全文获取类型
收费全文 | 766篇 |
免费 | 16篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 110篇 |
金属工艺 | 10篇 |
机械仪表 | 13篇 |
建筑科学 | 29篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 51篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 108篇 |
一般工业技术 | 126篇 |
冶金工业 | 241篇 |
原子能技术 | 5篇 |
自动化技术 | 64篇 |
出版年
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 18篇 |
2013年 | 29篇 |
2012年 | 25篇 |
2011年 | 29篇 |
2010年 | 20篇 |
2009年 | 30篇 |
2008年 | 29篇 |
2007年 | 36篇 |
2006年 | 37篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 14篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 18篇 |
1999年 | 22篇 |
1998年 | 70篇 |
1997年 | 39篇 |
1996年 | 31篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1983年 | 10篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1976年 | 11篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1969年 | 3篇 |
1967年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有782条查询结果,搜索用时 31 毫秒
81.
82.
Nandan Sudarsanam Daniel D. Frey 《Quality and Reliability Engineering International》2011,27(7):947-957
Ensemble Methods are proposed as a means to extendbiAdaptive One‐Factor‐at‐a‐Time (aOFAT) experimentation. The proposed method executes multiple aOFAT experiments on the same system with minor differences in experimental setup, such as ‘starting points’. Experimental conclusions are arrived at by aggregating the multiple, individual aOFATs. A comparison is made to test the performance of the new method with that of a traditional form of experimentation, namely a single fractional factorial design which is equally resource intensive. The comparisons between the two experimental algorithms are conducted using a hierarchical probability meta‐model and an illustrative case study. The case is a wet clutch system with the goal of minimizing drag torque. In this study, the proposed procedure was superior in performance to using fractional factorial arrays consistently across various experimental settings. At the best, the proposed algorithm provides an expected value of improvement that is 15% higher than the traditional approach; at the worst, the two methods are equally effective, and on average the improvement is about 10% higher with the new method. These findings suggest that running multiple adaptive experiments in parallel can be an effective way to make improvements in quality and performance of engineering systems and also provides a reasonable aggregation procedure by which to bring together the results of the many separate experiments. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
83.
In-use measurement of activity, energy use, and emissions of a plug-in hybrid electric vehicle 总被引:1,自引:0,他引:1
Plug-in hybrid electric vehicles (PHEVs) could reduce transportation air emissions and energy use. However, a method is needed for estimating on-road emissions of PHEVs. To develop a framework for quantifying microscale energy use and emissions (EU&E), measurements were conducted on a Toyota Prius retrofitted with a plug-in battery system on eight routes. Measurements were made using the following: (1) a data logger for the hybrid control system; (2) a portable emissions measurement system; and (3) a global positioning system with barometric altimeter. Trends in EU&E are estimated based on vehicle specific power. Energy economy is quantified based on gasoline consumed by the engine and grid energy consumed by the plug-in battery. Emissions from electricity consumption are estimated based on the power generation mix. Fuel use is approximately 30% lower during plug-in battery use. Grid emissions were higher for CO?, NO(x), SO?, and PM compared to tailpipe emissions but lower for CO and hydrocarbons. EU&E depends on engine and plug-in battery operation. The use of two energy sources must be addressed in characterizing fuel economy; overall energy economy is 11% lower if including grid energy use than accounting only for fuel consumption. 相似文献
84.
JS Bertino S Thoelen P VanDamme JP Bryan PR Becherer S Frey FG Hayden LC Marcus DM Parenti M Sperling IS Chan L Brown D Nalin 《Canadian Metallurgical Quarterly》1998,178(4):1181-1184
The dose response relationship of 25-, 50-, and 100-U doses of an inactivated hepatitis A vaccine was examined in 358-seronegative volunteers in a 2-dose schedule. The 50-U and 100-U groups had statistically significantly higher seroconversion rates than the 25-U group at weeks 2, 4, 8, and 24. Seroconversion was statistically significantly greater for the 100-U compared with the 25- and 50-U doses 2 weeks after the first injection but was not significantly different by 4 weeks after the first injection in the 50- and 100-U dose groups. After 2 injections, all subjects in all groups seroconverted. The vaccine was well tolerated at all dosage levels. 相似文献
85.
T. Mattfeldt V. Schmidt D. Reepschläger C. Rose & H. Frey 《Journal of microscopy》1996,183(2):158-169
Real structures investigated in the material and biological sciences, such as minerals or tissues, can often be reduced to two phases. In a stochastic approach, the components of such binary structures may be considered as the union of grains — random sets implanted with their centres at random points — and their complementary space, which is called the pore space. The simplest stochastic germ-grain model is the Boolean model of random sets, which we use here instrumentally as a null model (reference model) for comparison with our biological material. After a brief review of basic properties of the Boolean model and related statistical methods, we introduce centred contact density functions as a new approach. Empirical contact density functions are estimated from the empirical contact distribution functions with an image analyser by dilation of the grain phase. Theoretical contact density functions are then predicted from a set of image parameters, under the assumption that the Boolean model holds. A centred contact density function is the difference between the estimated and the predicted contact density function. Apart from a random error term, centred contact density functions amount to zero irrespective of the area fraction of the grain phase, when the germ-grain model is Boolean. As a section of a spatial Boolean model is a planar Boolean model, the method is also applicable in stereological studies where digitized images are obtained from sections of a three-dimensional structure. Centred contact density functions were determined for mastopathic tissue as compared to mammary cancer, and for tumour-free prostatic tissue as compared to prostatic cancer. For each category of specimens, twenty cases with 10 images each were analysed. Benign and malignant glandular tissue of the aforementioned types deviates significantly from the Boolean model. Centred contact density functions show that malignant transformation is connected with profound geometric remodelling of the pore space. 相似文献
86.
F Becmeur I Chevalier-Kauffmann G Frey P Sauvage 《Canadian Metallurgical Quarterly》1998,52(10):1060-1063
A new case report of laparoscopic repair of a diaphragmatic hernia through the foramen of Morgagni in a 11-year-old boy with Down's syndrome is described. The review of 11 other cases in the adult literature illustrated the various aspects of this laparoscopic approach. 相似文献
87.
AK Nakashima R Horsley RL Frey PA Sweeney JT Weber PL Fleming 《Canadian Metallurgical Quarterly》1998,280(16):1421-1426
CONTEXT: Policies requiring confidential reporting by name to state health departments of persons infected with the human immunodeficiency virus (HIV) have potential to cause some of them to avoid HIV testing. OBJECTIVE: To describe trends in use of HIV testing services at publicly funded HIV counseling and testing sites before and after the implementation of HIV reporting policies. DESIGN AND SETTING: Analysis of service provision data from 6 state health departments (Louisiana, Michigan, Nebraska, Nevada, New Jersey, and Tennessee) 12 months before and 12 months after HIV reporting was introduced. MAIN OUTCOME MEASURE: Percent change in numbers of persons tested at publicly funded HIV counseling and testing sites after implementation of confidential HIV reporting by risk group. RESULTS: No significant declines in the total number of HIV tests provided at counseling and testing sites in the months immediately after implementation of HIV reporting occurred in any state, other than those expected from trends present before HIV reporting. Increases occurred in Nebraska (15.8%), Nevada (48.4%), New Jersey (21.3%), and Tennessee (62.8%). Predicted decreases occurred in Louisiana (10.5%) and Michigan (2.0%). In all areas, testing of at-risk heterosexuals increased in the year after HIV reporting was implemented (Louisiana, 10.5%; Michigan, 225.1 %; Nebraska, 5.7%; Nevada, 303.3%; New Jersey, 462.9%; Tennessee, 603.8%). Declines in testing occurred among men who have sex with men in Louisiana (4.3%) and Tennessee (4.1%) after HIV reporting; testing increased for this group in Michigan (5.3%), Nebraska (19.6%), Nevada (12.5%), and New Jersey (22.4%). Among injection drug users, testing declined in Louisiana (15%), Michigan (34.3%), and New Jersey (0.6%) and increased in Nebraska (1.7%), Nevada (18.9%), and Tennessee (16.6%). CONCLUSIONS: Confidential HIV reporting by name did not appear to affect use of HIV testing in publicly funded counseling and testing programs. 相似文献
88.
A novel property of hippocampal LTP, 'variable persistence', has recently been described that is, we argue, relevant to the role of LTP in information storage. Specifically, new results indicate that a particular pattern of synaptic activation can give rise, either to a relatively short-lasting LTP, or to a longer-lasting LTP as a function of the history of activation of the neuron. This has led to the idea that the induction of LTP is associated with the setting of a'synaptic tag' at activated synapses, whose role is to sequester plasticity-related proteins that then serve to stabilize temporary synaptic changes and so extend their persistence. In this article, we outline the synaptic tag hypothesis, compare predictions it makes with those of other theories about the persistence of LTP, and speculate about the cellular identity of the tag. In addition, we outline the requirement for aminergic activation to induce late LTP and consider the functional implications of the synaptic tag hypothesis with respect to long-term memory. 相似文献
89.
Shockley Kevin; Baker Aimee A.; Richardson Michael J.; Fowler Carol A. 《Canadian Metallurgical Quarterly》2007,33(1):201
Cooperative conversation has been shown to foster interpersonal postural coordination. The authors investigated whether such coordination is mediated by the influence of articulation on postural sway. In Experiment 1, talkers produced words in synchrony or in alternation, as the authors varied speaking rate and word similarity. Greater shared postural activity was found for the faster speaking rate. In Experiment 2, the authors demonstrated that shared postural activity also increases when individuals speak the same words or speak words that have similar stress patterns. However, this increase in shared postural activity is present only when participants' data are compared with those of their partner, who was present during the task, but not when compared with the data of a member of a different pair speaking the same word sequences as those of the original partner. The authors' findings suggest that interpersonal postural coordination observed during conversation is mediated by convergent speaking patterns. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
90.
The sequences of the 16S rRNA genes (rrs genes) of Clostridium chauvoei, the causative agent of blackleg in cattle, and the phenotypically related organism Clostridium septicum were determined. After amplification of 1,507-bp PCR fragments from the corresponding rrs genes, the sequences were determined in a single round of sequencing by using conserved region primers. A sequence similarity analysis of the sequences revealed the close phylogenetic relationship of C. chauvoei and C. septicum in Clostridium cluster I (M. D. Collins, P. A. Lawson, A. Willems, J. J. Cordoba, J. Fernandez-Garayzabal, P. Garcia, J. Cai, H. Hippe, and J. A. E. Farrow, Int. J. Syst. Bacteriol. 44:812-826, 1994), which includes Clostridium carnis, Clostridium perfringens, Clostridium botulinum, and Clostridium tetani. We found that 99.3% of the nucleotides in the genes of C. chauvoei and C. septicum are identical. 相似文献