首页 | 官方网站   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   618篇
  免费   37篇
  国内免费   1篇
工业技术   656篇
  2024年   1篇
  2023年   4篇
  2022年   14篇
  2021年   57篇
  2020年   27篇
  2019年   41篇
  2018年   30篇
  2017年   20篇
  2016年   28篇
  2015年   13篇
  2014年   43篇
  2013年   45篇
  2012年   41篇
  2011年   56篇
  2010年   30篇
  2009年   33篇
  2008年   29篇
  2007年   15篇
  2006年   16篇
  2005年   14篇
  2004年   7篇
  2003年   6篇
  2002年   12篇
  2001年   6篇
  2000年   8篇
  1999年   4篇
  1998年   12篇
  1997年   10篇
  1996年   5篇
  1995年   1篇
  1994年   3篇
  1993年   5篇
  1992年   5篇
  1989年   2篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
  1974年   1篇
  1926年   1篇
排序方式: 共有656条查询结果,搜索用时 15 毫秒
71.
We present the application of the shape-from-silhouette technique to reconstruct the three-dimensional profile of ancient handworks from their x-ray absorption images. The acquisition technique is similar to tomography, since the images are taken all around the object while it is rotated. Some reference points are placed on a small and light structure corotating with the object, and are acquired on the images for calibration and registration. The reconstruction algorithm gives finally the three-dimensional appearance of the handwork. We present the analysis of a bronze pendant of VI-VII century B.C. (Venetic area, Italy) completely hidden by corrosion products. The three-dimensional reconstruction shows that the pendant is a very elaborated piece, with two embraced figures that were completely invisible at the excavation.  相似文献   
72.
Norepinephrine (NE) neurons and extracellular NE exert some protective effects against a variety of insults, including methamphetamine (Meth)-induced cell damage. The intimate mechanism of protection remains difficult to be analyzed in vivo. In fact, this may occur directly on target neurons or as the indirect consequence of NE-induced alterations in the activity of trans-synaptic loops. Therefore, to elude neuronal networks, which may contribute to these effects in vivo, the present study investigates whether NE still protects when directly applied to Meth-treated PC12 cells. Meth was selected based on its detrimental effects along various specific brain areas. The study shows that NE directly protects in vitro against Meth-induced cell damage. The present study indicates that such an effect fully depends on the activation of plasma membrane β2-adrenergic receptors (ARs). Evidence indicates that β2-ARs activation restores autophagy, which is impaired by Meth administration. This occurs via restoration of the autophagy flux and, as assessed by ultrastructural morphometry, by preventing the dissipation of microtubule-associated protein 1 light chain 3 (LC3) from autophagy vacuoles to the cytosol, which is produced instead during Meth toxicity. These findings may have an impact in a variety of degenerative conditions characterized by NE deficiency along with autophagy impairment.  相似文献   
73.
BACKGROUND: Salad crops of the Brassicaceae family, such as Diplotaxis tenuifolia and Eruca vesicaria, commonly referred to as ‘rocket salads’, have attracted considerable interest as culinary vegetables because of their strong flavour and their content of putative health‐promoting compounds. Among such compounds, glucosinolates and phenolics are well‐known phytochemicals with an important role also in determining the characteristic flavour of these species. In this study, to identify potentially high‐value rocket salads, 37 cultivated types were examined for sensory characters and their relations with glucosinolate and phenolic contents, which ranged from 0.76 to 3.03 g kg?1 dry weight (DW) and from 4.68 to 31.39 g kg?1 DW, respectively. RESULTS: The perception of bitter taste was significantly affected by specific glucosinolates, namely progoitrin/epiprogoitrin and dimeric glucosativin. Aroma intensity was negatively related to glucoalyssin content, whereas pungency was significantly related to total glucosinolate content. Kaempferol‐3‐(2‐sinapoyl‐glucoside)‐4′‐glucoside was positively and significantly related to all flavour trait perceptions. Aroma intensity, pungency, crunchiness and juiciness were positively related to typical rocket salad flavour perception through a prominent direct effect. CONCLUSION: Aroma intensity, pungency, crunchiness and juiciness were strong determinants of overall rocket salad flavour perception. Visual traits also characterised sensory components. Bitterness, usually considered a negative flavour trait, was moderately perceived in the examined material, without negatively affecting typical flavour perception. In the range of the examined material, glucosinolate content did not contrast with typical flavour, demonstrating that good taste and putative health‐promoting properties may coexist. Copyright © 2011 Society of Chemical Industry  相似文献   
74.
Technology evaluation is part of the decision-making process of any software organization. Unlike conventional wisdom, empirical evaluation strives to avoid biased conclusions by relying on observation and looking for pitfalls in the evaluation process. In this paper, we provide a summary of the maintenance studies presented in the session ‘Study and assessment of (new) technologies’ of the International Workshop on Empirical Studies of Software Maintenance (WESS '96), and also report on the working group discussion which focused on common problems and open issues in the field of technology evaluation. These empirical studies are then classified according to a multi-dimensional framework to synthesize the state of the research in technology evaluation and ultimately discover interesting patterns. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
75.
Saitta  Lorenza  Botta  Marco  Neri  Filippo 《Machine Learning》1993,11(2-3):153-172
This article presents the system WHY, which learns and updates a diagnostic knowledge base using domain knowledge and a set of examples. The a priori knowledge consists of a causal model of the domain that states the relationships among basic phenomena, and a body of phenomenological theory that describes the links between abstract concepts and their possible manifestations in the world. The phenomenological knowledge is used deductively, the causal model is used abductively, and the examples are used inductively. The problems of imperfection and intractability of the theory are handled by allowing the system to make assumptions during its reasoning. In this way, robust knowledge can be learned with limited complexity and a small number of examples. The system works in a first-order logic environment and has been applied in a real domain.  相似文献   
76.
77.
The empirical investigation of Perspective-Based Reading   总被引:6,自引:1,他引:5  
We consider reading techniques a fundamental means of achieving high quality software. Due to the lack of research in this area, we are experimenting with the application and comparison of various reading techniques. This paper deals with our experiences with a family of reading techniques known as Perspective-Based Reading (PBR), and its application to requirements documents. The goal of PBR is to provide operational scenarios where members of a review team read a document from a particular perspective, e.g., tester, developer, user. Our assumption is that the combination of different perspectives provides better coverage of the document, i.e., uncovers a wider range of defects, than the same number of readers using their usual technique.To test the effectiveness of PBR, we conducted a controlled experiment with professional software developers from the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC) Software Engineering Laboratory (SEL). The subjects read two types of documents, one generic in nature and the other from the NASA domain, using two reading techniques, a PBR technique and their usual technique. The results from these experiments, as well as the experimental design, are presented and analyzed. Teams applying PBR are shown to achieve significantly better coverage of documents than teams that do not apply PBR.We thoroughly discuss the threats to validity so that external replications can benefit from the lessons learned and improve the experimental design if the constraints are different from those posed by subjects borrowed from a development organization.  相似文献   
78.
Digital Footprinting: Uncovering Tourists with User-Generated Content   总被引:4,自引:0,他引:4  
Novel methods and tools are being developed to explore the significance of the new types of user-related spatiotemporal data. This approach helps uncover the presence and movements of tourists from cell phone network data and the georeferenced photos they generate.  相似文献   
79.
The role of brown adipose tissue in the mechanism of medium chain triglyceride (MCT)-induced thermogenesis was investigated. Under anesthesia, the interscapular brown adipose tissue (IBAT) was excised in male Sprague-Dawley rats, and the animals were fitted with gastrostomy tubes. After a 10-day recovery period, the animals were divided into two groups: one group received a diet containing MCT as 50% of calories, and the other group received an isocaloric diet containing long chain triglyceride (LCT). The diets were fed for 6 wk at a level of calorie intake that was 150% of the ad libitum intake of a parallel control group. During the last week of the study, resting and norepinephrine (NE)-stimulated O2 consumption and CO2 production were measured in a Noyons diaferometer. At the end of 6 wk, the animals were weighed and killed. The individual fat pads were dissected and weighed, and an aliquot of the right retroperitoneal fat pad was used to measure adipocyte size and number. The results showed that body weight and adipocyte size (but not adipocyte number) were significantly smaller in the MCT-fed compared to the LCT-fed animals. Resting as well as maximal NE-stimulated oxygen consumption values were significantly higher in the MCT-fed than the LCT-fed rats. It is concluded that the enhanced thermogenesis induced by MCT persists despite the absence of IBAT and that the phenomenon is likely related to more extensive oxidation of MCT-in contrast to LCT-derived fatty acids, thus leading to increased oxygen consumption, enhanced dissipation of energy as heat and diminished efficiency of weight gain and deposition of body fat. Presented at the symposium on “Specialty Lipids and Their Biofunctionality” at the annual meeting of the American Oil Chemists' Society, Philadelphia, May 1985.  相似文献   
80.
The use of a general correlation, proposed for organic liquid thermal conductivity λ prediction and checked in the case of organic refrigerant fluids, is extended to inorganic refrigerant fluids whose λ decreases when the reduced temperature, Tr, increases. Suggestions are given for the refrigerants fluids whose λ increases with the reduced temperature.  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-23

京公网安备 11010802026262号