全文获取类型
收费全文 | 1093篇 |
免费 | 51篇 |
国内免费 | 5篇 |
专业分类
化学 | 874篇 |
晶体学 | 27篇 |
力学 | 17篇 |
数学 | 40篇 |
物理学 | 191篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 24篇 |
2019年 | 26篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 25篇 |
2015年 | 24篇 |
2014年 | 33篇 |
2013年 | 51篇 |
2012年 | 51篇 |
2011年 | 62篇 |
2010年 | 36篇 |
2009年 | 30篇 |
2008年 | 66篇 |
2007年 | 55篇 |
2006年 | 66篇 |
2005年 | 81篇 |
2004年 | 48篇 |
2003年 | 59篇 |
2002年 | 54篇 |
2001年 | 30篇 |
2000年 | 34篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 23篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1973年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有1149条查询结果,搜索用时 15 毫秒
81.
Md. Khorshed Alam Ryuji Miura Hideyuki Tsuboi Akira Endou Momoji Kubo 《Applied Surface Science》2010,257(5):1383-1389
Ceria plays an important role in catalysis, due to its ability to store and release oxygen depending on the condition present in the catalyst environment. To analyze the role of ceria in catalytic reactions, it is necessary to know the details of the interaction of ceria surface with environmentally sensitive molecules. This study was conducted using ultra accelerated quantum chemical molecular dynamics. Its purpose was to investigate the reduction process of the (1 1 1) and (1 1 0) surfaces of ceria with atomic hydrogen as well as water desorption mechanisms from the surfaces. This simulation demonstrated that when a high-energy colliding hydrogen atoms are adsorbed on the ceria, it pulls up an O atom from the ceria surfaces and results in the formation of a H2O molecule. This is the first dynamics simulation related to such reduction processes based on quantum chemistry. 相似文献
82.
Norihiko Minami 《Proceedings of the American Mathematical Society》2002,130(5):1557-1562
Let be a space of finite type. Set as usual, and define the mod support of by for 0.$"> Call sparse if there is no with
Then we show the relation for any finite type space with being sparse.
As a special case, we have and the main theorem of Ravenel, Wilson and Yagita is also generalized in terms of the mod support.
83.
In the presence of catalytic amounts of Cp*Ru(cod)Cl, unsymmetrical 1,6-diynes possessing a variety of functional groups reacted with electron-deficient tricarbonyl compounds at the ketone C=O double bonds to selectively afford dienones via electrocyclic ring opening of the expected alpha-pyrans. The intramolecular Michael addition of the cycloadducts having an acetyl and an alkylidenemalonate moiety gave bicyclo[3.3.0]octenone derivatives. 相似文献
84.
Hong FL Minoshima K Onae A Inaba H Takada H Hirai A Matsumoto H Sugiura T Yoshida M 《Optics letters》2003,28(17):1516-1518
A frequency comb spanning more than one octave has been achieved by injecting the second-harmonic generation (780 nm) of a mode-locked fiber laser (1.56 microm) into a photonic crystal fiber. We propose and realize a novel interferometric scheme for observing the carrier-envelope offset frequency of the frequency comb. Frequency noise has been observed on the measured carrier-envelope offset frequency, which has been confirmed to be generated in the photonic crystal fiber by comparing the measured beat frequencies between cw lasers and frequency combs before and after the photonic crystal fiber. The mode-locked fiber laser is considered to be an important candidate for the light source used in realizing a compact optical frequency measurement system including applications in the telecommunication bands. 相似文献
85.
Tobe M Isobe Y Tomizawa H Nagasaki T Aoki M Negishi T Hayashi H 《Chemical & pharmaceutical bulletin》2003,51(9):1109-1112
We investigated the chemical modifications of the nitroquinazoline derivative (1) through the replacement of the NH group at the C(4)-position with several N-alkyl groups to increase the lipophilicity at the C(4)-position. Among them, we found that the N-methyl analogue (5a) showed a 2-fold loss in the inhibitory activity toward tumor necrosis factor-alpha (TNF-alpha) production in vitro as compared with the NH analogue (1); however, 5a exhibited an oral inhibitory activity on TNF-alpha production with an ED50 value of 26 mg/kg, whereas 1 did not. Moreover, the oral bioavailability of 5a was higher than that of 1 (1, F=1%; 5a, F=21%), and the calculated ClogP value for 5a was higher than that for 1. These results suggest that the improved lipophilicity of 5a compared with that of 1 reflects its greater inhibitory activity on TNF-alpha production in vivo as well as oral bioavailability. 相似文献
86.
Ida K Funaba H Kado S Narihara K Tanaka K Takeiri Y Nakamura Y Ohyabu N Yamazaki K Yokoyama M Murakami S Ashikawa N deVries PC Emoto M Goto M Idei H Ikeda K Inagaki S Inoue N Isobe M Itoh K Kaneko O Kawahata K Khlopenkov K Komori A Kubo S Kumazawa R Liang Y Masuzaki S Minami T Miyazawa J Morisaki T Morita S Mutoh T Muto S Nagayama Y Nakanishi H Nishimura K Noda N Notake T Kobuchi T Ohdachi S Ohkubo K Oka Y Osakabe M Ozaki T Pavlichenko RO Peterson BJ Sagara A Saito K Sakakibara S Sakamoto R 《Physical review letters》2001,86(23):5297-5300
Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss. 相似文献
87.
傅元勇 周书华T. Koike S. Kinoshita Y. Ma Y. Miura K. Miwa Y. Miyagi K. Shirotori T. Suzuki H. Tamura K. Tsukada M. Ukai K. Futatsukawa K. Hosomi M. Kawai M. Mimori N. Terada N. Maruyama K. Aoki H Fujioka Y Kakiguchi T. Nagae D. Nakajima H Noumi T Takahashi T.N. Takahashi A. Toyota M. Dairaku T. Fukuda S. Minami W. Imoto S. Aiimura K. Tanida 《中国物理快报》2007,24(8):2216-2218
From the ^12 C(π^+,K^+)^12 AC reaction the γ -rays of 261.6±0.24 ke V(7/2^+ →5/2^+)and 1481.7±0.7 ke V(1/2^+ →5/2^+) of ^11 A B,and 2667.3±2.8 keV(1^- 2 → 2^- 1)of ^12 A C hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7keV and 261.6 keV are significantly different from the values predicted by the shell model using the △ and SN parameters determined from the ^7 △ Li data. 相似文献
88.
89.
Micron-sized monodispersed polystyrene (PS)/poly(3,5-xylidine) (PXy) composite particles were produced by chemical oxidative
seeded dispersion polymerization of 3,5-xylidine at 20 °C with 1.6-μm-sized monodispersed PS seed particles in HCl aqueous
solution, the pH of which was always kept at 2.5 with a pH stat. The composite particles produced consisted of a PS core and
a PXy shell.
Received: 16 December 1998 Accepted in revised form: 25 March 1999 相似文献
90.