全文获取类型
收费全文 | 669篇 |
免费 | 23篇 |
国内免费 | 4篇 |
专业分类
化学 | 508篇 |
晶体学 | 4篇 |
力学 | 11篇 |
数学 | 73篇 |
物理学 | 100篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 20篇 |
2015年 | 20篇 |
2014年 | 12篇 |
2013年 | 39篇 |
2012年 | 37篇 |
2011年 | 45篇 |
2010年 | 32篇 |
2009年 | 21篇 |
2008年 | 36篇 |
2007年 | 50篇 |
2006年 | 50篇 |
2005年 | 29篇 |
2004年 | 30篇 |
2003年 | 39篇 |
2002年 | 19篇 |
2001年 | 16篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
排序方式: 共有696条查询结果,搜索用时 15 毫秒
201.
Kuroda D Zhang Y Wang J Kaji N Tokeshi M Baba Y 《Analytical and bioanalytical chemistry》2008,391(7):2543-2549
A thermo-responsive separation matrix, consisting of Pluronic F127 tri-block copolymers of poly(ethylene oxide) and poly(propylene
oxide), was used to separate DNA fragments by microchip electrophoresis. At low temperature, the polymer matrix was low in
viscosity and allowed rapid loading into a microchannel under low pressure. With increasing temperatures above 25°C, the Pluronic
F127 solution forms a liquid crystalline phase consisting of spherical micelles with diameters of 17–19 nm. The solution can
be used to separate DNA fragments from 100 bp to 1500 bp on poly(methyl methacrylate) (PMMA) chips. This temperature-sensitive
and viscosity-tunable polymer provided excellent resolution over a wide range of DNA sizes. Separation is based on a different
mechanism compared with conventional matrices such as methylcellulose. To illustrate the separation mechanism of DNA in a
Pluronic F127 solution, DNA molecular imaging was performed by fluorescence microscopy with F127 polymer as the separation
matrix in microchip electrophoresis.
Figure Temperature dependence of the viscosity of 20% w/w Pluronic F127 solution in 1xTBE buffer. Dotted approximates resultant curve. 相似文献
202.
Neat Et2Zn, Ph2Zn, and highly concentrated Me2Zn are highly reactive organozinc reagents, which are commercially available in bulk quantities. We here report a catalytic enantioselective Et2Zn, Ph2Zn, and Me2Zn addition to ketones and aldehydes under solvent free or highly concentrated conditions without Ti(Oi-Pr)4 as a conventional activator of organozinc reagents. The desired optically active tertiary and secondary alcohols were obtained in good yield with high enantioselectivity when compared to the conventional solvent-use conditions. From the viewpoint of ecological and environmental reasons in green chemistry, this catalysis would be practical for not only academic but also industrial use. 相似文献
203.
Tadatsugu Yamaguchi Manabu HosakaToru Ozeki Masakazu MorimotoMasahiro Irie 《Tetrahedron letters》2011,52(43):5601-5604
Photochromic benzo[b]silole derivatives, 1-(1,1-dimethyl-2-phenylbenzo[b]silol-3-yl)-2-(2-phenylbenzo[b]thien-3-yl)perfluorocyclopentene and 1-(1,1-dimethyl-2-phenylbenzo[b]silol-3-yl)-2-(2-phenyl-1-benzofuran-3-yl)perfluorocyclopentene, were synthesized and their photochromic performance was examined in solution. 相似文献
204.
Quantitative determination of amino acids in functional foods by microchip electrophoresis 总被引:1,自引:0,他引:1
Microchip electrophoresis (MCE), a first-generation micrototal analysis system, has emerged during the miniaturization phase of food analysis. Based on the micellar electrokinetic chromatography mode, a simple and fast MCE method with light emitting diode-induced fluorescence detection was developed for quantitative analysis of amino acids in three different kinds of functional foods, viz. sports beverages, jelly-form beverages, and tablet-form functional foods. In contrast to the glass microchip, we improved the separation of amino acids on a poly(methyl methacrylate) (PMMA) chip by addition of cationic starch derivatives. 4-fluoro-7-nitro-2,1,3-benzoxadiazole, which has a short labeling time for amino acids, was used as the fluorescently labeled dye. This MCE method takes less than 10 min of total analysis time including sample preparation and analysis of amino acids in functional foods on a PMMA chip. The results show that this approach has the potential to be a fast and simple method for amino acid analysis in functional foods. 相似文献
205.
Manabu Miyamoto Kaori Nagata Takanori Maruo Norikazu Nishiyama Katsunori Yogo Yasuyuki Egashira Korekazu Ueyama 《Journal of membrane science》2008
Mesoporous silica membranes were prepared on porous alumina substrates by a vapor infiltration of tetraethoxysilane (TEOS) into a non-ionic poly(oxyethylene) (Brij56) surfactant film. Periodic mesostructured silica membranes were formed on both α- and γ-alumina substrates pre-treated with polystyrene. The polystyrene polymer plugged the pores of the alumina substrates and inhibited the deposition of silica in the alumina pores, resulting in the formation of a very thin silica membrane without a silica/alumina composite layer at the interface between mesoporous silica and the alumina substrates. The calcined mesoporous silica membrane showed very high nitrogen permeance (>10−6 mol m−2 s−1 Pa−1). The single gas permeation was governed by the Knudsen diffusion mechanism. The durability of the mesoporous silica membrane against moisture in air was improved by a silylation with trimethylethoxysiliane. 相似文献
206.
Jim Maxka Jerzy Chrusciel Manabu Sasaki Krzysztof Matyjaszewski 《Macromolecular Symposia》1994,77(1):79-92
Copolymers and homopolymers containing silicon atoms connected to three and four other silicon atoms have been prepared and characterized. We report the first evidence of dendritic polymers with silicon backbones. Copolymers made from RSiCl3 and R1R2SiCl2 resemble hybrid materials of polysilyne and polysilanes. Polymers, which contain tetrasilyl-substituted Si atoms, [(SiMe2)4Si]n and (Si)m(Me2Si)n, have also been synthesized. These molecules appear to be the first hyperbranched polymers, which have applications based on their electronic properties. The properties of these molecules fit into the hierarchy of 1-D to 3-D topologies known for Si materials. 相似文献
207.
Masamitsu Tanaka Manabu Kinoshita Yasuo Yoshihara Nariyoshi Shinomiya Shuhji Seki Koichi Nemoto Yuji Morimoto 《Photochemistry and photobiology》2010,86(2):403-409
Although there have been some reports about the cytotoxic effects of photodynamic therapy (PDT) on multidrug-resistant bacteria, there have been few reports in which favorable results of PDT on a local infection site are described. This study aimed to verify the hypothesis that the low efficacy of PDT on a local infection site is due to the cytotoxic effect of PDT on leukocytes. PDT using Photofrin® exerted significant cytotoxicity for cultured methicillin-resistant Staphylococcus aureus (MRSA). Nevertheless, this therapeutic modality was not effective for a murine MRSA arthritis model. Approximately 30% of intra-articular leukocytes, mainly neutrophils, died immediately after PDT, and a further decrease in the number of intra-articular leukocytes and atrophy of the synovial tissue were seen 24 h after PDT. Isolated peripheral neutrophils showed significant affinity for Photofrin® and showed significant morphological damage, resulting in cell death, when they were subject to PDT using Photofrin®. These results indicate that intra-articular neutrophils have an influence on the effects of PDT for MRSA arthritis. 相似文献
208.
209.