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   2533篇
  免费   42篇
  国内免费   2篇
电工技术   17篇
化学工业   357篇
金属工艺   42篇
机械仪表   47篇
建筑科学   95篇
矿业工程   1篇
能源动力   63篇
轻工业   234篇
水利工程   18篇
石油天然气   1篇
无线电   171篇
一般工业技术   334篇
冶金工业   951篇
原子能技术   26篇
自动化技术   220篇
  2023年   14篇
  2022年   17篇
  2021年   34篇
  2020年   24篇
  2019年   27篇
  2018年   23篇
  2017年   28篇
  2016年   30篇
  2015年   37篇
  2014年   44篇
  2013年   109篇
  2012年   87篇
  2011年   103篇
  2010年   78篇
  2009年   84篇
  2008年   99篇
  2007年   94篇
  2006年   96篇
  2005年   79篇
  2004年   71篇
  2003年   59篇
  2002年   65篇
  2001年   47篇
  2000年   62篇
  1999年   61篇
  1998年   139篇
  1997年   109篇
  1996年   88篇
  1995年   59篇
  1994年   56篇
  1993年   52篇
  1992年   36篇
  1991年   26篇
  1990年   40篇
  1989年   43篇
  1988年   36篇
  1987年   37篇
  1986年   33篇
  1985年   31篇
  1984年   36篇
  1983年   32篇
  1982年   19篇
  1981年   26篇
  1980年   17篇
  1979年   23篇
  1978年   23篇
  1977年   29篇
  1976年   51篇
  1975年   11篇
  1974年   15篇
排序方式: 共有2577条查询结果,搜索用时 31 毫秒
71.
The purpose of this article is to provide guidance on enhancing human response to emergency communication. This guidance can, in turn, help engineers improve the design of emergency notification and messaging systems, which, as a result, can help inform occupant response, reduce occupant evacuation time, and increase occupant safety. The article begins with a literature review on how people respond to emergencies. The Protective Action Decision Model, which describes the decision-making process that precedes human response in disaster events, is used as a framework for the literature collected as part of this review. This model is divided into three pre-decisional and five decisional processes. The method used to create the guidance document is then explained, including the six steps taken to review the literature collected (from 162 engineering and social science sources), generate findings from this literature, and compile the key statements found in the guidance document. Guidance on alerts, visual/audible warnings and dissemination of warning messages are provided. These are organized according to alert/warning type and dissemination method. The findings of the literature review include five guidance statements on alerts, 16 guidance statements on visual warnings, seven guidance statements on audible warnings and eight guidance statements on the dissemination of warning messages. Finally, guidance on emergency message testing, including language, readability and fire drills as a means of response testing, is provided. It is envisioned that this guidance will inform practitioners on the design of future emergency communications and subsequently enhances evacuee performance through a better understanding of the manner in which emergency information is processed and the tools available to provide such information.  相似文献   
72.
The primary objective of this paper is to examine the influence of natural amenities on student migration decisions using institution-level data from the National Center for Education Statistics’ Integrated Postsecondary Education Data System. We surpass the scope of previous studies focused on natural amenities, which rely on a limited selection of state-level measures, by matching interpolated weather station- and county-level climate data to each post-secondary institution. Results suggest that students consider natural amenities in their migration to college decision and, in a number of cases, preferences for natural amenities vary based on origin state amenity conditions. Nonetheless, migration decisions are dominated by origin state educational opportunities and by proximity of the student’s origin state to the state of college attendance.  相似文献   
73.
Children are very different from adults—they have developing motor skills, limited reach, short attention spans, limited exposure to traditional user interfaces and social protocols. How do we evaluate user interfaces for children? In this paper, we present four evaluative techniques that we have successfully used with children.  相似文献   
74.
High efficiency solar steam gasification of biomass is carried out in a prototype molten salt reactor for solar-only and solar-autothermal hybrid operation. Previous demonstration of the prototype 3-kW solar gasifier for steam gasification of cellulose at stoichiometric conditions demonstrated thermal efficiency of 44% during continuous operation at 1200 K. The present work expands the range of operating conditions to consider two challenges. Hybridization between solar and autothermal modes of operation is accomplished by adding oxygen directly to the reactor. Control of the H2:CO ratio of the product gas is accomplished through in-situ steam shifting. Hybridization stabilized temperatures for variations in radiative input as large as a 30% reduction in power, corresponding to conditions where both sensible and chemical heat demands for the process were fully met by exothermic heat release with no significant challenges. Peak efficiencies and carbon conversion values observed are 45% and 99.5% respectively. The resulting product gas stream composition was shifted from a hydrogen and carbon monoxide ratio of 1:1 with stoichiometric steam delivery to a ratio of 1.7:1 with steam at nine times the stoichiometric amount, only slightly lower than equilibrium predictions. The results demonstrate very favorable attributes for the molten salt reactor in a continuous fuel production process.  相似文献   
75.
Chronic infection with Helicobacter pylori increases risk of gastric diseases including gastric cancer. Despite development of a robust immune response, H. pylori persists in the gastric niche. Progression of gastric inflammation to serious disease outcomes is associated with infection with H. pylori strains which encode the cag Type IV Secretion System (cag T4SS). The cag T4SS is responsible for translocating the oncogenic protein CagA into host cells and inducing pro-inflammatory and carcinogenic signaling cascades. Our previous work demonstrated that nutrient iron modulates the activity of the T4SS and biogenesis of T4SS pili. In response to H. pylori infection, the host produces a variety of antimicrobial molecules, including the iron-binding glycoprotein, lactoferrin. Our work shows that apo-lactoferrin exerts antimicrobial activity against H. pylori under iron-limited conditions, while holo-lactoferrin enhances bacterial growth. Culturing H. pylori in the presence of holo-lactoferrin prior to co-culture with gastric epithelial cells, results in repression of the cag T4SS activity. Concomitantly, a decrease in biogenesis of cag T4SS pili at the host-pathogen interface was observed under these culture conditions by high-resolution electron microscopy analyses. Taken together, these results indicate that acquisition of alternate sources of nutrient iron plays a role in regulating the pro-inflammatory activity of a bacterial secretion system and present novel therapeutic targets for the treatment of H. pylori-related disease.  相似文献   
76.
NF-κB-inducing kinase (NIK), the essential upstream kinase, which regulates activation of the noncanonical NF-κB pathway, has important roles in regulating immunity and inflammation. In addition, NIK is vital for maintaining cellular health through its control of fundamental cellular processes, including differentiation, growth, and cell survival. As such aberrant expression or regulation of NIK is associated with several disease states. For example, loss of NIK leads to severe immune defects, while the overexpression of NIK is observed in inflammatory diseases, metabolic disorders, and the development and progression of cancer. This review discusses recent studies investigating the therapeutic potential of NIK inhibitors in various diseases.  相似文献   
77.
International Journal of Computer Vision - We introduce a neural architecture for navigation in novel environments. Our proposed architecture learns to map from first-person views and plans a...  相似文献   
78.
Almonds are blanched by exposure to hot water or steam-injected water to remove the pellicle (skin) from the kernel. This study evaluated the survival of Salmonella Enteritidis PT 30, Salmonella Senftenberg 775W and Enterococcus faecalis on whole raw almond kernels exposed to hot water. Whole, inoculated (7 to 9 log CFU/g) Nonpareil almonds (40 g) were submerged in 25 L of water maintained at 60, 70, 80 and 88 °C. Almonds were heated for up to 12 min, drained for 2 s, and transferred to 80 mL of cold (4 °C) tryptic soy broth. Almonds in broth were stomached at high speed for 2 min, serially diluted, plated onto tryptic soy and bismuth sulfite agars (Salmonella) or bile esculin agar (Enterococcus) and incubated at 37 °C for 24 and 48 h, respectively. D values of 2.6, 1.2, 0.75 and 0.39 min were calculated for exposure of S. Enteritidis PT 30 to water at 60, 70, 80 and 88 °C, respectively; the calculated z value was 35 C°. D values determined for Salmonella Senftenberg 775W and E. faecalis at 88 °C were 0.37 and 0.36 min, respectively. Neither Salmonella serovar could be recovered by enrichment of 1-g samples after almonds inoculated at 5 log CFU/g were heated at 88 °C for 2 min. These data will be useful to validate almond industry blanching processes.  相似文献   
79.
Sustainability is an issue of concern in many industrial sectors. The construction industry is no exception. The study described in this paper adopts a critical qualitative approach to investigate sustainability policy practices in the construction industry. This approach includes a statement of principles, sustainability reporting incorporated within a financial report, and a stand-alone sustainability reporting system. The top international contractors listed by Engineering News Record (ENR) were examined. The results show that sustainability policy development varies from case to case in these companies but trends are emerging on common issues addressed. The findings show a trend of increasingly level of disclosure of corporation's commitmnets an achievements on sustainability. Similarly, the energy efficiency and conservation, greenhouse gas emission reduction and integration of renewable energy resources into projects are among the common themes of these sustainability policies disclosed by construction contractors. The construcion industry can learn from the energy sector that is advanced in sustainability reporting.  相似文献   
80.
The present study describes the effect of friction stir processing parameters on formability of Mg AZ31B sheet under biaxial stretching. The formability of friction stir processed sheet was studied by limiting dome height test in biaxial strain deformation mode. The experiments were carried out as per the Taguchi parametric design concepts and an L9 orthogonal array was used to study the influence of various combinations of process parameters. Statistical optimization technique, ANOVA was used to determine the optimum levels and to find the significance of each process parameter. The results indicate that the traverse speed is the most significant factor followed by the rotational speed and the tilt angle in deciding the formability of friction stir processed magnesium alloy. In addition, mathematical model was developed to establish relationship between the different process variables with formability by regression analysis.  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