全文获取类型
收费全文 | 553篇 |
免费 | 35篇 |
国内免费 | 1篇 |
专业分类
化学 | 386篇 |
晶体学 | 8篇 |
力学 | 11篇 |
数学 | 78篇 |
物理学 | 106篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 22篇 |
2019年 | 24篇 |
2018年 | 28篇 |
2017年 | 9篇 |
2016年 | 25篇 |
2015年 | 32篇 |
2014年 | 19篇 |
2013年 | 32篇 |
2012年 | 37篇 |
2011年 | 52篇 |
2010年 | 37篇 |
2009年 | 18篇 |
2008年 | 41篇 |
2007年 | 41篇 |
2006年 | 34篇 |
2005年 | 21篇 |
2004年 | 14篇 |
2003年 | 17篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有589条查询结果,搜索用时 203 毫秒
581.
Hydrophobic ionic liquids composed of tetrabutylphosphonium cation and chiral anions derived from amino acids modified with trifluoromethane sulfonyl groups have been synthesized using a simple method. 相似文献
582.
Carboxylesterase and sorbitol dehydrogenase are separated by non-denaturing two-dimensional electrophoresis (2-DE) of isoelectric focusing separation using 5% carrier ampholyte (pH 6-8) and 1.25% carrier ampholyte (pH 3-10) and size separation. Furthermore, activities of sorbitol, malate and lactate dehydrogenases are sequentially examined when the enzymes are separated by 2-DE and are sequentially reacted to sorbitol, malic and lactic acid, respectively, in the presence of nicotinamide adenine dinucleotide, nitro blue tetrazolium and phenazine methosulphate. Several kinds of enzymes including lactate dehydrogenize isozymes can be simultaneously separated using 2-DE. Furthermore, the binding differences between lactate dehydrogenase isozymes and concanavalin A (con A) can be examined using a combination of 2-DE and non-denaturing stacking gel electrophoresis. The results of this study indicate that non-denaturing 2-DE can be applied to both enzyme separation and isozyme heterogeneity analysis. 相似文献
583.
Kenta Itahashi Georg P. A. Berg Hiroyuki Fujioka Hans Geissel Ryugo S. Hayano Satoru Hirenzaki Natsumi Ikeno Naohito Inabe Satoshi Itoh Daisuke Kameda Toshiyuki Kubo Hiroaki Matsubara Shinichiro Michimasa Kenjiro Miki Hiroyuki Miya Masaki Nakamura Takahiro Nishi Shumpei Noji Shinsuke Ota Ken Suzuki Hiroyuki Takeda Koichi Todoroki Kyo Tsukada Tomohiro Uesaka Helmut Weick Koichi Yoshida 《Hyperfine Interactions》2012,209(1-3):51-56
584.
Makoto Okano Tomoya Yamada Youichi Sakakibara Toshihiro Kamei Jun-ichiro Sugisaka Noritsugu Yamamoto Masahide Itoh Takeyoshi Sugaya Kazuhiro Komori Masahiko Mori 《Photonics and Nanostructures》2012,10(3):287-295
We present an efficient means of light extraction from two-dimensional photonic crystal (2D PC) cavities with SiO2 cladding. We propose a vertically coupled system consisting of a 2D PC cavity and a hydrogenated-amorphous-silicon (a-Si:H)-wire waveguide, which we theoretically investigate using the 3D finite-difference time-domain method. Light can be extracted with an efficiency of greater than 95% to both output ports of the a-Si:H-wire waveguide or extracted with an efficiency of greater than 90% to a single output port of the a-Si:H-wire waveguide with a reflector. 相似文献
585.
Daisuke Iida Kenta Tamura Motoaki Iwaya Satoshi Kamiyama Hiroshi Amano Isamu Akasaki 《Journal of Crystal Growth》2010,312(21):3131-3135
The electrical and optical properties of Mg-doped a- and c-plane GaN films grown by metalorganic vapor phase epitaxy were systematically investigated. The photoluminescence spectra of Mg-doped a- and c-plane GaN films exhibit strong emissions related to deep donors when Mg doping concentrations are above 1×1020 cm−3 and 5×1019 cm−3, respectively. The electrical properties also indicate the existence of compensating donors because the hole concentration decreases at such high Mg doping concentrations. In addition, we estimated the ND/NA compensation ratio of a- and c-plane GaN by variable-temperature Hall effect measurement. The obtained results indicate that the compensation effect of the Mg-doped a-plane GaN films is lower than that of the Mg-doped c-plane GaN films. 相似文献
586.
Dr. Hirofumi Ueda Dr. Soichiro Sato Kenta Noda Dr. Hiroyuki Hakamata Dr. Eunsang Kwon Prof. Dr. Nagao Kobayashi Prof. Dr. Hidetoshi Tokuyama 《Angewandte Chemie (International ed. in English)》2023,62(22):e202302404
Biomimetic oxidative dimerization of tryptophan derivatives in aqueous media with oxygen as a bulk oxidant catalyzed by an iron octacarboxy phthalocyanine complex was established. The discovery of the extremely active iron catalyst enables aerobic enzyme-mimetic oxidation to be performed in a flask. This method was applicable to the oxidative dimerization of a wide range of tryptophan derivatives, including various dipeptides and oligopeptides, with remarkable functional-group tolerance without the protection of the amino acid residues. Furthermore, oxidative dimerization of tryptophan derivatives bearing dioxopiperazine units enabled the convergent total synthesis of five natural pyrroloindole compounds and unnatural congeners. The established chemical method provides facile access to a broad range of dimerized peptides with a unique scaffold to link two turn structures, which will serve as a powerful tool to create new small- and medium-sized-molecules as drug candidates. 相似文献
587.
Dr. Daichi Kato Dr. Peng Song Dr. Hiroki Ubukata Haruki Taguro Dr. Cédric Tassel Dr. Kohei Miyazaki Prof. Takeshi Abe Dr. Kousuke Nakano Prof. Kenta Hongo Prof. Ryo Maezono Prof. Hiroshi Kageyama 《Angewandte Chemie (International ed. in English)》2023,62(30):e202301416
Mixed-anion compounds have attracted growing attentions, but their synthesis is challenging, making a rational search desirable. Here, we explored LaF3-LaX3 (X=Cl, Br, I) system using ab initio structure searches based on evolutionary algorithms, and predicted LaF2X and LaFX2 (X=Br, I), which are respectively isostructural with LaHBr2 and YH2I, consisting of layered La-F blocks with single and double ordered honeycomb lattices, separated by van der Waals gaps. We successfully synthesized these compounds: LaF2Br and LaFI2 crystallize in the predicted structure, while LaF2I is similar to the predicted one but with different layer stacking. LaF2I exhibits fluoride ion conductivity comparable to that of non-doped LaF3, and has the potential to show better ionic conductivity upon appropriate doping, given the theoretically lower diffusion energy barrier and the presence of soft iodine anions. This study shows the structure prediction using evolutionary algorithms will accelerate the discovery of mixed-anion compounds in future, in particular those with an ordered anion arrangement. 相似文献
588.
589.
Acridone units were incorporated into the arylene–ethynylene structure as polar arene units. Cyclic trimers consisting of three acridone-2,7-diyl units and three 1,3-phenylene units were synthesized by Sonogashira couplings via stepwise or direct route. X-ray analysis revealed that the trimer had a nearly planar macrocyclic framework with a cavity surrounded by three carbonyl groups. In contrast, the corresponding tetramer had a nonplanar macrocyclic framework. 1H NMR measurements showed that the trimer formed a 1 : 1 complex as a macrocyclic host with dihydric phenol guests, and the association constants were determined to be ca. 1.0×103 L mol−1 for hydroquinone or resorcinol guests in CDCl3 at 298 K. The calculated structures of these complexes by the DFT method supported the presence of two sets of OH⋅⋅⋅O=C hydrogen bonds between the host and guest molecules. The spectroscopic data of the cyclic trimers and tetramers are compared with those of reference acridone compounds. 相似文献