全文获取类型
收费全文 | 1028篇 |
免费 | 13篇 |
专业分类
化学 | 747篇 |
晶体学 | 10篇 |
力学 | 7篇 |
数学 | 127篇 |
物理学 | 150篇 |
出版年
2021年 | 7篇 |
2019年 | 6篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 49篇 |
2012年 | 36篇 |
2011年 | 32篇 |
2010年 | 31篇 |
2009年 | 30篇 |
2008年 | 60篇 |
2007年 | 57篇 |
2006年 | 47篇 |
2005年 | 61篇 |
2004年 | 40篇 |
2003年 | 48篇 |
2002年 | 64篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 19篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1994年 | 14篇 |
1993年 | 4篇 |
1992年 | 15篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 28篇 |
1983年 | 9篇 |
1982年 | 28篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1975年 | 21篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1968年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有1041条查询结果,搜索用时 203 毫秒
991.
Four new 8-O-4' type neolignan glycosides with enantiometric aglycones, (7S,8R)-erythro-guaiacylglycerol-beta-O-4'-sinapyl ether 9-O-beta-D-glucopyranoside (1), (7R,8S)-erythro-guaiacylglycerol-beta-O-4'-sinapyl ether 9-O-beta-D-glucopyranoside (2), (7S,8R)-erythro- syringylglycerol-beta-O-4'-sinapyl ether 9-O-beta-D-glucopyranoside (3) and (7R,8S)-erythro- syringylglycerol-beta-O-4'-sinapyl ether 9-O-beta-D-glucopyranoside (4), were isolated from the leaves of Osmanthus ilicifolius. Their structures were established on the basis of NMR, circular dichroism (CD), MS and chemical data. The NMR assignments for the compounds were carried out using (1)H, (13)C, COSY, HMQC, HMBC and NOESY NMR experiments. 相似文献
992.
Dynamical visualization of "coffee stain phenomenon" in droplets of polymer solution via fluorescent microscopy 总被引:1,自引:0,他引:1
Kajiya T Kaneko D Doi M 《Langmuir : the ACS journal of surfaces and colloids》2008,24(21):12369-12374
In the drying process of polymer solution droplets, we propose an experimental procedure for visualizing the solute concentration profile by combining the fluorescent microscopy with the lateral profile observation. We have conducted a dynamical observation of the transport process of the solute polymer toward the edge that causes the "coffee stain phenomenon". We have found that the polymer concentration increases sharply near the edge, while it remains almost constant in the central region until the last stage of drying. The method is useful to understand the dynamical process that occurs near the contact line. 相似文献
993.
994.
A cationic rhodium(I)/H(8)-BINAP complex catalyzes codimerization of alkenes bearing no alpha-hydrogen and electron-deficient internal alkynes, leading to 1,3-dienes in good yields with moderate to excellent regio- and stereoselectivity. The same complex also catalyzes codimerization of an acrylate and phenyl-substituted electron-rich internal alkynes, leading to 1,3-dienes. 相似文献
995.
A cationic rhodium(I)/rac-BINAP complex catalyzes chemo- and regioselective formal cross-cyclotrimerizations of alkynes with enol ethers or acetates. Commercially available and cheap liquid enol ethers and acetates could be used as convenient gaseous alkyne equivalents in the present rhodium catalyses. 相似文献
996.
Stanislav Jure?ka Hikaru Kobayashi Woo-Byoung Kim Masao Takahashi Emil Pin?ík 《Central European Journal of Physics》2012,10(1):210-217
The quality of the interface region in a semiconductor device and the density of interface states (DOS) play important roles
and become critical for the quality of the whole device containing ultrathin oxide films. In the present study the metal-oxide-semiconductor
(MOS) structures with ultrathin SiO2 layer were prepared on Si(100) substrates by using a low temperature nitric acid oxidation of silicon (NAOS) method. Carrier
confinement in the structure produces the space quantization effect important for localization of carriers in the structure
and determination of the capacitance. We determined the DOS by using the theoretical capacitance of the MOS structure computed
by the quantum mechanical approach. The development of the density of SiO2/Si interface states was analyzed by theoretical modeling of the C-V curves, based on the superposition of theoretical capacitance
without interface states and additional capacitance corresponding to the charges trapped by the interface states. The development
of the DOS distribution with the passivation procedures can be determined by this method. 相似文献
997.
Iwamatsu M 《The Journal of chemical physics》2012,136(4):044701
Parallel and series nucleation are the basic elements of the complex nucleation process when two saddle points exist on the free-energy landscape. It is pointed out that the nucleation rates follow formulas similar to those of parallel and series connection of resistors or conductors in an electric circuit. Necessary formulas to calculate individual nucleation rates at the saddle points and the total nucleation rate are summarized, and the extension to the more complex nucleation process is suggested. 相似文献
998.
Uemura Y Inada Y Niwa Y Kimura M Bando KK Yagishita A Iwasawa Y Nomura M 《Physical chemistry chemical physics : PCCP》2012,14(7):2152-2158
Formation and oxidation processes of PdZn nanoparticles on ZnO were successfully observed by means of in situ time-resolved X-ray absorption fine structure spectroscopy (XAFS), and the analysis of data on near-edge (XANES) and extended (EXAFS) structures revealed detailed changes in Pd during both processes. PdZn nanoparticles were formed on ZnO through a two-step scheme under a hydrogen atmosphere. The first process was the formation of metallic Pd nanoparticles, which was quickly finished within 1 s. The second process was the formation of PdZn nanoparticles, which took several tens of minutes. Oxidation of the PdZn nanoparticles also consisted of two processes. Zn atoms were oxidized prior to Pd atoms and the metallic Pd nanoparticles surrounded by ZnO were formed afterwards. Oxidation of the metallic Pd nanoparticles was scarce and very slow. According to the results of kinetic analyses, the metallic Pd surrounded by ZnO was a stable species under the oxidative atmosphere. 相似文献
999.
1000.