全文获取类型
收费全文 | 125839篇 |
免费 | 6646篇 |
国内免费 | 70篇 |
专业分类
林业 | 6836篇 |
农学 | 4764篇 |
基础科学 | 834篇 |
16841篇 | |
综合类 | 17767篇 |
农作物 | 4872篇 |
水产渔业 | 6583篇 |
畜牧兽医 | 63829篇 |
园艺 | 2092篇 |
植物保护 | 8137篇 |
出版年
2018年 | 2765篇 |
2017年 | 2923篇 |
2016年 | 2254篇 |
2015年 | 1627篇 |
2014年 | 1934篇 |
2013年 | 4538篇 |
2012年 | 3762篇 |
2011年 | 5111篇 |
2010年 | 3810篇 |
2009年 | 3615篇 |
2008年 | 4823篇 |
2007年 | 4859篇 |
2006年 | 3844篇 |
2005年 | 3613篇 |
2004年 | 3550篇 |
2003年 | 3539篇 |
2002年 | 3287篇 |
2001年 | 4230篇 |
2000年 | 4098篇 |
1999年 | 3314篇 |
1998年 | 1448篇 |
1997年 | 1323篇 |
1996年 | 1244篇 |
1995年 | 1369篇 |
1994年 | 1301篇 |
1993年 | 1236篇 |
1992年 | 2579篇 |
1991年 | 2690篇 |
1990年 | 2866篇 |
1989年 | 2633篇 |
1988年 | 2479篇 |
1987年 | 2374篇 |
1986年 | 2347篇 |
1985年 | 2238篇 |
1984年 | 1882篇 |
1983年 | 1644篇 |
1982年 | 1069篇 |
1979年 | 1671篇 |
1978年 | 1307篇 |
1977年 | 1138篇 |
1976年 | 1121篇 |
1975年 | 1146篇 |
1974年 | 1304篇 |
1973年 | 1346篇 |
1972年 | 1349篇 |
1971年 | 1267篇 |
1970年 | 1241篇 |
1969年 | 1201篇 |
1967年 | 1092篇 |
1966年 | 1033篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Effect of injecting amino acids into the egg on embryonic and subsequent growth in the domestic fowl
W. K. Al‐Murrani 《British poultry science》1982,23(2):171-174
1. The growing embryo uses about 1% of the total protein available in the egg during the first week of incubation.
2. Injecting the growing embryo with amino acids equivalent to the amount of protein used resulted in higher weight of chicks at all stages up to 56 d. 相似文献
992.
Insulin-secreting islet cell tumors: establishing a diagnosis and the clinical course for 25 dogs 总被引:2,自引:0,他引:2
S A Kruth E C Feldman P C Kennedy 《Journal of the American Veterinary Medical Association》1982,181(1):54-58
Twenty-five dogs with insulin-secreting neoplasms of the pancreas were studied. The diagnosis in each case was determined by histologic evaluation of pancreatic tissue obtained at surgery. The breed distribution revealed that German Shepherd Dogs, Irish Setters, and Collies were most commonly represented. Physical examination, complete blood counts, serum biochemical analysis, and urinalysis were of little diagnostic value, aside from the finding of hypoglycemia in 21 of 25 dogs. Radiographs of the thorax and abdomen were noncontributory to the ultimate diagnosis. Prior to surgery, fasting immunoreactive insulin concentrations and blood glucose concentrations were studied. Insulin:glucose ratios, glucose:insulin ratios, and amended insulin:glucose ratios were determined from the insulin and glucose concentrations in a single blood sample in each of 28 trials. In addition, glucagon tolerance tests were performed on 12 dogs. The amended insulin:glucose ratios proved to be the most reliable for diagnosis. Pancreatic masses were evident at surgery in 23 of 25 dogs; the remaining 2 dogs had microscopic evidence of an islet cell tumor. Nineteen of the islet cell tumors were carcinomas and 6 were simply described as "islet cell tumors." The mean life expectancy after surgery was 12.3 months. Treatment for malignant islet cell tumours included frequent feeding glucocorticoids, and diazoxide. 相似文献
993.
Subsequent to a cross-sectional serological survey of Manawatu dairy farm workers, a case-control study was carried out to investigate the correlation between titres to leptospiral serovars in workers and those in cattle in their herds. A total of 52 herds was investigated, 25 of which were high risk where milkers had titres of 1:96 or greater, and 27 were case-controls where milkers had no detectable agglutinin titres at a minimum serum dilution of 1:24. The serological prevalence of titres to hardjo in cattle on high risk farms (76.5%) was significantly higher (P<0.05) than on the case-control farms (60.0%). The geometric mean titres of seropositive cattle on high risk farms were also significantly higher (P<0.01) than in the cattle from the case-control farms, especially in the younger cohorts. These findings suggest that there was active endemic hardjo infection in the two- to three-year-old cattle on the high risk farms. Titres to pomona were demonstrated in only 5.2% of the cattle from both types of farm. Workers with titres to pomona tended to be from farms on which stock, especially calves, were bought-in and pigs were kept. Conventional measures for protecting milkers from contact with infected urine appeared to be ineffective and it is concluded that prevention of leptospirosis in dairy farm workers can only be achieved by elimination of infection in the herd by vaccination of cattle. 相似文献
994.
G. Vulsteke P. Meeus 《European journal of plant pathology / European Foundation for Plant Pathology》1982,88(2):79-85
Two sprays of vinclozolin (0.5 kg a.i. ha–1) or procymidone (0.5 kg a.i. ha–1), the first at the beginning of flowering and the second two weeks later, gave the best control ofBotrytis cinerea on dwarf snap beans (Phaseolus vulgaris). Good results were also obtained with iprodione and with thiophanate-methyl. Vinclozolin and procymidone at the same program were the most active fungicides againstSclerotinia sclerotiorum. Treatments with the latter two fungicides resulted in increased yields of pods and had no influence on colour and quality of the pods. Residue levels were below the tolerances.Samenvatting Twee bespuitingen met vinchlozolin (0,5 kg a.i. ha–1) of procymidon (0,5 kg a.i. ha–1), de eerste in het stadium begin bloei en de tweede 14 dagen later tijdens de peulzetting, waren voldoende omB. cinerea in stamslabonen te bestrijden. Tevens werden goede resultaten verkregen met iprodion en thiofanaat-methyl. Vinchlozolin en procymidon gaven volgens hetzelfde schema toegepast ook de beste werking tegenS. sclerotiorum. Toepassingen van deze laatste twee fungiciden leverden een hogere peulopbrengst en hadden geen invloed op de kleur en de kwaliteit van de peulen. Het residugehalte in de peulen lag beneden de toelaatbare grens.This research was subsidized by the Instituut tot Aanmoediging van het Wetenschappelijk Onderzoek in Nijverheid en Landbouw (IWONL). 相似文献
995.
996.
997.
998.
999.
Mesce KA 《Science (New York, N.Y.)》1982,215(4535):993-995
Hermit crabs explore empty gastropod shells by touching, rolling, and probing them before choosing one for a home. This component of shell selection behavior was examined in Pagurus hirsutiusculus hirsutiusculus (Dana) with binary choice tests between natural shells and accurate replicas of the shells with different chemical compositions. The results show that calcium emanating from the surface of shells is responsible for the behavior. Sensitivity to calcium may be a factor that enables the hermit crab to locate partially buried shells and discriminate empty shells from ones housing living gastropods or from small pebbles. 相似文献
1000.
Abelson PH 《Science (New York, N.Y.)》1982,216(4551):1177