全文获取类型
收费全文 | 136852篇 |
免费 | 19644篇 |
国内免费 | 15401篇 |
专业分类
化学 | 72843篇 |
晶体学 | 1143篇 |
力学 | 5918篇 |
综合类 | 669篇 |
数学 | 12645篇 |
物理学 | 39695篇 |
无线电 | 38984篇 |
出版年
2024年 | 551篇 |
2023年 | 3171篇 |
2022年 | 4205篇 |
2021年 | 5356篇 |
2020年 | 5221篇 |
2019年 | 4720篇 |
2018年 | 4444篇 |
2017年 | 4174篇 |
2016年 | 5914篇 |
2015年 | 6261篇 |
2014年 | 7684篇 |
2013年 | 9774篇 |
2012年 | 11458篇 |
2011年 | 11639篇 |
2010年 | 8615篇 |
2009年 | 8542篇 |
2008年 | 8808篇 |
2007年 | 7985篇 |
2006年 | 7577篇 |
2005年 | 6646篇 |
2004年 | 4839篇 |
2003年 | 4039篇 |
2002年 | 3641篇 |
2001年 | 3116篇 |
2000年 | 2817篇 |
1999年 | 2943篇 |
1998年 | 2509篇 |
1997年 | 2175篇 |
1996年 | 2150篇 |
1995年 | 1901篇 |
1994年 | 1616篇 |
1993年 | 1341篇 |
1992年 | 1178篇 |
1991年 | 995篇 |
1990年 | 828篇 |
1989年 | 591篇 |
1988年 | 462篇 |
1987年 | 378篇 |
1986年 | 384篇 |
1985年 | 293篇 |
1984年 | 221篇 |
1983年 | 191篇 |
1982年 | 141篇 |
1981年 | 84篇 |
1980年 | 65篇 |
1979年 | 27篇 |
1978年 | 28篇 |
1976年 | 24篇 |
1975年 | 23篇 |
1957年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
E. Liénard G. Ban J. Blieck D. Durand F. Duval X. Fléchard M. Herbane M. Labalme Y. Lemière F. Mauger A. Méry O. Naviliat-Cuncic D. Rodríguez J. C. Thomas 《Hyperfine Interactions》2006,172(1-3):29-33
We report on the status of the LPCTrap experiment, devoted to measure the β–ν angular correlation in the pure Gamow–Teller
decay of 6He. This measurement is motivated by the search for the presence of tensor type contributions to the weak interaction. The
6He ions are confined in a novel transparent Paul trap. The β particles and the recoil ions are detected in coincidence to
deduce the angular correlation parameter. The commissioning run performed in 2005 has given the proof of principle of this
experiment. Up to 105 coincidences were recorded during a second run in 2006. 相似文献
152.
153.
154.
155.
Based on solving the couple mode equation numerically, the characterization of the signal power on the gate power was analyzed. And the relationship of the tolerance of the grating period and the bulk temperature on the interaction length was analyzed. 相似文献
156.
A new chemiluminescence method for the determination of carbamazepine (CBZ) has been developed. The method is based on the chemiluminescence produced in the reaction of tris(2,2'-bipyridine)ruthenium(III) and CBZ in an acidic medium. The chemiluminescence intensity was enhanced by organic solvents in the reaction system. Under the optimum experimental conditions, the calibration curve was linear over the range 4.0 x 10(-3)-8.6 x 10(-7) mol/L for CBZ. The detection limit (S/N = 3) was 2.5 x 10(-7) mol/L and the relative standard deviation of six replicate measurements was 2.6% for 4.0 x 10(-4) mol/L of CBZ. The possible reaction mechanism were also discussed. The chemiluminescence method was successfully applied to assay the CBZ contents in pharmaceutical tablets. 相似文献
157.
本文研究了无线局域网中使信号频谱得到优化的一种简单OFDM子载波加载算法。此算法基于边缘自适应(Margin Adaptive)加载准则及其在室内无线信道上的性能。 相似文献
158.
The effects of partial substitution of Mn for Co on the thermoelectric properties of Ca3MnxCo4−xO9 (x=0, 0.03, 0.9), prepared by sol-gel process, were investigated at the temperatures from 380 K down to 5 K. The results indicate that the substitution of Mn for Co results in increase in thermopower at temperatures >∼80 K, and substantial (23-31% at 300 K) decrease in lattice thermal conductivity in the whole temperature range investigated. The temperature behavior of ZT suggests that Ca3MnxCo4−xO9 with light Mn substitution would be a promising candidate for high-temperature thermoelectric applications. 相似文献
159.
Spontaneous emission behavior from atoms (or molecules) in one-dimensional photonic crystal with a defect is investigated. Taken all the TE and TM modes into account, the normalized spontaneous emission rate of the atom is calculated as a function of the position of the atom in the crystal. Results for both nonabsorbing dielectric structure and absorbing dielectric structure are presented. With the increase of the thickness of the defect in which the atoms are embedded, the oscillations of the spontaneous emission rate versus the position of the atom become dense and the lifetime distribution becomes narrow and sharp. The PC effect may lead to the coexistence of both accelerated and inhibited decay processes. 相似文献
160.
Huimin Xie Biao Li Robert Geer Bai Xu James Castracane 《Optics and Lasers in Engineering》2003,40(3):163-177
A focused ion beam (FIB) Moiré method is proposed to measure the in-plane deformation of object in a micrometer scale. The FIB Moiré is generated by the interference between a prepared specimen grating and FIB raster scan lines. The principle of the FIB Moiré is described. The sensitivity and accuracy of deformation measurement are discussed in detail. Several specimen gratings with 0.14 and 0.20 μm spacing are used to generate FIB Moiré patterns. The FIB Moiré method is successfully used to measure the residual deformation in a micro-electro-mechanical system structure after removing the SiO2 sacrificial layer with a 5000 lines/mm grating. The results demonstrate the feasibility of this method. 相似文献