全文获取类型
收费全文 | 119630篇 |
免费 | 6377篇 |
国内免费 | 124篇 |
专业分类
林业 | 5460篇 |
农学 | 3325篇 |
基础科学 | 643篇 |
13297篇 | |
综合类 | 23741篇 |
农作物 | 4658篇 |
水产渔业 | 5355篇 |
畜牧兽医 | 61340篇 |
园艺 | 1314篇 |
植物保护 | 6998篇 |
出版年
2018年 | 1644篇 |
2017年 | 1811篇 |
2016年 | 1597篇 |
2015年 | 1403篇 |
2014年 | 1786篇 |
2013年 | 4060篇 |
2012年 | 3250篇 |
2011年 | 3893篇 |
2010年 | 2483篇 |
2009年 | 2636篇 |
2008年 | 3823篇 |
2007年 | 3671篇 |
2006年 | 3496篇 |
2005年 | 3259篇 |
2004年 | 3140篇 |
2003年 | 3184篇 |
2002年 | 2957篇 |
2001年 | 3565篇 |
2000年 | 3554篇 |
1999年 | 2794篇 |
1998年 | 1097篇 |
1997年 | 1089篇 |
1996年 | 1098篇 |
1995年 | 1241篇 |
1994年 | 1084篇 |
1993年 | 1148篇 |
1992年 | 2261篇 |
1991年 | 2485篇 |
1990年 | 2349篇 |
1989年 | 2362篇 |
1988年 | 2164篇 |
1987年 | 2243篇 |
1986年 | 2299篇 |
1985年 | 2262篇 |
1984年 | 1758篇 |
1983年 | 1576篇 |
1982年 | 1072篇 |
1979年 | 1674篇 |
1978年 | 1361篇 |
1977年 | 1145篇 |
1975年 | 1192篇 |
1974年 | 1591篇 |
1973年 | 1516篇 |
1972年 | 1589篇 |
1971年 | 1532篇 |
1970年 | 1461篇 |
1969年 | 1401篇 |
1968年 | 1172篇 |
1967年 | 1224篇 |
1966年 | 1082篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
E. Conde A. M. Moreno I. Martin-Lacave A. Fernandez y H. Galera 《Anatomia, histologia, embryologia》1992,21(1):94-100
A systematic immunohistochemical study of the ultimobranchial tubule (UBT) has been carried out in 45 Wistar rats of different ages (0, 5, 10, 15, 20, 25, 30, 60 and 120 days). The existence of calcitonin immunoreactive cells in the UBT wall has been demonstrated in a 5-days old rat. In addition, immunohistochemical studies for thyroglobulin revealed positive staining in follicular cells connected to the UBT and, occasionally, in isolated cells lying within solid clusters from the UBT. These last results together with the continued and repeated existence of numerous mitosis and PAS (+) microfollicles, apparently rising from the UBT, support the hypothesis that the ultimobranchial body (UBB) may contribute partially to the formation of a part of the follicular component. 相似文献
2.
Kevin R. Stuart Arnold G. Eversole David E. Brune 《Journal of the World Aquaculture Society》2001,32(1):105-111
Abstract.— The freshwater mussel Elliptio complanata was provided water containing green algae and cyanobacteria delivered from the Partitioned Aquaculture System (PAS) at eight flow rates to determine algal filtration rates as mg of particulate organic carbon (POC)/kg wet tissue weight per h. The dominant taxon in cyanobacterial waters was Microcystis while the dominant taxa in green algal waters were Scenedesmus and Ankistrodesmus . The cell counts of Scenedesmus and Ankistrodesmus were the only algal taxa that were significantly different between the incoming water and water filtered by mussels. Filtration rates of POC obtained from green algal water were significantly greater than from cyanobacteria-dominated waters at all flow rates. A significant increase in mean filtration rate was observed as flow rates increased. The filtration rate of green algae increased as POC concentration increased, peaking at 28 mg C/L. A maximum filtration rate was not observed with cyanobacterial waters. 相似文献
3.
E Oohashi K Yagi Y Uzuka S Tanabe T Sarashina T Ishida 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(11):1241-1243
The purpose of this study was to evaluate seasonal influences on thyroid hormone levels of healthy outdoor dogs in Hokkaido. We surveyed serum basal total thyroxine (tT4), free thyroxine (fT4), and canine thyroid-stimulating hormone (cTSH) levels, and tT4 levels after administration of TSH for a year. Basal tT4 levels decreased in January, and increased in August and September. fT4 levels increased in January and November. No significant seasonal variation was found in cTSH. tT4 levels after administration of TSH in August and November increased. These results suggested that the thyroid gland may have been activated in November. We should take seasonal variation into consideration when thyroid function is tested. 相似文献
4.
The isolation of (+)-totarol as active compound against Mycobacterium tuberculosis is reported from Chamaecyparis nootkatensis outerbark. 相似文献
5.
6.
7.
8.
C Richardson W P Taylor S Terlecki E P Gibbs 《American journal of veterinary research》1985,46(9):1912-1922
Twenty-four ewes were inoculated with 1 of 2 strains of bluetongue virus type 4 at 40, 60, or 80 days of gestation. Two ewes aborted, 2 ewes died, and 1 was killed during the experiment, but their fetuses were recovered. At term, 2 mummified fetuses, 4 dead lambs, and 17 clinically healthy lambs were produced by 12 sheep, and the remaining 7 sheep were barren. Porencephaly and cerebellar dysgenesis were found in term lambs born to sheep inoculated at 40 and 60 days of gestation. Radiographic examination of 12 fetuses showed developmental ages far less than their chronologic age; 8 fetuses had skeletal growth-retardation lines, which were also observed in the dead lambs. A systemic lymphoreticular hyperplasia was observed in the dead lambs and in all lambs at 12 weeks of age; in 4 of the latter, granulomatous reactions were present in the liver and kidney. Lungs of the full-term lambs were reduced in weight and showed poor alveolar development and mononuclear cell infiltration, which persisted in the 12-week-old lambs. It was concluded that bluetongue virus is capable of causing not only gross abnormalities of the CNS, but also generalized growth retardation and fetal lymphoreticular hyperplasia. 相似文献
9.
Disseminated Aspergillus terreus infection was diagnosed in ten previously healthy adult dogs--nine German shepherds and one dalmatian. The disease was characterized by the presence of multiple granulomas and infarcts in a wide range of organs. The kidney, spleen, and skeletal system were most commonly and severely affected. Fungal hyphae were demonstrated in large numbers within granulomas and thrombi, and A. terreus was readily isolated by culture. This disseminated mycosis appears unique; in this series of cases there was no apparent predisposing factor, portal of entry, or primary focus for dissemination of the infection. 相似文献
10.