全文获取类型
收费全文 | 1321篇 |
免费 | 42篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 175篇 |
金属工艺 | 14篇 |
机械仪表 | 11篇 |
建筑科学 | 78篇 |
矿业工程 | 8篇 |
能源动力 | 18篇 |
轻工业 | 130篇 |
水利工程 | 12篇 |
石油天然气 | 1篇 |
无线电 | 122篇 |
一般工业技术 | 160篇 |
冶金工业 | 461篇 |
原子能技术 | 5篇 |
自动化技术 | 150篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 24篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 22篇 |
2016年 | 20篇 |
2015年 | 18篇 |
2014年 | 36篇 |
2013年 | 70篇 |
2012年 | 37篇 |
2011年 | 50篇 |
2010年 | 43篇 |
2009年 | 36篇 |
2008年 | 46篇 |
2007年 | 49篇 |
2006年 | 38篇 |
2005年 | 53篇 |
2004年 | 34篇 |
2003年 | 39篇 |
2002年 | 25篇 |
2001年 | 28篇 |
2000年 | 17篇 |
1999年 | 24篇 |
1998年 | 127篇 |
1997年 | 74篇 |
1996年 | 52篇 |
1995年 | 37篇 |
1994年 | 32篇 |
1993年 | 21篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 15篇 |
1976年 | 14篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有1365条查询结果,搜索用时 15 毫秒
81.
Mackle TR Kay JK Auldist MJ McGibbon AK Philpott BA Baumgard LH Bauman DE 《Journal of dairy science》2003,86(2):644-652
The aim of this study was to investigate the effects of conjugated linoleic acid supplementation on the synthesis of milk fat in pasture-fed Friesian cows. In four cows, a commercial mixture containing 62.3% (wt/vol) conjugated linoleic acid was infused intraabomasally to avoid rumen fermentation and biohydrogenation. The design was a 4 x 4 Latin square in which each cow received infusions of 0, 20, 40, and 80 g/d of conjugated linoleic acid mixture for 4 d. Cows were fed freshly cut ryegrass/white clover pasture ad libitum. Milk fat concentration was decreased by 36, 43, and 62% and milk fat yield was decreased by 32, 36, and 60% by the 20, 40, and 80 g of conjugated linoleic acid/d treatments. Dry matter intake, milk protein concentration, and protein yield were unaffected by treatments; however, milk yield was increased by 11% during the 40-g conjugated linoleic acid/d treatment. The effects of conjugated linoleic acid infusion were most pronounced in reducing de novo fatty acid synthesis and desaturation. Results show that the inhibitory effect of this conjugated linoleic acid mixture on milk fat synthesis occurs in pasture-fed cows, and demonstrate the potential to dramatically alter gross milk composition. This technology could offer a management tool to manipulate milk composition and energy demands of pasture-fed cows. 相似文献
82.
Richter Susanne A.; Stubenrauch Kay; Lilie Hauke; Rudolph Rainer 《Protein engineering, design & selection : PEDS》2001,14(10):775-783
The de novo design of a molecular adapter for directed associationand covalent linkage of two polypeptides is presented. Usingpeptides containing charged amino acid residues and an additionalcysteine residue (AlaCysLys8 and AlaCysGlu8) we demonstratethat the electrostatic interaction promotes the associationof two synthetic peptides and, subsequently, disulfide bondformation. The reaction depends on both the redox potentialand on the ionic strength of the buffer. Varying the redox potential,the interaction of the peptides was quantified by a G0' of 6.6± 0.2 kcal/mol. Heterodimerization of the peptides ishighly specific, a competition of association by other cysteinecontaining compounds could not be observed. Two proteins comprisingcysteine-containing polyionic fusion peptides, a modified Fabfragment and an -glucosidase fusion, could be specifically conjugatedby directed association and subsequent disulfide bond formation.Both proteins retain their functional characteristics withinthe bifunctional conjugate: enzymatic activity of the glucosidaseand antigen-binding capacity of the Fab fragment are equivalentto the non-conjugated components. 相似文献
83.
Take care! The evaluation of a team-based burnout intervention program for oncology care providers. 总被引:1,自引:0,他引:1
Le Blanc Pascale M.; Hox Joop J.; Schaufeli Wilmar B.; Taris Toon W.; Peeters Maria C. W. 《Canadian Metallurgical Quarterly》2007,92(1):213
In this quasi-experimental study among staff of 29 oncology wards, the authors evaluated the effects of a team-based burnout intervention program combining a staff support group with a participatory action research approach. Nine wards were randomly selected to participate in the program. Before the program started (Time 1), directly after the program ended (Time 2), and 6 months later (Time 3), study participants filled out a questionnaire on their work situation and well-being. Results of multilevel analyses showed that staff in the experimental wards experienced significantly less emotional exhaustion at both Time 2 and Time 3 and less depersonalization at Time 2, compared with the control wards. Moreover, changes in burnout levels were significantly related to changes in the perception of job characteristics over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
84.
Kay C. Dee 《工程教育杂志》2007,96(1):69-78
Many engineering faculty believe that when students perceive a course to have a high workload, students will rate the course and the performance of the course instructor poorly. This belief can be particularly worrying to engineering faculty since engineering courses are often perceived as uniquely demanding. The present investigation demonstrated that student ratings of workload and of overall instructor performance in engineering courses were not correlated (e.g., Spearman's rho = 0.068) in data sets from either of two institutions. In contrast, a number of evaluation items were strongly correlated (Spearman's rho = 0.7 to 0.899) with ratings of overall instructor performance across engineering, mathematics and science, and humanities courses. The results of the present study provide motivation for faculty seeking to improve their teaching and course evaluations to focus on teaching methods, organization/preparation, and interactions with students, rather than course workload. 相似文献
85.
Many alternative theories about organization exist. Despite this, or perhaps because of it, adequate explanation of the relationship between macro and micro processes of organization, and organizational dynamics remains elusive. In the recent past there has been growing interest in two areas of systems science that offer a different basis for understanding the generative and dynamic qualities of organizations. These are autopoietic theory and complex adaptive systems theory. In this paper, we outline a theory of organization built on a synthesis of these two theoretical strands. It is argued that the approach provides an improved framework for understanding the nature and dynamics of organizational phenomena, and as such a more rigorous basis upon which to base future organizational research. 相似文献
86.
Robert Kay 《国际通用系统杂志》2013,42(5):515-530
In this paper, I will discuss the application of Maturana and Varela's theories of autopoiesis, cognition and language to the notions of worldview, worldview change and curriculum design. The context for this discussion is the education of systems concepts, thinking and practice. It has been argued that systemic thinking requires the adoption of particular assumptions into the worldview of the student, independent of the systems concepts under study. This raises the question of how best to structure a curriculum to meet this end. It will be argued that autopoietic theory, when applied to systems education has significant implications for curriculum design. 相似文献
87.
The generalized likelihood ratio test (GLRT) is widely used in signal processing applications such as image processing, wireless communications, medical imaging, classification, and signal detection. However, the GLRT does not have many known properties, other than that it is invariant, uniformly most powerful invariant (UMPI) for problems that fit the linear model, and asymptotically (N/spl rarr//spl infin/) UMPI in general. Since it is invariant, it belongs to the class of tests for which the UMPI test is optimal. In this paper, we consider a general class of detection problems in which unknown signal parameters imply a problem invariance that can be described analytically by orthogonal subgroups. This invariance is natural for problems with unknown signal parameters and, for example, include those of the matched subspace detectors of Scharf and Friedlander. We derive the GLRT and UMPI detectors for this general signal class for the case of Gaussian noise. An expression is found that relates the two test statistics showing the UMPI statistic to be the sum of two terms, one of which is the GLRT. Using this, we find that the GLRT and UMPI tests are asymptotically equivalent as signal-to-noise ratio (SNR) approaches infinity (or as probability of false alarm approaches zero). These results are illustrated by extending an example given by Nicolls and de Jager to show the analytic relationship between the GLRT and UMPI tests. The results indicate that the performance between the tests becomes close at signal-to-noise ratios (SNRs) associated with operating points of the receiver operating curve that are typically of interest in signal detection applications. 相似文献
88.
André Pohlmann Marc Leßmann Andreas Fritschi Thomas Finocchiaro Ulrich Steinseifer Kay Hameyer 《Mechatronics》2013,23(2):222-226
In industrialized countries cardiovascular diseases are the major cause of death. Beside heart transplants, which are a limited option due to the limited number of available human donor hearts, Total Artificial Hearts (TAHs) are the only therapy available for some patients with terminal heart diseases. For various reasons a total implantable artificial heart is desirable, but also sets restrictions in terms of weight and dimensions due to the limited space in the human thorax. Therefore a precise requirement profile is needed for the drive design to provide sufficient force for the blood pump and to avoid oversizing of the drive and to prevent blood damage by overheating. 相似文献
89.
Fincham Frank D.; Cui Ming; Braithwaite Scott; Pasley Kay 《Canadian Metallurgical Quarterly》2008,20(3):260
Prevention of intimate partner violence on college campuses includes programs designed to change attitudes, and hence, a scale that assesses such attitudes is needed. Study 1 (N = 859) cross validates the factor structure of the Intimate Partner Violence Attitude Scale-Revised using exploratory factor analysis and presents initial validity data on the scale. In Study 2 (N = 687), the obtained three-factor structure (Abuse, Control, Violence) is tested using confirmatory factor analysis, and it is shown to be concurrently related to assault in romantic relationships and to predict psychological aggression 14 weeks later. The findings are discussed in the context of how understanding and modifying attitudes assessed by the Intimate Partner Violence Attitude Scale-Revised may improve interventions aimed at reducing intimate partner violence. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
90.
In a recently completed research project for the Illinois Department of Transportation, the potential service life of each noise barrier material or product currently in use by the Department was evaluated based on the current condition of the barriers in service. The assessment was made by field observation of a majority of the noise barriers in Illinois, and by surveying highway maintenance personnel regarding their observations and experiences with noise barriers in their jurisdictions. The accurate estimation of service life is a necessary component of life-cycle cost analysis of noise barriers, an additional outcome of the research. 相似文献