全文获取类型
收费全文 | 841篇 |
免费 | 25篇 |
国内免费 | 9篇 |
专业分类
化学 | 502篇 |
晶体学 | 1篇 |
力学 | 17篇 |
数学 | 124篇 |
物理学 | 231篇 |
出版年
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 37篇 |
2012年 | 42篇 |
2011年 | 40篇 |
2010年 | 27篇 |
2009年 | 18篇 |
2008年 | 54篇 |
2007年 | 47篇 |
2006年 | 31篇 |
2005年 | 40篇 |
2004年 | 44篇 |
2003年 | 25篇 |
2002年 | 45篇 |
2001年 | 19篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 18篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1975年 | 11篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1972年 | 5篇 |
1971年 | 4篇 |
排序方式: 共有875条查询结果,搜索用时 0 毫秒
21.
J.R. McDonald 《Chemical physics》1976,13(4):339-347
The fluorescence emission spectrum and analysis of NSF vapor is presented. Single vibronic level excitation near the S1 origin gives rise to a 10 μs radiative decay. The fluorescence lifetime for excitation of levels with ? 4500 cm?1 excess vibrational energy becomes controlled by a unimolecular radiationless process which is likely photodissociation; the dependence of this radiationless rate on energy and vibrational mode is investigated. The perturbations resulting from coupling of zero-order S1 states with other vibronic levels which control the excited state dynamics of SO2 are apparently not operative for NSF. Attempts are made to rationalize the grossly different dynamic behavior of the S1 levels of these two otherwise very similar systems. 相似文献
22.
23.
24.
Xin Chen Aleksandra M. Krajewska Dr. Cormac McGuinness Amy Lynes David McAteer Nina Berner Prof. Georg Duesberg Prof. Jonathan N. Coleman Prof. Aidan R. McDonald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):984-992
Covalently tethering photosensitizers to catalytically active 1T-MoS2 surfaces holds great promise for the solar-driven hydrogen evolution reaction (HER). Herein, we report the preparation of two new RuII-complex-functionalized MoS2 hybrids [RuII(bpy)2(phen)]-MoS2 and [RuII(bpy)2(py)Cl]-MoS2. The influence of covalent functionalization of chemically exfoliated 1T-MoS2 with coordinating ligands and RuII complexes on the HER activity and photo-electrochemical performance of this dye-sensitized system was studied systematically. We find that the photo-electrochemical performance of this RuII-complex-sensitized MoS2 system is highly dependent on the surface extent of photosensitizers and the catalytic activity of functionalized MoS2. The latter was strongly affected by the number and the kind of functional groups. Our results underline the tunability of the photovoltage generation in this dye-sensitized MoS2 system by manipulation of the surface functionalities, which provides a practical guidance for smart design of future dye-sensitized MoS2 hydrogen production devices towards improved the photofuel conversion efficiency. 相似文献
25.
Internal pressurization testing at room temperature was performed to evaluate the effect of flame-spraying aluminum-12silicon on the leakage behavior of fibre-reinforced composite tubes fabricated by filament winding, and covered with garnet sand. A group of specimens were completely coated with flame-sprayed metal particles and another set remained uncoated. t-tests were conducted at a significance level of α = 0.05 to analyze the effect of the coating on the leakage behavior of the specimens. Ultraviolet imaging was used to illustrate a characteristic leakage pattern of the composite tubes. Coated specimens exhibited slightly higher mean leakage and burst pressures than the uncoated specimens. The t-test results provided strong statistical evidence that the flame spraying process employed did not damage the filament wound tubes covered with garnet sand. 相似文献
26.
27.
Charles J. McDonald 《Journal of Dispersion Science and Technology》2013,34(3-4):365-392
The structure of a 70/30 ethyl acrylate-acrylamide latex made in a semi-continuous process with surfactant has been investigated. The molar composition and relative concentration of the polymers in the serum phase, on the surface and in the particle were characterized by coupling a filtration procedure, serum replacement, with carbon-13 NMR spectroscopy. The development of polymer in the different phases could be monitored by taking samples at timed intervals during the polymerization. Post-treatment of the latex with sodium hydroxide selectively hydrolyzed the copolymerized ethyl acrylate in the serum and on the surface. By measurement of spin lattice relaxation times it was possible to estimate surface concentration of oligomeric polymer 相似文献
28.
29.
Ronald G. Cavell Chih Y. Wong Robert McDonald 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Neutral hexacoordinate phosphorus(V) compounds of a number of univalent bidentate ligands are known.l,2 The silylated forms of tridentate, dianionic Schiff base ligands: N-(2-hydroxyphenyl)salicylideneamine H2LI, N-(4-tert-butyl-2-hydroxyphenyl)-salicylideneamine H2LII, N-(2-hydroxy-4-nitrophenyl)salicylidene-amine H2LIII, and 2,2′-azodiphenol H2LIV gave, with halogeno- and (trifluoromethyl)halogenophosphoranes, neutral hexa-coordinate derivatives with bis-chelate structures. The ligands form bicyclic five- and six-membered chelate rings in a meridional conformation, with two P-O bonds and one N→P donor bond. Hexacoordinate structures were evidenced by high-field 31P NMR chemical shifts (-136 to -148 ppm), characteristic J PF coupling patterns and was further substantiated by crystal structures of Cl3LII (A) and F3PLII (B). 相似文献
30.
Paolo Pirovano Adriana M. Magherusan Ciara McGlynn Andrew Ure Amy Lynes Dr. Aidan R. McDonald 《Angewandte Chemie (International ed. in English)》2014,53(23):5946-5950
Metal‐bound superoxide intermediates are often implicated as electrophilic oxidants in dioxygen‐activating metalloenzymes. In the nonheme iron α‐ketoglutarate dependent oxygenases and pterin‐dependent hydroxylases, however, FeIII–superoxide intermediates are postulated to react by nucleophilic attack on electrophilic carbon atoms. By reacting a CuII–superoxide complex ( 1 ) with acyl chloride substrates, we have found that a metal–superoxide complex can be a very reactive nucleophile. Furthermore, 1 was found to be an efficient nucleophilic deformylating reagent, capable of Baeyer–Villiger oxidation of a number of aldehyde substrates. The observed nucleophilic chemistry represents a new domain for metal–superoxide reactivity. Our observations provide support for the postulated role of metal–superoxide intermediates in nonheme iron α‐ketoglutarate dependent and pterin‐dependent enzymes. 相似文献