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   474篇
  免费   10篇
电工技术   18篇
综合类   2篇
化学工业   192篇
金属工艺   18篇
机械仪表   9篇
建筑科学   4篇
矿业工程   1篇
能源动力   12篇
轻工业   83篇
石油天然气   1篇
无线电   19篇
一般工业技术   70篇
冶金工业   22篇
原子能技术   7篇
自动化技术   26篇
  2023年   3篇
  2022年   14篇
  2021年   12篇
  2020年   8篇
  2019年   8篇
  2018年   6篇
  2017年   5篇
  2016年   8篇
  2015年   11篇
  2014年   16篇
  2013年   31篇
  2012年   24篇
  2011年   35篇
  2010年   17篇
  2009年   24篇
  2008年   28篇
  2007年   25篇
  2006年   28篇
  2005年   12篇
  2004年   12篇
  2003年   18篇
  2002年   14篇
  2001年   9篇
  2000年   11篇
  1999年   12篇
  1998年   7篇
  1997年   12篇
  1996年   4篇
  1995年   4篇
  1994年   4篇
  1993年   3篇
  1992年   4篇
  1991年   6篇
  1990年   4篇
  1988年   1篇
  1987年   1篇
  1986年   5篇
  1985年   4篇
  1984年   6篇
  1983年   2篇
  1982年   3篇
  1980年   2篇
  1979年   4篇
  1978年   2篇
  1977年   4篇
  1976年   5篇
  1975年   2篇
  1974年   1篇
  1971年   1篇
  1969年   1篇
排序方式: 共有484条查询结果,搜索用时 0 毫秒
31.
Analysis of reports about incidental and accidental events in nursing care were made using a reliability engineering method. Unnatural working hours, such as evening duty, night duty falling next to a holiday, two consecutive night-duty shifts, and two consecutive evening-duty shifts were major factors in the occurrence of errors. In a mixed-division ward (a ward containing patients belonging to different divisions), rule-based errors happened more frequently than in a single-division ward. Also, less experienced nursing staffs made errors more frequently than experienced nursing staffs.  相似文献   
32.
β′-(BEDT-TTF)(TCNQ) is a compound of BEDT-TTF (=ET) and TCNQ molecules aligned orthogonally with each other, forming two-dimensional sheets and one-dimensional columns of 1/4-filled π band, respectively. It is known that the metal-insulator transition occurs at 330 K at ambient pressure. We have measured the electronic spin susceptibility by means of the EPR-NMR method at 50 MHz, and the angular dependence of g-factor and line width of EPR both at Q (34 GHz) and W (94 GHz) band. We successfully confirmed that the antiferromagnetic transition occurs in ET sheets and TCNQ columns, independently.  相似文献   
33.
Bryophytes with high As accumulation affinity were identified in the aquatic environment. We surveyed a stream near copper mine tailings and then conducted laboratory experiments to confirm As accumulation in the bryophytes with high As affinity. We found that a moss, Scopelophila cataractae, accumulates As in addition to Cu in aquatic environments and confirmed it in laboratory experiments. The highest value for As in S. cataractae from the field survey was 1300 mg/kg dry weight at relatively low As concentrations in the stream water (0.005 mg/L). In addition, Brachythecium plumosum and Rhynchostegium riparioides may also be useful bryophytes for accumulation of Cu and As, though the mechanisms of As accumulation might differ between these two bryophytes and S. cataractae.  相似文献   
34.
Cold spraying has been developed as a high-quality coating technique. In this article, copper is deposited on an AlN substrate coated by the sputtering of titanium and copper at a low pressure of less than 1.0 MPa, making this approach suitable for a wide range of engineering applications. In order to understand the adhesion mechanism at the atomic scale, the interfacial regions are carefully observed in thin foil samples from the cross sections of the specimens with a HREM. We find a unique wavy boundary between the sputtered titanium and the sputtered copper. It is assumed that the shear-instability phenomenon occurs due to the cold-spraying process and influences the adhesive strength. Furthermore, the cold-sprayed copper particles are connected directly without any oxidation layer due to the appearance of new metallic surfaces during the impact process. The TEM data clearly reveal the phenomena and mechanisms related to the impact of powder sprayed on the substrate.  相似文献   
35.
Late health effects of exposure to atomic bomb radiation have been evaluated in survivors. A cohort of 120 321 people has been followed since 1950 for mortality, including the cause of death using the Japanese population registry system (Life Span Study), and for cancer incidence using population-based cancer registries. Findings have included a markedly increased risk of leukaemia several years after the exposure, increased risk of various malignant tumours several decades after the exposure and, more recently, findings of increased rates of non-cancer diseases such as cardiovascular diseases.  相似文献   
36.
Four-terminal electrical measurement is realized on a microscopic structure in air, without a lithographic process, using a home-built quadruple-scanning-probe force microscope (QSPFM). The QSPFM has four probes whose positions are individually controlled by obtaining images of a sample in the manner of atomic force microscopy (AFM), and uses the probes as contacting electrodes for electrical measurements. A specially arranged tuning fork probe (TFP) is used as a self-detection force sensor to operate each probe in a frequency modulation AFM mode, resulting in simultaneous imaging of the same microscopic feature on an insulator using the four TFPs. Four-terminal electrical measurement is then demonstrated in air by placing each probe electrode in contact with a graphene flake exfoliated on a silicon dioxide film, and the sheet resistance of the flake is measured by the van der Pauw method. The present work shows that the QSPFM has the potential to measure the intrinsic electrical properties of a wide range of microscopic materials in situ without electrode fabrication.  相似文献   
37.
郑艳  村上洋 《食品科技》2004,(12):16-17
乳糖酸(Lactobionicacid)是乳糖氧化的产物,具有多种生理功能。目前,欧美等发达国家乳糖酸的生产是通过化学合成法,生产成本高,且有大量副产物生成。研究采用具有葡萄糖氧化酶的菌株BurkholderiacepaciaNo.24细胞培养物进行生物转化生产乳糖酸,55g湿重/1000mL细胞可将浓度为193mmol/L的乳糖转化成188mmol/L的乳糖酸,转化率可达99.8%,且转化液经薄层色谱层析和高效液相色谱检测证明在转化过程中没有副产物生成;同时,该菌株还具有广泛的底物专一性,能将葡萄糖、麦芽糖等糖类转化成相应的糖酸。  相似文献   
38.
The concept of ‘recycling’ was adopted to solve the overuse of resources by mass production and mass consumption of products in the 20th century. In the latter half of the 20th century, all companies started recycling activities slowly but positively, and some of them established their own recycling plants. This article introduces the processes through which used home appliances are made into materials (for reuse), and the machines, facilities, and methods for such reuse, as well as the results of their actual application by the study of a recycling plant. It is expected that this article would motivate the readers for recycling and to consider and feel what we, consumers, should do. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
39.
Social, technological, economic and environmental issues should be considered comprehensively for the evaluation of global-warming mitigation options. Existing integrated assessment models include assessment of quantitative factors; however, these models do not explicitly consider interactions among qualitative factors in the background – for example, introductions of nuclear power stations interact with social acceptability. In this paper, we applied a technological forecasting method – the cross-impact method – which explicitly deals with the relationships among relevant factors, and we then developed narrative scenarios having consistency with qualitative social contexts. An example of developed scenarios in 2050, assuming the global population and the gross domestic product are the same as those of the A1 scenario of the IPCC Special Report on Emissions Scenarios, tells us that: (1) the Internet will be extensively used in all regions; (2) the global unified market will appear; (3) regional cultures will tend to converge; (4) long-term investments (of more than 30 years) will become difficult and therefore nuclear-power stations will not increase so remarkably; (5) the self-sufficient supply and diversification of primary energy sources will not progress so rapidly; and (6) due to the widespread use of the Internet, people will be more educated in global environmental issues and environmental costs will be more socially acceptable.  相似文献   
40.
The best-fit values of the Michaelis constant (Km) and the maximum velocity (V) in the Michaelis-Menten equation can be obtained by the method of least squares with the Taylor expansion for the sum of squares of the absolute residual, i.e., the difference between the observed velocity and the corresponding velocity by calculation. This method makes it possible to determine the values of Km and V not in a trial-and-error manner but in a deductive and unique manner after some iterative procedures starting from arbitrary approximate values of Km and V. These values can be said to be uniquely determined for a set of data as the finally converged values are no longer dependent upon the initial approximate values of Km and V. It is also very important to obtain initial approximate values of parameters for the application of the method described above. A simple method is proposed to estimate the approximate values of parameters involved in fractional functions. The method of rearrangement after canceling of denominator of a fractional function can be utilized to obtain approximate values, not only for cases of two unknown parameters such as the Michaelis-Menten equation, but also for cases with more than two unknowns.  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