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   30030篇
  免费   1369篇
  国内免费   132篇
电工技术   490篇
综合类   235篇
化学工业   5111篇
金属工艺   799篇
机械仪表   671篇
建筑科学   806篇
矿业工程   152篇
能源动力   506篇
轻工业   4048篇
水利工程   217篇
石油天然气   136篇
武器工业   10篇
无线电   1610篇
一般工业技术   5461篇
冶金工业   7476篇
原子能技术   173篇
自动化技术   3630篇
  2023年   309篇
  2022年   276篇
  2021年   628篇
  2020年   517篇
  2019年   448篇
  2018年   919篇
  2017年   830篇
  2016年   917篇
  2015年   821篇
  2014年   958篇
  2013年   1799篇
  2012年   1378篇
  2011年   1412篇
  2010年   1188篇
  2009年   1133篇
  2008年   1280篇
  2007年   1197篇
  2006年   844篇
  2005年   711篇
  2004年   507篇
  2003年   487篇
  2002年   436篇
  2001年   348篇
  2000年   338篇
  1999年   458篇
  1998年   2308篇
  1997年   1401篇
  1996年   999篇
  1995年   588篇
  1994年   488篇
  1993年   449篇
  1992年   185篇
  1991年   181篇
  1990年   160篇
  1989年   160篇
  1988年   149篇
  1987年   166篇
  1986年   141篇
  1985年   221篇
  1984年   189篇
  1983年   166篇
  1982年   140篇
  1981年   180篇
  1980年   173篇
  1979年   128篇
  1978年   108篇
  1977年   230篇
  1976年   491篇
  1975年   91篇
  1973年   119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Nickel (Ni)–Tungsten (W) alloys were electrodeposited galvanostatically (at–10 mA cm–2) on copper substrate with 3 different W contents under the controlled hydrodynamic conditions and then the anodic dissolution behaviors of the alloys were observed by potentiodynamic polarization and electrochemical quartz crystal microbalance (EQCM) techniques. While the structure of the electrodeposited Ni–W alloy with low W content (15.90% W) was crystalline, that of the alloy with high W content (50.80% W) was nano-crystalline according to X-ray diffraction patterns. The increase in the W content of the electrodeposited Ni–W alloy resulted decrease at pH 3 and increase at pH 7 and 12.5 in the anodic currents of the alloy. The pH dependent dissolutions caused electrodeposited alloy surface to have W—enrichment at pH 3 and Ni—enrichment at pH 7 and 12.5. These observations indicated that the selective dissolution of Ni or W was the main mechanism in the anodic dissolution of the electrodeposited Ni–W alloys. The EQCM experiments conducted at pH 7 supported the presence of the selective dissolution mechanism that the anodic dissolution potential of W was 0.42 V lower than that of Ni in the electrodeposited Ni–W alloys.  相似文献   
994.
Minds and Machines - In this paper, we show that reproducibility is a severe problem that concerns simulation models. The reproducibility problem challenges the concept of numerical solution and...  相似文献   
995.
Software and Systems Modeling - Engineers commonly use paper and whiteboards to sketch and discuss ideas in early phases of requirements elicitation and software modeling. These physical media...  相似文献   
996.
In this paper, we analyse a systematically designed and easily tunable backstepping-based boundary control concept for a gantry crane with heavy chain and payload. The corresponding closed-loop system is formulated as an abstract evolution equation in an appropriate Hilbert space. Non-restrictive conditions for the controller coefficients are derived, under which the solutions are described by a C0-semi-group of contractions, and are asymptotically stable. Moreover, by applying Huang's theorem we can finally even show that under these conditions the controller renders the closed-loop system exponentially stable.  相似文献   
997.
Recently, food recommender systems have received increasing attention due to their relevance for healthy living. Most existing studies on the food domain focus on recommendations that suggest proper food items for individual users on the basis of considering their preferences or health problems. These systems also provide functionalities to keep track of nutritional consumption as well as to persuade users to change their eating behavior in positive ways. Also, group recommendation functionalities are very useful in the food domain, especially when a group of users wants to have a dinner together at home or have a birthday party in a restaurant. Such scenarios create many challenges for food recommender systems since the preferences of all group members have to be taken into account in an adequate fashion. In this paper, we present an overview of recommendation techniques for individuals and groups in the healthy food domain. In addition, we analyze the existing state-of-the-art in food recommender systems and discuss research challenges related to the development of future food recommendation technologies.  相似文献   
998.
999.
Geosynthetic Encased Sand Columns (GEC) have been frequently adopted in geo-engineering practice to improve bearing capacity, reduce settlements and accelerate consolidation in saturated soft cohesive ground (e.g. Alexiew et al, 2005; Alexiew et al., 2012; Raithel et al, 2005). The present paper extends these early views by introducing the use of columns to reduce the magnitude of horizontal earth pressures acting on structures adjacent to compaction fills. The monitoring program of a full-scale bridge abutment on soft soil supported by GECs and geogrid reinforced system is described, where field performance is monitored with pressure cells, electrical piezometers, inclinometers and settlement plates. Analytical and numerical analyses have been performed to help on interpreting experimental measurements. The collected database is interpreted to demonstrate that GEC can reduce by up to 50% the horizontal earth pressure over bridge border foundation piles when compared to values predicted for unreinforced ground and demonstrate that the work conformed to acceptable limits of behavior.  相似文献   
1000.
Industrial production systems and industrially manufactured products are constantly evolving due to technical innovations and customers’ demands. Therefore, ensuring an optimized co-evolution of both becomes an important yet challenging task. Approaches for model-based systems engineering have been widely investigated and have already had significant impact on industrial practice. However, existing model-based approaches mostly are focusing on particular aspects of a production system and do not provide a holistic approach for optimizing automated production systems, their deployment, and their co-evolution with the product. As a first step towards this direction, this contribution proposes the combination of an engineering approach for aPS based on systems modeling language with models and techniques for deployment of software and hardware to cyber-physical system architectures, which have been investigated in the field of computer science, and motivates the possibilities of a combined approach.  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