全文获取类型
收费全文 | 28358篇 |
免费 | 3082篇 |
国内免费 | 1020篇 |
学科分类
工业技术 | 32460篇 |
出版年
2024年 | 137篇 |
2023年 | 469篇 |
2022年 | 724篇 |
2021年 | 932篇 |
2020年 | 1046篇 |
2019年 | 896篇 |
2018年 | 923篇 |
2017年 | 1090篇 |
2016年 | 1013篇 |
2015年 | 1134篇 |
2014年 | 1652篇 |
2013年 | 1874篇 |
2012年 | 1827篇 |
2011年 | 2337篇 |
2010年 | 1783篇 |
2009年 | 1855篇 |
2008年 | 1474篇 |
2007年 | 1808篇 |
2006年 | 1848篇 |
2005年 | 1486篇 |
2004年 | 1244篇 |
2003年 | 1033篇 |
2002年 | 746篇 |
2001年 | 552篇 |
2000年 | 438篇 |
1999年 | 371篇 |
1998年 | 338篇 |
1997年 | 240篇 |
1996年 | 228篇 |
1995年 | 159篇 |
1994年 | 154篇 |
1993年 | 97篇 |
1992年 | 100篇 |
1991年 | 73篇 |
1990年 | 73篇 |
1989年 | 58篇 |
1988年 | 32篇 |
1987年 | 28篇 |
1986年 | 28篇 |
1985年 | 23篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 2篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1959年 | 4篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
We demonstrate that alkali-halide salts, particularly potassium bromide, can reduce the photothermal emission (PTE) from single walled carbon nanotubes (SWNT). PTE is a prominent spectral feature in Raman spectroscopy when a near infrared laser is used to analyze a dark colored sample. We subsequently show that trapping salts inside SWNT and coating SWNT with the salt has a more pronounced impact on not only reducing PTE, but also enhancing the intensity of the Raman spectral features. The effect, which we have called nanotube enhanced Raman spectroscopy (NERS), has differences and similarities to the widely studied surface enhanced Raman spectroscopy (SERS). 相似文献
2.
3.
1 INTRODUCTIONParticlesreinforcedtitaniumalloymatrixcomposites(TMCp)havewideapplicationfieldsfortheirattractivehighspecificstreng 相似文献
4.
对菱镁矿在固体燃料燃烧过程中的固硫特性进行了理论研究,所得结论对进一步将菱镁矿作为固体燃料燃烧过程中的固硫剂具有非常重要的意义。 相似文献
5.
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
6.
The Synthesis of Sulfated Titanium Oxide Nanotubes 总被引:1,自引:0,他引:1
Chiu-Hsun Lin Shu-Hua Chien Jiunn-Hsing Chao Chyi-Yang Sheu Yu-Cheng Cheng Ya-Jean Huang Chih-Hsiang Tsai 《Catalysis Letters》2002,80(3-4):153-159
TiO2 nanotubes can be prepared in gram quantities by treating anatase TiO2 powder with concentrated NaOH solution. These TiO2 nanotubes acquired strong acidity after being impregnated with sulfuric acid solution and calcined at 300 °C. The anatase TiO2 powder used to prepare the nanotube did not catalyze the esterification between cyclohexanol and acetic acid, while sulfated TiO2 nanotubes were very reactive toward the esterification reaction. 相似文献
7.
8.
10.
Titanium Dioxide, TiO2, is a photocatalyst with a unique characteristic. A surface coated with TiO2 exhibits an extremely high affinity for water when exposed to UV light and the contact angle decreases nearly to zero. Inversely, the contact angle increases when the surface is shielded from UV. This superhydrophilic nature gives a self-cleaning effect to the coated surface and has already been applied to some construction materials, car coatings and so on. We applied this property to the enhancement of boiling heat transfer. An experiment involving the pool boiling of pure water has been performed to make clear the effect of high wettability on heat transfer characteristics. The heat transfer surface is a vertical copper cylinder of 17 mm in diameter and the measurement has been done at saturated temperature and in a steady state. Both TiO2-coated and non-coated surfaces were used for comparison. In the case of the TiO2-coated surface, it is exposed to UV light for a few hours before experiment and it is found that the maximum heat flux (CHF) is about two times larger than that of the uncoated surface. The temperature at minimum heat flux (MHF) for the superhydrophilic surface is higher by 100 K than that for the normal one. The superhydrophilic surface can be an ideal heat transfer surface. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献