全文获取类型
收费全文 | 47328篇 |
免费 | 2061篇 |
国内免费 | 22篇 |
专业分类
林业 | 2827篇 |
农学 | 1508篇 |
基础科学 | 261篇 |
7794篇 | |
综合类 | 4963篇 |
农作物 | 2044篇 |
水产渔业 | 2304篇 |
畜牧兽医 | 23703篇 |
园艺 | 768篇 |
植物保护 | 3239篇 |
出版年
2021年 | 437篇 |
2020年 | 482篇 |
2019年 | 473篇 |
2018年 | 1202篇 |
2017年 | 1308篇 |
2016年 | 1142篇 |
2015年 | 920篇 |
2014年 | 1110篇 |
2013年 | 2388篇 |
2012年 | 2065篇 |
2011年 | 2148篇 |
2010年 | 1304篇 |
2009年 | 1146篇 |
2008年 | 1786篇 |
2007年 | 1704篇 |
2006年 | 1417篇 |
2005年 | 1935篇 |
2004年 | 1803篇 |
2003年 | 1524篇 |
2002年 | 1034篇 |
2001年 | 1104篇 |
2000年 | 981篇 |
1999年 | 861篇 |
1998年 | 315篇 |
1997年 | 281篇 |
1995年 | 332篇 |
1992年 | 578篇 |
1991年 | 606篇 |
1990年 | 640篇 |
1989年 | 623篇 |
1988年 | 549篇 |
1987年 | 500篇 |
1986年 | 558篇 |
1985年 | 492篇 |
1984年 | 453篇 |
1983年 | 404篇 |
1979年 | 613篇 |
1978年 | 427篇 |
1977年 | 461篇 |
1976年 | 548篇 |
1975年 | 608篇 |
1974年 | 670篇 |
1973年 | 598篇 |
1972年 | 575篇 |
1971年 | 484篇 |
1970年 | 476篇 |
1969年 | 544篇 |
1968年 | 555篇 |
1967年 | 572篇 |
1966年 | 539篇 |
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
71.
With the help of a new synthetic material follicles and corpora lutea from the ovaries of 80 cows in different stages of the sexual cycle were examined for modifications of their blood vessel architecture. In the theca externa the main artery which runs towards the follicle, separates into arterioles of which capillaries derive in the theca interna, building a basket-like network around the zona granulosa. After ovulation the follicle wall forms characteristic fields. Capillaries grow into the zona granulosa and thus the folds form the lobular structure of the corpus luteum. Capillaries which rise from the ruptured part of the follicle, spread centripetally and together with lutein cells they build up the not lobulated cupola of the corpus luteum. The regression of the corpus luteum starts around the 16th day of the cycle, beginning at the capillary network of the cupola. A contraction of the vessels and a quick decrease of the volume follow. 相似文献
72.
Two cases of H.c.c. which occurred in winter 1987 in Vienna are described. Case one was a female Chow-Chow, 8 weeks of age, that died from the peracute form of the disease. The diagnosis was confirmed by histology and direct immunofluorescence. Case two, a 9-month old female Kuvacz, showed clinical signs of the subacute form of H.c.c. She was hospitalized and therapy was successful. The disease was diagnosed by the typical clinical signs and the raise of antibodies in paired serum samples. Etiology, clinical signs and immunology of H.c.c. are discussed. 相似文献
73.
Bilateral nephrolithiasis with intermittent ureterolithiasis was diagnosed in a 7-year old Holstein cow. Two episodes of ureterolithiasis resulted in severe azotemia which resolved after spontaneous movement of the stone. A third episode of obstruction one year after the initial episode resulted in rupture of one kidney, necessitating euthanasia. The histopathological examination of the kidney was diagnostic for chronic pyelonephritis. Corynebacterium sp. was cultured from a nephrolith. In this case it is believed that the chronic pyelonephritis predisposed to the calculi formation. 相似文献
74.
Effect of a new pelleting process on the level of contamination of poultry mash by Escherichia coli and Salmonella 总被引:2,自引:0,他引:2
R H McCapes H E Ekperigin W J Cameron W L Ritchie J Slagter V Stangeland K V Nagaraja 《Avian diseases》1989,33(1):103-111
The efficacy of a new pelleting process in eliminating naturally occurring Escherichia coli and salmonella from poultry mash was assessed by comparing the microbial load in raw and processed mash. Instead of using steam produced in a boiler, the new process conditioned mash in an Original Vertical Conditioner with steam and other hot gases generated by direct combustion in a Vaporator. E. coli was isolated from 72-100% of samples of raw mash in all trials, and the mean number of colony-forming units of E. coli/g of samples was 6.8 +/- 4.0 X 10(4). Salmonellae (S. senftenberg, S. bredeney, and S. mbandaka) were isolated from 5-10% of samples of raw mash utilized in three of the seven trials. Within limitations of the sampling and analytical tests utilized, the new pelleting process eliminated salmonella from all mash in which the organism was known to be present but eliminated E. coli in only three trials. The process appeared to be 100% effective against both organisms when mash entering the pellet mill from the conditioner had a temperature of 85.7 C and a moisture content of 14.5% and had been retained and treated with steam and hot gases for 4.1 minutes. 相似文献
75.
Y Zhou V Moennig C O Coulibaly J Dahle B Liess 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1989,36(1):76-80
Monoclonal antibodies against hog cholera and bovine viral diarrhoea viruses were assayed on organ tissue sections of experimentally infected animals. The animals had been infected simultaneously with both viruses. The antibodies were tested using an indirect immunofluorescence test and an indirect enzyme immunoassay with a biotin/streptavidin/peroxidase detection system. A polyclonal hyperimmune serum was used as a control in direct immunofluorescence tests. Both techniques based on monoclonal antibodies were more sensitive and more specific than the conventional test, the enzyme immunoassay being more sensitive than the immunofluorescence test. Small amounts of BVD viral antigen were demonstrable with monoclonal antibodies in most organ tissues. 相似文献
76.
K Fehlhaber G Krüger V Schubert H Rolletschek 《Archiv fuer experimentelle veterinaermedizin》1989,43(6):855-862
Reference is made to work undertaken by Stehle (1983) on rapid semiquantitative determination of urinary protein in pigs for slaughter to identify premortal strain and stress, with additional studies being conducted into the suitability of the method. The investigations performed for this study covered urinary protein samples from 59 living and 762 slaughtered pigs. The Biophan E paper strip test was applied to groups of animals, and, when compared to high-accuracy laboratory determination of urinary protein, it provided sufficiently accurate information on the presence of stress-related proteinuria. Its accuracy, however, proved to be insufficient, when individual animals were examined. The number of clearly stressed slaughter pigs was unexpectedly high, although the same animals had been rated clinically inconspicuous prior to slaughter. Brief rest period resulted in significant rise of stress. The Biophan E paper strip test was found to be suitable for instantaneous determination of stress and strain on pigs for slaughter. 相似文献
77.
78.
Gastrointestinal nematode infections of goats in a sub-tropical and humid zone of India 总被引:1,自引:0,他引:1
Twelve hundred and twenty-eight goats (Capra hircus L.) from a sub-tropical and humid zone of India were examined for gastrointestinal nematodes. The species encountered in the region were: Haemonchus contortus, Bunostomum trigonocephalum, Oesophagostomum columbianum, Trichuris globulosa, O. aspersum, and T. ovis. The overall infection rate was 86.8%. Among various species found, H. contortus emerged as the most prevalent, although B. trigonocephalum and O. columbianum were also significantly in evidence. The seasonal fluctuation in infection was assessed by monitoring the faecal egg count of 1638 goats slaughtered during the 1-year period. The maximum values for the prevalence and overall mean eggs g-1 of faeces (EPG) were observed after the heavy rainfall season and remained at a relatively high level from July to December. H. contortus and O. columbianum appear to be of major importance as parasites in the goats of this climatic zone; the role of climatic factors in their prevalence is discussed. 相似文献
79.
The kidney's microvascularization of the Pudu pudu is mostly similar to that of domestic animals. The renal parenchymatous arteries do not give off capsular branches. The majority of the Pudu pudu's glomerula shows spherical shape. Glomerula next to the medulla have a diameter which is an average of 25 microns larger than the diameter of those situated more peripherally. Their volume is comparable to that of the angora rabbit. The capillaries form anastomosis in the inner and outer part of the glomerulus. 相似文献
80.