全文获取类型
收费全文 | 2237篇 |
免费 | 218篇 |
专业分类
2455篇 |
出版年
2023年 | 22篇 |
2022年 | 47篇 |
2021年 | 83篇 |
2020年 | 33篇 |
2019年 | 43篇 |
2018年 | 72篇 |
2017年 | 55篇 |
2016年 | 67篇 |
2015年 | 84篇 |
2014年 | 111篇 |
2013年 | 157篇 |
2012年 | 167篇 |
2011年 | 127篇 |
2010年 | 87篇 |
2009年 | 66篇 |
2008年 | 90篇 |
2007年 | 71篇 |
2006年 | 81篇 |
2005年 | 73篇 |
2004年 | 54篇 |
2003年 | 58篇 |
2002年 | 50篇 |
2001年 | 43篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 14篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 19篇 |
1992年 | 39篇 |
1991年 | 33篇 |
1990年 | 36篇 |
1989年 | 36篇 |
1988年 | 25篇 |
1987年 | 27篇 |
1986年 | 38篇 |
1985年 | 30篇 |
1984年 | 32篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 25篇 |
1978年 | 17篇 |
1977年 | 20篇 |
1976年 | 20篇 |
1975年 | 24篇 |
1974年 | 24篇 |
排序方式: 共有2455条查询结果,搜索用时 15 毫秒
991.
992.
U K Verma D J Brenner W L Thacker R F Benson G Vesey J B Kurtz P J Dennis A G Steigerwalt J S Robinson C W Moss 《International journal of systematic bacteriology》1992,42(3):404-407
A Legionella-like organism (strain 214T [T = type strain]) was isolated from a cooling tower in Stratford-upon-Avon, England. This strain required L-cysteine and contained cellular branched-chain fatty acids that are typical of the genus Legionella. Strain 214T produced pink colonies on buffered charcoal-yeast extract agar. Ubiquinone Q-12 was the major quinone. Strain 214T was serologically distinct from other legionellae as determined by a slide agglutination test. The results of DNA hybridization studies showed that strain 214T (= ATCC 49655T) is a member of a new Legionella species, Legionella shakespearei. 相似文献
993.
This study was conducted on 110 cross-bred Hisardale x Nali ewes. The ewes were divided into two groups: one group was treated with 2 ml of polyandroalbumin subcutaneously (s.c.) twice at an interval of 28 d, with breeding rams introduced 28 d after the second injection of the drug. The second group served as the untreated controls. Of the 55 ewes in each group, 52 were mated during the 40 d breeding period. The occurance of estrus and estrous cycle length were the same in the two groups. Fortysix ewes in the treated group and 47 ewes in the control group lambed, producing 55 and 47 lambs, respectively. In the treated group, the lambing rate, fecundity and fertility were 100, 96.36 and 88.46%, while these values for the control group were 85.45, 83.64 and 90.38%. Prolificity rates were 1.15 and 0.98 for the treated and control group, respectively. 相似文献
994.
995.
996.
Mean respiratory quotients determined on samples from individual drones by Cartesian diver respirometry averaged 0·64, suggesting that phospholipids constitute the major source of energy. The average sperm density of semen was 7·76 millions/μl. Dilution of semen increased the rate of oxygen consumption by 68 per cent. Semen stored at 13 to 14°C for 1 month showed only 40 per cent of the oxygen uptake of freshly ejaculated semen. Streptomycin sulphate treated samples of semen showed significantly lower rates of oxygen consumption than untreated samples. These results suggest that the high density of sperm in the semen and low metabolic activity during storage may be at least partly responsible for the successful long-term storage of honey-bee spermatozoa. 相似文献
997.
Organizational changes in phospholipid multibilayers induced by uncouplers of oxidative phosphorylation: a spin label study 总被引:2,自引:0,他引:2
A cholestane spin probe was used to study the effect of uncouplers of oxidative phosphorylation (2,4-dinitrophenol, pentachlorophenol and dicumarol) on the degree of organization of phospholipids in hydrated multibilayers. Disruptive effects were observed—their magnitude depending on pH, time and the presence of cholesterol. A correlation between changes in probe organization and ion conductivity, with maximum effects at the pH corresponding to the pK of the uncoupler, could be demonstrated in the films containing cholesterol. Egg lecithin films containing no cholesterol were disordered maximally at pH 4.0 irrespective of the uncoupler used. The effect of uncouplers on the probe disorganization varied with time after exposure. These time effects indicated that relative movement of uncoupler, probe and lipid molecules occur to produce lipid organizations differing from those after initial exposure to uncoupler. The results show that even in a simple model system uncoupler effects may be complex, and suggest that changes in bilayer lipid organization parameters may play a role in uncoupling oxidative phosphorylation. 相似文献
998.
Mode of germination and effect of various substrates, temperature, humidities, light and darkness on germination of poppy powdery mildew conidia have been studied.Conidia germinated on all substrates tested. Highest germination (89.41 %) was on agar 2 %. Germination was equally good on dry slide and in water. Generally one, rarely two germ tubes emerged from each conidium from the corner or occasionally from other places. Germination started after two hours of incubation and was almost over in 5 hours. Germination energy was 86.2.Maximum temperature for germination was 32.5 C. Optimum lied near 20 C.Light and darkness did not affect germination.Conidia germinated at all relative humidities tested including 0 and 100 %.Department of Plant Pathology, Agricultural Experiment Station, University of Udaipur, Udaipur, India.Based on a part of Ph.D. thesis of the senior author. 相似文献
999.
1000.