全文获取类型
收费全文 | 948篇 |
免费 | 79篇 |
专业分类
1027篇 |
出版年
2022年 | 9篇 |
2021年 | 12篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 27篇 |
2014年 | 30篇 |
2013年 | 38篇 |
2012年 | 55篇 |
2011年 | 60篇 |
2010年 | 36篇 |
2009年 | 23篇 |
2008年 | 41篇 |
2007年 | 38篇 |
2006年 | 41篇 |
2005年 | 37篇 |
2004年 | 25篇 |
2003年 | 37篇 |
2002年 | 35篇 |
2001年 | 20篇 |
2000年 | 37篇 |
1999年 | 26篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 23篇 |
1991年 | 18篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1975年 | 16篇 |
1974年 | 17篇 |
1973年 | 10篇 |
1972年 | 8篇 |
1971年 | 6篇 |
1967年 | 5篇 |
排序方式: 共有1027条查询结果,搜索用时 6 毫秒
141.
OBJECTIVE: To assess the relation of smoking and alcohol and coffee consumption to active Helicobacter pylori infection. DESIGN: Cross sectional study of patients attending a general practitioner. Active H pylori infection was measured by the 15C-urea breath test and detailed quantitative information on smoking and on alcohol and coffee consumption was obtained by a standardised self administered questionnaire. SETTING: One general practice in Germany. SUBJECTS: 447 patients aged 15-79 who had not had peptic ulcer disease or treatment for H pylori infection. MAIN OUTCOME MEASURES: Prevalence of H pylori infection according to smoking and alcohol and coffee consumption. RESULTS: Overall prevalence of infection was 21% (94/447). There was no significant relation between smoking and active H pylori infection. Alcohol consumption showed a negative dose-response relation and coffee consumption a positive dose-response relation with active infection. After adjustment for potential confounders, the odds ratios for patients who drank < or = 75 g and > 75 g of ethanol a week compared with non-drinkers were 0.90 (95% confidence interval 0.55 to 1.59) and 0.33 (0.16 to 0.68), respectively (P value for trend 0.005, assuming that 1 litre of beer and 0.51 of wine contain on average 50 g of ethanol in south Germany). Adjusted odds ratios for patients who drank < 3 cups and > or = 3 cups of coffee per day compared with those who did not drink coffee were 1.49 (0.71 to 3.12) and 2.49 (1.23 to 5.03), respectively (P value for trend 0.007). CONCLUSION: These results suggest a protective effect of alcohol consumption against active infection with H pylori and an opposite effect of coffee consumption. 相似文献
142.
143.
Great-granny’s Garden: a living archive and a sensory garden 总被引:1,自引:0,他引:1
Since 2003, the Botanical Garden in Oslo has been involved in a project coordinated by the Norwegian Genetic Resource Centre.
The wide range of work supervised by this centre includes conservation of ornamental plants. Our garden has been responsible
for the registration and collecting of ornamentals in Southeast-Norway and has a special responsibility for the conservation
of Paeonia species and cultivars. As a result of the project, Great-granny’s Garden was opened to the public in 2008. It has two objectives.
Firstly, it shall be a living archive of Norway’s horticultural heritage. Although proven hardy, easy to grow, and long-lived,
old varieties of traditional ornamentals are rapidly disappearing. We aim to keep these old-fashioned varieties for sustainable
use in future horticulture and encourage people to use them in present day gardening, both in new gardens and in the restoration
of old ones. Secondly, the garden is designed as a sensory garden for people with dementia, in cooperation with Oslo’s Resource
Centre for Dementia and Psychiatric Care of the Elderly. It is enclosed by a picked fence and by shrubs, offers rest on several
benches, and has a paved and easy to follow round-walk among traditional garden elements and plants with a lush variety of
colours, forms, and scents. A sensory garden stimulates many senses, evokes pleasant emotions, brings out long-forgotten memories,
and stimulates communication. Sensory gardens are therefore considered an important tool in the therapy of dementia. 相似文献
144.
145.
146.
147.
Mutants of Pichia guilliermondii were isolated that lacked homoaconitate hydratase (lys4), homoisocitrate dehydrogenase (lys10) or α-aminoadipate reductase (lys2) and were able to excrete homocitrate into the culture medium. The effects of incubation time and lysine concentration in the medium on the excretion of homocitrate were examined. In the presence of 600 mg of L-lysine/1 in a minimum salt medium P. guilliermondii G75 (lys2) produced about 280 mg homocitrate/1 during 48 h of growth. A simple procedure to isolate homocitrate from the medium is described. 相似文献
148.
149.
150.
D Bode M Heinecke U Schernau 《Biochemical and biophysical research communications》1973,52(4):1234-1240
In the presence of two or polyvalent cations, e. g., Mg2+, protonated ethylenediamine, protonated spermidine, and protonated spermine, poly U forms an ordered structure in aqueous solution. At elevated temperatures, the secondary structure is lost by a cooperative process. The melting temperature Tm rises with the size of the cations. Using IR-spectroscopy, we could show that the secondary structure of poly U is stabilized by hydrogen bonds. Both carbonyl groups of the uracil are involved in the hydrogen bonding. This experimental result enables us to choose the right arrangement for UU base pairing. 相似文献