全文获取类型
收费全文 | 255313篇 |
免费 | 16043篇 |
国内免费 | 8442篇 |
专业分类
电工技术 | 11549篇 |
技术理论 | 8篇 |
综合类 | 15314篇 |
化学工业 | 40369篇 |
金属工艺 | 14096篇 |
机械仪表 | 13433篇 |
建筑科学 | 16103篇 |
矿业工程 | 5385篇 |
能源动力 | 5817篇 |
轻工业 | 18448篇 |
水利工程 | 4565篇 |
石油天然气 | 9646篇 |
武器工业 | 1436篇 |
无线电 | 28320篇 |
一般工业技术 | 35441篇 |
冶金工业 | 10130篇 |
原子能技术 | 2077篇 |
自动化技术 | 47661篇 |
出版年
2024年 | 836篇 |
2023年 | 2948篇 |
2022年 | 5410篇 |
2021年 | 7202篇 |
2020年 | 5562篇 |
2019年 | 4597篇 |
2018年 | 18706篇 |
2017年 | 18498篇 |
2016年 | 14482篇 |
2015年 | 7587篇 |
2014年 | 9079篇 |
2013年 | 10515篇 |
2012年 | 14562篇 |
2011年 | 21626篇 |
2010年 | 19180篇 |
2009年 | 15985篇 |
2008年 | 17082篇 |
2007年 | 17481篇 |
2006年 | 10003篇 |
2005年 | 9518篇 |
2004年 | 6906篇 |
2003年 | 6050篇 |
2002年 | 5291篇 |
2001年 | 4297篇 |
2000年 | 4226篇 |
1999年 | 3996篇 |
1998年 | 3223篇 |
1997年 | 2663篇 |
1996年 | 2488篇 |
1995年 | 2138篇 |
1994年 | 1678篇 |
1993年 | 1212篇 |
1992年 | 979篇 |
1991年 | 792篇 |
1990年 | 554篇 |
1989年 | 496篇 |
1988年 | 417篇 |
1987年 | 275篇 |
1986年 | 190篇 |
1985年 | 115篇 |
1984年 | 77篇 |
1983年 | 60篇 |
1982年 | 72篇 |
1980年 | 52篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 48篇 |
1959年 | 43篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
21.
Introduction
The IEC central office informed in 7/543/AC that the secretariat of TC 7 would be taken over by the Chinese National Committee on January 10, 2003 and affirmed subsequently in 7/544/AC that the secretariat of TC 7 has been taken over by the Chinese National Committee which appointing secretary in Shanghai Electric Cable Research Institute as no objection has been raised by the Standardization Management Board members. It's the first IEC secretariat that assumed by China, with great significance, just as commented by the media that the commitment indicate undoubtedly China is to play a much more active and important role in the world especially after its entry into world trade organization as well as the trend of global economic integration. 相似文献
22.
为了提高注入剖面测井的准确性,研制了一种新型注入剖面组合测井仪。该仪器由流量处理单元、伽马处理单元、井温处理单元、磁性定位处理单元、调制式传输、电源电路六部分组成。一次下井可同时测取流量、伽马、井温、磁性定位四组参数。具有测取资料精度高、单芯电缆传输、流量可单点测量也可连续测量以厦现场监测和维修方便等特点。 相似文献
23.
Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted
calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical
composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX
and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite
particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies
by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give
clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse
to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites
could be useful for hyperthermia. 相似文献
24.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method
in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer.
But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results
showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that,
the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic
whereas chloride doped polyaniline films were found to be highly hygroscopic. 相似文献
25.
26.
A multi-level attention framework for tracking and segmentation of humans and objects under complex occlusions is investigated,
featuring an effective probabilistic appearance-based technique for pixel reclassification during object grouping and splitting.
A novel ’spatial-depth affinity metric’ is introduced in the conventional likelihood function, utilising information of both
spatial locations of pixels and dynamic depth ordering of the component objects in grouping. Depth ordering estimation is
achieved through a combination of top-down and bottom-up approach. Experiments on some realworld difficult scenarios of low
quality and highly compressed videos demonstrate the very promising results achieved. 相似文献
27.
28.
29.
主要对各国3G许可证与使用技术标准的抽绑政策.各国对2G/3G网络漫游的管制规定。以及3G网络之间共享的种类及实施方式等方面做了详尽的讲解,并进行比较和分析。 相似文献
30.
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