全文获取类型
收费全文 | 205752篇 |
免费 | 15375篇 |
国内免费 | 7808篇 |
专业分类
电工技术 | 11244篇 |
技术理论 | 14篇 |
综合类 | 11214篇 |
化学工业 | 35702篇 |
金属工艺 | 10538篇 |
机械仪表 | 11997篇 |
建筑科学 | 16413篇 |
矿业工程 | 4942篇 |
能源动力 | 5849篇 |
轻工业 | 12687篇 |
水利工程 | 3211篇 |
石油天然气 | 11074篇 |
武器工业 | 1345篇 |
无线电 | 25487篇 |
一般工业技术 | 26718篇 |
冶金工业 | 10934篇 |
原子能技术 | 2114篇 |
自动化技术 | 27452篇 |
出版年
2024年 | 881篇 |
2023年 | 3262篇 |
2022年 | 5827篇 |
2021年 | 7929篇 |
2020年 | 5799篇 |
2019年 | 5015篇 |
2018年 | 5417篇 |
2017年 | 6200篇 |
2016年 | 5692篇 |
2015年 | 7290篇 |
2014年 | 9520篇 |
2013年 | 12271篇 |
2012年 | 12226篇 |
2011年 | 13872篇 |
2010年 | 11611篇 |
2009年 | 11461篇 |
2008年 | 10873篇 |
2007年 | 10468篇 |
2006年 | 10858篇 |
2005年 | 9629篇 |
2004年 | 6565篇 |
2003年 | 5778篇 |
2002年 | 5252篇 |
2001年 | 4723篇 |
2000年 | 4868篇 |
1999年 | 5637篇 |
1998年 | 5283篇 |
1997年 | 4351篇 |
1996年 | 3956篇 |
1995年 | 3310篇 |
1994年 | 2768篇 |
1993年 | 2187篇 |
1992年 | 1700篇 |
1991年 | 1277篇 |
1990年 | 1018篇 |
1989年 | 877篇 |
1988年 | 681篇 |
1987年 | 496篇 |
1986年 | 394篇 |
1985年 | 334篇 |
1984年 | 212篇 |
1983年 | 198篇 |
1982年 | 163篇 |
1981年 | 145篇 |
1980年 | 131篇 |
1979年 | 97篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
62.
It has been observed that herpes simplex virus mutants with deficient or altered thymidine kinase activity are more susceptible to Cidofovir (CDV; 1-[(S)-3-hydroxy-2-(phosphonomethoxy)propyl]cytosine dihydrate) in tissue culture than are the parental strains. During infection of cells, the elevation of the dCTP pool by thymidine kinase mutant viruses is less than that induced by the wild-type virus. The competition between CDV diphosphate and dCTP at the viral polymerase is therefore changed in favor of CDV diphosphate, enhancing its activity. 相似文献
63.
We compared the data from four growth hormone (GH) immunoassays for analyzing 24-h GH profiles in four apparently normal subjects and four obese subjects (508 serum samples). The detection limit was 0.02 microgram/L for one immunochemiluminometric assay (ICMA), 0.1 microgram/L for two IRMAs, and 0.4 microgram/L for one RIA. All GH pulses with a peak ICMA value > 1 microgram/L were detected by each of the other methods. Overall, the correlation coefficient between the values obtained with all four assays exceeded 0.90. However, for GH concentrations < or = 0.25 microgram/L, acceptable concordance (r2 > or = 0.80) was reached only between the ICMA and one IRMA; between the ICMA and the RIA, concordance was acceptable only for GH concentrations > or = 10 micrograms/L. In the normal subjects, the percentage of undetectable values was 0% with the ICMA but 29% with one of the IRMAs; in obese subjects, the corresponding values were 12% and 38%. 相似文献
64.
应用音平化渣图象分析和指导转炉造渣操作 总被引:3,自引:1,他引:2
利用音平化渣图象可以清晰地看出在转炉造渣过程中何时发生喷溅,何时发生炉渣返干和何时化渣正常。应用音平化渣图象和炉渣三元相图,可以正确地分析发生喷溅和返干的原因,从而找到避免突发性喷溅和严重返干的方法。正确的枪位和炉渣碱度控制是实现平稳吹炼的保证,而音平化渣图象能帮助操作工实现这一目标。 相似文献
65.
Fanggao Chang Tao Li Yongxia Ge Zhenping Chen Zhongshi Liu Xiping Jing 《Journal of Materials Science》2007,42(17):7109-7115
DC resistivity, dielectric constant, dielectric loss and positron annihilation spectra of (Ba1−x
Ho
x
)TiO3 ceramics have been measured as a function of holmium concentration x. It has been found that the DC resistivity of (Ba1−x
Ho
x
)TiO3 is strongly dependent on the Ho content: it decreases three orders of magnitude and reaches a minimum at x = 0.4%. Doping with 0.6% holmium increases the permittivity of BaTiO3 by approximately three times (from ∼1,300 to ∼4,000), with only a slight increase in the corresponding dielectric loss. The
local electron density and defect concentration estimated using positron annihilation technique conforms well to the features
found in the dielectric and resistivity measurements. The results have been discussed in terms of a mixed compensation model. 相似文献
66.
Gang Chen Zhonghua Yang Chor Ping Low 《Industrial Informatics, IEEE Transactions on》2006,2(4):269-280
In this paper, we address agent coordination from a dynamic systems perspective and propose a dynamic coordination model, which is inspired by biological metabolic systems. A new coordination mechanism through dynamic local adjustment (CDLA) is presented, and coordination is achieved when every agent utilizes explicitly the global system dynamics and performs iteratively a dynamic local adjustment procedure. The CDLA mechanism is investigated in an example multiagent shop floor system. The results show that the example manufacturing process is well-coordinated and the coordination approach is practically applicable and effective 相似文献
67.
Chai-Chin Lin Chih-Ming Chen Jenn-Hwan Tarng Hsueh-Ming Hang Hsiao-Cheng Yu 《Broadcasting, IEEE Transactions on》2002,48(1):38-43
Field tests of the transmission performance of the ATSC DTV system have been conducted in Taiwan. The test results as well as comparisons against the NTSC system performance are reported and analyzed. From the measured results the reception characteristics of the DTV can be deduced and can provide guidelines for television stations to design the transmission system, schedule equipment deployment, plan service coverage areas, and improve the reception quality of the digital signal 相似文献
68.
69.
The paper presented some interesting results on the selection of near-minimum time geometric paths for robotic manipulators. However, there are certain parts of this paper which need to be clarified. 相似文献
70.
以TD—SCDMA既有进展及面临的挑战与NGBWM的发展走向为基础,重点论述自主创新导向下的TD—SCDMA与NGBWM务实发展战略思考。 相似文献