全文获取类型
收费全文 | 31298篇 |
免费 | 3189篇 |
国内免费 | 2153篇 |
专业分类
电工技术 | 1471篇 |
综合类 | 2096篇 |
化学工业 | 6865篇 |
金属工艺 | 3401篇 |
机械仪表 | 1062篇 |
建筑科学 | 2023篇 |
矿业工程 | 1046篇 |
能源动力 | 944篇 |
轻工业 | 1401篇 |
水利工程 | 786篇 |
石油天然气 | 677篇 |
武器工业 | 107篇 |
无线电 | 2343篇 |
一般工业技术 | 4429篇 |
冶金工业 | 6179篇 |
原子能技术 | 1349篇 |
自动化技术 | 461篇 |
出版年
2024年 | 94篇 |
2023年 | 471篇 |
2022年 | 743篇 |
2021年 | 915篇 |
2020年 | 1038篇 |
2019年 | 976篇 |
2018年 | 964篇 |
2017年 | 1045篇 |
2016年 | 1037篇 |
2015年 | 991篇 |
2014年 | 1534篇 |
2013年 | 1664篇 |
2012年 | 2035篇 |
2011年 | 2178篇 |
2010年 | 1679篇 |
2009年 | 1737篇 |
2008年 | 1568篇 |
2007年 | 1894篇 |
2006年 | 2065篇 |
2005年 | 1711篇 |
2004年 | 1623篇 |
2003年 | 1431篇 |
2002年 | 1222篇 |
2001年 | 1052篇 |
2000年 | 923篇 |
1999年 | 659篇 |
1998年 | 533篇 |
1997年 | 455篇 |
1996年 | 442篇 |
1995年 | 358篇 |
1994年 | 322篇 |
1993年 | 238篇 |
1992年 | 229篇 |
1991年 | 175篇 |
1990年 | 157篇 |
1989年 | 116篇 |
1988年 | 77篇 |
1987年 | 65篇 |
1986年 | 66篇 |
1985年 | 36篇 |
1984年 | 32篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1974年 | 4篇 |
1959年 | 5篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
新型壳聚糖/纳米二氧化硅杂化材料的制备与性能 总被引:10,自引:5,他引:5
在纳米S iO2颗粒表面引入羟丙基氯活性基团,得到功能化S iO2颗粒,再将羟丙基氯化的S iO2颗粒交联固定在壳聚糖上,制备了一种新型的壳聚糖/纳米S iO2杂化材料(简称杂化材料);通过傅里叶变换红外光谱、透射电镜、扫描电镜方法对杂化材料进行表征,采用热重(TG)分析研究杂化材料的热性能;考察了杂化材料的沉降速率和对金属离子Ca2+和M g2+的吸附能力。电镜分析结果表明,杂化材料微粒为纳米尺度的无机S iO2加强化的微粒,S iO2颗粒分散在材料中,形成均匀的表面;TG分析结果表明,杂化材料的热性能有所提高;沉降实验测得壳聚糖和杂化材料作为吸附剂的沉降时间分别为130.3,68.5s,表明杂化材料的沉降速率比壳聚糖的沉降速率快了近一倍;杂化材料对金属离子Ca2+和M g2+的吸附量分别可达到0.289 3,1.445 6mm ol/g。 相似文献
32.
33.
34.
35.
Based on the voltage and current fluctuating phenomenon in the arc plasma load under the negative-pulse-bias, usingthe plasma physics theory and analysis of computer simulation expatiates that the nature of plasma load in vacuumarc plasma is a capacitance 相似文献
36.
H. L. Du S. R. Rose Z. D. Xiang P. K. Datta X. Y. Li 《Materialwissenschaft und Werkstofftechnik》2003,34(4):421-426
The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl3 diffusion coating was studied in an environment of H2/H2S/H2O at 850oC. The kinetic results demonstrate that the TiAl3 coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al2O3 scale on the surface of the TiAl3‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate. 相似文献
37.
由于干态聚合物电解质目前还不能满足聚合物锂离子电池的应用要求,人们致力于开发含液体增塑剂的聚合物电解质,包括凝胶型和微孔型两类体系。本文综述了含液聚合物电解质的最新进展,重点论述了各种新体系和新方法。 相似文献
38.
基于对地观测激光回波特征的目标特性研究 总被引:5,自引:0,他引:5
本文研究了对地观测激光回波特征与地面目标特征之间的关系模型,分析了分类地面目标的激光回波特征,提出一种基于查表法的目标特性计算方法并给出了仿真结果。 相似文献
39.
Effect of Stoichiometry on Properties of Rare-Earth-Based Hydrogen Storage Alloy for Nickel-Metal Hydride Secondary Battery 总被引:2,自引:0,他引:2
Effect of stoichiometry on microstructures, electrochemical properties and PCT characteristics of the alloys MI(Ni0.71Co0.15-Al0.06Mn0.08)x (MI=Lanthanum-rich Michmetal, x=4.6~5.2) have been investigated. The lattice constants a, c, and cellvolumes of non-stoichiometric alloys are bigger than those of the stoichiometric alloy. With the increasing stoichiometry x,the value of a decreases, and the value of c and cell volume increases except for those of the stoichiometric alloy; the plateaupressure of PCT curve, discharge capacity and cycling stability all increase. The alloy with x=5.2 shows the highest dischargecapacity and the best cycling stability among the studied alloys. 相似文献
40.
Electro-organic synthesis without supporting electrolyte: Possibilities of solid polymer electrolyte technology 总被引:1,自引:0,他引:1
J. Jörissen 《Journal of Applied Electrochemistry》2003,33(10):969-977
The application of ion exchange membranes as solid polymer electrolytes (SPE) in fuel cells is state-of-the-art. This technology needs no supporting electrolyte; consequently it can be applied for electro-organic syntheses in order to save process steps. In this case the process is not predetermined to a maximized energy efficiency so that the selection of the cell design, of the electrode materials and of the operating conditions can be focused on a high selectivity of the electrode reactions. The electro-osmotic stream, which is caused by the solvation shells of the ions during their migration through the membrane, and hence is a typical property of SPE technology, has a significant effect on the electrode reactions. It generates enhanced mass transfer at the electrodes, which is beneficial for reaction selectivity. It can be influenced by the choice of, and possibly by the preparation of, the membrane. An additional remarkable advantage of SPE technology is the exceptional long durability of oxide coated electrodes. By combination of several process engineering methods stable operation of SPE cells has been realized, even for examples of non-aqueous reaction systems. Experiments up to 6000 h duration and in cells of up to 250 cm2 membrane area show the potential for industrial application. 相似文献