全文获取类型
收费全文 | 973篇 |
免费 | 128篇 |
专业分类
林业 | 27篇 |
农学 | 24篇 |
基础科学 | 3篇 |
119篇 | |
综合类 | 60篇 |
农作物 | 46篇 |
水产渔业 | 70篇 |
畜牧兽医 | 695篇 |
园艺 | 19篇 |
植物保护 | 38篇 |
出版年
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 24篇 |
2018年 | 22篇 |
2017年 | 22篇 |
2016年 | 33篇 |
2015年 | 16篇 |
2014年 | 33篇 |
2013年 | 53篇 |
2012年 | 48篇 |
2011年 | 50篇 |
2010年 | 23篇 |
2009年 | 22篇 |
2008年 | 43篇 |
2007年 | 42篇 |
2006年 | 32篇 |
2005年 | 26篇 |
2004年 | 47篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 41篇 |
2000年 | 33篇 |
1999年 | 27篇 |
1998年 | 15篇 |
1997年 | 7篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 14篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1977年 | 7篇 |
1975年 | 11篇 |
1974年 | 17篇 |
1973年 | 12篇 |
1972年 | 10篇 |
1971年 | 6篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1968年 | 8篇 |
1967年 | 7篇 |
1966年 | 10篇 |
排序方式: 共有1101条查询结果,搜索用时 15 毫秒
131.
Infection of normal adult cattle and sporadic serological Brucella abortus reactors, which no longer had diagnostic titers to B. abortus, with a culture of Escherichia coli isolated from a cow (or its environment) resulted in the production of a primary IgM serum antibody response to both B. abortus and E. coli. Cattle injected with heat killed E. coli and guinea pigs or young calves lacking natural agglutinins to B. abortus injected with live E. coli, produced serum antibody only to E. coli. The subsequent reinjections of live E. coli into the former two groups of cattle resulted in all but one animal in each group producing IgM ‘secondary’ responses to B. abortus of decreasing magnitude, while the anti-E. coli responses increased and eventually switched to synthesis of IgG class antibody. The remaining two animals produced a series of ‘secondary’ responses of IgM antibody to B. abortus similar in amplitude and duration to the primary immune response. The anti-E. coli agglutinins of these two animals increased in titer and IgG class antibody to E. coli was evident after several injections of E. coli. These results indicate that infection of cattle by E. coli can cause a problem in the serological fiagnosis of B. abortus infection. Speculations on the cause of this cross-reaction and ways of minimizing misdiagnosis are discussed. 相似文献
132.
Feed intake data were collected every 6 h in a 140-d feeding trial involving two pens of 15 bull calves, each using one Pinpointer single-animal feeding stall per pen. Spectral analysis of these data revealed strong cyclic patterns of feed intake. These patterns were unique to each animal and consisted of two or more cycle lengths, some up to 28 d, for each animal. Feed intake behavior is an important factor in many forms of animal experimentation. Animal researchers frequently use row-column designs, where columns represent animals and rows represent periods. Latin squares and crossover designs are common examples. Standard analysis of variance procedures are appropriate for these experiments only if certain assumptions are met; one is that if cyclic variation is present, it is identical for all animals, i.e., there is no row X column interaction. If this assumption is not satisfied, standard analysis of variance procedures will result in upward bias of the mean square error and may result in serious distortion of treatment effect estimates. This occurred using the data from the feeding trial reported in this paper. Time-series analysis of covariance greatly improved the accuracy and efficiency of estimates of treatment effects. Consideration of variations in cyclic behavior should be part of the design process in experiments using feed intake data. Guidelines for the design of experiments to take advantage of time-series methodology are given. 相似文献
133.
Haemolysis in gel test for detecting bovine antibodies to Brucella abortus lipopolysaccharide 总被引:2,自引:0,他引:2
Optimal reagent parameters for a haemolysis in gel test for detection of bovine anti-Brucella abortus antibody were established. Using an alkali-treated crude lipopolysaccharide antigen attached to J-negative bovine erythrocytes, 0.125 mg of antigen, 0.1 ml of erythrocytes and 0.4 ml of guinea pig complement were required to perform 15 tests with appropriate serum controls. The haemolysis in gel test and an IgM radioimmunoassay (RIA) procedure were compared for their ability to detect the onset of increased serum antibody levels and antibody levels in sera diluted to extinction. While the RIA was more sensitive in amount of antibody detected, the haemolysis in gel test was equally able to detect initiation of antibody synthesis. 相似文献
134.
135.
Two electrophoretically different carbonic anhydrase (Ca) isoenzymes have been demonstrated in cattle where their presence is presumed to be controlled by codominant allelic genes (Sartore & Bernoco 1966). Previous reports of Ca polymorphism in swine are not available. 相似文献
136.
137.
The bovine immune response to Brucella abortus I. A water soluble antigen precipitated by sera of some naturally infected cattle. 下载免费PDF全文
Selected sera from cattle naturally infected with Brucella abortus precipitate water soluble antigens extracted by sonication from B. abortus. One of these antigens resembles antigen E (Baughn and Freeman) as it is excluded from Sephadex G-200 gels, migrates anodally when electrophoresed at pH 8.6, resists heating at 100 degrees C for ten minutes and appears to be susceptible to papain digestion. Precipitins specific for this antigen remained in sera from which all detectable Brucella agglutinating antibody had been removed by adsorption with live or heat killed B. abortus. The antigen has been extracted from smooth and rough strains of B abortus. Precipitins specific for this antigen have been detected in antisera produced against Brucella canis. 相似文献
138.
Experimental Edema Disease of Swine (E. Coli ENTEROTOXEMIA) II. The Development of Hypertension After the Intravenous Administration of Edema Disease Principle 下载免费PDF全文
The intravenous inoculation of edema disease principle induced profound hypertension in pigs. The increase in blood pressure occurred approximately 40 hours after inoculation and coincided with the development of the characteristic neurological disturbance of edema disease. Therefore hypertension may play a pathogenetic role in the neuropathy of experimental edema disease. 相似文献
139.
140.