全文获取类型
收费全文 | 86043篇 |
免费 | 5522篇 |
国内免费 | 767篇 |
专业分类
林业 | 3139篇 |
农学 | 2533篇 |
基础科学 | 673篇 |
9788篇 | |
综合类 | 16382篇 |
农作物 | 3020篇 |
水产渔业 | 3754篇 |
畜牧兽医 | 46983篇 |
园艺 | 1122篇 |
植物保护 | 4938篇 |
出版年
2021年 | 718篇 |
2020年 | 934篇 |
2019年 | 979篇 |
2018年 | 1440篇 |
2017年 | 1655篇 |
2016年 | 1446篇 |
2015年 | 1437篇 |
2014年 | 1682篇 |
2013年 | 3097篇 |
2012年 | 3010篇 |
2011年 | 3636篇 |
2010年 | 2416篇 |
2009年 | 2362篇 |
2008年 | 3197篇 |
2007年 | 3033篇 |
2006年 | 2735篇 |
2005年 | 2646篇 |
2004年 | 2417篇 |
2003年 | 2473篇 |
2002年 | 2347篇 |
2001年 | 2609篇 |
2000年 | 2629篇 |
1999年 | 2026篇 |
1998年 | 919篇 |
1997年 | 858篇 |
1996年 | 778篇 |
1995年 | 872篇 |
1994年 | 785篇 |
1993年 | 795篇 |
1992年 | 1658篇 |
1991年 | 1837篇 |
1990年 | 1794篇 |
1989年 | 1691篇 |
1988年 | 1558篇 |
1987年 | 1642篇 |
1986年 | 1625篇 |
1985年 | 1463篇 |
1984年 | 1256篇 |
1983年 | 1080篇 |
1982年 | 714篇 |
1979年 | 1057篇 |
1978年 | 832篇 |
1976年 | 715篇 |
1975年 | 750篇 |
1974年 | 1006篇 |
1973年 | 986篇 |
1972年 | 956篇 |
1971年 | 882篇 |
1970年 | 855篇 |
1969年 | 805篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
The insecticide formulation BI 58 EC was tested for teratogenicity in chicken embryos, with particular reference to degradation of the active ingredient (dimethoate) after the treatment of embryonated eggs. The pesticide was diluted in water to a concentration level of 0.8%, and the emulsion was injected into the air space in a volume of 0.1 ml/egg, or hen's eggs were treated by the immersion technique. Residues of dimethoate were measured in the samples on days, 13, 15 and 19 of the incubation of chicken embryos, and morphological examinations were performed simultaneously. Analytical chemistry data indicated a slower degradation of dimethoate in embryos after the immersion of eggs, and cyllosis was remarkable in this group among the sporadic developmental anomalies. The liver tissues of both treated groups exhibited severe fatty infiltration. 相似文献
105.
106.
107.
L Seganti F Superti L Sinibaldi M Marchetti S Bianchi N Orsi 《Comparative immunology, microbiology and infectious diseases》1991,14(3):265-275
Rabies virus is able to infect in vitro a wide range of homeothermic and poikilothermic cells but little is known about its multiplication in arthropod cells. In this research the infection of rabies virus in Aedes pseudoscutellaris cells, a mosquito cell line susceptible to mosquito-borne viruses, was studied. After 60 days of incubation at 26 degrees C up to 70% of infected cells showed the synthesis of both viral nucleocapsid and envelope antigens, although viral yield and cell damage could not be detected. Research performed in order to investigate the role of membrane carbohydrate moieties in rabies virus-mosquito cell interaction suggested the participation of galactose and N-acetylglucosamine whereas sialic acid, known to be a rabies binding site in many homeothermic cell lines, was not involved. 相似文献
108.
P. Merino J.M. Estavillo L.A. Graciolli M. Pinto M. Lacuesta A. Muñoz-Rueda C. Gonzalez-Murua 《Soil Use and Management》2002,18(2):135-141
Abstract. Nitrous oxide (N2 O) is involved in both ozone destruction and global warming. In agricultural soils it is produced by nitrification and denitrification mainly after fertilization. Nitrification inhibitors have been proposed as one of the management tools for the reduction of the potential hazards of fertilizer-derived N2 O. Addition of nitrification inhibitors to fertilizers maintains soil N in ammonium form, thereby gaseous N losses by nitrification and denitrification are less likely to occur and there is increased N utilization by the sward. We present a study aimed to evaluate the effectiveness of the nitrification inhibitor dicyandiamide (DCD) and of the slurry additive Actilith F2 on N2 O emissions following application of calcium ammonium nitrate or cattle slurry to a mixed clover/ryegrass sward in the Basque Country. The results indicate that large differences in N2 O emission occur depending on fertilizer type and the presence or absence of a nitrification inhibitor. There is considerable scope for immediate reduction of emissions by applying DCD with calcium ammonium nitrate or cattle slurry. DCD, applied at 25 kg ha–1 , reduced the amount of N lost as N2 O by 60% and 42% when applied with cattle slurry and calcium ammonium nitrate, respectively. Actilith F2 did not reduce N2 O emissions and it produced a long lasting mineralization of previously immobilized added N. 相似文献
109.
110.
Sarah L Ralston 《Veterinary Clinics of North America: Equine Practice》2002,18(2):295-304, vii
Abnormally high or low blood glucose and insulin concentrations after standardized glucose tolerance tests can reflect disorders such as pituitary dysfunction, polysaccharide storage myopathies, and other clinical disorders. Glucose and insulin responses, however, are modified by the diet to which the animal has adapted, time since it was last fed, and what it was fed. Body fat (obesity), fitness level, physiologic status, and stress also alter glucose and insulin metabolism. Therefore, it is important to consider these factors when evaluating glucose and insulin tests, especially if only one sample it taken. This article describes the factors affecting glucose and insulin metabolism in horses and how they might influence the interpretation of standardized tests of glucose tolerance. 相似文献