全文获取类型
收费全文 | 3607篇 |
免费 | 88篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 46篇 |
综合类 | 23篇 |
化学工业 | 918篇 |
金属工艺 | 83篇 |
机械仪表 | 80篇 |
建筑科学 | 148篇 |
矿业工程 | 16篇 |
能源动力 | 50篇 |
轻工业 | 646篇 |
水利工程 | 7篇 |
石油天然气 | 12篇 |
无线电 | 195篇 |
一般工业技术 | 662篇 |
冶金工业 | 405篇 |
原子能技术 | 25篇 |
自动化技术 | 383篇 |
出版年
2021年 | 51篇 |
2020年 | 43篇 |
2019年 | 44篇 |
2018年 | 45篇 |
2016年 | 68篇 |
2015年 | 56篇 |
2014年 | 70篇 |
2013年 | 101篇 |
2012年 | 110篇 |
2011年 | 146篇 |
2010年 | 117篇 |
2009年 | 118篇 |
2008年 | 118篇 |
2007年 | 114篇 |
2006年 | 107篇 |
2005年 | 110篇 |
2004年 | 97篇 |
2003年 | 54篇 |
2002年 | 74篇 |
2001年 | 58篇 |
2000年 | 69篇 |
1999年 | 75篇 |
1998年 | 126篇 |
1997年 | 100篇 |
1996年 | 68篇 |
1995年 | 75篇 |
1994年 | 69篇 |
1993年 | 54篇 |
1992年 | 64篇 |
1991年 | 40篇 |
1990年 | 36篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 38篇 |
1986年 | 46篇 |
1985年 | 53篇 |
1984年 | 60篇 |
1983年 | 39篇 |
1982年 | 39篇 |
1980年 | 46篇 |
1979年 | 41篇 |
1978年 | 43篇 |
1977年 | 47篇 |
1976年 | 55篇 |
1975年 | 50篇 |
1974年 | 55篇 |
1973年 | 44篇 |
1971年 | 34篇 |
1970年 | 39篇 |
1967年 | 33篇 |
排序方式: 共有3699条查询结果,搜索用时 31 毫秒
91.
Christina Schwind Jürgen Buder Ulrike Cress Friedrich W. Hesse 《Computers & Education》2012,58(2):787-796
The Web is a perfect backdrop for opinion formation as a multitude of different opinions is publicly available. However, the different opinions often remain unexploited: Learners prefer preference-consistent over preference-inconsistent information, a phenomenon called confirmation bias. Two experiments were designed to test whether technologies such as recommender systems can be used to overcome this bias. The role of preference-inconsistent recommendations was explored by comparing their influence to a condition with preference-consistent recommendations and to a control condition without recommendations. In Study 1, preference-inconsistent recommendations led to a reduction of confirmation bias and to a more moderate view of the controversial topic of neuro-enhancement. In Study 2, we found that preference-inconsistent recommendations stimulated balanced recall and divergent thinking. Together these studies showed that preference-inconsistent recommendations are an effective approach for reducing confirmation bias and stimulating divergent thinking. In conclusion, future research and practical implications are discussed. 相似文献
92.
In micron‐sized Ni bicrystals, after compression tests, orientation gradients are measured by electron back scattering diffraction (EBSD). The results clearly show that EBSD can be used to study dislocation pile‐ups at boundaries. Using bicrystals with single and multiple slip orientations our results show that with decreasing the size of the pillars the orientation changes due to cross‐slip decreases and the orientation changes at the boundary increases. This directly indicates a change in the hardening mechanism when the probability of dislocation–dislocation interaction decreases due to source‐limited plasticity in the bicrystals with diameters below approximately two microns. 相似文献
93.
Chemical functionalization of carbon nanotubes (CNT) with nucleophiles requires introduction of electrophilic reactive sites on the CNTs. This can, for instance, be accomplished by the chemical bromination procedure with elemental bromine and a set of Lewis acids (BBr3, BF3 × Et2O, AlBr3, FeBr3, ZnBr2, TiBr4, SiBr4, SnBr4, VBr3) or a radical starter like dibenzoylperoxide (DBPO) in appropriate solvents at varied temperature. The present approach to electrophilic sites relies on the well-known electrophilic aromatic substitution or addition of bromine with aromatic structural units. In addition to the use of bromine, the introduction of haloalkyl groups was also investigated here using bis-electrophiles or haloalcohols and Brønsted acids. The advantages and drawbacks of the studied reaction conditions, the obtained degree of bromination as analyzed by X-ray photoelectron spectroscopy (XPS) and the amount of introduced bromine that can be substituted by a nucleophile are presented and discussed. 相似文献
94.
Physical strain is usually evaluated physiologically by using the heart rate (HR) or psychologically using scaled perceived exertion (PE). In order to explore the relationship between these approaches, we compared the series of both measurements taken simultaneously during work on a bicycle ergometer. A total of 29 participants aged between 27 and 41, 42 and 56, and 57 and 71 years took part in 28 minutes of cycling with systematically increased and decreased load as well as in 7 hours of continuous cycling with low to medium exertion, interrupted by brief peak loads at high to very high exertion levels. Results revealed that, while both measurements are suitable to capture physical strain, HR is not as specific as PE. The older participants further perceived comparable physical loads as more demanding as the younger participants. With an aging workforce, results have potential implications for the organisation of work places. 相似文献
95.
96.
Mohd-Shafie Muhammad Luqman Kadir Wan Mohd Nasir Wan Lichter Horst Khatibsyarbini Muhammad Isa Mohd Adham 《Software and Systems Modeling》2022,21(2):717-753
Software and Systems Modeling - Model-based test case generation (MB-TCG) and prioritization (MB-TCP) utilize models that represent the system under test (SUT) for test generation and... 相似文献
97.
98.
Sonia R. Merritt Agata A. Exner Zhenghong Lee Horst A. von Recum 《Advanced Engineering Materials》2012,14(5):B266-B278
Polymer processing via electrospinning is a cost effective and scalable method for preparing nanofibers with industrial, electrical, and biomedical applications, particularly tissue engineering and drug delivery. Characterization methods for these fibers include microscopy techniques for vitro surface morphology information, spectroscopy methods to determine in vitro chemical composition, and medical imaging tools for in vivo assessment of morphology and efficacy of implanted material. The focus of this paper is be on recent applications for electrospun nanofibers, in vitro characterization methods, and medical imaging modalities that can be used for in vivo assessment of the fibers, as well as insights in how to adapt existing techniques toward the characterization of electrospun materials. 相似文献
99.
100.
The metabolism of 1,8‐cineole after ingestion of sage tea was studied. After application of the tea, the metabolites 2‐hydroxy‐1,8‐cineole, 3‐hydroxy‐1,8‐cineole, 9‐hydroxy‐1,8‐cineole and, for the first time in humans, 7‐hydroxy‐1,8‐cineole were identified in plasma and urine of one volunteer. For quantitation of these metabolites and the parent compound, stable isotope dilution assays were developed after synthesis of [2H3]‐1,8‐cineole, [9/10‐2H3]‐2‐hydroxy‐1,8‐cineole and [13C,2H2]‐9‐hydroxy‐1,8‐cineole as internal standards. Using these standards, we quantified 1,8‐cineole by solid phase microextraction GC‐MS and the hydroxyl‐1,8‐cineoles by LC‐MS/MS after deconjugation in blood and urine of the volunteer. After consumption of 1.02 mg 1,8‐cineole (19 μg/kg bw), the hydroxycineoles along with their parent compound were detectable in the blood plasma of the volunteer under study after liberation from their glucuronides with 2‐hydroxycineole being the predominant metabolite at a maximum plasma concentration of 86 nmol/L followed by the 9‐hydroxy isomer at a maximum plasma concentration of 33 nmol/L. The parent compound 1,8‐cineole showed a low maximum plasma concentration of 19 nmol/L. In urine, 2‐hydroxycineole also showed highest contents followed by its 9‐isomer. Summing up the urinary excretion over 10 h, 2‐hydroxycineole, the 9‐isomer, the 3‐isomer and the 7‐isomer accounted for 20.9, 17.2, 10.6 and 3.8% of the cineole dose, respectively. 相似文献