首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2735篇
  免费   229篇
  国内免费   7篇
电工技术   14篇
综合类   2篇
化学工业   772篇
金属工艺   21篇
机械仪表   58篇
建筑科学   136篇
能源动力   56篇
轻工业   582篇
水利工程   36篇
石油天然气   9篇
无线电   141篇
一般工业技术   447篇
冶金工业   348篇
原子能技术   8篇
自动化技术   341篇
  2024年   9篇
  2023年   58篇
  2022年   76篇
  2021年   254篇
  2020年   107篇
  2019年   119篇
  2018年   138篇
  2017年   112篇
  2016年   108篇
  2015年   116篇
  2014年   111篇
  2013年   198篇
  2012年   172篇
  2011年   218篇
  2010年   124篇
  2009年   145篇
  2008年   126篇
  2007年   129篇
  2006年   90篇
  2005年   75篇
  2004年   56篇
  2003年   51篇
  2002年   44篇
  2001年   12篇
  2000年   20篇
  1999年   27篇
  1998年   26篇
  1997年   35篇
  1996年   18篇
  1995年   16篇
  1994年   12篇
  1993年   11篇
  1992年   14篇
  1990年   10篇
  1989年   8篇
  1988年   11篇
  1987年   7篇
  1986年   8篇
  1985年   13篇
  1984年   6篇
  1983年   10篇
  1982年   8篇
  1981年   5篇
  1980年   5篇
  1977年   10篇
  1976年   7篇
  1973年   5篇
  1972年   3篇
  1969年   3篇
  1964年   3篇
排序方式: 共有2971条查询结果,搜索用时 15 毫秒
81.
SmartBone® (SB) is a biohybrid bone substitute advantageously proposed as a class III medical device for bone regeneration in reconstructive surgeries (oral, maxillofacial, orthopedic, and oncology). In the present study, a new strategy to improve SB osteoinductivity was developed. SB scaffolds were loaded with lyosecretome, a freeze-dried formulation of mesenchymal stem cell (MSC)-secretome, containing proteins and extracellular vesicles (EVs). Lyosecretome-loaded SB scaffolds (SBlyo) were prepared using an absorption method. A burst release of proteins and EVs (38% and 50% after 30 min, respectively) was observed, and then proteins were released more slowly with respect to EVs, most likely because they more strongly adsorbed onto the SB surface. In vitro tests were conducted using adipose tissue-derived stromal vascular fraction (SVF) plated on SB or SBlyo. After 14 days, significant cell proliferation improvement was observed on SBlyo with respect to SB, where cells filled the cavities between the native trabeculae. On SB, on the other hand, the process was still present, but tissue formation was less organized at 60 days. On both scaffolds, cells differentiated into osteoblasts and were able to mineralize after 60 days. Nonetheless, SBlyo showed a higher expression of osteoblast markers and a higher quantity of newly formed trabeculae than SB alone. The quantification analysis of the newly formed mineralized tissue and the immunohistochemical studies demonstrated that SBlyo induces bone formation more effectively. This osteoinductive effect is likely due to the osteogenic factors present in the lyosecretome, such as fibronectin, alpha-2-macroglobulin, apolipoprotein A, and TGF-β.  相似文献   
82.
83.
The goal of the study was to obtain spaghetti enriched with pea flour with sensory properties close to conventional pasta. To this aim, the study has been organised in two subsequent trials. In the first, the pea flour amount added to the spaghetti was continuously increased until the overall sensory quality reached its threshold value (pea flour concentration = 15%). In fact, the spaghetti samples supplemented with 15% pea flour (15%S‐P) showed less elasticity, unpleasant colour and higher firmness compared to the control sample (CTRL). The second step was aimed to improve the overall sensory quality of the 15%S‐P spaghetti by means of guar gum (GUAR). The sample with GUAR (15%S‐P/GUAR) showed a pleasant colour, odour and taste. Furthermore, the 15%S‐P/GUAR sample recorded a low starch digestibility value (i.e. 54) and a higher soluble fibre content with respect to the 15%S‐P sample.  相似文献   
84.
Investigation on the behavior of nematic liquid crystals on functionalized polar dielectric crystal substrates is accomplished. Very interesting effects can be observed in maneuvering liquid crystal droplets on the substrate surface, driven by electric fields generated by pyroelectric effect. Reversible drops fragmentation and self‐assembling in different configurations can be achieved. The dynamics of the observed phenomena is studied and the repeatability of the process is full assessed.  相似文献   
85.
86.
An electromechanical switch based on bent carbon nanotubes was fabricated. The shape and structure of the bent carbon nanotubes allows one to produce a low cost and low working voltage switch. The fabrication process is free of any nanolithography. The electrical characteristics of the fabricated device were investigated, both experimentally and theoretically. Actuation of the fabricated device shows hysteresis behavior in the measured IV curves depending on the structural parameters of the bent nanotubes. The relationship between the pull-in voltage and the morphology of the bent nanotubes was studied by the obtained hysteresis curves. A scanning electron microscope was used for structural analysis. This study introduced an easy way to fabricate electromechanical switches with controllable on/off states.  相似文献   
87.
The effect of heat pre-treatment (45 °C/25 min), applied to whole fruit, and post-cut calcium dips in 1 and 2 g/L CaCl2 solutions on respiration rate and texture preservation of kiwifruit slices was studied. During a 9-day period, packages’ atmosphere composition, slices’ firmness, pectin content and sensory scores were evaluated. Histological observations of samples were also performed. Neither heat pre-treatment nor calcium dips alone were effective in diminishing respiration rate of the slices but the application of both treatments revealed a synergistic effect on respiration rate reduction. Calcium-dipped fruit slices showed better firmness preservation. Post-cut calcium dips, alone or combined with heat pre-treatments, yielded slices presenting higher insoluble/total galacturonic acid ratio, indicating formation of calcium pectates. Slices from heat-pre-treated fruits, even in the absence of calcium, also revealed insoluble/total galacturonic acid ratio similar to calcium-treated slices, supporting, despite the lower firmness value, a more structured tissue, as observed in SEM microphotographs. Sensory and physical–chemical parameters obtained were correlated. The effectiveness of calcium treatment was equally observed for both tested concentrations during a 9-day shelf life period.  相似文献   
88.
89.
Bulletin of Engineering Geology and the Environment - The spatial prediction of landslide susceptibility locations is a crucial task to support risk management and development plans in mountainous...  相似文献   
90.
Global demand for mobility is increasing and the environmental impact of transport has become an important issue in transportation network planning and decision-making, as well as in the operational management phase. Suitable methods are required to assess emissions and fuel consumption reduction strategies that seek to improve energy efficiency and furthering decarbonization. This study describes the development and application of an improved modeling framework – the HERA (Highway EneRgy Assessment) methodology – that enables to assess the energy and carbon footprint of different highways and traffic flow scenarios and their comparison. HERA incorporates an average speed consumption model adjusted with a correction factor which takes into account the road gradient. It provides a more comprehensive method for estimating the footprint of particular highway segments under specific traffic conditions. It includes the application of the methodology to the Spanish highway network to validate it. Finally, a case study shows the benefits from using this methodology and how to integrate the objective of carbon footprint reductions into highway design, operation and scenario comparison.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号