全文获取类型
收费全文 | 437篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 320篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 19篇 |
物理学 | 102篇 |
出版年
2022年 | 3篇 |
2019年 | 4篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 23篇 |
2012年 | 12篇 |
2011年 | 21篇 |
2010年 | 14篇 |
2009年 | 7篇 |
2008年 | 18篇 |
2007年 | 22篇 |
2006年 | 17篇 |
2005年 | 28篇 |
2004年 | 20篇 |
2003年 | 13篇 |
2002年 | 10篇 |
2001年 | 16篇 |
2000年 | 16篇 |
1999年 | 6篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 15篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1972年 | 3篇 |
1969年 | 4篇 |
1967年 | 2篇 |
1928年 | 2篇 |
1910年 | 2篇 |
排序方式: 共有444条查询结果,搜索用时 687 毫秒
61.
T. Nishi 《Journal of Polymer Science.Polymer Physics》1974,12(4):685-693
The spin–spin relaxation time T2 and the fraction of short T2 component for composites of natural rubber with carbon black prepared under various conditions have been measured by pulsed NMR. Effect of swelling with a solvent (CCl4), carbon black species (SAF, HAF, SRF) with different surface areas, and different initial carbon black loadings (35, 50, 70 phr) have been determined. Molecular motion in the rubber phase not in the immediate vicinity of the carbon black surface increases rapidly with increasing solvent concentration, yet it is still slightly restricted compared to rubber with solvent alone. On the other hand, molecular motion in the immobilized layer around carbon black and the fraction rubber in that layer are not affected by the solvent. This indicates strong restriction of molecular motion of polymers at the surface. For estimation of the thickness of the immobilized layer, the necessity of using an appropriate measure of surface area accessible to polymer molecules is pointed out. The degree of immobilization in the layer and the thickness of the layer do not vary appreciably with the nature of carbon black or the initial loading of carbon black. 相似文献
62.
63.
Haruko Okamura 《Journal of Combinatorial Theory, Series B》1984,37(2):151-172
Mader proved that for every k-edge-connected graph G (k ≥ 4), there exists a path joining two given vertices such that the subgraph obtained from G by deleting the edges of the path is (k - 2)-edge-connected. A generalization of this and a sufficient condition for existance of 3, 4, or 5 terminus k edge-disjoint paths in graphs are given. 相似文献
64.
Mikio Yagi Nobuyuki Nishi Minoru Kinoshita Saburo Nagakura 《Chemical physics letters》1976,39(2):240-244
Using microwave induced delayed phosphorescence techniques we determined the populating and depopulating rate constants for the individual spin-sublevels of the phosphorescent states of tetracyanobenzene (TCNB) and its charge-transfer complexes with benzene and hexamethylbenzene (HMB) in n-hexane at 1.25 K. It was shown that the non-radiative decay process from the shortest lifetime sublevel is most responsible for the previously observed shortening in the phosphorescence lifetime of the TCNBHMB complex. 相似文献
65.
66.
Summary A reversed-phase high-performance liquid chromatographic (HPLC) method was developed to determine the optical purity of denopamine, which is a new cardiotonic agent having an asymmetric carbon in a molecule. The enantiomers were converted to diastereomeric thiourea derivatives using 2,3,4,6-Tetra-O-acetyl--D-glucopyranosyl isothiocyanate (GITC) reagent. Separation of the enantiomers of denopamine as diastereomers was successfully achieved by reversed-phase HPLC within 10 min using an ODS column and UV detection. Derivatization of denopamine proceeded rapidly under the alkaline conditions and the ambient temperature. This method was applied to the determination of the optical purity of denopamine drug substances and those in tablets. The favorable UV absorption of the derivatives enabled the optical antipode to be determined down to the 0.2% level. 相似文献
67.
Masahiro Kawasaki Kazuo Kasatani Hiroyasu Sato Hisanori Shinohara Nobuyuki Nishi 《Chemical physics》1984,88(1):135-142
Molecular beams of halogenated hydrocarbons containing chlorine and bromine atoms were photodissociated using an excimer laser at 193 nm. Molecules photodissociated were HCCBr, HCCCH2Br, HCCCH2Cl, CH3Cl, C2H5Cl and i-C3H7Cl. The time-of-flight distributions of the photofragments were measured in order to study the primary processes and the dissociation dynamics. Generalizations consistent with the data are that atomic products (RX → R + X) result from direct dissociation of the CX repulsive singlet state, molecular elimination (RX → R′ + HX) is a result of a crossover to the ground state and triplet states are involved in the photodissociation of alkyne compounds. 相似文献
68.
Akihiro Nishi 《Annals of the Institute of Statistical Mathematics》1977,29(1):433-444
Summary This paper is concerned with probabilities (error probabilities), caused by misclassification, of linear classification procedures
(linear procedures) between two categories, whose mean vectors and covariance matrices are assumed to be known, while the
distribution of each category may well be continuous or discrete. The tightest upper bounds on the largest of two kinds of
error probability of each linear procedure and on the expected error probability for any apriori probabilities are obtained.
Moreover in some cases of interest, theoptimal linear procedure (in the sense of attaining the infimum out of all the upper bounds) is given. 相似文献
69.
The emission spectra and its time decay in PbCl2 at low temperature are reported. Three emission bands lying at 3.81 (uv), 2.93 (blue) and 2.60 eV are found for the photo-excitation in the intrinsic absorption region, at 4.2 K. An exponential decay with decay time of 11.4 μs is observed for the uv emission. For the blue emission two kinds of time decay spectra are observed: a second order process below 10 K and an exponential decay above 14 K. The mechanisms of these emission are discussed by taking into account the above results. 相似文献
70.
During the course of the study of the hydrothermal stability of alanine oligopeptides, a small amount of oligopeptides longer than the starting oligopeptides was found in the reaction products. On the basis of this unexpected finding and the investigation of the reaction mechanism, the elongation of oligopeptides using (Ala)3, (Ala)4, and (Ala)5 was attempted in aqueous solution at 275-310 degrees C within the second time range using a microflow reactor system. The elongation of (Ala)4 and (Ala)5 succeeded in the presence of an excess amount of Ala monomer. This is probably due to the fact that the elongation rate is competitive or somewhat faster than the degradation of peptide bonding. On the contrary, the elongation of (Ala)3 was not possible since it was immediately converted to diketopiperazine. 相似文献