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   450篇
  免费   5篇
电工技术   14篇
化学工业   116篇
金属工艺   7篇
机械仪表   8篇
建筑科学   31篇
能源动力   16篇
轻工业   24篇
水利工程   2篇
无线电   17篇
一般工业技术   79篇
冶金工业   66篇
自动化技术   75篇
  2024年   7篇
  2023年   9篇
  2022年   8篇
  2021年   11篇
  2020年   7篇
  2019年   7篇
  2018年   6篇
  2017年   6篇
  2016年   10篇
  2015年   5篇
  2014年   13篇
  2013年   27篇
  2012年   14篇
  2011年   22篇
  2010年   14篇
  2009年   16篇
  2008年   12篇
  2007年   14篇
  2006年   10篇
  2005年   18篇
  2004年   9篇
  2003年   11篇
  2002年   13篇
  2001年   10篇
  2000年   8篇
  1999年   8篇
  1998年   19篇
  1997年   11篇
  1996年   11篇
  1995年   15篇
  1994年   7篇
  1993年   14篇
  1992年   4篇
  1991年   7篇
  1990年   4篇
  1989年   9篇
  1988年   3篇
  1987年   5篇
  1986年   5篇
  1985年   8篇
  1984年   2篇
  1983年   5篇
  1981年   7篇
  1980年   3篇
  1978年   3篇
  1977年   4篇
  1976年   5篇
  1975年   2篇
  1971年   2篇
  1958年   1篇
排序方式: 共有455条查询结果,搜索用时 0 毫秒
41.
Lennart Sjberg 《Displays》1987,8(4):210-212
A discussion of the factors involved in the subjective perception of television picture quality is presented. Much of the work in this field is cited, and it is concluded that future work needs to consider a broader range of variables than has been looked at so far.  相似文献   
42.
The sequence of estimates formed by the LMS algorithm for a standard linear regression estimation problem is considered. It is known since earlier that smoothing these estimates by simple averaging will lead to, asymptotically, the recursive least-squares algorithm. In this paper, it is first shown that smoothing the LMS estimates using a matrix updating will lead to smoothed estimates with optimal tracking properties, also in case the true parameters are slowly changing as a random walk. The choice of smoothing matrix should be tailored to the properties of the random walk. Second, it is shown that the same accuracy can be obtained also for a modified algorithm, SLAMS, which is based on averages and requires much less computations.  相似文献   
43.
    
There are dozens of studies made and ongoing related to wind integration. However, the results are not easy to compare. IEA WIND R&D Task 25 on ‘Design and Operation of Power Systems with Large Amounts of Wind Power’ collects and shares information on wind generation impacts on power systems, with analyses and guidelines on methodologies. In the state‐of‐the‐art report (October, 2007), and the final report of the 3 years period (July, 2009) the most relevant wind power grid integration studies have been analysed especially regarding methodologies and input data. Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and aggregation benefits of wide areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and functioning electricity markets at less than day‐ahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefits, electricity markets and larger balancing areas. Best practices in wind integration studies are described. There is also benefit when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels and this should be highlighted more in future studies. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
44.
45.
    
The bottom-up construction of an artificial cell requires the realization of synthetic cell division. Significant progress has been made toward reliable compartment division, yet mechanisms to segregate the DNA-encoded informational content are still in their infancy. Herein, droplets of DNA Y-motifs are formed by liquid–liquid phase separation. DNA droplet segregation is obtained by cleaving the linking component between two populations of DNA Y-motifs. In addition to enzymatic cleavage, photolabile sites are introduced for spatio-temporally controlled DNA segregation in bulk as well as in cell-sized water-in-oil droplets and giant unilamellar lipid vesicles (GUVs). Notably, the segregation process is slower in confinement than in bulk. The ionic strength of the solution and the nucleobase sequences are employed to regulate the segregation dynamics. The experimental results are corroborated in a lattice-based theoretical model which mimics the interactions between the DNA Y-motif populations. Altogether, engineered DNA droplets, reconstituted in GUVs, can represent a strategy toward a DNA segregation module within bottom-up assembled synthetic cells.  相似文献   
46.
    
Oceans cover 71 % of Earth's surface and are home to hundreds of thousands of species, many of which are microbial. Knowledge about marine microbes has strongly increased in the past decades due to global sampling expeditions, and hundreds of detailed studies on marine microbial ecology, physiology, and biogeochemistry. However, the translation of this knowledge into biotechnological applications or synthetic biology approaches using marine microbes has been limited so far. This review highlights key examples of marine bacteria in synthetic biology and metabolic engineering, and outlines possible future work based on the emerging marine chassis organisms Vibrio natriegens and Halomonas bluephagenesis. Furthermore, the valorization of algal polysaccharides by genetically enhanced microbes is presented as an example of the opportunities and challenges associated with blue biotechnology. Finally, new roles for marine synthetic biology in tackling pressing global challenges, including climate change and marine pollution, are discussed.  相似文献   
47.
    
The quest for developing materials that provide a perfect trade-off between factors such as enzyme-like response, stability, and low cost has been a long-standing challenge in the field of biosensing. Metal-organic frameworks (MOFs) and their composites have emerged as promising candidates for biosensing applications due to their exceptional properties such as tunable pore size, high specific surface area, and exposed active sites. A comparative study of the intrinsic peroxidase-like activity of five different MOF materials: Fe-BTC, NH2-MIL-101(Fe), composites of Fe-BTC with polymers polydopamine (PDA), poly p-phenylenediamine (PpPDA), and poly(3,4-ethylenedioxythiophene) is reported for the detection of H2O2, an important biomarker in biomedical diagnostics. The response of these materials toward H2O2 via electrochemical and colorimetric techniques is mapped and it is found that, at neutral pH, the Fe-BTC/PEDOT composite exhibits the highest sensitivity and activity compared to other MOF materials in this study. The results indicate that the combination of unique properties of Fe-BTC and conducting polymer PEDOT, improves the peroxidase-like activity of the Fe-BTC/PEDOT composite compared to the individual components. This work presents a new opportunity for easy-to synthesize and low-cost MOFs/conducting polymer composites for biosensing applications and provides significant insights to achieve rational design of composites with desirable functional properties  相似文献   
48.
    
Rapidly increasing levels of variable inverter‐based renewable energy sources (are quickly changing electric power systems and prompting questions about how the systems will be operated when renewable generation becomes the dominant technologies. In this article, we review the status of this shifting paradigm in power systems throughout the world. We then review the implications of this shift, focusing on the rising challenges, and we provide an overview and technology‐readiness classifications of some proposed mitigation strategies. Finally, we highlight outstanding questions that will require solutions to reach these ultrahigh shares of variable inverter‐based renewable energy sources. This article is categorized under:
  • Wind Power > Systems and Infrastructure
  • Energy Systems Economics > Systems and Infrastructure
  • Energy Infrastructure > Systems and Infrastructure
  相似文献   
49.
    
Both stereolithographic printing of microfluidics and inkjet printing of electronics are promising tools for the fabrication of lab‐on‐a‐chip devices. However, the combination of these two technologies has been a challenge so far, as the 3D‐printed components usually have to be bonded manually to the substrates functionalized with printed electronics. Here, a surface modification method is demonstrated for enabling the direct stereolithographic printing of microfluidic structures onto a variety of different substrates that are usually employed for printed electronics. The approach makes use of an acrylate‐terminated silane that covalently binds substrate and polymer network of the 3D print. The bonding strength is quantified and the compatibility of the concept with printed electrodes in a microfluidic channel is evaluated.  相似文献   
50.
Starting from the Conservative assertion that home ownership fosters politically active and virtuous citizens, this paper examines two lines of argument in housing theory; (a) Jim Kemeny's thesis that owner occupation is closely linked to increasing privatism, i.e. a growth in lifestyles centred around the home and privacy rather than the workplace or the public affairs in a society, and (b) Peter Saunders' thesis that home owners will organise and mobilise politically in defence of their property interests if and when various government agencies threaten to remove their tax subsidies. To test these propositions empirically, data on the effects of the rapid and comprehensive dismantling of tax privileges to Swedish home owners in the 1980s and early 1990s are confronted with data on political interest, participation and knowledge as well as civic trust and responsibility from the Swedish election surveys of 1979, 1985 and 1991. Contrary to Conservative beliefs, home owners do not stand out as 'democratic examples'; with the exception of political knowledge and party membership, they are no more 'civil' or 'democratic' than other citizens. There is also not much to support Kemeny's 'privatism' or Saunders' 'reaction-to-threat' theses. Although home owners in Sweden saw their tax privileges diminishing rapidly during the 1980s and early 1990s, they do not show the distinctive patterns of change in democratic orientation and spirit predicted by these two housing theorists. To allow for an even more conclusive test of Kemeny's 'privatism' thesis, however, one must overcome the mismatch of income definitions in housing statistics and election survey data.  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