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   435篇
  免费   22篇
  国内免费   1篇
电工技术   5篇
综合类   2篇
化学工业   93篇
金属工艺   7篇
机械仪表   12篇
建筑科学   44篇
能源动力   9篇
轻工业   95篇
无线电   27篇
一般工业技术   67篇
冶金工业   63篇
原子能技术   8篇
自动化技术   26篇
  2024年   6篇
  2023年   11篇
  2022年   19篇
  2021年   22篇
  2020年   19篇
  2019年   15篇
  2018年   6篇
  2017年   10篇
  2016年   4篇
  2015年   9篇
  2014年   18篇
  2013年   31篇
  2012年   16篇
  2011年   36篇
  2010年   21篇
  2009年   22篇
  2008年   17篇
  2007年   20篇
  2006年   20篇
  2005年   14篇
  2004年   11篇
  2003年   11篇
  2002年   8篇
  2001年   4篇
  1999年   5篇
  1998年   8篇
  1997年   3篇
  1996年   5篇
  1995年   6篇
  1994年   2篇
  1993年   3篇
  1992年   2篇
  1991年   3篇
  1990年   4篇
  1989年   3篇
  1988年   2篇
  1987年   3篇
  1986年   4篇
  1985年   2篇
  1984年   4篇
  1981年   5篇
  1979年   2篇
  1978年   2篇
  1975年   4篇
  1969年   3篇
  1962年   1篇
  1961年   1篇
  1957年   1篇
  1956年   1篇
  1951年   1篇
排序方式: 共有458条查询结果,搜索用时 15 毫秒
71.
72.
Dyslipoproteinemia of the Nagase analbuminemic rat (NAR) is characterized by elevated concentrations of VLDL and LDL attributed to increased rates of liver lipoprotein synthesis. Increased lysophosphatidylcholine (LPC) in NAR HDL has been attributed to high plasma LCAT activity. We show here that, as compared with Sprague-Dawley rats (SDR), NAR plasma triacylglycerol (TAG), total cholesterol (TC), HDL TAG, protein, total phospholipids (PL), LPC, and PS are increased. These alterations rendered the NAR HDL particle more susceptible to the activity of the enzyme hepatic lipoprotein lipase (HL), which otherwise was unaltered in our study. Fractional catabolic rates in blood of the autologous 125I-apoHDL (median and lower quartile values), were, respectively, 0.231 and 1.645 (n=10) in NAR as compared with 0.140 and 0.109 (n=10) in SDR (P=0.012), corresponding to synthesis rates of HDL protein of 89.8±33.7 mg/d in NAR and 17.4±6.5 mg/d in SDR (P=0.0122). Furthermore, Swiss mouse macrophage free-cholesterol (FC) efflux rates, measured as the percent [14C]-cholesterol efflux/6 h, were 8.2±2.3 (n=9) in NAR HDL and 11.2±3.2 (n=10) in SDR HDL (P=0.03). Therefore, in NAR the modification of the HDL composition slows down the cell FC efflux rate, and together with the increased rate of plasma HDL metabolism influences the reverse cholesterol transport system.  相似文献   
73.
The paper investigates the behaviors of recycled aggregate concrete-filled steel tubular (RACFST) columns under eccentric loadings with the incorporation of expansive agents. A total of 16 RACFST columns were tested in this study. The main parameters varied in this study are recycled coarse aggregate replacement percentages (0%, 30%, 50%, 70%, and 100%), expansive agent dosages (0%, 8%, and 15%) and an eccentric distance of compressive load from the center of the column (0 and 40 mm). Experimental results showed that the ultimate stresses of RACFST columns decreased with increasing recycled coarse aggregate replacement percentages but appropriate expansive agent dosages can reduce the decrement; the incorporation of expansive agent decreased the ultimate stresses of RACFST columns but an appropriate dosage can increase the deformation ability. The recycled coarse aggregate replacement percentages have limited influence on the ultimate stresses of the RACFST columns and has more effect than that of the normal aggregate concrete-filled steel tubular columns.  相似文献   
74.
In response to the increasing public concern over the effects of construction waste on the environment, a performance assessment system has been designed to provide an instant, online assessment of how well a construction site performs environmentally, e.g. measuring the level of pollution generated from a construction site. Through the use of both Internet and database technologies, it is possible to collect and present data that are essential for environmental management online. To achieve this, a set of environmental performance parameters was derived through a postal questionnaire survey and interviews with experts in the field. A conceptual framework was developed, of which the key components were: template, knowledge base, output data and benchmark group. In combination, these factors provide a system that enables speedy assessment and effective management of environmental performance on construction sites, hence prompt decisions can be made and corrective actions can be taken before potential hazards turn into real disasters.  相似文献   
75.
Evaluations of existing waste recycling methods: A Hong Kong study   总被引:3,自引:0,他引:3  
Environmental problems have been considered as a serious situation in Hong Kong construction. Waste management is pressing harder with the alarming signal warning the industry. Reuse, recycling and reducing the wastes are considered as the only methods to recover the wastes generated; however, the implementations still have much room for improvement. In order to ameliorate the existing situations, evaluations of the existing waste recycling methods are studied in this research. A telephone interviewing to the recyclers, site visits to the construction and demolition sites (including the Lower Ngau Tau Kok Estate Phase 1) and the centralized recycling plant in Tuen Mun Area 38 are under investigation. Difficulties encountered for various recycling parties are investigated. Rather than the poor quality found from the recyclable materials, they found the high investment cost, lengthy demolition period and limited space caused the major barriers for them. Therefore, some recommendations are suggested: (i) proposing a higher landfill charging scheme; (ii) setting up a centralized centre for recycling the materials; (iii) examining the Hong Kong government should be supported in the provision of land for recycling plants; (iv) implementing innovative demolition methods; (v) allowing some locations in town for residents’ easy access to drop-off recyclable materials; (vi) allowing flexible demolition periods; (vii) setting up recycling plant in town or in the form of mobile installations; (viii) reusing the reusable components as donations to the charity organization; (ix) providing higher flexibility in receiving concrete waste in Tuen Mun Area 38 recycling plant; and (x) balancing the supply and demand of recycled materials through legislations or incentive schemes.  相似文献   
76.
Moeck  Christian  Merk  Markus  Radny  Dirk  Auckenthaler  Adrian  Schirmer  Mario  Gabriel  Thomas 《Grundwasser》2022,27(3):187-196
Grundwasser - Eine nachhaltige Wasserversorgung in urbanen Gebieten stellt aufgrund des Nutzungsdrucks sowie vielfältiger anthropogener Einträge eine große Herausforderung dar....  相似文献   
77.
This paper reviews the recent research progress in the incorporation of plasmonic nanostructures with photovoltaic devices and the potential for surface plasmon enhanced absorption. We first outline a variety of cell architectures incorporating metal nanostructures. We then review the experimental fabrication methods and measurements to date, as well as systematic theoretical studies of the optimal nanostructure shapes. Finally we discuss photovoltaic absorber materials that could benefit from surface plasmon enhanced absorption.  相似文献   
78.
Kao J  Bai P  Chuang VP  Jiang Z  Ercius P  Xu T 《Nano letters》2012,12(5):2610-2618
We demonstrated a versatile approach to obtain layered nanoparticle sheets with in-plane hexagonal order and 3-D ordered arrays of single nanoparticle chains in thin films upon blending nanoparticles with block copolymer (BCP)-based supramolecules. Basic understanding on the thermodynamic and kinetic aspects of the assembly process paved a path to manipulate these assemblies to meet demands in nanoparticle-based device fabrication and understand structure-property correlations.  相似文献   
79.
Exposures to carcinogenic polycyclic aromatic hydrocarbons (PAHs) have been linked to human lung cancer. The purpose of this study was to assess lung cancer risk caused by inhalation exposure to nano/ultrafine particle-bound PAHs at the population level in Taiwan appraised with recent published data. A human respiratory tract model was linked with a physiologically based pharmacokinetic model to estimate deposition fraction and internal organic-specific PAHs doses. A probabilistic risk assessment framework was developed to estimate potential lung cancer risk. We reanalyzed particle size distribution, total-PAHs, particle-bound benzo(a)pyrene (B[a]P) and PM concentrations. A dose-response profile describing the relationships between external B[a]P concentration and lung cancer risk response was constructed based on population attributable fraction (PAF). We found that 90% probability lung cancer risks ranged from 10(-5) to 10(-4) for traffic-related nano and ultrafine particle-bound PAHs, indicating a potential lung cancer risk. The particle size-specific PAF-based excess annual lung cancer incidence rate due to PAHs exposure was estimated to be less than 1 per 100,000 population, indicating a mild risk factor for lung cancer. We concluded that probabilistic risk assessment linked PAF for limiting cumulative PAHs emissions to reduce lung cancer risk plays a prominent role in future government risk assessment program.  相似文献   
80.
The wrinkle dynamics (such as reversibility and stability) of human skin are affected by the external stimuli, as well as the skin's structure and mechanical properties. Inspired by these tunable responses, three types of moisture‐responsive wrinkle dynamics are achieved, for the first time, through a single film–substrate system. These dynamics include: (1) completely reversible wrinkles formation; (2) irreversible wrinkles formation I: the initially formed wrinkles can be permanently erased and never reappear; and (3) irreversible wrinkles formation II: once the wrinkles form, they can no longer be erased. The key to success is to control the stiffness and thickness ratios of the film and the substrate, and tailor the crosslink degree/gradient of the film to allow for moisture‐dependent changes of modulus and swelling degree. These unique responsive dynamics motivate the invention of a series of optical devices triggered by moisture, including anticounterfeit tabs, encryption devices, water indicators, light diffusors, and antiglare films. This study also paves the road for further understanding of the skin wrinkling dynamics and manipulation.  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