全文获取类型
收费全文 | 39190篇 |
免费 | 1192篇 |
国内免费 | 270篇 |
专业分类
化学 | 27354篇 |
晶体学 | 335篇 |
力学 | 742篇 |
综合类 | 1篇 |
数学 | 6368篇 |
物理学 | 5852篇 |
出版年
2023年 | 180篇 |
2022年 | 344篇 |
2021年 | 463篇 |
2020年 | 642篇 |
2019年 | 633篇 |
2018年 | 436篇 |
2017年 | 406篇 |
2016年 | 998篇 |
2015年 | 892篇 |
2014年 | 1071篇 |
2013年 | 1825篇 |
2012年 | 2306篇 |
2011年 | 2610篇 |
2010年 | 1430篇 |
2009年 | 1259篇 |
2008年 | 2410篇 |
2007年 | 2224篇 |
2006年 | 2254篇 |
2005年 | 2104篇 |
2004年 | 1811篇 |
2003年 | 1505篇 |
2002年 | 1454篇 |
2001年 | 596篇 |
2000年 | 583篇 |
1999年 | 466篇 |
1998年 | 436篇 |
1997年 | 465篇 |
1996年 | 535篇 |
1995年 | 376篇 |
1994年 | 449篇 |
1993年 | 396篇 |
1992年 | 363篇 |
1991年 | 337篇 |
1990年 | 302篇 |
1989年 | 256篇 |
1988年 | 260篇 |
1987年 | 285篇 |
1986年 | 237篇 |
1985年 | 433篇 |
1984年 | 393篇 |
1983年 | 328篇 |
1982年 | 393篇 |
1981年 | 337篇 |
1980年 | 330篇 |
1979年 | 285篇 |
1978年 | 279篇 |
1977年 | 271篇 |
1976年 | 266篇 |
1975年 | 243篇 |
1974年 | 216篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
Tadeusz Balaban Michael O'Carroll Ricardo Schor 《Communications in Mathematical Physics》1989,122(2):233-247
Block renormalization group transformations (RGT) for lattice and continuum Euclidean Fermions in d dimensions are developed using Fermionic integrals with exponential and -function weight functions. For the free field the sequence of actionsD
k
generated by the RGT from D, the Dirac operator, are shown to have exponential decay; uniform ink, after rescaling to the unit lattice. It is shown that the two-point functionD
–1 admits a simple telescopic sum decomposition into fluctuation two-point functions which for the exponential weight RGT have exponential decay. Contrary to RG intuition the sequence of rescaled actions corresponding to the -function RGT do not have uniform exponential decay and we give examples of initial actions in one dimension where this phenomena occurs for the exponenential weight RGT also. 相似文献
162.
163.
A well-known relativistic action at a distance interaction of two unequal masses is altered so as to yield purely Newtonian radial forces with fixed particle rest masses in the system center-of-momentum inertial frame. Although particle masses experience no kinematic mass increase in this frame, speeds are naturally restricted to less than the speed of light. We derive a relation between the center-of-momentum frame total Newtonian energy and the composite rest mass. In a new proper time quantum formalism, we obtain an L2(R4 R4, C) Hilbert space by varying individual particle rest masses. We propose the use of density operators, recognizing that the auxiliary proper time parameter is not an observable. The quantum formalism is applied to our altered version of the relativistic harmonic oscillator. Our generalized coherent states yield four-dimensional wave packets which follow the correct classical world lines. Appendices contain reviews of classical Hamiltonian reparametrization (incorporating our notion of manifest covariance), and a comparison of this work with the literature. 相似文献
164.
165.
Polyazido high-nitrogen compounds: hydrazo- and azo-1,3,5-triazine 总被引:13,自引:0,他引:13
Huynh MH Hiskey MA Hartline EL Montoya DP Gilardi R 《Angewandte Chemie (International ed. in English)》2004,43(37):4924-4928
166.
A diastereoselective [4+2] annulation of vinyl carbodiimides with chiral N-alkyl imines has been developed to access the stereochemically rich tricyclic core of the batzelladine alkaloids. Its application to the asymmetric synthesis of batzelladine D permitted the use of long-range, directed hydrogenation and stereoselective intramolecular iodoamination as additional key steps to establish the remaining stereocenters within the natural product with excellent stereocontrol. 相似文献
167.
Michael Binnewies Marion Jerzembeck Andreas Kornick 《Angewandte Chemie (International ed. in English)》1991,30(7):745-753
One of the modern high technologies which has advanced enormously in the last few years is glass fiber technology. This is used in the manufacture of glass fibers for lighting purposes and for the optical transfer of analog and digital data with a high transfer density. The technical demands made on the glass fibers required for data transfer, the optical waveguides, are extremely high and are already fulfilled to a large extent by industry. At present about four million kilometers of fiber, worth ca. 800 million DM are produced worldwide (10% in the Federal Republic of Germany). Numerous chemical processes take place during the manufacture of optical waveguides. However, in contrast both to the high and constantly growing demands on the quality and to the increasing production volume of such fibers, little is in fact known about the reactions involved. The present article will attempt to develop a picture of the multifarious reactions occurring in the course of this technical process on the basis of literature data and our own studies. 相似文献
168.
Microsatellite structures in the context of human evolution 总被引:2,自引:0,他引:2
Six microsatellite - or short tandem repeat (STR) - systems with uniform repetitive sequences (HumTH01, HumCD4, HumFES/FPS, HumF13B, HumTPO, HumLPL) and three compound repeat systems (HumVWA, HumFIBRA, D21S11) were used, including data from the literature, to determine genetic distances among eight populations worldwide. The TH01- and VWA homologous loci in nonhuman primates (chimpanzees, gorillas, orangutans, rhesus monkeys, ring-tailed lemurs) were compared and found to be shorter than in humans. Microsatellites of lower complexity were most efficient for the separation of major ethnic groups. The loci of higher complexity showed a leveling of the diversity differences among populations, which could be attributed to higher mutation rates. 相似文献
169.
170.
CuAl2Cl8. Preparation and Crystal Structure. Crystals of CuAl2Cl8 have been prepared. Their remission spectrum agrees with that of gaseous CuAl2Cl8. The crystal structure (P21/c;a = 6.614, b = 7.376, c = 12.319 Å; β = 94.11°) shows a molecular lattice with Cu in square planar coordination, which is completed to a stretched octahedron (as in solid CuCl2) by two Cl atoms from neighbour molecules. Al has tetrahedral coordination. 相似文献