全文获取类型
收费全文 | 35990篇 |
免费 | 395篇 |
国内免费 | 305篇 |
专业分类
化学 | 16419篇 |
晶体学 | 310篇 |
力学 | 1468篇 |
综合类 | 12篇 |
数学 | 9801篇 |
物理学 | 8680篇 |
出版年
2023年 | 99篇 |
2022年 | 416篇 |
2021年 | 449篇 |
2020年 | 252篇 |
2019年 | 245篇 |
2018年 | 1368篇 |
2017年 | 1598篇 |
2016年 | 1003篇 |
2015年 | 763篇 |
2014年 | 765篇 |
2013年 | 1100篇 |
2012年 | 3591篇 |
2011年 | 2818篇 |
2010年 | 2144篇 |
2009年 | 1796篇 |
2008年 | 996篇 |
2007年 | 1020篇 |
2006年 | 977篇 |
2005年 | 4703篇 |
2004年 | 4145篇 |
2003年 | 2470篇 |
2002年 | 643篇 |
2001年 | 376篇 |
2000年 | 151篇 |
1999年 | 214篇 |
1998年 | 160篇 |
1997年 | 106篇 |
1996年 | 96篇 |
1995年 | 78篇 |
1994年 | 75篇 |
1993年 | 58篇 |
1992年 | 200篇 |
1991年 | 185篇 |
1990年 | 159篇 |
1989年 | 138篇 |
1988年 | 119篇 |
1987年 | 78篇 |
1986年 | 69篇 |
1985年 | 81篇 |
1984年 | 52篇 |
1983年 | 43篇 |
1982年 | 47篇 |
1979年 | 41篇 |
1976年 | 88篇 |
1974年 | 44篇 |
1973年 | 52篇 |
1972年 | 40篇 |
1969年 | 39篇 |
1968年 | 39篇 |
1966年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
P Nürnberg I Barth E Fuhrmann C Lenzner T Losanova C Peters H P?che G Thiel 《Electrophoresis》1991,12(2-3):186-192
Germline and somatic instability of the human genome was studied, using synthetic oligonucleotides specific for simple repeat motifs. The following probes were used: (GTG)5, (GACA)4, (GATA)4, (CT)8, (TTAGGG)3, (GT)8, (GAA)6 and (GGAT)4. Each of them is unique with respect to the target regions recognized in the genome. Thus compilation of the various fingerprint data provides a complex map of the genome (and its deviations). While the fingerprints of differentiated somatic tissues never showed any alterations, in tumor tissues (namely gliomas) many changes could be detected. Most of the latter reflect secondary karyological aberrations. In nearly one third of the gliomas, drastically amplified and apparently monomorphic DNA fragments were identified. This marker should make it possible to deal with causal pathogenetic mechanisms as well as novel diagnostic strategies. 相似文献
72.
73.
F. Cannata J. P. Dedonder L. Le?niak 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(4):451-460
We investigate the origin of the attraction in theK¯K channel around the threshold by introducing an additional channel to theππ andK¯K channels in a separable potential formalism assuming, in general, no direct interaction in theK¯K channel. To reproduce the features of the data, we find that the threshold of the additional channel is much above thef 0(975) meson position. We show that this three-channel problem can be reduced to an effective two-channel problem where thef 0(975) behaves as if it were aK¯K molecule bound by the coupling to the exotic channel. This picture is also supported by the fact that a single pole only, in the complexK¯K momentum plane, is associated to thef 0(975) meson. Various physical observables, like the decay branching ratio and theK¯K scattering length, are then discussed in an effective two-channel framework. 相似文献
74.
Dorota G?azowska Janusz Matkowski 《Journal of Mathematical Analysis and Applications》2007,331(2):1187-1199
The invariance of the geometric mean G with respect to the Lagrangian mean-type mapping (Lf,Lg), i.e. the equation G○(Lf,Lg)=G, is considered. We show that the functions f and g must be of high class regularity. This fact allows to reduce the problem to a differential equation and determine the second derivatives of the generators f and g. 相似文献
75.
In the paper we indicate an error made in the proof of the main result of the paper [M.A. Darwish, On quadratic integral equation of fractional orders, J. Math. Anal. Appl. 311 (2005) 112-119]. Moreover, we provide correct proof of a slightly modified version of the mentioned result. The main tool used in our proof is the technique associated with the Hausdorff measure of noncompactness. 相似文献
76.
Marta Gimnez-Pedrs Ali Aghmiz Carmen Claver Anna M. Masdeu-Bult Denis Sinou 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):157-163
High linear alkenes (1-octene and 1-decene) have been hydroformylated using water-soluble rhodium complexes associated with sulfonated diphosphines in the presence of ionic surfactants or methanol. In all cases, the hydroformylation activities were higher than in experiments without additives. The selectivity in aldehydes was higher when we used cetyltrimethylammonium hydrogensulfate (CTAHSO4) as the surfactant or methanol as the co-solvent. 相似文献
77.
In this paper we deal with nonlinear second-order boundary value problems with impulses. The impulsive functions depend implicitly on the different considered variables and the boundary value conditions are nonlinear. In both cases functional dependence on the solution is allowed. The existence results follow from the existence of a pair of well-ordered lower and upper solutions. 相似文献
78.
79.
We study linear dynamical systems with multidimensional time in Banach spaces. Using Taylor functional calculus we prove that under additional assumptions hyperbolic systems have shadowing property. 相似文献
80.
S?awomir Solecki 《Topology and its Applications》2007,154(12):2462-2464
Let I0 be the σ-ideal of subsets of a Polish group generated by Borel sets which have perfectly many pairwise disjoint translates. We prove that a Fubini-type theorem holds between I0 and the σ-ideals of Haar measure zero sets and of meager sets. We use this result to give a simple proof of a generalization of a theorem of Balcerzak-Ros?anowski-Shelah stating that I0 on N2 strongly violates the countable chain condition. 相似文献