全文获取类型
收费全文 | 3752篇 |
免费 | 105篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 22篇 |
综合类 | 4篇 |
化学工业 | 709篇 |
金属工艺 | 66篇 |
机械仪表 | 48篇 |
建筑科学 | 158篇 |
矿业工程 | 8篇 |
能源动力 | 73篇 |
轻工业 | 311篇 |
水利工程 | 29篇 |
石油天然气 | 11篇 |
无线电 | 286篇 |
一般工业技术 | 453篇 |
冶金工业 | 1305篇 |
原子能技术 | 14篇 |
自动化技术 | 363篇 |
出版年
2022年 | 48篇 |
2021年 | 71篇 |
2020年 | 41篇 |
2019年 | 44篇 |
2018年 | 54篇 |
2017年 | 45篇 |
2016年 | 54篇 |
2015年 | 48篇 |
2014年 | 82篇 |
2013年 | 182篇 |
2012年 | 113篇 |
2011年 | 131篇 |
2010年 | 94篇 |
2009年 | 104篇 |
2008年 | 126篇 |
2007年 | 125篇 |
2006年 | 91篇 |
2005年 | 89篇 |
2004年 | 80篇 |
2003年 | 49篇 |
2002年 | 90篇 |
2001年 | 77篇 |
2000年 | 60篇 |
1999年 | 80篇 |
1998年 | 230篇 |
1997年 | 164篇 |
1996年 | 117篇 |
1995年 | 96篇 |
1994年 | 83篇 |
1993年 | 90篇 |
1992年 | 71篇 |
1991年 | 28篇 |
1990年 | 62篇 |
1989年 | 56篇 |
1988年 | 67篇 |
1987年 | 81篇 |
1986年 | 47篇 |
1985年 | 56篇 |
1984年 | 62篇 |
1983年 | 45篇 |
1982年 | 50篇 |
1981年 | 43篇 |
1980年 | 43篇 |
1979年 | 45篇 |
1978年 | 34篇 |
1977年 | 32篇 |
1976年 | 54篇 |
1975年 | 31篇 |
1973年 | 25篇 |
1972年 | 25篇 |
排序方式: 共有3860条查询结果,搜索用时 15 毫秒
51.
We carefully selected a group of chemical engineering scientists internationally recognized as top-scientists in their field. A method has been developed to systematically compare bibliometric characteristics of these top-scientists with an average scientist in chemical engineering. This method also includes citation-analysis of books and proceedings. The results show a very clear bibliometric profile. First, top-scientists references are more numerous and, fourth, they concern more recent literature. Our fifth findings is that the journals used by top-scientists for their publications are representative for the field of chemical engineering as a whole. But they differ in specific aspects significantly from the average journal structure in chemical engineering: the published work of top-scientists is both general as well as more specialistic than the average work in chemical engineering. 相似文献
52.
CG de Koster W Heerma HA Pepermans A Groenewegen H Peters J Haverkamp 《Canadian Metallurgical Quarterly》1995,230(1):135-148
Natural mixtures of sophorolipids produced by the yeast Candida bombicola have been analyzed by fast atom bombardment (FAB)-MS and collision-induced dissociation (CID)-MS. Some pure components have been analysed by two-dimensional NMR spectroscopy. The presence of acidic, lactonic, and O-acetylated forms and the position of double bonds in the fatty acid part of these glycolipids can be easily inferred from positive and negative ion FAB-mass spectra. Details about position of O-acetylation can be obtained from CID mass spectra of [M+H]+ and [M-H]- ions and from the NMR spectra. Differences in CID fragmentation between protonated and sodiated molecular ions are discussed in detail. Enzymatic hydrolysis of 6',6"-di-O-acetyl sophorolipid lactone by cutinase from Fusarium solani results specifically in the removal of the 6'-O-acetyl group, whereas the 6"-O-acetyl and lactone group are resistant. This specificity is explained from a three-dimensional model of the sophorolipid generated on the basis of the short 1H,1H distances as inferred from the NMR (ROESY) spectra. 相似文献
53.
C van Campen HJ Sixma JJ Kerssens L Peters JJ Rasker 《Canadian Metallurgical Quarterly》1998,37(4):362-368
BACKGROUND: Stress can exacerbate a number of psychiatric disorders, many of which are associated with prefrontal cortical (PFC) cognitive deficits. Biochemical studies demonstrate that mild stress preferentially increases dopamine turnover in the PFC. Our study examined the effects of acute, mild stress exposure on higher cognitive function in monkeys and the role of dopaminergic mechanisms in the stress response. METHODS: The effects of loud (105-dB) noise stress were examined on a spatial working memory task (delayed response) dependent on the PFC, and on a reference memory task with similar motor and motivational demands (visual pattern discrimination) dependent on the inferior temporal cortex. The role of dopamine mechanisms was tested by challenging the stress response with agents that decrease dopamine receptor stimulation. RESULTS: Exposure to noise stress significantly impaired delayed-response performance. Stress did not impair performance on "0-second" delay control trials and did not alter visual pattern discrimination performance, which is consistent with impaired PFC cognitive function rather than nonspecific changes in performance. Stress-induced deficits in delayed-response performance were ameliorated by pretreatment with drugs that block dopamine receptors (haloperidol, SCH 23390) or reduce stress-induced PFC dopamine turnover in rodents (clonidine, naloxone hydrochloride). CONCLUSIONS: These results indicate that stress impairs PFC cognitive function through a hyperdopaminergic mechanism. Stress may take the PFC "off-line" to allow more habitual responses mediated by posterior cortical and subcortical structures to regulate behavior. This mechanism may have survival value, but may often be maladaptive in human society, contributing to the vulnerability of the PFC in many neuropsychiatric disorders. 相似文献
54.
Aspects of the mathematical specialty of topology appear within several seemingly distinct areas of engineering design and engineering design theory. Indeed, the expression topology of a design is often used informally. In this article a primary intent is to demonstrate the diversity of applications of topology within engineering design. A complementary goal is to introduce the engineering design community to topology as a rich, formal, well-established mathematical discipline that may be of value for wider study. Upon reviewing some of these topological applications, it appears that topology holds promise as a basis for formalizing engineering design theory. This article considers topology as a basis for unifying design abstractions. The potential benefit may be the realization of commonalities between design aspects previously considered separately, where each now has its own attendant specialized, expensive analyses. 相似文献
55.
Borkin MA Gajos KZ Peters A Mitsouras D Melchionna S Rybicki FJ Feldman CL Pfister H 《IEEE transactions on visualization and computer graphics》2011,17(12):2479-2488
Heart disease is the number one killer in the United States, and finding indicators of the disease at an early stage is critical for treatment and prevention. In this paper we evaluate visualization techniques that enable the diagnosis of coronary artery disease. A key physical quantity of medical interest is endothelial shear stress (ESS). Low ESS has been associated with sites of lesion formation and rapid progression of disease in the coronary arteries. Having effective visualizations of a patient's ESS data is vital for the quick and thorough non-invasive evaluation by a cardiologist. We present a task taxonomy for hemodynamics based on a formative user study with domain experts. Based on the results of this study we developed HemoVis, an interactive visualization application for heart disease diagnosis that uses a novel 2D tree diagram representation of coronary artery trees. We present the results of a formal quantitative user study with domain experts that evaluates the effect of 2D versus 3D artery representations and of color maps on identifying regions of low ESS. We show statistically significant results demonstrating that our 2D visualizations are more accurate and efficient than 3D representations, and that a perceptually appropriate color map leads to fewer diagnostic mistakes than a rainbow color map. 相似文献
56.
This study investigated the online practices of students enrolled in graduate-level distance education courses. Using interviews and a questionnaire as data sources, the study sought to: (a) identify common practices that students adopt in asynchronous discussions, and (b) gain an understanding of why students adopt them. An analysis of the data suggests that many of the practices are coping mechanisms developed to help students more easily meet course participation requirements. Some of these are time saving strategies designed to reduce information overload (e.g., skimming messages rather than reading them carefully). Other strategies are designed to help students project an image of themselves as knowledgeable and collaborative course participants. It is argued that although these practices provide students with a level of efficiency in terms of meeting course requirements, they may inadvertently undermine learning. 相似文献
57.
We introduce a non-uniform subdivision algorithm that partitions the neighborhood of an extraordinary point in the ratio σ:1−σ, where σ(0,1). We call σ the speed of the non-uniform subdivision and verify C1 continuity of the limit surface. For σ=1/2, the Catmull–Clark limit surface is recovered. Other speeds are useful to vary the relative width of the polynomial spline rings generated from extraordinary nodes. 相似文献
58.
Judith Segal 《Computer Supported Cooperative Work (CSCW)》2009,18(5-6):581-606
In earlier work, I identified a particular class of end-user developers, who include scientists and whom I term ‘professional end-user developers’, as being of especial interest. Here, I extend this work by articulating a culture of professional end-user development, and illustrating by means of a field-study how the influence of this culture causes cooperation problems in an inter-disciplinary team developing a software system for a scientific community. My analysis of the field study data is informed by some recent literature on multi-national work cultures. Whilst acknowledging that viewing a scientific development through a lens of software development culture does not give a full picture, I argue that it nonetheless provides deep insights. 相似文献
59.
60.
A Lack of Insight: An Experimental Analysis of R&D Managers’ Decision Making in Innovation Portfolio Management 下载免费PDF全文
Judith Behrens 《Creativity & Innovation Management》2016,25(2):239-250
This study analyses the decision to exploit an innovation project and investigates differences in individuals’ evaluations of project attributes in the context of innovation project portfolio management. A conjoint field experiment was used to collect data on exploitation decisions made by 126 research and development (R&D) managers to test how managers evaluate specific project attributes in the context of innovation project portfolio management. I analyse the relative power and popularity of profitability, strategy, uncertainty and social dimensions of the portfolio while R&D managers exploit an innovation project. Moreover, using social judgement theory, I analyse actual exploitation processes (i.e., the innovation attributes an R&D manager considers while he or she is making an exploitation decision) and self‐reported decision‐making attributes (i.e., managers’ self‐reported data). The data underline that R&D managers value specific project attributes more and others less, and therefore find disparities in innovation project portfolio decision making. Based on this study's results, decision makers are better able to reflect and understand the influence of specific project attributes. Therefore, they should investigate established decision‐making processes which can help them to improve portfolio performance. 相似文献