全文获取类型
收费全文 | 6987篇 |
免费 | 74篇 |
国内免费 | 421篇 |
学科分类
工业技术 | 7482篇 |
出版年
2024年 | 6篇 |
2023年 | 75篇 |
2022年 | 115篇 |
2021年 | 166篇 |
2020年 | 107篇 |
2019年 | 142篇 |
2018年 | 151篇 |
2017年 | 142篇 |
2016年 | 131篇 |
2015年 | 179篇 |
2014年 | 346篇 |
2013年 | 464篇 |
2012年 | 278篇 |
2011年 | 541篇 |
2010年 | 431篇 |
2009年 | 438篇 |
2008年 | 494篇 |
2007年 | 519篇 |
2006年 | 413篇 |
2005年 | 329篇 |
2004年 | 307篇 |
2003年 | 286篇 |
2002年 | 277篇 |
2001年 | 188篇 |
2000年 | 192篇 |
1999年 | 147篇 |
1998年 | 157篇 |
1997年 | 119篇 |
1996年 | 105篇 |
1995年 | 74篇 |
1994年 | 54篇 |
1993年 | 31篇 |
1992年 | 22篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有7482条查询结果,搜索用时 62 毫秒
91.
92.
The conversion coating can be obtained by using a solution containing titanium tetrachloride, fluorosilicate acid and nitric acid. The results of X-ray photoelectron spectroscopy (XPS) showed that the titanium conversion coating consisted of ZnO, TiO2 and Zn4Si2O7(OH)2. The formation process of the titanium conversion coating was studied. Effects of the immersion time, pH value and solution temperature on the corrosion resistance and the chemical composition of the titanium conversion coating were investigated by the salt spray test (SST) and XPS, respectively. The results of XPS and SST showed that the titanium conversion coating displayed better corrosion resistance with higher contents of Si and Ti. Results of corrosion tests (the salt spray and electrochemical test) indicate that the corrosion resistance of the conversion coating by titanium solution is better than that of the conversion coating using the traditional chromate solution. 相似文献
93.
94.
CrSiN coatings with different Si concentration (Si/(Cr + Si) ratio: 0, 3.7, 11.7, 20%) were deposited on stainless steel substrates using a closed field unbalanced magnetron sputtering (CFUBM) system. The variation in the microstructure of the films with the Si concentration was measured by XRD. The corrosion behavior of the CrSiN coatings in a deaerated 3.5% NaCl solution was investigated by potentiodynamic tests, electrochemical impedance spectroscopy (EIS) and surface analyses. The microstructure of the CrSiN film was found to depend on the Si concentration. The results of the potentiodynamic polarization tests showed that the corrosion current density and porosity decreased with increasing Si/(Cr + Si) ratio. The EIS measurements showed that the corrosion resistance of the Si-bearing CrN was improved by the phase transformation of the film, which led to an increase in the pore resistance and charge transfer resistance. The Si-bearing CrN possesses the best corrosion resistance at a Si/(Cr + Si) ratio of 20%, measured by the maximization of the pore resistance and charge transfer resistance. 相似文献
95.
96.
航空发动机滑油系统镁合金微生物腐蚀与防护 总被引:4,自引:1,他引:4
针对航空发动机滑油系统镁合金部件的工作环境特点,结合外场出现的滑油系统故障分析和返厂大修某发动机统计资料,发现微生物是引起其腐蚀的主要原因。同时,提出一些防护措施。 相似文献
97.
Ti-24Al-11Nb腐蚀疲劳断口形貌的研究张跃,褚武扬,王燕斌,肖纪美(北京科技大学北京100083)1引言对Ti-24AI-11Nb合金的断裂特征和断口形貌已进行了较多的研究[“].在300oC的氢气中该合金能发生氢致开裂,其断口形貌与过载断口... 相似文献
98.
R.E. Melchers 《Corrosion Science》2003,45(10):2307-2323
The non-linear phenomenological model previously proposed for the ‘general’ corrosion loss of mild and low alloy steels under fully aerated ‘at-sea’ near-surface immersion conditions is applied to provide a new interpretation of literature data for copper-bearing steels. The data is examined to extract the parameters required for the model as a function of average seawater temperature. On the basis of the expectation of consistency, the data is then used to calibrate the parameters. All are generally consistent with the parameters derived earlier for mild and low alloy steels. The calibrated parameters are used to predict a consolidated plot of expected corrosion loss-time-temperature for copper-bearing steels. This compares favourably with a similar plot derived earlier from observed data alone. 相似文献
99.
Pipelines and heat exchangers using seawater as coolant suffer from biofouling. Biofouling not only reduces heat transfer performance significantly, but also causes considerable pressure drop, calling for higher pumping requirements. It would be much more desirable if surfaces with an inherently lower stickability for biofouling could be developed. In this paper, a cost-effective autocatalytic graded Ni-Cu-P-PTFE composite coating with corrosion-resistant properties was applied to reduce biofouling formation. The experimental results showed that the surface free energy of the Ni-Cu-P-PTFE coatings, which were altered by changing the PTFE content in the coatings, had a significant influence on the adhesion of microbial and mineral deposits. The Ni-Cu-P-PTFE coatings with defined surface free energy reduced the adhesion of these deposits significantly. The anti-bacterial mechanism of the composite coatings was explained with the extended DLVO theory. 相似文献
100.
针对尿素合成塔的腐蚀问题,详细介绍了从投产使用到现在该设备的腐蚀现状.并从不同角度进行详细分析,提出了解决问题的办法及日常运行中应注意的问题. 相似文献