全文获取类型
收费全文 | 90946篇 |
免费 | 3269篇 |
国内免费 | 219篇 |
专业分类
化学 | 59207篇 |
晶体学 | 537篇 |
力学 | 2324篇 |
综合类 | 4篇 |
数学 | 14405篇 |
物理学 | 17957篇 |
出版年
2023年 | 646篇 |
2022年 | 778篇 |
2021年 | 1331篇 |
2020年 | 1395篇 |
2019年 | 1377篇 |
2018年 | 1794篇 |
2017年 | 1548篇 |
2016年 | 2969篇 |
2015年 | 2566篇 |
2014年 | 2684篇 |
2013年 | 5485篇 |
2012年 | 6020篇 |
2011年 | 6416篇 |
2010年 | 3985篇 |
2009年 | 3473篇 |
2008年 | 5532篇 |
2007年 | 5477篇 |
2006年 | 4885篇 |
2005年 | 4591篇 |
2004年 | 3822篇 |
2003年 | 3082篇 |
2002年 | 2718篇 |
2001年 | 1806篇 |
2000年 | 1555篇 |
1999年 | 1186篇 |
1998年 | 906篇 |
1997年 | 814篇 |
1996年 | 1009篇 |
1995年 | 693篇 |
1994年 | 735篇 |
1993年 | 752篇 |
1992年 | 758篇 |
1991年 | 613篇 |
1990年 | 582篇 |
1989年 | 526篇 |
1988年 | 466篇 |
1987年 | 466篇 |
1986年 | 423篇 |
1985年 | 650篇 |
1984年 | 602篇 |
1983年 | 433篇 |
1982年 | 525篇 |
1981年 | 477篇 |
1980年 | 425篇 |
1979年 | 409篇 |
1978年 | 378篇 |
1976年 | 378篇 |
1975年 | 342篇 |
1974年 | 320篇 |
1973年 | 353篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
231.
Girard V Farrenq R Sorokin E Sorokina IT Guelachvili G Picqué N 《Chemical physics letters》2006,419(4-6):584-588
The spectral dynamics of a mid-infrared multimode Cr(2+):ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C(2)H(2) in natural isotopic abundance are recorded around 4000 cm(-1) with kilometric absorption path lengths and sensitivities better than 3 10(-8) cm(-1). Two cold bands are newly identified and assigned to the ν(1)+ν(4) (1) and ν(3)+ν(5) (1) transitions of (12)C(13)CH(2). The ν(1)+ν(5) (1) band of (12)C(2)HD and fourteen (12)C(2)H(2) bands are observed, among which for the first time ν(2)+2ν(4) (2)+ν(5) (-1). 相似文献
232.
Bubble pressure points of ethanol–1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea refrigerant) mixtures from the third Industrial Fluid Properties Simulation Challenge are computed using publicly available molecular simulation software. Several published force fields are compared against the known answers provided in the contest guidelines and the best force fields are used to make predictions for the unknown results. 相似文献
233.
234.
J. J. EGOZCUE J. L. DIAZ-BARRERO V. PAWLOWSKY-GLAHN 《数学学报(英文版)》2006,22(4):1175-1182
The set of probability functions is a convex subset of L1 and it does not have a linear space structure when using ordinary sum and multiplication by real constants. Moreover, difficulties arise when dealing with distances between densities. The crucial point is that usual distances are not invariant under relevant transformations of densities. To overcome these limitations, Aitchison's ideas on compositional data analysis are used, generalizing perturbation and power transformation, as well as the Aitchison inner product, to operations on probability density functions with support on a finite interval. With these operations at hand, it is shown that the set of bounded probability density functions on finite intervals is a pre-Hilbert space. A Hilbert space of densities, whose logarithm is square-integrable, is obtained as the natural completion of the pre-Hilbert space. 相似文献
235.
236.
Generally, in homotopy theory a cylinder object (or, its dual, a path object) is used to define homotopy between morphisms,
and a cone object is used to build exact sequences of homotopy groups. Here, an axiomatic theory based on a cone functor is
given. Suspension objects are associated to based objects and cofibrations, obtaining homotopy groups referred to an object
and relative to a cofibration, respectively. Exact sequences of these groups are built. Algebraic and particular examples
are given. We point out that the main results of this paper were already stated in [3], and the purpose of this article is
to give full details of the foregoing. 相似文献
237.
Rogério S. Mol 《Bulletin of the Brazilian Mathematical Society》2006,37(1):29-48
Résumé. Nous définissons des classes polaires associées à une distribution holomorphe singulière de sous-espaces tangents d’une variété
projective lisse. Nous prouvons que ces classes polaires peuvent être calculées en fonction des classes de Chern-Mather du
faisceau tangent de la distribution et réciproquement. Nous utilisons leurs degrés pour borner les degrés de certaines classes
polaires associés à une variété invariante.
*Ce travail a été soutenu par l’Accord de Coopération France-Brésil (CNRS/CNPq) et par la Fondation CAPES-Brésil. 相似文献
238.
E. Liénard G. Ban J. Blieck D. Durand F. Duval X. Fléchard M. Herbane M. Labalme Y. Lemière F. Mauger A. Méry O. Naviliat-Cuncic D. Rodríguez J. C. Thomas 《Hyperfine Interactions》2006,172(1-3):29-33
We report on the status of the LPCTrap experiment, devoted to measure the β–ν angular correlation in the pure Gamow–Teller
decay of 6He. This measurement is motivated by the search for the presence of tensor type contributions to the weak interaction. The
6He ions are confined in a novel transparent Paul trap. The β particles and the recoil ions are detected in coincidence to
deduce the angular correlation parameter. The commissioning run performed in 2005 has given the proof of principle of this
experiment. Up to 105 coincidences were recorded during a second run in 2006. 相似文献
239.
Summary The gas chromatographic behaviour of crosslinked macroporous 2-hydroxyethyl methacrylate grafted with 2-methyloxazoline was
investigated and the range of applicability of the copolymer was assessed. Retention index values were measured on this copolymer
and compared with those obtained on the terpolymer 2-hydroxyethyl methacrylate-ethylene dimethacrylate-acrylonitrile. Rohrschneider
constants and efficiency data for selected sorbates are given. The use of this type of polymer in the separation of various
types of compounds is documented by various examples. 相似文献
240.