全文获取类型
收费全文 | 477篇 |
免费 | 24篇 |
国内免费 | 2篇 |
专业分类
化学 | 391篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 16篇 |
物理学 | 91篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 22篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 30篇 |
2012年 | 37篇 |
2011年 | 28篇 |
2010年 | 12篇 |
2009年 | 19篇 |
2008年 | 34篇 |
2007年 | 28篇 |
2006年 | 18篇 |
2005年 | 26篇 |
2004年 | 22篇 |
2003年 | 22篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有503条查询结果,搜索用时 15 毫秒
101.
102.
The thermal decomposition of propane was studied behind reflected shock waves over the temperature range 1100–1450 K and the pressure range 1.5–2.6 atm, by both monitoring the time variations of absorption at 3.39 μm and analyzing the concentrations of the reacted gas mixtures. The rate constants of the elementary reactions were discussed from the results. The rate constant expressions, k1 = 1.1 × 1016 exp (?84 kcal/RT) s?1 and k4 = 9.3 × 1013 exp(?8 kcal/RT) cm3 mol?1 s?1, of reactions C3H8 → CH3 + C2H5 and C3H8 + H → n-C3H7 + H2 were evaluated, respectively. 相似文献
103.
Yoshiaki Hidaka Takashi Taniguchi Takashi Kamesawa Hiromitsu Masaoka Koji Inami Hiroyuki Kawano 《国际化学动力学杂志》1993,25(4):305-322
Thermal decomposition of formaldehyde diluted with Ar was studied behind reflected shock waves in the temperature range of 1200–2000 K at total pressures between 1.3 and 3.0 atm. The study was carried out for compositions from the concentrated mixture, 4% CH2O, to the highly dilute mixture, 0.01% CH2O by using time-resolve IR-laser absorption and IR-emission, and a single-pulse technique. From a computer-simulation study, the mechanism and the rate-constant expressions that could explain all of our data and previously reported ARAS data were discussed. This data obtained over a wide concentration range from 50 ppm CH2O to 4% CH2O were satisfactorily modeled by a five-reaction mechanism. © 1993 John Wiley & Sons, Inc. 相似文献
104.
Yoshiaki Hidaka Takuji Nakamura Aya Miyauchi Toshihiko Shiraishi Hiroyuki Kawano 《国际化学动力学杂志》1989,21(8):643-666
Propyne (p-C3H4) or allene (a-C3H4) mixtures, highly diluted with Ar, were heated to the temperature range 1200–1570 K at pressures of 1.7–2.6 atm behind reflected shock waves. The thermal decompositions of propyne and allene were studied by both measuring the profiles of the IR emission at 3.48 μm or 5.18 μm and analyzing the concentrations of reacted gas mixtures. The mechanism and the rate constant expressions were discussed from both the profiles and the concentrations of reactant and products obtained. The rate constant expressions for reactions, (1) p-C3H4 → a-C3H4, (?1) a-C3H4 → p-C3H4, and (5) p-C3H4 + H → CH3 + C2H2 were evaluated. 相似文献
105.
Yutaka Nagai Nakahara Kouji Yoneyama Yoshifumi Kawano Katsuyasu Tanaka Katsumi Nakata Ryouhei 《Journal of Physics and Chemistry of Solids》2004,65(11):1861-1870
The characteristics of high-temperature ionic thermocurrent (HT ITC) in CaF2 doped with different sodium concentrations were studied by the Teflon-insulated electrode ITC method. It was shown that, with increasing sodium concentration, the HT ITC band moved toward a Na+-FV dipole band with a peak at 162 K. The results of analyses of the HT ITC spectra using an equivalent electric circuit proved that the activation energy of space charge migration related to HT ITC was also strongly dependent on the doped sodium concentrations if varied from 0.94 to 0.46 eV with increasing sodium concentration in our ITC study. In addition, the broadening of the Na+-FV dipole band was observed in 3 nominal mole% NaF-doped CaF2, which was accompanied by a considerable decrease of the activation energy from 0.46 to 0.29 eV without showing marked temperature shifts of the peak ITC bands. 相似文献
106.
Tetsuya Tsujihara Sayaka Endo Tsunayoshi Takehara Takeyuki Suzuki Satoru Tamura Tomikazu Kawano 《Tetrahedron letters》2018,59(25):2450-2453
The synthesis of helically chiral [6]helicene-based sulfonic acid and sulfonamide from enantiomerically pure 1-acetylthio-5,6,9,10-tetrahydro[6]helicene is reported. The first helically chiral disulfonimides were developed as a synthetic application of [6]helicene-based sulfonamide. This new class of organocatalysts was tested in an asymmetric Mukaiyama aldol reaction to obtain up to quantitative yields and enantioselectivities up to 24%. 相似文献
107.
Ryo Hirata Ayame Torii Kenichi Kawano Shiroh Futaki Ayumi Imayoshi Kazunori Tsubaki 《Tetrahedron》2018,74(27):3608-3615
Fluorescent dyes possessing a variety of arylacetylenes at the 9-position of a xanthene skeleton were synthesized and their optical properties were investigated. The π system effectively expanded over the xanthene skeleton and the aryl group through the triple bond. Starting from the emission wavelength (λem) of 9-methyl xanthene 20 in basic DMSO solution at 536?nm, the emission wavelengths gradually shifted to the red region for methylacetylene 17 (λem?=?600?nm), phenylacetylene 5 (λem?=?636?nm), and p-CF3-phenylacetylene 11 (λem?=?660?nm). On the basis of these data, we estimated the substituent effects for the red shift on the emission wavelength and rationally explained the results by DFT calculations. Furthermore, potential applicability of these fluorescent dyes to cell staining was exemplified. 相似文献
108.
Docking Strategy To Construct Thermostable,Single‐Crystalline,Hydrogen‐Bonded Organic Framework with High Surface Area
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Ichiro Hisaki Yuto Suzuki Eduardo Gomez Dr. Boiko Cohen Dr. Norimitsu Tohnai Prof. Dr. Abderrazzak Douhal 《Angewandte Chemie (International ed. in English)》2018,57(39):12650-12655
Enhancing thermal and chemical durability and increasing surface area are two main directions for the construction and improvement of the performance of porous hydrogen‐bonded organic frameworks (HOFs). Herein, a hexaazatriphenylene (HAT) derivative that possesses six carboxyaryl groups serves as a suitable building block for the systematic construction of thermally and chemically durable HOFs with high surface area through shape‐fitted docking between the HAT cores and interpenetrated three‐dimensional network. A HAT derivative with carboxybiphenyl groups forms a stable single‐crystalline porous HOF that displays protic solvent durability, even in concentrated HCl, heat resistance up to 305 °C, and a high Brunauer–Emmett–Teller surface area [SA(BET)] of 1288 m2 g?1. A single crystal of this HOF displays anisotropic fluorescence, which suggests that it would be applicable to polarized emitters based on robust functional porous materials. 相似文献
109.
In the case of 38 and 96 kHz ultrasonic vibrating electrode (USVE) voltammetry of chlorpromazine, the oxidation current increased considerably with ultrasonic power (amplitude). Movement of the first oxidation product, crimson coloured cation radical, and the streaming of liquid in the neighbourhood of the USVE, were visually observed in order to understand the mechanism of the promotive effects of ultrasound on the oxidation reaction. The reaction profile of the oxidation of chlorpromazine in 38 kHz seems to be somewhat different from that in 96 kHz. However, the mechanical agitation of solution in the area nearest the electrode surface, which is essentially the same fundamental mechanism, takes place in both the cases of 38 and 96 kHz. Both micro- and macro-streamings due to the vibration of a small bubble on the electrode surface with a frequency lower than that of the ultrasonic wave were formed in 38 kHz. These streamings seemed to contribute to the agitation and the exchange of the solution near the electrode surface. However, at the same ultrasonic amplitude, the oxidation current at 96 kHz was much greater than that at 38 kHz. Such a promoting effect of ultrasound on the electrode reaction was considered to be due to the increase of the moving speed or to the acceleration of the particle in the solution. 相似文献
110.
Shimada Y Akane H Taniguchi N Matsuhisa A Kawano N Tanaka A 《Chemical & pharmaceutical bulletin》2005,53(5):589-590
Stereoselective synthesis of methyl (Z)-(4,4-difluoro-2,3,4,5-tetrahydro-1H-1-benzazepin-5-ylidene)acetate (1a) is described. Z-selectivity of the Horner-Wadsworth-Emmons (HWE) reaction was obtained based on an investigation of the reaction conditions for introduction of a methylidene group onto the 5-position of benzazepine. 相似文献