全文获取类型
收费全文 | 5234篇 |
免费 | 583篇 |
国内免费 | 162篇 |
专业分类
电工技术 | 332篇 |
技术理论 | 1篇 |
综合类 | 403篇 |
化学工业 | 736篇 |
金属工艺 | 225篇 |
机械仪表 | 234篇 |
建筑科学 | 652篇 |
矿业工程 | 291篇 |
能源动力 | 279篇 |
轻工业 | 474篇 |
水利工程 | 252篇 |
石油天然气 | 297篇 |
武器工业 | 23篇 |
无线电 | 509篇 |
一般工业技术 | 738篇 |
冶金工业 | 146篇 |
原子能技术 | 51篇 |
自动化技术 | 336篇 |
出版年
2024年 | 19篇 |
2023年 | 117篇 |
2022年 | 96篇 |
2021年 | 151篇 |
2020年 | 188篇 |
2019年 | 172篇 |
2018年 | 128篇 |
2017年 | 164篇 |
2016年 | 177篇 |
2015年 | 205篇 |
2014年 | 318篇 |
2013年 | 334篇 |
2012年 | 339篇 |
2011年 | 365篇 |
2010年 | 284篇 |
2009年 | 292篇 |
2008年 | 266篇 |
2007年 | 368篇 |
2006年 | 293篇 |
2005年 | 240篇 |
2004年 | 226篇 |
2003年 | 215篇 |
2002年 | 164篇 |
2001年 | 122篇 |
2000年 | 135篇 |
1999年 | 118篇 |
1998年 | 79篇 |
1997年 | 72篇 |
1996年 | 52篇 |
1995年 | 43篇 |
1994年 | 41篇 |
1993年 | 36篇 |
1992年 | 30篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1975年 | 1篇 |
1962年 | 2篇 |
1957年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有5979条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(45):19758-19771
In this study, the effects of cell temperature and relative humidity on charge transport parameters are numerically analyzed. In order to perform this analysis, three-dimensional and anisotropic numerical models are developed. The numerical models are integrated into the experimental values for anisotropic electrical conductivities, as depending on cell temperature and relative humidity, that were obtained from our previous study. The achieved results indicate that the values of current densities in the in-plane direction increase with increasing cell temperature and relative humidity, while the current densities reach a maximum in the rib regions for both the numerical model at the through-plane direction. The behaviors of electrolyte potentials are similar with changes in the cell temperature and relative humidity. In addition, the cathode electrical potentials in both the in-plane direction and through-plane direction do not change to a considerable amount with increasing cell temperature and relative humidity. 相似文献
2.
龙口水利枢纽坝基岩体主要由奥陶系中统马家沟组(O2m2)灰岩组成,其中发育有多层软弱夹层。作为其中之一的钙质充填夹层,强度虽不很低,但由于处于坝基下的持力层内,间距不大,发育密集,产状平缓,是坝基浅层抗滑稳定的主要控制因素,因此,在大坝抗滑稳定分析时,应进行分析和研究。 相似文献
3.
本文报道采用液相外延(LPE)生长和传统光刻制管工艺研制出引入多层(三层或三层以上)中间能带隙过渡的吸收区、倍增区分离的InGaAs(P)/InP雪崩光电二极管(简称InGaAs(P)/InPSAGMAPD),其技术指标为:击穿电压VB=40~90V;0.9VB时的暗电流Id最小可小于10nA;1.3μm时光响应度Re=0.6~0.8A/W,倍增因子M≥20(Mmax>40),过剩噪声因子F≌5和较宽频带响应特性。 相似文献
4.
依托伊朗德黑兰地铁一、二号线工程 ,针对地铁单洞单线采用的轨道施工轨排法存在的不足 ,根据单洞双线隧道的特点 ,提出了利用组装好的轨排直接铺设在隧道结构底板上作为轨道平板车临时轨道的施工新方法 相似文献
5.
一级开发大柳树高坝原始库容比二级开发小观音高坝多 4 0亿m3 ,库容大带来的好处体现在 5~ 7月可多向下游增供水量 ,缓解下游河道断流 ;延长泄放清水时间 ;增加发电效益 ;满足宁蒙河段防凌要求 ;增加汛期集中泄水 ,减缓下游河道淤积萎缩 ;满足南水北调西线工程水量调节要求等。为了更好优化配置黄河水资源 ,从全局和长远利益考虑 ,应采用一级开发方案 ,修建大柳树高坝大库 相似文献
6.
用化学气相沉积法制备了液晶光阀中光电导层———非晶硅薄膜,从实验中得出最佳制备工艺的参数取值。给出了用包络线法测量非晶硅薄膜光吸收系数的原理,测量了样品的光吸收系数随波长的变化规律。得到样品在最佳工艺条件下的光吸收系数高于1×103cm-1。 相似文献
7.
Thin hard coatings fracture propagation during the impact test 总被引:2,自引:0,他引:2
One of the most significant applications of the impact test is to investigate thin hard coatings fatigue properties. Herein the test conditions and duration up to the film damage initiation, are considered in order to determine the critical stresses associated with the coating fatigue strength. Moreover, the subsequent film damage propagation is a significant mechanism as well, since it refers to the ability of the coating to withstand loads after its fatigue damage initiation. In order to describe the film fracture propagation the failed area ratio was introduced and an algorithm to determine this magnitude developed, based on the analysis of imprint scanning electron microscopy graphs. The application of the coating failed area ratio will be demonstrated in various impact test film cases, also with superficial thin layers. The top layers do not affect, in general, the failure initiation of the basic coating. However, according to the obtained results, the superficial films influence the basic coating failure propagation rate during the impact test. 相似文献
8.
D. Knig S. Carvajal-Gonzalez A. M. Downs J. Vassy P. Rigaut 《Journal of microscopy》1991,161(3):405-433
Within the concept of point processes, a review is presented of quantities which can be used in studies of three-dimensional (3-D) aggregates of particles. Suitable characteristics and estimators are given for both unmarked and marked point processes. To demonstrate the feasibility of such quantitative approaches, an application in histology, dealing with 3-D arrangements of cell nuclei in rat liver, is described. Using a confocal scanning light microscope, 3-D images are recorded and image analysis used to obtain the coordinates of the centroid, together with the volume and DNA content, of each cell nucleus. Examples of results are given, using both unmarked and marked point processes. In the latter case, cell type, nuclear volume and ploidy group are suitable marks. 相似文献
9.
Ashok K. Vijh 《Drying Technology》1995,13(1):215-224
An attempt is made to elucidate the electrochemical aspects of the electroosmotic dewatering (EOD) of clays as reported in some recent work, especially that on interrupted DC power electroosmotic dewatering published by Rabie, Mujumdar and Weber (2). These authors showed that the dewatering by EOD stops after the DC power has been on for several minutes or hours; on interruption of their power and on short-circuiting of the electrodes, conditions can be created again for some further dewatering by DC power EOD. This discovery, of Rabie et al. is interpreted as a fuel cell effect and it is shown that it affords clues to several other electrochemical strategies for the possible enhancement of the efficiency of the EOD by DC power.
Further, the open circuit potentials observed by Rabie et al. (2) on the interruption of DC power are given an electrochemical interpretation which leads to quantitative estimates in agreement with the experimental values. 相似文献
Further, the open circuit potentials observed by Rabie et al. (2) on the interruption of DC power are given an electrochemical interpretation which leads to quantitative estimates in agreement with the experimental values. 相似文献
10.
Theory of a novel voltage-sustaining layer for power devices 总被引:3,自引:0,他引:3
The theory of a novel voltage-sustaining layer for power devices, called a Composite Buffer layer (CB-layer for short) is proposed. The CB-layer can be implemented in several ways, one particular implementation is used here, which consists of alternating n- and p-type regions, that are parallel to the direction of the applied electric field. In the off-state, the fields induced by the depletion charges of both region types compensate each other to allowing the doping in both n-regions and p-regions to be very high without causing a reduction of the breakdown voltage. In the onstate the heavy doping ensures the voltage drop is very low and that the saturation current density high. A simple relationship between the specific on-resistance and Ron and the sustaining voltage VB can be shown to be Ron=2.53 × 10−7bVB1.23 ωcm2, where the breadth b (in μm) of each region is much smaller than the thickness W. The design method of the CB-layer is discussed in some detail. The simulation results are shown to be in perfect agreement with the theory. The structure has application to a wide variety of different power devices. An RMOST structure has been used to demonstrate the benefits of the technique in the paper, for which excellent performance is demonstrated. 相似文献