全文获取类型
收费全文 | 18600篇 |
免费 | 1601篇 |
国内免费 | 1034篇 |
专业分类
化学 | 11960篇 |
晶体学 | 153篇 |
力学 | 626篇 |
综合类 | 110篇 |
数学 | 3020篇 |
物理学 | 5366篇 |
出版年
2023年 | 243篇 |
2022年 | 346篇 |
2021年 | 416篇 |
2020年 | 471篇 |
2019年 | 453篇 |
2018年 | 449篇 |
2017年 | 475篇 |
2016年 | 911篇 |
2015年 | 730篇 |
2014年 | 896篇 |
2013年 | 1467篇 |
2012年 | 1303篇 |
2011年 | 1412篇 |
2010年 | 926篇 |
2009年 | 786篇 |
2008年 | 912篇 |
2007年 | 777篇 |
2006年 | 643篇 |
2005年 | 512篇 |
2004年 | 479篇 |
2003年 | 447篇 |
2002年 | 484篇 |
2001年 | 395篇 |
2000年 | 277篇 |
1999年 | 318篇 |
1998年 | 239篇 |
1997年 | 206篇 |
1996年 | 222篇 |
1995年 | 190篇 |
1994年 | 185篇 |
1993年 | 168篇 |
1992年 | 161篇 |
1991年 | 149篇 |
1990年 | 112篇 |
1989年 | 119篇 |
1988年 | 117篇 |
1987年 | 115篇 |
1986年 | 108篇 |
1985年 | 132篇 |
1984年 | 112篇 |
1983年 | 99篇 |
1982年 | 92篇 |
1981年 | 90篇 |
1980年 | 97篇 |
1978年 | 96篇 |
1977年 | 100篇 |
1974年 | 87篇 |
1973年 | 95篇 |
1968年 | 88篇 |
1965年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
几种陆用惯性自寻北方案的比较 总被引:2,自引:1,他引:1
介绍几种目前广泛应用于军事及民用工业领域的高精度自寻北方案,同时讨论并分析了这些方案的精度和误差补偿方法,提出在兵器领域尤其是在陆用车辆上的适用性等问题。 相似文献
42.
K. Prokeš 《Czechoslovak Journal of Physics》2002,52(2):253-258
Many materials exhibit various magnetic phenomena as a function of magnetic field, temperature and/or pressure. Usually, bulk magnetic measurements provide first information on the magnetic state of the material by measuring their response on the applied magnetic field. However, it is necessary to investigate materials also on a microscopic scale. This is often done by means of neutron scattering. In this contribution we discuss basic ideas of this method and we report on few experimental results obtained with a split-pair coil 14.5 T superconducting magnet which can be combined with dilution stick offering temperatures as low as 30 mK and/or with a small clamped-type pressure cell which offers pressure up to 1.0 GPa. 相似文献
43.
Shuguan Ji Zhenxin Liu Shaoyun Shi 《Journal of Mathematical Analysis and Applications》2007,325(2):1306-1313
The method of equivalent variational methods, originally due to Carathéodory for free problems in the calculus of variations is extended to investigate boundary value problems for a class of second order differential equations on the half-line. Some applications are presented to illustrate the potential of this method. 相似文献
44.
The validity of local parton-hadron duality within the framework of HERWIG and JETSET event generators is investigated. We concentrate one
+
e
– annihilations in LEP 2 energy range as these interactions provide theoretically the cleanest condition for the discussion of this concept. We conclude that the concept of local parton-hadron duality is not valid in either of the two generators considered. 相似文献
45.
Š. Jakševičius 《Lithuanian Mathematical Journal》1992,32(2):174-180
Kaunas Academy of Agriculture, 4324 Noreikiškés, Lithuania. Translated from Lietuvos Matematikos Rinkinys, Vol. 32, No. 2,
pp. 221–228, April–June, 1992. 相似文献
46.
The laser cladding of Fe-based alloys on a medium carbon steel substrate was performed using a CO2 laser and Ar shielding gas that was blown into a molten pool. The microstructure and cracking susceptibility of the laser-clad layers were studied in terms of carbon additions. Results show that the small change of the carbon content in the alloy powders can obviously change the microstructure and properties of the layers. When the carbon content is in the range of 0.3–0.4 wt.%, the decrease of the carbon content in alloy powders will increase the hardness and toughness of the layers simultaneously under the same process parameters. As a result, crack-free coatings with high hardness can be obtained. As the carbon content increases from 0.2 wt.% to 0.4 wt.%, the segregation ratio of chromium increases, while the segregation ratios of nickel, manganese, and silicon first decrease and then increase. At the same time, a new designing principle concerning the composition and microstructure has been put forward, and the principal mechanisms of strengthening and toughening of the layers are fine-grain strengthening and low carbon martensitic phase transformation strengthening. 相似文献
47.
48.
František Toman Ludvík Beneš 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):231-236
Differential molar adsorption enthalpies (DMAE) were determined by gas chromatographic measurements of specific retention
volume of vapors on the surface of two forms of Mg–Al hydrotalcite. A linear dependence of the DMAE on the number of the carbon
atoms in hydrocarbons was observed for both form of hydrotalcite. The dependence of the differential molar adsorption enthalpies
on the number of chlorine atoms in organic molecules is discussed. A linear dependence of DMAE on the molecular weight of
chloroderivatives of methane and ethylene on the basic form in an order monochloromethane < dichloromethane < trichloromethane
or vinylidene chloride < 1,1-dichloroethylene < trichloroethylene was found. 相似文献
49.
The paper is devoted to the research of large deviation probabilities in the approximation by compound Poisson law. 相似文献
50.
Oriňák Andrej Arlinghaus Heinrich Frank Vering Guido Justinová Martina Oriňáková Renáta Turčániová L’udmila Halama Maroš 《平面色谱法杂志一现代薄层色谱法》2003,16(1):23-27
JPC – Journal of Planar Chromatography – Modern TLC - Two interfaces have been tested for coupling thin-layer chromatography (TLC) with time-of-flight secondary-ion mass spectrometry... 相似文献