全文获取类型
收费全文 | 291565篇 |
免费 | 7295篇 |
国内免费 | 5236篇 |
专业分类
化学 | 163187篇 |
晶体学 | 4570篇 |
力学 | 13301篇 |
综合类 | 326篇 |
数学 | 30066篇 |
物理学 | 92646篇 |
出版年
2021年 | 3054篇 |
2020年 | 3338篇 |
2019年 | 3597篇 |
2018年 | 4118篇 |
2017年 | 3994篇 |
2016年 | 5692篇 |
2015年 | 4062篇 |
2014年 | 5828篇 |
2013年 | 12653篇 |
2012年 | 10177篇 |
2011年 | 11810篇 |
2010年 | 8564篇 |
2009年 | 8515篇 |
2008年 | 10312篇 |
2007年 | 10182篇 |
2006年 | 9560篇 |
2005年 | 8651篇 |
2004年 | 7847篇 |
2003年 | 7022篇 |
2002年 | 7043篇 |
2001年 | 8225篇 |
2000年 | 6302篇 |
1999年 | 5050篇 |
1998年 | 4231篇 |
1997年 | 4077篇 |
1996年 | 3975篇 |
1995年 | 3570篇 |
1994年 | 3517篇 |
1993年 | 3355篇 |
1992年 | 3821篇 |
1991年 | 3767篇 |
1990年 | 3711篇 |
1989年 | 3656篇 |
1988年 | 3476篇 |
1987年 | 3486篇 |
1986年 | 3270篇 |
1985年 | 4181篇 |
1984年 | 4185篇 |
1983年 | 3531篇 |
1982年 | 3696篇 |
1981年 | 3534篇 |
1980年 | 3417篇 |
1979年 | 3685篇 |
1978年 | 3943篇 |
1977年 | 3756篇 |
1976年 | 3804篇 |
1975年 | 3557篇 |
1974年 | 3537篇 |
1973年 | 3557篇 |
1967年 | 2649篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
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
13.
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
14.
S. A. Gurevich T. A. Zaraiskaya S. G. Konnikov V. M. Mikushkin S. Yu. Nikonov A. A. Sitnikova S. E. Sysoev V. V. Khorenko V. V. Shnitov Yu. S. Gordeev 《Physics of the Solid State》1997,39(10):1691-1695
The concentration and chemical state of copper in the subsurface region of Cu/SiO2 composite films obtained by simultaneous magnetron sputtering from two sources (Cu and SiO2) are determined by x-ray photoelectron spectroscopy (XPS). It is established that copper in the as-grown film is primarily in the form of unoxidized atoms dispersed in a SiO2 matrix. Annealing of the film results in practically no oxidation, but about 70% of the copper atoms condense into metallic clusters with sizes below 10 Å in the subsurface region and about 50 Å in the bulk of the film. The changes in the binding energy of core electrons, and especially in the energies of Auger electrons, are so large in this situation that photoelectron and Auger spectroscopy are efficient methods for monitoring the chemical state of this composite material. 相似文献
15.
对由一类非线性抛物型变分不等方程所描述的无穷维动力系统,给出了存在全局吸引子及弱近似惯性流形的充分条件. 相似文献
16.
D. V. Vyalykh A. M. Shikin G. V. Prudnikova A. Yu. Grigor’ev A. G. Starodubov V. K. Adamchuk 《Physics of the Solid State》2002,44(1):164-170
This paper reports on the first experimental observation of quantum-well states and sp-type resonances in thin single-crystal gold, silver, and copper layers formed on single-crystal W(110) surfaces, which result from spatial localization of Bloch-type electronic wave functions in a quantum well with potential barriers at the vacuum/metal and metal/W(110) interfaces. The quantization of the valence-band electronic structure in Au/W(110), Ag/W(110), and Cu/W(110) systems was studied experimentally using angle-resolved photoelectron spectroscopy. 相似文献
17.
Yu. V. Borovskikh 《Journal of Mathematical Sciences》1991,53(4):353-358
Estimates of a rate of convergence of orderO(n
–1) are obtained for integral functionals of an empirical process.Translated fromTeoriya Sluchainykh Protsessov, Vol. 15, pp. 10–16, 1987. 相似文献
18.
V. Yu. Korolev 《Journal of Mathematical Sciences》1991,57(4):3270-3277
Translated fromProblemy Ustoichivosti Stokhasticheskikh Modelei. Trudy Seminara, 1988, pp. 84–92. 相似文献
19.
20.