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   727篇
  免费   35篇
  国内免费   2篇
电工技术   5篇
化学工业   156篇
金属工艺   68篇
机械仪表   15篇
建筑科学   34篇
矿业工程   2篇
能源动力   13篇
轻工业   94篇
石油天然气   2篇
无线电   23篇
一般工业技术   138篇
冶金工业   117篇
自动化技术   97篇
  2023年   6篇
  2022年   27篇
  2021年   31篇
  2020年   23篇
  2019年   25篇
  2018年   32篇
  2017年   16篇
  2016年   31篇
  2015年   13篇
  2014年   29篇
  2013年   49篇
  2012年   27篇
  2011年   50篇
  2010年   45篇
  2009年   34篇
  2008年   36篇
  2007年   29篇
  2006年   13篇
  2005年   17篇
  2004年   21篇
  2003年   19篇
  2002年   9篇
  2001年   10篇
  2000年   9篇
  1999年   12篇
  1998年   12篇
  1997年   11篇
  1996年   8篇
  1995年   4篇
  1994年   8篇
  1993年   11篇
  1992年   4篇
  1990年   4篇
  1989年   6篇
  1988年   5篇
  1987年   5篇
  1986年   5篇
  1985年   9篇
  1984年   4篇
  1982年   3篇
  1981年   3篇
  1980年   5篇
  1979年   3篇
  1978年   4篇
  1977年   3篇
  1976年   3篇
  1973年   3篇
  1971年   5篇
  1969年   3篇
  1943年   3篇
排序方式: 共有764条查询结果,搜索用时 15 毫秒
31.
32.
Nowadays, many manufacturing processes require the machining of complex forms with a high aspect ratio or cavities. Tools with a long overhang length are a common method to meet these requirements. Typical examples for this are boring bars for bore-turning and the milling with very long cutters. These tools tend to vibrate strongly due to their slender shape. The stress-induced transformation of austenite to martensite and the distinctive hysteresis loop allow the NiTi shape memory alloys (SMA) to absorb vibration energy. This article describes the innovative approach to dampen process vibrations by coating the tool shafts of cutting tools with long overhang with NiTi thin films. It explores how these thin films can be applied on polished tungsten carbide shafts and how their modal parameters are modified by these coatings. In a further step, this knowledge is used to calculate stability charts of corresponding machining processes. The study reported in this article identified the stabilizing effects of coatings with a thickness of 2-4 ??m on milling processes. The minimum stability limit was increased by up to 200%.  相似文献   
33.
This paper explores the scale and scope of transformations in the environmental planning field, and the factors that may advance or impede their widespread adoption. A conceptual model is offered which examines scope (defined as type, breadth and structure of the transformation), and the scale of its impact (categorized as stakeholder, organizational, institutional or societal) and applies it to the analysis of several cases in Israel where environmental transformations, affecting the way in which planning is conducted, have been adopted. Conclusions include identification of conditions for facilitating and advancing transformations, including knowledge of innovative alternatives, initiative, willingness to adopt new practices, and identification of policy windows that emerge during conflict, reform, or crisis. The fostering of relations between environmental non-government organizations and planning systems and leadership roles are also significant in catalyzing environmental transformation.  相似文献   
34.
α-Actinin release and its degradation from myofibrils Z-line were studied in post mortem white dorsal muscle from bass and sea trout stored at 4°C and 10°C. Using α-actinin specific antibodies, we show that this protein is rapidly released within the first 24 h for the two species, and reaches a plateau within 4 days. Proteolysis take place very rapidly in bass muscle yielding 80 and 40 kDa fragments from α-actinin as major bands of proteolysis. Sea trout muscle is more resistant, and muscle stored at 4°C is not significantly α-actinin degraded even 10 days after death. In the case of sea trout muscle stored at 10°C, an increasing quantity of 80 and 40 kDa fragment can be observed after the third day. These results show that release and proteolysis of α-actinin are time- and temperature-dependent processes that take place at the early stages of fish storage. Furthermore, we observed that proteolysis of α-actinin seems to be dependent on fish species. In both species studied, the early release of α-actinin comes before the degradation of released molecules, and appears as a biphasic process throughout the disorganisation of post mortem muscle in fish cold-stored above 0°C.  相似文献   
35.
Assessing antioxidant intake requires a food antioxidant database. However, cooking may affect antioxidant content due to antioxidant release, destruction or creation of redox-active metabolites. Here, effects of boiling, steaming and microwaving of broccoli, cauliflower, cabbage and choy-sum (Chinese cabbage) were explored by measuring antioxidant contents of raw and cooked vegetables. Cooking water was also tested. For all cooked vegetables, antioxidant content was highest in steamed > boiled > microwaved, and decreased with longer cooking time, regardless of method. All steamed vegetables had higher antioxidant contents than had matching raw vegetables. Effects were variable for boiling and microwaving. Microwaving caused greater antioxidant loss into cooking water than did boiling. Marked losses of anitoxidants occurred in microwaved cabbage and spinach. To assess food antioxidant content/intake accurately, cooking effects need detailed study. Steaming may be the cooking method of choice to release/conserve antioxidants. The cooking water is a potentially rich source of dietary antioxidants.  相似文献   
36.
The active phase Ce0.5Pr0.5O2 has been loaded on commercial substrates (SiC DPF and cordierite honeycomb monolith) to perform DPF regeneration experiments in the exhaust of a diesel engine. Also, a powder sample has been prepared to carry out soot combustion experiments at laboratory. Experiments performed in the real diesel exhaust demonstrated the catalytic activity of the Ce–Pr mixed oxide for the combustion of soot, lowering the DPF regeneration temperature with regard to a counterpart catalyst-free DPF. The temperature for active regeneration of the Ce0.5Pr0.5O2-containing DPF when the soot content is low is in the range of 500–550 °C. When the Ce0.5Pr0.5O2-containing DPF is saturated with a high amount of soot, pressure drop and soot load at the filter reach equilibrium at around 360 °C under steady state engine operation due to passive regeneration. The uncoated DPF reached this equilibrium at around 440 °C. Comparing results at real exhaust with those at laboratory allow concluding that the Ce0.5Pr0.5O2-catalysed soot combustion in the real exhaust is not based on the NO2-assisted mechanism but is most likely occurring by the active oxygen-based mechanism.  相似文献   
37.
原材料成本推动Autocoro纺纱工艺发展.最近几年纱线生产成本在总成本中的份额不断地在增加.以前纱线生产成本也许占总成本的一半,目前已达75%.介绍了纺纱厂应对这种趋势的方法.  相似文献   
38.
This article is a background report describing a comprehensive study of research in the three computing disciplines Computer Science, Software Engineering, and Information Systems. Findings relate to research topics, approaches, methods, reference disciplines, and levels of analysis. The article informally describes the process used and the research products produced.  相似文献   
39.
In this work, the parameters stress intensity factor (SIF), initial and final crack lengths (a i and a f), crack growth parameters (C and m), and fatigue strength (FAT) are investigated. The determination of initial crack length seems to be the most serious factor in fatigue life and strength calculations for welded joints. A fracture mechanics approach was used in these calculations based on SIF which was calculated with the finite element method (FEM). The weld toe crack was determined to be equal to 0.1 mm, whereas the weld root crack’s length was varied depending on the degree of the weld penetration. These initial crack length values are applicable for all types of joints which have the same crack phenomenon. As based on the above calculated parameters, the new limits of FAT for new geometries which are not listed yet in recommendations can be calculated according to the current approach.  相似文献   
40.

Background  

During the last years engineered nanoparticles (NPs) have been extensively used in different technologies and consequently many questions have arisen about the risk and the impact on human health following exposure to nanoparticles. Nevertheless, at present knowledge about the cytotoxicity induced by NPs is still largely incomplete. In this context, we have investigated the cytotoxicity induced by gold nanoparticles (AuNPs), which differed in size and purification grade (presence or absence of sodium citrate residues on the particle surface) in vitro, in the human alveolar type-II (ATII)-like cell lines A549 and NCIH441.  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