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   878篇
  免费   25篇
电工技术   1篇
化学工业   110篇
金属工艺   1篇
机械仪表   15篇
建筑科学   54篇
矿业工程   4篇
能源动力   6篇
轻工业   115篇
水利工程   14篇
石油天然气   1篇
无线电   25篇
一般工业技术   89篇
冶金工业   336篇
原子能技术   1篇
自动化技术   131篇
  2022年   8篇
  2021年   21篇
  2020年   11篇
  2019年   6篇
  2018年   15篇
  2017年   14篇
  2016年   15篇
  2015年   15篇
  2014年   17篇
  2013年   55篇
  2012年   30篇
  2011年   61篇
  2010年   59篇
  2009年   33篇
  2008年   55篇
  2007年   43篇
  2006年   46篇
  2005年   35篇
  2004年   33篇
  2003年   39篇
  2002年   28篇
  2001年   21篇
  2000年   25篇
  1999年   23篇
  1998年   20篇
  1997年   19篇
  1996年   13篇
  1995年   10篇
  1994年   12篇
  1993年   14篇
  1992年   8篇
  1991年   2篇
  1990年   6篇
  1989年   9篇
  1988年   7篇
  1987年   12篇
  1986年   11篇
  1985年   9篇
  1984年   4篇
  1983年   6篇
  1982年   5篇
  1981年   2篇
  1979年   4篇
  1978年   3篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1974年   2篇
  1973年   2篇
  1971年   3篇
排序方式: 共有903条查询结果,搜索用时 15 毫秒
21.
In this paper, we present the building of various language resources for a multi-engine bi-directional English-Filipino Machine Translation (MT) system. Since linguistics information on Philippine languages are available, but as of yet, the focus has been on theoretical linguistics and little is done on the computational aspects of these languages, attempts are reported here on the manual construction of these language resources such as the grammar, lexicon, morphological information, and the corpora which were literally built from almost non-existent digital forms. Due to the inherent difficulties of manual construction, we also discuss our experiments on various technologies for automatic extraction of these resources to handle the intricacies of the Filipino language, designed with the intention of using them for the MT system. To implement the different MT engines and to ensure the improvement of translation quality, other language tools (such as the morphological analyzer and generator, and the part of speech tagger) were developed.  相似文献   
22.
OBJECTIVE: To explore the effects of contrast reduction on younger and older adults' reading behavior and to examine whether readers rely on word predictability to compensate for poor contrast. BACKGROUND: Poor contrast can degrade text and may influence reading behavior. Readers may compensate for visual degradation of text by taking advantage of word predictability. METHOD: In Experiment 1, 5 younger and 5 older adults read sentences presented with 10 levels of contrast. In Experiment 2, 40 younger and 40 older adults read high-, medium-, and low-contrast sentences that varied in target word predictability (high vs. low). RESULTS: Relative to those of younger adults, older adults' reading rates were more slowed by low contrast; comprehension was less influenced by contrast (i.e., not significantly). Older adults read high-predictability words faster and comprehended them better than low-predictability words, significantly so for high- and medium-contrast sentences. Younger adults comprehended high-predictability words significantly better than low-predictability words for high- and low-contrast sentences. CONCLUSION: Low contrast was more detrimental for older adults. High-predictability words benefited older adults by significantly reducing their reading times and benefited all readers by significantly increasing their comprehension. APPLICATION: The current findings demonstrate the benefit of adequate contrast and word predictability for optimal text design to facilitate both reading times and reading comprehension.  相似文献   
23.
The MANDAS project has defined a layered architecture for the management of distributed applications. In this paper we examine a vertical slice of this architecture, namely the management applications and services related to configuration management. We introduce an information model which captures the configuration information for distributed applications and discuss a repository service based on the model. We define a set of services and management applications to support maintenance of configuration information, and describe how the different types of configuration information are collected. Finally, we present two management applications that use configuration information.  相似文献   
24.
Stroke is associated with the intracerebral formation of fibrin clots which may lead to irreversible brain damage. Thrombolytic therapies employ a variety of natural and/or recombinant plasminogen activators to initiate fibrinolytic degradation of cerebral thrombi. However, such therapies when installed beyond 4‐ to 6‐h window, may fail to achieve the expected outcome. This is due to the hydroxyl radical‐induced modification of fibrin(ogen) molecules rendering them refractory to fibrinolytic degradation, but no cause of the increased free radical generation in stroke was offered. Here, we show by means of electron microscopy that iron ions added to human blood dramatically enhances fibrin fibers formation with thrombin, and significantly delays fibrinolysis during spontaneous clotting of native blood. Iron ions caused the appearance dense matted fibrin deposits, similar, if not identical, to those observed in plasma of patients with stroke. These results may explain a known relationship between thrombotic diseases and the increased body concentrations of free iron and/or hemoglobin derivatives. We conclude that any action resulting in the inhibition of hemostatic abnormalities, as well as in the reduction of body free iron and scavenging of hydroxyl radicals (e.g., by polyphenols) can potentially prevent pathological reactions associated with consequences of stroke. Microsc. Res. Tech. 75:1185–1190, 2012. © 2012 Wiley Periodicals, Inc.  相似文献   
25.
The design of and training for complex systems requires in-depth understanding of task demands imposed on users. In this project, we used the knowledge engineering approach (Bowles et al., 2004) to assess the task of mowing in a citrus grove. Knowledge engineering is divided into four phases: (1) Establish goals. We defined specific goals based on the stakeholders involved. The main goal was to identify operator demands to support improvement of the system. (2) Create a working model of the system. We reviewed product literature, analyzed the system, and conducted expert interviews. (3) Extract knowledge. We interviewed tractor operators to understand their knowledge base. (4) Structure knowledge. We analyzed and organized operator knowledge to inform project goals. We categorized the information and developed diagrams to display the knowledge effectively. This project illustrates the benefits of knowledge engineering as a qualitative research method to inform technology design and training.  相似文献   
26.
A global inventory of nitric oxide emissions from soils   总被引:15,自引:1,他引:15  
Over 60 published papers reporting field measurements of emissions of nitric oxide (NO) from soil are reviewed, and over 100 annual estimates of NO emissions were made for various types of ecosystems, including agricultural fields. These data were stratified by biome and the mean of each stratum was multiplied by an estimate of the biome area. A few strata were identified as clearly having low NO emissions: montane forests, swamps and marshes, tundra, and temperate forests that are not heavily affected by N deposition. The largest emissions were observed in tropical savanna/woodland, chaparral, and cultivated agriculture, but variation in NO emissions within these strata was also large. Although the stratification scheme fails to partition this within-stratum variation, it does clearly identify these biomes as globally important sources of NO and as areas where more research is needed to investigate within-biome variation in NO emissions. It is too early to tell whether differences in NO emissions between temperate and tropical agriculture are significant, but it is clear that agriculture is an important source of NO and that management practices affect NO emissions. The best current estimate of the global soil source of NO is 21 Tg N yr-1. Adsorption of NOx onto plant canopy surfaces may reduce emissions to the atmosphere to as low as 13 Tg N yr-1, although the absorption effect is probably smaller than this. An error term for the global estimate is difficult to determine, but it is at least ±4 and perhaps as large at ±10 Tg N yr-1. Hence, only modest progress has been made in narrowing uncertainties in the estimate of the global soil source of NO, although some published lower estimates appear unlikely. This inventory reconfirms that the soil source of NO is similar in magnitude to fossil fuel emissions of NOx. Further narrowing of the uncertainty of the estimate of global soil NO emissions will require more sophisticated and carefully chosen stratification schemes to address variation within biomes based on soil fertility, soil texture, climate, and management and will require linking this type of inventory and stratification with mechanistic models.  相似文献   
27.
Participants (N = 216) were administered a differential implicit learning task during which they were trained and tested on 3 maximally distinct 2nd-order visuomotor sequences, with sequence color serving as discriminative stimulus. During training, 1 sequence each was followed by an emotional face, a neutral face, and no face, using backward masking. Emotion (joy, surprise, anger), face gender, and exposure duration (12 ms, 209 ms) were varied between participants; implicit motives were assessed with a picture-story exercise. For power-motivated individuals, low-dominance facial expressions enhanced and high-dominance expressions impaired learning. For affiliation-motivated individuals, learning was impaired in the context of hostile faces. These findings did not depend on explicit learning of fixed sequences or on awareness of sequence-face contingencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
28.
X-ray and electron interactions with matter were used as probes to characterize the structure and chemistry of zirconia-thoria-urania ceramics. The ceramics were prepared by coprecipitation of Zr, Th and U salts. In this study, transmission electron microscopy (TEM) techniques such as energy dispersive X-ray (EDX) analysis and electron energy loss spectroscopy (EELS) complement X-ray diffraction, extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge spectroscopy (XANES), techniques to reveal the phase structure and chemistry. The results from XRD and EDX show that these ceramics separate into a Zr-based phase and an actinide-based phase with low mutual affinity of Th and Zr, as well as partial solubility of U in Zr. The comparison of EELS spectra collected for the ceramics with spectra collected for UO2 and U3O8 reference materials also allow us to assess U oxidation state independently in the two separate phases.  相似文献   
29.
A software architecture is presented that allows client application programs to interact with a DBMS server in a flexible and powerful way, using either direct, volatile messages, or messages sent via recoverable queues. Normal requests from clients to the server and replies from the server to clients can be transmitted using direct or recoverable messages. In addition, an application event notification mechanism is provided, whereby client applications running anywhere on the network can register for events, and when those events are raised, the clients are notified. A novel parameter passing mechanism allows a set of tuples to be included in an event notification. The event mechanism is particularly useful in an active DBMS, where events can be raised by triggers to signal running application programs. Received July 21, 1995 / Accepted May 30, 1996  相似文献   
30.
Photography reached the Ottoman Empire soon after its invention, at about the time that painting began to be practised there as part of a broader project of assimilating aspects of European culture. This was in marked contrast to the situation in Europe, where photography had to contend with visual traditions from which it adopted pictorial conventions and subject matter. Instead of supplanting existing traditions of realistic visual representation, photography in the Ottoman Empire served as a discrete source of inspiration. This paper examines how this inversion of European experience within the Ottoman Empire provides an alternative to dominant narratives of photographic history. If one of the salient characteristics of modernist movements in Western art is their ability to break with tradition, then the adoption of Western practices of representation by artists within the Ottoman Empire may be viewed as a radical modernist success.  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