (DXS465) detected abnormal patterns in fragile-X patients, but not in normal controls or in non-expressing male transmitters. 相似文献
87.
88.
Marcel Erné 《Order》1991,8(2):159-173
We introduce a special type of order-preserving maps between quasiordered sets, the so-called cut-stable maps. These form the largest morphism class such that the corresponding category of quasiordered sets contains the category of complete lattices and complete homomorphisms as a full reflective subcategory, the reflector being given by the Dedekind-MacNeille completion (alias normal completion or completion by cuts). Suitable restriction of the object class leads to the category of separated quasiordered sets and its full reflective subcategory of completely distributive lattices. Similar reflections are obtained for continuous lattices, algebraic lattices, etc. 相似文献
89.
We prove global existence of solutions to the continuous nonhomogeneous Smoluchowski equation for coagulation rates satisfying a more general structure condition than the Galkin–Tupchiev monotony hypothesis considered in (Ph. Laurençot, S. Mischler, Arch. Rational Mech. Anal. 162 (1) (2002) 45–99). The Smoluchowski coagulation rate fulfils this condition as well as some rates which vanish on the diagonal. Under the condition of positivity of the coagulation rate outside of the diagonal we prove that solutions tend to 0 in the large time asymptotic. These results depend on a new estimate from below for the dissipation rate of the Lp-norm, p>1. To cite this article: S. Mischler, M. Rodriguez Ricard, C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献
90.
M. Dubé C. Daneault V. Vuorinen M. Alava M. Rost 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):15-26
We investigate the structure and dynamics of the interface between
two immiscible liquids in a three-dimensional disordered porous
medium. We apply a phase-field model that includes explicitly
disorder and discuss both spontaneous and forced imbibition.
The structure of the interface is dominated by a length scale
ξ× which arises from liquid conservation. We further show
that disorder in the capillary and permeability act on different
length scales and give rise to different scalings and
structures of the interface properties. We conclude with a
range of applications. 相似文献