全文获取类型
收费全文 | 108990篇 |
免费 | 5597篇 |
国内免费 | 64篇 |
专业分类
林业 | 4549篇 |
农学 | 3177篇 |
基础科学 | 755篇 |
12353篇 | |
综合类 | 21231篇 |
农作物 | 4502篇 |
水产渔业 | 4937篇 |
畜牧兽医 | 55449篇 |
园艺 | 1310篇 |
植物保护 | 6388篇 |
出版年
2018年 | 1278篇 |
2017年 | 1409篇 |
2016年 | 1366篇 |
2015年 | 1144篇 |
2014年 | 1357篇 |
2013年 | 4085篇 |
2012年 | 2765篇 |
2011年 | 3413篇 |
2010年 | 2228篇 |
2009年 | 2181篇 |
2008年 | 3392篇 |
2007年 | 3155篇 |
2006年 | 2994篇 |
2005年 | 2827篇 |
2004年 | 2924篇 |
2003年 | 2852篇 |
2002年 | 2781篇 |
2001年 | 3316篇 |
2000年 | 3334篇 |
1999年 | 2483篇 |
1998年 | 1101篇 |
1997年 | 1106篇 |
1995年 | 1278篇 |
1994年 | 1188篇 |
1993年 | 1161篇 |
1992年 | 2389篇 |
1991年 | 2562篇 |
1990年 | 2465篇 |
1989年 | 2524篇 |
1988年 | 2298篇 |
1987年 | 2364篇 |
1986年 | 2506篇 |
1985年 | 2413篇 |
1984年 | 1946篇 |
1983年 | 1792篇 |
1982年 | 1176篇 |
1981年 | 1139篇 |
1980年 | 1034篇 |
1979年 | 1771篇 |
1978年 | 1431篇 |
1977年 | 1154篇 |
1976年 | 1141篇 |
1975年 | 1178篇 |
1974年 | 1540篇 |
1973年 | 1623篇 |
1972年 | 1591篇 |
1971年 | 1520篇 |
1970年 | 1412篇 |
1969年 | 1264篇 |
1967年 | 1098篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Use of Echinococcus granulosus worm antigens for immunodiagnosis of E. granulosus infection in dogs.
Echinococcus granulosus worm excretory/secretory antigens (WES) were used in ELISA for diagnosis of E. granulosus infection in dogs and compared with protoscolex somatic antigens (PSM). Sera from 224 dogs were tested. There was no correlation between ELISA absorbance values and E. granulosus worm burdens using either antigen. There was a significant linear relationship between absorbance values of sera tested in the ELISA using WES (W-ELISA) and the ELISA using PSM (P-ELISA). However, there was a small but significant difference between the absorbance values of the sera tested against the two antigens. Western blot analysis of WES using sera from E. granulosus-infected and uninfected dogs revealed antigenic components of relative molecular mass (Mr) larger than 94,000, Mr 94,000-68,000 and Mr 43,000-39,000 in worms, and these were specific for E. granulosus and not identified in PSM; these antigenic differences may be responsible for differences in reactivity in ELISA. The sensitivities of W-ELISA and P-ELISA were 80.8% and 75.6%, respectively. The specificities of W-ELISA and P-ELISA were 93.7% and 97.9%, respectively. The reduced specificity in W-ELISA was mainly attributable to increased background reactivity of sera from Taenia hydatigena-infected dogs. Despite the reduction in specificity, both ELISAs are valuable epidemiological tools to determine the prevalence of antibody to E. granulosus in dog populations and to monitor the success of hydatid control campaigns. 相似文献
82.
L G Rickard G L Zimmerman E P Hoberg P W Lockwood D W Weber R Miller 《Veterinary parasitology》1989,33(2):125-133
The effectiveness of the morantel sustained release trilaminate (MSRT) in controlling gastrointestinal nematodes through a grazing season was evaluated using 60 yearling beef stocker calves randomly divided into 2 groups of 30 animals each. In April 1985, the calves comprising the treatment group each received an MSRT designed to release morantel tartrate continuously for 90 days while those of the control group remained unmedicated. All animals were weighed and samples of rectal feces were taken at 14-day intervals, beginning on Day 0, until trial termination (Day 168). At trial termination, 10 control and 10 treated calves were necropsied for recovery of gastrointestinal nematodes. Three sets of parasite-na?ve tracer calves were utilized to evaluate the initial, interim and final levels of pasture contamination by nematode larvae. Overall, the use of the MSRT resulted in a 75.5% reduction (P less than 0.001) in output of nematode eggs from the principals, an 81.8% reduction (P less than 0.001) in numbers of gastrointestinal nematodes in principals (at trial termination), and a 96.9% reduction (P less than 0.05) of pasture larval nematode contamination (as indirectly indicated by parasite burdens in tracer calves). The mean weight advantage of treated calves was 16.6 kg per head (P less than 0.001). 相似文献
83.
R Korbel 《Tier?rztliche Praxis》1991,19(5):497-507
Ocular diseases in birds are very rarely investigated. Increased keeping of often very expensive caged birds makes it necessary for veterinarians in practice to deal with the problems of ornithoophthalmology. Fundamental physiological and anatomic differences between the mammalian and the avian eye, interspecies variables and general problems in handling do not allow a simple transfer of knowledge of mammal ophthalmology to birds. Therefore, it is necessary to find differentiated, species-orientated solutions in investigation as well as suitable treatments of ocular diseases in birds. An update on ornithoophthalmology is given. 相似文献
84.
A field experiment was conducted during the winter seasons of 1992–93 and 1993–94 at Anand to study the effect of FYM, nitrogen and source of fertilizer on growth and yield of mustard [ Brassica juncea (L.) Czernj & Cosson]. The results showed significant variation in leaf area index (LAI), crop growth rate (CGR), dry matter production and seed yield. The direct effect of farmyard manure (FYM) was conspicuous in improving the growth of mustard. FYM application at 10 tonnes ha−1 significantly increased the LAI, CGR and dry matter accumulation per plant at almost all the stages during first year study (1992–93) and in pooled analysis. Similarly, nitrogen application registered maximum LAI, CGR at 75 kg level and RGR and NAR at 50 kg level at almost all the during both years. Sulphur carrying source (Ammonium sulphate plus single super phosphate) increased all stages growth characters. Maximum dry matter accumulation per plant and seed yield were recorded with highest levels of FYM (20 tonnes ha−1 ), N (75 kg ha−1 ) and source having S. Seed yield was strongly associated with LAI and dry matter accumulation per plant at all the stages. 相似文献
85.
R. Zabielski S. G. Pierzynowski 《Journal of animal physiology and animal nutrition》1992,68(3):146-150
Eine Methode zur langfristigen Lymphsammlung aus der jejunalen Lymphbahn bei Schweinen und Schafen Es wird eine Methode zur langfristigen Lymphsammlung im Dünndarmbereich von Schweinen und Schafen vorgestellt. Mit Hilfe eines chirurgischen Eingriffs wurde ein Silikon-Katheder im truncus lymphaticus jejunalis implantiert. Zusätzlich wurde ein zweiter Katheter in die hintere vena cava in Richtung Herz eingesetzt. Beide Katheter wurden sofort miteinander verbunden, um die Wiedereinführung der jejunalen Lymphe in den Blutkreislauf zu gewährleisten. Der negative Druck in der hinteren vena cava im Thoraxteil förderte den Lymphfluß durch das Katheter im truncus lymphaticus jejunalis. Der preprandiale Lymphfluß des Jéjunums betrug bei Schweinen 0,3 ml/h/kg Körpergewicht und stieg postprandial auf 0,78 ml/h/kg an. Beim Schaf betrug der Basiswert 0,75 ml/h/kg. Er stieg nach intraduodenaler Infusion von Rapsöl auf 4,75 ml/h/kg. Eine mechanische Stimulation der intestinalen Receptoren durch 0,9% NaCl-Lösung stimulierte ebenfalls den Lymphfluß. 相似文献
86.
87.
The accumulation of soluble carbohydrates in vegetative parts of sweet sorghum ( Sorghum bicolor (L.) Moench.) represents an intermediate reserve pool for grain filling as well as an irreversible storage up to maturity. In order to study the effect of Sterility on soluble sugar accumulation in vegetative parts, two cytoplasmic male sterile (CMS) lines of sweet sorghum were compared with their corresponding fertile mamtainers for non-structural carbohydrate concentrations in shoots. Plants were harvested at four different physiological stages. The lines showed significant differences in the yield of non-structural carbohydrates. At maturity, the yields of soluble carbohydrates from vegetative parts of the two sterile lines were 93 % and 43 % higher than the yield of the two corresponding fertile lines. At that stage, sucrose represented about 80 % of total soluble carbohydrates and the higher yield of soluble carbohydrates of sterile lines was mainly due to the higher yield of sucrose. This indicates that the yield of extractable carbohydrates, especially sucrose, in vegetative parts of sweet sorghum could be considerably improved by using sterile lines which are utilized in hybrid production. 相似文献
88.
89.
90.