全文获取类型
收费全文 | 6174篇 |
免费 | 175篇 |
国内免费 | 10篇 |
学科分类
工业技术 | 6359篇 |
出版年
2021年 | 65篇 |
2020年 | 63篇 |
2019年 | 63篇 |
2018年 | 76篇 |
2017年 | 65篇 |
2016年 | 83篇 |
2015年 | 86篇 |
2014年 | 90篇 |
2013年 | 369篇 |
2012年 | 220篇 |
2011年 | 262篇 |
2010年 | 185篇 |
2009年 | 195篇 |
2008年 | 242篇 |
2007年 | 242篇 |
2006年 | 209篇 |
2005年 | 205篇 |
2004年 | 181篇 |
2003年 | 165篇 |
2002年 | 179篇 |
2001年 | 108篇 |
2000年 | 108篇 |
1999年 | 123篇 |
1998年 | 115篇 |
1997年 | 119篇 |
1996年 | 128篇 |
1995年 | 92篇 |
1994年 | 85篇 |
1993年 | 102篇 |
1992年 | 92篇 |
1991年 | 68篇 |
1990年 | 82篇 |
1989年 | 97篇 |
1988年 | 89篇 |
1987年 | 91篇 |
1986年 | 84篇 |
1985年 | 103篇 |
1984年 | 115篇 |
1983年 | 90篇 |
1982年 | 77篇 |
1981年 | 88篇 |
1980年 | 65篇 |
1979年 | 98篇 |
1978年 | 74篇 |
1977年 | 78篇 |
1976年 | 62篇 |
1975年 | 68篇 |
1974年 | 57篇 |
1973年 | 75篇 |
1972年 | 53篇 |
排序方式: 共有6359条查询结果,搜索用时 46 毫秒
51.
52.
Blanchard Edward B.; Appelbaum Kenneth A.; Guarnieri Patricia; Neff Debra F.; Andrasik Frank; Jaccard James; Barron Kevin D. 《Canadian Metallurgical Quarterly》1988,56(3):427
Tension and vascular headache patients, initially treated with biofeedback and/or relaxation training in either a minimal therapist contact protocol (3 visits) or an intensive individual protocol (10 or 16 visits) were followed-up prospectively for 2 years. In the first study, for the first 6 months of follow-up, half of all patients continued to keep headache diaries and were seen monthly and the other half had only minimal contact. The results at 1-year follow-up, based on 4 weeks of daily headache diaries, revealed equally good maintenance from both treatment protocols and from both follow-up conditions. In Study 2, we found that patients remained improved over pretreatment baseline levels at the 2-year follow-up regardless of initial treatment intensity. Approximately three quarters of vascular patients who were initially improved at posttreatment remained improved at 2 years. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
53.
Regression analyses of counts and rates: Poisson, overdispersed Poisson, and negative binomial models. 总被引:1,自引:0,他引:1
The regression models appropriate for counted data have seen little use in psychology. This article describes problems that occur when ordinary linear regression is used to analyze count data and presents 3 alternative regression models. The simplest, the Poisson regression model, is likely to be misleading unless restrictive assumptions are met because individual counts are usually more variable ("overdispersed") than is implied by the model. This model can be modified in 2 ways to accommodate this problem. In the overdispersed model, a factor can be estimated that corrects the regression model's inferential statistics. In the second alternative, the negative binomial regression model, a random term reflecting unexplained between-subject differences is included in the regression model. The authors compare the advantages of these approaches. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
Discusses the mental health problems that may occur as elderly people must face adjustments because of bereavement, poor physical health, the demands of caring for an ill spouse, drug/alcohol abuse, dementia and cognitive impairments, and multiple health problems. Negative social stereotypes associated with both elderly patients and mental health care, limited access to and a lack of trained professionals in the area of geriatric mental health care, lack of outreach, inadequate benefits under prepaid health plans, Medicare and Medicaid, and special problems of ethnic minority and rural elderly people all contribute to an inadequate mental health care system. The author, a US representative, suggests a redesigning of the system and outlines an initiative that addresses the development of an effective mental health care system for the elderly, modification of Medicare and Medicaid, and improvements in quality assurance and access protection. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
94 smokers (mean age 39 yrs) in a 6-wk behavioral smoking-cessation program were administered weekly questionnaires on their use of major program recommendations and other quitting strategies throughout treatment. An "affect-regulation" coping inventory was administered at the beginning and end of treatment. Adequate adherence was reported for most recommendations. Although a composite measure of adherence did not predict quitting success, adherence and coping assessments were associated with maintenance of treatment gains. Short-term maintenance was associated with an extensive affect-regulation repertoire and use of stimulus control strategies; long-term maintenance was associated with consistent self-monitoring of smoking during treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
Over the years the number of Web users has increased dramatically unfortunately leading to the inherent problem of congestion. This can affect each user's surfing experience. This paper investigates download times associated with a web request, identifies where delays occur, and provides guidelines which can be followed by web developers to enable a faster and more efficient download and service for their users. We conclude that delays in Internet traffic and congestion can often be attributed to poorly developed sites (e.g. excessive image size). Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
57.
58.
Edward G. Goetz 《Journal of Urban Affairs》1991,13(3):337-351
ABSTRACT: Many analysts argue that important structural conditions exist that discourage city governments from engaging in redistributive policy, especially programs that create direct costs for private developers. Labeled the limited city argument, this logic concludes that only cities with sufficient levels of economic and fiscal well-being can afford to impose upon private developers to meet social needs. Using survey data from 133 cities with populations over 100,000, this paper examines land use regulations that impose obligations or restrictions on the private sector to promote low income housing. The data suggest that the limited city argument is only part of the explanation. The use of regulatory housing policy is also correlated with measures of need and low income housing advocacy. 相似文献
59.
A reverse analysis of a 6 degree of freedom (dof) subchain of a modified 7 dof flight telerobotic servicer (FTS) manipulator system is presented. The 6 dof subchain is designated as a TR-RT* chain. At the outset, it was considered that the reverse analysis would be similar to a TTT manipulator analyzed previously for which the third and fourth joints intersect at a finite point. This was not, however, the case and a sixteenth-degree tan-half-angle polynomial was derived for the TR-RT manipulator. The elimination procedure is interesting and much simpler than the procedures for the general case. 相似文献
60.
Liaqat A. Khan Edward A. Wicklein E. C. Teixeira 《Canadian Metallurgical Quarterly》2006,132(7):741-746
A three-dimensional (3D) computational fluid dynamics (CFD) model of a contact tank is presented in this paper. The model results are compared against 3D velocities and flow through curve (FTC) data, representing a tracer concentration profile, from a 1:8 scale physical model. The objective is to demonstrate that CFD models can simulate both the FTC and the 3D velocity field quite well. Simultaneous validation of velocities and FTC is important in ascertaining the predictive capabilities of CFD models, as physical model studies indicate that different baffle arrangements can lead to similar FTCs. Therefore, a good prediction of only FTC, as presented in previous 3D CFD model studies, does not necessarily imply a correct simulation of the flow field. 相似文献