全文获取类型
收费全文 | 12170篇 |
免费 | 1742篇 |
国内免费 | 1400篇 |
专业分类
化学 | 8227篇 |
晶体学 | 147篇 |
力学 | 871篇 |
综合类 | 95篇 |
数学 | 1433篇 |
物理学 | 4539篇 |
出版年
2024年 | 35篇 |
2023年 | 175篇 |
2022年 | 298篇 |
2021年 | 328篇 |
2020年 | 393篇 |
2019年 | 360篇 |
2018年 | 320篇 |
2017年 | 306篇 |
2016年 | 471篇 |
2015年 | 455篇 |
2014年 | 590篇 |
2013年 | 816篇 |
2012年 | 904篇 |
2011年 | 971篇 |
2010年 | 654篇 |
2009年 | 713篇 |
2008年 | 755篇 |
2007年 | 723篇 |
2006年 | 683篇 |
2005年 | 628篇 |
2004年 | 493篇 |
2003年 | 392篇 |
2002年 | 348篇 |
2001年 | 327篇 |
2000年 | 286篇 |
1999年 | 317篇 |
1998年 | 327篇 |
1997年 | 266篇 |
1996年 | 266篇 |
1995年 | 227篇 |
1994年 | 245篇 |
1993年 | 161篇 |
1992年 | 150篇 |
1991年 | 131篇 |
1990年 | 139篇 |
1989年 | 84篇 |
1988年 | 81篇 |
1987年 | 87篇 |
1986年 | 82篇 |
1985年 | 71篇 |
1984年 | 48篇 |
1983年 | 33篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 20篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
本文介绍了一种新的自动调焦方法准直小孔法.对自动调焦的原理和后继电路处理方法作了详细的分析.它具有响应时间短、灵敏度高,能够很好的在激光直接写入系统中克服物镜工作台运动中导轨的不平和轴向窜动所造成的离焦。 相似文献
72.
Wanhui Liu Jianghong Tang Ying Wang Guoli Shen R. Yu 《Analytical and bioanalytical chemistry》1998,362(4):387-390
An optical fiber sensor for the continuous determination of hydrochloric acid is presented. It is based on the fluorescence quenching of a flavone containing copolymer membrane by hydrochloric acid. The quenching efficiency is greatly enhanced in the presence of Fe(III). This enhancement is attributed to the primary inner filter effect, as well as the formation of a complex between the 4′-N,N-dimethylaminoflavone group in the copolymer and the Fe(III) species extracted from hydrochloric acid solution. The optical response is linear and reversible for 0.10–6.00 mol L–1 HCl with a response time of the order of a second. The standard deviations for repeated alternative measurements of 0.20 and 2.00 mol L–1 hydrochloric acid are 0.32% and 0.46% (n = 10), respectively, indicating a good reproducibility. Because of the covalently bonding of the dye to polymer, the sensor exhibits also a good stability. Selectivity has also been evaluated for some potential interferents. The sensor in conjunction with a flow-injection system can be used for on-line determination of hydrochloric acid. 相似文献
73.
半导体激光泵浦预激光锁模调Q固体激光器研究 总被引:1,自引:0,他引:1
报道半导体激光侧面泵浦预激光锁模调Q的Nd:YAG固体板条激光器,预激光锁模调Q的激光脉冲宽度为36ps,调Q包纤各心的锁模单脉冲能量超过7μJ,相应的峰值功率达200kW。 相似文献
74.
Shitong Zhu Qizhi Guo Wenda Shen Shitao Wang 《International Journal of Theoretical Physics》1995,34(2):169-177
The optical metric for a strong-laser plasma is derived. The affine connection and curvature related to the optical metric are given and their spatial distributions are studied numerically. 相似文献
75.
Conflict resolution methodology is discussed with fuzzified Pareto frontier. Four solution concepts, namely, the Nash solution, the generalized Nash solution, the Kalai-Smorodinsky concept, and a solution method based on a special bargaining process are examined. The solutions are also fuzzy, the corresponding payoff values are fuzzy numbers, the membership functions of which are determined. Three particular cases are considered in the paper. Linear, quadratic, and general nonlinear Pareto frontiers with known shape are examined. 相似文献
76.
Theformationofanewtypeofself_assembledmultilayerfilms,moleculardeposition(MD)films[1,2],isafastdevelopingareaofthinfilmresearch.Thisnewmethodoffilmpreparationisbasedonionicattractionbetweenoppositechargedchromophores.IncomparisonwiththeclassicLangmuir_Blo… 相似文献
77.
78.
79.
80.
This paper proves that any set of n points in the plane contains two points such that any circle through those two points encloses at least
points of the set. The main ingredients used in the proof of this result are edge counting formulas for k-order Voronoi diagrams and a lower bound on the minimum number of semispaces of size at most k.Work on this paper by the first author has been supported by Amoco Fnd. Fac. Dev. Comput. Sci. 1-6-44862 and by the National Science Foundation under Grant CCR-8714565, by the second author has been partially supported by the Digital Equipment Corporation, by the fourth author has been partially supported by the Office of Naval Research under Grant N00014-86K-0416. 相似文献