全文获取类型
收费全文 | 58827篇 |
免费 | 6502篇 |
国内免费 | 4878篇 |
专业分类
电工技术 | 5331篇 |
综合类 | 5848篇 |
化学工业 | 7265篇 |
金属工艺 | 3797篇 |
机械仪表 | 3817篇 |
建筑科学 | 4494篇 |
矿业工程 | 2067篇 |
能源动力 | 1571篇 |
轻工业 | 6650篇 |
水利工程 | 1806篇 |
石油天然气 | 2231篇 |
武器工业 | 821篇 |
无线电 | 6356篇 |
一般工业技术 | 5277篇 |
冶金工业 | 2587篇 |
原子能技术 | 1259篇 |
自动化技术 | 9030篇 |
出版年
2024年 | 349篇 |
2023年 | 1004篇 |
2022年 | 2099篇 |
2021年 | 2734篇 |
2020年 | 2051篇 |
2019年 | 1488篇 |
2018年 | 1605篇 |
2017年 | 1885篇 |
2016年 | 1606篇 |
2015年 | 2564篇 |
2014年 | 3228篇 |
2013年 | 3911篇 |
2012年 | 4696篇 |
2011年 | 4818篇 |
2010年 | 4643篇 |
2009年 | 4506篇 |
2008年 | 4554篇 |
2007年 | 4524篇 |
2006年 | 3943篇 |
2005年 | 3287篇 |
2004年 | 2500篇 |
2003年 | 1758篇 |
2002年 | 1668篇 |
2001年 | 1508篇 |
2000年 | 1139篇 |
1999年 | 580篇 |
1998年 | 306篇 |
1997年 | 219篇 |
1996年 | 195篇 |
1995年 | 176篇 |
1994年 | 153篇 |
1993年 | 85篇 |
1992年 | 93篇 |
1991年 | 60篇 |
1990年 | 60篇 |
1989年 | 49篇 |
1988年 | 21篇 |
1987年 | 27篇 |
1986年 | 24篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1977年 | 1篇 |
1959年 | 9篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
宁东供水工程供水水泵共有卧式和立式离心泵2种方案可供选择,也是工程论证时争论的焦点,经综合比较及主机设备的国际招标,最终确定了奥地利安德里兹公司的卧式双吸中开式离心泵为宁东供水工程的供水水泵。 相似文献
2.
3.
4.
Disciplinary and linguistic considerations for academic Web linking: An exploratory hyperlink mediated study with Mainland China and Taiwan 总被引:4,自引:0,他引:4
The Web has become an important means of academic information exchange and can be used to give new insights into patterns
of informal scholarly communication. This study develops new methods to examine patterns of university Web linking, focusing
on Mainland China and Taiwan, and including language considerations. Multiple exploratory investigations into Web links were
conducted between universities in these two places. Firstly, inlinks were counted to each university Web site from its national
peers using four alternative Web document models. The results were shown to correlate significantly with research productivity
in Taiwan but not in the Mainland, although in the latter case less reliable institutional data could have been the cause.
For Taiwan, this is the first evidence of a scholarly association with academic linking for a non-English speaking region.
It was then ascertained that the same link counts associated more strongly with scientific than social scientific research
productivity in Taiwan. This confirms the general assumption of greater Web use by the hard sciences. We then investigated
Taiwan-Mainland university cross-links, and found that although English is extensively used on the Web, there was no evidence
that it was the language of preference for informal scholarly communication between the two areas.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
6.
In the present study, attempts are made to extend the application of the mechanical model for the fatigue crack initiation (FCI) and the FCI life formula of metallic notched elements in laboratory air to those in the corrosive environment. The test results and analysis of the corrosion FCI (CFCI) life of aluminum alloys and Ti---6A1---4V show that the expression of the CFCI life obtained by modifying the FCI life formula in laboratory air can give a good fit to the test results of the CFCI life. The salt water (3.5% NaCl) environment has no effects on the CFCI resistant coefficient compared with the FCI resistant coefficient in laboratory air. However, 3.5% NaCl environment greatly decreases the CFCI threshold of aluminum alloy, but has little effect on the CFCI threshold of Ti---6A1---4V. The loading frequency ranging from 1 Hz to 10 Hz has no appreciable effect on the CFCI life, and thus, the CFCI threshold of aluminum alloys investigated. Hence, the expression for the CFCI life of metallic notched elements proposed in this study is a better one, which reveals a correlation between the CFCI life and the governing parameters, such as, the geometry of the notched elements, the nominal stress range, the stress ratio, the tensile properties and the CFCI threshold. However, this new expression of the CFCI life needs to be verified by more test results. 相似文献
7.
制作压力传感器时,在二氧化硅层上淀积多晶硅膜,既可利用优良的机械特性,又可保证压敏电阻与衬底间具有良好的绝缘性,由此可大大提高器件的温度特性。介绍了一种多晶硅压力传感器的原理和设计。实验结果表明,这类传感器具有灵敏度好,精度高等特点,电路工作范围为0-250℃,且具有良好的温度稳定性。 相似文献
8.
橡胶卷材挤出连续硫化生产线的结构特色与工作原理 总被引:1,自引:0,他引:1
介绍了橡胶防水防腐卷材挤出连续硫化生产线的结构、特点和工作原理;指出在目前国内同类设备中,该生产设备具有先进性,并可替代引进设备。 相似文献
9.
A kind of complex additive mainly containing Al, Mg, F, and O was prepared. The synthetical performances of the property-modified prebaked anodes containing additives were tested in laboratory. On the basis of ideal testing results obtained, a large number of industrial prebaked property-modified anodes are prepared in a large-scale aluminum company. Further more, they are all used in 160 kA prebaked anode aluminum electrolysis cells. The statistic result show that, compared with common anodes, the property-modified ones enhance current by 11.6 kg per ton aluminum averagely. 相似文献
10.
XIAO Chang-jiang SUN Ming ZHOU Hong-yan LIU Sui-xin LONG Kai-chao HE Fei LI Tong 《中南工业大学学报(英文版)》2005,12(Z1)
Objective Study on the effect of NF-κB in ox-LDL injured HUVEC-304 and the intervention with the serum of Tongmai Decoction. Methods Tongmai Decoction herbage-contained serum was made by the serum pharmacology methods, then the HUVEC-304 cells were divided into 5 groups and incubated for 24 h: 1) normal group;2) fetal calf serum group; 3) ox-LDL group; 4) simvastatin group; 5) Tongmai Decoction group. RT-PCR was used to determine the mRNA of NF-κB in the cells, Western Blot Assay was used to determine the protein content of NF-κB in the cells. Results 1) Compared with the cells in normal group and serum control group , the endothelial cells in ox-LDL group are seriously injured, while those in Tongmai Decoction group grow better; 2) Compared with the cells in normal group and fetal calf serum group, the expressions of NF-κB gene and protein are up-regulated in ox-LDL group(P<0.05, P<0.01); 3) Compared with the cells in ox-LDL group, the expression of NF-κB gene and protein in Tongmai Decoction group are significantly down-regulated, there is no difference between Tongmai Decoction group and simvastatin group(P>0.05). Conclusion Tongmai Decoction can protect the injured endothelial cells, up-regulate the expressions of NF-κB gene and protein content. 相似文献