全文获取类型
收费全文 | 14022篇 |
免费 | 2284篇 |
国内免费 | 1254篇 |
专业分类
化学 | 2802篇 |
晶体学 | 33篇 |
力学 | 839篇 |
综合类 | 63篇 |
数学 | 381篇 |
物理学 | 6521篇 |
无线电 | 6921篇 |
出版年
2024年 | 31篇 |
2023年 | 198篇 |
2022年 | 248篇 |
2021年 | 301篇 |
2020年 | 337篇 |
2019年 | 277篇 |
2018年 | 284篇 |
2017年 | 506篇 |
2016年 | 605篇 |
2015年 | 638篇 |
2014年 | 959篇 |
2013年 | 909篇 |
2012年 | 1093篇 |
2011年 | 1112篇 |
2010年 | 840篇 |
2009年 | 869篇 |
2008年 | 999篇 |
2007年 | 1056篇 |
2006年 | 906篇 |
2005年 | 733篇 |
2004年 | 668篇 |
2003年 | 607篇 |
2002年 | 475篇 |
2001年 | 507篇 |
2000年 | 398篇 |
1999年 | 318篇 |
1998年 | 270篇 |
1997年 | 260篇 |
1996年 | 217篇 |
1995年 | 168篇 |
1994年 | 135篇 |
1993年 | 130篇 |
1992年 | 103篇 |
1991年 | 88篇 |
1990年 | 56篇 |
1989年 | 50篇 |
1988年 | 47篇 |
1987年 | 33篇 |
1986年 | 15篇 |
1985年 | 30篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
DIELECTRIC EFFECT ON THE RADIO-FREQUENCY CHARACTERISTICS OF A RECTANGULAR WAVEGUIDE GRATING TRAVELING WAVE TUBE 总被引:2,自引:0,他引:2
Zhigang Lu Yubin Gong Yanyu Wei Wenxiang Wang 《International Journal of Infrared and Millimeter Waves》2006,27(8):1095-1108
A new type of partial-dielectric-loaded rectangular waveguide grating slow-wave structure (SWS) for millimeter wave traveling
wave tube (TWT) is presented in this paper. The radio-frequency characteristics including the dispersion properties, the longitudinal
electric field distribution and the beam-wave coupling impedance of this structure are analyzed. The results show that the
dispersion of the rectangular waveguide grating circuit is weakened, the phase velocity is reduced and the position of the
maximum E
z
is basically invariant after partially filling the dielectric materials in the rectangular waveguide grating SWS. Although
the coupling impedance decreases a little, it still keeps above 40 Ω. 相似文献
103.
《Electroanalysis》2006,18(6):613-620
The interaction of malachite green (MG) with double‐stranded DNA (dsDNA) in pH 7.0 Britton–Robinson (B–R) buffer solution was investigated by electrochemical and spectrophotometric methods. Within the potential scan range of ?1.0 to +1.5 V (vs. SCE), MG has two oxidative peaks at 0.547 V and 0.833 V and one reductive peak at 0.362 V on cyclic voltammogram at the scan rate of 0.20 V/s. After the addition of dsDNA into the MG solution, the oxidative peak current at 0.547 V decreases obviously. The electrochemical parameters, such as the charge transfer coefficient (α), the surface reaction rate constant (ks) and the diffusion coefficient (D), were calculated and compared between in the absence and presence of dsDNA. The results show that these parameters of MG after adding dsDNA have greatly changed, which indicates that an electrochemical active complex was formed. The interaction mechanisms of MG with dsDNA are discussed in some details from the electrochemistry and UV‐vis spectrophotometry. The reduction of the peak current of MG after adding dsDNA was further used for the quantification of dsDNA by differential pulse voltammetry (DPV). The linear range for dsDNA is in the range of 10.0–100.0 μg/mL with the linear regression equation as Δip (μA)=0.065+0.0096 C (μg/mL) and the detection limit of 6.0 μg/mL (3σ). The influences of coexisting substances were investigated and artificial samples were determined with satisfactory results. 相似文献
104.
105.
Vanessa de Freitas Cunha Lins Geraldo Francisco de Andrade Reis Carlos Roberto de Araujo 《Applied Surface Science》2006,253(5):2875-2884
In this work, electrochemical impedance spectroscopy and linear polarization are used in determining porosity of zinc phosphates, and of nickel and manganese modified zinc phosphates on electrogalvanized steel. The porosity of the phosphate layers ranges from 0.1% for the manganese-modified hopeite to 8% for hopeite, using the linear polarization and the electrochemical impedance spectroscopy techniques. The porosity values measured using the two techniques were in agreement. All impedance spectra of coated samples showed two steps, with two capacitive arcs and an inductive looping. 相似文献
106.
对交流电场下双巯基烷烃硫醇自组装分子膜的阻抗谱进行了研究.利用汞金属作为衬底,制备出双巯基烷烃硫醇自组装分子膜,并通过交流频谱仪对其进行频谱的扫描.明确了膜的作用范围为阻抗谱中频部分为了解释该阻抗谱,提出了一种串联的等效电路来进行了拟合,并与其他的模型进行比较.同时,观察到在损耗谱中损耗峰随硫醇碳链原子数的增加而向低频方向移动并得出双巯基硫醇(C6-C10)在交流电场下的激活能为23~39 meV. 相似文献
107.
108.
以角锥棱镜作为惯性元件,利用光学干涉原理,可以实现对运动物体的二维加速度测量。本文给出了二维加速度激光传感器的设计理论和测量原理。 相似文献
109.
在测量微安表内阻的众多方法中,替代法是最简单的方法。本文全面分析了影响测量结果不确定度的因素,求出了实验测量的最佳条件,计算了普通仪器组合下测量结果的相对不确定度。 相似文献
110.
In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the number of the fringe evolutions during the corrosion test of a carbon steel in blank seawater and seawater with different concentrations of a corrosion inhibitor. In other words, the anodic dissolution behaviors (corrosion) of the carbon steel were determined simultaneously by holographic interferometry, as an electromagnetic method, and by the electrochemical impedance (EI) spectroscopy, as an electronic method. So, the abrupt rate change of the number of the fringe evolutions during corrosion tests, EI spectroscopy, of the carbon steel is called electrochemical emission spectroscopy. The corrosion process of the steel samples was carried out in blank seawater and seawater with different concentrations, 5–20 ppm, of TROS C-70 corrosion inhibitor using the EI spectroscopy method, at room temperature. The electrochemical-emission spectra of the carbon steel in different solutions represent a detailed picture of the rate change of the anodic dissolution of the steel throughout the corrosion processes. Furthermore, the optical interferometry data of the carbon steel were compared to the data, which was obtained from the EI. spectroscopy. Consequently, holographic interferometry is found very useful for monitoring the anodic dissolution behaviors of metals, in which the number of the fringe evolutions of the steel samples can be determined in situ. 相似文献