全文获取类型
收费全文 | 233787篇 |
免费 | 2511篇 |
国内免费 | 662篇 |
专业分类
化学 | 125986篇 |
晶体学 | 3601篇 |
力学 | 11022篇 |
综合类 | 10篇 |
数学 | 27186篇 |
物理学 | 69155篇 |
出版年
2021年 | 2370篇 |
2020年 | 2501篇 |
2019年 | 3034篇 |
2018年 | 4016篇 |
2017年 | 4026篇 |
2016年 | 5612篇 |
2015年 | 3043篇 |
2014年 | 5082篇 |
2013年 | 10253篇 |
2012年 | 8624篇 |
2011年 | 10262篇 |
2010年 | 7547篇 |
2009年 | 7597篇 |
2008年 | 9532篇 |
2007年 | 9510篇 |
2006年 | 8569篇 |
2005年 | 7660篇 |
2004年 | 7122篇 |
2003年 | 6449篇 |
2002年 | 6362篇 |
2001年 | 5978篇 |
2000年 | 4512篇 |
1999年 | 3471篇 |
1998年 | 3017篇 |
1997年 | 3094篇 |
1996年 | 2995篇 |
1995年 | 2538篇 |
1994年 | 2604篇 |
1993年 | 2477篇 |
1992年 | 2779篇 |
1991年 | 2868篇 |
1990年 | 2747篇 |
1989年 | 2819篇 |
1988年 | 2753篇 |
1987年 | 2745篇 |
1986年 | 2588篇 |
1985年 | 3368篇 |
1984年 | 3432篇 |
1983年 | 2831篇 |
1982年 | 2866篇 |
1981年 | 2835篇 |
1980年 | 2625篇 |
1979年 | 2978篇 |
1978年 | 2913篇 |
1977年 | 3086篇 |
1976年 | 3070篇 |
1975年 | 2867篇 |
1974年 | 2804篇 |
1973年 | 2912篇 |
1972年 | 2168篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
931.
G. Baldsiefen H. Hübel W. Korten U. J. van Severen J. A. Cizewski N. H. Medina D. R. Napoli C. Rossi Alvarez G. Lo Bianco S. Signorelli 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):337-338
High-spin states in196Pb have been populated using the reaction170Er(30Si,4n). The previously observed shears bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin. 相似文献
932.
Yu. Dryagin N. Scalyga T. Geist 《International Journal of Infrared and Millimeter Waves》1996,17(7):1199-1204
The construction of a notch-filter for 140 GHz with very low passband insertion loss is described. It is based on a single-mode rectangular waveguide and cylindrical cavities matched to it. The typical transmission characteristic is also presented. 相似文献
933.
P. G. Baranov N. G. Romanov A. Hofstaetter A. Scharmann C. Schnorr F. J. Ahlers K. Pierz 《JETP Letters》1996,64(10):754-759
Two types of excitons, localized at opposite interfaces and characterized by different magnitudes of the exchange interactions
at the same radiation energies, are simultaneously in type-II GaAs/AlAs superlattices. It is shown that the additional long-wavelength
luminescence line in superlattices grown with growth interruptions after the GaAs layers is due to the recombination of an
exciton localized at an inverted interface in regions where the quantum-well width is increased by one monolayer.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 701–706 (25 November 1996) 相似文献
934.
935.
C. B?uerle Yu M. Bunkov S. N. Fisher H. Godfrin G. R. Pickett 《Czechoslovak Journal of Physics》1996,46(Z1):5-6
During studies of the impact of single neutrons on superfluid3He at around 100μK we have measured the thermal energy released in the superfluid following the nuclear reaction, n+3He→p+3H+764keV. However, we find that the measured energy deposited in the quasiparticle system shortly after this reaction is substantially
less than what we expect. We believe that this energy deficit represents that energy which has gone into the creation of vortices,
in analogy to the creation of cosmic strings in the early universe via the Kibble mechanism. Furthermore, from the magnitude
of the deficit, we can infer the vortex density which compares favorably with that predicted in Zurek’s scenairo. 相似文献
936.
937.
Diane L. Levesque Eng-Chi Wang Dau-Chang Wei Cherng-Chyi Tzeng Raymond P. Panzica Fardos N. M. Naguib Mahmoud H. El Kouni 《Journal of heterocyclic chemistry》1993,30(5):1399-1404
A new series of potent uridine phosphorylase inhibitors have been prepared from barbituric acid. Among them, 1-[(2-hydroxyethoxy)methyl]-5-)(m--benzyloxy)benzylbarbituric acid ( 37 , BBBA) is the most promising having a Ki value of 1.1 ± 0.2 nM with uridine phosphorylase from human liver. The new inhibitors are easily synthesized and are better inhibitors of human uridine phosphorylase than their uracil counterparts. 相似文献
938.
A quasipotential operator for a system of two scalar particles, and also an integral equation and a normalization condition for the wave function of the connected state, are obtained by the method of two-time Green's functions in an explicitly covariant form. The cases are considered of scalar and electromagnetic interactions of particles of the system.Frantsiska Skoriny Gomel' State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 112–118, June, 1993. 相似文献
939.
L. B. Sjogren H. -X. L. Liu X. -H. Qin C. W. Domier N. C. Luhmann 《International Journal of Infrared and Millimeter Waves》1993,14(6):1201-1216
Device alternatives for millimeter-wave beam control arrays are examined. For the control function, a wide range of semiconductor device as well as bulk material alternatives are considered. In addition, alternatives to the traditional metal strip are considered for the passive electromagnetic array element. This work should provide a broader perspective regarding the choices available for the optimized design of new beam control arrays. 相似文献
940.
The gravitational interaction between grooves machined in a hollow cylindrical mass of uniform density, and an external point mass, is derived in terms of the Associated Legendre functions, and the parametric form of the coupling coefficients is presented. The cross-sections of the grooves, which are regularly spaced in azimuth, are in the form of truncated sectors of the cylinder's end-faces. This theory is applied to the test-masses for the Satellite Test of the Equivalence Principle (STEP) experiment, for which four grooves have been assumed, and an expression for the axialforce is derived which is more than 104 times faster to compute than a Monte-Carlo integration of similar accuracy. Following this analysis it is suggested that the STEP test-masses should carry at least 6 grooves. This theory has wider application to gravitational problems involving general sectored cylindrical bodies. 相似文献