全文获取类型
收费全文 | 315517篇 |
免费 | 17094篇 |
国内免费 | 699篇 |
专业分类
林业 | 24528篇 |
农学 | 14199篇 |
基础科学 | 3000篇 |
46770篇 | |
综合类 | 43010篇 |
农作物 | 17471篇 |
水产渔业 | 18103篇 |
畜牧兽医 | 133982篇 |
园艺 | 6501篇 |
植物保护 | 25746篇 |
出版年
2019年 | 3727篇 |
2018年 | 4348篇 |
2017年 | 4777篇 |
2016年 | 5044篇 |
2015年 | 4492篇 |
2014年 | 5845篇 |
2013年 | 16528篇 |
2012年 | 7896篇 |
2011年 | 10177篇 |
2010年 | 7994篇 |
2009年 | 8424篇 |
2008年 | 9486篇 |
2007年 | 8653篇 |
2006年 | 9102篇 |
2005年 | 8351篇 |
2004年 | 8148篇 |
2003年 | 7902篇 |
2002年 | 7293篇 |
2001年 | 8303篇 |
2000年 | 7900篇 |
1999年 | 6992篇 |
1998年 | 4374篇 |
1997年 | 4414篇 |
1996年 | 4138篇 |
1995年 | 4803篇 |
1994年 | 4267篇 |
1993年 | 3950篇 |
1992年 | 5738篇 |
1991年 | 5958篇 |
1990年 | 5783篇 |
1989年 | 5745篇 |
1988年 | 5209篇 |
1987年 | 5289篇 |
1986年 | 5339篇 |
1985年 | 5426篇 |
1984年 | 4874篇 |
1983年 | 4484篇 |
1982年 | 3459篇 |
1981年 | 3308篇 |
1980年 | 3242篇 |
1979年 | 4341篇 |
1978年 | 3752篇 |
1977年 | 3386篇 |
1976年 | 3103篇 |
1975年 | 3085篇 |
1974年 | 3758篇 |
1973年 | 3684篇 |
1972年 | 3499篇 |
1971年 | 3312篇 |
1970年 | 3135篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
943.
944.
Intensive microearthquake swarms with the appearance of volcanic tremor have been observed in the southwest part of Long Valley caldera, southeastern California. This activity, possibly associated with magma injection, began 6 weeks after several strong (magnitude 6+) earthquakes in an area south of the caldera and has continued sporadically to the present time. The earthquake sequence and magmatic activity are part of a broad increase in tectonic activity in a 15,000-square-kilometer region surrounding the "White Mountains seismic gap," an area with high potential for the next major earthquake in the western Great Basin. 相似文献
945.
946.
Keane DP Horney FD Ogilvie TH 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(2):57-59
A four day old Holstein calf was presented with a history of recurrent free gas bloat. An exploratory laparotomy was performed and no abnormalities were discovered in the gastrointestinal tract. An esophagotracheal fistula was suspected and confirmed by endoscopy. Surgical correction was performed by ligating the tubular connection between the trachea and esophagus and suturing closed the defects in these structures. 相似文献
947.
Examination of the origin of increased equine serum alkaline phosphatase concentrations 总被引:2,自引:0,他引:2
Trueman KF Lumsden JH McSherry BJ 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(4):108-111
Serum alkaline phosphatase activity was found to be increased in 32.6% of equine samples analyzed at the Ontario Veterinary College over an 18 month period. An attempt was made using sensitivity to L-phenylalanine and heat to identify the origin of increased serum alkaline phosphatase isoenzymes present in 44 clinical cases. No difference in sensitivity to either procedure was observed for serum alkaline phosphatase from groups of foals and horses representing different clinical problems. Alkaline phosphatase of osseous tissue origin appeared to be the major source of activity for each group of animals reported. 相似文献
948.
949.
Lavigne C Smith HJ 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(12):389-390,391
In 1982, approximately 13,000 Canadian cattle were treated once for sarcoptic mange with ivermectin at a dose of 10 mg per 45.4 kg of body weight. The results showed 100% efficacy against Sarcoptes scabiei and other ectoparasites present. All cattle showed marked improvement in general condition with new hair growth and apparent weight gains by 31 days posttreatment. Surveillance of treated herds for a year following treatment showed that one parenteral treatment with ivermectin eradicated the disease from closed herds. 相似文献
950.
This paper concerns the taxonomic status of the F38-like group (MacOwan), a prime determinant of contagious caprine pleuropneumonia (CCPP). Extensive biochemical and serological investigations on strain F38 are reported. Some complex serological relationships with other mycoplasma species are revealed. The results, taken in conjunction with earlier published work on geno-typic characters, lead to the conclusion that final classification of these organisms should await further comparative studies of a number of field strains with a related group of strains classified as M. capri-colum.The characterization of F38 confirms its partial relationship to the “M. mycoides group” of ovine/caprine/bovine mycoplasmas, and has also revealed a very close phenotypic relationship to the bovine mycoplasma serogroup 7, a finding of potential diagnostic and epidemiological importance.Key words: mycoplasmas, classification, F38-like group 相似文献