全文获取类型
收费全文 | 24283篇 |
免费 | 1811篇 |
国内免费 | 637篇 |
专业分类
电工技术 | 1408篇 |
技术理论 | 3篇 |
综合类 | 1436篇 |
化学工业 | 3917篇 |
金属工艺 | 1288篇 |
机械仪表 | 1529篇 |
建筑科学 | 2089篇 |
矿业工程 | 823篇 |
能源动力 | 671篇 |
轻工业 | 1381篇 |
水利工程 | 383篇 |
石油天然气 | 1646篇 |
武器工业 | 125篇 |
无线电 | 2529篇 |
一般工业技术 | 2956篇 |
冶金工业 | 1095篇 |
原子能技术 | 338篇 |
自动化技术 | 3114篇 |
出版年
2025年 | 67篇 |
2024年 | 610篇 |
2023年 | 602篇 |
2022年 | 744篇 |
2021年 | 1026篇 |
2020年 | 937篇 |
2019年 | 816篇 |
2018年 | 760篇 |
2017年 | 830篇 |
2016年 | 737篇 |
2015年 | 891篇 |
2014年 | 1178篇 |
2013年 | 1280篇 |
2012年 | 1473篇 |
2011年 | 1507篇 |
2010年 | 1360篇 |
2009年 | 1204篇 |
2008年 | 1185篇 |
2007年 | 1169篇 |
2006年 | 1214篇 |
2005年 | 1125篇 |
2004年 | 701篇 |
2003年 | 596篇 |
2002年 | 539篇 |
2001年 | 506篇 |
2000年 | 475篇 |
1999年 | 619篇 |
1998年 | 478篇 |
1997年 | 409篇 |
1996年 | 364篇 |
1995年 | 325篇 |
1994年 | 249篇 |
1993年 | 150篇 |
1992年 | 137篇 |
1991年 | 122篇 |
1990年 | 87篇 |
1989年 | 71篇 |
1988年 | 54篇 |
1987年 | 31篇 |
1986年 | 31篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1958年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
研究了Al2O3-TiB2陶瓷刀具材料在1000℃下的氧化行为,用XRD、SEM分析了氧化后的相组成及显微结构。结果表明:Al2O3-TiB2陶瓷材料在1000℃空气中氧化增重符合抛物线规律;随TiB2含量的增加,该材料的抗氧化能力下降。 相似文献
3.
Neural Computing and Applications - Image classification method is currently the more popular image technology, but it still has certain problems in practice. In order to improve the image... 相似文献
4.
研究了热处理对Ag-15Al(at%)固溶体合金电阻率和有序参数的影响,由X射线衍射分析表明,合金的短程序转变不是Ag_3Al化合物型的δ第二相的形成,而是α-Ag-Al固溶体原子的有序排列。 相似文献
5.
6.
7.
Tensile properties and failure mechanism of a newly developed three-dimensional (3D) woven composite material named 3D nonorthogonal woven composite are investigated in this paper. The microstructure of the composite is studied and the tensile properties are obtained by quasi-static tensile tests. The failure mechanism of specimen is discussed based on observation of the fracture surfaces via electron microscope. It is found that the specimens always split along the oblique yarns and produce typical v-shaped fracture surfaces. The representative volume cell (RVC) is established based on the microstructure. A finite element analysis is conducted with periodical boundary conditions. The finite element simulation results agree well with the experimental data. By analyzing deformation and stress distribution under different loading conditions, it is demonstrated that finite element model based on RVC is valid in predicting tensile properties of 3D nonorthogonal woven composites. Stress distribution shows that the oblique yarns and warp yarns oriented along the x direction carry primary load under x tension and that warp yarns bear primary load under y tension. 相似文献
8.
Deng Juan Zhao Shu Wang Yan Wang Lei Wang Hong Sha Hong 《Multimedia Tools and Applications》2017,76(7):10097-10117
Multimedia Tools and Applications - Most of the existing image encryption algorithms based on compressive sensing are too complex to operate. An image compression-encryption scheme with simple... 相似文献
9.
10.
The temporal scale effect of loading data on nitrate-nitrogen load computation was examined using outputs of watershed modeling tool Hydrologic Simulation Program-FORTRAN (HSPF) for the Amite River in Louisiana, USA. The daily nitrate-nitrogen concentrations simulated using the HSPF were employed first to obtain daily, weekly, bi-weekly, and monthly average data and then to develop load duration curves for the data with four different temporal scales. The duration curves exhibited high variability in the load estimated using daily data as compared with those based on bi-weekly and monthly data. According to daily data, the nitrate-nitrogen load in the winter was found to be 2,780 kg. The nitrate-nitrogen load decreased with increasing temporal (daily, weekly, bi-weekly, and monthly) scale (commonly used in water quality monitoring) of the data. The coefficient of variation, used to quantify the effect of temporal scale on the load, was found to be linearly and inversely correlated with the logarithm of the time scale. Based on the finding, empirical equations were proposed to extrapolate near real-time data for flow and nitrate-nitrogen, greatly simplifying nutrient monitoring and reducing the cost involved in water quality monitoring. 相似文献