全文获取类型
收费全文 | 11447篇 |
免费 | 779篇 |
专业分类
林业 | 964篇 |
农学 | 418篇 |
基础科学 | 55篇 |
2364篇 | |
综合类 | 389篇 |
农作物 | 431篇 |
水产渔业 | 1020篇 |
畜牧兽医 | 5314篇 |
园艺 | 174篇 |
植物保护 | 1097篇 |
出版年
2023年 | 80篇 |
2022年 | 113篇 |
2021年 | 248篇 |
2020年 | 230篇 |
2019年 | 157篇 |
2018年 | 473篇 |
2017年 | 506篇 |
2016年 | 500篇 |
2015年 | 374篇 |
2014年 | 458篇 |
2013年 | 653篇 |
2012年 | 789篇 |
2011年 | 685篇 |
2010年 | 383篇 |
2009年 | 356篇 |
2008年 | 563篇 |
2007年 | 516篇 |
2006年 | 425篇 |
2005年 | 458篇 |
2004年 | 376篇 |
2003年 | 368篇 |
2002年 | 309篇 |
2001年 | 264篇 |
2000年 | 254篇 |
1999年 | 225篇 |
1998年 | 48篇 |
1997年 | 42篇 |
1996年 | 49篇 |
1992年 | 137篇 |
1991年 | 124篇 |
1990年 | 114篇 |
1989年 | 131篇 |
1988年 | 126篇 |
1987年 | 124篇 |
1986年 | 116篇 |
1985年 | 104篇 |
1984年 | 81篇 |
1983年 | 74篇 |
1982年 | 46篇 |
1981年 | 58篇 |
1980年 | 50篇 |
1979年 | 105篇 |
1978年 | 95篇 |
1977年 | 84篇 |
1976年 | 55篇 |
1975年 | 48篇 |
1974年 | 99篇 |
1973年 | 70篇 |
1972年 | 96篇 |
1971年 | 92篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
The effect of seven fertilizers on the viability of Taenia saginata eggs was tested in vitro. The most destructive effect was produced by lime-nitrogen, in which the eggs survived only for 24 hours in the substance and for two days in a saturated solution. In the limestone the eggs survived for three days. 相似文献
32.
V Danielová D Málková J Minár B Rehse-Küpper Z Hájková J Halgos L Jedlicka 《Folia parasitologica》1978,25(2):187-190
In the years 1973 and 1975 mosquitoes and some other Diptera (Tabanidae, Simuliidae, Hippoboscidae) were tested for virus. 13,924 mosquitoes, 75 horseflies and 60 blackflies were processed in 1973. Five strains of Tahyna virus were isolated from mosquito species Aedes vexans. 3,378 mosquitoes and 12 sheep keds were tested for virus in 1975. Twelve strains of Calovo virus were isolated from Anopheles maculipennis and one strain of Tahyna virus was obtained from Aedes vexans mosquitoes. 相似文献
33.
Surface structures of males and females of Setaria labiatopapillosa were studied by means of scanning electron microscopy at high magnification. It was found that the surface of buccal cavity, lateral appendages, vulva, anus and cloaca differs from the remaining cuticle. The shape of internal and external mouth papillae, amphids, deirids, postdeirid and phasmidial pore was studied. On the surface of the postdeirid are four small papillae arranged in a typical manner around the depression from which projects a needle-like formation. The ventral bands are formed by fine longitudinal parallel folds of the cuticle. Some anomalies in the localization of postcloacal papillae were observed. 相似文献
34.
Bacillary rickettsia-like organisms (BRLO) were found in the tick Dermacentor marginatus. They are gram-negative and differ from common bacteria and reckettsiae both in the cultivation conditions and morphology. BRLO are non-pathogenic for ticks and guinea pigs. In our studies they were isolated on half-engorged females of D. marginatus, on which they are still maintained. 相似文献
35.
A very low virus level was found for a short time in the blood of ducklings and goslings after experimental Lednice (Yaba 1) virus infection by subcutaneous (scut) and intranasal (inas) route and in blood of ducklings also after infection by intracerebral (icer) route. Subsequently virus neutralizing antibody formation was examined. Antibody formation was found in most of animals. In goslings onset of antibody formation seems to be slower than in ducklings after the same virus infection dose; vice versa, in ducklings antibody titer decreased after 6 weeks. Using low infection virus dose, neutralizing antibody level in ducklings was lower than in the former case. On examining the blood and the organs, the virus was detected in a very low amount and for a very short time in blood and spleen of goslings and only in blood of ducklings. 相似文献
36.
J Marcaník J Kocisová K Bod'a T Pauer M Belák R Skarda 《Archives of Animal Nutrition》1976,26(11):757-763
Histological and histochemical studies were carried out on the gastro-intestinal mucosa of three experimental cows (roughages/maize silage) and three control animals. The animals were slaughtered on termination of the long-term trial. Mucosa samples were taken, for further study, from the rumen, the duodenum, the jejunum, the large intestine and the appendix. Histochemical analysis did not reveal any essential differences in the activities of non-specific esterase, alkaline and acid phosphatase and lactic acid dehydrogenase in the mucosa of the rumen, the large and the small intestine and the appendix of both the experimental animals and the controls. The experimental animals were found to exhibit a higher rate of glutamate-dehydrogenase activity in the ruminal mucosa and in the mucosa of the large and small intestine. A higher succinate dehydrogenase activity was observed in the ruminal mucosa of the experimental animals, relative to that of the controls, while the activity in the intestinal mucosa was decreased. Only slight changes were noted in the activity of the enzymatic systems tested. Electron microscopic studies did not reveal any differences in the ultrastructure of the epithelial cells of the ruminal mucosa in both the experimental animal and the controls. 相似文献
37.
The protective effect of a lyophilized vaccine against Marek's disease ("Keramvac"--Pfizer), prepared from a cell-free turkey's herpesvirus (strain FC 126), was compared in field trials with losses in the group of non-vaccinated chickens. Under the indicated conditions, the vaccine had only a 50.86% effectiveness. The possible causes of the reduced vaccination effect are discussed with regard to the pathomorphological and virological findings suggesting, among others, an increased incidence of the symptoms of the classical form of Marek's disease in the population investigated. 相似文献
38.
Of 62 strains of Staphylococcus aureus, isolated from milk samples of dairy-cows with staphylococcic mastitis from five agricultural enterprises, 68 p. c. could be typified as bacteriophages. In 42 typified strains, altogether 17 different phage pictures were found, in which case, in the different agricultural enterprises, the number of phage picture fluctuated between 1 and 8. Phage picture 42 D was found and dominated in all the agricultural enterprises. Of the typified strains, 76% could be ranked only into one phage group and 24% in the "M" group (= miscellaneous). Of 32 typified strains, 56.3% belonged to phage group IV, 25% to group III, 12.5% to group I, and 6.2% to group II. 相似文献
39.
Of 62 strains of Staphylococcus aureus, isolated from milk samples of dairy-cows with staphylococcic mastitis from five agricultural enterprises, 68 p. c. could be typified as bacteriophages. In 42 typified strains, altogether 17 different phage pictures were found, in which case, in the different agricultural enterprises, the number of phage picture fluctuated between 1 and 8. Phage picture 42 D was found and dominated in all the agricultural enterprises. Of the typified strains, 76% could be ranked only into one phage group and 24% in the "M" group (= miscellaneous). Of 32 typified strains, 56.3% belonged to phage group IV, 25% to group III, 12.5% to group I, and 6.2% to group II. 相似文献
40.
Z Hubálek 《Folia parasitologica》1975,22(1):73-79
Samples of pigeon droppings were taken from 7 sites in a church tower contaminated with C. neoformans, and the distribution patterns of the fungus were studied. From various sites, 0 to 3 x 10(5) viable C. neoformans particles were recovered per one gram of dry excreta. The factors causing the different density of C. neoformans population in the habitat were: uric acid share of the total nitrogen, creatinine content, sunlight and probably pH. Chemical composition of the substrate is the primary factor in the distribution of C. neoformans in droppings. 相似文献