全文获取类型
收费全文 | 389954篇 |
免费 | 3126篇 |
国内免费 | 1034篇 |
专业分类
化学 | 203965篇 |
晶体学 | 5997篇 |
力学 | 18453篇 |
综合类 | 16篇 |
数学 | 45819篇 |
物理学 | 119864篇 |
出版年
2020年 | 3499篇 |
2019年 | 4178篇 |
2018年 | 6502篇 |
2017年 | 6571篇 |
2016年 | 8172篇 |
2015年 | 4435篇 |
2014年 | 7355篇 |
2013年 | 16447篇 |
2012年 | 13037篇 |
2011年 | 15206篇 |
2010年 | 11405篇 |
2009年 | 11469篇 |
2008年 | 14316篇 |
2007年 | 14168篇 |
2006年 | 12913篇 |
2005年 | 14068篇 |
2004年 | 13192篇 |
2003年 | 11099篇 |
2002年 | 9614篇 |
2001年 | 10415篇 |
2000年 | 8062篇 |
1999年 | 6091篇 |
1998年 | 5225篇 |
1997年 | 5330篇 |
1996年 | 4932篇 |
1995年 | 4204篇 |
1994年 | 4402篇 |
1993年 | 4347篇 |
1992年 | 4764篇 |
1991年 | 4893篇 |
1990年 | 4683篇 |
1989年 | 4739篇 |
1988年 | 4600篇 |
1987年 | 4573篇 |
1986年 | 4375篇 |
1985年 | 5644篇 |
1984年 | 5821篇 |
1983年 | 4763篇 |
1982年 | 5026篇 |
1981年 | 4879篇 |
1980年 | 4496篇 |
1979年 | 5039篇 |
1978年 | 5138篇 |
1977年 | 5292篇 |
1976年 | 5311篇 |
1975年 | 4968篇 |
1974年 | 4885篇 |
1973年 | 5110篇 |
1972年 | 3666篇 |
1971年 | 3340篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
E. Jackiewicz M. Lukasiak M. Kopcewicz K. Szpila N. Bakun-Czubarow 《Hyperfine Interactions》1992,70(1-4):993-996
Terrestrial basalt rocks considered to be a good analogues of the Martian regolith were studied by using the Mössbauer spectroscopy and X-ray diffraction. The weathering of basalts was followed by the changes of the Fe2+/Fe3+ ratio. The basalt rock undergoes alteration from primary mineral composition (olivine+pyroxene+plagioclase) through smectite to kaolinite clay with oxides and hydroxides with the increase of the Fe2+/Fe3+ ratio. 相似文献
192.
The dependence of distribution functions of quarks, antiquarks, diquarks and their fragmentation into hadrons on the transverse momentumk t is discussed in the frame of the quark-gluon string model. We then discuss the division ofk t between 2n-quark-antiquark chains, orn-pomeron showers. Hadron and hadron-nuclear processesp?p,p?A,K +?p,K +?A are analysed. A strong dependence of the observed values on the numbern is derived by this method, which is of special importance for the analysis of hadron-nucleus collisions. Our method is compared with the regulark t division method. 相似文献
193.
194.
NaY zeolite samples loaded with sodium metal by vapor phase deposition have been investigated using129Xe NMR spectroscopy. At low sodium concentration, the129Xe NMR spectrum showed three resonance lines which clearly indicate the existence of distinct domains in the zeolite sample. Such an observation suggests that the diffusion of the xenon atoms into each domain only occurs with respect to the NMR time scale (2.9 ms). As the sodium concentration increases, observation of a single broad line indicate a macroscopic homogenization of the system. The shift of this line is explained in part due to a paramagnetic interaction between the xenon atoms and the unpaired electrons of particles containing an odd number of sodium atoms. The linewidth is due to the distribution of the local magnetic fields partially averaged by the rapid motion of the xenon atoms and to the statistical distribution of the sodium particles in the supercage cavities. The paramagnetic interaction vanishes with the oxidation of the sample leading to a narrowing and a shift of the line to higher magnetic fields. 相似文献
195.
Myagchenkov V. A. Chichkanov S. V. Proskurina V. E. Myagchenkov A. V. 《Russian Journal of Applied Chemistry》2002,75(9):1485-1488
The Thoms effect observed with water-soluble cationic copolymer of acrylamide was studied in relation to the concentration, molecular weight, and molecular weight polydispersity of the polymeric additive, with its composition and composition polydispersity being constant. 相似文献
196.
The three-band two-dimensional repulsive Hubbard model in the formalism of the temperature Green function is investigated.
The applicability of the weak coupling approach at the values of the dimensionless coupling constant U/t≈10–11 is justified.
The normal state, the antiferromagnetic state with Neel magnetic ordering on the “copper” sublattice, and the superconducting
state with nontrivial Cooper pairing in channels with odd angular momenta are studied. The possibility of other magnetic states
in the model is discussed. Bibliography: 20 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 209, 1994, pp. 194–228.
Translated by K. Malyshev. 相似文献
197.
Alloys of the systems Fe–Al (mixable over the whole concentration range) and Fe–Mg (insoluble with each other) were produced by implantation of Fe ions into Al and Mg, respectively. The implantation energy was 200 keV and the ion doses ranged from 1 × 1014 to 9 × 1017cm-2The obtained implantation profiles were determined by Auger electron spectroscopy depth profiling. Maximum iron concentrations reached were up to 60 at.% for implantation into Al and 94 at.% for implantation into Mg. Phase analysis of the implanted layers was performed by conversion electron Mössbauer spectroscopy and X‐ray diffraction. For implantation into Mg, two different kinds of Mössbauer spectra were obtained: at low doses paramagnetic doublets indicating at least two different iron sites and at high doses a dominant ferromagnetic six‐line‐pattern with a small paramagnetic fraction. The X‐ray diffraction pattern concluded that in the latter case a dilated αiron lattice is formed. For implantation into Al, the Mössbauer spectra were doublet structures very similar to those obtained at amorphous Fe–Al alloys produced by rapid quenching methods. They also indicated at least two different main iron environments. For the highest implanted sample a ferromagnetic six‐line‐pattern with magnetic field values close to those of Fe3Al appeared. 相似文献
198.
N. Yu. Netsvetaev 《Journal of Mathematical Sciences》1998,91(6):3460-3468
Some corollaries of the Hirzebruch-Thom signature theorem are discussed. The multiplicativity of the signature and the naturalness
of the Pontryagin classes for coverings in the case of ℚ-homology manifolds is proved. A geometric proof of Hirzebruch’s well-known
“functional equation” for the virtual signature is outlined. Bibliography: 25 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 231, 1995, pp. 197–209.
Translated by N. Yu. Netsvetaev. 相似文献
199.
200.