全文获取类型
收费全文 | 267432篇 |
免费 | 2375篇 |
国内免费 | 623篇 |
专业分类
化学 | 142010篇 |
晶体学 | 4164篇 |
力学 | 11922篇 |
综合类 | 9篇 |
数学 | 29481篇 |
物理学 | 82844篇 |
出版年
2019年 | 2290篇 |
2018年 | 3114篇 |
2017年 | 3110篇 |
2016年 | 4482篇 |
2015年 | 2656篇 |
2014年 | 4279篇 |
2013年 | 10672篇 |
2012年 | 8070篇 |
2011年 | 9894篇 |
2010年 | 7082篇 |
2009年 | 6878篇 |
2008年 | 9311篇 |
2007年 | 9516篇 |
2006年 | 8878篇 |
2005年 | 8070篇 |
2004年 | 7424篇 |
2003年 | 6735篇 |
2002年 | 6658篇 |
2001年 | 7325篇 |
2000年 | 5659篇 |
1999年 | 4360篇 |
1998年 | 3859篇 |
1997年 | 3844篇 |
1996年 | 3585篇 |
1995年 | 3332篇 |
1994年 | 3491篇 |
1993年 | 3189篇 |
1992年 | 3664篇 |
1991年 | 3667篇 |
1990年 | 3599篇 |
1989年 | 3457篇 |
1988年 | 3568篇 |
1987年 | 3465篇 |
1986年 | 3285篇 |
1985年 | 4360篇 |
1984年 | 4633篇 |
1983年 | 3872篇 |
1982年 | 4006篇 |
1981年 | 3931篇 |
1980年 | 3910篇 |
1979年 | 3877篇 |
1978年 | 4191篇 |
1977年 | 4107篇 |
1976年 | 4173篇 |
1975年 | 3849篇 |
1974年 | 3893篇 |
1973年 | 4050篇 |
1972年 | 2851篇 |
1971年 | 2378篇 |
1970年 | 2177篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
951.
Polyethyleneimine (PEIM) samples crosslinked by a commercial epoxy resin (Epon 828) were prepared, and their adsorption capacity for acidic gases was studied. The swelling and deswelling characteristics of the crosslinked samples were also examined as part of this program. Reactivation of these adsorbents could be carried out by heat, or by a combination of heat and treatment in dilute alkalies. 相似文献
952.
953.
954.
G. M. Luke L. P. Le B. J. Sternlieb Y. J. Uemura J. H. Brewer R. Kadono R. F. Kiefl S. R. Kreitzman T. M. Riseman C. E. Stronach M. Davis S. Uchida H. Takagi Y. Tokura Y. Hidaka T. Murakami E. A. Early J. T. Markert M. B. Maple C. L. Seaman 《Hyperfine Interactions》1991,63(1-4):311-317
We report muon spin relaxation/rotation measurements on sintered powder samples of Nd2−x
Ce
x
CuO4−y
and a large single crystal of Nd2CuO4−y
. We find an electronic phase diagram which is quite similar to that of hole-doped superconductors such as La2−x
Sr
x
CuO4−y
, although the doping of electrons into the system is less efficient in destroying the static moments on the copper spins.
Static magnetic order in Nd2CuO4−y
appears below about 250 K, and two spin reorientations are seen atT=75 K andT=35 K. Measurements of the magnetic field penetration depth have been unsuccessful due to the rare-earth paramagnetism of
these materials. 相似文献
955.
W. Loveland K. Aleklett J. O. Liljenzin G. T. Seaborg 《Journal of Radioanalytical and Nuclear Chemistry》1992,160(1):181-189
The use of radioanalytical techniques to study heavy ion induced nuclear reactions offers some distinct advantages over conventional physical techniques. Among these are (a) unit Z and A resultion in detecting the reaction products (b) high sensitivity for low probability events (c) lack of low energy thresholds or cutoffs in measuring reactcion product energy spectcra (d) economical use of accelerator time and (e) simple, portable experimental apparatus allowing broad survey measurements of reaction mechanisms at a variety of nuclear particle accelerators. We describe examples of these advantages from our research in nuclear chemistry. 相似文献
956.
G. Principi A. Maddalena Ajay Gupta R. Dal Maschio S. Diré 《Hyperfine Interactions》1992,69(1-4):619-622
Conversion electron Mössbauer spectroscopy (CEMS) has been used to study tin oxide films prepared by sol-gel dipping and sputtering. The spectra of films prepared by sol-gel route result close to that of crystalline SnO2 after heat treatment at a temperature as low as 150°C. The Mössbauer parameters of as sputter deposited films indicate that the structure of the deposited stannic oxide has an amorphous character more pronounced for thinner samples. The structure becomes predominantly that of crystalline SnO2 by heating at 550°C for 30 min provided the film thickness is higher than 10 nm. 相似文献
957.
The possible types of ordering diagrams of ternary substutional alloys with an fcc lattice are analyzed, taking account of interactions in two coordination spheres.Ural Polytechnic Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 38–41, December, 1992. 相似文献
958.
Conde M.E. Bekefi G. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1992,20(3):240-244
A new regime of free-electron laser (FEL) operation using a helical wiggler field and a reversed axial guide magnetic field is reported. The orientation of the axial field is such as to oppose the electron rotation imparted by the helical field. The 33.3-GHz FEL amplifier is driven by a mildly relativistic electron beam (750 kV 300 A, 30 ns) and generates 61 MW of radiation with a 27% conversion efficiency. The results are compared with those obtained when the axial guide field is in its conventional orientation, where considerable loss of power and efficiency is observed 相似文献
959.
960.