全文获取类型
收费全文 | 1679篇 |
免费 | 17篇 |
国内免费 | 3篇 |
专业分类
化学 | 1263篇 |
晶体学 | 21篇 |
力学 | 14篇 |
数学 | 119篇 |
物理学 | 282篇 |
出版年
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 15篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 21篇 |
2014年 | 15篇 |
2013年 | 89篇 |
2012年 | 47篇 |
2011年 | 79篇 |
2010年 | 42篇 |
2009年 | 49篇 |
2008年 | 72篇 |
2007年 | 87篇 |
2006年 | 78篇 |
2005年 | 80篇 |
2004年 | 78篇 |
2003年 | 73篇 |
2002年 | 80篇 |
2001年 | 51篇 |
2000年 | 29篇 |
1999年 | 23篇 |
1998年 | 17篇 |
1997年 | 29篇 |
1996年 | 18篇 |
1995年 | 22篇 |
1994年 | 25篇 |
1993年 | 14篇 |
1992年 | 26篇 |
1991年 | 30篇 |
1990年 | 18篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 23篇 |
1986年 | 25篇 |
1985年 | 27篇 |
1984年 | 36篇 |
1983年 | 13篇 |
1982年 | 21篇 |
1981年 | 25篇 |
1980年 | 30篇 |
1979年 | 35篇 |
1978年 | 25篇 |
1977年 | 14篇 |
1976年 | 19篇 |
1975年 | 22篇 |
1974年 | 16篇 |
1973年 | 8篇 |
1972年 | 12篇 |
1969年 | 8篇 |
排序方式: 共有1699条查询结果,搜索用时 0 毫秒
181.
Harada T Nakagawa Y Ogura T Yamada Y Ohe T Miyagawa H 《Journal of chemical information and modeling》2011,51(2):296-305
Insect growth is regulated by the orchestrated event of ecdysteroids and their receptor proteins. Agonists/antagonists of ecdysteroid receptor are predicted to disrupt normal growth, providing good candidates of new insecticides. A database of over 2 million compounds was subjected to a shape-based virtual screening cascade to identify novel nonsteroidal hits similar to the known EcR ligand ponasterone A. Testing revealed micromolar hits against two strains of insect cells. Docking experiments against EcR were used to support the predicted binding mode of these ligands based on their overlay to ponasterone A. 相似文献
182.
Liu SY Alnama K Matsumoto J Nishizawa K Kohguchi H Lee YP Suzuki T 《The journal of physical chemistry. A》2011,115(14):2953-2965
We performed He I ultraviolet photoelectron spectroscopy (UPS) of jet-cooled aromatic molecules using a newly developed photoelectron imaging (PEI) spectrometer. The PEI spectrometer can measure photoelectron spectra and photoelectron angular distributions at a considerably higher efficiency than a conventional spectrometer that uses a hemispherical energy analyzer. One technical problem with PEI is its relatively high susceptibility to background electrons generated by scattered He I radiation. To reduce this problem, we designed a new electrostatic lens that intercepts background photoelectrons emitted from the repeller plate toward the imaging detector. An energy resolution (ΔE/E) of 0.735% at E = 5.461 eV is demonstrated with He I radiation. The energy resolution is limited by the size of the ionization region. Trajectory calculations indicate that the system is capable of achieving an energy resolution of 0.04% with a laser if the imaging resolution is not limited. Experimental results are presented for jet-cooled benzene and pyridine, and they are compared with results in the literature. 相似文献
183.
Monitoring the aggregation processes of amyloid-β using a spin-labeled, fluorescent nitroxyl radical
Mito F Yamasaki T Ito Y Yamato M Mino H Sadasue H Shirahama C Sakai K Utsumi H Yamada K 《Chemical communications (Cambridge, England)》2011,47(17):5070-5072
Amyloid nitroxyl radical (nitroxide) ligands were used to detect amyloid-β fibrils, the main constituents of senile plaques in Alzheimer's disease, using anisotropic ESR spectra, and were found to affect the aggregation process due to the radical functionality. These compounds have great potential as novel and multifunctional probes, combining spin labels, spin probes, and fluorescence probes. 相似文献
184.
185.
Kiyoshi Hosono 《Discrete Mathematics》2011,(17):1886
Let P be a finite set of points in general position in the plane. We evaluate the ratio between the maximum area of an empty triangle of P and the area of the convex hull of P. 相似文献
186.
187.
K. Ogura T. Hattori M. Hirata M. Asano M. Yoshida M. Tamada H. Omichi N. Nagaoka H. Kubota R. Katakai 《Radiation measurements》1995,25(1-4):159-162
Several types of copolymers of CR-39 were prepared to find its usefulness as a nuclear track detector of high sensitivity. Track responses of these copolymers were investigated by irradiating energetic ions from proton through Ar. The copolymer of CR-39 monomer with N-isopropylacrylamide (NIPAAm) shows higher sensitivity than that of pure CR-39 for low LET particles such as protons. Preliminary results are reported for the track responses of copolymers (CR-39/NIPAAm) with various contents of NIPAAm as well as the etching properties. 相似文献
188.
Matsuyama Kiyoshi Mishima Kenji Hayashi Ken-ichiro Matsuyama Hideto 《Journal of nanoparticle research》2003,5(1-2):87-95
A novel preparation method is reported for the microencapsulation of TiO2 nanoparticles by rapid expansion of supercritical solution with a nonsolvent. A suspension of TiO2 nanoparticles in carbon dioxide containing a cosolvent and dissolved polymer is sprayed through a nozzle to atmospheric pressure. After rapid expansion, polymer microspheres were obtained. The microspheres do not tend to agglomerate, since the pure cosolvent is a nonsolvent for the polymer. The structure and morphology of microspheres were investigated by SEM, TEM and XRD. The obtained polymer microspheres are microcapsules of TiO2 nanoparticles. The mean particle diameter and particle size distribution of microcapsules, could be controlled by changing the polymer concentration, pre-expansion pressure, temperature and injection distance. The polymer feed compositions are more effective than other factors on the control of particle size. 相似文献
189.
Minami K. Ogura K. Aiba Y. Amin M.R. Zheng X.D. Watanabe T. Carmel Y. Destler W.W. Granatstein V.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(2):124-132
We study the starting conditions for a large diameter (diameter/wavelength=4.8) finite length backward wave oscillator designed for 24-GHz operation at the fundamental TM01 mode. This geometry is very promising for high power handling capability. We analyze two separate threshold conditions. First, finite length effects give rise to a threshold in electron beam energy below which oscillations cannot be sustained at any beam current. The second is the more familiar current threshold known as a start current. It is also found that the growth rate for the fundamental mode can be much larger than those of other higher order modes thus leading to coherent operation of large diameter sources free from mode competition 相似文献
190.
A. Sagisaka A.S. Pirozhkov H. Daido A. Fukumi Z. Li K. Ogura A. Yogo Y. Oishi T. Nayuki T. Fujii K. Nemoto S. Orimo M. Nishiuchi Y. Hayashi M. Mori M. Kado S. Nakamura A. Noda I.W. Choi J.H. Sung D.-K. Ko J. Lee 《Applied physics. B, Lasers and optics》2006,84(3):415-419
A two-color interferometer for preformed plasma characterization is developed. We observe the electron density distribution of preformed plasmas on a 5 μm-thick copper target irradiated with a high-intensity Ti:sapphire laser. The two-color interferometer extended the observable electron density region using a fundamental (800 nm) probe beam to cover the lower density region and a second harmonic (400 nm) probe beam to cover the higher density region, simultaneously. This characterization of the electron density distribution of preformed plasmas with femtosecond time resolution significantly contributes to the understanding of high-intensity laser–thin-foil interactions during high-energy electron, ion, and X-ray generation. PACS 52.38.-r; 52.50.Jm; 52.70.-m 相似文献