全文获取类型
收费全文 | 4136篇 |
免费 | 89篇 |
国内免费 | 20篇 |
专业分类
化学 | 2802篇 |
晶体学 | 52篇 |
力学 | 62篇 |
数学 | 241篇 |
物理学 | 1088篇 |
出版年
2022年 | 26篇 |
2021年 | 25篇 |
2020年 | 45篇 |
2019年 | 52篇 |
2018年 | 37篇 |
2017年 | 33篇 |
2016年 | 53篇 |
2015年 | 71篇 |
2014年 | 73篇 |
2013年 | 227篇 |
2012年 | 183篇 |
2011年 | 225篇 |
2010年 | 126篇 |
2009年 | 141篇 |
2008年 | 220篇 |
2007年 | 241篇 |
2006年 | 235篇 |
2005年 | 205篇 |
2004年 | 146篇 |
2003年 | 158篇 |
2002年 | 170篇 |
2001年 | 101篇 |
2000年 | 111篇 |
1999年 | 72篇 |
1998年 | 47篇 |
1997年 | 48篇 |
1996年 | 71篇 |
1995年 | 46篇 |
1994年 | 38篇 |
1993年 | 47篇 |
1992年 | 70篇 |
1991年 | 48篇 |
1990年 | 48篇 |
1989年 | 43篇 |
1988年 | 62篇 |
1987年 | 45篇 |
1986年 | 52篇 |
1985年 | 65篇 |
1984年 | 63篇 |
1983年 | 29篇 |
1982年 | 44篇 |
1981年 | 39篇 |
1980年 | 42篇 |
1979年 | 43篇 |
1978年 | 38篇 |
1977年 | 45篇 |
1976年 | 25篇 |
1975年 | 31篇 |
1974年 | 31篇 |
1973年 | 25篇 |
排序方式: 共有4245条查询结果,搜索用时 15 毫秒
1.
J. Kobayashi Y. Izumi M. Kumakura Y. Takahashi 《Applied physics. B, Lasers and optics》2006,83(1):21-25
By stabilizing the beam pointing of optical trapping beams, we have succeeded in stable formation of Bose–Einstein condensate
(BEC) of 87Rb with all-optical method. The thermal effect of acousto-optic modulator (AOM) is usually one of the most serious problems
to induce beam-pointing instability, especially for high power CO2 laser. By passing the beam through AOM twice, we have improved the beam pointing from about 4.8 mrad to less than 0.4 mrad,
which has been experimentally confirmed to be small enough to stably form BEC at the crossed region of CO2 lasers as well as to perform experiments using an optical lattice which might have been affected by beam-pointing instability.
PACS 32.80.Pj; 42.79.Jq; 03.75.Mn 相似文献
2.
3.
Yasumitsu Matsuo Takehiko Ijichi Hironori Yamada Junko Hatori Seiichiro Ikehata 《Central European Journal of Physics》2004,2(2):357-366
We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator and molecular conductor, and
investigated the electrical properties and memory effects on the PEN-FET. We have observed a drastic change in the drain current
at around the coercive electric fieldE
c
of the organic ferroelectric insulator in not only a FET (PEN-FET) based on a pentacene (PEN) film but also a FET (IPEN-FET)
based on an iodine doped PEN film. The magnitude of the change of the drain current for the IPEN-FET is 200 times larger than
that for the PEN-FET. It is expected from these results that the PEN-FET (especially the IPEN-FET) is an improvement in such
devices, since it operates at a low gate electric field accompanied by the appearance of the spontaneous polarization in the
organic ferroelectric insulator. In addition, we have found that the drain current for the PEN-FET does not return to the
initial drain current ofE
G
=0 V/cm for more than one week, even if the gate electric field is changed to 0 V/cm from 500 V/cm(>E
c
). From these results, it is suggested that the PEN-FET becomes a memory device. 相似文献
4.
A simple method to label oligosaccharides with a multifunctional fluorescent group was developed. Oligosaccharides were quantitatively labeled at their reducing termini with pyrene butanoic acid hydrazide. The pyrene-labeled oligosaccharides were successfully applied to fluorescence polarization measurements and ELISA at picomole quantity, which was not previously reached by other procedures. This labeling method should prove to be useful in a variety of aspects in glycobiology. 相似文献
5.
6.
7.
Hiroshi Yamauchi Keiko Takahashi Mari Mashiko Juichiro Saitoh Yukio Yamamura 《应用有机金属化学》1992,6(4):383-388
We calculated the intake of each chemical species of dietary arsenic by typical Japanese, and determined urinary and blood levels of each chemical species of arsenic. The mean total arsenic intake by 35 volunteers was 195±235 (15.8-1039) μg As day?1, composed of 76% trimethylated arsenic (TMA), 17.3% inorganic arsenic (Asi), 5.8% dimethylated arsenic (DMA), and 0.8% monomethylated arsenic (MA): the intake of TMA was the largest of all the measured species. Intake of Asi characteristically and invariably occurred in each meal. Of the intake of Asi, 45-75% was methylated in vivo to form MA and DMA, and excreted in these forms into urine. The mean measured urinary total arsenic level in 56 healthy volunteers was 129±92.0 μg As dm?3, composed of 64.6% TMA, 26.7% DMA, 6.7% Asi and 2.2% MA. The mean blood total arsenic level in the 56 volunteers was 0.73±0.57 μg dl?1, composed of 73% TMA, 14% DMA and 9.6% Asi. The urinary TMA levels proved to be significantly correlated with the whole-blood TMA levels (r = 0.376; P<0.01). 相似文献
8.
The present paper gives a more complete treatment of the scattering from a two-dimensional random surface than previous works. Reciprocal theorems for the stochastic wave field and the incoherent scattering distribution (bistatic cross section) are derived and the presence of backscattering enhancement in the case of a slightly random Neumann surface is demonstrated. A physical interpretation of the backscattering enhancement associated with the presence of anomalous scattering on a slightly random Neumann surface is given. Some numerical calculations are performed to show the incoherent scattering distribution and the backscattering enhancement. 相似文献
9.
10.