全文获取类型
收费全文 | 31257篇 |
免费 | 2295篇 |
国内免费 | 1121篇 |
专业分类
电工技术 | 1748篇 |
综合类 | 1066篇 |
化学工业 | 7708篇 |
金属工艺 | 1022篇 |
机械仪表 | 1459篇 |
建筑科学 | 495篇 |
矿业工程 | 249篇 |
能源动力 | 7995篇 |
轻工业 | 3762篇 |
水利工程 | 78篇 |
石油天然气 | 162篇 |
武器工业 | 58篇 |
无线电 | 3037篇 |
一般工业技术 | 3124篇 |
冶金工业 | 789篇 |
原子能技术 | 340篇 |
自动化技术 | 1581篇 |
出版年
2024年 | 92篇 |
2023年 | 710篇 |
2022年 | 2000篇 |
2021年 | 2297篇 |
2020年 | 1290篇 |
2019年 | 1192篇 |
2018年 | 986篇 |
2017年 | 1158篇 |
2016年 | 1059篇 |
2015年 | 1030篇 |
2014年 | 1728篇 |
2013年 | 1911篇 |
2012年 | 1913篇 |
2011年 | 2690篇 |
2010年 | 1968篇 |
2009年 | 1684篇 |
2008年 | 1733篇 |
2007年 | 1653篇 |
2006年 | 1335篇 |
2005年 | 1112篇 |
2004年 | 879篇 |
2003年 | 666篇 |
2002年 | 651篇 |
2001年 | 511篇 |
2000年 | 395篇 |
1999年 | 328篇 |
1998年 | 291篇 |
1997年 | 237篇 |
1996年 | 193篇 |
1995年 | 161篇 |
1994年 | 151篇 |
1993年 | 118篇 |
1992年 | 100篇 |
1991年 | 78篇 |
1990年 | 64篇 |
1989年 | 56篇 |
1988年 | 44篇 |
1987年 | 28篇 |
1986年 | 30篇 |
1985年 | 34篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1975年 | 4篇 |
1965年 | 3篇 |
1964年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
A new method of studying the corrosion inhibition mechanism of rare earth metal(REM) on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were analyzed. By measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and the addition of CeCl3, the influence of corrosive performance of CeCl3 on LC4 super-power aluminum alloy in the 0.1 mol·L−1 NaCl solution was investigated. Meanwhile, the conditional changes of pH values, CeCl3 solution, additire and time of performance were also studied. Finally, the features of electrode surface were revealed by using SEM and X-ray energy-dispersive spectrometry (EDS). By combining these with other electric chemical techniques, such as potential-time curve, polarization curve et al. 相似文献
22.
23.
24.
Nanocrystalline TiO2 photosensitized with natural polymers with enhanced efficiency from 400 to 600 nm 总被引:1,自引:0,他引:1
Rodolfo Espinosa Inti Zumeta Jorge L. Santana Francisco Martínez-Luzardo Bernardo Gonzlez Sergilus Docteur Elena Vigil 《Solar Energy Materials & Solar Cells》2005,85(3):359-369
TiO2 sensitization for solar applications requires not only efficient but also stable and inexpensive sensitizers. Different condensed tannins extracted from bark wastes of tropical wood trees were studied as possible sensitizers of TiO2. These natural polymers adhere strongly to the TiO2 even from aqueous solutions. Absorption spectra are presented for 1 mM aqueous sensitizing solutions prepared with lyophilized condensed tannins which absorb light in the visible range. Spectral photocurrent measurements and I–V characterization show that no bias is required for electron injection to the TiO2 from all studied condensed tannins. Incident photon to current efficiency (IPCE) analysis indicates that surface complexation originates absorption bands with different electron injection efficiencies. These play a dominant role in determining IPCE spectral shape. We propose that surface modification by the sensitizer changes the surface trap density, thereby decreasing recombination losses. 相似文献
25.
The effects of NOx on the performance of proton exchange membrane (PEM) fuel cell were investigated through the introduction of a mixture containing NO and NO2, in a ratio of 9:1, into the cathode stream of a single PEM fuel cell. The NOx concentrations used in the experiments were 1480 ppm, 140 ppm and 10 ppm, which cover a range of three orders. The experimental results obtained from the tests of durability, polarization, reversibility and electrochemical impedance spectroscopy (EIS) showed a detrimental effect of NOx on the cell performance. The electrochemical measurements results suggested that the impacts of NOx are mainly resulted from the superposition of the oxygen reduction reaction (ORR), NO and HNO2 oxidation reactions, and the increased cathodic impedance. Complete recovery of the cell performance was reached after operating the cell with clean air and then purging with N2 for hours. 相似文献
26.
Local Strain Measurement within Tendon 总被引:2,自引:0,他引:2
Abstract: Tendon is a dense connective tissue, responsible for transmitting the forces generated by muscles to the skeleton. It is composed of a hierarchical arrangement of crimped collagen fibres, interspersed with proteoglycan matrix and cells, known as tenocytes. During physiological loading, tendons are subjected to strains in the region of 5–6%, which result in the straightening and realignment of the collagen fibres, generating variable local strain fields within the tendon. This study demonstrates a technique for analysing local strains within viable tendon explants, during both loading and unloading of the tissue. Samples were strained in a custom-designed rig, allowing real-time visualisation of cell nuclei, used as local discrete markers, on a confocal microscope. Results indicated that local strains within the fascicle are smaller than the applied strains, never exceeding 1.2%, even at 8% gross applied strain. By contrast, the sliding of adjacent collagen units was recorded at each strain increment in this study, reaching a mean maximum of 3.9% of the applied displacement. Loading–unloading studies indicated that sliding behaviour is reversible up to strains of 5%, and provides the major extension mechanism within the rat-tail tendon. This technique can be extended to further analyse shearing behaviour within the matrix. 相似文献
27.
Henrik Pettersson Tadeusz Gruszecki Lars-Henrik Johansson Per Johander 《Solar Energy Materials & Solar Cells》2003,77(4):6595
A manufacturing technique for monolithic dye-sensitised solar cells is presented. Encapsulated modules designed for indoor low-power applications have been prepared using industrial methods and equipment. Under certain conditions (light intensity <5000 lx, temperature between –10°C and 50°C, and relative humidity of appr. 50%), the modules have performed well and shown excellent long-term stability. Moreover, modules withstand illumination in combination with storage at 100% relative humidity. However, a certain degradation of the module performance takes place at illuminations exceeding 5000 lx and temperatures exceeding 50°C. 相似文献
28.
ATM网络的可用比特率业务 总被引:2,自引:0,他引:2
本文介绍了可用比特率业务的业务特点,速率控制机制以及该业务存在的问题。 相似文献
29.
The dye-sensitized TiO2 complex films were prepared by the dye coat onto TiO2 surfaces,and the sensitizing mechanism and adsorption properties of the dye-sensitized TiO2 complex films were inverstigated.The influence of the application conditions of dye adsorbed on TiO2 films on the amount of dye adsorption was discussed.Experimental results show that the concentration,the temperature of dye solutions and the dipping time of TiO2 films in the dye solutions have a significant influence on the amount of dye adsorption.Cell test indicates that the conversion efficiency of light to electricity increases with the amount of dye adsorption. 相似文献
30.
河口水流、波浪、潮流、泥沙、河床变形二维数学模型 总被引:19,自引:0,他引:19
根据河口“波浪掀沙,潮流输沙”的泥沙运动机制,引入“波浪幅射应力”反应波浪对水体和泥沙的驱动力.考虑波浪对底部泥沙作用力、波浪对水流挟沙能力的影响及风场对水流和泥沙运动的影响.同时考虑泥沙粒径大小、水体含盐度、含沙量及水流紊动程度等因素对絮凝沉速的影响.用ADI算法求解沿水深平均方程,破开算子法解悬移质不平衡输沙方程及河床变形方程,引入通度概念处理岸滩不规则边界,建立河口水流、波浪、潮流、泥沙、河床变形二维数学模型.通过实测资料及卫星摇感图像对所建数学模型进行检验,表明它可以较好地预测河口泥沙的运动 相似文献