全文获取类型
收费全文 | 842篇 |
免费 | 65篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 216篇 |
金属工艺 | 15篇 |
机械仪表 | 9篇 |
建筑科学 | 30篇 |
矿业工程 | 3篇 |
能源动力 | 21篇 |
轻工业 | 183篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
无线电 | 38篇 |
一般工业技术 | 122篇 |
冶金工业 | 117篇 |
原子能技术 | 4篇 |
自动化技术 | 135篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 13篇 |
2021年 | 47篇 |
2020年 | 26篇 |
2019年 | 32篇 |
2018年 | 27篇 |
2017年 | 30篇 |
2016年 | 25篇 |
2015年 | 33篇 |
2014年 | 44篇 |
2013年 | 76篇 |
2012年 | 57篇 |
2011年 | 66篇 |
2010年 | 46篇 |
2009年 | 50篇 |
2008年 | 38篇 |
2007年 | 33篇 |
2006年 | 30篇 |
2005年 | 23篇 |
2004年 | 27篇 |
2003年 | 28篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1960年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有910条查询结果,搜索用时 15 毫秒
1.
2.
Water-deficit stresses such as drought and salinity are the most important factors limiting crop productivity. Hence, understanding the plant responses to these stresses is key for the improvement of their tolerance and yield. In this study M. truncatula plants were subjected to 250 mM NaCl as well as reduced irrigation (No-W) and 250 g/L polyethylene glycol (PEG)-6000 to induce salinity and drought stress, respectively, provoking a drop to −1.7 MPa in leaf water potential. The whole plant physiology and metabolism was explored by characterizing the stress responses at root, phloem sap and leaf organ level. PEG treatment led to some typical responses of plants to drought stress, but in addition to PEG uptake, an important impairment of nutrient uptake and a different regulation of carbon metabolism could be observed compared to No-W plants. No-W plants showed an important redistribution of antioxidants and assimilates to the root tissue, with a distinctive increase in root proline degradation and alkaline invertase activity. On the contrary, salinity provoked an increase in leaf starch and isocitrate dehydrogenase activity, suggesting key roles in the plant response to this stress. Overall, results suggest higher protection of salt-stressed shoots and non-irrigated roots through different mechanisms, including the regulation of proline and carbon metabolism, while discarding PEG as safe mimicker of drought. This raises the need to understand the effect at the whole plant level of the different strategies employed to apply water-deficit stress. 相似文献
3.
4.
正趁着春节假期,我到台北和高雄看望久别的姐妹们。虽是第一次来到宝岛,不过吃住都是在姐妹家中,这趟旅行倒像是回家一样,没什么违和感与陌生感,然而小新鲜却总是不断。刚下飞机时,看到几乎人人戴口罩,这吓了我一跳,其实那里空气真不错,没遇到过雾霾天。这是怎么回事呢? 相似文献
5.
正尽管中国足球无缘本届俄罗斯世界杯,但"中国制造"和"中国品牌"已令人侧目、笑傲全球。中国企业为本届世界杯的赛事经济贡献巨大,这对谋求重塑声誉的国际足联(FIFA)来说,无异于雪中送炭;对中国企业而言,期望通过世界杯的聚集效应放大自身的品牌价值,借势在商业征途上纵横四海,并将"足球梦""复兴梦"与"中国梦""实业梦"的雄心壮志结合得更为实际。2010年,"瓦瓦祖拉"的塑料喇叭响彻南非,"普天同庆"的官方用球和国旗、假发、墨镜、望远 相似文献
6.
Dipta Mukherjee Arjun Dey A. Carmel Mary Esther Debajyoti Palai N. Sridhara Parthasarathi Bera Manjima Bhattacharya A. Rajendra Anand Kumar Sharma Anoop Kumar Mukhopadhyay 《Ceramics International》2018,44(8):8913-8921
Smooth, uniform and crystalline vanadium oxide thin films were deposited on quartz by spin coating technique with four different rpm i.e., 1000, 2000, 3000 and 4000 and subsequently post annealed at 350, 450 and 550?°C in vacuum. Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were utilized for microstructural characterizations and phase analysis, respectively, for vanadium oxide powder and deposited film. Nanorods were observed to be grown after vacuum annealing. X-ray photoelectron spectroscopy (XPS) technique was utilized to study the elemental oxidation state of deposited vanadium oxide films. Thermo-optical and electrical properties such as solar transmittance (τs), reflectance (ρs), absorptance (αs), infrared (IR) emittance (εir) and sheet resistance (Rs) of different thin films were evaluated. Based on the optical characteristics the optimized condition of the film processing was identified to be spin coated at 3000?rpm. Subsequently, the nanoindentation technique was utilized to measure hardness and Young's modulus of the optimized film. The measured nanomechanical properties were found to be superior to those reported for sputtered vanadium oxide films. Finally, temperature dependent phase transition characteristics of optimized vanadium oxide films were studied by differential scanning calorimetry (DSC) technique. Reversible and repeatable phase transition was found to occur in the range of 44–48?°C which was significantly lower than the phase transition temperature (i.e., 68?°C) of bulk VO2. 相似文献
7.
Gil Costa Machado Esther García-Tuñón Robert V. Bell Mauro Alini Eduardo Saiz Marianna Peroglio 《Journal of the European Ceramic Society》2018,38(3):949-961
Calcium phosphates (CaP) have been the subject of several studies that often lack a systematic approach to understanding how their properties affect biological response. CaP particles functionalised with a pH-responsive polymer (BCS) were used to prepare microporous substrates (porosity between 70 and 75% and pore sizes of 5–20 μm) through the aggregation of oil-in-water emulsions by controlling solid loading, emulsification energy, pH, drying and sintering conditions. The combined effect of surface roughness (roughness amplitude, Ra between 0.9–1.7 μm) and chemistry (varying Hydroxyapatite/β-Tricalcium phosphate ratio) on human mesenchymal stem cells was evaluated. HA substrates stimulated higher cell adhesion and proliferation (especially with lower Ra), but cell area increased with β-TCP content. The effect of surface roughness depended of chemistry: HA promoted higher mineralising activity when Ra ~ 1.5 μm, whereas β-TCP substrates stimulated a more osteogenic profile when Ra ~ 1.7 μm. A novel templating method to fabricate microporous CaP substrates was developed, opening possibilities for bone substitutes with controlled features. 相似文献
8.
9.
10.