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   2661篇
  免费   213篇
  国内免费   11篇
电工技术   39篇
综合类   18篇
化学工业   526篇
金属工艺   56篇
机械仪表   59篇
建筑科学   153篇
矿业工程   8篇
能源动力   81篇
轻工业   186篇
水利工程   28篇
石油天然气   28篇
无线电   322篇
一般工业技术   546篇
冶金工业   241篇
原子能技术   8篇
自动化技术   586篇
  2023年   40篇
  2022年   57篇
  2021年   108篇
  2020年   79篇
  2019年   88篇
  2018年   98篇
  2017年   85篇
  2016年   107篇
  2015年   96篇
  2014年   115篇
  2013年   207篇
  2012年   136篇
  2011年   231篇
  2010年   144篇
  2009年   159篇
  2008年   160篇
  2007年   164篇
  2006年   123篇
  2005年   89篇
  2004年   53篇
  2003年   53篇
  2002年   43篇
  2001年   40篇
  2000年   36篇
  1999年   25篇
  1998年   31篇
  1997年   27篇
  1996年   22篇
  1995年   22篇
  1994年   26篇
  1993年   9篇
  1992年   18篇
  1991年   7篇
  1990年   12篇
  1989年   13篇
  1988年   9篇
  1987年   11篇
  1986年   6篇
  1985年   13篇
  1984年   8篇
  1983年   11篇
  1982年   13篇
  1981年   7篇
  1979年   9篇
  1977年   8篇
  1976年   5篇
  1975年   8篇
  1974年   13篇
  1973年   5篇
  1969年   5篇
排序方式: 共有2885条查询结果,搜索用时 281 毫秒
101.
102.
Vegetable oils are now considered to be a potential alternative that can be used in place of partial or total substitution of diesel fuels. In this study, we used diethyl ether as an oxygenated additive to investigate the possible use of higher percentages of biodiesel in an unmodified diesel engine. Neem oil was selected for biodiesel production. The tests were performed at a steady-state condition in a single-cylinder constant speed DI diesel engine. The combustion process involved in diesel engine would be improved and the particulate matter would be reduced if these biodiesels are blended. An experimental investigation is carried out to establish the emission characteristics of a direct injection diesel engine using diethyl ether as additive in Neat Neem oil Biodiesel. Emissions of hydro carbon oxides of nitrogen and carbon monoxide significantly reduced by adding diethyl ether into neem oil biodiesel at 10% and 20% on volume basis.  相似文献   
103.
Advanced Time Series InSAR (ATS-InSAR) generally refers to those TS-InSAR methods with an external distributed scatterer selection module, e.g. SqueeSAR?, and GEOS-ATSA (Advanced Time-Series Analysis). It is being known as a very efficient tool for monitoring ground deformation over suburban or non-urban regions with great success. However, research conducted using C-band Envisat-based ATS-InSAR failed to produce reasonable outcome within Appin Colliery primarily due to the underground mining effect, which is located in the southeastern corner of the Southern Coalfield, New South Wales, Australia; thus, the general underground mining pattern cannot be formed. This work presents a modified ATS-InSAR method for mapping the ground deformation over underground mining region. More specifically, in order to achieve the best outcome, a modified measurement scatterer (MS) pixel selection method is introduced by including less reliable MS pixels through an Inverse Distance Weighted-based integration method. In addition, the proposed method is also applied to C-band Sentinel-1 image stacks for testing purpose, and the final result proved to be efficient to offer sufficient information to the mining industry and government for risk management purpose.  相似文献   
104.
The effects and interactions of heating temperature (60 °C to 73.9 °C), salt (0.0 % to 4.5 %?w/v), sodium pyrophosphate (0.0 % to 0.5 %?w/v), and sodium lactate (0.0 % to 4.5 %?w/v) on the heat resistance of a five-strain mixture of Listeria monocytogenes in 75 % lean ground beef were examined. Meat samples in sterile filtered stomacher bags were heated in a temperature controlled waterbath to determine thermal death times. The recovery medium was tryptic soy agar supplemented with 0.6 % yeast extract and 1 % sodium pyruvate. Weibull survival functions were employed to model the primary survival curves. Then, survival curve-specific estimated parameter values obtained from the Weibull model were used for determining a secondary model. The results indicate that temperature and salt have a large impact on the inactivation kinetics of L. monocytogenes, while sodium lactate (NaL) has an impact in the presence of salt. The model presented in this paper for predicting inactivation of L. monocytogenes can be used as an aid in designing lethality treatments meant to control the presence of this pathogen in ready-to-eat products.  相似文献   
105.
Poly(urethane urea) elastomers are versatile and can be tailored to exhibit a broad range of mechanical response under high strain rate deformation. In this work, we utilize coarse-grained molecular dynamics simulations to elucidate the molecular mechanisms, particularly the effects of hard segment content, intermolecular interaction, and rigidity of the interface between the hard and soft segments on local morphology and rate-dependent stress-strain behavior in the ballistic regime. Simulation results qualitatively agree with available experimental data, where analysis of hard segment orientation during tensile and compression deformation and dynamic strain rate sensitivity was also performed. Further study of the intermolecular interaction on the stress-strain behavior reveals that it has a strong effect on strain hardening, particularly for a rigid interface, once the hard segment content reaches the percolation threshold. Simulation results also show that interface intermolecular interaction could become more dominant over interface rigidity in the initial stress-strain response, particularly below percolation.  相似文献   
106.
Caenorhabditis elegans vulval development is a paradigm system for understanding cell differentiation in the process of organogenesis. Through temporal and spatial controls, the fate pattern of six cells is determined by the competition of the LET-23 and the Notch signalling pathways. Modelling cell fate determination in vulval development using state-based models, coupled with formal analysis techniques, has been established as a powerful approach in predicting the outcome of combinations of mutations. However, computing the outcomes of complex and highly concurrent models can become prohibitive. Here, we show how logic programs derived from state machines describing the differentiation of C. elegans vulval precursor cells can increase the speed of prediction by four orders of magnitude relative to previous approaches. Moreover, this increase in speed allows us to infer, or ‘retrodict’, compatible genomes from cell fate patterns. We exploit this technique to predict highly variable cell fate patterns resulting from dig-1 reduced-function mutations and let-23 mosaics. In addition to the new insights offered, we propose our technique as a platform for aiding the design and analysis of experimental data.  相似文献   
107.
Wireless Networks - Internet of things consist in the deployment of constrained and battery-powered devices with a radio interface. Most industrial applications require to respect strict...  相似文献   
108.
109.
Design chain management requires many decision makers throughout the product development process. It is critical to reduce complexity and uncertainty of the design process by correctly modeling subjective data associated with decision makers’ preferences. This paper aims at using decision support to find optimal designs by modeling respondent preferences and trade-offs with consideration of uncertainty. Specifically, a simulation-based ranking methodology is implemented and incorporated with traditional conjoint analysis. This process facilitates a schematic decision support process by alleviating user fatigue. In addition, incorporation of uncertainty in the ranking process provides the capability of producing robust and reliable products. The efficacy and applicability of simulation-based conjoint ranking is demonstrated with a case study of a power-generating shock absorber design.  相似文献   
110.
Despite the problems involved in its use, SWOT (strengths-weaknesses-opportunities-threats) analysis remains a major strategic tool for listing the strengths and weaknesses of an organisation, for recording the major strengths and translating them into value. This paper presents a straightforward methodology for making a structured analysis of strengths and weaknesses, based on an analysis of important value-creating events and the strengths and weaknesses that caused these events. The focused SWOT methodology distils the strengths and weaknesses into core competences and core problems, by using the core-competence tree and the current-reality tree. The core competences and core problems are then linked into a plan of action aimed at preserving and leveraging the organisation's core competences, while defending against exposure to core problems. Applications of the methodology are presented and it is demonstrated in a detailed case study.  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