全文获取类型
收费全文 | 321807篇 |
免费 | 18368篇 |
国内免费 | 9745篇 |
专业分类
林业 | 31951篇 |
农学 | 25809篇 |
基础科学 | 9957篇 |
53877篇 | |
综合类 | 50859篇 |
农作物 | 21407篇 |
水产渔业 | 18718篇 |
畜牧兽医 | 99625篇 |
园艺 | 9492篇 |
植物保护 | 28225篇 |
出版年
2022年 | 3472篇 |
2021年 | 5626篇 |
2020年 | 5600篇 |
2019年 | 6366篇 |
2018年 | 5597篇 |
2017年 | 6921篇 |
2016年 | 7199篇 |
2015年 | 7981篇 |
2014年 | 9196篇 |
2013年 | 20411篇 |
2012年 | 10904篇 |
2011年 | 12888篇 |
2010年 | 12709篇 |
2009年 | 12849篇 |
2008年 | 11386篇 |
2007年 | 10568篇 |
2006年 | 11110篇 |
2005年 | 9825篇 |
2004年 | 7518篇 |
2003年 | 7219篇 |
2002年 | 6414篇 |
2001年 | 6599篇 |
2000年 | 6370篇 |
1999年 | 6471篇 |
1998年 | 5680篇 |
1997年 | 5556篇 |
1996年 | 5191篇 |
1995年 | 5569篇 |
1994年 | 4817篇 |
1993年 | 4572篇 |
1992年 | 4843篇 |
1991年 | 4846篇 |
1990年 | 4503篇 |
1989年 | 4418篇 |
1988年 | 3866篇 |
1987年 | 3743篇 |
1986年 | 3529篇 |
1985年 | 3854篇 |
1984年 | 3592篇 |
1983年 | 3402篇 |
1982年 | 2890篇 |
1981年 | 2832篇 |
1980年 | 2763篇 |
1979年 | 3148篇 |
1978年 | 2826篇 |
1977年 | 2639篇 |
1976年 | 2495篇 |
1974年 | 2598篇 |
1973年 | 2496篇 |
1972年 | 2364篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
选用14日龄健康的海佩科内用仔鸡48羽,随机分成试验(24羽)和对照(24羽)两组.试验组在饲粮中添加0.25%的茶多酚(TP),研究TP对鸡免疫功能的作用.试验结果表明,TP对自然感染法氏囊病鸡,有明显提高(p<0.05)鸡血液中红细胞C_(3b)受体和免疫复合物的含量及保护鸡脾脏正常的免疫功能,同时也发现TP对公母鸡法氏囊的重量有不同影响.本试验表明,TP具有提高家禽免疫功能的作用. 相似文献
103.
A disease causing the decline of papaya (Carica papaya) plants was noticed in the Jordan Valley in 1982. The disease caused severe yellowing of the upper leaves and dieback of the apex. The disease was not transmissible mechanically and continued efforts to associate viruses and viroids have so far been unsuccessful. Epidemiological observations suggested that the disease is airborne and probably caused by a mollicute. In order to test this hypothesis, plots were covered by an insect-proof net and with white nets providing 15, 30 and 50% shade. The 30%, 50% and insect-proof nettings provided complete protection, and the 15% netting reduced disease incidence to <2%, compared with>37% in the uncovered control plot. Spraying plants at weekly intervals with a commercial whitewash solution was also found to be effective in reducing disease incidence. The advantages of using a range of netting field treatments as a simple means for obtaining information on the epidemiological nature of a new disease are described. 相似文献
104.
P. Buracco R. Guglielmino O. Abate V. Bocchini E. Cornaglia D. B. DeNicola† M. Cilli P. Ponzio 《The Journal of small animal practice》1992,33(6):279-284
The clinical course of a feline leukaemia virus (FeLV)-negative and feline immunodeficiency virus (FIV)-positive cat affected with a large granular lymphocyte lymphoma is presented. Cyto-logical examination showed neoplastic cells in the pleural effusion and in two abdominal masses. Bone marrow and peripheral blood were moderately involved and chemotherapy was used to control the tumour. Cytochemistry, immunohis-tochemistry and ultrastructural studies were applied to define the cellular lineage; cytochemistry suggested a T-cell lineage. 相似文献
105.
B Mermer P Hillman R Harris T Krogmann Q Tonelli W Palin P Andersen 《Veterinary immunology and immunopathology》1992,35(1-2):133-141
We have developed an antibody detection enzyme-linked immunosorbent assay (ELISA) for the identification of animals infected by feline immunodeficiency virus (FIV). The ELISA solid-phase antigen consists of recombinant FIV gag proteins expressed in bacteria. The proteins are purified from bacterial lysates as insoluble inclusion bodies. In the case of bacterially expressed p24gag, it is shown that all of the linear, sequential epitopes presented by viral p24 during infection are retained. Purified preparations can be substituted for solid-phase whole virus in the IDEXX PetChektm immunoassay. The antibody ELISA duplicates the sensitivity and specificity of the whole virus based PetChek plate assay. 相似文献
106.
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
107.
The immunofunctional response of the gland of Harder (GH) was compared in chickens and turkeys using an in vivo assay previously developed for use in chickens. The GH were surgically removed (GHx) from leghorn chicks at 1 day of age and from poults at 2 days of age. Intact birds of each species served as controls. During the fourth week of age, both GH-intact and GHx chicks were exposed to killed Brucella abortus antigen by the ocular or intraperitoneal route. One week later, serum and tears were collected and assayed for antibodies to B. abortus. In addition, all birds were killed at the end of the trial period, and the heads were fixed and processed for histologic examination. Various components of the head-associated lymphoid tissue (HALT) including the GH, nasal glands, lacrimal glands, lacrimal ducts, eyelid conjunctiva, and nasal cavity mucosa/submucosa, were evaluated microscopically using a scoring system to estimate quantity and degree of development of immune tissue in those sites. Results of all analyses indicate that functional response and morphology of the HALT are comparable in turkeys and chickens. 相似文献
108.
家用冰箱存在着不同程度的细菌污染,必需对冰箱进行定期或不定期的消毒。经用载体法和平皿法研究发现,用紫外线对冰箱进行消毒是可行的,其对大肠杆菌、金黄色葡萄球菌和枯草杆菌黑色变种芽胞有较强的杀灭作用,而且不会引起冰箱内温度升高。同时还可产生少量Q,除去冰箱内异味,因此具有杀菌、抑菌、除臭保鲜的作用。 相似文献
109.
Abstract. The use of an indirect enzyme-linked immunosorbent assay ( elisa ) for the detection of channel catfish antibody to Edwardsiella ictaluri is described. Changes in agglutination titre in fish immunized with Edwardsiella ictaluri heat killed whole bacterins or lipopolysaccharides were reflected by corresponding changes in elisa readings. Relatively high correlations were observed among elisa OD readings, computed elisa titres and corresponding agglutination titres. 相似文献
110.