全文获取类型
收费全文 | 177523篇 |
免费 | 4392篇 |
国内免费 | 1671篇 |
专业分类
电工技术 | 4540篇 |
技术理论 | 1篇 |
综合类 | 1717篇 |
化学工业 | 28532篇 |
金属工艺 | 7283篇 |
机械仪表 | 6464篇 |
建筑科学 | 6521篇 |
矿业工程 | 1155篇 |
能源动力 | 4691篇 |
轻工业 | 19176篇 |
水利工程 | 1609篇 |
石油天然气 | 1895篇 |
武器工业 | 212篇 |
无线电 | 23354篇 |
一般工业技术 | 32118篇 |
冶金工业 | 24937篇 |
原子能技术 | 2690篇 |
自动化技术 | 16691篇 |
出版年
2022年 | 1284篇 |
2021年 | 1977篇 |
2020年 | 1482篇 |
2019年 | 1589篇 |
2018年 | 1864篇 |
2017年 | 2116篇 |
2016年 | 2111篇 |
2015年 | 2142篇 |
2014年 | 3071篇 |
2013年 | 8137篇 |
2012年 | 4795篇 |
2011年 | 6369篇 |
2010年 | 5068篇 |
2009年 | 5544篇 |
2008年 | 5961篇 |
2007年 | 6140篇 |
2006年 | 5564篇 |
2005年 | 5292篇 |
2004年 | 4741篇 |
2003年 | 4542篇 |
2002年 | 4499篇 |
2001年 | 4461篇 |
2000年 | 4256篇 |
1999年 | 4303篇 |
1998年 | 7210篇 |
1997年 | 5681篇 |
1996年 | 4956篇 |
1995年 | 4116篇 |
1994年 | 3700篇 |
1993年 | 3440篇 |
1992年 | 2986篇 |
1991年 | 2860篇 |
1990年 | 2751篇 |
1989年 | 2714篇 |
1988年 | 2555篇 |
1987年 | 2230篇 |
1986年 | 2159篇 |
1985年 | 2588篇 |
1984年 | 2347篇 |
1983年 | 2209篇 |
1982年 | 2079篇 |
1981年 | 2003篇 |
1980年 | 1870篇 |
1979年 | 1882篇 |
1978年 | 1771篇 |
1977年 | 2086篇 |
1976年 | 2567篇 |
1975年 | 1584篇 |
1974年 | 1430篇 |
1973年 | 1453篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Yan He Kangren Kong Zhengxi Guo Weifeng Fang Zaiqiang Ma Haihua Pan Ruikang Tang Zhaoming Liu 《Advanced functional materials》2021,31(26):2101291
Sensitivity and multi-directional motivation are major two factors for developing optimized humidity-response materials, which are promising for sensing, energy production, etc. Organic functional groups are commonly used as the water sensitive units through hydrogen bond interactions with water molecules in actuators. The multi-coordination ability of inorganic ions implies that the inorganic ionic compounds are potentially superior water sensitive units. However, the particle forms of inorganic ionic compounds produced by classical nucleation limit the number of exposed ions to interact with water. Recent progress on the inorganic ionic oligomers has broken through the limitation of classical nucleation, and realized the molecular-scaled incorporation of inorganic ionic compounds into an organic matrix. Here, the incorporation of hydrophilic calcium carbonate ionic oligomers into hydrophobic poly(vinylidene fluoride) (PVDF) is demonstrated. The ultra-small calcium carbonate oligomers within a PVDF film endow it with an ultra-sensitive, reversible, and bidirectional response. The motivation ability is superior to other bidirectional humidity-actuators at present, which realizes self-motivation on an ice surface, converting the chemical potential energy of the humidity gradient from ice to kinetic energy. 相似文献
12.
Tuladhar Sanira Alsadoon Abeer Prasad P. W. C. Ali Akbas Ezaldeen Alrubaie Ahmad 《Multimedia Tools and Applications》2022,81(17):23845-23865
Multimedia Tools and Applications - Gastrointestinal stromal tumor is one of the critical tumors that doctors do not suggest to get frequent endoscopy, so there is a need for a diagnosis system... 相似文献
13.
Chuntao Lan Haiyang Zou Longfei Wang Meng Zhang Shuang Pan Ying Ma Yiping Qiu Zhong Lin Wang Zhiqun Lin 《Advanced materials (Deerfield Beach, Fla.)》2020,32(47):2005481
Despite recent rapid advances in metal halide perovskites for use in optoelectronics, the fundamental understanding of the electrical-poling-induced ion migration, accounting for many unusual attributes and thus performance in perovskite-based devices, remain comparatively elusive. Herein, the electrical-poling-promoted polarization potential is reported for rendering hybrid organic–inorganic perovskite photodetectors with high photocurrent and fast response time, displaying a tenfold enhancement in the photocurrent and a twofold decrease in the response time after an external electric field poling. First, a robust meniscus-assisted solution-printing strategy is employed to facilitate the oriented perovskite crystals over a large area. Subsequently, the electrical poling invokes the ion migration within perovskite crystals, thus inducing a polarization potential, as substantiated by the surface potential change assessed by Kelvin probe force microscopy. Such electrical-poling-induced polarization potential is responsible for the markedly enhanced photocurrent and largely shortened response time. This work presents new insights into the electrical-poling-triggered ion migration and, in turn, polarization potential as well as into the implication of the latter for optoelectronic devices with greater performance. As such, the utilization of ion-migration-produced polarization potential may represent an important endeavor toward a wide range of high-performance perovskite-based photodetectors, solar cells, transistors, scintillators, etc. 相似文献
14.
15.
16.
C. Doga Demirhan William W. Tso Joseph B. Powell Efstratios N. Pistikopoulos 《American Institute of Chemical Engineers》2019,65(7):e16498
Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas-based reference case. A deterministic global optimization-based branch-and-bound algorithm is used to solve the resulting large-scale nonconvex mixed-integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019 相似文献
17.
Babilas R. Łoński W. Młynarek K. Bajorek A. Radoń A. 《Metallurgical and Materials Transactions A》2020,51(8):4215-4227
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y... 相似文献
18.
Colour remains one of the key factors in presenting an object and, consequently, has been widely applied in retrieval of images based on their visual contents. However, a colour appearance changes with the change of viewing surroundings, the phenomenon that has not been paid attention yet while performing colour‐based image retrieval. To comprehend this effect, in this article, a chromatic contrast model, CAMcc, is developed for the application of retrieval of colour intensive images, cementing the gap that most of existing colour models lack to fill by taking simultaneous colour contrast into account. Subsequently, the model is applied to the retrieval task on a collection of museum wallpapers of colour‐rich images. In comparison with current popular colour models including CIECAM02, HSI and RGB, with respect to both foreground and background colours, CAMcc appears to outperform the others with retrieved results being closer to query images. In addition, CAMcc focuses more on foreground colours, especially by maintaining the balance between both foreground and background colours, while the rest of existing models take on dominant colours that are perceived the most, usually background tones. Significantly, the contribution of the investigation lies in not only the improvement of the accuracy of colour‐based image retrieval but also the development of colour contrast model that warrants an important place in colour and computer vision theory, leading to deciphering the insight of this age‐old topic of chromatic contrast in colour science. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 361–373, 2015 相似文献
19.
核桃雄花中总多酚提取工艺的研究 总被引:2,自引:0,他引:2
采用单因素和正交试验研究核桃雄花中多酚类物质的最佳提取工艺条件。通过对4种不同溶剂(无水乙醇、甲醇、丙酮和乙酸乙酯)在相同试验条件下的浸提效果比较发现,甲醇是核桃雄花中总酚类物质的最佳提取试剂。然后分别采用常规水浴浸提法和超声波辅助浸提法对甲醇体分数、浸提温度、浸提时间和料液比等因素进行研究,在确定最佳单因素水平的基础上,再利用正交试验优化以甲醇为浸提剂的提取工艺条件,试验得出超声波辅助浸提法具有用时短、总多酚提取量高的优点,其最佳工艺条件为:料液比1∶30(g/m L)、甲醇溶液体积分数30%、温度70℃、浸提时间10 min。在此条件下,核桃雄花中的总多酚含量可达6.56%,明显高于其他条件下的。 相似文献
20.