全文获取类型
收费全文 | 4054篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 63篇 |
金属工艺 | 1篇 |
机械仪表 | 3篇 |
建筑科学 | 3篇 |
能源动力 | 3篇 |
轻工业 | 26篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 10篇 |
一般工业技术 | 13篇 |
冶金工业 | 3910篇 |
原子能技术 | 1篇 |
自动化技术 | 24篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 6篇 |
2009年 | 5篇 |
2008年 | 1篇 |
2007年 | 9篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 11篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 111篇 |
1998年 | 1179篇 |
1997年 | 709篇 |
1996年 | 454篇 |
1995年 | 223篇 |
1994年 | 226篇 |
1993年 | 219篇 |
1992年 | 18篇 |
1991年 | 44篇 |
1990年 | 37篇 |
1989年 | 44篇 |
1988年 | 35篇 |
1987年 | 41篇 |
1986年 | 53篇 |
1985年 | 37篇 |
1984年 | 4篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 27篇 |
1980年 | 54篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 114篇 |
1976年 | 262篇 |
1975年 | 10篇 |
1964年 | 1篇 |
1955年 | 5篇 |
1954年 | 2篇 |
排序方式: 共有4063条查询结果,搜索用时 31 毫秒
51.
52.
53.
Commercially targeted virtual reality (VR) equipment is gaining popularity and might be a viable tool for pain distraction. This experimental research aimed to discover whether active distraction techniques (such as commercially targeted VR and video games) result in reduced subjective discomfort relative to passive distraction techniques. The study examined a healthy adult population who experienced an experimentally induced discomfort task. Participants were 27 adults, 14 females and 13 males. Participants completed four tasks, a baseline measure of physical discomfort, video clip distraction (passive distraction), video game distraction (active distraction) and exploring a VR world using an Oculus Rift head-mounted display (active distraction). In all four test conditions, participants were asked to sit on a chair holding their non-dominant leg at a height of approximately 30 cm from the floor, up to a maximum of 5 min. Counterbalancing of task order was conducted to reduce effects of participant fatigue. The participants indicated significantly reduced self-reported discomfort in the active distraction tasks when compared to the passive distraction tasks. While the findings demonstrate the effectiveness of a commercially targeted VR technology in increasing pain tolerance, the relative benefits of this technology over non-immersive video games are not apparent. 相似文献
54.
R Fuhrer C Dufouil TC Antonucci MJ Shipley C Helmer JF Dartigues 《Canadian Metallurgical Quarterly》1999,149(2):116-126
The possible modifying effect of social relations on the association between depression and mortality was examined in a community-based cohort study. A total of 3,777 randomly selected persons 65 years of age and older in southwest France were followed over a 5-year period from 1988 in the Personnes Agees Quid (PAQUID). At study entry, the prevalence of elevated depressive symptomatology was 12.9% for men and 14.7% for women, and the reported relative isolation was 14.1% for men and 26.0% for women. During a total of 16,984 person-years of follow-up, 849 deaths occurred. Among participants with high levels of depressive symptomatology, the age-adjusted mortality rate ratio was 2.10 (95% confidence interval 1.7-2.7) in men and 1.76 (95% confidence interval 1.4-2.3) in women. When compared with individuals with the most connections, men and women with few social network connections were also at increased risk of mortality: age-adjusted rate ratio = 2.69 (95% confidence interval 1.9-3.8) for men and 1.56 (95% confidence interval 1.0-2.4) for women. Satisfaction with social support had a small but nonsignificant effect on mortality risk. For women, the excess risks due to depressive symptoms and few network connections are observed only in the 65- to 74-year age group, after adjusting for health and health behaviors. Social relations did not significantly modify the depression-mortality associations for either men or women, although the depression-mortality effect was reduced by 12.8% in men. The latter findings do not appear to be compatible with the buffering hypothesis, whereby we would expect social relations to decrease the depression-mortality association. Nonetheless, there are independent effects from these two factors, and older men who are depressed and not socially connected are at increased risk of dying earlier. 相似文献
55.
56.
H Morales P Tilquin JF Rees A Massip F Dessy A Van Langendonckt 《Canadian Metallurgical Quarterly》1999,52(2):149-157
The impact of oxidative stress on the in vitro development of bovine embryos in synthetic oviduct fluid medium (mSOF) was assessed by using H2O2 as a stress inducer. In a preliminary experiment, a chemiluminescent method was used to measure the antioxidative capacity of the mSOF culture medium. Pyruvate was the mSOF component displaying the highest H2O2 degrading ability. Essential and nonessential amino acids also significantly reduced the H2O2 concentration, whereas lactate and glutamine were ineffective. The effect on further development of a short exposure of zygotes, 9-16-cell stage embryos and blastocysts to 0 M; 10(-7) M ; 10(-6) M, and 10(-5) M H2O2 in pyruvate-free mSOF was evaluated. Developmental rates of the H2O2-treated zygotes to the 5-8-cell or blastocyst stages and survival of H2O2-treated blastocysts were reduced in a dose-dependent manner whereas the 9-16-cell embryos were unaffected by those treatments. Blastocysts treated with H2O2 also tended to have lower numbers of bisbenzimide-stained nuclei and showed increased nuclear fragmentation. Including pyruvate in the mSOF culture medium during a 10(-5) M H2O2 pulse highly reduced the H2O2 concentration as measured by chemiluminescence and improved zygote and blastocyst development, but failed to prevent blastocyst nuclei degradation. These experiments suggest that bovine embryos show developmental change in sensitivity to exogenous H2O2, the 9-16-cell embryos being more resistant than zygotes and blastocysts and that H2O2 and its toxic effects can be attenuated by including pyruvate in the medium. 相似文献
57.
S Sharir MA Jewett JF Sturgeon M Moore PR Warde CN Catton MK Gospodarowicz 《Canadian Metallurgical Quarterly》1999,161(2):472-5; discussion 475-6
PURPOSE: To optimize followup in patients with stage I nonseminomatous testis cancer on surveillance we evaluated the contribution of each followup modality to the detection of progression as well as morbidity and mortality outcomes. MATERIALS AND METHODS: After orchiectomy 170 patients with clinical stage I nonseminoma were prospectively placed on a surveillance protocol. History, physical examination, serum tumor markers, abdominal and pelvic computerized tomography (CT), and chest x-ray were used for followup. The number of failures, methods and timing of progression detection, treatments required, mortality rate and subsequent contralateral primary tumors were recorded. RESULTS: The 170 surveillance patients were followed a median of 6.3 years. Within 2 years (median 6.9 months) postoperatively 48 patients (28.2%) had disease progression. History, physical examination, markers, CT and chest radiography provided the initial evidence of progression in 18 (37.5%), 34 (70.8%), 34 (70.8%), and 4 (8.3%) patients, respectively. Each modality was the only indicator of failure in 2 (4.2%), 4 (8.3%), 10 (20.8%) and 0 cases, respectively. Of the 170 patients 122 (71.8%) required no additional treatment beyond orchiectomy, 26 (15.3%) received 1 and 22 (12.9%) underwent more than 1 therapeutic modality. Only 1 patient (0.6%) died of disease. Contralateral tumors developed in 5 cases (2.9%) therapeutic a mean of 8.1 years after orchiectomy. CONCLUSIONS: In stage I nonseminoma patients, surveillance history, physical examination, tumor markers and abdominopelvic CT are necessary components of the followup protocol. Removal of routine chest x-ray from the protocol would not have changed progression detection. The initial surveillance visit must occur by 2 months postoperatively. Patients should be followed beyond 5 years and likely for life in addition to regular patient self-examination. 相似文献
58.
C Ledent O Valverde G Cossu F Petitet JF Aubert F Beslot GA B?hme A Imperato T Pedrazzini BP Roques G Vassart W Fratta M Parmentier 《Canadian Metallurgical Quarterly》1999,283(5400):401-404
The function of the central cannabinoid receptor (CB1) was investigated by invalidating its gene. Mutant mice did not respond to cannabinoid drugs, demonstrating the exclusive role of the CB1 receptor in mediating analgesia, reinforcement, hypothermia, hypolocomotion, and hypotension. The acute effects of opiates were unaffected, but the reinforcing properties of morphine and the severity of the withdrawal syndrome were strongly reduced. These observations suggest that the CB1 receptor is involved in the motivational properties of opiates and in the development of physical dependence and extend the concept of an interconnected role of CB1 and opiate receptors in the brain areas mediating addictive behavior. 相似文献
59.
JF Rehfeld 《Canadian Metallurgical Quarterly》1997,159(51):7673-7677
The aim of this study was to measure size and quality of the research carried out in Copenhagen (H:S) hospitals using conventional bibliometry. Based on the H:S-report on scientific publications in 1995, the research performed in each hospital and each department has been measured as the sum of publications and as journal impact factor score. Publication numbers and impact factor score varied eighty-fold between the individual H:S-hospitals. With a close relation between publication numbers and impact factor score, the Rigshospital produced 60%, Hvidovre Hospital 20% and Bispebjerg Hospital 11%, while the four remaining hospitals (Frederiksberg Hospital, the Copenhagen Community Hospital, Sct. Hans Hospital and Sundby Hospital) together produced 9% of the research. The departmental research activities as such showed correlation neither to clinical specialty nor to specific hospitals. In conclusion, the Rigshospital is responsible for most of the research in H:S. Generally, departments headed by university professors showed the highest research activity. 相似文献
60.