全文获取类型
收费全文 | 1674篇 |
免费 | 23篇 |
专业分类
电工技术 | 11篇 |
化学工业 | 111篇 |
金属工艺 | 27篇 |
机械仪表 | 33篇 |
建筑科学 | 34篇 |
能源动力 | 5篇 |
轻工业 | 78篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 71篇 |
一般工业技术 | 153篇 |
冶金工业 | 1056篇 |
原子能技术 | 5篇 |
自动化技术 | 105篇 |
出版年
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 15篇 |
2013年 | 28篇 |
2012年 | 23篇 |
2011年 | 32篇 |
2010年 | 17篇 |
2009年 | 23篇 |
2008年 | 24篇 |
2007年 | 36篇 |
2006年 | 46篇 |
2005年 | 26篇 |
2004年 | 27篇 |
2003年 | 20篇 |
2002年 | 22篇 |
2001年 | 23篇 |
2000年 | 23篇 |
1999年 | 53篇 |
1998年 | 297篇 |
1997年 | 161篇 |
1996年 | 112篇 |
1995年 | 66篇 |
1994年 | 49篇 |
1993年 | 55篇 |
1992年 | 25篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 25篇 |
1988年 | 17篇 |
1987年 | 23篇 |
1986年 | 22篇 |
1985年 | 28篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 36篇 |
1976年 | 71篇 |
1975年 | 13篇 |
1972年 | 9篇 |
1971年 | 9篇 |
1967年 | 6篇 |
排序方式: 共有1697条查询结果,搜索用时 911 毫秒
41.
Maeda N Wells D Becker NC Hartley PG Wilson PW Haymet AD Kozielski KA 《The Review of scientific instruments》2011,82(6):065109
Nucleation in a supercooled or a supersaturated medium is a stochastic event, and hence statistical analyses are required for the understanding and prediction of such events. The development of reliable statistical methods for quantifying nucleation probability is highly desirable for applications where control of nucleation is required. The nucleation of gas hydrates in supercooled conditions is one such application. We describe the design and development of a high pressure automated lag time apparatus (HP-ALTA) for the statistical study of gas hydrate nucleation and growth at elevated gas pressures. The apparatus allows a small volume (≈150 μl) of water to be cooled at a controlled rate in a pressurized gas atmosphere, and the temperature of gas hydrate nucleation, T(f), to be detected. The instrument then raises the sample temperature under controlled conditions to facilitate dissociation of the gas hydrate before repeating the cooling-nucleation cycle again. This process of forming and dissociating gas hydrates can be automatically repeated for a statistically significant (>100) number of nucleation events. The HP-ALTA can be operated in two modes, one for the detection of hydrate in the bulk of the sample, under a stirring action, and the other for the detection of the formation of hydrate films across the water-gas interface of a quiescent sample. The technique can be applied to the study of several parameters, such as gas pressure, cooling rate and gas composition, on the gas hydrate nucleation probability distribution for supercooled water samples. 相似文献
42.
Darcy T. Haluzan David M. Klymyshyn Martin Börner Sven Achenbach Garth Wells Timo Mappes Jürgen Mohr 《Microsystem Technologies》2008,14(9-11):1709-1714
High aspect ratio variable capacitors have been fabricated using deep X-ray lithography and electroplating. Stiction phenomena applicable to high aspect ratio devices are presented, including the conditions for stiction to occur and the critical dimensions of structures. Actuation tests at 3 GHz are also presented and show a maximum capacitance of 0.86 pF with no actuation voltage and a minimum capacitance of 0.70 pF with an actuation voltage of 20 V just before pull-in, which gives a tuning range of 1.23:1. Corresponding Q-factor values are 49.3 and 70.8 respectively. After pull-in, the measured capacitance is 0.61 pF, corresponding to a tuning range of 1.41:1, with a maximum Q-factor of 102.9. 相似文献
43.
Subdermal superficial liposuction, first presented by the authors at the ISAPS Congress at Zurich in 1989, is performed with thin three-hole Mercedes cannulas (diameter ranges from 1.8 to 2 mm) to treat small and secondary adiposities and to allow better skin retraction. Suction of the subdermal layer of fat reduces the thickness and consistency of the superficial fat and enhances the possibility of skin retraction. In cases where there is a large adiposity of the abdomen, arms, or inner thighs, there is a conspicuous volume of fat whose weight tends to overstretch and to carry the overlying skin downward. In these cases we need to reduce the large fat volume to permit effective skin retraction. Therefore, we apply the principles of traditional liposuction with those of subdermal superficial liposuction to aspirate large amounts of fat from all the adipose layers. We call this technique Massive All Layer Liposuction (MALL). The amount of skin shrinkage after this "defatting" procedure is remarkable and the clinical results are very good. The MALL technique can be applied to other areas as well. In our experience this new liposuction technique has dramatically reduced the indications of abdominoplasties and dermolipectomies of inner thighs and arms. 相似文献
44.
M. A. Wells I. V. Samarasekera J. K. Brimacombe E. B. Hawbolt D. J. Lloyd 《Metallurgical and Materials Transactions B》1998,29(3):611-620
A comprehensive mathematical model of the hot tandem rolling process for aluminum alloys has been developed. Reflecting the
complex thermomechanical and microstructural changes effected in the alloys during rolling, the model incorporated heat flow,
plastic deformation, kinetics of static recrystallization, final recrystallized grain size, and texture evolution. The results
of this microstructural engineering study, combining computer modeling, laboratory tests, and industrial measurements, are
presented in three parts. In this Part I, laboratory measurements of static recrystallization kinetics and final recrystallized
grain size are described for AA5182 and AA5052 aluminum alloys and expressed quantitatively by semiempirical equations. In
Part II, laboratory measurements of the texture evolution during static recrystallization are described for each of the alloys
and expressed mathematically using a modified form of the Avrami equation. Finally, Part III of this article describes the
development of an overall mathematical model for an industrial aluminum hot tandem rolling process which incorporates the
microstructure and texture equations developed and the model validation using industrial data. The laboratory measurements
for the microstructural evolution were carried out using industrially rolled material and a state-of-the-art plane strain
compression tester at Alcan International. Each sample was given a single deformation and heat treated in a salt bath at 400
°C for various lengths of time to effect different levels of recrystallization in the samples. The range of hot-working conditions
used for the laboratory study was chosen to represent conditions typically seen in industrial aluminum hot tandem rolling
processes, i.e., deformation temperatures of 350 °C to 500 °C, strain rates of 0.5 to 100 seconds and total strains of 0.5 to 2.0. The semiempirical
equations developed indicated that both the recrystallization kinetics and the final recrystallized grain size were dependent
on the deformation history of the material i.e., total strain and Zener-Hollomon parameter (Z), where
and time at the recrystallization temperature. 相似文献
45.
Kai Ming Ting Jonathan R. Wells Swee Chuan Tan Shyh Wei Teng Geoffrey I. Webb 《Machine Learning》2011,82(3):375-397
This paper introduces a new ensemble approach, Feature-Subspace Aggregating (Feating), which builds local models instead of
global models. Feating is a generic ensemble approach that can enhance the predictive performance of both stable and unstable
learners. In contrast, most existing ensemble approaches can improve the predictive performance of unstable learners only.
Our analysis shows that the new approach reduces the execution time to generate a model in an ensemble through an increased
level of localisation in Feating. Our empirical evaluation shows that Feating performs significantly better than Boosting,
Random Subspace and Bagging in terms of predictive accuracy, when a stable learner SVM is used as the base learner. The speed
up achieved by Feating makes feasible SVM ensembles that would otherwise be infeasible for large data sets. When SVM is the
preferred base learner, we show that Feating SVM performs better than Boosting decision trees and Random Forests. We further
demonstrate that Feating also substantially reduces the error of another stable learner, k-nearest neighbour, and an unstable
learner, decision tree. 相似文献
46.
47.
The study aims were, in a population of university students, staff, and faculty (n = 140), to: 1) determine the distribution of seven measures of mobile device use; 2) determine the distribution of musculoskeletal symptoms of the upper extremity, upper back and neck; and 3) assess the relationship between device use and symptoms. 137 of 140 participants (98%) reported using a mobile device. Most participants (84%) reported pain in at least one body part. Right hand pain was most common at the base of the thumb. Significant associations found included time spent internet browsing and pain in the base of the right thumb (odds ratio 2.21, 95% confidence interval 1.02–4.78), and total time spent using a mobile device and pain in the right shoulder (2.55, 1.25–5.21) and neck (2.72, 1.24–5.96). Although this research is preliminary, the observed associations, together with the rising use of these devices, raise concern for heavy users. 相似文献
48.
A participatory ergonomics programme was implemented in an automotive parts manufacturing factory in which an ergonomics change team was formed, composed of members from management, the organized labour union and the research team. It was hypothesized that the participatory nature of this change process would result in enhanced worker perceptions of workplace communication dynamics, decision latitude and influence, which in conjunction with anticipated mechanical exposure reductions would lead to reduced worker pain severity. Utilizing a sister plant in the corporation as a referent group, a quasi-experimental design was employed with a longitudinal, repeat questionnaire approach to document pre-post intervention changes. Nine participatory activities (psychosocial interventions) were implemented as part of the process. Communication dynamics regarding ergonomics were significantly enhanced at the intervention plant compared to the referent plant. However, there were no significantly different changes in worker perceptions of decision latitude or influence between the two plants, nor did pain severity change. Possible explanations for these results include limited intervention intensity, context and co-intervention differences between the two plants, high plant turnover reducing the statistical power of the study and lack of sensitivity and specificity in the psychosocial measures used. Further research should include the development of psychosocial tools more specific to participatory ergonomic interventions and the assessment of the extent of change in psychosocial factors that might be associated with improvements in pain. 相似文献
49.
Assessing Image Features for Vision-Based Robot Positioning 总被引:2,自引:0,他引:2
50.
Day [3] describes an analytical model of minimum-length sequence (MLS) metrics measuring distances between partitions of a set. By selecting suitable values of model coordinates, a user may identify within the model that metric most appropriate to his classification application. Users should understand that within the model similar metrics may nevertheless exhibit extreme differences in their computational complexities. For example, the asymptotic time complexities of two MLS metrics are known to be linear in the number of objects being partitioned; yet we establish below that the computational problem for a closely related MLS metric is NP-complete. 相似文献