全文获取类型
收费全文 | 175141篇 |
免费 | 20872篇 |
国内免费 | 14806篇 |
专业分类
电工技术 | 16260篇 |
综合类 | 18048篇 |
化学工业 | 21295篇 |
金属工艺 | 11994篇 |
机械仪表 | 12487篇 |
建筑科学 | 13340篇 |
矿业工程 | 6624篇 |
能源动力 | 4635篇 |
轻工业 | 20310篇 |
水利工程 | 6051篇 |
石油天然气 | 5785篇 |
武器工业 | 2280篇 |
无线电 | 19470篇 |
一般工业技术 | 14603篇 |
冶金工业 | 6762篇 |
原子能技术 | 3315篇 |
自动化技术 | 27560篇 |
出版年
2024年 | 1094篇 |
2023年 | 2941篇 |
2022年 | 6932篇 |
2021年 | 8877篇 |
2020年 | 6515篇 |
2019年 | 4440篇 |
2018年 | 4758篇 |
2017年 | 5467篇 |
2016年 | 4878篇 |
2015年 | 7791篇 |
2014年 | 9909篇 |
2013年 | 11411篇 |
2012年 | 14278篇 |
2011年 | 14674篇 |
2010年 | 14561篇 |
2009年 | 13761篇 |
2008年 | 14228篇 |
2007年 | 14002篇 |
2006年 | 11821篇 |
2005年 | 9892篇 |
2004年 | 7179篇 |
2003年 | 4732篇 |
2002年 | 4477篇 |
2001年 | 4235篇 |
2000年 | 3427篇 |
1999年 | 1470篇 |
1998年 | 538篇 |
1997年 | 490篇 |
1996年 | 361篇 |
1995年 | 285篇 |
1994年 | 214篇 |
1993年 | 213篇 |
1992年 | 154篇 |
1991年 | 106篇 |
1990年 | 102篇 |
1989年 | 114篇 |
1988年 | 72篇 |
1987年 | 55篇 |
1986年 | 50篇 |
1985年 | 29篇 |
1984年 | 20篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 32篇 |
1980年 | 54篇 |
1979年 | 29篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1959年 | 33篇 |
1951年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
In the last decade the 'comet assay' or 'single cell gel electrophoresis assay' has been established as a sensitive method for the detection of DNA damage and the measurement of its recovery. The results published in the literature have often been obtained with different methods for comet structure measurement. In most cases these data are not comparable with each other. Even when using similar systems for the analysis, it is difficult to obtain matching data. This presentation will describe some technical aspects of our measurement equipment and evaluation software. It focuses on necessary experimental conditions to minimize errors in obtaining such data. The software developed here allows the rapid analysis of the microscopic samples (< 2 s per image). The image analysis was designed with respect to the morphological shapes of comet cells, which were investigated with a confocal laser microscope. The system is built with standard components which are commercially available. As a measure of the amount of DNA damage the ratio of fluorescence intensity was used inside the comet tail and the fluorescence intensity of the comet head. Other parameters such as DNA content, comet area, head radius, tail length and tail moment are also determined. The reproducibility of the system has been evaluated in several experiments over a period of 5 years. 相似文献
103.
结合当前我国建材市场的形势 ,就建材市场“涨价风潮”的起因 ,从经济增长的结果、市场运行的规律等方面进行了论述 ,提出了涨价风潮对近期全国建材市场的影响 相似文献
104.
The microstructure development of Pd77.5Au6Si16.5 alloy droplet solidified in a drop tube process was studied. It was found that two distinct microstructures, i.e. (Pd,Au)3Si primary phase and Pd+(Pd,Au)3Si eutectic can be obtained when the droplet diameter is within the range between 2.3~0.4 mm. The morpologies of the (Pd,Au)3Si developed from dendrite trunk-like with single branching only into dendrite cluster-like with ternary branching with the decrease of the droplet diameter. When the droplet diameter is about 0.25 mm, the primary phase (Pd,Au)3Si almost disappears and the microstructure mainly shows Pd+(Pd,Au)3Si eutectic. The morphology of the eutectic transforms from fiber-like to plate-like with the decrease of the droplet diameter in the range between 2.3-0.25 mm. When the droplet diameter is about 0.19 mm, the microstructure is only the single phase of Pd solid solution 相似文献
105.
106.
107.
108.
Nd:碲酸盐玻璃的光谱和激光性质 总被引:2,自引:0,他引:2
对比了各种激光玻璃的光谱性质,指出碲酸盐玻璃是一咱理想的激光介质,并资产在室温下实现了钛宝石激光器泵浦了Nd:碲酸盐块体玻璃的激光发射,激光阈值4.20mJ,斜率效率14.7%。 相似文献
109.
110.
TiNi shape memory alloys prepared by normal sintering 总被引:4,自引:0,他引:4
Ning Zhang P. Babayan Khosrovabadi J. H. Lindenhovius B. H. Kolster 《Materials Science and Engineering: A》1992,150(2):263-270
This paper covers the use of conventional press and sinter of titanium and nickel equiatomic blends, involving transient liquid phases. A notable development has been the fabrication of homogeneous compacts from the elemental powders. Results indicate that employment of a double-stage sintering cycle is effective to sustain the geometrical integrity of the sintered sample. The TiNi alloy prepared in this manner exhibits a recovery strain of 4.6% by generating a restoring stress of 230 MPa, with a martensitic transformation point Ms of 34 °C. 相似文献