全文获取类型
收费全文 | 445篇 |
免费 | 12篇 |
专业分类
化学 | 346篇 |
晶体学 | 1篇 |
力学 | 14篇 |
数学 | 28篇 |
物理学 | 68篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 18篇 |
2012年 | 36篇 |
2011年 | 32篇 |
2010年 | 26篇 |
2009年 | 16篇 |
2008年 | 32篇 |
2007年 | 30篇 |
2006年 | 33篇 |
2005年 | 34篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有457条查询结果,搜索用时 31 毫秒
431.
Complementary asymmetric alkylation reaction of the lithioenamine derived from 2-methoxycarbonylcyclohexanone and ()-valine -butyl ester was examined by employing the various electron pair donating additives in a toluene solvent, in order to clarify the factors controlling the diastereoface selectivity. 相似文献
432.
433.
Y. Ikemoto T. Moriwaki H. Okamura T. Sasaki N. Yoneyama A. Taguchi Y. Inouye S. Kawata T. Kinoshita 《Infrared Physics & Technology》2008,51(5):417-419
The authors report infrared near-field spectroscopy using synchrotron radiation at BL43IR, SPring-8 in the finger print region. At the microspectroscopy station, the infrared synchrotron radiation beam is focused on a cantilever probe with a 3 μm square aperture. A comb-shaped Au electrode with the width of 3 μm and the distance of 3 μm is used for the reflection measurement. The Au electrodes can be resolved at 650 cm−1 and the resolution is estimated to be λ/5. 相似文献
434.
Kenji Nina Yuki Kimura Kaori Yokoyama Osamu Kido Gong Binyo Chihiro Kaito 《Physica E: Low-dimensional Systems and Nanostructures》2008,40(9):2995-2998
The formation process of MoO2 crystal from amorphous MoO3 film has been imaged by in situ observation with a transmission electron microscope. Selective growth of flower-shaped MoO2 crystals by heating above 673 K in vacuum was directly observed. Since the MoO2 crystal has metallic conductivity of the order of indium oxide film containing tin (ITO film), the thin film growth of the MoO2 phase has been discussed on the basis of a new substitute for ITO film. 相似文献
435.
436.
437.
Isao Fujii Makoto Hashimoto Kaori Konishi Akiko Unezawa Haruka Sakuraba Kenta Suzuki Harue Tsushima Miho Iwasaki Satsuki Yoshida Akane Kudo Rina Fujita Aika Hichiwa Koharu Saito Takashi Asano Jun Ishikawa Daigo Wakana Yukihiro Goda Ayumi Watanabe Mamoru Watanabe Yui Masumoto Junichiro Kanazawa Hajime Sato Masanobu Uchiyama 《Angewandte Chemie (International ed. in English)》2020,59(22):8464-8470
Shimalactones A and B are neuritogenic polyketides possessing characteristic oxabicyclo[2.2.1]heptane and bicyclo[4.2.0]octadiene ring systems that are produced by the marine fungus Emericella variecolor GF10. We identified a candidate biosynthetic gene cluster and conducted heterologous expression analysis. Expression of ShmA polyketide synthase in Aspergillus oryzae resulted in the production of preshimalactone. Aspergillus oryzae and Saccharomyces cerevisiae transformants expressing ShmA and ShmB produced shimalactones A and B, thus suggesting that the double bicyclo‐ring formation reactions proceed non‐enzymatically from preshimalactone epoxide. DFT calculations strongly support the idea that oxabicyclo‐ring formation and 8π‐6π electrocyclization proceed spontaneously after opening of the preshimalactone epoxide ring through protonation. We confirmed the formation of preshimalactone epoxide in vitro, followed by its non‐enzymatic conversion to shimalactones in the dark. 相似文献
438.
439.
Harusawa S Kawamura M Araki L Taniguchi R Yoneyama H Sakamoto Y Kaneko N Nakao Y Hatano K Fujita T Yamamoto R Kurihara T Yamatodani A 《Chemical & pharmaceutical bulletin》2007,55(8):1245-1253
The (2R,5S)-trans- and (2S,5S)-cis-stereoisomers 1a and 1b of 4(5)-(5-aminotetrahydropyran-2-yl)imidazole, which have two chiral centers and adopt a stable chair conformation, were synthesized via cyclization of diol intermediates 7 using L-glutamine as the starting material. Their enantiomers, (2S,5R)-trans-1c and (2R,5R)-cis-1d, were synthesized by the same methodology from D-glutamine. Stereo isomers 1a-d were converted into cyanoguanidines 11a-d, and into N-isopropyl and N-3,3-dimethylbutyl derivatives 12a-d and 13a-d, respectively. The results of in vivo brain microdialysis of the derivatives apparently indicated that only (2S,5R)-isomers increased the release of neuronal histamine. Among the many (2S,5R)-N-alkyl derivatives, 13c (OUP-133) and 18 (OUP-153) increased histamine release to 180-190% and 180-200% of basal levels, respectively, and were found to be novel histamine H(3) antagonists. 相似文献
440.
Mizuno T Murao K Tanabe Y Oda M Tanaka T 《Journal of the American Chemical Society》2007,129(37):11378-11383
Coordination of metal ions significantly contributes to protein structures and functions. Here we constructed a fusion protein, consisting of a de novo designed, metal-ion-binding, trimeric coiled-coil and a circularly permutated green fluorescent protein (cpGFP), where the fluorescent emission from cpGFP was induced by metal ion coordination to the coiled-coil. A circularly permutated GFP, (191)cpGFP(190), was constructed by connecting the original N- and C-termini of GFP(UV) by a GGSGG linker and cleaving it between Asp(190) and Gly(191). The metal-ion-binding coiled-coil, IZ-HH, was designed to have three alpha-helical structures, with 12 His residues in the hydrophobic core of the coiled-coil structure. IZ-HH exhibited an unfolded structure, whereas it formed the trimeric coiled-coil structure in the presence of divalent metal ions, such as Cu(2+), Ni(2+), or Zn(2+). The fusion protein (191)cpGFP(190)-IZ-HH was constructed, in which (191)cpGFP(190) was inserted between the second and third alpha-helices of IZ-HH. Escherichia coli cells, expressing (191)cpGFP(190)-IZ-HH, exhibited strong fluorescence when the Cu(2+) and Zn(2+) ions were present in the medium, indicating that they passed through the cell membrane and induced the proper folding of the (191)cpGFP(190) domain. This strategy, in which protein function is regulated by a metal-ion-responsive coiled-coil, should be applicable to the design of various metal-ion-responsive, nonnatural proteins that work both in vitro and in vivo. 相似文献