全文获取类型
收费全文 | 1365篇 |
免费 | 148篇 |
出版年
2020年 | 17篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 26篇 |
2014年 | 35篇 |
2013年 | 48篇 |
2012年 | 50篇 |
2011年 | 60篇 |
2010年 | 38篇 |
2009年 | 29篇 |
2008年 | 42篇 |
2007年 | 50篇 |
2006年 | 44篇 |
2005年 | 46篇 |
2004年 | 46篇 |
2003年 | 48篇 |
2002年 | 36篇 |
2001年 | 39篇 |
2000年 | 46篇 |
1999年 | 42篇 |
1998年 | 23篇 |
1996年 | 11篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 27篇 |
1991年 | 26篇 |
1990年 | 32篇 |
1989年 | 30篇 |
1988年 | 32篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 33篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 22篇 |
1977年 | 16篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1974年 | 14篇 |
1973年 | 13篇 |
1971年 | 14篇 |
1970年 | 13篇 |
1969年 | 12篇 |
1968年 | 11篇 |
1967年 | 18篇 |
排序方式: 共有1513条查询结果,搜索用时 15 毫秒
31.
Apparatus for the partial freezing of liquid nitrogen for the rapid cooling of cells and tissues 总被引:2,自引:0,他引:2
A P MacKenzie 《Biodynamica》1969,10(215):341-351
32.
Evaluation of Factors Related to Growth of Rift Valley Fever Virus in Suspended Cell Cultures 总被引:2,自引:2,他引:0 下载免费PDF全文
Jerry S. Walker Richard C. Carter Frederick Klein Shirley E. Snowden Ralph E. Lincoln 《Applied microbiology》1969,17(5):658-664
The effect of several controlled variables on the peak titer and fold increase of Rift Valley fever virus grown in suspension culture on two variants of Earle's L cell, L-DR and L-MA clone 1-1, was studied. No significant amount of cell-associated virus was found at 24 hr, indicating a release of virus soon after its formation. Mild sonic treatment of the virus produced in serum-free medium increased the infective titer about 10x. This difference was not observed with virus produced in medium supplemented with serum. Peak titer was not affected by medium used during the infection period, by multiplicity of inoculum (MOI), or by initial cell concentration within the test range of 10(4) to 2 x 10(6) cell/ml. Cell strain employed influenced titer, because the L-DR cell did not produce virus efficiently at low MOI and low initial cell concentration. The time of peak titer and fold replication was dependent on MOI and initial cell concentration. Differences in virus propagation in monolayer and suspension systems are discussed. 相似文献
33.
Two Colombian species described earlier by the authors underPrionosciadium, and a hitherto unnamed collection from the same country are systematically compared with North AmericanPrionosciadium and the monotypic generaCotopaxia (Ecuador) andPerissocoeleum (Colombia). Habit, foliage, inflorescence, fruit, and distribution all suggest that the páramo species exhibit considerable unity ifCotopaxia is excluded. It is indicated also that the genusPrionosciadium has been attributed to South America incorrectly. Despite the somewhat discordant evidence obtained from pollen morphology, it is concluded that the most feasible disposition of the four Colombian plants is to unite them underPerissocoeleum. 相似文献
34.
Value of field data for extrapolation in anthrax 总被引:8,自引:0,他引:8
35.
Pathophysiological and biochemical changes in anthrax 总被引:4,自引:0,他引:4
36.
Jerry S. Walker Frederick Klein Ralph E. Lincoln Albert L. Fernelius 《Journal of bacteriology》1967,94(3):552-556
Rats, rabbits, swine, guinea pigs, and monkeys were infected with anthrax spores, and their temperature responses were recorded. These were characteristic for a species and appeared independent of resistance or susceptibility of the species toward establishment of the disease. The rabbit appeared unique in that it not only failed to demonstrate a dose-response relationship over an 8-log dose range, but acted independently producing erratic body temperatures depending on spore dose. This limits the usefulness of the rabbit in studying anthrax pathogenesis, and poses questions regarding published data with the rabbit as the test animal. 相似文献
37.
38.
39.
40.
OBJECTIVE--To investigate the effects of phenoxymethylpenicillin and erythromycin on urinary isolates from patients with untreated asymptomatic bacteriuria. DESIGN--Retrospective study of subgroup of patients from cohort followed up till the end of 1986. SETTING--Outpatient clinic for children with urinary tract infections. PATIENTS--51 Girls aged under 15 with untreated asymptomatic bacteriuria. INTERVENTIONS--Before 1982 intercurrent infections (mostly tonsillitis or otitis) were treated with phenoxymethylpenicillin; after 1982 erythromycin treatment was preferred. END POINTS--Change of bacterial strain in urinary tract and symptomatic recurrences of disease. MEASUREMENTS AND MAIN RESULTS--Bacteria identified by serotype and electrophoretic type and compared before and after antibiotic treatment. Bacteriuria eradicated and replaced by new strains in most patients treated with phenoxymethylpenicillin, leading to symptomatic recurrences in about 15%. Conversely, patients given erythromycin rarely showed change in bacteriuria and none suffered symptomatic recurrence. CONCLUSIONS--In girls with untreated asymptomatic bacteriuria the use of phenoxymethylpenicillin for intercurrent infections may lead to a change of urinary bacteria and leave them at substantial risk of acute pyelonephritis. With erythromycin this risk is small (2/20 courses in this series). 相似文献