全文获取类型
收费全文 | 123518篇 |
免费 | 11820篇 |
国内免费 | 7620篇 |
专业分类
电工技术 | 9004篇 |
技术理论 | 8篇 |
综合类 | 9578篇 |
化学工业 | 18211篇 |
金属工艺 | 8036篇 |
机械仪表 | 8433篇 |
建筑科学 | 9964篇 |
矿业工程 | 3942篇 |
能源动力 | 3858篇 |
轻工业 | 8637篇 |
水利工程 | 2935篇 |
石油天然气 | 6334篇 |
武器工业 | 1432篇 |
无线电 | 14522篇 |
一般工业技术 | 13280篇 |
冶金工业 | 5173篇 |
原子能技术 | 1764篇 |
自动化技术 | 17847篇 |
出版年
2024年 | 554篇 |
2023年 | 1767篇 |
2022年 | 3372篇 |
2021年 | 4881篇 |
2020年 | 3686篇 |
2019年 | 3085篇 |
2018年 | 3372篇 |
2017年 | 3877篇 |
2016年 | 3579篇 |
2015年 | 5174篇 |
2014年 | 6543篇 |
2013年 | 7787篇 |
2012年 | 8926篇 |
2011年 | 9776篇 |
2010年 | 9088篇 |
2009年 | 8689篇 |
2008年 | 8706篇 |
2007年 | 8416篇 |
2006年 | 8005篇 |
2005年 | 6449篇 |
2004年 | 4630篇 |
2003年 | 3845篇 |
2002年 | 3710篇 |
2001年 | 3125篇 |
2000年 | 2619篇 |
1999年 | 2139篇 |
1998年 | 1418篇 |
1997年 | 1151篇 |
1996年 | 997篇 |
1995年 | 831篇 |
1994年 | 659篇 |
1993年 | 486篇 |
1992年 | 356篇 |
1991年 | 266篇 |
1990年 | 205篇 |
1989年 | 159篇 |
1988年 | 130篇 |
1987年 | 97篇 |
1986年 | 83篇 |
1985年 | 52篇 |
1984年 | 48篇 |
1983年 | 41篇 |
1982年 | 29篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 17篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1959年 | 19篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m?2 and 45 W m?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m?1 to 30.2 MPa and 158 J m?1, respectively. Copyright © 2003 Society of Chemical Industry 相似文献
2.
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
3.
Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage. © 2003 Society of Chemical Industry 相似文献
4.
Polymer networks in which poly(propylene imine) dendrimers (Astramol?) are connected to each other by linear polytetrahydrofuran (polyTHF) segments, were prepared by two methods. The first method was a one‐step procedure in which bifunctionally living polyTHF, obtained by initiation of the THF polymerization with trifluoromethane sulfonic anhydride (triflic anhydride), was reacted with an amino‐dendrimer. This reaction was very fast but did not allow formation of the end products. The second method was a two‐step procedure. In a first step, living polyTHF, prepared with acryloyloxybutyl triflate as initiator, was grafted on an amino‐dendrimer, to form a star‐like, acrylate‐terminated polyTHF multi‐macromonomer with the dendrimer as core. In a second step, networks were obtained by Michael addition between the acrylate end‐groups and unreacted amino‐groups of the dendrimer. This cross‐linking reaction occurred spontaneously upon heating of the solution of the multi‐macromonomer with gelation times varying from a few minutes to a few hours, depending on the temperature and the composition of the prepolymers. With this method it was possible to prepare networks in the form of coatings or films. © 2003 Society of Chemical Industry 相似文献
5.
Liang Y.C. Wenjiang Zeng Pick Hong Ong Zhaoxia Gao Jun Cai Balasubramanian N. 《Electron Device Letters, IEEE》2002,23(12):700-703
In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology. 相似文献
6.
Jun Chen Berger T. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(8):3385-3398
We consider a distributed source coding system in which several observations must be encoded separately and communicated to the decoder by using limited transmission rate. We introduce a robust distributed coding scheme which flexibly trades off between system robustness and compression efficiency. The optimality of this coding scheme is proved for various special cases. 相似文献
7.
2007年国外有机硅进展 总被引:2,自引:0,他引:2
根据2007年公开发表的相关资料,综述了2007年国外有机硅行业的市场动向、行业动向及有机硅产品的研发进展. 相似文献
8.
Aimin Xiang Zhongjie Du Qinghua Zeng Chen Zhang Hangquan Li 《Polymer International》2005,54(10):1366-1370
This paper presents recent efforts on the preparation of flexible polyhedral particles via concentrated emulsion templating polymerization in which the hydrophilic monomer (acrylamide) and hydrophobic monomer (butyl acrylate) are polymerized simultaneously in the continuous and dispersed phase, respectively. Such templating polymerization has been enhanced in our systems owing to the introduction of acrylamide monomer and their higher polymerization rate in continuous phase as compared with butyl acrylate in dispersed phase. Diffusion between the different phases was also inhibited. Furthermore, the stability of the concentrated emulsion and the molecular weight of the produced poly(butyl acrylate) were found to be significantly affected by the amount of redox initiator. The morphology of the particles could be controlled by varying the volume fraction of the dispersed phase and the polyhedral particles were achieved at higher volume fraction. Copyright © 2005 Society of Chemical Industry 相似文献
9.
10.