全文获取类型
收费全文 | 15310篇 |
免费 | 499篇 |
国内免费 | 328篇 |
专业分类
化学 | 9539篇 |
晶体学 | 97篇 |
力学 | 441篇 |
综合类 | 30篇 |
数学 | 2062篇 |
物理学 | 3968篇 |
出版年
2021年 | 218篇 |
2020年 | 200篇 |
2019年 | 193篇 |
2018年 | 186篇 |
2017年 | 161篇 |
2016年 | 373篇 |
2015年 | 336篇 |
2014年 | 405篇 |
2013年 | 829篇 |
2012年 | 673篇 |
2011年 | 788篇 |
2010年 | 543篇 |
2009年 | 525篇 |
2008年 | 721篇 |
2007年 | 761篇 |
2006年 | 636篇 |
2005年 | 631篇 |
2004年 | 615篇 |
2003年 | 607篇 |
2002年 | 646篇 |
2001年 | 455篇 |
2000年 | 413篇 |
1999年 | 320篇 |
1998年 | 235篇 |
1997年 | 205篇 |
1996年 | 198篇 |
1995年 | 237篇 |
1994年 | 221篇 |
1993年 | 177篇 |
1992年 | 170篇 |
1991年 | 175篇 |
1990年 | 189篇 |
1989年 | 157篇 |
1988年 | 136篇 |
1987年 | 137篇 |
1986年 | 125篇 |
1985年 | 219篇 |
1984年 | 238篇 |
1983年 | 161篇 |
1982年 | 178篇 |
1981年 | 152篇 |
1980年 | 162篇 |
1979年 | 145篇 |
1978年 | 118篇 |
1977年 | 167篇 |
1976年 | 148篇 |
1975年 | 120篇 |
1974年 | 114篇 |
1973年 | 114篇 |
1972年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 712 毫秒
991.
We developed a constituent quark-diquark model for the nucleon and its resonances using a harmonic oscillator potential for
the interaction. The effects due to relativistic kinetic energy correction are studied. Finally, charge form factor of the
model is calculated and compared with experimental data.
相似文献
992.
993.
A. De Roeck A. Katre P. Mermod D. Milstead T. Sloan 《The European Physical Journal C - Particles and Fields》2012,72(4):1985
The experiments at the Large Hadron Collider (LHC) are able to discover or set limits on the production of exotic particles
with TeV-scale masses possessing values of electric and/or magnetic charge such that they behave as highly ionising particles
(HIPs). In this paper the sensitivity of the LHC experiments to HIP production is discussed in detail. It is shown that a
number of different detection methods are required to investigate as fully as possible the charge-mass range. These include
direct detection as the HIPs pass through either passive or active detectors and, in the case of magnetically charged objects,
the so-called induction method with which magnetic monopoles which stop in accelerator and detector material could be observed.
The benefit of using complementary approaches to HIP detection is discussed. 相似文献
994.
995.
Jesús A. De Loera Bernd Sturmfels Cynthia Vinzant 《Foundations of Computational Mathematics》2012,12(4):509-540
The central curve of a linear program is an algebraic curve specified by linear and quadratic constraints arising from complementary slackness. It is the union of the various central paths for minimizing or maximizing the cost function over any region in the associated hyperplane arrangement. We determine the degree, arithmetic genus and defining prime ideal of the central curve, thereby answering a question of Bayer and Lagarias. These invariants, along with the degree of the Gauss image of the curve, are expressed in terms of the matroid of the input matrix. Extending work of Dedieu, Malajovich and Shub, this yields an instance-specific bound on the total curvature of the central path, a quantity relevant for interior-point methods. The global geometry of central curves is studied in detail. 相似文献
996.
Darwin P. R. Kint Antxon Martínez De Ilarduya Sebastin Muoz‐Guerra 《Journal of Polymer Science.Polymer Physics》2001,39(13):1553-1564
The microstructure and crystallization behavior of a set of poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers (PETNI) containing 5‐nitroisophthalic units in the 10–50 mol % range were examined and compared to those of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate‐co‐isophthalate) (PETI) copolymers. A 13C NMR analysis of PETNI copolymers in a trifluoroacetic acid solution indicates that they are random copolymers with average sequence lengths in accordance with ideal polycondensation statistics. Differential scanning calorimetry (DSC) studies show that PETNI containing 5‐nitroisophthalic units up to 20 mol % are able to crystallize and that crystallization takes place in these copolymers at much slower rates than in PET. Wide‐angle X‐ray diffraction from powder and fibers reveals that crystallizable PETNI adopts the same triclinic crystal structure as PET, with the nitroisophthalate units being excluded from crystallites. Fourier transform infrared in combination with cross‐polarization/magic‐angle spinning 13C NMR spectroscopy demonstrates the occurrence of a gauche–trans conversion encompassing the crystallization process. A correlation between DSC and spectroscopic data leads us to conclude that the content of trans conformer in the noncrystallized phase of PETNI is higher than in both PET and PETI copolymers and suggests that secondary crystallization in the homopolymer must proceed by a mechanism different than that in copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1553–1564, 2001 相似文献
997.
998.
G. Spavieri V. Guerra R. De Abreu G. T. Gillies 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):457-463
Propagation of Aharonov-Bohm matter waves and light waves in moving media is
characterized by the interaction electromagnetic momentum. Thus, recent
models of light propagation in moving rarefied media justify and call for an optical experiment of the Mascart-Jamin type,
capable of testing the
modern interpretations of ether drift experiments. 相似文献
999.
H. E. Roman A. Celi G. De Filippi 《The European physical journal. Special topics》2008,161(1):195-205
We study long-term behaviour of air temperature, wave heights and wind speed time
series recorded for the period 1993–1997 at a meteo-marine station located in the
Adriatic Sea. The scaling analysis shows that fluctuations of air temperature
display long-range autocorrelations, while those for wave heights show a more complex
behaviour, crossing over from a persistent regime at intermediate time scales (up
to about 20 days) to an anti-persistence behaviour at longer times. Furthermore,
the crosscorrelations of their records are found to be large, with a covariance
of about -0.3 (indicating anti-crosscorrelations) within the full 5-years period,
giving a quantitative measure of the actual coupling between the two data sets. Wind
speed fluctuations are found to be strongly crosscorrelated (about 0.6) with those
of wave heights, indicating as expected that wind is the main driving force for wave
height fluctuations. 相似文献
1000.
Riccardo Ghiloni 《Proceedings of the American Mathematical Society》2002,130(12):3525-3535
For each compact smooth manifold containing at least two points we prove the existence of a compact nonsingular algebraic set and a smooth map such that, for every rational diffeomorphism and for every diffeomorphism where and are compact nonsingular algebraic sets, we may fix a neighborhood of in which does not contain any regular rational map. Furthermore is not homotopic to any regular rational map. Bearing in mind the case in which is a compact nonsingular algebraic set with totally algebraic homology, the previous result establishes a clear distinction between the property of a smooth map to represent an algebraic unoriented bordism class and the property of to be homotopic to a regular rational map. Furthermore we have: every compact Nash submanifold of containing at least two points has not any tubular neighborhood with rational retraction.