全文获取类型
收费全文 | 2004篇 |
免费 | 45篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 249篇 |
金属工艺 | 22篇 |
机械仪表 | 44篇 |
建筑科学 | 95篇 |
矿业工程 | 6篇 |
能源动力 | 59篇 |
轻工业 | 206篇 |
水利工程 | 16篇 |
石油天然气 | 4篇 |
无线电 | 214篇 |
一般工业技术 | 272篇 |
冶金工业 | 650篇 |
原子能技术 | 26篇 |
自动化技术 | 178篇 |
出版年
2023年 | 16篇 |
2022年 | 13篇 |
2021年 | 31篇 |
2020年 | 30篇 |
2019年 | 32篇 |
2018年 | 27篇 |
2017年 | 26篇 |
2016年 | 33篇 |
2015年 | 16篇 |
2014年 | 39篇 |
2013年 | 78篇 |
2012年 | 58篇 |
2011年 | 83篇 |
2010年 | 56篇 |
2009年 | 42篇 |
2008年 | 60篇 |
2007年 | 74篇 |
2006年 | 68篇 |
2005年 | 55篇 |
2004年 | 43篇 |
2003年 | 51篇 |
2002年 | 49篇 |
2001年 | 47篇 |
2000年 | 36篇 |
1999年 | 48篇 |
1998年 | 155篇 |
1997年 | 119篇 |
1996年 | 72篇 |
1995年 | 42篇 |
1994年 | 43篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 20篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 26篇 |
1979年 | 15篇 |
1978年 | 13篇 |
1977年 | 33篇 |
1976年 | 42篇 |
1975年 | 14篇 |
1974年 | 18篇 |
排序方式: 共有2055条查询结果,搜索用时 609 毫秒
11.
Ahluwalia Jasjit S.; Nollen Nicole; Kaur Harsohena; James Aimee S.; Mayo Matthew S.; Resnicow Ken 《Canadian Metallurgical Quarterly》2007,26(2):214
Objectives: Examine the effectiveness of an intervention to increase fruits and vegetables (FV) consumption among smokers. Design: Cluster-randomized trial of 20 public housing developments; 10 randomly assigned to an FV intervention and 10 to a smoking cessation intervention. Main outcome measures: Usual (past 7 days) and past 30 days change in daily FV intake at 8 weeks and 6 months postbaseline. Results: Greater increases were seen in the FV group. At Week 8 and Month 6, the FV group had consumed 1.58 (p = .001) and 0.78 (p = .04), respectively, more daily FV servings in the past 7 days than the cessation group. At the same time points, the FV group had consumed 3.61 (p = .01) and 3.93 (p = .01), respectively, more FV servings in the past 30 days than the cessation group. Completing more motivational interviewing sessions (p = .02) and trying more recipes (p = .02) led to significantly greater increases at Month 6 among FV participants. Conclusions: Motivational interviewing counseling and lifestyle modification through trying out healthy recipes may be effective in helping a high-risk population increase their FV intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
12.
The utility of guided ultrasonic waves for increasing the efficiency and sensitivity of nuclear steam generator tubing evaluation by nondestructive means is explored. The basic theoretical background of guided waves in tubes is presented, with major emphasis placed on those results with direct relevance to NDE applications. The possibility of increasing the inspection range of the guided wave modes as well as their sensitivity to defects by proper choice of mode and frequency is also discussed. 相似文献
13.
Vector quantization by deterministic annealing 总被引:7,自引:0,他引:7
Rose K. Gurewitz E. Fox G.C. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(4):1249-1257
A deterministic annealing approach is suggested to search for the optimal vector quantizer given a set of training data. The problem is reformulated within a probabilistic framework. No prior knowledge is assumed on the source density, and the principle of maximum entropy is used to obtain the association probabilities at a given average distortion. The corresponding Lagrange multiplier is inversely related to the `temperature' and is used to control the annealing process. In this process, as the temperature is lowered, the system undergoes a sequence of phase transitions when existing clusters split naturally, without use of heuristics. The resulting codebook is independent of the codebook used to initialize the iterations 相似文献
14.
15.
16.
Ockene Judith K.; Kristeller Jean; Pbert Lori; Hebert James R.; Luippold Rose; Goldberg Robert J.; Landon Joan; Kalan Kathryn 《Canadian Metallurgical Quarterly》1994,13(3):278
Patterns of smoking cessation using 6- and 12-mo follow-up data are reported for 1,261 primary care patients randomized to 3 physician-delivered smoking interventions: advice only (AO), counseling (CI), and counseling plus availability of nicotine-containing gum (CI?+?NCG). One-week point-prevalence cessation rates at 12 mo did not differ among the interventions: AO (15.2%), CI (12.9%) and CI?+?NCG (16.7%). However, maintained cessation rates (abstinent at both 6 and 12 mo) increased with intervention intensity: AO (6.0%), CI (7.8%), and CI?+?NCG (10.0%): Test of trend χ–2?=?5.06, p?=?.02. CI?+?NCG was significantly higher than AO (p?=?.02). The findings support the following conclusions: Brief physician delivered intervention with availability of nicotine-containing gum can have a beneficial long-term effect on smoking cessation, and cohort data as well as point-prevalence rates are important when assessing the long-term impact of lifestyle interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
17.
18.
WJ Aspden A Rao K Rose PT Scott IJ Clarke TE Trigg J Walsh MJ D''Occhio 《Canadian Metallurgical Quarterly》1997,14(6):429-437
Tooth loss diminishes oral function and quality of life, and national health targets aim to reduce population levels of tooth loss. OBJECTIVES: The purpose of this study was to determine tooth loss incidence and predictors of tooth loss among older adults in South Australia. METHODS: Data were obtained from a cohort study of a stratified random sample of community-dwelling dentate people aged 60+ years. Interviews and oral examinations were conducted among 911 individuals at baseline and among 693 of them (76.1%) 2 years later. Incidence rates and relative risks were calculated for population subgroups and multivariate logistic regression was used to construct risk prediction models. A method was developed to calculate 95% confidence intervals (95% CI) for relative risks (RR) from logistic regression models using a Taylor series approximation. RESULTS: Some 19.5% (95% CI = 15.4-23.6%) of people lost one or more teeth during the 2 years. Men, people with a recent extraction, people who brushed their teeth infrequently, smokers and people born outside Australia had significantly (P < 0.05) greater risk of tooth loss. Baseline clinical predictors of tooth loss included more missing teeth, retained roots, decayed root surfaces, periodontal pockets and periodontal recession. In a multivariate model that controlled for baseline clinical predictors, former smokers (RR = 2.55, 95% CI = 1.48-4.40) and current smokers (RR = 2.06, 95% CI = 0.92-4.62) had similarly elevated risks of tooth loss compared with non-smokers. CONCLUSIONS: The findings from this population suggest that a history of smoking contributes to tooth loss through mechanisms in addition to clinical disease processes alone. 相似文献
19.
JM Chen ML Barr A Chadburn G Frizzera FA Schenkel RR Sciacca DS Reison LJ Addonizio EA Rose DM Knowles 《Canadian Metallurgical Quarterly》1993,56(3):527-538
We conducted a retrospective study of 516 cardiac recipients who underwent transplantation between April 1983 and April 1992, 19 of whom had development of post-transplantation lymphoproliferative disorders (PTLDs). These 19 patients presented with involvement of lung (5), gastrointestinal tract (5), disseminated disease (6), and adenoids and lymph nodes (3). B-cell proliferations ranging from an atypical hyperplasia to malignant lymphoma developed in 18 patients, and mixed cellularity Hodgkin's disease developed in 1 patient. The 19 patients with PTLD displayed a predominance of both women and cardiomyopathy as the indication for transplantation when compared with two separate control populations. No correlation was found between demographic criteria analyzed and (1) early versus late diagnosis of PTLD after transplantation, (2) the site of PTLD involvement, or (3) the histopathologic category of the PTLD lesion. Patients with gastrointestinal tract and lung PTLD involvement enjoyed an improved survival after both transplantation and PTLD diagnosis when compared with patients with PTLD involvement of all other extranodal sites. We report a high incidence of PTLD involving the lung and gastrointestinal tract in our cohort study. These sites of involvement responded better to a reduction in immunosuppression than did the other extranodal sites of involvement. 相似文献
20.