全文获取类型
收费全文 | 52512篇 |
免费 | 9409篇 |
国内免费 | 5809篇 |
专业分类
电工技术 | 4692篇 |
技术理论 | 2篇 |
综合类 | 4784篇 |
化学工业 | 1993篇 |
金属工艺 | 1045篇 |
机械仪表 | 3557篇 |
建筑科学 | 2059篇 |
矿业工程 | 982篇 |
能源动力 | 422篇 |
轻工业 | 4352篇 |
水利工程 | 447篇 |
石油天然气 | 1028篇 |
武器工业 | 979篇 |
无线电 | 12236篇 |
一般工业技术 | 3373篇 |
冶金工业 | 750篇 |
原子能技术 | 488篇 |
自动化技术 | 24541篇 |
出版年
2024年 | 579篇 |
2023年 | 1605篇 |
2022年 | 2596篇 |
2021年 | 2795篇 |
2020年 | 2716篇 |
2019年 | 2119篇 |
2018年 | 1826篇 |
2017年 | 2341篇 |
2016年 | 2445篇 |
2015年 | 2800篇 |
2014年 | 4289篇 |
2013年 | 3716篇 |
2012年 | 4504篇 |
2011年 | 4746篇 |
2010年 | 3587篇 |
2009年 | 3510篇 |
2008年 | 3584篇 |
2007年 | 3841篇 |
2006年 | 3066篇 |
2005年 | 2572篇 |
2004年 | 1878篇 |
2003年 | 1550篇 |
2002年 | 1113篇 |
2001年 | 779篇 |
2000年 | 640篇 |
1999年 | 484篇 |
1998年 | 402篇 |
1997年 | 294篇 |
1996年 | 283篇 |
1995年 | 199篇 |
1994年 | 133篇 |
1993年 | 122篇 |
1992年 | 113篇 |
1991年 | 97篇 |
1990年 | 81篇 |
1989年 | 40篇 |
1988年 | 50篇 |
1987年 | 24篇 |
1986年 | 30篇 |
1985年 | 27篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Mirona K. Mironova 《Cement and Concrete Research》2002,32(1):9-15
The paper treats complex phenomena that accompany the diffusion of sulfate ions into cement paste or systems. The ion distribution within the material was studied by designing a specific diffusion model. The model accounts for two phenomena: capillary filling with products of the chemical reactions and the subsequent liquid push out of the capillary. The approach allows to quantify the concentration of free ions having penetrated the cement stone and that of chemically reacted ions, and to assess the liquid push out. Experimental data are also presented. 相似文献
82.
郑晓东 《石油地球物理勘探》1991,(5)
本文介绍了一系列简单而实用的 AVO 异常显示、检测和增强的新技术。包括:共炮检距(或相近)显示技术、振幅比值显示技术、滚动显示技术、线性转换显示技术、抛物线转换显示技术和 AVO 增强技术。文中以实例说明了上述各种方法的应用情况。 相似文献
83.
84.
85.
基于误码率与Q值的对应关系,本文介绍一种Q值在线检测方法,模块设计采用DSP技术,并讨论了该模块在光纤工业专用网(FIN)中的应用。 相似文献
86.
城市现有地下管线探查及数据处理方法探讨 总被引:4,自引:0,他引:4
该文根据城市地下管线探查及数据处理方法现状 ,结合管线管理单位需要 ,对地下管线探查及数据处理方法中的有关问题进行了探讨 ,供今后管线探测工作借鉴 相似文献
87.
R. Talero 《Cement and Concrete Research》2002,32(5):707-717
In this research, former XRD experiments have been verified by Le Chatelier-Ansttet (L-A) test. For this purpose, 28 cements consisting of 7 Portland cements and 21 blended cements containing 20%, 30% and 40% metakaolin have been submitted to the Le Chatelier-Anstett (L-A) test for 2 years. With all these cements, L-A specimens were manufactured and a direct parameter was measured for these specimens: increase in diameter, Δ∅, or diameter growth. Other complementary determinations were chemical analysis, XDA patterns and SEM of ettringites and specific properties of some cements tested. The experimental results have borne out that the formation rate of the ettringite formed from the reactive alumina, Al2O3r−, present in pozzolans must be considerably higher than the formation rate of the ettringite from C3A and much higher than the ettringite from C4AF, both present in OPC. Owing to this, these ettringites were proposed being named “rapid formation” (ett-rf), “slow formation” (ett-lf) and “very slow formation” (ett-vlf) ettringites, respectively. On the other hand, these experimental results have also shown that the ett-rf has a much smaller size than the ett-lf (this is a direct consequence of the aforementioned conclusion); that almost all the alumina, Al2O3, present in M pozzolan must be regarded as being “reactive,” Al2O3r−, or at least, the greatest part; that the detrimental effects derived from gypsum attack are shown much earlier in these POZC than in their plain OPC and, to such an extent, that this aggressive action can be described as rapid gypsum attack; and that none of the 21 POZC tested can be described as high nor moderate sulphate resistant cements according to L-A test. 相似文献
88.
89.
T. MATTILA-SANDHOLM T. ALI-VEHMAS G. WIRTANEN U. RÖNNER M. SANDHOLM 《International Journal of Food Science & Technology》1991,26(3):325-336
Automated monitoring of the microbiological quality of heat-processed foods by the resazurin reduction test was applied to microtitration plate incubator-fluorimeter technology. The appearance and disappearance of the fluorescing peak of resorufin was monitored on microtitration trays. Pasteurized or ultra-high temperature-treated starch-based soup was used as the model food system. Bacillus subtilis spores (ultra-high temperature treatment) and vegetative cells of Enterococcus faecalis (pasteurization) were inoculated into the soup before the heat treatment at levels which resulted in some survival. The timing of appearance of maximum fluorescence correlated with the number of bacteria in pre-incubated samples. Automated resazurin-reduction fluorimetry was compared with conventional plating, turbidometry and microcolony count by the direct epifluorescent filter technique. The results of the resazurin test correlated well with those of all the other methods tested. Fluorimetry had the advantage that the results could be read within 1–5h and the reproducibility was superior to the other methods. 相似文献
90.
补偿元件对载体催化元件输出特性的影响 总被引:2,自引:1,他引:1
阐述了矿井瓦斯传感器-载体催化元件在应用中,补偿元件发挥的作用和工作原理,着重分析了补偿元件对载体催化元件输出特性的影响,探讨了提高线性补偿效果的方法。 相似文献