全文获取类型
收费全文 | 312篇 |
免费 | 16篇 |
专业分类
化学 | 297篇 |
晶体学 | 4篇 |
数学 | 3篇 |
物理学 | 24篇 |
出版年
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2017年 | 2篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 16篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 7篇 |
2009年 | 13篇 |
2008年 | 25篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 19篇 |
2002年 | 20篇 |
2001年 | 3篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 10篇 |
1972年 | 5篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1940年 | 2篇 |
排序方式: 共有328条查询结果,搜索用时 15 毫秒
271.
Hiroyuki Takemura Katsuya Sako Tesuo Iwanaga Akane Tatsumi Yukako Mogami Hiromi Watanabe Miho Aoki Shiho Yûki Yuri Hayano Mirei Itaka 《Tetrahedron》2018,74(16):1991-2001
The one-pot reaction between bis(hydroxymethyl)phenol derivatives and diamines or triamines afforded novel azacalixarenes with bridged structures. Basket-type macrocycles of cone conformations, molecules that contained two aza[3.1.1.1]calixarene skeletons connected by a chain, or novel saucer-type azacalixarenes were obtained from the reaction. Structures of some of them were determined by crystallographic analyses. 相似文献
272.
Dr. Koji Yamamoto Junya Sawada Prof. Tetsuro Murahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(38):8388-8392
We report the triply bridging coordination of thiophene and selenophene to a trinuclear metal cluster site. The triply bridging coordination of selenophene at a Pd3 site forms a unique spiro-type Pd5 cluster. Furthermore, either thiophene or selenophene is accommodated stably at a Pd3 site supported by a backside μ3-cyclooctatetraene ligand through the face-capping μ3-coordination. The Pd3 site supported by the cyclooctatetraene ligand showed higher binding affinity of benzene over thiophene, although a Pd2 site strongly favors thiophene over benzene. 相似文献
273.
Norio Wada Miho Nakamura Yumi Tanaka Kiyoshi Kanamura Kimihiro Yamashita 《Journal of colloid and interface science》2009,330(2):374-379
We demonstrated the formation of calcite thin films on positively and negatively charged surfaces of a hydroxyapatite (HAp) electret coexisting with polyacrylic acid (PAA) and self-generating surface electric fields due to HAp electrets with electrically aligned dipoles. The cooperation of PAA and the self-generating surface electric field due to the electrets favored the formation of calcite thin films and acted remarkably on the negatively charged surface. Calcite thin films, 4–10 μm thick, with a shell-like microstructure were produced on the negatively charged surfaces with a small amount of PAA. In contrast, under other reaction conditions, calcite thin films with a fan-like structure in the cross section formed on the polarized substrates, and their thickness ranged from 2 to 7 μm. The films were composed of hemispheric- or flat island-shaped aggregates that were made of the calcite crystals that elongated along the c-axis. The morphology of the PAA–Ca2+ complex assembly, which adsorbed onto the polarized HAp substrates, was controlled by the balance of the spatial charge distribution in its structure and the properties of the self-generating surface electric field, which led to the different morphologies of the calcite thin films. We proposed that the formation mechanism of the films formed coexisting with PAA and the self-generating electric fields. 相似文献
274.
275.
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
276.
Hatsumi Nakazawa Shinobu Fujinami Miho Motoyama Takao Ohta Takeaki Araki Hajime Tanaka 《Molecular Crystals and Liquid Crystals》2013,570(1):871-878
Abstract Polymerization-induced phase separation in polymer-dispersed liquid crystal is studied by computer simulations in two dimensions. The domain morphology resulting from phase separation is investigated by solving the couple set of equations for the local volume fraction and the nematic order parameter, taking into account the viscoelastic effects and gelation due to polymerization. Comparing the morphology of phase separation by temperature quench, it is shown that the viscoelastic effects and gelation enable the polymer-rich phase to form a stable interconnected domain even when the polymer component is minority. 相似文献
277.
A target value for iminoctadine triacetate residues in tap water was set at 6 microg/l in Japan. We have developed a highly selective and sensitive analytical method for iminoctadine triacetate by solid phase extraction LC/ESI/MS using hydrophilic interaction chromatography. The recovery rates at concentration of 0.06, 0.6, and 6 microg/l in distilled water, tap water, and raw water were 77.1 - 96.7%, and CV were 3.7 - 13.2%. The quantitation limit of the present method was 0.04 microg/l, and it was able to measure even one-hundredth of the target value of iminoctadine triacetate quantitatively. 相似文献
278.
Dr. Koji Yamamoto Seita Kimura Prof. Tetsuro Murahashi 《Angewandte Chemie (International ed. in English)》2016,55(17):5322-5326
The intrinsic features of (hetero‐arene)–metal interactions have been elusive mainly because the systematic structure analysis of non‐anchored hetero‐arene–metal complexes has been hampered by their labile nature. We report successful isolation and systematic structure analysis of a series of non‐anchored indole–palladium(II) complexes. It was revealed that there is a σ–π continuum for the indole–metal interaction, while it has been thought that the dominant coordination mode of indole to a metal center is the Wheland‐intermediate‐type σ‐mode in light of the seemingly strong electron‐donating ability of indole. Several factors which affect the σ‐ or π‐character of indole–metal interactions are discussed. 相似文献
279.
Rhodium(III)‐Catalyzed Tandem [2+2+2] Annulation–Lactamization of Anilides with Two Alkynoates via Cleavage of Two Adjacent C−H or C−H/C−O bonds 下载免费PDF全文
Miho Fukui Dr. Yu Shibata Yuki Hoshino Haruki Sugiyama Kota Teraoka Prof. Dr. Hidehiro Uekusa Prof. Dr. Keiichi Noguchi Prof. Dr. Ken Tanaka 《化学:亚洲杂志》2016,11(16):2260-2264
An electron‐deficient CpE rhodium(III) complex bearing a cyclopentadienyl ligand with two ethyl ester substituents catalyzes the tandem [2+2+2] annulation–lactamization of acetanilides with two alkynoates via cleavage of adjacent two C?H bonds to give densely substituted benzo[cd]indolones. The reactions of meta‐methoxy‐substituted acetanilides with two alkynoates also provided benzo[cd]indolones via cleavage of adjacent C?H/C?O bonds. Furthermore, 3,5‐dimethoxyacetanilides reacted with two alkynoates to give dearomatized spiro compounds. 相似文献
280.
Daisuke Sakai Daichi Miho Kenji Harada Daisuke Barada Takashi Fukuda 《Optical Review》2010,17(3):187-190
We have succeeded in the first fabrication of a diffractive structure replicated onto a glass substrate using a template of
self-assembled polystyrene particles via corona-charging treatment. A hexagonal close-packed structure of selfassembled particles
was used as the template in the structural replication. As a result, a sixfold symmetric diffraction pattern was generated
from the glass substrate, on/in which the diffractive structure was replicatively fabricated. The dependence of the diffraction
efficiency on processing time of corona-charging treatment was examined. It was found that the diffraction efficiency increased
with treatment time up to 2 h. The observed first-order diffraction efficiency was 2.4 × 10−3%. In contrast, the diffraction efficiency decreased after 2 h treatment under our current experimental conditions. This trend
of diffraction efficiency was discussed on the basis of structural changes of the polystyrene template. 相似文献