全文获取类型
收费全文 | 648篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 324篇 |
晶体学 | 4篇 |
力学 | 33篇 |
数学 | 71篇 |
物理学 | 223篇 |
出版年
2021年 | 4篇 |
2020年 | 5篇 |
2018年 | 8篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 13篇 |
2013年 | 30篇 |
2012年 | 25篇 |
2011年 | 43篇 |
2010年 | 19篇 |
2009年 | 16篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 28篇 |
2005年 | 22篇 |
2004年 | 30篇 |
2003年 | 24篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 17篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1977年 | 5篇 |
1976年 | 13篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1968年 | 4篇 |
1966年 | 4篇 |
排序方式: 共有655条查询结果,搜索用时 46 毫秒
1.
We study the number of determining modes necessary for continuous data assimilation in the two-dimensional incompressible Navier–Stokes equations. Our focus is on how the spatial structure of the body forcing affects the rate of continuous data assimilation and the number of determining modes. We treat this problem analytically by proving a convergence result depending on the H
–1 norm of f and computationally by considering a family of forcing functions with identical Grashof numbers that are supported on different annuli in Fourier space. The rate of continuous data assimilation and the number of determining modes is shown to depend strongly on the length scales present in the forcing. 相似文献
2.
There is a high correlation between molecular surface area (TSA) of triorganotin and triorganolead compounds and their toxicity towards a bacterium (Escherichia coli) and an alga (Selenastrum capricornutum). Parallel attempts to correlate other Group IVA organometals incorporating silicon or germanium were unsuccessful. It was further demonstrated, however, that a high correlation was obtainable between certain series of compounds with the same organic substituent but different metal centers involving all Group IVA elements. In both instances, the inability to obtain a quantitative structure-activity relationship (QSAR) for all systems studied appears to be a function of the solubility of the compounds. While organotin TSA values have been found to correlate well with their toxicities toward various organisms, this study clearly suggests that this type of QSAR can be readily extended to include other organometal systems, provided that there is no solubility problem and the toxicity is a function of the hydrophobicity of the organometal compounds. 相似文献
3.
4.
5.
6.
7.
Abstract— The excitation spectrum for bacteriochlorophyll b fluorescence, the action spectrum for cytochrome-553 oxidation, and the action spectrum for P-985 bleaching are compared to the absorption (1-T) spectrum of a Rhodopseudomonas sp. NHTC 133 extract over the range 770 to 930 mμ. These spectra show that a minor pigment P-830 is more effective in sensitizing cytochrome oxidation and P-985 bleaching than in exciting fluorescence of Bchl b. These results are consistent with the proposal that P-830 is a form of Bchl b in special relation to the reaction center pigment P-985. 相似文献
8.
Abstract— Photohydrogen production, 200-700 μmol H2 h?1 (mg bacteriochlorophyll a)?1 has been obtained in a system containing unit membrane vesicles (Complex I) from the green photosynthetic bacterium Chiorobium limicola f. thiosulfatophilum, ascorbate, N,N,N′,N′-tetramethyl-p-phenylene-diamine, dithioerythritol, an oxygen scavenging mixture, either methyl viologen (MV) or clostridial ferredoxin (CPS Fd) as electron carrier, and either CPS hydrogenase or platinum asbestos as catalyst. All components are necessary for maximum activity, and spinach Fd cannot be substituted for CPS Fd. Higher rates of photohydrogen production are obtained using MV or CPS Fd with hydrogenase than with MV and Pt asbestos. The highest quantum efficiencies (7–10% at 0.2–0.9 mW absorbed light and over 20% at lower light) were obtained with CPS Fd, hydrogenase and non-saturating 812 nm light. With saturating white light, however, rates of photohydrogen production varied relatively little among the various combinations of electron carrier and catalyst tested. The reaction rate is unaffected by 0.03% Triton X-100, and is insensitive to treatment with antimycin a or m-chloro-carbonyl cyanide phenylhydrazone. This indicates that neither electron flow through an endogenous cyclic chain, nor maintenance of a proton gradient are involved in this process. 相似文献
9.
Recent research has demonstrated that in a simulated flue gas stream containing NO(2) and SO(2) elemental mercury is initially captured on a carbon or manganese oxide sorbent. After approximately an hour, however, mercury breaks through relatively rapidly, and the volatile form of mercury emitted is an oxidized species. The volatile mercury species emitted from a granular MnO(2) sorbent was trapped in an impinger containing cold acetonitrile. Subsequent evaporation of 95% of the acetonitrile in a Kuderna-Danish apparatus and gas chromatography (GC) of the concentrate resulted in a single mercury-containing GC peak at 5.5 min; the retention time and mass spectrum of this compound matched exactly those of a standard mercury(II) nitrate hydrate, Hg(NO(3))(2).H(2)O dissolved in acetonitrile. The volatile mercury component analyzed from injection of this standard solution was shown to be a form of methylmercury that is produced in the GC column by reaction of the highly reactive mercury nitrate with the methylsiloxane GC phase. Because the on-column derivatization reaction seems to be unique to mercury nitrate, the GC-MS (gas chromatography-mass spectroscopic) analysis provides strong evidence for identification of the trapped oxidized mercury species as mercury nitrate although, because the nitrate becomes detached from the mercury atom in the on-column reaction, the identity is not proven. 相似文献
10.
Dudkin VY Orlova M Geng X Mandal M Olson WC Danishefsky SJ 《Journal of the American Chemical Society》2004,126(31):9560-9562
Synthetic gp120331-335 glycopeptide fragments carrying hybrid and high-mannose type N-linked glycans were evaluated for binding to broadly neutralizing antibody 2G12 using surface plasmon resonance technology. None of the hybrid-type constructs demonstrated binding to 2G12. In the high-mannose series, the "Cys dimer" construct, presenting two undecasaccharide glycans, showed significantly higher binding than the Cys-protected monomer. The binding of the dimeric structure was further investigated in competition with recombinant gp120. The data suggest that gp120 and its designed synthetic epitope construct bind to the same site on 2G12. 相似文献