全文获取类型
收费全文 | 1682篇 |
免费 | 47篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 12篇 |
综合类 | 6篇 |
化学工业 | 306篇 |
金属工艺 | 25篇 |
机械仪表 | 21篇 |
建筑科学 | 130篇 |
矿业工程 | 1篇 |
能源动力 | 15篇 |
轻工业 | 214篇 |
水利工程 | 28篇 |
石油天然气 | 4篇 |
无线电 | 69篇 |
一般工业技术 | 248篇 |
冶金工业 | 512篇 |
原子能技术 | 8篇 |
自动化技术 | 134篇 |
出版年
2023年 | 13篇 |
2022年 | 26篇 |
2021年 | 41篇 |
2020年 | 19篇 |
2019年 | 30篇 |
2018年 | 38篇 |
2017年 | 27篇 |
2016年 | 35篇 |
2015年 | 16篇 |
2014年 | 32篇 |
2013年 | 89篇 |
2012年 | 70篇 |
2011年 | 120篇 |
2010年 | 85篇 |
2009年 | 77篇 |
2008年 | 91篇 |
2007年 | 91篇 |
2006年 | 76篇 |
2005年 | 74篇 |
2004年 | 64篇 |
2003年 | 65篇 |
2002年 | 56篇 |
2001年 | 33篇 |
2000年 | 22篇 |
1999年 | 22篇 |
1998年 | 73篇 |
1997年 | 40篇 |
1996年 | 40篇 |
1995年 | 18篇 |
1994年 | 23篇 |
1993年 | 23篇 |
1992年 | 15篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1969年 | 5篇 |
1967年 | 6篇 |
排序方式: 共有1733条查询结果,搜索用时 15 毫秒
1.
Bond Gary R.; Dietzen Laura L.; McGrew John H.; Miller Larry D. 《Canadian Metallurgical Quarterly》1995,40(2):75
Tested the hypothesis that Ss with severe mental illnesses would achieve better vocational outcomes with an accelerated approach to supported employment (AASE), as compared to gradual approaches (GA) with prevocational training. 86 Ss (mean age 35.1 yrs) with a diagnosis of a serious mental illness, were randomly assigned to either the AASE, or the GA, which included a minimum of 4 mo prevocational training. Data were obtained on indicators of vocational outcomes over 2 yrs, and for a limited number of Ss (n=36), during the 4th yr of inception into the program. Initially, only 5% of Ss preferred prevocational training. After 1 yr, AASE Ss showed better outcomes for a range of indicators, including achievement of competitive employment, duration of employment and mean earnings. During the 4th yr, 59% of these Ss were competitively employed, as compared to only 6% of GA Ss. Rehabilitation is more effective using AASE than GA. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
The National Research Council (NRC) recently published a report. Science and Judgment in Risk Assessment, that critiqued the current approaches to characterizing human cancer risks from exposure to chemicals. One issue raised in the report relates to the use of default options for quantitation of cancer risks. Default options are general guidelines that can be used for risk assessment when specific information about a chemical is absent. Research on 1,3-butadiene represents an interesting case study in which existing knowledge on this chemical indicates that two default options may no longer be tenable: (1) humans are as sensitive as the most sensitive animal species, and (2) the rate of metabolism is a function of body surface area rather than inherent species differences in metabolic capacity. Butadiene, a major commodity chemical used in the production of synthetic rubber, is listed as one of 189 hazardous air pollutants under the 1990 Clean Air Act Amendments. Butadiene is a carcinogen in rats and mice, with mice being substantially more sensitive than rats. The extent to which butadiene poses a cancer risk to humans exposed to this chemical is uncertain. Butadiene requires metabolic activation to DNA-reactive epoxides to exert its mutagenic and carcinogenic effects. Research is directed toward obtaining a better understanding of the cancer risks of butadiene in humans by evaluating species-dependent differences in the formation of the toxic butadiene epoxide metabolites, epoxybutene and diepoxybutane. The data include in-vitro studies on butadiene metabolism using tissues from humans, rats, and mice as well as experimental data and physiological model predictions for butadiene in blood and butadiene epoxides in blood, lung, and liver after exposure of rats and mice to inhaled butadiene. The findings suggest that humans are more like rats and less like mice regarding the formation of butadiene epoxides. The research approach employed can be a useful strategy for developing mechanistic and toxicokinetic data to supplant default options used in carcinogen risk assessments for butadiene. 相似文献
3.
4.
我非常能理解每当发烧友拥有新器材的那种冲动和兴奋的心情,特别是当您面对这样一部技术先进、功能齐全,Dolby Digital、Dolby Digital(AC-3)-ES、dts、 相似文献
5.
Heather J. Avens 《Polymer》2008,49(22):4762-4768
Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eightfold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from fivefold lower eosin surface densities (2.8 versus 14 eosins/μm2) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities. 相似文献
6.
We present formal definitions of anonymity properties for voting protocols using the process algebra CSP. We analyse a number of anonymity definitions, and give formal definitions for strong and weak anonymity, highlighting the difference between these definitions. We show that the strong anonymity definition is too strong for practical purposes; the weak anonymity definition, however, turns out to be ideal for analysing voting systems. Two case studies are presented to demonstrate the usefulness of the formal definitions: a conventional voting system, and Prêt à Voter, a paper-based, voter-verifiable scheme. In each case, we give a CSP model of the system, and analyse it against our anonymity definitions by specification checks using the Failures-Divergences Refinement (FDR2) model checker. We give a detailed discussion on the results from the analysis, emphasizing the assumptions that we made in our model as well as the challenges in modelling electronic voting systems using CSP. 相似文献
7.
Jo Towers Jennifer Hall Tina Rapke Lyndon C. Martin Heather Andrews 《Canadian Journal of Science, Mathematics, & Technology Education》2013,13(3):152-164
ABSTRACTIn this article, we review published literature that draws on autobiographical accounts of students' experiences learning mathematics. We summarize the main findings of the target literature and present recommendations for further research that will extend this field. Our review indicates that autobiographical and narrative methodological approaches have the potential to occasion important advances in our knowledge of students' experiences learning mathematics. However, relative to accounts of preservice teacher learning, there is a paucity of published research that documents the mathematics learning experiences of kindergarten to Grade 12 students. 相似文献
8.
9.
Distance learning's interfaces—from corresponding through the postal service to the televised talking head—have traditionally been designed from the top down, supporting banking models of learning or, in writing instruction, current-traditional rhetoric pedagogies. Due to temporal and spatial constraints, these interface designs often support (or encourage) one-way communication from the instructor to the student. Students mostly interact with the instructor by asking questions or submitting work, and they tend to have little correspondence with other peers. These methods clearly privilege the instructor's knowledge and evaluation. Furthermore, these interface designs empower the instructor to gaze upon the students and assess them—often not as a corporeal body but as a corpus of texts. Thus, each interface adopted for distance learning sets up a power dynamic in which the capability to share the roles of creating knowledge is juxtaposed with the instructor's capability to normalize the students and reify their own authority through their gaze. In this article we examine the traditional classroom interface through the correspondence course interface, the simulated classroom interface, and the synchronous video interface to raise questions about the infrastructures of distance learning and their implications for student learning. 相似文献
10.
Essential role of beta-adrenergic receptor kinase 1 in cardiac development and function 总被引:1,自引:0,他引:1