全文获取类型
收费全文 | 200篇 |
免费 | 4篇 |
专业分类
化学 | 107篇 |
力学 | 3篇 |
数学 | 5篇 |
物理学 | 89篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 9篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 2篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1970年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有204条查询结果,搜索用时 31 毫秒
81.
The cross-correlation properties of dichromatic light multiply-scattered by colloidal particles in a uniform flow are studied experimentally. It is shown that the correlation peak value of intensity fluctuations depends on the optical thickness of the sample and the number density of particles, whereas the decay time of cross-correlation functions is almost independent of the characteristics of particle suspensions. This result indicates that the number fluctuations as well as the speckle fluctuations contribute to the temporal variations in the intensity, and that the velocity of the uniform flow is measurable without being affected by the diffusive motion of the scatterers. The effect of wavelength difference is also examined. 相似文献
82.
The thermolysis of a pentacoordinate fluorodisilane bearing an 8-(dimethylamino)-1-naphthyl group in the presence of 2,3,4,5,6-pentaphenylfulvene or 14-phenyldibenzofulvene affords a silylene-fulvene adduct bearing a zwitterionic structure attributable to the silaylide, but it spontaneously undergoes subsequent intramolecular cyclization reaction between the silicon atom and the aromatic carbon atom in the fulvene moiety followed by a sigmatropic proton migration to form a neutral silicon-containing six- or five-membered ring product. 相似文献
83.
Various cyclic ethers are prepared in good to excellent yields by treating diolefins with phenylselenyl chloride in aqueous acetonitrile. This is the most facile method for organoselenium-induced formation of cyclic ethers from diolefins so far reported. 相似文献
84.
Jan-E. Bäckvall Mesbah U. Ahmad Sakae Uemura Akio Toshimitsu Takashi Kawamura 《Tetrahedron letters》1980,21(23):2283-2286
Stereochemical studies on the copper(I) halide cleavage of thallium-carbon bonds in acetonitrile indicate that at 80°C a radical path accounts for approximately of the product, whereas at 60°C an ionic path predominates. The results are consistent with e.s.r. measurements by a spin trapping technique. 相似文献
85.
A poly-
-histidine(PLH)-copper(II) complex can be used as an alternative biocatalyst in an O2 detection-type amperometric enzyme-less
-ascorbate (AsA) sensor. The PLH–Cu(II) membrane was simply prepared by entrapping the PLH in polyacrylamide gel and subsequent treatment of the gel with CuCl2 solution. This enzyme-less biosensor can be used over a relatively wide pH region from 4 to 11 and enables precise determination of AsA (RSD less than 3%, n=10) at pH 7.0. The fundamental performance characteristics (sensitivity, response time, and linear range) of this PLH–Cu(II)-based sensor is comparable to those of a native ascorbate oxidase-based sensor. Unfortunately, the selectivity is inherently rather low and, as a result, the response was degraded in the presence of higher concentrations (more than mM order) of quinones. However, reducing sugars caused no interference and the sensor could be used to detect AsA in some fruits and drinks. This enzyme-less sensor has excellent stability for at least 3 months of repeated analysis (more than 300 samples) without loss of ordinal activity. 相似文献
86.
Osamu Onomura Peter G. Kirira Toshimitsu Tanaka Shinsuke Tsukada Yoshihiro Matsumura Yosuke Demizu 《Tetrahedron》2008,64(32):7498-7503
Diastereoselective introduction of nucleophiles into l-proline derivatives at the 5-position was achieved with suitable selection of N-protecting group. N-Methoxycarbonylated or benzyloxycarbonylated l-proline derivatives reacted with arene to give cis-arylated products. On the other hand, N-benzoylated l-proline derivative preferentially gave trans-arylated product, which could be easily transformed into optically active C2-symmetrical pyrrolidine derivative. Such derivative 5 worked well as an organic activator in the asymmetric reduction of aromatic imines by Cl3SiH. 相似文献
87.
88.
89.
Dispersion Theory of Liquids Containing Optically Linear and Nonlinear Maxwell Garnett Nanoparticles 总被引:2,自引:0,他引:2
Kai-Erik Peiponen Martti O. A. M#xE;kinen Jarkko J. Saarinen Toshimitsu Asakura 《Optical Review》2001,8(1):9-17
Kramers-Kronig relations and sum rules for effective linear permittivity of the Maxwell Garnett liquid-nanosphere system were obtained using complex analysis and general expression of the effective permittivity. When reflectance from optically linear and nonlinear Maxwell Garnett nanoparticles was calculated it was observed that the reflectance, in the case of attenuated total reflection, depends on the fill fraction of the nanospheres and their nonlinear susceptibility. According to simulations a good sensitivity of the nonlinear contribution on the reflectance can be obtained by using a probe wavelength corresponding to the resonance frequency of the nanosphere system. In Kretchmann#x0027;s configuration it was observed that the surface-plasmon-resonance angle depends on the fill fraction and on the intensity of the incident light. By using reflectance, it is possible to detect optically nonlinear nanospheres in liquids. 相似文献
90.
Yuka MiyakeYu Kimura Syungo IshikawaHiroshi Tsujita Hiroki MiuraMichiko Narazaki Tetsuya MatsudaYasuhiko Tabata Tetsuya YanoAkio Toshimitsu Teruyuki Kondo 《Tetrahedron letters》2012,53(34):4580-4583
Novel chiral dendrimer-triamine-coordinated Gd complexes were synthesized and shown to have longitudinal relaxivity (r1) 3 times higher than that of clinically used Gd-DTPA. The pharmacokinetic differences between optical isomers were estimated from the affinity of 2-(R) and 2-(S) with bovine serum albumin (BSA), respectively, by a quartz crystal microbalance (QCM) measurement. As a result, the association constant Ka of 2-(S) was about 4 times higher than that of 2-(R), which means that 2-(S) is retained in the vascular retention for a longer time after administration. This result was also supported by T1-weighted MR images of mice before and after the intravenous injection of 2-(R) and 2-(S), as well as the time-course of the signal intensities (SI) at the blood vessels and quantification of Gd3+ concentration in the blood and urine. 相似文献