全文获取类型
收费全文 | 604篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
化学 | 459篇 |
晶体学 | 4篇 |
力学 | 13篇 |
数学 | 39篇 |
物理学 | 111篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 33篇 |
2012年 | 37篇 |
2011年 | 48篇 |
2010年 | 18篇 |
2009年 | 20篇 |
2008年 | 47篇 |
2007年 | 37篇 |
2006年 | 32篇 |
2005年 | 49篇 |
2004年 | 49篇 |
2003年 | 31篇 |
2002年 | 16篇 |
2001年 | 14篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有626条查询结果,搜索用时 15 毫秒
1.
2.
3.
Yuka Kawashita 《Tetrahedron letters》2006,47(25):4231-4233
A variety of 2-arylbenzothiazoles were prepared by the direct reaction of 2-aminobenzenethiol and aryl aldehydes by the aid of activated carbon (Shirasagi KL or Darco® KB) under oxygen atmosphere. 2-Pyridylbenzothiazole, thus obtained, was proved to work as an efficient ligand in palladium-catalyzed Mizoroki-Heck reaction. 相似文献
4.
The interaction of two parallel plane jets of different velocities is studied by flow visualization and PIV measurement to
examine the influence of velocity ratio on the development ofjets in the initial region. It is found that the parallel plane
jets develop toward the high velocity side and the jet width is reduced with a decrease in the jet velocity ratio. Corresponding
to the variation of mean velocity field to the velocity ratio, the magnitudes of turbulence intensities, Reynolds stress and
static pressure are weakened in the merging region of the jets and their peak locations of the properties are shifted to the
high velocity side. These results indicate that the interaction of two parallel jets is weakened with a decrease in the velocity
ratio of the jets. 相似文献
5.
6.
Hidenori Hanaoka Yuka Imamoto Takahiro Hino Tetsuya Kohno Kazunori Yanagi Yoshiaki Oda 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3668-3676
Chromium catalysts combined with phosphorous‐bridged bisphenoxy ligands were found to be highly active for ethylene polymerization. The most efficient catalyst precursor among them, generated by combining bis[3‐tert‐butyl‐5‐methyl‐2‐hydroxyphenyl](phenyl)phosphine hydrochloride ( 1a ) and CrCl3(THF)3, was characterized. X‐ray analysis of (3‐tert‐butyl‐5‐methyl‐2‐phenoxy)(3‐tert‐butyl‐5‐methyl‐ 2‐hydroxyphenyl)(phenyl)phosphine bis(tetrahydrofuran)chromium dichloride ( 6 ), obtained by the reaction of 1a and CrCl3(THF)3 in the presence of NaH, revealed a unique structure in which one phenol moiety of the bisphenol did not coordinate to the chromium center. Complex 6 showed higher activities than those observed in the in situ catalyst system. Polyethylene of various molecular weights was obtained with differing activators. The highest activity (113.5 kg mmol (cat)?1 h?1) was observed when TIBA/TB was used as a cocatalyst. A medium molecular weight polymer with narrow molecular weight distribution (Mw = 128,700, Mw/Mn = 1.8) was obtained using a 6 ‐TIBA/B(C6F5)3 system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3668–3676, 2007 相似文献
7.
Li C Lee D Graf TN Phifer SS Nakanishi Y Burgess JP Riswan S Setyowati FM Saribi AM Soejarto DD Farnsworth NR Falkinham JO Kroll DJ Kinghorn AD Wani MC Oberlies NH 《Organic letters》2005,7(25):5709-5712
[chemical reaction: see text]. Three new ent-trachylobane diterpenoids (1-3) were isolated and structures elucidated from Mitrephora glabra Scheff. (Annonaceae). Mitrephorone A (1) possesses a hexacyclic ring system with adjacent ketone moieties and an oxetane ring, both of which are unprecedented among trachylobanes. All compounds were evaluated for cytotoxicity against a panel of cancer cells, where 1 displayed the most potent and broadest activity, and against a battery of antimicrobial assays, where all compounds were approximately equipotent. 相似文献
8.
Summary {\rtf1\ansi\ansicpg1250\deff0\deflang1038\deflangfe1038\deftab708{\fonttbl{\f0\froman\fprq2\fcharset238{\*\fname Times New Roman;}Times New Roman CE;}}
\viewkind4\uc1\pard\f0\fs20 New explanations are given for two types of irregular thermogravimetric (TG) data. A TG relationship between mass and temperature is derived on the basis of migration behavior of bubbles generated in bulk of sample system, and superposed on that derived on the basis of kinetics of the 4\super th\nosupersub order event, which is superposed on the experimental TG data obtained from three reference papers. This suggests that these TG data are reflecting migration of bubbles. A dependence of TG behavior on heating rate, which is contrary to usual that, is shown and is explained in terms of event-rate determination by boiling.
\par } 相似文献
9.
M. Fujisawa T. Matsushita Y. Matsui K. Akasaka T. Kimura 《Journal of Thermal Analysis and Calorimetry》2004,77(1):225-231
The heat capacities of binary aqueous solutions of 1,2-ethanediol, 1,2-propanediol and 1,2-butanediol were measured at temperatures
ranging from 283.15 to 338.15 K by differential scanning calorimetry. The partial molar heat capacities at the infinite dilution
were then calculated for the respective alkanediols. For 1,2-ethanediol or 1,2-propanediol, the partial molar heat capacities
at the infinite dilution of increased with increasing temperature. In contrast, the partial molar heat capacities of 1,2-butanediol
at the infinite dilution decreased with increasing temperature.
Heat capacity changes by dissolution of the alkanediols were also determined. Heat capacity changes caused by the dissolution
of 1,2-ethanediol or 1,2-propanediol were increase with increasing temperature. On the other hand, heat capacity changes caused
by the dissolution of 1,2-butanediol are decrease with increasing temperature. Thus our results indicated that the structural
changes of water caused by the dissolution of 1,2-butanediol differed from that of the two other alkanediols.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
T. Kimura Y. Takahashi T. Kamiyama M. Fujisawa 《Journal of Thermal Analysis and Calorimetry》2007,88(2):587-595
Excess enthalpies (H
E)
of 17 binary mixtures of o- and m-isomers of dichlorobenzene, difluorobenzene, methoxymethylbenzene,
dimethylbenzene, dimethoxybenzene, aminofluorobenzene, fluoronitrobenzene,
diethylbenzene, chlorofluorobenzene, fluoroiodobenzene, bromofluorobenzene,
chloromethylbenzene, fluoromethylbenzene, bromomethylbenzene, iodomethylbenzene,
fluoromethoxybenzene, dibromobenzene at 298.15 K were measured. All excess
enthalpies measured were very small, and those of o-+m-isomers of aminofluorobenzene, dibromobenzene and
iodomethylbenzene were negative but 14 other binary mixtures of isomers were
positive over the whole range of mole fractions. H
E
of o-+m-isomers
of dimethoxybenzene showed the largest enthalpic instability and those of
aminofluorobenzene showed the largest enthalpic stability. There was a correlation
between dipole–dipole interaction, dipole–induced dipole interaction
or entropies of vaporization and excess partial molar enthalpies at infinite
dilution. 相似文献