全文获取类型
收费全文 | 914786篇 |
免费 | 73659篇 |
国内免费 | 42593篇 |
专业分类
电工技术 | 59612篇 |
技术理论 | 90篇 |
综合类 | 67299篇 |
化学工业 | 141561篇 |
金属工艺 | 51496篇 |
机械仪表 | 59164篇 |
建筑科学 | 76281篇 |
矿业工程 | 30261篇 |
能源动力 | 25063篇 |
轻工业 | 62414篇 |
水利工程 | 18797篇 |
石油天然气 | 54981篇 |
武器工业 | 8143篇 |
无线电 | 101600篇 |
一般工业技术 | 95996篇 |
冶金工业 | 45369篇 |
原子能技术 | 9569篇 |
自动化技术 | 123342篇 |
出版年
2024年 | 3876篇 |
2023年 | 13127篇 |
2022年 | 25936篇 |
2021年 | 35762篇 |
2020年 | 26931篇 |
2019年 | 21207篇 |
2018年 | 24230篇 |
2017年 | 28156篇 |
2016年 | 25046篇 |
2015年 | 35582篇 |
2014年 | 45510篇 |
2013年 | 54370篇 |
2012年 | 59860篇 |
2011年 | 65252篇 |
2010年 | 58547篇 |
2009年 | 55398篇 |
2008年 | 54459篇 |
2007年 | 52243篇 |
2006年 | 52439篇 |
2005年 | 45303篇 |
2004年 | 30477篇 |
2003年 | 26672篇 |
2002年 | 25222篇 |
2001年 | 22700篇 |
2000年 | 21595篇 |
1999年 | 23021篇 |
1998年 | 17829篇 |
1997年 | 15256篇 |
1996年 | 14226篇 |
1995年 | 11820篇 |
1994年 | 9681篇 |
1993年 | 6710篇 |
1992年 | 5412篇 |
1991年 | 4090篇 |
1990年 | 3097篇 |
1989年 | 2565篇 |
1988年 | 2033篇 |
1987年 | 1341篇 |
1986年 | 1046篇 |
1985年 | 674篇 |
1984年 | 527篇 |
1983年 | 385篇 |
1982年 | 345篇 |
1981年 | 265篇 |
1980年 | 251篇 |
1979年 | 124篇 |
1978年 | 53篇 |
1977年 | 54篇 |
1976年 | 66篇 |
1951年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Zhang Yaocang 《中国油气》2006,13(1):12-15
Since the founding of P.R.China,Particularly after the lauch of reform and opening up in 1978,China's oil and gas industry has undergone a series of significant reforms and restructuring.it has set up a complete oil and gas industry system. 相似文献
3.
4.
World oil production and reserve additions heavily depend on giant oilfields. Currently, there are more than 4,000 producing oilfields in the world, producing around 68 million barrels of oil per day. Most oilfields in the world are minor ones, with oil production below 20,000 barrels per day; only 3% (about 120) oilfields in the world produce over 100,000 barrels per day with overall daily production exceeding 32 million barrels, which accounts for 47% of the total world oil supply . The scales of the oilfields heavily influence economic indices like investment, production and life spans of the oilfields. Therefore, giant oilfields have always been the dream of oil finders and targets of geologists' researches . 相似文献
5.
杨宇 《中国室内装饰装修天地》2006,(7):54-61
华风气象影视大楼总面积4万平方米,根据空间功能不同分为办公大楼和商务写字楼两部分,办公大楼是集演播室、制作机房、办公室为一体的九层综合性建筑。设计师杨宇在刚接触到这个项目的时候,面对的是一个既成事实的建筑。 相似文献
6.
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
7.
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
8.
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
9.
张媛媛 《安徽电子信息职业技术学院学报》2003,2(6):3-4
简要介绍了通用串行总线USB的特点,对USB接口芯片USBN9602的内部结构、引脚、寄存器组作了详细的论述,并介绍了其应用。 相似文献
10.
Shi-Jin Ding Hang Hu Lim H.F. Kim S.J. Yu X.F. Chunxiang Zhu Li M.F. Byung Jin Cho Chan D.S.H. Rustagi S.C. Yu M.B. Chin A. Dim-Lee Kwong 《Electron Device Letters, IEEE》2003,24(12):730-732
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications. 相似文献