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   835篇
  免费   39篇
  国内免费   1篇
电工技术   6篇
化学工业   217篇
金属工艺   21篇
机械仪表   31篇
建筑科学   32篇
矿业工程   5篇
能源动力   39篇
轻工业   143篇
水利工程   4篇
石油天然气   5篇
无线电   45篇
一般工业技术   119篇
冶金工业   50篇
原子能技术   3篇
自动化技术   155篇
  2024年   3篇
  2023年   9篇
  2022年   29篇
  2021年   29篇
  2020年   26篇
  2019年   22篇
  2018年   30篇
  2017年   34篇
  2016年   34篇
  2015年   21篇
  2014年   43篇
  2013年   67篇
  2012年   63篇
  2011年   67篇
  2010年   36篇
  2009年   37篇
  2008年   51篇
  2007年   38篇
  2006年   32篇
  2005年   25篇
  2004年   18篇
  2003年   20篇
  2002年   12篇
  2001年   5篇
  2000年   4篇
  1999年   4篇
  1998年   8篇
  1997年   8篇
  1996年   3篇
  1995年   11篇
  1994年   8篇
  1993年   5篇
  1992年   4篇
  1991年   5篇
  1990年   5篇
  1989年   3篇
  1988年   5篇
  1986年   4篇
  1985年   3篇
  1984年   3篇
  1983年   7篇
  1981年   7篇
  1980年   5篇
  1979年   3篇
  1978年   5篇
  1976年   4篇
  1974年   3篇
  1971年   1篇
  1958年   1篇
  1955年   2篇
排序方式: 共有875条查询结果,搜索用时 20 毫秒
11.
Autonomous and semi-autonomous mobile robots have to perform a multiplicity of concurrent activities in order to carry out useful tasks in unstructured human-populated environments. Even if it is commonly accepted that a successful accomplishment of assigned tasks requires some sort of real time capability to quickly react and adapt to environmental changes, it is not clear which operating system support is best suited for the scheduling and synchronizing of concurrent activities with different timing requirements. This paper discusses this problem, comparing two different real time scheduling policies for autonomous robot applications: pre-emptive rate monotonic and non pre-emptive Earliest Deadline First (EDF). Experimental results are presented and evaluated.  相似文献   
12.
The pedestrian–structure interaction is considered by developing a non-linear double pendulum model, representing the lateral walking of the pedestrian and the horizontal vibration mode of the structure. To understand the synchronization phenomenon, the two oscillators were considered in their phase spaces, and a ring-dynamics approach was applied. As synchronization occurs, pedestrian motion becomes in phase quadrature with a quarter-of-period in advance of the bridge motion: this ensures stability of walking conditions on a moving deck, but causes random cancellation of forces typical of an incoherent crowd. Correspondingly, the lateral force transmitted to the structure increases its value, approaching resonance conditions.  相似文献   
13.
14.
This paper describes a rigorous and systematic procedure to derive a non-linear distributed FET model that an easily be implemented in CAD routines of simulators based on harmonic balance techniques. The new model is derived from a knowldge of the conventional linear lumped equivalent circuit, from non-linear current sources extracted with pulsed measurements, and from the physical dimensions of the FET. For fundamental and haromonic requencies, the FET is modelled by N identical cells. Each cell is made up of a non-linear two-port section inserted between two linear four-port sections that simulate the coupling and the distributed effects along the electrodes of the FET in the width direction only. This non-linear distributed scaling approach to FET modelling has been applied to the analysis of a submicrometre-gate GaAs FET at Millimetre-wave frequencies, and the results were compared to the non-linear lumped element approach. This approach can be applied to other transistors used in non-linear regions at microwave and millimetre-wave frequencies.  相似文献   
15.
The consumption of brassica sprouts as raw vegetables provides a fair amount of glucosinolates (GLs) and active plant myrosinase, which enables the breakdown of GLs into health-promoting isothiocyanates (ITCs). This study reports the determination of the main constituents related to human health found in edible sprouts of two Brassica oleracea varieties, broccoli and Tuscan black kale, and two Raphanus sativus varieties, Daikon and Sango. Radish sprouts exhibited the highest ability to produce ITCs, with Daikon showing the greatest level of conversion of GLs into bioactive ITCs (96.5%), followed by Sango (90.0%). Tuscan black kale gave a value of 68.5%, whereas broccoli displayed the lowest with 18.7%. ITCs were not the exclusive GL breakdown products in the two B. oleracea varieties, since nitriles were also produced, thus accounting for the lower conversion observed. Measuring the release of plant ITCs is a valuable tool in predicting the potential level of exposure to these bioactive compounds after the consumption of raw brassica sprouts.  相似文献   
16.
A diet based on sunflower cake for lambs was assayed in order to reuse biodiesel industrial by-products with the aim of reducing livestock costs and evaluating their influence on meat quality. To achieve these goals, sixteen male lambs were fed diets containing different levels of sunflower cake (control, 5%, 10% and 15%). Afterwards, their semimembranosus muscles were analysed by two-dimensional electrophoresis coupled to mass spectrometry and their functional protein association was examined using STRING. Structural and metabolic proteins in the lambs’ proteomes changed significantly according to their diet. Fifteen proteins showed significant changes caused by the inclusion of sunflower cake, and the most differentially abundant structural proteins were detected in 2-DE gels from the lambs. Differentially abundant metabolic proteins such as ENO3 (enolase 3), MDH1 (malate dehydrogenase) and ALDH1A1 (retinal dehydrogenase) have been proposed as biomarkers of quality parameters in other species.  相似文献   
17.
Wireless Personal Communications - The increased use of unmanned aerial vehicles (UAVs), better known as drones, by civilians has grown exponentially and their autonomous flight control systems...  相似文献   
18.
19.
Pulsed vacuum osmotic dehydration (PVOD) is a widely used technique for reducing moisture content and water activity in biological products. This study aimed to analyze the effect of vacuum application (VA) on PVOD of beetroot, carrot, and eggplant slices, with respect to chemical (moisture, water activity, specific pigments, polyphenols, and sodium content), optical (color), mechanical (shrinkage, maximum stress, and elasticity), and structural (microstructure) properties. PVOD was conducted at three different vacuum pressures (0, 40, and 80 kPa, for 10 min), during a total process time of 300 min. Osmotic processing was performed at 35 °C by using a ternary osmotic solution [40% sucrose +?10% sodium chloride (w/w)]. Eggplant and carrot samples were more sensitive to VA, compared to beetroot. This was related to their porous and less compact structure. In general, VA reduced the moisture content and water activity and preserved the carotenoid content. VA caused loss of betalain and phenolic acid, favored sodium uptake, and induced significant changes in the optical, mechanical, and structural properties, compared to the osmotic processing conducted at atmospheric pressure.  相似文献   
20.
Giant cell tumour of bone (GCTB) is a benign, locally aggressive primary bone neoplasm that represents 5% of all bone tumours. The principal treatment approach is surgery. Although generally GCTB is considered only a locally aggressive disease, it can metastasise, and lung metastases occur in 1–9% of patients. To date, only the use of denosumab has been approved as medical treatment for GCTB. Even more rarely, GCTB undergoes sarcomatous transformation into a malignant tumour (4% of all GCTB), but history of this malignant transformation is unclear and unpredictable. Considering the rarity of the event, the data in the literature are few. In this review, we summarise published data of GCTB malignant transformation and we analyse three cases of malignant transformation of GCTB, evaluating histopathology, genetics, and radiological aspects. Despite the rarity of this event, we conclude that a strict follow up is recommended to detect early malignant transformation.  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