全文获取类型
收费全文 | 128744篇 |
免费 | 8683篇 |
国内免费 | 19961篇 |
专业分类
化学 | 104959篇 |
晶体学 | 2729篇 |
力学 | 2974篇 |
综合类 | 1175篇 |
数学 | 15301篇 |
物理学 | 30250篇 |
出版年
2024年 | 269篇 |
2023年 | 1523篇 |
2022年 | 3392篇 |
2021年 | 3347篇 |
2020年 | 3756篇 |
2019年 | 3511篇 |
2018年 | 2976篇 |
2017年 | 4151篇 |
2016年 | 4315篇 |
2015年 | 3646篇 |
2014年 | 5006篇 |
2013年 | 10102篇 |
2012年 | 8491篇 |
2011年 | 7563篇 |
2010年 | 6492篇 |
2009年 | 8514篇 |
2008年 | 8512篇 |
2007年 | 8722篇 |
2006年 | 7962篇 |
2005年 | 6821篇 |
2004年 | 6351篇 |
2003年 | 5338篇 |
2002年 | 6256篇 |
2001年 | 3968篇 |
2000年 | 3676篇 |
1999年 | 3326篇 |
1998年 | 2842篇 |
1997年 | 2288篇 |
1996年 | 1963篇 |
1995年 | 1862篇 |
1994年 | 1656篇 |
1993年 | 1378篇 |
1992年 | 1270篇 |
1991年 | 894篇 |
1990年 | 712篇 |
1989年 | 675篇 |
1988年 | 524篇 |
1987年 | 392篇 |
1986年 | 347篇 |
1985年 | 327篇 |
1984年 | 313篇 |
1983年 | 168篇 |
1982年 | 258篇 |
1981年 | 251篇 |
1980年 | 244篇 |
1979年 | 237篇 |
1978年 | 209篇 |
1977年 | 161篇 |
1976年 | 132篇 |
1973年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Shougo Higashi 《Surface science》2006,600(3):591-597
We have studied the individual adsorption of Mn and Bi, and their coadsorption on Cu(0 0 1) by low-energy electron diffraction (LEED). For Mn, we have determined the c(2 × 2) structure formed at 300 K, whose structure had been determined by several methods. We reconfirmed by a tensor LEED analysis that it is a substitutional structure and that a previously reported large corrugation (0.30 Å) between substitutional Mn and remaining surface Cu atoms coincides perfectly with the present value. In the individual adsorption of Bi, we have found a c(4 × 2) structure, which is formed by cooling below ∼250 K a surface prepared by Bi deposition of ∼0.25 ML coverage at 300 K where streaky half-order LEED spots appear. The c(4 × 2) structure has been determined by the tensor LEED analysis at 130 K and it is a substitutional structure. In the coadsorption, we found a c(6 × 4) structure, which has been determined by the tensor LEED analysis. It is very similar to the previously determined structure of the c(6 × 4) formed by coadsorption of Mg and Bi, and embedded MnBi4 clusters are arranged in the top Cu layer instead of MgBi4. Large lateral displacements of Bi atoms in the c(6 × 4)-(Mn + Bi) suggest that the Mn atoms undergo the size-enhancement caused by their large magnetic moment. 相似文献
22.
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
23.
GAO Jing ZHOU Xiaohua CHEN Xun Chongqing University Chemical Engineering Department Chongqing China 《Chinese Journal of Reactive Polymers》2006,(2)
1. INTRODUCTION In the process of coking plant, about 30%~35% sulfur is transformed to H2S and some other sulfide, which form impurity in coal gas together with NH3 and HCN. Only 0.1% H2S containing in air can lead to die, so it is very important to carry on desulphurization and decyanation with coal gas [1~3]. Currently desulphurization and decyanation craft technique have Dry Oxidation Technology, Wet Oxidation Technology and Liquid Absorption Technology [2] three main kinds. The… 相似文献
24.
meso-Tetra(n-hexyloxycarbonyl)porphyrin was found to be converted into porphine, the mother compound of porphyrins, in a 77% yield when heated in aqueous sulfuric acid at 180 °C over 30 min under an inert atmosphere. The observation demonstrates that the substituted porphyrin serves as a novel and useful precursor for porphine. 相似文献
25.
We obtain upper bounds for the tail distribution of the first nonnegative sum of a random walk and for the moments of the overshoot over an arbitrary nonnegative level if the expectation of jumps is positive and close to zero. In addition, we find an estimate for the expectation of the first ladder epoch. 相似文献
26.
The breakthrough and stoichiometric SO2 adsorption efficiencies of a biomass supported Na2CO3 system (80 wt %Na2CO3/straw) have reached 48.9% and 80.6% respectively at a desulfurization temperature of 80℃. 相似文献
27.
28.
Kasper K. Berthelsen Jesper Møller 《Bulletin of the Brazilian Mathematical Society》2002,33(3):351-367
This primer provides a self-contained exposition of the case where spatial birth-and-death processes are used for perfect
simulation of locally stable point processes. Particularly, a simple dominating coupling from the past (CFTP) algorithm and
the CFTP algorithms introduced in [13], [14], and [5] are studied. Some empirical results for the algorithms are discussed.
Received: 30 June 2002 相似文献
29.
Let G=(V(G),E(G)) be a graph. A (n,G, λ)‐GD is a partition of the edges of λKn into subgraphs (G‐blocks), each of which is isomorphic to G. The (n,G,λ)‐GD is named as graph design for G or G‐decomposition. The large set of (n,G,λ)‐GD is denoted by (n,G,λ)‐LGD. In this work, we obtain the existence spectrum of (n,P3,λ)‐LGD. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 151–159, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10008 相似文献
30.
A design of diode-pumped high-efficiency Nd:YVO4/LBO red laser is reported. Using critical phase-matching (CPM) LBO, 671 nm red laser was obtained from 1342 nm light by intracavity frequency doubling. With an incident pump laser of 800 mW, using type-I and type-II CPM LBO, 97 and 52 mWTEM00 mode red laser outputs were obtained, with optical-to-optical conversion efficiencies of up to 12.1% and 6.5%, respectively. 相似文献