全文获取类型
收费全文 | 430484篇 |
免费 | 4217篇 |
国内免费 | 1193篇 |
专业分类
化学 | 234111篇 |
晶体学 | 6823篇 |
力学 | 18853篇 |
综合类 | 13篇 |
数学 | 46158篇 |
物理学 | 129936篇 |
出版年
2018年 | 4190篇 |
2017年 | 4156篇 |
2016年 | 6430篇 |
2015年 | 4140篇 |
2014年 | 6354篇 |
2013年 | 17399篇 |
2012年 | 12490篇 |
2011年 | 15415篇 |
2010年 | 10840篇 |
2009年 | 10600篇 |
2008年 | 14283篇 |
2007年 | 14618篇 |
2006年 | 13758篇 |
2005年 | 12456篇 |
2004年 | 11400篇 |
2003年 | 10371篇 |
2002年 | 10205篇 |
2001年 | 12035篇 |
2000年 | 9275篇 |
1999年 | 7282篇 |
1998年 | 6113篇 |
1997年 | 6140篇 |
1996年 | 5857篇 |
1995年 | 5436篇 |
1994年 | 5449篇 |
1993年 | 5104篇 |
1992年 | 6000篇 |
1991年 | 5874篇 |
1990年 | 5772篇 |
1989年 | 5657篇 |
1988年 | 5731篇 |
1987年 | 5618篇 |
1986年 | 5292篇 |
1985年 | 7052篇 |
1984年 | 7295篇 |
1983年 | 6065篇 |
1982年 | 6374篇 |
1981年 | 6269篇 |
1980年 | 6137篇 |
1979年 | 6312篇 |
1978年 | 6771篇 |
1977年 | 6527篇 |
1976年 | 6543篇 |
1975年 | 6117篇 |
1974年 | 6158篇 |
1973年 | 6286篇 |
1972年 | 4376篇 |
1971年 | 3644篇 |
1968年 | 3781篇 |
1967年 | 3975篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
J. Urban H. Sack-Kongehl K. Weiss 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,36(1):73-83
Structure and reactivity with oxigen of Cu clusters in the size range of 4.5±2.5 nm created by the inert gas aggregation technique were studied by HREM. The pure Cu clusters investigated under clean conditions show the structures of MTP's with a small lattice dilatation of the (111) plane of 1.25%. For icosahedral and decahedral particles this dilatation corresponds to a splitting of the nearest neighbour distance showing two different values, i.e. dilatation of 2.2% and contraction of 2.8% for the two edges of the deformed tetrahedral subunits, respectively. Oxidation at room temperature and air pressure of 1 bar only begins after a few minutes of exposure to air, after having undergone creation of probably non-stoichiometric intermediate states in the cuprite Cu2O structure with the bulk values of the bond lengths. 相似文献
992.
Institute of Biology, Ufa Scientific Center, Russian Academy of Sciences, Ufa, fax (3472) 35 6103. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 755-756, September-October, 1995. Original article submitted September 6, 1994. 相似文献
993.
A. Mahoui J. Lapasset D. G. Sannikov J. Moret P. Saint Grégoire 《Zeitschrift für Physik B Condensed Matter》1995,99(4):543-549
The crystal structure [(C2H5)4N]2CuCl4 has been determined by X-ray diffraction at 243K. The room temperature phase (phase I) belongs to the space group P42/nm [1] whereas the low temperature phase (phase II) is orthorhombic and belongs to the space group Pnna. The phase transition at Tc=258K is of improper ferroelastic type and it is associated with the ordering of the CuCl4 2? and a partial ordering of the [(C2H5)4N]+ ions which are disordered in the high temperature tetragonal phase. At lower temperature, there occurs another instability which could correspond to a complete ordering in the crystal. 相似文献
994.
The temperature dependence of the NMR chemical shift of129Xe dissolved in liquid alkanes is examined in the context of the reaction field model. An essential feature of the theory is the inclusion of the temperature dependence of the density of thesolvent. The theory of free volume for liquids is incorporated into the reaction field model to account for this temperature dependence. Comparison of the theory with previously reported measurements indicates the sensitivity of the129Xe chemical shift to the free volume of liquids. Incorporation of free volume improves the agreement between measurement and theory for branched alkane solvents, and resolves the origin of the 62 ppm intercept in the plot of reaction field as a function of129Xe chemical shift for the n-alkanes. 相似文献
995.
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
996.
997.
S. E. Kubatkin A. Ya. Tzalenchuk Z. G. Ivanov P. Delsing R. I. Shekhter T. Claeson 《JETP Letters》1996,63(2):126-132
We report on a successful attempt to fabricate a Coulomb blockade electrometer consisting of an ultrasmall YBa2Cu3O7−δ (YBCO) island coupled to two gold electrodes through a high-resistance native surface tunnel barrier. A third electrode placed
near the island was used as an electrostatic gate. Spectra typical for tunneling into the YBCO superconductor were reproducibly
measured. At temperatures below 0.5 K the low-bias conductance was suppressed by the Coulomb blockade. The blockade could
be periodically varied by the gate potential. An external magnetic field of up to 5 T strongly influenced the transport via
the island but without any change in the period of the Coulomb oscillations.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 112–117 (25 January 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
998.
999.
1000.
L. J. Yamí n S. E. Blanco J. M. Luco F. H. Ferretti 《Journal of Molecular Structure》1997,390(1-3):209-215
The isomerization mechanism of 2′(OH)chalcone (1) in flavanone (2) was studied. The calculations were performed with the semiempirical method AM1, using totally optimized molecular geometries. A 6-step mechanism including several equilibrium states was proposed. It was concluded that: (a) At the conformational equilibrium of 1 there could be 43.9% of s-cis conformer; (b) The acid dissociation of 1 trans-s-trans is considerable; (c) The EE, ΔHf and net charges show that the rotation of ring A of 1 and the formation of ring C of 2 occurs without greater impairments; (d) Although the keto structure is the most stable one, the enolate of 2 is present in the reaction medium; (e) The conversion of enol of 2 in the keto form would be the limiting step of the analyzed isomerization rate. 相似文献