全文获取类型
收费全文 | 6341篇 |
免费 | 618篇 |
国内免费 | 216篇 |
专业分类
电工技术 | 307篇 |
综合类 | 340篇 |
化学工业 | 1046篇 |
金属工艺 | 371篇 |
机械仪表 | 398篇 |
建筑科学 | 375篇 |
矿业工程 | 140篇 |
能源动力 | 182篇 |
轻工业 | 646篇 |
水利工程 | 104篇 |
石油天然气 | 153篇 |
武器工业 | 22篇 |
无线电 | 782篇 |
一般工业技术 | 903篇 |
冶金工业 | 447篇 |
原子能技术 | 82篇 |
自动化技术 | 877篇 |
出版年
2024年 | 11篇 |
2023年 | 108篇 |
2022年 | 191篇 |
2021年 | 281篇 |
2020年 | 220篇 |
2019年 | 155篇 |
2018年 | 202篇 |
2017年 | 191篇 |
2016年 | 215篇 |
2015年 | 257篇 |
2014年 | 349篇 |
2013年 | 449篇 |
2012年 | 448篇 |
2011年 | 470篇 |
2010年 | 347篇 |
2009年 | 382篇 |
2008年 | 354篇 |
2007年 | 303篇 |
2006年 | 308篇 |
2005年 | 241篇 |
2004年 | 162篇 |
2003年 | 194篇 |
2002年 | 190篇 |
2001年 | 150篇 |
2000年 | 101篇 |
1999年 | 106篇 |
1998年 | 143篇 |
1997年 | 87篇 |
1996年 | 80篇 |
1995年 | 87篇 |
1994年 | 52篇 |
1993年 | 52篇 |
1992年 | 36篇 |
1991年 | 30篇 |
1990年 | 30篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1977年 | 11篇 |
1976年 | 17篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1969年 | 5篇 |
排序方式: 共有7175条查询结果,搜索用时 15 毫秒
1.
采用溶胶-凝胶法制备CuO-SiO2复合气凝胶,通过在气凝胶孔道内填充TiCl4,然后将其气相水解,得到了在CuO-SiO2气凝胶表面生长了高结晶度的TiO2纳米纤维(CuO-SiO2@TiO2),纤维直径~16 nm.通过XPS、UPS、UV-Vis DRS、荧光光谱(PL)等表征了材料的结构及光电性能.结果表明,制备的CuO-SiO2@TiO2对可见光有明显吸收,且荧光强度较商用TiO2(P25)大幅降低,光生电子-空穴对更加稳定.再在纳米纤维上负载CuO,所得CuO-SiO2@TiO2/CuO在可见光区的荧光强度进一步增强.以300 W氙灯为光源,分别以CuO-SiO2@TiO2及CuO-SiO2@TiO2/CuO为催化剂,无牺牲剂条件下光催化还原CO2,4 h后甲醇产率分别为1304.0及1589.0μmol/g-cat,转换频率(TOF)分别为0.038及0.046 h–1.循环实验表明,纳米纤维具有较好的光催化稳定性,经过4次光催化循环实验后,CuO-SiO2@TiO2/CuO的保留率~94%,甲醇产率可达1472.0μmol/g-cat,TOF为0.042 h–1. 相似文献
2.
3.
Zhang Nan Zhao Man Liu Guangfa Wang Jiaoyang Chen Yunzhi Zhang Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then... 相似文献
4.
Understanding the phase transition behavior of the rhombohedral phase (R) and tetragonal phase (T) of the relaxor ferroelectric PMN–PT single crystals under mechanical load is essential for the potential voltage-free controlled ferroelectric-based nanodevices. Relaxor ferroelectric single crystals PMN–PT, under a local inhomogeneous mechanical load, were studied experimentally by the nanoindentation tests and Raman spectroscopy measurements. The observations show that the rhombohedral phase can be transformed successfully to the tetragonal phase under a mechanical stress, and the tetragonal phase in the PMN–PT single crystals presents a structural stability. The phase transition induced by the mechanical stress with different strain rates further indicates that the relaxor ferroelectric single crystals possess a potential mechanical controllability. The present study reveals the phase transition pathway of the relaxor ferroelectric single crystal under inhomogeneous stress and provides the exciting possibility of the control of mechanically induced phase transition for ferroelectrics. 相似文献
5.
Chenchen Zhou Jia Man Haibo Yu He Xia Luming Man Bin Qi Jianfeng Li 《Ceramics International》2021,47(8):10866-10872
Ceramic microparticles have great potentials in various fields such as materials engineering, biotechnology, microelectromechanical systems, etc. Morphology of the microparticle performs an important role on their application. To date, it remains difficult to find an effective and controllable way for fabricating nonspherical ceramic microparticles with 3D features. This work demonstrates a method that combines UV light lithography and single emulsion opaque-droplet-templated microfluidic molding to prepare the crescent-shaped ceramic microparticles. By tailoring the intensity of UV light and flow rate of fluid, the shapes of microparticles are accordingly tuned. Therefore, varieties of crescent-shaped microparticles and their variations have been fabricated. After sintering, the crescent-shaped alumina ceramic microparticles were obtained. Benefitting from the light absorption and scattering behavior of most ceramic nanoparticles, this system can serve as a general platform to produce crescent-shaped microparticles made from different materials, and hold great potentials for applications in microrobotics, structural materials in MEMS, and biotechnology. 相似文献
6.
目的 检测水产品及养殖水中丁香酚类化合物。方法 应用食品补充检验方法BJS 201908《水产品及水中丁香酚类化合物的测定》,以海水鱼、淡水鱼、海水虾、淡水虾及养殖水作为基质,测定6种丁香酚类化合物的含量。结果 通过对实际样品测定后发现,在水产品中检出了丁香酚类化合物,主要为丁香酚,检出率为28.9%,其中海水鱼相对突出。结论 本研究为丁香酚作为渔用麻醉剂提供了方法论,为丁香酚类化合物在水产运输的合理使用提供理论依据。 相似文献
7.
8.
Jia-Wun Li Yung-Hsin Cheng Hsun-Tsing Lee Chyung-Chyung Wang Chih-Wei Chiu Maw-Cherng Suen 《应用聚合物科学杂志》2020,137(36):49062
This study successfully incorporated a short-segment fluorine-containing chain extender (2,2,3,3-tetrafluoro-1,4-butanediol [TF]) into castor oil-based polyurethane (COPU) to synthesize TF/COPUs. The interactions between TF and COPU components were identified by Fourier transform infrared and X-ray photoelectron spectroscopies, the results revealed that the increase in the TF content increased the van der Waals forces in C F…CO and the hydrogen bonding force in C F…H N. Atomic force microscopy indicated that the addition of more TF contributed to a higher level of microphase separation in the TF/COPUs. Thermogravimetric analysis showed that the TF component can enhance the thermal resistance of TF/COPUs. Differential scanning calorimetry and dynamic mechanical analysis indicated that the glass transition temperature (Tg) of TF/COPUs increased with the TF content. The stress–strain testing showed that the tensile strength and elongation at break values decreased with the TF content. This tensile behavior may be due to the molecular weight of a TF/COPU decreased with the TF content as evidenced by the gel permeation chromatography results. The hydrolytic degradation tests of dipping TF/COPUs in 3 wt% NaOH solution indicated that TF could lower the surface free energy and enhance the degradation stability of TF/COPUs. 相似文献
9.
10.