全文获取类型
收费全文 | 203276篇 |
免费 | 3645篇 |
国内免费 | 810篇 |
专业分类
电工技术 | 3610篇 |
综合类 | 331篇 |
化学工业 | 32784篇 |
金属工艺 | 8334篇 |
机械仪表 | 5724篇 |
建筑科学 | 5376篇 |
矿业工程 | 968篇 |
能源动力 | 5569篇 |
轻工业 | 20187篇 |
水利工程 | 1942篇 |
石油天然气 | 3265篇 |
武器工业 | 8篇 |
无线电 | 21884篇 |
一般工业技术 | 37075篇 |
冶金工业 | 38617篇 |
原子能技术 | 4472篇 |
自动化技术 | 17585篇 |
出版年
2021年 | 2074篇 |
2020年 | 1436篇 |
2019年 | 1864篇 |
2018年 | 2787篇 |
2017年 | 2869篇 |
2016年 | 2919篇 |
2015年 | 2144篇 |
2014年 | 3570篇 |
2013年 | 9219篇 |
2012年 | 5814篇 |
2011年 | 7936篇 |
2010年 | 6203篇 |
2009年 | 7084篇 |
2008年 | 6925篇 |
2007年 | 6747篇 |
2006年 | 5742篇 |
2005年 | 5447篇 |
2004年 | 5285篇 |
2003年 | 4917篇 |
2002年 | 4841篇 |
2001年 | 4753篇 |
2000年 | 4386篇 |
1999年 | 4504篇 |
1998年 | 12141篇 |
1997年 | 8548篇 |
1996年 | 6453篇 |
1995年 | 4814篇 |
1994年 | 4024篇 |
1993年 | 4021篇 |
1992年 | 2792篇 |
1991年 | 2779篇 |
1990年 | 2601篇 |
1989年 | 2605篇 |
1988年 | 2547篇 |
1987年 | 2261篇 |
1986年 | 2214篇 |
1985年 | 2533篇 |
1984年 | 2294篇 |
1983年 | 2084篇 |
1982年 | 1983篇 |
1981年 | 2048篇 |
1980年 | 1883篇 |
1979年 | 1891篇 |
1978年 | 1838篇 |
1977年 | 2221篇 |
1976年 | 2890篇 |
1975年 | 1626篇 |
1974年 | 1583篇 |
1973年 | 1651篇 |
1972年 | 1372篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Bernette Maria Oosterlaken Heiner Friedrich Gijsbertus de With 《Microscopy research and technique》2022,85(1):412-417
Transmission electron microscopy (TEM) is an important analysis technique to visualize (bio)macromolecules and their assemblies, including collagen fibers. Many protocols for TEM sample preparation of collagen involve one or more washing steps to remove excess salts from the dispersion that could hamper analysis when dried on a TEM grid. Such protocols are not standardized and washing times as well as washing solvents vary from procedure to procedure, with each research group typically having their own protocol. Here, we investigate the influence of washing with water, ethanol, but also methanol and 2-propanol, for both mineralized and unmineralized collagen samples via a protocol based on centrifugation. Washing with water maintains the hydrated collagen structure and the characteristic banding pattern can be clearly observed. Conversely, washing with ethanol results in dehydration of the fibrils, often leading to aggregation of the fibers and a less obvious banding pattern, already within 1 min of ethanol exposure. As we show, this process is fully reversible. Similar observations were made for methanol and propanol. Based on these results, a standardized washing protocol for collagenous samples is proposed. 相似文献
2.
3.
4.
F.T. Munna Vidhya Selvanathan K. Sobayel Ghulam Muhammad Nilofar Asim Nowshad Amin Kamaruzzaman Sopian Md. Akhtaruzzaman 《Ceramics International》2021,47(8):11003-11009
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell. 相似文献
5.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
6.
Kravchenko V. F. Konovalov Ya. Yu. 《Journal of Communications Technology and Electronics》2022,67(8):952-964
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically... 相似文献
7.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
8.
Gabriela Pitolli Lyra Valdemir Santos Eliria Maria de Jesus Agnolon Pallone Ruth Herta Goldschmidt Aliaga Kiminami Bruno Carlos De Santis João Adriano Rossignolo 《International Journal of Applied Ceramic Technology》2021,18(3):705-715
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C. 相似文献
9.
Reliable joints of Ti3SiC2 ceramic and TC11 alloy were diffusion bonded with a 50 μm thick Cu interlayer. The typical interfacial structure of the diffusion boned joint, which was dependent on the interdiffusion and chemical reactions between Al, Si and Ti atoms from the base materials and Cu interlayer, was TC11/α-Ti + β-Ti + Ti2Cu + TiCu/Ti5Si4 + TiSiCu/Cu(s, s)/Ti3SiC2. The influence of bonding temperature and time on the interfacial structure and mechanical properties of Ti3SiC2/Cu/TC11 joint was analyzed. With the increase of bonding temperature and time, the joint shear strength was gradually increased due to enhanced atomic diffusion. However, the thickness of Ti5Si4 and TiSiCu layers with high microhardness increased for a long holding time, resulting in the reduction of bonding strength. The maximum shear strength of 251 ± 6 MPa was obtained for the joint diffusion bonded at 850 °C for 60 min, and fracture primarily occurred at the diffusion layer adjacent to the Ti3SiC2 substrate. This work provided an economical and convenient solution for broadening the engineering application of Ti3SiC2 ceramic. 相似文献
10.
Khammatova V. V. Gainutdinov R. F. Khammatova E. A. Titova L. V. 《Fibre Chemistry》2021,53(3):204-207
Fibre Chemistry - An analysis of the aramid fiber market including the range of industrial textile materials containing chemical fibers for specialized protective clothing of metallurgical workers,... 相似文献