全文获取类型
收费全文 | 7130篇 |
免费 | 164篇 |
国内免费 | 19篇 |
专业分类
化学 | 5238篇 |
晶体学 | 81篇 |
力学 | 80篇 |
综合类 | 1篇 |
数学 | 352篇 |
物理学 | 1561篇 |
出版年
2022年 | 45篇 |
2021年 | 75篇 |
2020年 | 84篇 |
2019年 | 86篇 |
2018年 | 64篇 |
2017年 | 51篇 |
2016年 | 101篇 |
2015年 | 111篇 |
2014年 | 111篇 |
2013年 | 315篇 |
2012年 | 276篇 |
2011年 | 366篇 |
2010年 | 173篇 |
2009年 | 194篇 |
2008年 | 340篇 |
2007年 | 355篇 |
2006年 | 360篇 |
2005年 | 373篇 |
2004年 | 359篇 |
2003年 | 267篇 |
2002年 | 267篇 |
2001年 | 220篇 |
2000年 | 195篇 |
1999年 | 105篇 |
1998年 | 58篇 |
1997年 | 77篇 |
1996年 | 101篇 |
1995年 | 84篇 |
1994年 | 91篇 |
1993年 | 104篇 |
1992年 | 123篇 |
1991年 | 118篇 |
1990年 | 89篇 |
1989年 | 102篇 |
1988年 | 97篇 |
1987年 | 72篇 |
1986年 | 77篇 |
1985年 | 117篇 |
1984年 | 136篇 |
1983年 | 67篇 |
1982年 | 76篇 |
1981年 | 70篇 |
1980年 | 83篇 |
1979年 | 96篇 |
1978年 | 83篇 |
1977年 | 86篇 |
1976年 | 65篇 |
1975年 | 62篇 |
1974年 | 55篇 |
1973年 | 54篇 |
排序方式: 共有7313条查询结果,搜索用时 31 毫秒
991.
992.
993.
S. Iversen H. Nann A. Obst Kamal K. Seth N. Tanaka C.L. Morris H.A. Thiessen K. Boyer W. Cottingame C. Fred Moore R.L. Boudrie D. Dehnhard 《Physics letters. [Part B]》1979,82(1):51-54
π+ and π? elastic and inelastic scattering from 18O have been measured at T(π)=164 MeV. Consistent with the results at 230 MeV, it is found that the ratio for the 21+ state is 1.86(16), while for the 31? state it is 0.89(6). These results are interpreted as indicating differences in neutron and proton deformations characterizing the 21+ transition and partial neutron blocking for the 31? transition. Optical model analysis of elastic scattering leads to the conclusion that . 相似文献
994.
995.
(±)-Isostegane isomerized into (+-)-isopicrostegane, (±)-picrostegane, and (±)-stegane, the parent compound o steganacin-type dibenzocyclooctadiene lignan lactones. 相似文献
996.
The distributed Bragg-reflector (DBR) laser with optical loss in the corrugated waveguide is analyzed by using the coupling mode theory. The threshold gain and the mode selectivity are given as a function of the optical loss, the coupling coefficient and the pumped length. These results show that the DBR laser has an optimum condition by considering the threshold gain and the mode selectivity. 相似文献
997.
Masao Shiozaki Yukiko Watanabe Toshio Kaneko Daisuke Tanaka Shin-ichi Kurakata 《Tetrahedron》2005,61(21):5101-5122
Lipid A analogues containing glucose in substitution for glucosamine on the reducing end were synthesized, and the inhibitory activities on LPS-induced TNFα production (LPS-antagonistic activity) in vitro using human whole blood cells were measured. The IC50 values (nM) of these ten compounds, 8, 14, 21, 31, 40, 51, 57, 62, 67 and 72, were 11.2, 15.4, 2.7, 0.1, 0.4, 1.3, 3.2, 3.2, 1.4 and 14.4, respectively. And also inhibitory activities (ID50) on TNFα production toward galactosamine loaded C3H/HeN mice in vivo of compounds 21, 31, 57, 62 and 67 were measured. The values of these compounds were 0.29, 0.50, 0.61, not dose-dependent and 0.33 mg/kg, respectively. 相似文献
998.
Gorelsky SI Basumallick L Vura-Weis J Sarangi R Hodgson KO Hedman B Fujisawa K Solomon EI 《Inorganic chemistry》2005,44(14):4947-4960
A series of metal-varied [ML(SC6F5)] model complexes (where L = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate and M = Mn, Fe, Co, Ni, Cu, and Zn) related to blue copper proteins has been studied by a combination of absorption, MCD, resonance Raman, and S K-edge X-ray absorption spectroscopies. Density functional calculations have been used to characterize these complexes and calculate their spectra. The observed variations in geometry, spectra, and bond energies are interpreted in terms of changes in the nature of metal-ligand bonding interactions. The metal 3d-ligand orbital interaction, which contributes to covalent bonding in these complexes, becomes stronger going from Mn(II) to Co(II) (the sigma contribution) and to Cu(II) (the pi contribution). This change in the covalency results from the increased effective nuclear charge of the metal atom in going from Mn(II) to Zn(II) and the change in the 3d orbital populations (d5-->d10). Ionic bonding also plays an important role in determining the overall strength of the ML(+)-SC6F5(-) interaction. However, there is a compensating effect: as the covalent contribution to the metal-ligand bonding increases, the ionic contribution decreases. These results provide insight into the Irving-Williams series, where it is found that the bonding of the ligand being replaced by the thiolate makes a major contribution to the observed order of the stability constants over the series of metal ions. 相似文献
999.
We demonstrated the deposition of nanometric Zn dots using photodissociation with gas-phase diethylzinc and an optical near field under nonresonant conditions. To explain the experimental results, we proposed an exciton-phonon polariton model, and discuss the quantitative experimental dependence of the deposition rate on the optical power and photon energy based on photodissociation involving multiple-step excitation via molecular vibration modes. The physical basis of this process, which seems to violate the Franck-Condon principle, is the optically nonadiabatic excitation of the molecular vibration mode due to the steep spatial gradient of the optical near-field energy. 相似文献
1000.
Two kinds of the homogeneous nucleation theory exist at the present: the classical nucleation theory and the semiphenomenological model. To test them, we performed molecular-dynamics (MD) simulations of nucleation from vapor to liquid with 5000-20,000 Lennard-Jones-type molecules. Simulations were done for various values of supersaturation ratios (from 2 to 10) and temperatures (from 80 to 120 K). We compared the size distribution of clusters in MD simulations with those in the theoretical models because the number density of critical clusters governs the nucleation rate. We found that the semiphenomenological model achieves excellent agreements in size distributions of the clusters with all MD simulations we done. The classical theory underestimates the number density of the clusters in the temperature range of 80-100 K, but overestimates in 100-120 K. The semiphenomenological model also predicts well the nucleation rate in MD simulations, while the classical nucleation theory does not. Our results confirmed the validity of the semiphenomenological model for Lennard-Jones-type molecules. 相似文献