全文获取类型
收费全文 | 33680篇 |
免费 | 1303篇 |
国内免费 | 10篇 |
专业分类
林业 | 2299篇 |
农学 | 1499篇 |
基础科学 | 269篇 |
5762篇 | |
综合类 | 4361篇 |
农作物 | 1598篇 |
水产渔业 | 1793篇 |
畜牧兽医 | 13974篇 |
园艺 | 952篇 |
植物保护 | 2486篇 |
出版年
2019年 | 250篇 |
2018年 | 1602篇 |
2017年 | 1697篇 |
2016年 | 957篇 |
2015年 | 372篇 |
2014年 | 458篇 |
2013年 | 959篇 |
2012年 | 1180篇 |
2011年 | 2051篇 |
2010年 | 1886篇 |
2009年 | 1660篇 |
2008年 | 1751篇 |
2007年 | 1950篇 |
2006年 | 811篇 |
2005年 | 814篇 |
2004年 | 689篇 |
2003年 | 781篇 |
2002年 | 654篇 |
2001年 | 808篇 |
2000年 | 822篇 |
1999年 | 633篇 |
1998年 | 274篇 |
1997年 | 282篇 |
1995年 | 260篇 |
1994年 | 227篇 |
1993年 | 253篇 |
1992年 | 463篇 |
1991年 | 516篇 |
1990年 | 435篇 |
1989年 | 431篇 |
1988年 | 421篇 |
1987年 | 411篇 |
1986年 | 364篇 |
1985年 | 388篇 |
1984年 | 339篇 |
1983年 | 287篇 |
1982年 | 243篇 |
1979年 | 383篇 |
1978年 | 289篇 |
1977年 | 308篇 |
1976年 | 299篇 |
1975年 | 317篇 |
1974年 | 332篇 |
1973年 | 303篇 |
1972年 | 291篇 |
1971年 | 246篇 |
1969年 | 292篇 |
1968年 | 287篇 |
1967年 | 333篇 |
1966年 | 304篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
943.
Pasmo Disease of Linseed in Scotland 总被引:1,自引:0,他引:1
S. J. I. HOLMES 《Plant pathology》1976,25(1):61-61
944.
Chronic brucellosis was produced in the rabbit by parental and penicillin-induced L-phase revertant of Brucella canis. Animals in the experimental groups were injected with 1.2 x 10(8) organisms/ml of appropriate strains by specified routes at intervals. At a maximum of 12 weeks postinfection, animals were killed and samples were taken for bacteriology, serology, histology, immunofluorescent and electron microscopy. Results revealed faecal shedding in some animals from 72 hours up to three weeks postinfection. High agglutinating antibody titres of 1:1280 were sustained in all infected animals. Histopathological and ultrastructural changes attributed to the invading organisms were apparent and evidence of mitochrondriopathic changes are provided. The implication and indirect role of L-phase in brucellosis are discussed. 相似文献
945.
946.
T. Linares W. A. King K. Larsson I. Gustavsson A. Bane 《Veterinary research communications》1980,4(1):113-118
A total of 55 non-surgical collections, 7 days after spontaneous heat, was made in 19 heifers. Recovery rate was 57% (17/30) from 10 repeat breeder heifers and 72% (18/25) from 9 virgin heifers, this difference was not significant. Fertilization rate in both groups was 94%. The eggs were always recovered in the first 100 ml of flushing medium. Mean lengths of oestrous cycle after non-surgical collection were, respectively, 16.9 and 18.1 days in repeat breeder and virgin heifers. This difference was not significant. However, the cycle in which the first collection was made was significantly shorter (P<.005) than the cycle immediately before the collections. Only 61% of possible eggs were non-surgically collected from 4 superovulated repeat breeder cows and no further eggs were found after slaughter, one to two hours later. 相似文献
947.
Procedures designed to extract pseudorabies viral (PRV) antigens from PRV-infected tissue cultures were investigated to determine whether differences in extraction method had an effect upon the final concentrated antigenic product. All four of the preparations made from PRV-infected tissue culture cells (trypsin extract and disrupted cells) or entire PRV-infected cultures (polysorbate 80 extract and (NH4)2SO4 precipitate) contained relatively large amounts of the same antigen, whereas cell-free PRV-infected tissue culture fluids did not contain significant amounts of this antigen. Specific antibody directed against this antigen was present in all PRV antisera tested. Two other antigens were observed in some of the preparations, but PRV antisera varied in their ability to precipitate with these antigens. Therefore, the number of precipitation lines observed in agar gel immunodiffusion between PRV preparations and PRV-positive antisera depended both upon the extraction method used to obtain the antigen and upon the specificity of the selected antiserum. 相似文献
948.
The use of the rapid quantitative plate agglutination test (QPAT) utilizing triphenyltetrazolium chloride (TTC) stained antigen for the differentiation of bovine brucellosis and yersiniosis is described. It was found with experimental laboratory animals and cattle, that titres against homologous antigen tended to exceed titres against heterologous antigen and that this reaction together with measurement of the Yersinia OH agglutinin titre could be used for purposes of differentiation. It was, however, not possible to differentiate these infections in serum from cattle with naturally-occurring antibodies. It was also shown that Brucella 0 agglutination in the QPAT was very weak in some sera with high titred anti-Brucella antibodies by serum agglutination, while Yersinia 0 agglutination was not. The QPAT, using Yersinia 0 antigen, therefore correlated well with the results obtained using Brucella 0 antigen in serum agglutination tests. It is suggested that Yersinia 0 antigen may be a suitable antigen for use in rapid agglutination tests because of this relative insusceptibility to false negative results. 相似文献
949.
950.