全文获取类型
收费全文 | 35050篇 |
免费 | 1415篇 |
国内免费 | 1447篇 |
专业分类
化学 | 22274篇 |
晶体学 | 286篇 |
力学 | 709篇 |
综合类 | 11篇 |
数学 | 6518篇 |
物理学 | 8114篇 |
出版年
2023年 | 213篇 |
2021年 | 580篇 |
2020年 | 503篇 |
2019年 | 525篇 |
2018年 | 632篇 |
2017年 | 629篇 |
2016年 | 1280篇 |
2015年 | 1049篇 |
2014年 | 1173篇 |
2013年 | 2616篇 |
2012年 | 2214篇 |
2011年 | 2543篇 |
2010年 | 1489篇 |
2009年 | 1652篇 |
2008年 | 1769篇 |
2007年 | 1669篇 |
2006年 | 1406篇 |
2005年 | 1262篇 |
2004年 | 1573篇 |
2003年 | 1172篇 |
2002年 | 1107篇 |
2001年 | 654篇 |
2000年 | 584篇 |
1999年 | 473篇 |
1998年 | 424篇 |
1997年 | 405篇 |
1996年 | 391篇 |
1995年 | 344篇 |
1994年 | 283篇 |
1993年 | 307篇 |
1992年 | 295篇 |
1991年 | 232篇 |
1990年 | 253篇 |
1989年 | 224篇 |
1988年 | 230篇 |
1987年 | 213篇 |
1986年 | 221篇 |
1985年 | 307篇 |
1984年 | 312篇 |
1983年 | 251篇 |
1982年 | 255篇 |
1981年 | 241篇 |
1980年 | 237篇 |
1979年 | 218篇 |
1978年 | 240篇 |
1977年 | 217篇 |
1976年 | 214篇 |
1975年 | 194篇 |
1974年 | 215篇 |
1973年 | 186篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
81.
82.
The new techniques and ideas in quantum interferometry with neutrons, photons, atoms, electrons, and Bose condensates that fluorished in the last two decades have influenced in a decisive way the thinking and the research in the foundations and interpretation of quantum mechanics. The controversies existing among different schools on the reality of matter waves of quantum theory, the postulates of quantum measurement theory, and the (in)completeness of quantum mechanics have to be approached now in a new way. Our argumentation follows the spirit of the Paris school. 相似文献
83.
The standard model on non-commutative space-time 总被引:1,自引:0,他引:1
X. Calmet B. Jurčo P. Schupp J. Wess M. Wohlgenannt 《The European Physical Journal C - Particles and Fields》2002,23(2):363-376
We consider the standard model on a non-commutative space and expand the action in the non-commutativity parameter . No new particles are introduced; the structure group is . We derive the leading order action. At zeroth order the action coincides with the ordinary standard model. At leading order
in we find new vertices which are absent in the standard model on commutative space-time. The most striking features are couplings
between quarks, gluons and electroweak bosons and many new vertices in the charged and neutral currents. We find that parity
is violated in non-commutative QCD. The Higgs mechanism can be applied. QED is not deformed in the minimal version of the
NCSM to the order considered.
Received: 29 November 2001 / Published online: 25 January 2002 相似文献
84.
Alberto Elduque José Marí a Pé rez 《Proceedings of the American Mathematical Society》1997,125(8):2207-2216
Composition algebras with a unit element constitute a well-known class of algebras. In this paper, those composition algebras with a one-sided unit element are characterized and examples are given of arbitrary infinite dimension.
85.
The main aim of this paper is the calculation of the dimension of certain atomic amalgams. These consist of finite Boolean algebras (blocks) pasted together in such a way that a pair of blocks intersects either trivially in the bounds, or the intersection consists of the bounds, an atom, and its complement. 相似文献
86.
F. Rubio F. García H. D. Burrows A. A. C. C. Pais A. J. M. Valente M. J. Tapia J. M. García 《Journal of polymer science. Part A, Polymer chemistry》2007,45(9):1788-1799
The interaction between trivalent lanthanide ions and poly(1,4,7,10,13‐pentaoxacyclopentadecan‐2‐yl‐methyl methacrylate), PCR5, in aqueous solution and in the solid state have been studied. In aqueous solution, evidence of a weak interaction between the lanthanides and PCR5 comes from the small red shift of the Ce(III) emission spectra and the slight broadening of the Gd(III) EPR spectra. From the Tb(III) lifetimes in the presence of H2O and D2O the loss of one or two water coordinated molecules is confirmed when Tb(III) is bound to PCR5. An association constant of the order of 200 M?1 was obtained for a 1:1 (lanthanide:15‐crown‐5) complex from the shift of the polymer NMR signals induced by Tb(III). A similar association constant is obtained from the differences of the molar conductivity of Ce(III) solution at various concentrations in presence and absence of PCR5. When Tb(III) is adsorbed on PCR5 membranes, lifetime experiments in H2O and D2O confirm the loss of 5 or 6 water coordinated molecules indicating that in solid state the lanthanide(III)‐PCR5 interaction is stronger than in solution. The adsorption of Ce(III) in PCR5 membranes shows a Langmuir type isotherm, from which an equilibrium constant of 39 M?1 has been calculated. SEM shows that the membrane morphology is not much affected by lanthanide adsorption. Support for lanthanide ion–crown interactions comes from ab initio calculations on 15‐crown‐5/La(III) complex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1788–1799, 2007 相似文献
87.
N. Raju T. Špaček J. Ježek I. M. Caminiti F. Leinisch K. Hideg P. Ježek W. E. Trommer 《Applied magnetic resonance》2006,30(3-4):373-383
Electron paramagnetic resonance (EPR) spectroscopy of spin-labeled fatty acids was used to investigate their interaction withEscherichia coli-expressed human mitochondrial uncoupling protein UCP2 refolded from inclusion bodies in nonaethylene glycol monododecyl ether (C12E9) micelles. 5-DOXYL-stearic acid and 4-PROXYL-palmitic acid bound to UCP2 exhibited additional clearly separated h+1I, h?1I “immobile” peaks in the low- and high-field region, respectively, separated by 42 and 44 Gauss, and extensively reduced h+1M, h?1M “mobile” peaks, separated by about 30 G, whereas with 7-DOXYL-stearic acid the I and M peaks were smoothed together into one wide peak. Competition of 4-PROXYL-palmitic acid with added palmitic acid, arachidonic acid, and all-cis-8,11,14-eicosatrienoic acid and of 7-DOXYL-stearic acid with arachidonic acid was indicated by the disappearance of the h+1I, h?1I “immobile” peaks, whereas redistribution in micelles without protein was indicated by the rising of the h+1M, h?1M “mobile” peaks. In conclusion, a competition of palmitic, arachidonic, and eicosatrienoic acid within a putative fatty acid binding site was observed for mitochondrial uncoupling protein UCP2. This finding together with the observation of EPR spectra of highly immobilized probes exclusively in the presence of the recombinant UCP2 suggest the existence of a fatty acid binding site on UCP2 which is a prerequisite of the fatty acid cycling mechanism as previously postulated for UCP1. 相似文献
88.
D.L. Skuratov Yu.L. Ratis I.A. Selezneva J. Pérez P. Fernández de Córdoba J.F. Urchueguía 《Applied Mathematical Modelling》2007
This paper deals with modelling the workpiece temperature field produced during the grinding process. The proposed model is given in terms of a two-dimensional boundary-value problem where the interdependence among the grinding wheel, the workpiece and the coolant is described by two variable functions in the boundary condition. An explicit integral form solution is constructed using the Laplace and Fourier transforms and the Green’s function method. 相似文献
89.
On‐line coupling of LC and ICP‐MS has been used for fractionation and detection of species of Cu, Fe, I, Se and Zn in human serum. It has been shown that anion exchange chromatography provided better separation capability (both intra‐ and inter‐element) than size‐exclusion chromatography. The mobile phases for ion exchange chromatography consisted of Tris–HNO3 buffer and ammonium salt (nitrate, acetate or formate). Formate was found to be the best mobile phase counter ion, enabling good chromatographic separation, and is acceptable for mass spectrometry too. The quantitative evaluation of element concentrations adhering to individual fractions was performed by the peak area normalization method. The repeatability of results ranged from 3 to 15% (depending on the element concentration level) and represented the main part of the result uncertainty. The accuracy of Cu and Zn fraction determinations was confirmed by comparison with the isotope dilution technique. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
90.
Received December 31, 2001 / Published online May 21, 2002 相似文献