全文获取类型
收费全文 | 166278篇 |
免费 | 9450篇 |
国内免费 | 100篇 |
专业分类
林业 | 6706篇 |
农学 | 5650篇 |
基础科学 | 1036篇 |
21296篇 | |
综合类 | 24809篇 |
农作物 | 6103篇 |
水产渔业 | 8751篇 |
畜牧兽医 | 88377篇 |
园艺 | 2208篇 |
植物保护 | 10892篇 |
出版年
2020年 | 1363篇 |
2019年 | 1641篇 |
2018年 | 2645篇 |
2017年 | 2897篇 |
2016年 | 2711篇 |
2015年 | 2325篇 |
2014年 | 2863篇 |
2013年 | 6787篇 |
2012年 | 5073篇 |
2011年 | 6094篇 |
2010年 | 4169篇 |
2009年 | 4164篇 |
2008年 | 6046篇 |
2007年 | 5857篇 |
2006年 | 5445篇 |
2005年 | 5019篇 |
2004年 | 4886篇 |
2003年 | 4955篇 |
2002年 | 4507篇 |
2001年 | 5803篇 |
2000年 | 5717篇 |
1999年 | 4565篇 |
1998年 | 1827篇 |
1997年 | 1773篇 |
1996年 | 1643篇 |
1995年 | 1982篇 |
1994年 | 1659篇 |
1993年 | 1668篇 |
1992年 | 3466篇 |
1991年 | 3616篇 |
1990年 | 3606篇 |
1989年 | 3577篇 |
1988年 | 3268篇 |
1987年 | 3295篇 |
1986年 | 3230篇 |
1985年 | 3047篇 |
1984年 | 2502篇 |
1983年 | 2188篇 |
1982年 | 1462篇 |
1979年 | 2092篇 |
1978年 | 1666篇 |
1977年 | 1463篇 |
1976年 | 1403篇 |
1975年 | 1497篇 |
1974年 | 1756篇 |
1973年 | 1821篇 |
1972年 | 1795篇 |
1971年 | 1552篇 |
1970年 | 1581篇 |
1969年 | 1507篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
101.
Seven cases of cutaneous hemangioma and nine of cutaneous hemangiosarcoma were diagnosed from biopsy specimens of 15 Domestic Shorthairs of 5,091 cats that were examined by necropsy or biopsy during the 5-year period from 1 January 1986 through 31 December 1990. All but three cats were male. Tumor cells of both hemangiomas and hemangiosarcomas were immunoreactive for factor VIII-related antigen and for vimentin by the avidin biotin peroxidase complex method. In cats with a median age of 10 years, hemangiomas occurred in skin with pigmented hair in six of seven cases without apparent site predilection. These solitary tumors did not recur after excision although one cat (No. 3) subsequently developed cutaneous hemangiosarcoma at another site. Seven of nine hemangiosarcomas occurred in dermis and subcutis of the head, usually on the pinna. All five hemangiosarcomas of the head, for which cutaneous pigmentation could be determined, occurred in unpigmented skin. Cats with hemangiosarcoma had a median age of 12.5 years at the time of diagnosis. Metastasis has not been documented, but hemangiosarcoma has recurred, from 1 month to 2 years after excision, in 6/7 cats that were studied. 相似文献
102.
J Kimura A Tsukise M Okano 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(5):1035-1037
The dependency of the secretory function of the feline major vestibular gland (Bartholin's gland) on the ovarian steroid hormones was studied histochemically. After estrogen (estradiol-17 beta or diethylstilbestrol), progesterone or a combination of these was administered to cats which were previously ovariohysterectomized, the major vestibular glands were removed, embedded in paraffin, sectioned, and stained by alcian blue, periodic acid-Schiff or peroxidase-labeled lectin (peanut agglutinin and wheat germ agglutinin). The vividly positive reactions to the stainings applied were observed in the secretory epithelial cells of the major vestibular glands in the estrogen treated animals. The dependency of the secretory function of the major vestibular glands on the estrogen was demonstrated in this study. 相似文献
103.
S Agungpriyono Y Yamamoto N Kitamura J Yamada K Sigit T Yamashita 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(6):1063-1069
The stomach of the lesser mouse deer (Tragulus javanicus) was observed macroscopically. It consisted of only three compartments, rumen, reticulum and abomasum without omasum. The rumen was S-shaped with large ventral and caudoventral blind sacs and the reticulum was larger than the abomasum. Internally, the rumen was covered with numerous ruminal papillae even on the pillars and the ruminoreticular fold. These papillae were leaf- or tongue-like shaped and varied in size and density. The reticulum had honey-combed crests and the secondary crests were found rarely. The lips of the reticular groove were prominent and more developed in the aboral part than in the oral one. A sac-like transition zone, which had more prominent mucosal folds than had the floor of the reticular groove, was observed between the caudal end of the reticular groove and the abomasum. Mucosal folds of the abomasum were spiral, low but rather thick. These findings were discussed in view of comparison with other ruminants and of possible functional implications. 相似文献
104.
105.
106.
David E Kenny Michael R Lappin Felicia Knightly Jeffery Baler Melissa Brewer David M Getzy 《Journal of zoo and wildlife medicine》2002,33(2):131-138
In May 1996 the Denver Zoological Gardens obtained two male and two female Pallas' cats (Otocolobus felis manul) that were wild-caught in the Ukraine. These animals were part of a group of 16 wild-caught adults (eight male and eight female) imported to the United States and Canada between 1995 and 1996. The Denver Zoological Gardens cats were quarantined at the zoo hospital for approximately I mo. During the quarantine period they were immobilized for physical examination, and sera were obtained from them to evaluate for exposure to Toxoplasma gondii. All cats were positive for T. gondii antibodies by latex agglutination (titers from 1:512 to 1:1,024). After being paired for breeding, one pair produced two litters, and another pair produced four litters, a total of 17 kittens between 1997 and 2001. Four kittens and two young adults died from a disseminated granulomatous and necrotizing inflammation consistent with toxoplasmosis. Toxoplasma gondii infection was confirmed in all six deceased cats by polymerase chain reaction performed on formalin-fixed tissues. An additional five kittens disappeared and were not available for necropsy. The fatality rate from toxoplasmosis was 35.3% (6/17) for cats that were available for necropsy and could have been as high as 64.7% (11/17) if it were assumed that the disappeared kittens were also affected. The Pallas' kitten survival rate at the Denver Zoological Gardens was 35.3%. This article describes the clinical and pathologic features of toxoplasmosis in a group of Pallas' cats at the Denver Zoological Gardens. 相似文献
107.
A field experiment was conducted with different nitrogen regimes to assess the growth and yield performance of wheat genotypes which differ in nitrate assimilation potential. Genotypic differences in biomass accumulation were observed at different growth stages. The nitrogen treatment had little effect on biomass accumulation at early stages of growth, while at later stages of growth there was enhanced biomass accumulation when N was applied in more than two splits. On an average, genotypes with high nitrate reductase activity (the 'HNR' genotypes) accumulated 14.2 % more biomass than the genotypes with low nitrate reductase activity ('LNR' genotypes) when an extra dose (40 kg N ha−1 ) of nitrogen was given at the time of anthesis. The application of nitrogen in more than two splits increased grain yield of both 'HNR' and 'LNR' genotypes mainly by increasing grain weight per ear. The application of an extra dose of nitrogen (40 kg N ha−1 ) at the time of anthesis increased grain yield of 'HNR' genotypes by 38.5 % as compared to 'LNR' genotypes. 相似文献
108.
109.
110.
P I Rekwot E O Oyedipe O O Akerejola A A Voh P M Dawuda 《The British veterinary journal》1989,145(1):85-88
Twenty-one Bunaji (White Fulani, Zebu) and 21 Friesian X Bunaji cross-bred bull calves, approximately 6 months of age, were each divided after weaning into two groups and fed isocaloric rations containing 14.45% (high protein) and 8.51% (low protein) crude protein for 10 months. Serum samples were collected biweekly for 10 months and analysed for serum proteins. Age had no significant effect. The Bunaji had significantly (P less than 0.05) higher total protein, albumin, and alpha 1-globulin than Friesian X Bunaji. While there was no significant difference in body condition score between the two breeds, the Friesian X Bunaji had a significantly (P less than 0.05) higher growth rate. Animals on high protein diets had significantly (P less than 0.05) higher total protein, albumin, alpha 2-globulin, gamma-globulin and total globulin than those on low protein. However, alpha 1-globulin and beta-globulin were not significantly (P greater than 0.05) different for the two treatment groups. 相似文献