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   51602篇
  免费   2782篇
  国内免费   61篇
电工技术   369篇
综合类   40篇
化学工业   11256篇
金属工艺   957篇
机械仪表   983篇
建筑科学   1629篇
矿业工程   103篇
能源动力   1339篇
轻工业   8772篇
水利工程   484篇
石油天然气   224篇
武器工业   7篇
无线电   1998篇
一般工业技术   7879篇
冶金工业   11361篇
原子能技术   280篇
自动化技术   6764篇
  2024年   93篇
  2023年   410篇
  2022年   891篇
  2021年   1401篇
  2020年   978篇
  2019年   1168篇
  2018年   1706篇
  2017年   1686篇
  2016年   1814篇
  2015年   1406篇
  2014年   1811篇
  2013年   3627篇
  2012年   2841篇
  2011年   3114篇
  2010年   2427篇
  2009年   2335篇
  2008年   2167篇
  2007年   1948篇
  2006年   1517篇
  2005年   1347篇
  2004年   1203篇
  2003年   1080篇
  2002年   1025篇
  2001年   728篇
  2000年   720篇
  1999年   774篇
  1998年   3234篇
  1997年   2199篇
  1996年   1490篇
  1995年   882篇
  1994年   734篇
  1993年   809篇
  1992年   320篇
  1991年   300篇
  1990年   239篇
  1989年   264篇
  1988年   256篇
  1987年   224篇
  1986年   193篇
  1985年   242篇
  1984年   193篇
  1983年   151篇
  1982年   182篇
  1981年   200篇
  1980年   202篇
  1979年   114篇
  1978年   113篇
  1977年   357篇
  1976年   753篇
  1973年   89篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
For new developments such as plasma surface technologies, it is first necessary to prove their scientific possibilities and limits. Therefore it is mainly questions of process understanding and process handling, quality of the substrate and coating as well as its interactions which are considered and discussed.

To use these technologies in industry it is also necessary to consider ecological aspects as well as economic and marketing aspects. For a scientist at first these aspects are not as important.

An overview of different economic aspects of the application of plasma surface technologies is presented by considering the following: investment and running costs of plants; costs of process development for special applications; comparison of different technologies; certainty and reproducibility of the coating technologies; cost and profit balance of coated work pieces; costs of marketing.

Recently, the importance of the ecological aspects of industrial technologies has increased greatly. In most cases these questions are closely linked to the economic aspects. Nearly all ecological problems can be solved and handled, but the costs for this are increasing greatly. Although the laws currently differ in different countries, in future the laws everywhere will become more strict. The main concerns of the application and handling of a plasma assisted process are for example the use or production of toxic media, security of plants for the staff and for the environment, and handling of used coated material.  相似文献   

122.
Immunofluorescence microscopic observations indicated that a monoclonal antibody, Vmp 18, raised against the peptide 199-208 of murine interleukin 1 alpha, cross-reacted with an antigenic determinant of Drosophila thorax muscles. Immunoelectron microscopic analysis showed that the gold particles were mainly localized in the Z-line which is the attachment site of thin filaments from adjacent sarcomeres. On the contrary, the antibody failed to mark the Z-line in vertebrate skeletal muscle. A Western blot of total protein extract from Drosophila thorax muscles bound a protein of 43 kDa. Our observations suggest that the Vmp 18 antibody could contribute to clarify the composition of the Z-line in insect's flight muscles.  相似文献   
123.
124.
A cross-sectional study was performed to obtain risk factors for hepatitis B disease, HBsAg carriers and immunised personnel, among 2470 workers in a general hospital in Madrid, Spain. The data obtained were analyzed with multiple logistic regression to obtain beta coefficients for variables. The results of the analysis show that being a nurse or being regularly exposed to blood are the most important risk factors for hepatitis B acquisition. The length of time working at the same job activity was also a risk factor. The resulting beta coefficients allow the construction for a hepatitis non-immunised, HBsAg carrier and immunised HBV status, which can select subjects for a hepatitis B vaccination program.  相似文献   
125.
The adsorption of sulphate ions on Zn and Al was studied in 0.5 M NaClO4 supporting electrolyte at various pH values in the range of pH=2-7 by radiotracer techniques. It was found in both cases that the adsorption of sulphate passes over maximum in the pH range studied.The phenomena observed are interpreted by the assumption that the main component of the overall process is anion adsorption on the protonated oxides/hydroxides formed as a result of corrosion. At low pH values the steady state coverage with respect to these products should be very low owing to their dissolution; consequently the extent of anion adsorption induced must also be very low. At higher pH values where no protonation occurs the adsorption of anions decreases significantly.  相似文献   
126.
The changes to the chemical senses of taste and smell that accompany ageing are widely documented, and there has been some evidence that these changes may influence food preferences of the older consumer. However, little is known about the loss of function of the residual senses of texture and chemical irritant perception and how such losses influence food preferences. A consumer panel comprising a young (20–35 years) and an older (>65 years) age cohort was recruited and sensory tests were conducted to determine perceived intensity, preferences and the possibility of cross modal interaction between the sensory modalities of chemical irritation and texture. Liquid, semi-solid and solid food systems were studied to enable comparisons to be drawn. Older consumers were less capable of discriminating between chemical irritation and texture stimuli, indicating loss of sensory function, but there was indication that higher levels of chemical irritation were preferred among older consumers in some texture types.  相似文献   
127.
Generation of Technology-Independent Retargetable Analog Blocks   总被引:1,自引:0,他引:1  
This paper introduces a complete methodology for retargeting of analog cells to different sets of specifications. This methodology is technology-independent, thus allowing the migration, from one technology to another, of the circuit under retargeting. Careful integration of the device sizing and layout generation tasks via the incorporation of layout constraints during the sizing process allows to generate fully functional designs in a few minutes. The methodology is illustrated via the retargeting of a fully-differential Miller-compensated two-stage operational amplifier for a new set of specifications and two different technological processes.An erratum to this article can be found at  相似文献   
128.
This paper introduces a methodology for symbolic pole/zero extraction based on the formulation of the time-constant matrix of the circuits. This methodology incorporates approximation techniques specifically devoted to achieve an optimum trade-off between accuracy and complexity of the symbolic root expressions. The capability to efficiently handle even large circuits will be demonstrated through several practical circuits.  相似文献   
129.
130.
A one-dimensional mesoscopic ring with one input and two output leads acts as a spintronic beam splitter. The spatial degree of freedom, i.e., the presence of two different possible output channels, gets intertwined with the spin direction as a consequence of quantum interference and spin-orbit interaction. We investigate this kind of spatial-spin correlation, and show that the output density operator contains no quantum entanglement in the important special case when the device polarizes a perfectly random input spin state. However, the correlations are in general not purely classical, we also present specific input states with maximal spatial-spin entanglement after the ring.  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