全文获取类型
收费全文 | 2310篇 |
免费 | 43篇 |
国内免费 | 11篇 |
专业分类
化学 | 1481篇 |
晶体学 | 22篇 |
力学 | 106篇 |
数学 | 327篇 |
物理学 | 428篇 |
出版年
2023年 | 18篇 |
2022年 | 26篇 |
2021年 | 45篇 |
2020年 | 37篇 |
2019年 | 29篇 |
2018年 | 36篇 |
2017年 | 27篇 |
2016年 | 46篇 |
2015年 | 50篇 |
2014年 | 58篇 |
2013年 | 131篇 |
2012年 | 117篇 |
2011年 | 164篇 |
2010年 | 89篇 |
2009年 | 83篇 |
2008年 | 137篇 |
2007年 | 128篇 |
2006年 | 122篇 |
2005年 | 113篇 |
2004年 | 101篇 |
2003年 | 81篇 |
2002年 | 94篇 |
2001年 | 36篇 |
2000年 | 35篇 |
1999年 | 23篇 |
1998年 | 23篇 |
1997年 | 26篇 |
1996年 | 36篇 |
1995年 | 30篇 |
1994年 | 27篇 |
1993年 | 26篇 |
1992年 | 9篇 |
1991年 | 19篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 22篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 22篇 |
1984年 | 24篇 |
1983年 | 22篇 |
1982年 | 15篇 |
1981年 | 17篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 21篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1973年 | 8篇 |
排序方式: 共有2364条查询结果,搜索用时 968 毫秒
151.
Gain-guided diode lasers usually have emission wavelengths determined by the manufacturing process, with typically 0.5-1-nm bandwidth. Furthermore, their beam quality is rather poor. We show that external cavities allow for tunable narrow-bandwidth operation of gain-guided diode lasers. At the same time the beam quality is drastically improved; almost diffraction-limited light of more than 200 mW has been achieved over the whole tuning range from 910 to 942 nm with narrow bandwidth. 相似文献
152.
R. Lo Franco G. Compagno A. Messina A. Napoli 《The European physical journal. Special topics》2008,160(1):247-257
We show that the N-photon generalized binomial states of electromagnetic field may be put in a bijective mapping with the
coherent atomic states of N two-level atoms. We exploit this correspondence to simply obtain both known and new properties
of the N-photon generalized binomial states. In particular, an over-complete basis of these binomial states and an orthonormal
basis are obtained. Finally, the squeezing properties of generalized binomial state are analyzed. 相似文献
153.
We report on a novel technique to compensate for all-order polarization-mode dispersion. By means of this technique, based on a suitable combination of phase modulation and group-velocity dispersion, we compensated for as much as 60 ps of differential group delay that affected a 10-Gbit/s return-to-zero data stream. 相似文献
154.
In this paper, we show a unified approach to the problem of characterizing general distribution functions based on the conditional expectation between adjacent order statistics, or , where is a real, continuous and strictly monotonic function. We have the explicit expression of the distribution function from the above order mean function, and , and we give necessary and sufficient conditions so that any real function can be an order mean function. Our results generalize the results given for the discrete, absolutely continuous and continuous cases. Further, we show stability theorems for these characterizations.
155.
Davide Franco 《Annali di Matematica Pura ed Applicata》1996,170(1):133-145
Sunto
Si analizzano delle condizioni per l'annullamento della coomologia di fibrati stabili di rango 2su
P
3.Dopo i primi risultati di annullamento dovuti principalmente ad Hartshorne, Chang congetturò che alcune disuguaglianze sulle, classi di Chern fossero sufficienti per l'annullamento del primo gruppo di coomologia. La congettura finora è provata solo in alcuni casi particolari. Nel lavoro si dimostra la congettura in molti altri casi. In particolare si completano alcuni risultati recenti dovuti ad Ellia affrontando il caso in cui la prima classe di Chern è dispari. 相似文献
156.
157.
Witold Lipski Franco P Preparata 《Journal of Algorithms in Cognition, Informatics and Logic》1980,1(3):235-246
Let R1,…,Rm be rectangles on the plane with sides parallel to the coordinate axes. An algorithm is described for finding the contour of F = R1 ∪ … ∪ Rm in time, where p is the number of edges in the contour. This is O(m2) in the general case, and O(m log m) when F is without holes (then p ≤ 8m ? 4); both of these performances are optimal. 相似文献
158.
In this paper we study the conditions to be satisfied in order to use a N-pole truncation to the continued-frac ion expansion. We show the correct way to do the cut off and apply the result to analyse experimental data for the one-dimensional antiferromagnet TMMC, at low temperatures. 相似文献
159.
160.
[reaction: see text] 4-Methyl-5-alkyl-2(5H)-furanones have been prepared by ruthenium-catalyzed ring-closing metathesis of the suitable methallyl acrylates. Despite the electron deficiency of the conjugated double bond and of the gem-disubstitution of the allylic alkene moiety in the starting acrylates, the first-generation Grubbs' catalyst I proved to be an effective promoter for the ring closure, affording the expected butenolides in good to high yields. 相似文献