全文获取类型
收费全文 | 2237篇 |
免费 | 79篇 |
国内免费 | 11篇 |
专业分类
化学 | 1787篇 |
晶体学 | 27篇 |
力学 | 18篇 |
数学 | 133篇 |
物理学 | 362篇 |
出版年
2023年 | 17篇 |
2022年 | 29篇 |
2021年 | 31篇 |
2020年 | 42篇 |
2019年 | 50篇 |
2018年 | 24篇 |
2017年 | 19篇 |
2016年 | 50篇 |
2015年 | 38篇 |
2014年 | 62篇 |
2013年 | 107篇 |
2012年 | 146篇 |
2011年 | 146篇 |
2010年 | 89篇 |
2009年 | 65篇 |
2008年 | 150篇 |
2007年 | 119篇 |
2006年 | 129篇 |
2005年 | 137篇 |
2004年 | 138篇 |
2003年 | 108篇 |
2002年 | 85篇 |
2001年 | 33篇 |
2000年 | 27篇 |
1999年 | 24篇 |
1998年 | 14篇 |
1997年 | 26篇 |
1996年 | 25篇 |
1995年 | 17篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 24篇 |
1980年 | 20篇 |
1979年 | 23篇 |
1978年 | 13篇 |
1977年 | 23篇 |
1976年 | 18篇 |
1974年 | 8篇 |
1973年 | 10篇 |
排序方式: 共有2327条查询结果,搜索用时 15 毫秒
91.
Y Igarashi K Aoki H Nishimura I Morishita K Usui 《Chemical & pharmaceutical bulletin》2012,60(8):1088-1091
Here, we describe the first total synthesis of hydroxyl-α- and hydroxyl-β-sanshool, which involves Suzuki-Miyaura coupling (SMC). Hydroxy-α-sanshool (1) was synthesized by SMC of bromoalkyne 4 with boronate 3 followed by (Z)-selective reduction of the triple bond in the coupling product. Hydroxy-β-sanshool (2) was synthesized by regio- and (E)-selective conversion of 4 to iodoalkene 11 followed by SMC with 3. 相似文献
92.
Generation of Aryl(2‐lithiophenyl)methanone O‐Methyl Oximes and Their Use for the Synthesis of N‐(3‐Alkyl‐1‐aryl‐ or 1,3‐diaryl‐1H‐isoindol‐1‐yl)‐O‐methylhydroxylamines via the Reaction with Nitriles 下载免费PDF全文
Kazuhiro Kobayashi Kota Matsumoto Yuu Shirai Hiroaki Ishikawa Hiroki Inouchi Miyuki Tanmatsu 《Helvetica chimica acta》2014,97(7):915-922
An efficient two‐step procedure for the preparation of a new type of 1H‐isoindoles, i.e., N‐(3‐alkyl‐1‐aryl‐ or 1,3‐diaryl‐1H‐isoindol‐1‐yl)‐O‐methylhydroxylamines 5 , from readily available aryl(2‐bromophenyl)methanones 1 has been developed. Aryl(2‐bromophenyl)methanone O‐methyloximes 2 , derived from the corresponding ketones, were treated with BuLi in Et2O at 0° to generate novel lithium compounds, aryl(2‐lithiophenyl)methanone O‐methyloximes 3 , which were allowed to react with nitriles to give the desired products 5 in moderate‐to‐fair yields. 相似文献
93.
Ha J Seo HY Shim YS Nam HJ Seog H Ito M Nakagawa H 《Journal of AOAC International》2010,93(6):1905-1911
A sensitive and specific heating block method coupled with ultra-HPLC (u-HPLC) was developed for the analysis of capsaicin in Gochujang and validated by comparing with a conventional HPLC (AOAC Method 995.03). The method validation parameters yielded good results, including linearity, precision, accuracy, and recovery. The u-HPLC separation was performed on a reversed C18 column (50 x 2 mm id, particle size 2 microm), followed by fluorescence detection (excitation 280 nm, emission 325 nm). Methanol was used as the extracting solvent, and the amount of sample taken was approximately 0.2 g; the optimum amount of extraction solvent and extraction time were 15 mL and 1 h, respectively. The recovery of capsaicin in Gochujang was more than 93%, and the LOD and LOQ of the u-HPLC analysis were 0.05 and 0.16 microg/g for capsaicin and 0.05 and 0.16 microg/g for dihydrocapsaicin. The calibration graphs for capsaicin and dihydrocapsaicin were linear from 0.2 to 10.0 microg/mL for u-HPLC. The interday and intraday precisions (RSD values) were < 6.27%. 相似文献
94.
Sanjay S. Latthe Hiroaki Imai V. Ganesan Charles Kappenstein A. Venkateswara Rao 《Journal of Sol-Gel Science and Technology》2010,53(2):208-215
Optically transparent silica films were prepared at room temperature (~27°C) by keeping the molar ratio of TEOS:MeOH:H2O (0.001 M NH4F) constant at 1:19.29:6.20, respectively. A surface chemical modification of the films was done with alkylchlorosilanes at
different concentrations from 0 to 1 vol. % and aging times varied from half to 2 h. The DMCS and TMCS surface modified silica
films showed the static water contact angle of 146° and 162°, respectively. When the DMCS and TMCS modified films were cured
at temperatures higher than 240 and 275°C, respectively, the films became superhydrophilic. Further, the humidity study was
carried out at a relative humidity of 90% at 30°C temperature over 60 days. We characterized the water repellent silica films
by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, % of optical transmission,
humidity tests and contact angle measurements. 相似文献
95.
Hiroaki Aizawa Ken Hatano Hitoshi Saeki Nobuaki Honsho Tetsuo Koyama Koji Matsuoka Daiyo Terunuma 《Tetrahedron letters》2010,51(12):1545-6442
A new compound having a 2,3,4,5-tetraphenylsilole derivative on the center silicon of Dumbbell(1)6Gb3; Silole-Dumbbell(1)6Gb3 (1) was previously reported. It was found that 1 exhibited strongly increased fluorescence both in water and in a 96% acetone/water mixed solvent. The physical behavior of 1 in water and in the 96% acetone/water mixed solvent was investigated, and analyses including fluorescence quantum yields, dynamic-light-scattering (DLS), atomic-force-microscopy (AFM), and fluorescence microscopy were carried out. It was clarified that 1 dynamically formed different types of aggregates in water and in higher acetone concentrations to yield high aggregation-induced emission (AIE) effects due to the formation of micelle-like particles in water and inversion-type micelles in the acetone/water mixed solvent, respectively. 相似文献
96.
Takenaka S Susuki N Miyamoto H Tanabe E Matsune H Kishida M 《Chemical communications (Cambridge, England)》2010,46(47):8950-8952
Pd cathode catalysts for polymer electrolyte fuel cells have been covered with silica layers a few nanometres thick. The silica-coated Pd catalysts showed high activity and excellent durability for the oxygen reduction under the severe cathode conditions of PEFCs, while Pd catalysts without silica-coating were seriously deactivated under the same conditions. The coverage of Pd metal with silica prevents the diffusion of Pd species out of the silica layers. 相似文献
97.
A method in which antibodies are produced by using an immunogen heterogeneously conjugated with two or more kinds of haptens having unlike chemical structures against a same carrier protein was offered as an efficient approach for development of antibody to low molecular compounds. To appreciate the potentiality of the approach, 17β-estradiol (E2) and testosterone were selected as model compounds. The I50 values of antiserum developed were 6 and 8 μg L−1 with the detection limits of 0.02 and 0.15 μg L−1 for E2 and testosterone, respectively. Antiserum owned an interesting characteristic that it was possible to independently analyze E2 and testosterone without mutual interference by making proper use of coating antigens. When using β-estradiol 17-hemisuccuinate (EH) conjugated with bovine serum albumin (BSA) as a coating antigen, the enzyme-linked immunosorbent assay (ELISA) was very selective to E2 and some estrogen analogues. Therefore, if testosterone coexisted in the ELISA for E2 detection, it showed no interference with it. From these findings, it was suggested that the verified method was an efficient and rational approach in development of polyclonal antibody to low molecular compounds. 相似文献
98.
Kuniaki Tatsuta Hiroaki Tanaka Hitomi Tsukagoshi Takafumi Kashima Seijiro Hosokawa 《Tetrahedron letters》2010,51(42):5546-5549
The total synthesis of lactonamycin has been achieved. The synthesis includes sequential intramolecular conjugate addition of alcohols to the acetylenic ester, stereoselective glycosylation of the tertiary alcohol, and Michael-Dieckmann type cyclization with the thioester, by which the highly convergent route has been established. 相似文献
99.
Crown ether-type macrocycles consisting of an enantiopure biarenol derivative and an oligoethylene glycol were synthesized by the Lewis acid-mediated tandem Claisen rearrangement. This is the first example of the successful application of the tandem Claisen rearrangement to the synthesis of enantiopure macrocyclic biarenol derivatives. The enantiopure macrocyclic biarenols were found to form 1:1 complexes with amino acid salts and to discriminate their chirality. 相似文献
100.
Direct Observation of Ordered High‐Spin–Low‐Spin Intermediate States of an Iron(III) Three‐Step Spin‐Crossover Complex 下载免费PDF全文
Dr. Zhao‐Yang Li Dr. Hiroyoshi Ohtsu Dr. Tatsuhiro Kojima Dr. Jing‐Wei Dai Takefumi Yoshida Dr. Brian K. Breedlove Dr. Wei‐Xiong Zhang Dr. Hiroaki Iguchi Prof. Osamu Sato Prof. Masaki Kawano Prof. Masahiro Yamashita 《Angewandte Chemie (International ed. in English)》2016,55(17):5184-5189
A neutral mononuclear FeIII complex [FeIII(H‐5‐Br‐thsa‐Me)(5‐Br‐thsa‐Me)]?H2O ( 1 ; H2‐5‐Br‐thsa‐Me=5‐bromosalicylaldehyde methylthiosemicarbazone) was prepared that exhibited a three‐step spin‐crossover (SCO) with symmetry breaking and a 14 K hysteresis loop owing to strong cooperativity. Two ordered intermediate states of 1 were observed, 4HS–2LS and 2HS–4LS, which exhibited reentrant phase‐transition behavior. This study provides a new platform for examining multistability in SCO complexes. 相似文献