全文获取类型
收费全文 | 453889篇 |
免费 | 4560篇 |
国内免费 | 1337篇 |
专业分类
化学 | 250179篇 |
晶体学 | 7029篇 |
力学 | 19509篇 |
综合类 | 13篇 |
数学 | 48232篇 |
物理学 | 134824篇 |
出版年
2018年 | 4501篇 |
2017年 | 4444篇 |
2016年 | 7099篇 |
2015年 | 4725篇 |
2014年 | 7086篇 |
2013年 | 18709篇 |
2012年 | 14240篇 |
2011年 | 17294篇 |
2010年 | 11967篇 |
2009年 | 11571篇 |
2008年 | 15778篇 |
2007年 | 16026篇 |
2006年 | 15053篇 |
2005年 | 13673篇 |
2004年 | 12481篇 |
2003年 | 11198篇 |
2002年 | 11007篇 |
2001年 | 12431篇 |
2000年 | 9693篇 |
1999年 | 7539篇 |
1998年 | 6304篇 |
1997年 | 6368篇 |
1996年 | 6127篇 |
1995年 | 5636篇 |
1994年 | 5680篇 |
1993年 | 5343篇 |
1992年 | 6223篇 |
1991年 | 6029篇 |
1990年 | 5889篇 |
1989年 | 5765篇 |
1988年 | 5820篇 |
1987年 | 5707篇 |
1986年 | 5361篇 |
1985年 | 7183篇 |
1984年 | 7379篇 |
1983年 | 6147篇 |
1982年 | 6467篇 |
1981年 | 6327篇 |
1980年 | 6191篇 |
1979年 | 6353篇 |
1978年 | 6824篇 |
1977年 | 6582篇 |
1976年 | 6607篇 |
1975年 | 6180篇 |
1974年 | 6209篇 |
1973年 | 6362篇 |
1972年 | 4403篇 |
1971年 | 3668篇 |
1968年 | 3785篇 |
1967年 | 3986篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Günter Pickert 《Archiv der Mathematik》1992,58(4):397-398
Ohne Zusammenfassung 相似文献
992.
A study is reported on carbides electrolytically extracted from two different types of high speed tool steels as quenched and after tempering. According to X-ray diffraction analysis and EDS microanalysis, Mössbauer spectra show the presence of MC and M6C in every analysed sample. Only a few substitutional Fe atoms should be present in MC and they give a minor contribution to the Mössbauer spectrum. A model for evaluating the Mössbauer spectrum of M6C is proposed which is based on the symmetry of lattice sites occupied by Fe atoms and partially substituted by other metallic atoms. The proposed model also allows to get information on the amount of this substitution. 相似文献
993.
A. Yu. Khodjamirian
A. G. Oganessian
《Nuclear Physics B》1992,380(3):431-443The leading nonperturbative contribution to the cross section of charm production in two-photon collisions is calculated in QCD. Operator expansion is used and the c-quark interaction with vacuum gluon condensate is taken into account. As a result, the moments of the charm contribution to the photon structure function are obtained. The moments with sufficiently high numbers turn out to be sensitive to the gluon condensate. 相似文献
994.
A multilayer structure consisting of undoped GaAs and AlAs layers was incorporated into a buffer layer on GaAs substrates. This reduces the spreading of impurities from the substrate (e.g. tellurium) into layers deposited on top of the multilayer system as observed by SIMS and C/V profiling. Incorporation coefficients for tellurium in GaAs, AlAs and multilayers were calculated. 相似文献
995.
Physical Engineering Institute, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 5, pp. 565–574, May, 1991. 相似文献
996.
MacLatchy C.S. Smith H.C.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(6):1254-1258
The electron current to a Langmuir probe in a moving high-pressure plasma has been measured and analyzed. The plasma is an atmospheric-pressure propane flame, and the probe's speed relative to the plasma was varied from 10 ms-1 to 30 ms-1. The current is linearly dependent on the speed and appears to be comprised of two components-one driven by diffusion and the other by convection. A model is devised which can be used to measure the electron density. By comparing the density computed from this model to that measured from the ion current, it has been possible to measure the electron mobility in the flame gases. The value obtained by the authors is in good agreement with theoretical calculations found in the literature 相似文献
997.
The determination of doxazosin by high-performance liquid chromatography with fluorescence detection is described. Propanolol was used as the internal standard. Plasma samples were treated with methanol to precipitate the proteins. Doxazosin was isolated with C18 reversed-phase extraction columns. The determination limit is 1 ng/ml of plasma, while the extraction columns can be reused frequently. The method is applied to clinical trial samples. 相似文献
998.
In vitro and in vivo proton T1 data are reported that demonstrate that the paramagnetic copper-D-penicillamine complex can be applied as a potential contrast agent to magnetic resonance imaging. 相似文献
999.
Electron energy distribution functions (eedf) in CO2 laser discharge (He—CO2—N2—CO mixture) have been calculated by solving the Boltzmann equation in the presence of given concentrations of excited (vibrational and electronic) states. The results show a well structured eedf as a result of second kind collisions coming from metastable electronic states of N2 and He as well as a strong dependence of rate coefficients for CO2 dissociation and for the ionization of the different species. 相似文献
1000.
Ulrich Mayerhofer T. von Egidy J. Jolie H. G. Börner G. Colvin S. Judge B. Krusche S. J. Robinson K. Schreckenbach S. Brant V. Paar 《Zeitschrift für Physik A Hadrons and Nuclei》1991,341(1):1-8
Gamma rays of199Au obtained after double neutron capture in197Au were measured at the ILL high flux reactor. A level scheme up to 1770 keV excitation energy is established. The result is compared with IBFM and Boson-Fermion-Symmetry calculations. 相似文献