全文获取类型
收费全文 | 31621篇 |
免费 | 5628篇 |
国内免费 | 3344篇 |
专业分类
化学 | 22467篇 |
晶体学 | 357篇 |
力学 | 1814篇 |
综合类 | 139篇 |
数学 | 3038篇 |
物理学 | 12778篇 |
出版年
2024年 | 136篇 |
2023年 | 705篇 |
2022年 | 1237篇 |
2021年 | 1389篇 |
2020年 | 1428篇 |
2019年 | 1398篇 |
2018年 | 1180篇 |
2017年 | 1071篇 |
2016年 | 1629篇 |
2015年 | 1552篇 |
2014年 | 1982篇 |
2013年 | 2438篇 |
2012年 | 2917篇 |
2011年 | 2938篇 |
2010年 | 1906篇 |
2009年 | 1812篇 |
2008年 | 2027篇 |
2007年 | 1775篇 |
2006年 | 1652篇 |
2005年 | 1312篇 |
2004年 | 990篇 |
2003年 | 767篇 |
2002年 | 763篇 |
2001年 | 591篇 |
2000年 | 471篇 |
1999年 | 595篇 |
1998年 | 514篇 |
1997年 | 500篇 |
1996年 | 502篇 |
1995年 | 427篇 |
1994年 | 344篇 |
1993年 | 286篇 |
1992年 | 279篇 |
1991年 | 224篇 |
1990年 | 204篇 |
1989年 | 153篇 |
1988年 | 92篇 |
1987年 | 80篇 |
1986年 | 105篇 |
1985年 | 73篇 |
1984年 | 37篇 |
1983年 | 44篇 |
1982年 | 28篇 |
1981年 | 22篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1957年 | 4篇 |
1923年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
141.
Jia Li Yanru Chen Shixue Xu Yongqing Wang Muchun Zhou Qi Zhao Yu Xin Feinan Chen 《Optics & Laser Technology》2011,43(1):152-157
Based on the vector angular spectrum representation of electromagnetic beams and the method of stationary phase, the vectorial structure of a Hermite-cosine-Gaussian (HcosG) beam in the far field is derived in analytical form. Energy flux distributions for the TE term, TM term and the whole beam are represented. The vectorial structures of HcosG beams with different Hermite models are depicted. The effects of cosine displacement parameters on the vectorial structure are also demonstrated. The results may provide a flexible approach to manipulate HcosG beams in free space. 相似文献
142.
Songqing Zhao Yuzi Liu Shufang Wang Zhen Liu Ze Zhang Huibin Lu Bolin Cheng 《Applied Surface Science》2006,253(2):726-729
B-doped ZnO thin films have been fabricated on fused quartz substrates using boron-ZnO mosaic target by pulsed-laser deposition technique, and the mechanical properties have been studied by nanoindentation continuous stiffness measurement technique and transmission electron microscope (TEM). Nanoindentation measurement revealed that the hardness of B-doped ZnO films, 9.32 ± 0.90 to 12.10 ± 1.00 GPa, is much greater than that of undoped ZnO films and very close to that of traditional semiconductor Si. The mean transmittance (%) is larger than 81% in the visible range (380-780 nm) for all the films, and the Hall effect measurement showed that the carrier density is around 2 × 1020 cm−3 and the resistivity lower than 3 × 10−3 Ω cm. TEM characteristics show undoped thin films have more amorphous area between grains while the B-doped ZnO films have thin grain boundaries. We suggest that the grain boundaries act as the strain compensation sites and the decrease in thickness of grain boundaries enhances the hardness of the B-doped ZnO films. 相似文献
143.
Prior to the flashover across an insulator in vacuum, the insulator surface is usually charged. It is of great importance to investigate the charging phenomena for better understanding the flashover characteristics. It is considered that there are two kinds of mechanisms closely related to the surface charging of insulator i.e., the secondary electron emission occurred over an insulator, and while employing a perfect electrode contact ahead of electron emission into vacuum, the charge injection and accumulation occurred inside the surface layer of an insulator. Based on the rigorous analysis of the kinetic processes of both primary and secondary electrons, the related surface charges were theoretically deduced. Involving the detrapping of charges trapped and the recombination of charges injected, the charging process due to charge injection and accumulation was analyzed. Some formulas were given to express the density of surface charges. 相似文献
144.
145.
Jin-Cui Zhao Ping Yuan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(6):1-6
We investigate self-localisation of dipolar Bose-Einstein condensates (BECs) in 1D nonlinear lattices via boundary dissipation in a dissipative nonlinear Schrödinger model (DNLS) with nearest-neighbour dipole-dipole interactions (DDI). By including both contact interactions and DDIs, we observe that a rich variety of self-localised modes (i.e., single discrete breathers, moving breathers and multi-breathers) can exist in dipolar systems in optical lattices. Furthermore, we find that DDIs can suppress the formation of single discrete breathers and support the formation of multi-breathers. Our results show that including both contact interactions and DDIs may provide a way to experimentally obtain stationary multi-breathers in optical lattices via boundary dissipations. 相似文献
146.
XiGuang Cao Xun Chen YunHua Chen XiangYi Cui DeQing Fang ChangBo Fu Karl L. Giboni HaoWei Gong GuoDong Guo Ming He Jie Hu XingTao Huang XiangDong Ji YongLin Ju ShaoLi Li Qing Lin HuaXuan Liu JiangLai Liu Xiang Liu Wolfgang Lorenzon YuGang Ma YaJun Mao KaiXuan Ni Kirill Pushkin XiangXiang Ren Michael Schubnell ManBing Shen YuJie Shi Scott Stephenson AnDi Tan Greg Tarlé HongWei Wang JiMing Wang Meng Wang XuMing Wang Zhou Wang YueHuan Wei ShiYong Wu MengJiao Xiao Xiang Xiao PengWei Xie Tao Ye YingHui You XiongHui Zen Hua Zhang Tao Zhang HaiYing Zhao Li Zhao XiaoPeng Zhou ZhongHua Zhu 《中国科学:物理学 力学 天文学(英文版)》2014,57(8):1476-1494
147.
148.
149.
The nitrogen doping of ZnO film deposited by the magnetron sputtering method is subsequently realized by the hydrothermal synthesis method.The nitrogen-doped ZnO film is preferably(002) oriented.With the increase of hexamethylenetetramine(HMT) solution concentration,the average grain size of the film along the 002 direction almost immediately decreases and then monotonously increases,conversely,the lattice strain first increases and then decreases.The structural evolution of the film surface from compact and even to sparse and rough is attributed to the enhanced nitrogen doping content in the hydrothermal process.The transmission and photoluminescence properties of the film are closely related to grain size,lattice strain,and nitrogen-related defect arising from the enhanced nitrogen doping content with HMT concentration increasing. 相似文献
150.
Bobo Hua Xiu-Hong Gao Ming-Jing Zhao Shao-Ming Fei 《International Journal of Theoretical Physics》2013,52(9):3007-3010
We study the stability of NPT property of an arbitrary pure entangled state under the mixture of arbitrary pure separable states. For bipartite pure states with Schmidt number n (n>1) which is NPT, we show that this state is still NPT when it is mixed with no more than $\frac {n(n-1)}{2}-1$ arbitrary pure separable states. This result is generalized to multipartite case. 相似文献