全文获取类型
收费全文 | 3338篇 |
免费 | 39篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 34篇 |
综合类 | 2篇 |
化学工业 | 471篇 |
金属工艺 | 36篇 |
机械仪表 | 58篇 |
建筑科学 | 174篇 |
矿业工程 | 15篇 |
能源动力 | 68篇 |
轻工业 | 234篇 |
水利工程 | 12篇 |
石油天然气 | 19篇 |
无线电 | 235篇 |
一般工业技术 | 399篇 |
冶金工业 | 1213篇 |
原子能技术 | 28篇 |
自动化技术 | 383篇 |
出版年
2021年 | 18篇 |
2019年 | 22篇 |
2017年 | 21篇 |
2016年 | 28篇 |
2015年 | 22篇 |
2014年 | 38篇 |
2013年 | 145篇 |
2012年 | 73篇 |
2011年 | 117篇 |
2010年 | 94篇 |
2009年 | 82篇 |
2008年 | 115篇 |
2007年 | 104篇 |
2006年 | 113篇 |
2005年 | 77篇 |
2004年 | 78篇 |
2003年 | 84篇 |
2002年 | 82篇 |
2001年 | 63篇 |
2000年 | 60篇 |
1999年 | 69篇 |
1998年 | 157篇 |
1997年 | 109篇 |
1996年 | 100篇 |
1995年 | 95篇 |
1994年 | 85篇 |
1993年 | 77篇 |
1992年 | 64篇 |
1991年 | 37篇 |
1990年 | 53篇 |
1989年 | 57篇 |
1988年 | 64篇 |
1987年 | 58篇 |
1986年 | 56篇 |
1985年 | 59篇 |
1984年 | 50篇 |
1983年 | 56篇 |
1982年 | 55篇 |
1981年 | 38篇 |
1980年 | 51篇 |
1979年 | 46篇 |
1978年 | 34篇 |
1977年 | 43篇 |
1976年 | 52篇 |
1975年 | 42篇 |
1974年 | 45篇 |
1973年 | 34篇 |
1972年 | 26篇 |
1971年 | 17篇 |
1970年 | 17篇 |
排序方式: 共有3381条查询结果,搜索用时 10 毫秒
11.
S Pollack MG Woerner A Howard RB Fireworker JM Kane 《Canadian Metallurgical Quarterly》1998,34(1):89-92
Diabetes mellitus positive for antibodies to glutamate decarboxylase is heterogeneous as far as the degree of impairment of endogenous insulin release, though antibodies to glutamate decarboxylase are the most useful marker for future insulin deficiency. To investigate what determines the prognosis of diabetes mellitus positive for antibodies to glutamate decarboxylase, we measured HLA-DRB1 alleles in three groups: 77 cases of insulin-dependent diabetes mellitus (IDDM), 44 of non-insulin-dependent diabetes mellitus (NIDDM) with secondary failure of oral hypoglycemic therapy, and 22 of NIDDM well controlled by diet and/or sulfonylurea agents. The proportion of susceptible and resistant alleles to IDDM determined the degree of insulin deficiency, and comparison of IDDM to NIDDM well controlled by diet and/or sulfonylurea agents revealed significant differences in DRB1*0405 (P < 0.05; RR = 2.82 and RR = 0.89, respectively) and DRB1*1502 (P < 0.001; RR = 0.02 and RR = 2.19, respectively). This study revealed that HLA-DRB1 alleles contribute to determining the prognosis of Japanese diabetes mellitus positive for antibodies to glutamate decarboxylase. 相似文献
12.
Howard Kenneth I.; Krause Merton S.; Orlinsky David E. 《Canadian Metallurgical Quarterly》1986,54(1):106
Presents an analysis of the attrition dilemma in psychotherapy research and reviews the methods used to compensate for data loss. It is argued that attrition is not ultimately a problem of bias but a problem of lack of information. A reformulation is offered that integrates single-case studies with traditional group comparison methodology in an attempt to find optimal causal relations of treatments to outcomes. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
Interviewed 120 sunbathing and nonsunbathing beachgoers about their health practices, knowledge about skin cancer, moods, and social rewards obtained through sunbathing. Ss also completed personality questionnaires. Data were considered using a theoretical perspective combining aspects of health belief, social influence, social learning, and risk-taking models. Results indicate that sunbathing was related to having a positive attitude toward risk taking, having little knowledge about skin cancer, reporting a relaxed mood, having friends who sunbathe, and engaging in activities related to maintaining a positive physical appearance. Sunscreen use was related to sex, having knowledge about skin cancer, knowing people who have had cancer, and reporting high levels of anxiety. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
15.
16.
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
17.
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
18.
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
19.
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
20.
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