全文获取类型
收费全文 | 1580篇 |
免费 | 32篇 |
国内免费 | 3篇 |
专业分类
化学 | 1082篇 |
晶体学 | 24篇 |
力学 | 24篇 |
数学 | 92篇 |
物理学 | 393篇 |
出版年
2021年 | 11篇 |
2020年 | 19篇 |
2019年 | 21篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 28篇 |
2015年 | 29篇 |
2014年 | 27篇 |
2013年 | 68篇 |
2012年 | 70篇 |
2011年 | 76篇 |
2010年 | 52篇 |
2009年 | 46篇 |
2008年 | 103篇 |
2007年 | 91篇 |
2006年 | 95篇 |
2005年 | 99篇 |
2004年 | 71篇 |
2003年 | 63篇 |
2002年 | 80篇 |
2001年 | 38篇 |
2000年 | 48篇 |
1999年 | 19篇 |
1998年 | 19篇 |
1997年 | 23篇 |
1996年 | 23篇 |
1995年 | 27篇 |
1994年 | 21篇 |
1993年 | 15篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 22篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1974年 | 8篇 |
1973年 | 11篇 |
1969年 | 6篇 |
1967年 | 7篇 |
1966年 | 5篇 |
排序方式: 共有1615条查询结果,搜索用时 125 毫秒
31.
K. Nomura 《Graphs and Combinatorics》1995,11(2):139-140
Let be a bipartite distance-regular graph of even valencyk. Let us consider the intersection array modulo 2, which would become Lett be the length of any series of (1, 0, 1)'s witht > 1. Thent + 1|r
1 + 1, withr
1 the length of the first series. 相似文献
32.
Takaaki Nomura 《Annals of Global Analysis and Geometry》1994,12(1):237-260
We study the set of rankp idempotents in a topologically simple Hilbert Jordan algebra (JH-algebra for short). To produce the differential geometric structure on, we establish Jordan algebraic results concerning the structure of some two-generator subalgebras. We identify geodesics, the Riemannian distance and the sectional curvature of by using the Jordan algebraic structure. 相似文献
33.
In a previous paper we studied the Young's and shear modulus of a high-angle twist grain boundary (5) in Cu, using the EAM, and related it to the uniaxial strain derivatives of single crystals. In this paper, we discuss elastic properties of ten additional twist grain boundaries, from 8.8–43.6°. The monolayer Young's modulus at each boundary was calculated and found to be 20–50% higher than the bulk value for all eleven boundaries for both csl and type1 structures. The monolayer shear modulus at each boundary was calculated and found to be 93–98% lower than the bulk value for six grain boundaries with csl structure and found to decrease with increasing twist angle. The critical shear stress was also calculated for eleven boundaries with csl structure and found to roughly decrease with increasing twist angle. 相似文献
34.
Mamoru Sato Yukiteru Katsube Masaaki Katai Jun' ichi Katakawa Tadahiro Tetsumi 《Journal of chemical crystallography》1996,26(2):153-156
The crystal and molecular structure of a grayanotoxin III derivative, 6-0-acetylgrayanotoxin III is presented. The crystal is orthorhombic, space group P212121, witha=15.582(3),b=21.304(3),c=6.339(3)Å,V=2104(1) Å3
Z=4. The structure was solved by direct methods and refined by full matrix least-squares methods to a finalR=0.047 for 1763 independent reflections withF
0>3 (F
0) The molecule is based on a tetracyclic structure consisting of two five-membered, one six-membered, and one seven-membered ring with various conformations. 相似文献
35.
Akito Nomura 《manuscripta mathematica》1993,79(1):379-390
LetL/k be a finite Galois extension with Galois groupG, and
a group extension. We study the existence of the Galois extensionM/L/k such that the canonical projection Gal(M/k)→Gal(L/k) coincides with the given homomorphismj:E→G and thatM/L is unramified. 相似文献
36.
Phenols are deprotected with weak bases from their tert-butoxycarbonyl (Boc) derivatives. Boc deprotection with bases can avoid side reactions during the deprotection with acids. We note the lability of the Boc to bases and are able to utilize it as a new cleavage condition for synthetic studies. 相似文献
37.
Yotaro Morishima Shigeki Nomura Mikiharu Kamachi 《Journal of polymer science. Part A, Polymer chemistry》1994,32(16):3141-3146
3,7-Diethyl- 10-phenylphenothiazine (DEPPT), a phenothiazine derivative whose 3,7- and 10-positions are blocked, was synthesized. Potentiostatic electrolysis of DEPPT in acetonitrile (ACN) in the presence of 0.1M of LiClO4 at 0.7 V (vs. Ag/Ag/Cl) yielded the stable cation radical of DEPPT (DEPPT+·) which was characterized by cyclic voltammetry, UV-visible spectroscopy, and ESR spectrometry. Stable cation radicals of 10-phenylphenothiazine and 3,7-diethyl-10-methylphenothiazine were also prepared. The cationic polymerization of n-butyl vinyl ether was initiated by these cation radicals, including DEPPT·+. The electron transfer mechanism for the initiation step, which we proposed previously, was supported by the fact that DEPPT·+ was capable of initiating the polymerization; dimerization of DEPPT·+ by releasing protons is precluded because 3,7- and 10-positions are all blocked. © 1994 John Wiley & Sons, Inc. 相似文献
38.
Syed Mashhood Ali Santosh Kumar Upadhyay Arti Maheshwari Mamoru Koketsu 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):325-328
1H NMR spectroscopic study of fluvastatin sodium (FLU), β-Cyclodextrin (β-CD) and their mixtures confirmed the formation of FLU/β-CD inclusion complex in solution. The stoichiometry of the complex was determined to be 1:1 and the overall binding constant (K
s) was calculated to be 340 M−1. Two dimensional COSY, ROESY and DEPTO experiments were performed for the unambiguous assignment of aromatic proton resonances and it was found that two isomeric forms of FLU are present in solution. It was confirmed with the help of ROESY spectral data that only F-substituted aromatic ring penetrates the β-CD cavity and there is chiral differentiation by the β-CD as one of the isomer binds more strongly, which is indicated by the intensity of correlation peaks. The mode of penetration of the guest into the β-CD cavity was also established and structure of the complex has been proposed. 相似文献
39.
Oseki Y Fujitsuka M Hara M Cai X Ie Y Aso Y Majima T 《The journal of physical chemistry. B》2005,109(21):10695-10698
Photophysical properties of oligo(2,3-thienyleneethynylene)s (nTE, n denotes the number of thiophene rings, n = 2, 3) in benzene were investigated using steady-state, time-resolved fluorescence, and transient absorption spectroscopies. For 2TE, generation of the radiative S2 and nonradiative S1 states was confirmed. Upon excitation, the S2 state was initially generated and deactivated to the S1 state within 10 ps. The S1 state exhibited the transient absorption band at 470 nm, of which the lifetime was estimated to be 5.3 ns. In the case of 3TE, on the other hand, it was revealed that the radiative S1 state with a transient absorption peak at 650 nm was generated upon excitation. The T1 states of nTE were generated from the S1 states. The quantum yields were estimated to be 0.52 and 0.54 for 2TE and 3TE, respectively. Extremely fast reactions in the higher triplet excited state were indicated for both 2TE and 3TE. 相似文献
40.
Tachikawa T Tojo S Fujitsuka M Majima T 《Langmuir : the ACS journal of surfaces and colloids》2004,20(22):9441-9444
The one-electron reduction of methyl viologen (MV(2+)) mediated by the carbon dioxide radical anion (CO(2)(*-)) during photocatalytic reactions in a colloidal TiO(2) aqueous solution (pH 2) has been investigated by time-resolved absorption spectroscopy. The formation of MV(*+) generated from the one-electron reduction reaction with CO(2)(*-), which is generated from the one-electron oxidation reactions with the photogenerated holes (h(+)), was directly observed. The spectral features of the photogenerated charge carriers and the kinetic analysis of the formation process of MV(*+) revealed that the CO(2)(*-), desorbed from the surface, reacts with MV(2+) via a homogeneous electron-transfer process in the bulk solution. 相似文献