全文获取类型
收费全文 | 142780篇 |
免费 | 9945篇 |
国内免费 | 16243篇 |
专业分类
化学 | 77893篇 |
晶体学 | 1388篇 |
力学 | 3199篇 |
综合类 | 925篇 |
数学 | 13571篇 |
物理学 | 32222篇 |
综合类 | 39770篇 |
出版年
2024年 | 184篇 |
2023年 | 1027篇 |
2022年 | 2382篇 |
2021年 | 2771篇 |
2020年 | 3180篇 |
2019年 | 3150篇 |
2018年 | 2885篇 |
2017年 | 4009篇 |
2016年 | 4403篇 |
2015年 | 4235篇 |
2014年 | 5544篇 |
2013年 | 9213篇 |
2012年 | 9226篇 |
2011年 | 8347篇 |
2010年 | 6604篇 |
2009年 | 8457篇 |
2008年 | 8914篇 |
2007年 | 10279篇 |
2006年 | 9413篇 |
2005年 | 8080篇 |
2004年 | 7506篇 |
2003年 | 6218篇 |
2002年 | 7109篇 |
2001年 | 4685篇 |
2000年 | 4328篇 |
1999年 | 3897篇 |
1998年 | 3264篇 |
1997年 | 2718篇 |
1996年 | 2375篇 |
1995年 | 2199篇 |
1994年 | 1959篇 |
1993年 | 1662篇 |
1992年 | 1523篇 |
1991年 | 1207篇 |
1990年 | 991篇 |
1989年 | 960篇 |
1988年 | 734篇 |
1987年 | 548篇 |
1986年 | 409篇 |
1985年 | 313篇 |
1984年 | 301篇 |
1983年 | 164篇 |
1982年 | 253篇 |
1981年 | 213篇 |
1980年 | 211篇 |
1979年 | 199篇 |
1978年 | 184篇 |
1977年 | 128篇 |
1976年 | 119篇 |
1973年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 720 毫秒
131.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
132.
The theory of free-carrier absorption (FCA) is developed, in the extreme quantum limit when the carriers are assumed to populate
only the lowest quantized energy level, for quasi-two and one-dimensional semiconducting quantum well structures where the
carriers are scattered by ionized impurities. The radiation field is assumed to be polarized in the plane of the layer in
the quasi-two-dimensional case and along the length of the wire in the quasi-one-dimensional case. Expressions for FCA are
obtained for the cases where the impurities are either in the well (background impurities) or outside the well (remote impurities).
Variation of FCA is numerically studied with photon frequency and well width. 相似文献
133.
Summary In 1980 Dahmen-DeVore-Scherer introduced a modulus of continuity which turns out to reflect invariance properties of compound cubature rules effectively. Accordingly, sharp error bounds are derived, the existence of relevant counterexamples being a consequence of a quantitative resonance principle, established previously. 相似文献
134.
相对论性无自旋粒子在Hartmann势场中运动的精确解 总被引:1,自引:1,他引:0
在标量势等于矢量势的条件下,本文获得了具有Hartmann型势的Klein-Gordon方程的精确解.给出了束缚态的精确的能谱方程和归一化的径向波函数,对于散射态,获得了按“k/2π标度”归一化的径向波函数和相移的解析计算公式.讨论了散射振幅的解析性质和波函数、能谱方程以及相移的非相对论近似. 相似文献
135.
A comparative study of the structure and crystallization of bulk metallic amorphous rod Pr60Ni30Al10 and melt-spun metallic amorphous ribbon Al87Ni10Pr3 总被引:1,自引:0,他引:1 下载免费PDF全文
Pr-based bulk metallic amorphous (BMA) rods (Pr60Ni30Al10) and Al-based amorphous ribbons (Al87Ni10Pr3) have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter (DSC) indicate that the glass-forming ability (GFA) of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction (XRD) and transmission electron microscope (TEM) show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures. 相似文献
136.
Electron spin resonance spectra of Mn2+ in diluted solid solutions of MnO2 in Y2O3 have been studied at room temperature for Mn concentrations between 0.20 and 2.00 mol%. Isolated Mn2+ ions in sites with two different symmetries were observed, as well as Mn2+ ions coupled by the exchange interaction. The relative concentration of isolated to coupled Mn2+ ions decreases with increasing manganese concentration. The results are consistent with the assumption that the manganese ions occupy preferentially the C2 symmetry sites. A theoretical calculation based on this model yields an effective range of the exchange interaction between Mn2+ ions of 0.53 nm, of the same order as that of Mn2+ ions in CaO. 相似文献
137.
许多实验对用CsI(Tl)闪烁晶体作为探测器来寻找和探测暗物质的可行性进行了研究.本工作利用8MeV单能中子轰击CsI(Tl)晶体探测器来研究Cs核和I核的QuenchingFactor.在数据处理中,运用脉冲形状甄别(PSD)方法来分辨反冲核信号和本底信号.实验结果表明,在7keV到132keV的能区中,Quench ingFactor随着反冲核能量的减少而增加.在探测暗物质的实验中,这一性质对于CsI(Tl)晶体探测器获得较低的能量阈值是很有利的. 相似文献
138.
Franz H. Asthalter T. Dommach M. Ehnes A. Messel K. Sergueev I. 《Hyperfine Interactions》2002,141(1-4):131-134
The present status of the new nuclear resonance beamline PETRA 1 at HASYLAB, DESY, Hamburg is described. Besides an overview
of the experimental setup some examples of recent experiments are given. Those cover the main applications, i.e., inelastic
scattering from iron alloys and quasielastic scattering from glass-forming liquids.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
139.
S.-Y. Sheu D.-Y. Yang H.L. Selzle E.W. Schlag 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):557-563
Charge transport is one important example of signal transduction in a protein which is responsible for action at a distance,
and is a fundamental process in biochemical action. A model is presented in which electronic effects interact with motional
processes to combine into a bifunctional model. This model is investigated with new detailed molecular dynamics calculations
and successfully explains such action at a distance.
Received 1st February 2002 / Received in final form 26 May 2002 Published online 13 September 2002 相似文献
140.
刘金凯 《山东师范大学学报(自然科学版)》2005,20(2):57-58
研究了诺氟沙星—铽(Tb^3 )络合物与核酸(DNA)的相互作用,据此建立了核酸的测定方法,讨论了诺氟沙星—铽与DNA分子之间的结合方式。 相似文献