全文获取类型
收费全文 | 20680篇 |
免费 | 4807篇 |
国内免费 | 1370篇 |
专业分类
化学 | 5508篇 |
晶体学 | 215篇 |
力学 | 1548篇 |
综合类 | 192篇 |
数学 | 4451篇 |
物理学 | 14943篇 |
出版年
2024年 | 30篇 |
2023年 | 145篇 |
2022年 | 335篇 |
2021年 | 363篇 |
2020年 | 469篇 |
2019年 | 394篇 |
2018年 | 440篇 |
2017年 | 627篇 |
2016年 | 721篇 |
2015年 | 619篇 |
2014年 | 1055篇 |
2013年 | 1307篇 |
2012年 | 1129篇 |
2011年 | 1437篇 |
2010年 | 1061篇 |
2009年 | 1254篇 |
2008年 | 1512篇 |
2007年 | 1601篇 |
2006年 | 1405篇 |
2005年 | 1210篇 |
2004年 | 1066篇 |
2003年 | 969篇 |
2002年 | 1046篇 |
2001年 | 795篇 |
2000年 | 796篇 |
1999年 | 720篇 |
1998年 | 651篇 |
1997年 | 531篇 |
1996年 | 506篇 |
1995年 | 420篇 |
1994年 | 351篇 |
1993年 | 314篇 |
1992年 | 272篇 |
1991年 | 224篇 |
1990年 | 161篇 |
1989年 | 144篇 |
1988年 | 116篇 |
1987年 | 112篇 |
1986年 | 91篇 |
1985年 | 71篇 |
1984年 | 64篇 |
1983年 | 30篇 |
1982年 | 60篇 |
1981年 | 66篇 |
1980年 | 40篇 |
1979年 | 32篇 |
1978年 | 25篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
R. J. Saykally K. M. Evenson D. A. Jennings L. R. Zink A. Scalabrin 《International Journal of Infrared and Millimeter Waves》1987,8(6):653-662
Twenty new cw FIR laser lines in CD3OH, optically pumped by a CO2 laser, are reported. The frequencies of 39 of the stronger laser lines were measured relative to stabilized CO2 lasers with a fractional uncertainty, as determined by the reproducibility of the FIR frequency itself, of 2 parts in 107.Contribution of the U.S. Government, not subject to copyright. 相似文献
52.
Tor Schoenmeyr David Yu Zhang 《Journal of Algorithms in Cognition, Informatics and Logic》2005,57(2):130-139
The string matching with mismatches problem requires finding the Hamming distance between a pattern P of length m and every length m substring of text T with length n. Fischer and Paterson's FFT-based algorithm solves the problem without error in O(σnlogm), where σ is the size of the alphabet Σ [SIAM–AMS Proc. 7 (1973) 113–125]. However, this in the worst case reduces to O(nmlogm). Atallah, Chyzak and Dumas used the idea of randomly mapping the letters of the alphabet to complex roots of unity to estimate the score vector in time O(nlogm) [Algorithmica 29 (2001) 468–486]. We show that the algorithm's score variance can be substantially lowered by using a bijective mapping, and specifically to zero in the case of binary and ternary alphabets. This result is extended via alphabet remappings to deterministically solve the string matching with mismatches problem with a constant factor of 2 improvement over Fischer–Paterson's method. 相似文献
53.
Weidong Gao Meiqiong Zhan Shuhai Fan Janda Shao Zheng-Xiu Fan 《Applied Surface Science》2005,250(1-4):195-202
The laser-induced damage (LID) behavior of narrow-band interference filters was investigated with a Nd:YAG laser at 1064 nm under single-pulse mode and free-running mode. The absorption measurement of such coatings was performed with surface thermal lensing (STL) technique. The damage morphologies under the two different laser modes were also studied in detail. It was found that all the filters exhibited a pass-band-center-dependent absorption and laser-induced damage threshold (LIDT) behavior, but the damage morphologies were diverse. The explanation was given with the analysis of the electric field distribution and the operational behavior of the irradiation laser. 相似文献
54.
55.
TANG Chen ZHANG Fang YAN Hai-Qing CHEN Zhan-Qing LUO Tao 《理论物理通讯》2005,44(3):435-439
We develop the three-step explicit and implicit schemes of exponential fitting methods. We use the three- step explicit exponential fitting scheme to predict an approximation, then use the three-step implicit exponential fitting scheme to correct this prediction. This combination is called the three-step predictor-corrector of exponential fitting method. The three-step predictor-corrector of exponential fitting method is applied to numerically compute the coupled nonlinear Schroedinger equation and the nonlinear Schroedinger equation with varying coefficients. The numerical results show that the scheme is highly accurate. 相似文献
56.
57.
58.
E. Rodriguez E. Jimenez G.J. Jacob A.A.R. Neves C.L. Cesar L.C. Barbosa 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):361
Multilayer PbTe quantum dots (QDs) and SiO2 were grown by pulsed laser deposition (PLD) and Plasma enhanced chemical vapor deposition (PECVD) techniques. The crystalline structure, QD size and size dispersion were observed by high-resolution transmission electron microscopy (HRTEM) measurements. This technique allows one to grow PbTe QDs as small as 1.8 nm diameter and 0.6 nm size dispersion. The whole structure can be used in a Fabry–Perot cavity for an optical device operating at the mid-infrared region. 相似文献
59.
曾六川 《高等学校计算数学学报(英文版)》2003,12(1)
The purpose of this paper is to investigate the problem of approximating fixed points of non-Lipschitizian asymptotically pseudocontractive mappings in an arbitrary real Banach space by the modified Ishikawa iterative sequences with errors. 相似文献
60.