全文获取类型
收费全文 | 330421篇 |
免费 | 3065篇 |
国内免费 | 940篇 |
专业分类
化学 | 165106篇 |
晶体学 | 5390篇 |
力学 | 15555篇 |
综合类 | 7篇 |
数学 | 38492篇 |
物理学 | 109876篇 |
出版年
2021年 | 3154篇 |
2020年 | 3344篇 |
2019年 | 3778篇 |
2018年 | 5208篇 |
2017年 | 5459篇 |
2016年 | 7393篇 |
2015年 | 4150篇 |
2014年 | 7054篇 |
2013年 | 15935篇 |
2012年 | 12414篇 |
2011年 | 14862篇 |
2010年 | 11042篇 |
2009年 | 10932篇 |
2008年 | 13255篇 |
2007年 | 13206篇 |
2006年 | 12152篇 |
2005年 | 10544篇 |
2004年 | 9839篇 |
2003年 | 8695篇 |
2002年 | 8683篇 |
2001年 | 10405篇 |
2000年 | 7663篇 |
1999年 | 5972篇 |
1998年 | 4978篇 |
1997年 | 4818篇 |
1996年 | 4485篇 |
1995年 | 3868篇 |
1994年 | 3824篇 |
1993年 | 3705篇 |
1992年 | 4099篇 |
1991年 | 4309篇 |
1990年 | 4102篇 |
1989年 | 4008篇 |
1988年 | 3782篇 |
1987年 | 3922篇 |
1986年 | 3686篇 |
1985年 | 4631篇 |
1984年 | 4683篇 |
1983年 | 3886篇 |
1982年 | 3976篇 |
1981年 | 3697篇 |
1980年 | 3649篇 |
1979年 | 3914篇 |
1978年 | 3903篇 |
1977年 | 3908篇 |
1976年 | 3880篇 |
1975年 | 3675篇 |
1974年 | 3615篇 |
1973年 | 3650篇 |
1972年 | 2603篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
A new microscopic model of anomalous muonium for the elemental semiconductors is proposed. The relevant configuration consisting
of both a diamagrentic molecule Si−Mu and an unpaired orbital e− is contained into a semivacancy of the real lattice. By using the unrestricted Hartree-Fock computational method the principal
properties of the system are established. A dynamical version of the model together with a question on the formation of such
system are discussed. 相似文献
192.
An explicit expression is obtained for the Green's functions of a massive scalar field for nonnull temperatures and density in the form of a series in powers of m/T. The equivalence of the spectral-geometric approach and the temperature technique of Matsubara and Bernard is demonstrated. Corrections to the Stefan-Boltzmann law are obtained on the basis of the calculated Green's functions. The energy density is calculated in regions of high and low temperatures. The formulas obtained can prove to be useful in the discussion of the phase transition hadrons-quark-gluon plasma.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 32–40, July, 1991. 相似文献
193.
194.
195.
E. R. Bauminger E. Fibach A. M. Konijn S. Ofer E. A. Rachmilewitz 《Hyperfine Interactions》1991,66(1-4):11-23
Mössbauer studies in murine (MEL) and human K-562 erythroleukemia cell lines have been utilized to study the fate of iron during intracellular Hb synthesis and denaturation. The results showed that ferritin can serve as an intermediate iron pool for Hb synthesis and for storage of iron released during intracellular Hb denaturation. 相似文献
196.
Using the appropriate harmonic oscillator states and reasonable approximations, we construct coherent wavepackets corresponding
to the solutions of the Klein-Gordon equation for the attractive potentialV(r)=−k/r, k>0, in two and three space dimensions. We deduce the corresponding classical limit in two dimension by requiring that the
expectation value 〈r〉 of the radial variable is large. In the case of three dimensions, besides the condition of large 〈r〉, we make the uncertainty Δr=[〈r
2〉 − 〈r〉2]1/2 a minimum with respect to certain parameter of the wavepacket. We then investigate the trajectory traversed by the wavepacket
in the classical limit. We find that the classical limit of this relativistic quantal problem gives, in the leading order,
the same expression for the rate of motion of the perihelion as that given by the solution of the corresponding special relativistic
classical dynamical problem. We also briefly discuss some of the subtle aspects of the classical limit of the relativistic
quantal system, in general. 相似文献
197.
Dmitrii S. Silvestrov 《Acta Appl Math》1994,34(1-2):109-124
Coupling procedures for Markov renewal processes are described. Applications to ergodic theorems for processes with semi-Markov switchings are considered.This paper was partly prepared with the support of NFR Grant F-UP 10257-300. 相似文献
198.
In this study we report the levels of 3-methoxy-4-hydroxyphenylglycol, 3,4-dihydroxyphenylacetic acid, homovallinic acid, tryptophan, 5-hydroxyindole-3-acetic acid and serotonin in lumbar cerebrospinal fluid (CSF) from patients with multiple sclerosis, cerebrovascular disease and muscular tension headache the later, as healthy controls. The separation of these substances was performed on a reversed phase column by ion pair high performance liquid chromatography and detection was made by a glassy carbon electrode set at +900 mV vs Ag+/AgCl. The whole separation was achieved within 25 min. Concentrations of all substances (10-1000 pmole/L) were linearly proportional to areas obtained. The system is sensitive, stable and reproducible. The significance of CSF levels of these metabolites from patients groups compared with healthy controls are discussed. 相似文献
199.
V. I. Khromov V. V. Kharlamov A. M. Chekmarev G. A. Andropova B. A. Mamet A. S. Plachinda 《Hyperfine Interactions》1991,67(1-4):565-567
The iron containing corrosion products from water heat-carrier and deposits of the second circuit of the nuclear power plant were investigated by means of absorption Mössbauer spectroscopy. The nonstoichiometric magnetite and paramagnetic (superparamagnetic) iron oxide particles were found to be the main corrosion products. The fraction of the magnetically ordered phase varied in the range 0–100% depending on the location in the second circuit. 相似文献
200.
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. L. Seaman Y. Dalichaouch M. B. Maple J. D. Garrett 《Hyperfine Interactions》1991,64(1-4):517-522
We have performed both zero field and high transverse field measurements at dilution refrigerator temperatures on a number of heavy electron systems, examining the superconducting and magnetic properties of these interesting materials. Among the materials studied to date are UBe13, URu2Si2 and U6Fe. The magnetic field penetration depth in the superconducting state of UBe13 is greater than 10000 Å, as no increase in the transverse field relaxation rate is observed belowT c . A sharp increase in the precession frequency is seen, starting atT c . This frequency shift shows little temperature dependence at low temperature; we found no clear evidence for unconventional superconductivity in this material. Zero field measurements in URu2Si2 show the weak antiferromagnetic transition at 17.5 K. Finally, we we found no clear evidence for unconventional superconductivity in this material. Zero field measurements in URu2Si2 show the weak antiferromagnetic transition at 17.5 K. Finally, we have observed relaxation in high transverse field due to the formation of a flux lattice in U6Fe, a material where the electron effective mass is rather lighter than in other heavy fermion systems. The relaxation exhibits a sharp onset atT c=3.9 K, and is flat at low temperatures as expected for a conventional superconductor. 相似文献