全文获取类型
收费全文 | 227747篇 |
免费 | 5213篇 |
国内免费 | 833篇 |
专业分类
电工技术 | 3788篇 |
综合类 | 347篇 |
化学工业 | 37510篇 |
金属工艺 | 8797篇 |
机械仪表 | 6188篇 |
建筑科学 | 6032篇 |
矿业工程 | 1018篇 |
能源动力 | 5954篇 |
轻工业 | 24151篇 |
水利工程 | 2181篇 |
石油天然气 | 3348篇 |
武器工业 | 13篇 |
无线电 | 22745篇 |
一般工业技术 | 41259篇 |
冶金工业 | 44797篇 |
原子能技术 | 4554篇 |
自动化技术 | 21111篇 |
出版年
2022年 | 1499篇 |
2021年 | 2605篇 |
2020年 | 1920篇 |
2019年 | 2411篇 |
2018年 | 3818篇 |
2017年 | 3819篇 |
2016年 | 3965篇 |
2015年 | 2926篇 |
2014年 | 4442篇 |
2013年 | 11159篇 |
2012年 | 7226篇 |
2011年 | 9178篇 |
2010年 | 7217篇 |
2009年 | 7949篇 |
2008年 | 7793篇 |
2007年 | 7653篇 |
2006年 | 6304篇 |
2005年 | 5937篇 |
2004年 | 5753篇 |
2003年 | 5343篇 |
2002年 | 5264篇 |
2001年 | 5060篇 |
2000年 | 4675篇 |
1999年 | 4832篇 |
1998年 | 13887篇 |
1997年 | 9770篇 |
1996年 | 7234篇 |
1995年 | 5272篇 |
1994年 | 4380篇 |
1993年 | 4439篇 |
1992年 | 2947篇 |
1991年 | 2947篇 |
1990年 | 2712篇 |
1989年 | 2735篇 |
1988年 | 2674篇 |
1987年 | 2379篇 |
1986年 | 2311篇 |
1985年 | 2642篇 |
1984年 | 2395篇 |
1983年 | 2165篇 |
1982年 | 2096篇 |
1981年 | 2170篇 |
1980年 | 2012篇 |
1979年 | 1954篇 |
1978年 | 1905篇 |
1977年 | 2469篇 |
1976年 | 3434篇 |
1975年 | 1669篇 |
1974年 | 1626篇 |
1973年 | 1710篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
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
3.
4.
5.
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
6.
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
7.
Moghadam Seyedeh Hadis Ashofteh Parisa-Sadat Loáiciga Hugo A. 《Water Resources Management》2022,36(9):3181-3205
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in... 相似文献
8.
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials. 相似文献
9.
Esperanza González-Redondo 《建筑学研究前沿(英文版)》2022,11(2):255-277
The constructive analysis of Madrid's old timber-framed collective courtyard buildings, whether demolished, preserved intact, or enlarged, has achieved the dating of relevant case studies. New parameters established in this study set a chronology based on front sector original projects: old (1737–1788), pre-modern (1788–1847) and modern (1847–1892). The on-site inspection and archival research point to ongoing misleading construction in the historic Southern area. Some modern corralas erected on top of pre-existing buildings confirm the initial hypothesis. First dimensioning rules for new façades and the stability required in old ones before adding new storeys, maintaining the original masonry or double-layered system, are discovered. Undated buildings suggest their possible origin a la malicia and a later transformation into transitional corralas. Finally, an analysis of the demolished courtyards narrows down the dating and points to new conjectures in some preserved by showing their uneven layout, old features, and structural discordances in each sector. 相似文献
10.
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