全文获取类型
收费全文 | 21371篇 |
免费 | 938篇 |
国内免费 | 28篇 |
专业分类
化学 | 12822篇 |
晶体学 | 58篇 |
力学 | 473篇 |
数学 | 2987篇 |
物理学 | 5997篇 |
出版年
2023年 | 179篇 |
2021年 | 222篇 |
2020年 | 323篇 |
2019年 | 246篇 |
2018年 | 257篇 |
2017年 | 237篇 |
2016年 | 619篇 |
2015年 | 578篇 |
2014年 | 558篇 |
2013年 | 1002篇 |
2012年 | 1062篇 |
2011年 | 1257篇 |
2010年 | 611篇 |
2009年 | 550篇 |
2008年 | 1068篇 |
2007年 | 1020篇 |
2006年 | 1024篇 |
2005年 | 894篇 |
2004年 | 716篇 |
2003年 | 634篇 |
2002年 | 603篇 |
2001年 | 505篇 |
2000年 | 407篇 |
1999年 | 329篇 |
1998年 | 272篇 |
1997年 | 304篇 |
1996年 | 292篇 |
1995年 | 271篇 |
1994年 | 237篇 |
1993年 | 277篇 |
1992年 | 259篇 |
1991年 | 205篇 |
1990年 | 172篇 |
1989年 | 167篇 |
1988年 | 144篇 |
1987年 | 169篇 |
1986年 | 172篇 |
1985年 | 190篇 |
1984年 | 224篇 |
1983年 | 201篇 |
1982年 | 200篇 |
1981年 | 217篇 |
1980年 | 183篇 |
1979年 | 177篇 |
1978年 | 195篇 |
1977年 | 185篇 |
1976年 | 160篇 |
1975年 | 148篇 |
1974年 | 159篇 |
1973年 | 148篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Marko D. Mihovilovic Bernhard Müller Markus Spina Arjumand I. Durrani Peter Stanetty Georg Dazinger Karl Kirchner 《Monatshefte für Chemie / Chemical Monthly》2006,137(6):785-794
Summary. Recombinant Escherichia coli overexpressing Pseudomonas sp. NCIMB 9872 cyclopentanone monooxygenase (CPMO, EC 1.14.13.16) and Acinetobacter sp. NCIMB 9871 cyclohexanone monooxygenase (CHMO, EC 1.14.13.22) have been utilized in whole-cell Baeyer-Villiger biotransformations of prochiral bicycloketones. A significant difference in substrate acceptance and stereoselectivity was
observed for bicyclo[3.3.0] and bicyclo[4.3.0] substrates. A plausible mechanism of these transformations was established
by means of high level DFT/B3LYP calculations suggesting an essential difference in electronic requirements for a successful
enzymatic conversion, which was similarly encountered in recombinant whole-cell mediated biooxidations. Some of the lactones
produced in the biocatalytic Baeyer-Villiger oxidation represent key intermediates for the synthesis of indole alkaloids. 相似文献
82.
P. Schwab A. Kochemasov R. Kullmer D. Bäuerle 《Applied Physics A: Materials Science & Processing》1992,54(2):166-169
Pulsed-laser deposition of YBa2Cu3O7 in N2O permits lowering of the substrate temperature with respect to deposition in O2 atmosphere. Additional photodissociation of N2O near the substrate surface deteriorates the superconducting properties of deposited films.On leave from: Institute of Applied Physics of the Academy of Sciences of the USSR, SU-603600 Nishni Nowgorod, USSR 相似文献
83.
In this paper we present photoionization cross sections of the Cu and Al dimers and tetramers. The local spin density method is applied to calculate the electronic structure and the ground state potential. The cross sections are calculated using the continuum multiple scattering method, and a basic analysis of the photoionization process is given within the independent particle picture. 相似文献
84.
Christian R. Noe M. Knollmüller K. Dungler C. Miculka P. Gärtner 《Monatshefte für Chemie / Chemical Monthly》1991,122(8-9):705-718
Summary Acetals3 and4 of alkylthienylcarbinols1 were prepared using an enantiomerically pure lactol2. In the key step these compounds were desulfurized. After deprotection the target compounds7 andent-7 were obtained.
Herrn Prof. Dr. H. Oelschläger zum 70. Geburtstag gewidmet 相似文献
85.
Kazhdan constants relative to conjugacy classes of compact groups are computed. They depend on the nontrivial irreducible characters of the respective group. The result is applied, in particular, to finite groups of Lie type, symmetric groups, and the group SU(n). 相似文献
86.
87.
T. Gleisberg F. Krauss C. G. Papadopoulos A. Schälicke S. Schumann 《The European Physical Journal C - Particles and Fields》2004,34(2):173-180
In this paper total cross sections for signals and backgrounds of top- and Higgs-production channels in e + e- collisions at a future linear collider are presented. All channels considered are characterized by the emergence of six-particle final states. The calculation takes into account the full set of tree-level amplitudes in each process. Two multi-purpose parton level generators, HELAC/PHEGAS and AMEGIC + + , are used, and their results are found to be in perfect agreement.Received: 26 November 2003, Revised: 15 January 2004, Published online: 3 March 2004 相似文献
88.
Experimental Techniques - 相似文献
89.
Markus Kirkilionis 《Journal of Mathematical Analysis and Applications》2004,299(1):157-173
We state and prove general comparison principles for ordinary differential equations, discuss the scope of these principles, and present examples. 相似文献
90.
Daniel E. Vogler Ana Lorencak Julien M. Rey Markus W. Sigrist 《Optics and Lasers in Engineering》2005,43(3-5):527
A novel sensitive technique for the determination of losses in fiber cavities is presented. The method is based on the cavity ringdown scheme implemented in silica-based single-mode fibers. Bending losses of fiber cavities of different lengths have been measured showing all an oscillating behavior with respect to the curvature radius of the fiber as predicted by a theoretical model. The best minimum detectable absorbance per cavity pass achieved by this new method is 1.72×10−3 dB within a 10 m-long cavity. This limit suffices well for an accurate determination of optical bending losses even in bend-insensitive fibers. Furthermore, the comparison of the measured bending losses with a theoretical model allows the extraction of different fiber parameters. Good agreement has been found between the experimentally derived parameters and literature data. 相似文献