首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5868篇
  免费   411篇
  国内免费   3篇
林业   149篇
农学   123篇
基础科学   50篇
  642篇
综合类   1476篇
农作物   193篇
水产渔业   226篇
畜牧兽医   3175篇
园艺   62篇
植物保护   186篇
  2018年   70篇
  2017年   67篇
  2016年   78篇
  2015年   56篇
  2014年   88篇
  2013年   231篇
  2012年   165篇
  2011年   185篇
  2010年   107篇
  2009年   106篇
  2008年   204篇
  2007年   197篇
  2006年   204篇
  2005年   180篇
  2004年   181篇
  2003年   191篇
  2002年   162篇
  2001年   142篇
  2000年   169篇
  1999年   149篇
  1998年   71篇
  1997年   66篇
  1996年   51篇
  1995年   54篇
  1993年   51篇
  1992年   125篇
  1991年   126篇
  1990年   123篇
  1989年   121篇
  1988年   99篇
  1987年   94篇
  1986年   137篇
  1985年   152篇
  1984年   119篇
  1983年   113篇
  1982年   70篇
  1981年   86篇
  1980年   65篇
  1979年   110篇
  1978年   98篇
  1977年   59篇
  1976年   50篇
  1975年   54篇
  1974年   57篇
  1973年   77篇
  1972年   77篇
  1971年   67篇
  1970年   57篇
  1969年   62篇
  1968年   62篇
排序方式: 共有6282条查询结果,搜索用时 15 毫秒
141.
Abstract— The author reviews rabies in man. Reference is made to sources of infection, the course of the disease in man, prophylactic vaccination, post-infection prophylaxis and possible complications.
Résumé— –L'auteur examine la question de la rage chez l'homme: sources d'infection, évolution de la maladie, vaccination prophylactique, prophylaxie après contage et complications possibles.
Zusammenfassung— Der Verfasser bespricht das Auftreten von Tollwut bei Menschen. Er weist auf die Infektionsquellen hin, beschreibt den Verlauf der Krankheit bei Menschen, vorbeugende Impfungen, Vorbeugungsmassnahmen nach einer Infektion und mögliche Komplikationen.  相似文献   
142.
143.
144.
Seven Florida sandhill cranes (Grus canadensis pratensis) and 6 greater sandhill cranes (Grus canadensis tabida) were exposed to lead-base paint containing 27% lead. One bird of each subspecies died enroute to the hospital, with a clinical history of anorexia, weakness, and open-mouth breathing of 36 hours' duration. There were no gross lesions, and microscopic lesions were limited to focal hepatic necrosis and hemosiderosis. Two of each subspecies of cranes developed clinical signs of lead poisoning, which included anorexia, weakness, green diarrhea, regurgitation, and open-mouth breathing. Diagnosis of lead poisoning was confirmed on the basis of blood lead concentrations ranging from 146 microgram/100 ml to 378 microgram/100 ml. These 4 cranes were treated successfully with calcium disodium edetate intramuscularly. Seven of the birds remained clinically normal despite high blood lead levels, especially in the greater sandhill cranes.  相似文献   
145.
Inexperienced hand-reared motmots avoided a pattern of red and yellow rings but readily attacked a pattern of green and blue rings and also one of red and yellow stripes. The motmots' avoidance of the "coral snake%" pattern indicates that mimic snake species can derive protection from some potential predators.  相似文献   
146.
Bovine enzootic haematuria in New Zealand   总被引:1,自引:0,他引:1  
  相似文献   
147.
Tear production was evaluated in 39 horses and 29 ponies using Schirmer tear test strips to determine whether diurnal or weekly fluctuations occur, whether location of strip placement has an effect, if values are the same for both eyes in an animal and whether sex, age, stabling vs. pasture and winter vs. summer had an effect. There was no test in which the raw score was less than 10 mm, although there were many occasions where tear wetting exceeded 35 mm. Analysis of the raw (continuous) scores by linear regression provided no evidence that signalment, housing or season or location of strip placement affected results. The distribution of tear test scores for a 'population' of eyes did not differ when the right eye was compared with the left eye or when the same eye was compared at different times on the same day. Individual test wetting values for opposing eyes measured at the same time, and also wetting values for the same eye measured at different times on the same day sometimes differed substantially. In winter maximum tear wetting exceeded 35 mm more frequently in the STT I than in the STT II even in housed horses and ponies, but there was no consistent significant difference. There appears to be wide variability in the STT I in normal horses and ponies.  相似文献   
148.
ABSTRACT Ninety-five isolates of Colletotrichum including 81 isolates of C. acutatum (62 from strawberry) and 14 isolates of C. gloeosporioides (13 from strawberry) were characterized by various molecular methods and pathogenicity tests. Results based on random amplified polymorphic DNA (RAPD) polymorphism and internal transcribed spacer (ITS) 2 sequence data provided clear genetic evidence of two subgroups in C. acutatum. The first subgroup, characterized as CA-clonal, included only isolates from strawberry and exhibited identical RAPD patterns and nearly identical ITS2 sequence analysis. A larger genetic group, CA-variable, included isolates from various hosts and exhibited variable RAPD patterns and divergent ITS2 sequence analysis. Within the C. acutatum population isolated from strawberry, the CA-clonal group is prevalent in Europe (54 isolates of 62). A subset of European C. acutatum isolates isolated from strawberry and representing the CA-clonal and CA-variable groups was assigned to two pathogenicity groups. No correlation could be drawn between genetic and pathogenicity groups. On the basis of molecular data, it is proposed that the CA-clonal subgroup contains closely related, highly virulent C. acutatum isolates that may have developed host specialization to strawberry. C. gloeosporioides isolates from Europe, which were rarely observed were either slightly or nonpathogenic on strawberry. The absence of correlation between genetic polymorphism and geographical origin in Colletotrichum spp. suggests a worldwide dissemination of isolates, probably through international plant exchanges.  相似文献   
149.
A 3-year-old, female African pygmy hedgehog (Atelerix albiventris) was referred with a history of hematuria. Hyperglycemia and glucosuria were found at presentation. Mammary adenocarcinoma and a granulosa cell tumor were found and removed surgically. Glucosuria and hematuria resolved, and the hedgehog has done well for 10 mo postoperatively.  相似文献   
150.
The objective of the present study was to detect quantitative trait loci for economically important traits in a family from a Bos indicus x Bos taurus sire. A Brahman x Hereford sire was used to develop a half-sib family (n = 547). The sire was mated to Bos taurus cows. Traits analyzed were birth (kg) and weaning weights (kg); hot carcass weight (kg); marbling score; longissimus area (cm2); USDA yield grade; estimated kidney, pelvic, and heart fat (%); fat thickness (cm); fat yield (%); and retail product yield (%). Meat tenderness was measured as Warner-Bratzler shear force (kg) at 3 and 14 d postmortem. Two hundred and thirty-eight markers were genotyped in 185 offspring. One hundred and thirty markers were used to genotype the remaining 362 offspring. A total of 312 markers were used in the final analysis. Seventy-four markers were common to both groups. Significant QTL (expected number of false-positives < 0.05) were observed for birth weight and longissimus area on chromosome 5, for longissimus area on chromosome 6, for retail product yield on chromosome 9, for birth weight on chromosome 21, and for marbling score on chromosome 23. Evidence suggesting (expected number of false-positives < 1) the presence of QTL was detected for several traits. Putative QTL for birth weight were detected on chromosomes 1, 2, and 3, and for weaning weight on chromosome 29. For hot carcass weight, QTL were detected on chromosomes 10, 18, and 29. Four QTL for yield grade were identified on chromosomes 2, 11, 14, and 19. Three QTL for fat thickness were detected on chromosomes 2, 3, 7, and 14. For marbling score, QTL were identified on chromosomes 3, 10, 14, and 27. Four QTL were identified for retail product yield on chromosomes 12, 18, 19, and 29. A QTL for estimated kidney, pelvic, and heart fat was detected on chromosome 15, and a QTL for meat tenderness measured as Warner-Bratzler shear force at 3 d postmortem was identified on chromosome 20. Two QTL were detected for meat tenderness measured as Warner-Bratzler shear force at 14 d postmortem on chromosomes 20 and 29. These results present a complete scan in all available progeny in this family. Regions underlying QTL need to be assessed in other populations.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号