全文获取类型
收费全文 | 1152篇 |
免费 | 27篇 |
国内免费 | 4篇 |
专业分类
化学 | 896篇 |
晶体学 | 5篇 |
力学 | 8篇 |
数学 | 85篇 |
物理学 | 189篇 |
出版年
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 22篇 |
2015年 | 17篇 |
2014年 | 21篇 |
2013年 | 46篇 |
2012年 | 55篇 |
2011年 | 73篇 |
2010年 | 36篇 |
2009年 | 38篇 |
2008年 | 56篇 |
2007年 | 79篇 |
2006年 | 78篇 |
2005年 | 50篇 |
2004年 | 59篇 |
2003年 | 67篇 |
2002年 | 63篇 |
2001年 | 20篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 15篇 |
1997年 | 8篇 |
1996年 | 22篇 |
1995年 | 5篇 |
1994年 | 20篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1973年 | 7篇 |
1972年 | 4篇 |
1969年 | 7篇 |
1968年 | 4篇 |
排序方式: 共有1183条查询结果,搜索用时 31 毫秒
91.
92.
Kiminori Itoh Tohru Okamoto Shuhei Wakita Hiroshi Niikura Masayuki Murabayashi 《应用有机金属化学》1991,5(4):295-301
Thin films of peroxohetero(carbon)polytungstic acid (CW-HPA) and carbon-free isopolytungstic acid (W-IPA) were prepared, and examined in terms of optical and etching properties. Thermal decomposition was found to give good results in removing excess hydrogen peroxide (H2O2) during the preparation of CW-HPA and W-IPA. It was shown for the first time that thin films of CW-HPA and W-IPA have very high refractive indices (larger than 2.0) when sufficiently dried. Optical waveguide (OWG) characteristics of these films were examined using a slab-type OWG structure and ARROW (Antiresonance Reflection Optical Waveguide)-type structures. An embossing technique was applied to make diffractional grating couplers. 相似文献
93.
Y. Kamii I. Waki H. Fujioka M. Oshima H. Miki M. Okuyama 《Applied Surface Science》2002,190(1-4):348-351
Electrical characteristics of Mg-doped p-GaN activated with Ni catalytic layers have been investigated by means of temperature-dependent Hall effect measurements. It has been revealed that the Ni layer on GaN enhances activation of the acceptor in the whole annealing temperature range. This enhancement is remarkable especially at temperatures below 500 °C and can be attributed to the catalytic effect for the hydrogen desorption. We have found that the donor concentrations in the samples activated with the Ni catalysts are also higher than those activated without Ni. This is probably due to the catalytic effect of Ni for the nitrogen desorption. In addition, it has been found that the ionization energies of the Mg acceptors in GaN activated with the Ni layer are decreased from 170 to 118 meV as the acceptor concentration increases. 相似文献
94.
The exchange interaction in the radical pair in homogeneous solution has been investigated by using the CIDNP method. The experimental observations of the multiplet pattern were compared with the theoretical simulations in which the exchange integral was a variable parameter. The results show that 2-propanol is a unique solvent in that the exchange integral in the radical pair in this solvent is large. 相似文献
95.
96.
Koji Umeda Takahiro Hanamuro Kunimi Yamada Yoshimitsu Negishi Hideki Iwano Tohru Danhara 《Radiation measurements》2007,42(10):1647-1654
97.
Formal Synthesis of Sarain A: Intramolecular Cycloaddition of an Eight‐Membered Cyclic Nitrone to Construct the 2‐Azabicyclo[3.3.1]nonane Framework
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. Takuya Higo Tomoya Ukegawa Dr. Satoshi Yokoshima Prof. Tohru Fukuyama 《Angewandte Chemie (International ed. in English)》2015,54(25):7367-7370
An enantioselective route to the tetracyclic skeleton of sarain A has been developed. Asymmetric reduction of an ynone introduced a chiral center which was transferred to the contiguous tertiary stereogenic centers through an Ireland–Claisen rearrangement. The 2‐azabicyclo[3.3.1]nonane framework was constructed by an unprecedented intramolecular cycloaddition of an eight‐membered cyclic nitrone. Using the steric bias of the bicyclic system, the quaternary carbon atom was constructed by a stereoselective aldol reaction. Further ring formations were performed by ring‐closing metathesis for the 13‐membered ring and an iodoamidation reaction for the pyrrolidine ring. The present synthesis has successfully provided an alternative route to the late‐stage intermediate of Overman’s synthesis. 相似文献
98.
Ryota Inoue Masashi Hasegawa Tohru Nishinaga Kenji Yoza Yasuhiro Mazaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(9):2772-2776
A series of thiacalix[n]dithiothiophenes (n=4–10) was prepared by a facile method and X‐ray analysis was used to determine the molecular structures of square‐ (4‐mer) and pentagonal‐shaped macrocycles (5‐mer). In the cyclic voltammograms, reversible multielectron redox processes, which are due to electronic delocalization, were observed at low oxidation potentials. The cyclic 4‐mer acted as a “Janus‐head” cavitand for two C60 molecules, whereas the 5‐ and 6‐mer formed stable 1:1 complexes with C60 . 相似文献
99.
Cover Picture: A Modular Synthesis of Conformationally Preorganised Extended β‐Strand Peptidomimetics (Chem. Eur. J. 42/2015)
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
100.
Jo Yong-Hyun Joshi Bhupendra Sekino Tohru Kim Tae-Ho Lee Soo-Wohn 《Research on Chemical Intermediates》2017,43(9):5261-5269
Research on Chemical Intermediates - A comparative study was carried out on the photocatalytic properties depending on Jodifferent morphologies of Ag3PO4 fabricated by different methods, i.e. as... 相似文献