全文获取类型
收费全文 | 106076篇 |
免费 | 17492篇 |
国内免费 | 10106篇 |
专业分类
化学 | 71313篇 |
晶体学 | 1218篇 |
力学 | 6923篇 |
综合类 | 536篇 |
数学 | 11924篇 |
物理学 | 41760篇 |
出版年
2024年 | 370篇 |
2023年 | 2133篇 |
2022年 | 3645篇 |
2021年 | 3975篇 |
2020年 | 4251篇 |
2019年 | 4137篇 |
2018年 | 3553篇 |
2017年 | 3289篇 |
2016年 | 5184篇 |
2015年 | 4948篇 |
2014年 | 6025篇 |
2013年 | 7786篇 |
2012年 | 9429篇 |
2011年 | 9759篇 |
2010年 | 6442篇 |
2009年 | 6159篇 |
2008年 | 6534篇 |
2007年 | 5997篇 |
2006年 | 5477篇 |
2005年 | 4594篇 |
2004年 | 3401篇 |
2003年 | 2668篇 |
2002年 | 2416篇 |
2001年 | 1979篇 |
2000年 | 1763篇 |
1999年 | 2072篇 |
1998年 | 1847篇 |
1997年 | 1720篇 |
1996年 | 1889篇 |
1995年 | 1502篇 |
1994年 | 1461篇 |
1993年 | 1168篇 |
1992年 | 1069篇 |
1991年 | 985篇 |
1990年 | 792篇 |
1989年 | 563篇 |
1988年 | 465篇 |
1987年 | 382篇 |
1986年 | 374篇 |
1985年 | 318篇 |
1984年 | 241篇 |
1983年 | 154篇 |
1982年 | 142篇 |
1981年 | 106篇 |
1980年 | 76篇 |
1979年 | 44篇 |
1978年 | 34篇 |
1976年 | 36篇 |
1975年 | 33篇 |
1974年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
We consider concentrated vorticities for the Euler equation on a smooth domain in the form of supported on well-separated vortical domains , , of small diameters . A conformal mapping framework is set up to study this free boundary problem with being part of unknowns. For any given vorticities and small , through a perturbation approach, we obtain such piecewise constant steady vortex patches as well as piecewise smooth Lipschitz steady vorticities, both concentrated near non-degenerate critical configurations of the Kirchhoff–Routh Hamiltonian function. When vortex patch evolution is considered as the boundary dynamics of , through an invariant subspace decomposition, it is also proved that the spectral/linear stability of such steady vortex patches is largely determined by that of the 2N-dimensional linearized point vortex dynamics, while the motion is highly oscillatory in the 2N-codim directions corresponding to the vortical domain shapes. 相似文献
2.
3.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling. 相似文献
4.
Qin Yin Shou-Guo Wang Xiao-Wei Liang De-Wei Gao Jun Zheng Shu-Li You 《Chemical science》2015,6(7):4179-4183
An organocatalytic asymmetric chlorinative dearomatization of naphthols was realized for the first time, providing chiral naphthalenones with a Cl-containing all-substituted stereocenter in excellent yields and enantioselectivity (up to 97% yield and 96% ee). The reaction features mild reaction conditions, good tolerance of diverse functional groups and simple reaction operation. 相似文献
5.
6.
Lijuan Shen Li Li Sheng Lu Xiaohan Zhang Jie Liu Junlin An Guojun Zhang Bo Wu Fei Wang 《中国颗粒学报》2015,(3):10-15
We conducted measurements of black carbon(BC) aerosol in Jiaxing,China during autumn from September 26 to November 30,2013.We investigated temporal and diurnal variations of BC,and its correlations with meteorological parameters and other major pollutants.Results showed that hourly mass concentrations of BC ranged from 0.2 to 22.0 μg/m3,with an average of 5.1 μg/m3.The diurnai variation of BC exhibited a bimodal distribution,with peaks at 07:00 and 18:00.The morning peak was larger than the evening peak.The mass percentages of BC in PM2.5 and PM10 were 7.1%and 4.8%,respectively.The absorption coefficient of BC was calculated to be 44.4 Mm-1,which accounted for 11.1%of the total aerosol extinction.BC was mainly emitted from local sources in southwestern Jiaxing where BC concentrations were generally greater than 11 μg/m3 during the measurement period.Correlation analysis indicated that the main sources of BC were motor vehicle exhaust,and domestic and industrial combustion. 相似文献
7.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献
8.
9.
10.