全文获取类型
收费全文 | 734篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
化学 | 560篇 |
晶体学 | 3篇 |
力学 | 17篇 |
数学 | 33篇 |
物理学 | 140篇 |
出版年
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 39篇 |
2012年 | 32篇 |
2011年 | 48篇 |
2010年 | 23篇 |
2009年 | 25篇 |
2008年 | 41篇 |
2007年 | 44篇 |
2006年 | 39篇 |
2005年 | 33篇 |
2004年 | 30篇 |
2003年 | 33篇 |
2002年 | 24篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 7篇 |
排序方式: 共有753条查询结果,搜索用时 15 毫秒
691.
Ohyama K Wada M Lord GA Ohba Y Fujishita O Nakashima K Lim CK Kuroda N 《Electrophoresis》2004,25(4-5):594-599
A capillary electrochromatographic method was developed for the separation of barbiturates. The separation was optimized in a 75 microm ID capillary, packed with 3-(1,8-naphthalimido)propyl-modified silyl silica gel (NAIP), studying the effect of buffer pH, buffer concentration, and mobile phase composition. Using an applied voltage of 20 kV and the short-end injection method (9 cm capillary effective length), the mobile phase of 1.0 mM citrate buffer (pH 5.0) containing 40% methanol provided the baseline separation of barbital, phenobarbital, secobarbital, and thiopental (internal standard) in less than 4.5 min. The method was successfully applied to the analysis of barbiturates in human serum. Under the optimal conditions, good repeatability and linearity were obtained in the range of 2.90-43.29 microg/mL for barbital, phenobarbital, and secobarbital. 相似文献
692.
Kenichi Nakashima Yoshinori Fujimoto Naofumi Kido 《Photochemistry and photobiology》1995,62(4):674-679
Abstract— The interaction of octadecylrhodamine B (ORB), a lipid-conjugated dye, with polystyrene latex in aqueous dispersions has been investigated by fluorescence techniques. The dependence of the fluorescence intensity of ORB on the latex concentration indicates that the dye is effectively adsorbed onto the latex surface from the aqueous phase and that deaggregation to fluorescent monomers from the nonfluorescent multimers takes place cooperatively when the surface coverage of the dye is reduced to a critical value. The fluorescence lifetime increases on going from a homogeneous methanolic solution to the latex dispersion, showing that the mobility of the probe is suppressed on the latex surface. From the results of polarization measurements, it is proposed that ORB molecules are adsorbed on the latex surface by a side-on geometry. The influence of a nonionic surfactant, triton X-100, on the fluorescence intensities of ORB and rhodamine B in the latex dispersion is also investigated. 相似文献
693.
Kenichi Nakashima Yoshinori Fujimoto Takayuki Anzai 《Photochemistry and photobiology》1995,61(6):592-599
The fluorescence intensity, lifetime and degree of polarization of octadecylrhodamine B (ORB) have been measured in order to examine the usefulness of this molecule as a probe of micelle properties for low-molecular-weight detergents and water-soluble triblock copolymers. The surfactants examined are hexadecyltrimethylammonium chloride (HTAC), Triton X-100 (TX-100), sodium dode-cylsulfate (SDS), sodium tetradecylsulfate (STS), and Pluronic L64 (ethylene oxide [EO]13 propylene oxide30 EO13, L64). The fluorescence intensity and degree of polarization of ORB show drastic increases at the critical micelle concentrations (CMC) of HTAC, TX-100 and L64, indicating that ORB is cooperatively incorporated into the micelles upon micellization. This feature demonstrates the validity of ORB as a probe for detecting micelle formation of these surfactants. However, in the case of SDS and STS, the fluorescence intensity starts to rise at concentrations far below the CMC, and the degree of polarization does not show significant changes at the CMC. The details of the interactions between ORB and the anionic surfactants have been unclear. These facts imply that some caution is needed for the applications of ORB to the systems containing anionic surfactants. The local viscosity of L64 micelles has been determined by polarization and lifetime measurements. The structure of the block copolymer micelles and the locations of the probe in the micelles are discussed in terms of the viscosity data. 相似文献
694.
G. Sugihara A. A. Nakamura T. -H. Nakashima Y. -I. Araki T. Okano M. Fujiwara 《Colloid and polymer science》1997,275(8):790-796
For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, the differential
conductivity (∂κ/∂C)
T
,
P
vs. square root of concentration (√C) was employed in order to determine not only CMC but also the limiting molar conductance (Λ0) and the molar conductance of micellar species (ΛM).
Based on the data of the degree of counterion binding to micelles (β) determined previously at different temperatures ranging
15–50 °C at every 5 °C, the experimental values of the degree of dissociation (ionization) of a micelle (αEX) were calculated by regarding as αEX=1−β. The ratio ΛM/Λ0 corresponding to the ratio of slopes below and above CMC in the curve of specific conductivity (κ) vs. concentration (C), which has been often assumed to be the degree of ionization of micelles (α), was compared with the present αEX. However, the ratio ΛM/Λ0 (=α) was found to have a correlationship with αEX (=1−β) as αEX≈0.40×(ΛM/Λ0), or strictly, αEX=0.40 (ΛM/Λ0)+0.08, indicating that the simple ratio of the slopes below and above CMC in κ vs. C curve is not true for αEX=1−β. On the other hand, the method proposed by Evans gave a value closer to αEX compared with the simple ratio.
Received: 17 September 1996 Accepted: 8 April 1997 相似文献
695.
Eiji Nakashima Kazuo Neriishi Atsushi Minamoto 《Annals of the Institute of Statistical Mathematics》2008,60(3):465-482
In analyses of bivariate ordered polytomous cataract data from atomic-bomb survivors, we compared two methods, the univariate
worse-eye method, and the bivariate generalized estimating equations (GEE’s) method using global odds ratio by Williamson
et al. (Journal of the American Statistical Association, 90, 1432–1437, 1995). When the association was large and only subject level covariates were used, model selection in the univariate
and bivariate methods resulted in the same mean model and similar risk estimates. We showed that the mean parameter and the
standard error (SE) in the univariate model are emphasized relative to those in the bivariate model, the biases of which are
negligible when the association between both eyes is large. Large sample simulation studies indicated that the univariate
Wald statistics are slightly conservative. The simulations also showed that, in bivariate cases, irrespective of the degree
of association, the independence estimating equations method with robust SE, and the GEE method with model-based and robust
SE are almost fully efficient in parameter estimation when only subject level covariates are included in the mean. 相似文献
696.
Le Thi Kim Dung Tomoki Imai Osamu Tomioka Mikio Nakashima Kuniaki Takahashi Yoshihiro Meguro 《Analytical sciences》2006,22(11):1425-1430
The supercritical fluid extraction (SFE) method using CO(2) as a medium with an extractant of HNO(3)-tri-n-butyl phosphate (TBP) complex was applied to extract uranium from several uranyl phosphate compounds and simulated uranium ores. An extraction method consisting of a static extraction process and a dynamic one was established, and the effects of the experimental conditions, such as pressure, temperature, and extraction time, on the extraction of uranium were ascertained. It was found that uranium could be efficiently extracted from both the uranyl phosphates and simulated ores by the SFE method using CO(2). It was thus demonstrated that the SFE method using CO(2) is useful as a pretreatment method for the analysis of uranium in ores. 相似文献
697.
A simple multilevel halftoning method, which is based on the conventional error diffusion method and realizes halftoning excelled in the distribution of dots, is proposed. The proposed method consists of three steps, e.g., the image decomposition, the generation of binary halftone images by the error diffusion, and the synthesis of a multilevel halftone image, and each step does not require a complicated algorithm. The effectiveness of the proposed method is indicated by applying it to three- and four-level halftoning of gray-tone and natural images. 相似文献
698.
Yoshinori Saito Saori Iga Kie Hoshiyama Katsuyuki Nakashima Yasuko Okamoto Chiaki Kuroda Xun Gong Motoo Tori 《Tetrahedron》2019,75(14):2239-2245
Secobakkane B (C-6/C-7 cleaved secobakkane type aldehyde), secovirgaurenols B and C (C-8/C-9 cleaved secoeremophilane type), a 1β,10β-epoxyfuranoeremophilane, two 1β,10β-epoxyeremophilanolides, and fukinospirolide C (bakkane-type lactone), as well as 33 known compounds were isolated from three samples of Ligularia virgaurea collected in China. Two of the three analyzed samples were grouped in the neoadenostylone (N) type, and the rest, a mixture of the 6-hydroxyeuryopsyn (H) and cacalol (C) types, out of five chemotypes found in this species. 相似文献
699.
We have measured electronic Raman scattering spectra and infrared absorption spectra of arsenic doped ZnTe. Electronic transitions from the ground state to the excited states in the arsenic acceptor and also vibronic transitions accompanying 1 LO phonon have been observed in both spectra. Experimentally determined acceptor levels are compared with the theoretical calculation. 相似文献
700.
Shuzo Matsumoto Yuka Taniguchi Yukihiro Fukunaga Hiromichi Nakashima Keiichi Watanabe Shoji Yamashita Etsuko Nishimoto 《Journal of fluorescence》2013,23(3):407-415
The structural feature of unfolding intermediate of pokeweed anti-viral protein (PAP) was characterized using time-resolved fluorescence spectroscopic methods to elucidate protein folding/unfolding process. CD and fluorescence spectra consistently demonstrated that the unfolding of PAP completed at 4 M of guanidine hydrochloride (GuHCl). The fluorescence resonance energy transfer (FRET) and time-resolve fluorescence depolarization analysis of Trp208 and Trp237 located in the C-terminal domain of PAP suggested that peculiar unfolding intermediate populated before reaching to the unfolding state. The FRET distance of Trp237 to Tyr182 was extended to more than 28 Å with keeping the compact conformation in the unfolding intermediate state populated in the presence of 2 M GuHCl. On the other hand, Trp208 maintained the energy transfer pair with Tyr72 near the active site, although the rotational freedom was increased a little. There results suggest that the most distinguished structural feature of the unfolding intermediate of PAP is the separation of C-terminal domain from N-terminal domain. FRET and fluorescence depolarization studies also showed that C-terminal domain would be more separated to liberate the segmental motions of Trp208 and Trp237 distinctly at the unfolding state. 相似文献