全文获取类型
收费全文 | 3734篇 |
免费 | 70篇 |
国内免费 | 24篇 |
专业分类
化学 | 2310篇 |
晶体学 | 26篇 |
力学 | 76篇 |
数学 | 600篇 |
物理学 | 816篇 |
出版年
2022年 | 30篇 |
2021年 | 38篇 |
2020年 | 58篇 |
2019年 | 42篇 |
2018年 | 25篇 |
2017年 | 23篇 |
2016年 | 45篇 |
2015年 | 51篇 |
2014年 | 47篇 |
2013年 | 164篇 |
2012年 | 162篇 |
2011年 | 178篇 |
2010年 | 99篇 |
2009年 | 87篇 |
2008年 | 153篇 |
2007年 | 189篇 |
2006年 | 177篇 |
2005年 | 173篇 |
2004年 | 169篇 |
2003年 | 139篇 |
2002年 | 124篇 |
2001年 | 84篇 |
2000年 | 96篇 |
1999年 | 52篇 |
1998年 | 65篇 |
1997年 | 56篇 |
1996年 | 62篇 |
1995年 | 63篇 |
1994年 | 51篇 |
1993年 | 70篇 |
1992年 | 43篇 |
1991年 | 40篇 |
1990年 | 46篇 |
1989年 | 45篇 |
1988年 | 37篇 |
1987年 | 42篇 |
1986年 | 42篇 |
1985年 | 58篇 |
1984年 | 47篇 |
1983年 | 38篇 |
1982年 | 34篇 |
1981年 | 37篇 |
1980年 | 36篇 |
1979年 | 26篇 |
1978年 | 30篇 |
1977年 | 39篇 |
1976年 | 45篇 |
1975年 | 49篇 |
1974年 | 41篇 |
1973年 | 45篇 |
排序方式: 共有3828条查询结果,搜索用时 15 毫秒
11.
Lancaster G.P.T. Häffner H. Wilson M.A. Becher C. Eschner J. Schmidt-Kaler F. Blatt R. 《Applied physics. B, Lasers and optics》2003,76(8):805-808
We present a scheme for employing a violet extended-cavity diode laser in experiments with single, trapped ions. For this the grating-stabilised laser is spatially and spectrally filtered and referenced to a Fabry–Pérot cavity. We measure an upper limit to the line width by observing a 305-kHz FWHM beat note with the second harmonic of a titanium sapphire laser. The laser is subsequently used to optically cool a single 40Ca+ ion close to the Doppler limit. PACS 03.67.Lx; 32.80.Pj; 42.55.Px 相似文献
12.
It is proved that for finite groups G, the probability thattwo randomly chosen elements of G generate a soluble subgrouptends to zero as the index of the largest soluble normal subgroupof G tends to infinity. 相似文献
13.
14.
15.
Future contributions toJournal of Chemical Crystallography 相似文献
16.
17.
18.
A. L'Esprance J. Nicolas D.K. Wilson D.W. Thomson Y. Gabillet G. Daigle 《Applied Acoustics》1993,40(4)
This paper presents a set of acoustical and meteorological data from an outdoor sound propagation experiment. This experiment was done in a farm field near Rock Springs, Pennsylvania, on 7 July 1990. Meteorological and acoustical measurements were recorded simultaneously during six different times in the day. The meteorological measurements permitted determination of the sound speed profiles during each of the measurement sessions, using a method based on surface-layer similarity scaling. The acoustical measurements allowed precise determination of the relative sound pressure levels for a frequency range up to 3150 Hz at six different distances (66, 88, 125, 175, 250 and 350 m). The results show atmospheric conditions have an important effect on sound propagation. At medium and high frequencies, variations of the relative SPL have been measured at distances as short as 62 m. These effects increased with the distances so that variations as great as 30 dB have been measured during that day. Comparisons with the fast field program predictions are also presented, and amply demonstrate the accuracies of this model, especially for the downward refraction cases. 相似文献
19.
20.
B Karimi S M T Fatemi Ghomi J M Wilson 《The Journal of the Operational Research Society》2006,57(2):140-147
In this paper, the multi-item, single-level, capacitated, dynamic lot sizing problem with set-up carry-over and backlogging, abbreviated to CLSP+, is considered. The problem is formulated as a mixed integer programming problem. A heuristic method consisting of four elements: (1) a demand shifting rule, (2) lot size determination rules, (3) checking feasibility conditions and (4) set-up carry-over determination, provides us with an initial feasible solution. The resulting feasible solution is improved by adopting the corresponding set-up and set-up carry-over schedule and re-optimizing it by solving a minimum-cost network flow problem. Then the improved solution is used as a starting solution for a tabu search procedure, with the value of moves assessed using the same minimum-cost network problem. Computational results on randomly generated problems show that the algorithm, which is coded in C++, is able to provide optimal solutions or solutions extremely close to optimal. The computational efficiency makes it possible to solve reasonably large problem instances routinely on a personal computer. 相似文献