全文获取类型
收费全文 | 366549篇 |
免费 | 8330篇 |
国内免费 | 4113篇 |
专业分类
化学 | 182811篇 |
晶体学 | 5322篇 |
力学 | 18264篇 |
综合类 | 138篇 |
数学 | 53507篇 |
物理学 | 118950篇 |
出版年
2021年 | 2709篇 |
2020年 | 3128篇 |
2019年 | 3360篇 |
2018年 | 12066篇 |
2017年 | 12743篇 |
2016年 | 9304篇 |
2015年 | 4851篇 |
2014年 | 5861篇 |
2013年 | 13540篇 |
2012年 | 14987篇 |
2011年 | 24896篇 |
2010年 | 15333篇 |
2009年 | 15226篇 |
2008年 | 21200篇 |
2007年 | 24493篇 |
2006年 | 10129篇 |
2005年 | 15857篇 |
2004年 | 11348篇 |
2003年 | 10266篇 |
2002年 | 8236篇 |
2001年 | 7906篇 |
2000年 | 6109篇 |
1999年 | 4825篇 |
1998年 | 4097篇 |
1997年 | 4078篇 |
1996年 | 3940篇 |
1995年 | 3650篇 |
1994年 | 3367篇 |
1993年 | 3342篇 |
1992年 | 3629篇 |
1991年 | 3620篇 |
1990年 | 3407篇 |
1989年 | 3317篇 |
1988年 | 3335篇 |
1987年 | 3186篇 |
1986年 | 3100篇 |
1985年 | 4135篇 |
1984年 | 4277篇 |
1983年 | 3519篇 |
1982年 | 3855篇 |
1981年 | 3742篇 |
1980年 | 3601篇 |
1979年 | 3645篇 |
1978年 | 3882篇 |
1977年 | 3627篇 |
1976年 | 3865篇 |
1975年 | 3436篇 |
1974年 | 3555篇 |
1973年 | 3898篇 |
1972年 | 2336篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Editorial: Metal-Enhanced Fluorescence 总被引:1,自引:0,他引:1
992.
M. M. Zaripov V. F. Tarasov V. A. Ulanov G. S. Shakurov 《Physics of the Solid State》2002,44(11):2050-2054
The bivalent chromium impurity centers in CdF2 and CaF2 crystals are investigated using electron paramagnetic resonance (EPR) in the frequency range 9.3–300 GHz. It is found that Cr2+ ions in the lattices of these crystals occupy cation positions and form [CrF4F4]6? clusters whose magnetic properties at low temperatures are characterized by orthorhombic symmetry. The parameters of the electron Zeeman and ligand interactions of the Cr2+ ion with four fluorine ions in the nearest environment are determined. The initial splittings in the system of spin energy levels of the cluster are measured. 相似文献
993.
Electronic properties of model quantum-dot structures in zero and finite magnetic fields 总被引:1,自引:0,他引:1
H. Saarikoski E. Räsänen S. Siljamäki A. Harju M.J. Puska R.M. Nieminen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):241-252
We have computed electronic structures and total energies of circularly confined two-dimensional quantum dots and their lateral
dimers in zero and finite uniform external magnetic fields using different theoretical schemes: the spin-density-functional
theory (SDFT), the current-and-spin-density-functional theory (CSDFT), and the variational quantum Monte Carlo (VMC) method.
The SDFT and CSDFT calculations employ a recently-developed, symmetry-unrestricted real-space algorithm allowing solutions
which break the spin symmetry. Results obtained for a six-electron dot in the weak confinement limit and in zero magnetic
field as well as in a moderate confinement and in finite magnetic fields enable us to draw conclusions about the reliability
of the more approximative SDFT and CSDFT schemes in comparison with the VMC method. The same is true for results obtained
for the two-electron quantum dot dimer as a function of inter-dot distance. The structure and role of the symmetry-breaking
solutions appearing in the SDFT and CSDFT calculations for the above systems are discussed.
Received 16 October 2001 and Received in final form 17 January 2002 相似文献
994.
R. A. Kotel’nikova G. N. Bogdanov G. V. Zotina V. S. Romanova Z. N. Parnes 《Physics of the Solid State》2002,44(3):576-577
Efficient quenching of eosin phosphorescence by amino-acid derivatives of fullerene (AADFs) such as C60-alanine and C60-glycine in aqueous solutions indicates the possibility of transferring electrons from eosin to fullerene upon collisions or in the exciplex state. To investigate electron transfer in the protein structure, we studied the process of incorporation of C60-alanine and C60-glycine into the heme pocket of myoglobin by controlling Förster quenching. The dissociation constant for the protein-AADF complex was estimated. 相似文献
995.
V. I. Strunin A. A. Lyakhov G. Zh. Khudaibergenov V. V. Shkurkin 《Technical Physics》2002,47(6):760-766
A model of silane decomposition in a radio-frequency argon plasma is constructed. The concentrations of SiH4 decomposition products, as well as products of synthesis (higher silanes), are calculated. The role of metastable argon atoms in the formation of SiH3 radicals and the higher silanes is analyzed. 相似文献
996.
997.
Several variations of two-dimensional (workers x jobs) and three-dimensional (workers x jobs x machines) time- as well as cost-minimizing assignment problems, which arise owing to (i) precedence relations of some form among the jobs or (ii) capacity restrictions on workers/machines imposed by the requirement that the surplus resources have to be fully employed, have been considered in the literature. In this paper, an algorithm is presented for time-cost trade-off analysis which is applicable to any general pair of such constrained problems. The algorithm is also illustrated by a numerical example. 相似文献
998.
This note discusses the need to use various data-compaction schemes in the implementation of sophisticated large-scale linear programming codes on modest personal computers. It demonstrates a method whereby the overhead of using these schemes is significantly reduced on Intel 80 x 86 processors. 相似文献
999.
The optimal return function for a Borel measurable gambling problem with a bounded utility function was shown by Strauch (1967)
to be universally measurable when the problem is leavable in the sense that the gambler may terminate play at any time. The
same is shown here for the more general class of nonleavable problems.
Research supported by National Science Foundation Grant DMS-8801085. 相似文献
1000.
Abhandlungen aus dem Mathematischen Seminar der Universität Hamburg - 相似文献