全文获取类型
收费全文 | 240篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
化学 | 202篇 |
数学 | 9篇 |
物理学 | 51篇 |
出版年
2024年 | 4篇 |
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 11篇 |
2020年 | 14篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 13篇 |
2013年 | 13篇 |
2012年 | 25篇 |
2011年 | 19篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 16篇 |
2007年 | 12篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 1篇 |
2001年 | 7篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1984年 | 4篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有262条查询结果,搜索用时 15 毫秒
91.
T. Shimoda K. Tajiri K. Kura A. Odahara M. Suga Y. Hirayama N. Imai H. Miyatake M. Pearson C. D. P. Levy K. P. Jackson R. Legillon C. Petrache T. Fukuchi N. Hamatani T. Hori M. Kazato Y. Kenmoku T. Masue H. Nishibata T. Suzuki A. Takashima R. Yokoyama 《Hyperfine Interactions》2014,225(1-3):183-191
Spin-polarized radioactive nuclear beams at TRIUMF enable a new spectroscopic method which efficiently assigns spins and parities of the daughter levels by taking advantage of the asymmetric β-decay of the polarized parent nucleus. This method was successfully applied to structure studies of 29Mg and 30Mg in connection with the physics of the “island of inversion”. In 29Mg, two low-lying levels with intruder configuration were assigned. In 30Mg, coexistence of spherical shape, prolate shape and γ-collectivity was strongly suggested. 相似文献
92.
Prof. Dr. Haruhiko Fuwa Masato Kawakami Kenkichi Noto Takashi Muto Yuto Suga Prof. Dr. Keiichi Konoki Prof. Dr. Mari Yotsu‐Yamashita Prof. Dr. Makoto Sasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8100-8110
We describe herein a concise synthesis of (+)‐neopeltolide, a marine macrolide natural product that elicits a highly potent antiproliferative activity against several human cancer cell lines. Our synthesis exploited the powerful bond‐forming ability and high functional group compatibility of olefin metathesis and esterification reactions to minimize manipulations of oxygen functionalities and to maximize synthetic convergency. Our findings include a chemoselective olefin cross‐metathesis reaction directed by H‐bonding, and a ring‐closing metathesis conducted under non‐high dilution conditions. Moreover, we developed a 16‐member stereoisomer library of 8,9‐dehydroneopeltolide to systematically explore the stereostructure–activity relationships. Assessment of the antiproliferative activity of the stereoisomers against A549 human lung adenocarcinoma, MCF‐7 human breast adenocarcinoma, HT‐1080 human fibrosarcoma, and P388 murine leukemia cell lines has revealed marked differences in potency between the stereoisomers. This study provides comprehensive insights into the structure–activity relationship of this important antiproliferative agent, leading to the identification of the pharmacophoric structural elements and the development of truncated analogues with nanomolar potency. 相似文献
93.
Hitoshi Tamiaki Rie Monobe Shun Koizumi Tomohiro Miyatake Yusuke Kinoshita 《Tetrahedron: Asymmetry》2013,24(11):677-682
Regioselective reduction of the 13-carbonyl group on the five-membered exo-ring of methyl pyropheophorbide-a, one of the chlorophyll-a derivatives, with sodium borohydride gave an epimeric mixture of (131R/S)-hydroxy-chlorins. The stereoselectivity was controlled by the steric effect of the (17S)-methoxycarbonylethyl group to afford the (131S)-rich secondary alcohol (25% de). The use of sterically large lithium tri(sec-butyl)borohydride as the reductant enhanced the stereoselectivity to 55% de. The regio- and stereoselective methylation and phenylation of the 13-CO of pyropheophorbide-a were observed using methyl and phenyl lithium, respectively. The major diastereomer of the tertiary alcohols obtained had the same configuration at the 131-stereogenic center as in the reduced product. All of the anion species (H?, CH3?, and C6H5?) favorably attacked the 131-carbon atom from the reverse side of the 17-propionate residue, that is, the less sterically crowded face of the 13-CO plane. 相似文献
94.
We demonstrate the permeabilization of cell membranes by an enhanced optical field generated under polystyrene microspheres of 1000 nm diameter excited by a femtosecond laser pulse. Fluorescent molecules and short interfering RNA (siRNA) have been successfully delivered to many cells in the irradiated area by a single 80 fs laser pulse at 800 nm wavelength in the presence of antibody-conjugated polystyrene spheres. The ratios of the cells showing permeabilization were 38% and 21% for Fluorescein isothiocyanate-dextran and siRNA, respectively, at the laser fluence of 1.06 J/cm(2). The present method has advantages both in high throughput of many cell treatments and precise processing of minute areas on cell membranes. 相似文献
95.
Hideyuki Nakanishi Yuto Kawabata Shogo Tsujiai Hayato Tanaka Satoshi Teraji Gbor Holl Istvn Lagzi Tomohisa Norisuye Qui Tran‐Cong‐Miyata 《Angewandte Chemie (International ed. in English)》2020,59(31):13086-13092
The development of methods to pattern nanocrystals with different sizes and shapes remains a challenge. In this study, we demonstrate a unique class of bottom‐up approaches to assemble nanocrystals into patterns. Our approach for patterning nanocrystals focuses on the utilization and control of the chemical reaction of solvents surrounding nanocrystals. The photopolymerization of solvent molecules through a photomask creates time‐dependent concentration gradients of the solvents. Dispersed nanocrystals such as silver nanowires (AgNWs) migrate and are gradually organized and integrated into the polymerizing films based on the concentration gradients. The AgNW‐embedded film properties are determined by the organized AgNW structures and include light transmission and electrical conductivity. Overall, the demonstrated method is very simple, widely applicable to various nanocrystals and solvents, and can thus contribute to the development of a new class of nanocrystal patterning methods. 相似文献
96.
Yasuyoshi Miki Yosiyuki Aoki Hideaki Miyatake Toshie Minematsu Hajime Hibino 《Tetrahedron letters》2006,47(29):5215-5218
1-Benzenesulfonylindole-2,3-dicarboxylic anhydride was reacted with methyl 1-benzenesulfonylindole-2-acetate to give the corresponding 2-acylindole-3-carboxylic acid as the sole product in high yield, which could be converted to caulersin in four steps. In a similar manner, three isomers A, B, and C were synthesized by reaction of indole-2,3-dicarboxylic anhydrides with methyl indoleacetates. 相似文献
97.
N. Nishida S. Okuma H. Miyatake S. Shiratake Y. Hidaka T. Murakami Y. Ueda K. Kosuge S. Kambe H. Yasuoka H. Takagi S. Uchida K. Nishiyama K. Nagamine Y. Kuno T. Yamazaki 《Hyperfine Interactions》1991,65(1-4):1027-1034
The negative muon spin rotation method (μ− SR) has been applied to studies of electronic states at oxygen sites of oxide superconductors YBa2Cu3O7, Nd2−x
Ce
x
CuO4−δ (x=0.15, oxygen reduced), LiTi2O4 and related oxide-insulators La2CuO4−δ, CuO, Cu2O. The paramagnetic shifts of μ− trapped at oxygen nuclei in these polycrystalline powder samples have been measured at 300 K. All the measured shifts are
positive. In copper-oxides the paramagnetic shifts are of the order 10−3, while in LiTi2O4 is very small (8.4±3.34×10−5). In YBa2Cu3O7, a fast μ− spin relaxation timeT
2
* (∼ 200 ns) has been observed; the reason for this is unknown and further studies are now in progress. 相似文献
98.
99.
VanSchouwen BM Gordon HL Rothstein SM Komeiji Y Fukuzawa K Tanaka S 《Computational Biology and Chemistry》2008,32(3):149-158
The cyclic AMP receptor protein (CRP) of Escherichia coli binds preferentially to DNA sequences possessing a T:A base pair at position 6 (at which the DNA becomes kinked), but with which it does not form any direct interactions. It has been proposed that indirect readout is involved in CRP-DNA binding, in which specificity for this base pair is primarily related to sequence effects on the energetic susceptibility of the DNA to kink formation. In the current study, the possibility of contributions to indirect readout by water-mediated hydrogen bonding of CRP with the T:A base pair was investigated. A 1.0 ns molecular dynamics simulation of the CRP-cAMP-DNA complex in explicit solvent was performed, and assessed for water-mediated CRP-DNA hydrogen bonds; results were compared to several X-ray crystal structures of comparable complexes. While several water-mediated CRP-DNA hydrogen bonds were identified, none of these involved the T:A base pair at position 6. Therefore, the sequence specificity for this base pair is not likely enhanced by water-mediated hydrogen bonding with the CRP. 相似文献
100.
Takeshi Inoue Takeshi Furukawa Akihiro Yoshimi Tsubasa Nanao Masatoshi Chikamori Kunifumi Suzuki Hironori Hayashi Hirokazu Miyatake Yuichi Ichikawa Masato Tsuchiya Naoto Hatakeyama Sota Kagami Makoto Uchida Hideki Ueno Yukari Matsuo Takeshi Fukuyama Koichiro Asahi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2016,70(6):129