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   1907篇
  免费   54篇
  国内免费   5篇
电工技术   89篇
化学工业   403篇
金属工艺   61篇
机械仪表   63篇
建筑科学   42篇
能源动力   69篇
轻工业   166篇
水利工程   7篇
无线电   169篇
一般工业技术   328篇
冶金工业   296篇
原子能技术   73篇
自动化技术   200篇
  2023年   11篇
  2022年   35篇
  2021年   40篇
  2020年   19篇
  2019年   40篇
  2018年   37篇
  2017年   26篇
  2016年   48篇
  2015年   36篇
  2014年   44篇
  2013年   118篇
  2012年   82篇
  2011年   114篇
  2010年   96篇
  2009年   78篇
  2008年   93篇
  2007年   77篇
  2006年   85篇
  2005年   68篇
  2004年   61篇
  2003年   35篇
  2002年   39篇
  2001年   25篇
  2000年   34篇
  1999年   40篇
  1998年   122篇
  1997年   64篇
  1996年   68篇
  1995年   44篇
  1994年   42篇
  1993年   33篇
  1992年   18篇
  1991年   18篇
  1990年   28篇
  1989年   27篇
  1988年   17篇
  1987年   10篇
  1986年   19篇
  1985年   15篇
  1984年   10篇
  1983年   7篇
  1982年   4篇
  1981年   7篇
  1980年   11篇
  1978年   2篇
  1977年   4篇
  1976年   5篇
  1975年   5篇
  1967年   1篇
  1966年   1篇
排序方式: 共有1966条查询结果,搜索用时 15 毫秒
11.
A potential barrier model along the grain boundaries in ultrathin tin dioxide (SnO2) gas sensors is presented. It is assumed that the negatively charged oxygens are adsorbed only on the grain boundaries. The potential barrier depth is expressed as functions of grain size, donor concentration and surface coverage of adsorbed oxygen ions at the boundaries. A direct consequence is that the conduction electrons are effectively confined in a grain when the film thickness becomes smaller than a critical value. This indicates a drastic increase in resistivity with decreasing film thickness in air, and thus an occurrence of an extremely high gas sensitivity.  相似文献   
12.
This 512 Kw×8 b×3 way synchronous BiCMOS SRAM uses a 2-stage wave-pipeline scheme, a PLL self-timing generator and a 0.4-μm BiCMOS process to achieve 220 MHz fully-random read/write operations with a GTL I/O interface. Newly developed circuit technologies include: 1) a zig-zag double word-line scheme, 2) a centered bit-line load layout scheme, and 3) a phase-locked-loop (PLL) with a multistage-tapped ring oscillator which generates a clock cycle proportional pulse (CCPP) and a clock edge lookahead pulse (CELP)  相似文献   
13.
14.
15.
Using in situ hybridization techniques, we examined the expression of ornithine decarboxylase (ODC) mRNA in the skin of five patients with systemic sclerosis (SSc) and five normal controls. Sections treated with an anti-sense probe showed concentrated grains exclusively in the epidermis of SSc patients, but not in that of normal controls. Because our subcloned anti-sense probe specifically hybridizes with ODC mRNA, these findings indicate that the expression of ODC mRNA is elevated in SSc epidermis. Possibly polyamines have an important part to play in the skin changes of SSc.  相似文献   
16.
The preparation and characterization of indium oxide (InO x )/tin oxide (SnO y ) multilayered films deposited by ion-beam sputtering are described and compared with indium tin oxide (ITO) films. The structure and the optoelectrical properties of the films are studied in relation to the layered structures and the post-deposition annealing. Low-angle X-ray diffraction analysis showed that most films retained the regular layered structures even after annealing at 500° C for 16 h. As an example, we obtained a resistivity of 6×10–4 cm and a transparency of about 85% in the visible range at a thickness of 110 nm in a multilayered film of InO x (2.0 nm)/SnO y (0.2 nm)×50 pairs when annealed at 300° C for 0.5 h in air. Hall coefficient measurements showed that this film had a mobility of 17 cm2 V–1 sec–1 and a carrier concentration (electron density) of 5×1020 cm–3.  相似文献   
17.
The balanced corpus of contemporary written Japanese (BCCWJ) is Japan’s first 100 million words balanced corpus. It consists of three subcorpora (publication subcorpus, library subcorpus, and special-purpose subcorpus) and covers a wide range of text registers including books in general, magazines, newspapers, governmental white papers, best-selling books, an internet bulletin-board, a blog, school textbooks, minutes of the national diet, publicity newsletters of local governments, laws, and poetry verses. A random sampling technique is utilized whenever possible in order to maximize the representativeness of the corpus. The corpus is annotated in terms of dual POS analysis, document structure, and bibliographical information. The BCCWJ is currently accessible in three different ways including Chunagon a web-based interface to the dual POS analysis data. Lastly, results of some pilot evaluation of the corpus with respect to the textual diversity are reported. The analyses include POS distribution, word-class distribution, entropy of orthography, sentence length, and variation of the adjective predicate. High textual diversity is observed in all these analyses.  相似文献   
18.
The plasmodium of Physarum polycephalum is a unicellular and multinuclear giant amoeba that has an amorphous cell body. To clearly observe how the plasmodium makes decisions in its motile and exploratory behaviours, we developed a new experimental system to pseudo-discretize the motility of the organism. In our experimental space that has agar surfaces arranged in a two-dimensional lattice, the continuous and omnidirectional movement of the plasmodium was limited to the stepwise one, and the direction of the locomotion was also limited to four neighbours. In such an experimental system, a cellular automata-like system was constructed using the living cell. We further analysed the exploratory behaviours of the plasmodium by duplicating the experimental results in the simulation models of cellular automata. As a result, it was revealed that the behaviours of the plasmodium are not reproduced by only local state transition rules; and for the reproduction, a kind of historical rule setting is needed.  相似文献   
19.
Shared protection/restoration is a promising solution for reducing protection resources and is supported at each layer of the current multi-layer networks. Software-defined networking is expected to reduce equipment cost as well as operational cost by orchestrating these shared protection functionalities. However, although protection resource sharing improves link utilization, it sometimes increases the required equipment. Meanwhile, traffic re-aggregation at each layer is an important technique for low volume traffic to utilize the underlying link capacity more efficiently, but re-aggregation also makes it difficult to share protection resources with traffic at lower layers. In this paper, we present multi-layer network design strategy and method that reduce equipment cost by means of both traffic re-aggregation at each layer and protection resource sharing among multiple service traffic at different layers. The strategy first prioritizes traffic re-aggregation at each layer, and then maximally delegates shared protection to lower layers as long as it does not increase the required capacity at the lower layer. Evaluation results from the example three-layer networks confirm that the proposed method can effectively reduce equipment cost compared to the conventional design method. Cost reduction is achieved by leveraging shared protection functions at multiple layers.  相似文献   
20.
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