全文获取类型
收费全文 | 779篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 407篇 |
晶体学 | 42篇 |
力学 | 40篇 |
数学 | 95篇 |
物理学 | 204篇 |
出版年
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2015年 | 6篇 |
2014年 | 24篇 |
2013年 | 57篇 |
2012年 | 35篇 |
2011年 | 38篇 |
2010年 | 31篇 |
2009年 | 22篇 |
2008年 | 14篇 |
2007年 | 16篇 |
2006年 | 22篇 |
2005年 | 27篇 |
2004年 | 14篇 |
2003年 | 15篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 11篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1990年 | 6篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 20篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 29篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1972年 | 9篇 |
1970年 | 7篇 |
1964年 | 6篇 |
排序方式: 共有788条查询结果,搜索用时 31 毫秒
11.
H. K. Reimschuesel J. Marti N. S. Murthy 《Journal of polymer science. Part A, Polymer chemistry》1988,26(1):43-59
Copolymers of ethylene and chlorotrifluoroethylene that contain small amounts of units derived from perfluorohexylethylene show improved resistance of thermal stress cracking. This is a consequence of effects of these units on structural parameters of both the crystalline and amorphous phases. Those of the crystalline phase entail growth and organization of lamellae, whereas those of the amorphous phase are related to conformation and packing of polymer chains. The crystalline phase consists exclusively of alternately arranged units of ethylene and chlorotrifluoroethylene. The amorphous phase is characterized by chain segments composed of randomly distributed units derived from ethylene, chlorotrifluoroethylene, pairs of these two units, and units derived from perfluorohexylethylene. 相似文献
12.
13.
Synthesis and Langmuir studies of bivalent and monovalent alpha-D-mannopyranosides with lectin Con A
Bandaru NM Sampath S Jayaraman N 《Langmuir : the ACS journal of surfaces and colloids》2005,21(21):9591-9596
Highly avid interaction between carbohydrate ligands and lectin receptors nominally requires the ligand presentation in a clustered form. We present herein an approach involving Langmuir monolayer formation of the sugar ligands and the assessment of their lectin binding at the air-water interface. Bivalent alpha-D-mannopyranoside containing the glycolipid ligand was used to study its binding profiles with lectin Con A, in comparison to the corresponding monovalent glycolipid. In addition to the bivalent and monovalent nature of the glycolipid ligands at the molecular level, the ligand densities at the monolayer level were varied with the aid of a nonsugar lipid molecule so as to obtain mixed monolayers with various sugar-nonsugar ratios. Lectin binding of bivalent and monovalent ligands at different ratios was monitored by differential changes in the surface area per molecule of the mixed monolayer, with and without the lectin. The present study shows that maximal binding of the lectin to the bivalent ligand occurs at lower sugar densities at the interface ( approximately 10% sugar in the mixed monolayer) than for that of the monovalent ligand ( approximately 20% sugar in the mixed monolayer). It is observed that complete coverage of the monolayer with only the sugar ligands does not allow all of the sugars to be functionally active. 相似文献
14.
P. S. Verma T. Venkateshwar Rao A. Jayaraman P. S. N. Murthy G. C. Joshi 《Fresenius' Journal of Analytical Chemistry》1994,348(11):742-744
The Fe(III)-EDTA complex reacts with sulfide ion in a fast electron transfer reaction, oxidising the latter to elemental sulfur and getting itself reduced to Fe(II). The reaction has been developed for the quantitative estimation of sulfide ion by titration against the Fe(III)-EDTA complex, measuring the redox potential of the system. Repeated use of a given quantity of the complex solution by the process of regeneration has been demonstrated. The possibility of its practical application in liquid phase oxidation processes of recovering sulfur from H2S is emphasized. 相似文献
15.
Murthy MB Daya Sagar BS Patil RL 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(6):1277-1280
The electronic absorption spectra of eight substituted acetic acids have been measured at room temperature in several solvents. The ground state dipole moments are evaluated experimentally for these molecules. These ground state values are used in conjunction with the spectral results to evaluate their first electronically excited state dipole moments. For all the molecules investigated here the dipole moments in the excited state are higher than their ground state values. 相似文献
16.
S. S. Krishnamurthy P. Ramabrahmam A. R. Vasudeva Murthy R. A. Shaw M. Woods 《无机化学与普通化学杂志》1985,522(3):226-234
The reactions of pentachloro(2′, 2′, 2′-triphenylphosphazen-1′-yl)cyclotriphosphazene, N3P3Cl5(NPPh3), with primary and secondary amines have been investigated using diethyl ether, methyl cyanid or benzene as the solvent. The structures of the products obtained, N3P3Cl5minus;nRn(NPPh3) [n = 1, R = NHMe, NHBut, NMe2, NC5H10, NEt2; n = 2, R = NMe2, NC5H10, NEt2; n = 3, R = NMe2, NHBut; n = 5, R = NMe2] are elucidated by 1H and 31P NMR spectroscopy. The ? NPPh3 substituent exerts a pronounced geminal directing influence on incoming secondary amino nucleophiles; compounds containing a ≡ PCl(NPPh3) group are not formed at the bis and subsequent stages of chlorine replacement. The reactions that involve primary amines follow the pattern established for the analogous reactions of hexachlorocyclotriphosphazene. The effect of solvent and possible mechanism(s) are discussed. 相似文献
17.
18.
The quantum density of states of the Henon-Heiles potential displays a pronounced beating pattern. This has been explained by the interference of three isolated classical periodic orbits with nearby actions and periods. A singular magnetic flux line, passing through the origin, drastically alters the beats even though the classical Lagrangian equations of motion remain unchanged. Some of the changes can be easily understood in terms of the Aharonov-Bohm effect. However, we find that the standard periodic orbit theory does not reproduce the diffraction-like quantum effects on those classical orbits which intersect the singular flux line, and argue that corrections of relative order variant Planck's over 2pi are necessary to describe these effects. We also discuss the changes in the distribution of nearest-neighbor spacings in the eigenvalue spectrum, brought about by the flux line. (c) 1995 American Institute of Physics. 相似文献
19.
20.
The complete force field for carbon suboxide has been evaluated. The optimum geometry, stretching and interaction force constants are obtained from a combination of the CNDO/force molecular orbital method and the compliance constant formalism. 相似文献