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   1144篇
  免费   21篇
电工技术   3篇
综合类   3篇
化学工业   287篇
金属工艺   15篇
机械仪表   16篇
建筑科学   79篇
矿业工程   28篇
能源动力   42篇
轻工业   134篇
水利工程   13篇
石油天然气   6篇
无线电   48篇
一般工业技术   150篇
冶金工业   175篇
原子能技术   9篇
自动化技术   157篇
  2022年   6篇
  2021年   5篇
  2020年   13篇
  2019年   11篇
  2018年   20篇
  2017年   13篇
  2016年   16篇
  2015年   17篇
  2014年   11篇
  2013年   82篇
  2012年   28篇
  2011年   56篇
  2010年   36篇
  2009年   30篇
  2008年   61篇
  2007年   44篇
  2006年   43篇
  2005年   32篇
  2004年   27篇
  2003年   30篇
  2002年   41篇
  2001年   17篇
  2000年   26篇
  1999年   21篇
  1998年   34篇
  1997年   20篇
  1996年   26篇
  1995年   24篇
  1994年   23篇
  1993年   18篇
  1992年   11篇
  1991年   12篇
  1990年   11篇
  1989年   16篇
  1988年   12篇
  1987年   15篇
  1986年   14篇
  1985年   16篇
  1984年   16篇
  1983年   23篇
  1982年   18篇
  1981年   20篇
  1980年   20篇
  1979年   17篇
  1978年   14篇
  1977年   10篇
  1976年   15篇
  1975年   13篇
  1974年   6篇
  1973年   9篇
排序方式: 共有1165条查询结果,搜索用时 15 毫秒
71.
This paper examines security of supply concerns in an Australian electricity market under transition and considers potential policy pathways to address them. It details the current state of Australia’s electricity industry, considers the extent to which supply security in the electricity sector may be considered a public good, and examines the features likely to impact on the efficacy of current and potential future market designs.  相似文献   
72.
Synthesis, structure, and properties of rigid‐rod polymers with special emphasis on poly(p‐phenylene benzobisoxazole) (PBO) and poly(p‐phenylene benzobisthiazole) (PBZT) have been reviewed. Recent studies on chemical modifications and molecular simulations have also been given. After nearly 20 years of research and development, PBO fiber was commercialized in the late 1990s. However, due to processing difficulties, the concept of the so called molecular composites has not been successful. Development of the high compressive strength M5 and dihydroxy‐PBI fibers clearly suggest that there is potential for further developing properties of this class of materials. Opto‐electronic properties have also been reviewed.

Synthesis of PBZT.  相似文献   

73.
Carbamoyl chlorides are important intermediates, both in the research laboratory and in industrial scale syntheses. The most studied and used are the disubstituted derivatives, incorporating either aryl or alkyl groups (Ar2NCOCl or R2NCOCl). Sometimes, the groups are tied back to give a ring and piperidino- and morpholino-derivatives are commonly encountered. Some studies have been made with two different groups attached. Solvolyses tend to occur at the carbonyl carbon, with replacement of the chloride ion. Studies of both rate and products are reviewed and the solvolysis reactions are usually SN1, although addition of an amine leads to a superimposable bimolecular component. Many of the studies under solvolytic conditions include the application of the extended Grunwald–Winstein equation. The monosubstituted derivatives (ArNHCOCl or RNHCOCl) are less studied. They are readily prepared by the addition of HCl to an isocyanate. In acetonitrile, they decompose to set up and reach equilibrium with the isocyanate (ArNCO or RNCO) and HCl. Considering that the structurally related formyl chloride (HOCOCl) is highly unstable (with formation of HCl + CO2), the unsubstituted carbamoyl chloride (H2NCOCl) is remarkably stable. Recommended synthetic procedures require it to survive reaction temperatures in the 300–400 °C range. There has been very little study of its reactions.  相似文献   
74.
75.
Abstract. Eliciting information about organizational culture is an important part of system analysis and design. However, eliciting knowledge of this sort is difficult. Laddering is an established technique that is particularly suitable for eliciting information about goals and for eliciting explanations, which are important issues when investigating organizational culture. This paper describes the method, its strengths and limitations, its use in several case studies and its relation to other elicitation techniques. Recommendations for further work are given.  相似文献   
76.
This research tests and develops the Technology Acceptance Model (TAM), introduced by Davis (1986), which attempts to explain end users' attitudes to computing technologies. It introduces several new variables, including compatibility, user characteristics, system rating and the enduser computing satisfaction (EUCS) construct, a surrogate measure for IT success and acceptance. A questionnaire with over seventy items was completed by a large number of users and LISREL, a technique for modelling a system of structural equations, was used to analyse the responses. The output shows the model as a whole fits the data very well and indicates significant relationships between variables in the model. These results confirm that TAM is a valuable tool for predicting attitudes, satisfaction, and usage from beliefs and external variables. They also show that relative advantage of the system contributed most to attitudes and satisfaction. Compatibility (of the system to the task performed) contributed most to usage and was the most important antecedent of the belief variables, including relative advantage.  相似文献   
77.
Over the last decade, MALDI-MS imaging has been used by researchers to explore areas of proteomics, lipidomics and metabolomics in samples of clinical origin for both targeted and global biomarker analysis. Numerous technological advancements in MS and clinical tissue MS imaging have been accomplished; hence, in this article we aim to critically discuss whether MS imaging has now in fact become a true champion of the ‘Omics Era’. In order to assess the potential for it to be routinely used in the clinical setting, it is pertinent to discuss some of its limitations, and to examine how these have been addressed by researchers. The key limitations of the technique we will discuss in this viewpoint article are as follows: sample throughput; relevance to patients, the availability of validated/standardised techniques; and integration with conventional pathology and other medical imaging techniques. Good progress has been made over the last 5 years in overcoming these limitations that had previously restricted the use of this technology in the clinical setting.  相似文献   
78.
79.
Within the medical domain there are clear expectations as to how a patient should respond to treatments administered. When these responses are not observed it can be challenging for clinicians to understand the anomalous responses. The work reported here describes a tool which can detect anomalous patient responses to treatment and further suggest hypotheses to explain the anomaly. In order to develop this tool, we have undertaken a study to determine how Intensive Care Unit (ICU) clinicians identify anomalous patient responses; we then asked further clinicians to provide potential explanations for such anomalies. The high level reasoning deployed by the clinicians has been captured and generalised to form the procedural component of the ontology-driven tool. An evaluation has shown that the tool successfully reproduced the clinician’s hypotheses in the majority of cases. Finally, the paper concludes by describing planned extensions to this work.  相似文献   
80.
This paper considers the design of feedback controllers for linear, time-invariant, spatially distributed systems in an approach which generalises the H-framework and in particular the H loop-shaping method. To this end, we introduce a class of spatially distributed system models called finite dimensional, distributed, linear, time-invariant systems. Sensors and actuators are considered to be part of the controller, rather than part of the plant, and thus the controller we wish to design is itself a spatially distributed system. Optimising over placements and shapes of the sensor and actuator spatial distribution functions is an integrated part of the controller design procedure. As an illustrative design example, we present the feedback stabilisation of an electrostatically destabilised, electrically conducting membrane.  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