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   657篇
  免费   28篇
  国内免费   1篇
电工技术   6篇
综合类   2篇
化学工业   146篇
金属工艺   22篇
机械仪表   27篇
建筑科学   51篇
矿业工程   1篇
能源动力   11篇
轻工业   120篇
水利工程   3篇
无线电   16篇
一般工业技术   107篇
冶金工业   92篇
原子能技术   8篇
自动化技术   74篇
  2023年   10篇
  2022年   20篇
  2021年   24篇
  2020年   10篇
  2019年   17篇
  2018年   16篇
  2017年   12篇
  2016年   21篇
  2015年   13篇
  2014年   23篇
  2013年   29篇
  2012年   36篇
  2011年   43篇
  2010年   37篇
  2009年   30篇
  2008年   44篇
  2007年   28篇
  2006年   32篇
  2005年   16篇
  2004年   16篇
  2003年   20篇
  2002年   17篇
  2001年   14篇
  2000年   10篇
  1999年   9篇
  1998年   15篇
  1997年   4篇
  1996年   9篇
  1995年   7篇
  1994年   2篇
  1992年   4篇
  1991年   3篇
  1990年   4篇
  1989年   4篇
  1988年   3篇
  1986年   3篇
  1985年   2篇
  1984年   2篇
  1977年   4篇
  1976年   2篇
  1975年   3篇
  1973年   4篇
  1971年   3篇
  1969年   1篇
  1905年   14篇
  1904年   16篇
  1903年   13篇
  1902年   11篇
  1899年   1篇
  1898年   2篇
排序方式: 共有686条查询结果,搜索用时 15 毫秒
71.
Anterior knee pain in our military population consititutes a diagnostic and therapeutic problem that is not always easily solved. In recent years, a better understanding of the biomechanics of the patello-femoral joint has contributed to the successful classification and treatment of many patients. However, the cause of pain remains elusive in a significant subset of patients who show no clinical or radiographic evidence of patellar malalignment and continue to have persistent pain despite adequate physiotherapy. In this article, the classification and approach to anterior knee pain are reviewed. Emphasis is placed on dividing patients into four subsets namely; normal tracking, patellar tilt, patellar subluxation and extra-articular causes of anterior knee pain. A more rational approach to the problem can then be employed and successful rehabilitation and/or surgery can be expected.  相似文献   
72.
The melting behavior of polyglycolide (PGA) with eight other biodegradable polymers was investigated to determine whether forming a blend could be used as a method of lowering the melting point of PGA. Blends were prepared by melt processing in differential scanning calorimetry (DSC) pans and were then analyzed by DSC. In every case, a comparison of the blend DSC plot with those of the two individual components showed that the melting behavior of PGA remained unchanged by blending. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2937–2939, 2003  相似文献   
73.
74.
Complaints of racism from visible-minority students at dalhousie medical school led to a study of the problem. Nancy Robb reports that the results surprised some people.  相似文献   
75.
The basic purpose of CAMAC is to provide a standardized method for transferring data and control information between instrurrentation modules and a digital controller. CAMAC encompasses both a hardware standard for housing the modular components of a system and an electrical and logical standard for the control "language" used to effect the information transfer. The CAMAC specification contains the formally stated rules for hoth of these aspects of CAMAC. This paper concentrates on the control language and describes some of its features and uses in a less formal way than in the specification, and therefore may be useful as an introduction to the subject. Other papers in this series consider other aspects of CAMAC, including its place in the context of instrumentation systems, hardware aspects, signal standards, the Branch Highway, and coupling to computers and control systems. Here, the scope is limited to the process of information interchange within the CAMAC crate. This is a revised version of a paper previously publishled. Since the first version was published, a revised version of the CAMAC specification has been issued. This present paper is based only on the revised specification. Information on the differences between the original and revised CAMAC specifications is available.  相似文献   
76.
Microcystis aeruginosa has quickly risen in infamy as one of the most universal and toxic bloom-forming cyanobacteria. Here we presented a species of golden alga (Poterioochromonas sp. strain ZX1), which can feed on toxic M. aeruginosa without any adverse effects from the cyanotoxins. Using flow cytometry, the ingestion and maximal digestion rates were estimated to be 0.2∼1.2 and 0.2 M. aeruginosa cells (ZX1 cell)−1 h−1, respectively. M. aeruginosa in densities below 107 cells mL−1 could be grazed down by ZX1, but no significant decrease was observed when the initial density was 3.2 × 107 cells mL−1. ZX1 grazing was a little influenced by the light intensity (0.5∼2500 lx) and initial pH of the medium (pH = 5.0∼9.5). ZX1 could not survive in continuous darkness for longer than 10 days. The pH value was adjusted to 8 by ZX1 while to 10 by M. aeruginosa. This study may shed light on understanding the ecological interactions between M. aeruginosa and mixotrophic Poterioochromonas sp. in aquatic ecosystems.  相似文献   
77.
Costs of mastitis: facts and perception   总被引:2,自引:0,他引:2  
A model to calculate the economic losses of mastitis on an average Dutch dairy farm was developed and used as base for a tool for farmers and advisors to calculate farm-specific economic losses of mastitis. The economic losses of a clinical case in a default situation were calculated as euro210, varying from euro164 to euro235 depending on the month of lactation. The total economic losses of mastitis (subclinical and clinical) per cow present in a default situation varied between euro65 and euro182/cow per year depending on the bulk tank somatic cell count. The tool was used to measure perception of the total economic losses of mastitis on the farm and the farmers' assessment of the cost factors of mastitis on 78 dairy farms, of which 64 were used for further analyses. Most farmers (72%) expected their economic losses to be lower than those revealed by our calculation made with their farm information. Underestimating the economic losses of mastitis can be regarded as a general problem in the dairy sector. The average economic losses assessed by the farmers were euro78/cow per year, but a large variation was given, euro17-198/cow per year. Although the average assessment of the farmers of the different cost factors is close to the default value, there is much variation. To improve the adoption rate of advice and lower the incidence of mastitis, it is important to show the farmers the economic losses of mastitis on their farm. The tool described in this paper can play a role in that process.  相似文献   
78.
BACKGROUND: Many consumers perceive organic foods as more nutritious than conventional foods. However, the existing evidence is insufficient to support or refute this belief. The purpose of the present study was to investigate the effect of three different model cultivation systems on selected major and trace element contents of dried foodstuffs (carrots, kale, peas, potatoes and apples) grown in two consecutive years, as well as mineral retention determined in 36 rats (second generation in a multi‐generation study) fed diets based on these foodstuffs from one year. RESULTS: Overall, there was no evident trend towards differences in element content of foodstuffs or diets due to the use of different cultivation systems, and differences between harvest years exceeded those seen between cultivation methods. Also, no significant differences in the retention of elements in rats fed diets derived from different cultivation systems were seen, since higher intake resulted in correspondingly higher excretion. CONCLUSION: This study does not support the belief that organically grown foodstuffs generally contain more major and trace elements than conventionally grown foodstuffs, nor does there appear to be an effect on the bioavailability of major and trace minerals in rats. Copyright © 2008 Society of Chemical Industry  相似文献   
79.
80.
In the context of ongoing densification of cities and aging urban populations, public spaces are a crucial infrastructure to support the physical and mental wellbeing of urban residents. The design of public space furniture elements is often standardised, and not considered in relation to environmental conditions and mechanisms of social interaction. This article presents a digital workflow to generate site-specific designs for shaded public seating, considering the relationships of local public places to their surroundings. A strategy for customised and site-specific design is developed through the use of multiple software tools, employing evolutionary algorithms and multi-objective optimisation. The method is applied to a small public space canopy prototype installed within a public housing estate in Hong Kong, incorporating additional criteria to achieve a low-cost and light-weight structure. Through multiple stages of refinement and optimisation, a material, structural and social performance-driven outcome was achieved that creates a shaded space for public seating, people watching and social interaction. As part of a larger research agenda exploring architectural form-finding and environmental psychology, the project represents potential new applications in the emerging field of socially driven computational design.  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