全文获取类型
收费全文 | 3582篇 |
免费 | 43篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 36篇 |
综合类 | 2篇 |
化学工业 | 491篇 |
金属工艺 | 43篇 |
机械仪表 | 63篇 |
建筑科学 | 179篇 |
矿业工程 | 15篇 |
能源动力 | 70篇 |
轻工业 | 244篇 |
水利工程 | 14篇 |
石油天然气 | 19篇 |
无线电 | 262篇 |
一般工业技术 | 409篇 |
冶金工业 | 1354篇 |
原子能技术 | 29篇 |
自动化技术 | 399篇 |
出版年
2020年 | 18篇 |
2019年 | 23篇 |
2017年 | 21篇 |
2016年 | 29篇 |
2015年 | 22篇 |
2014年 | 37篇 |
2013年 | 146篇 |
2012年 | 73篇 |
2011年 | 119篇 |
2010年 | 94篇 |
2009年 | 86篇 |
2008年 | 121篇 |
2007年 | 111篇 |
2006年 | 117篇 |
2005年 | 79篇 |
2004年 | 81篇 |
2003年 | 87篇 |
2002年 | 84篇 |
2001年 | 63篇 |
2000年 | 63篇 |
1999年 | 77篇 |
1998年 | 198篇 |
1997年 | 121篇 |
1996年 | 117篇 |
1995年 | 98篇 |
1994年 | 96篇 |
1993年 | 85篇 |
1992年 | 68篇 |
1991年 | 40篇 |
1990年 | 56篇 |
1989年 | 65篇 |
1988年 | 70篇 |
1987年 | 67篇 |
1986年 | 65篇 |
1985年 | 67篇 |
1984年 | 56篇 |
1983年 | 58篇 |
1982年 | 57篇 |
1981年 | 44篇 |
1980年 | 53篇 |
1979年 | 50篇 |
1978年 | 43篇 |
1977年 | 48篇 |
1976年 | 63篇 |
1975年 | 43篇 |
1974年 | 45篇 |
1973年 | 34篇 |
1972年 | 27篇 |
1971年 | 18篇 |
1970年 | 18篇 |
排序方式: 共有3629条查询结果,搜索用时 310 毫秒
21.
Sherman Seth J.; Atri Alireza; Hasselmo Michael E.; Stern Chantal E.; Howard Marc W. 《Canadian Metallurgical Quarterly》2003,117(3):526
Eight subjects studied a set of complex visual images after administration of 0.4 mg scopolamine. Another 8 subjects performed the same task without drug administration. On a subsequent item recognition test, subjects rated, on a 5-point scale, their confidence that the studied pictures and an equal number of unstudied lures were actually presented. Results showed that scopolamine affected responses to studied items, but not unstudied lures, demonstrating an unambiguous effect of scopolamine on recognition memory. To describe the scopolamine-injected subjects' data, the authors constructed a new model of 2-process recognition that includes the A. P. Yonelinas (1994) model as a limiting case. The model analysis suggests that scopolamine affected both familiarity and recollection. In particular, scopolamine did not affect the frequency with which recollection took place, but rather, affected the amount of recollected information. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
22.
23.
24.
Agrees with R. W. Motta et al's (see record 1994-04005-001) conclusion that there is little evidence that human figure drawings (HFDs) have any predictive validity or definitive clinical use in personality and intellectual assessment. Use of the HFD as a personality assessment tool is reviewed in the empirical literature. It is concluded that the only defensible ways that HFDs can be used involve hypothesis generating and testing under behavioral or cognitive-behavioral perspectives. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
Tucker Joan S.; Friedman Howard S.; Tsai Catherine M.; Martin Leslie R. 《Canadian Metallurgical Quarterly》1995,10(1):3
Models of the relations between contact with pets and better health are examined in an archival prospective study using data derived from the longitudinal study initiated by Terman in 1921 (current N?=?343 men, 300 women) . In survival analyses of documented longevity, playing with pets in 1977 (M age?=?67 years) was not associated with mortality risk through 1991 for the total sample nor for those who were unmarried or those who were less satisfied with their human relationships. Playing with pets was not associated with health-prone attributes or healthy behaviors such as personality, social ties, education, and smoking. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
26.
With worldwide energy consumption rising, there is a need to reduce energy use of the housing stock. While this general idea is well-known, there is an overwhelming amount of product data and manufacturers claims through which the homebuilder or designer must sort to make informed selections of energy-efficient upgrades. The main objective of this research was to identify cost effective–energy efficient upgrades from a group of 16 commonly available choices, and rank them according to the most beneficial for the least cost. This study was conducted in Phoenix, Arizona, and included a sample of 30 production-style homes typical of the Phoenix metropolitan area. Energy-simulation software was used to perform energy evaluations and derive the benefits of each upgrade. The cost of each upgrade was obtained from a database of national average costs and from a local context. Differences in the selection of beneficial upgrades vary dramatically with the source of the cost information. This research provides a generic methodology that can be used by builders and designers to select appropriate energy-efficient upgrades for a given geographic area that will provide high operating benefits relative to the amount of capital investment. 相似文献
27.
Assessed the retention of memory units for word-like strings of letters using the perceptions of 120 undergraduates in 2 experiments in determining how frequently various letters appeared. A series of strings was presented at 1 of 3 exposure durations. Within the series, the frequencies of occurrence of different strings and of the letters composing the strings were varied orthogonally. Results indicate that, at relatively long exposure durations, Ss could discriminate the frequency of occurrence for both strings and their constituent letters. The formation of global-level (string) memory units was indicated by judgments of string frequency being unaffected by either the frequencies of their component letters or experimental conditions (brief exposures) that prohibited accurate judgment of letter frequency. Although judgments of letter frequency were sometimes biased by the frequency of the strings containing the letters, the success with which the judgments discriminated different levels of letter frequency did not depend on the activation of string-level memory units. Furthermore, Ss' frequency judgments for letters were not predictable from their recall of the strings containing the letters. Results provide evidence for the formation of element-level (letter) memory units. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
Howard Kenneth I.; Krause Merton S.; Vessey John T. 《Canadian Metallurgical Quarterly》1994,31(2):302
The immediate goal of any clinical trial is to determine to which of a specified set of treatments future patients are to be assigned, particularly when analyzing data from clinical trials. When the outcome distributions of Experimental (E) and Control (C) treatments overlap, differences between treatment group means are not conclusive and may not be very informative, so a display of the overlapped frequency distributions and a summary measure of the probability of a random patient in E doing better than a random patient in C are needed. When outcome distributions overlap, the question of statistical model becomes crucial even when there are very significant differences between group means and very large effect sizes. Determining what patient variables interact with treatments is the route to optimal assignment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
Bo Jiang Jeffrey L. Brown Jane Sheraton Nathalie Fortin Howard Bussey 《Yeast (Chichester, England)》1994,10(3):341-353
We have identified three yeast genes, KES1, HES1 and OSH1, whose products show homology to the human oxysterol binding protein (OSBP). Mutations in these genes resulted in pleiotropic sterol-related phenotypes. These include tryptophan-transport defects and nystatin resistance, shown by double and triple mutants. In addition, mutant combinations showed small but apparently cumulative reductions in membrane ergosterol levels. The three yeast genes are also functionally related as overexpression of HES1 or KES1 alleviated the tryptophan-transport defect in kes1Δ or osh1Δ mutants, respectively. Our study implicates this new yeast gene family in ergosterol synthesis and provides comparative evidence of a role for human OSBP in cholesterol synthesis. 相似文献
30.
Levin Harvey S.; Mendelsohn Dianne; Lilly Matthew A.; Fletcher Jack M.; Culhane Kathleen A.; Chapman Sandra B.; Harward Harriet; Kusnerik Lori; Bruce Derek; Eisenberg Howard M. 《Canadian Metallurgical Quarterly》1994,8(2):171
To investigate the relationship of severity of pediatric closed head injury (CHI), the contribution of frontal lobe lesions, and age at testing (6–10 yr olds vs 11–15 yr olds) to cognitive deficit, 134 head-injured patients were given the Tower of London (TOL) task and underwent magnetic resonance imaging. 89 normal controls were given the TOL for comparison. Severity of CHI and age at testing were strongly related to cognitive performance on the TOL, including the frequency of breaking the rules. Volume of frontal lobe lesion (but not extrafrontal lesion) contributed to the prediction of perfomance on the TOL even after severity of injury was taken into account. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献