全文获取类型
收费全文 | 175122篇 |
免费 | 9858篇 |
国内免费 | 97篇 |
专业分类
林业 | 7331篇 |
农学 | 5813篇 |
基础科学 | 1080篇 |
21970篇 | |
综合类 | 26486篇 |
农作物 | 6493篇 |
水产渔业 | 8886篇 |
畜牧兽医 | 93274篇 |
园艺 | 2301篇 |
植物保护 | 11443篇 |
出版年
2019年 | 1704篇 |
2018年 | 2737篇 |
2017年 | 2971篇 |
2016年 | 2769篇 |
2015年 | 2427篇 |
2014年 | 2922篇 |
2013年 | 7237篇 |
2012年 | 5273篇 |
2011年 | 6304篇 |
2010年 | 4252篇 |
2009年 | 4277篇 |
2008年 | 6191篇 |
2007年 | 6058篇 |
2006年 | 5638篇 |
2005年 | 5185篇 |
2004年 | 4985篇 |
2003年 | 5104篇 |
2002年 | 4692篇 |
2001年 | 5805篇 |
2000年 | 5690篇 |
1999年 | 4601篇 |
1998年 | 1874篇 |
1997年 | 1842篇 |
1996年 | 1684篇 |
1995年 | 2038篇 |
1994年 | 1737篇 |
1993年 | 1742篇 |
1992年 | 3548篇 |
1991年 | 3789篇 |
1990年 | 3693篇 |
1989年 | 3687篇 |
1988年 | 3381篇 |
1987年 | 3358篇 |
1986年 | 3379篇 |
1985年 | 3228篇 |
1984年 | 2636篇 |
1983年 | 2375篇 |
1982年 | 1561篇 |
1979年 | 2306篇 |
1978年 | 1800篇 |
1977年 | 1649篇 |
1976年 | 1600篇 |
1975年 | 1672篇 |
1974年 | 2001篇 |
1973年 | 2051篇 |
1972年 | 1959篇 |
1971年 | 1732篇 |
1970年 | 1809篇 |
1969年 | 1708篇 |
1967年 | 1495篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The morphology of Onchocerca lupi, responsible for canine ocular onchocercosis, is unique within the genus. Earlier analyses of the 5S ribosomal RNA gene spacer region sequence of the parasite and the 16S ribosomal RNA gene sequence of its Wolbachia endosymbiotic bacteria (Rickettsiales) supported the morphological and biological arguments that O. lupi is a distinct species. However, the exact phylogenetic position of O. lupi and its endosymbiont could not be unambiguously determined. Herein we report analyses based on the mitochondrial cytochrome oxidase I (COI) gene of the filarial species and the Wolbachia surface protein (wsp) and the bacterial cell-cycle ftsZ genes of their wolbachiae. Our results indicate that O. lupi separated from other Onchocerca spp. early in evolution. This is in line with the previous morphological analysis demonstrating that O. lupi is an atypical Onchocerca species showing both primitive and evolved characters. The phylogenetic trees generated for the COI sequences of filariae and the wsp and ftsZ sequences of their wolbachiae were congruent with each other, which supports the hypothesis that nematodes and their Wolbachia endobacteria share a long co-evolutionary history. 相似文献
992.
993.
A model of limb deviation induced by hemi-circumferential periosteal stripping of the distal tibiotarsus of domestic chicks is described. This model has been developed to study the effects of periosteal stripping on the cellular, mechanical, vascular, and biochemical status of the immature bone and growth plate. It is hoped that such studies may further elucidate the mechanisms involved in altered bone growth following periosteal stripping techniques which are used in human and equine orthopaedics for the management of leg length discrepancies and angular limb deformities respectively (Auer and Martens 1980, Warrell and Baker 1987). Hemi-circumferential periosteal stripping of the left distal tibiotarsus of 28-day-old chicks resulted in significant change in metaphyseal-diaphyseal angle with time, compared to both the controls and the untreated right legs (P<0.0001). This model of limb deviation developed rapidly and consistently, and the procedures were well tolerated by the birds over the short survival time (maximum 28 days). 相似文献
994.
Müller G Steinbach G Berndt A Köhler H 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2002,49(9):429-437
In five experiments, lipopolysaccharides (LPS) of Escherichia coli O26:B6 and O111:B4 were applied intravenously, intramuscularly, subcutaneously or intrabronchially in doses of 5000-15,000 U/kg body mass to a total of 47 weaner pigs and compared with the application of sodium chloride. Different parameters of blood cells were investigated, including cell numbers, in vivo interleukin secretion, radical formation, phagocytosis capacity and IL-6 as well as TNFalpha formation ex vivo. Non-specific effects and dependencies on the type of application and LPS dose are discussed. 相似文献
995.
An unusual case of entropion, corneal ulcer and corneal haemorrhages in a one‐humped camel (Camelus dromedaries) is described. The most prominent clinical findings were entropion of both eyelids, severe blephrospasm, epiphora, conjunctivitis, conjunctival oedema, mucopurulent conjunctival discharges, hyperaemia, lacrimation and photophobia. Corneal ulcers and corneal haemorrhages were also observed. 相似文献
996.
Nadine Lamberski J Rachel Reader Lizette F Cook Eileen M Johnson David G Baker Linda J Lowenstine 《Journal of zoo and wildlife medicine》2002,33(2):151-156
A juvenile, female North American opossum (Didelphis virginiana) died of verminous pneumonia caused by Didelphostrongylus haysei despite aggressive treatment with oral fenbendazole, corticosteroids, and antibiotics. This prompted a retrospective study of lungworm infection in opossums, during which 19 additional necropsy reports from opossums were reviewed. Including the subject of this report, a total of 11 (55%) of these cases included a diagnosis of lungworm infection. This diagnosis was considered to have contributed to death in eight out of the 11 cases (73%). Histologically, 10 of the 11 (91%) opossums had granulomatous bronchopneumonia with small to moderate numbers of adult nematodes in the airways and parenchyma. Four of the 11 (36%) opossums had free larvae within the parenchyma or terminal airways. Inflammation was usually associated with larvae, degenerating parasites, and nonintact adult nematodes. Superimposed bacterial pneumonia was evident in three animals, and sections of lung examined from all the opossums were characterized by moderate to severe smooth-muscle hyperplasia in airways, including terminal respiratory bronchioles and alveolar ducts. Nine animals had prominent medial smooth-muscle hyperplasia in small- and medium-sized arterioles. Lesions in other organs, particularly in liver, heart, and gastrointestinal tract, were frequently identified. Three animals had concomitant septicemia or bacterial bronchopneumonia (or both), which contributed to the cause of death. Seven animals had gastric nematodosis (Physaloptera sp.), although three of them had been treated with a 14-day course of fenbendazole. 相似文献
997.
998.
P J Timoney P B Dillon V P Geraghty J F McArdle 《Comparative immunology, microbiology and infectious diseases》1983,6(3):227-234
Aspects of experimental transmission of the causal bacterium of contagious equine metritis (CEM) to albino Swiss mice were investigated. Whereas infection was established in the majority of female mice, the organism was recovered from only a limited number of male mice after challenge. No clinical evidence of infection was observed in the experimental mice. There was only one instance of presumptive venereal transmission of the CEM bacterium. One third of infected females conceived and had normal litters. 相似文献
999.
Comparative studies on three isolates of Breda virus of calves 总被引:8,自引:0,他引:8
G N Woode L J Saif M Quesada N J Winand J F Pohlenz N K Gourley 《American journal of veterinary research》1985,46(5):1003-1010
Three isolates of Breda virus of calves were compared morphologically and antigenically. The isolates demonstrated similar morphology and shared common antigens, as determined by enzyme-linked immunosorbent assay and immunoelectron microscopy. On the basis of results of the hemagglutination-inhibition test, enzyme-linked immunosorbent assay, and immunoelectron microscopy, the 3 isolates were further subdivided into 2 serotypes: serotype 1 (Breda virus 1) represented by the Iowa isolate 1; and serotype 2 (Breda virus 2), by the Ohio isolate and the Iowa isolate 2. The 3 isolates caused diarrhea in gnotobiotic calves. 相似文献
1000.
D. J. STEWART B. L. CLARK J. E. PETERSON D. L. EMERY E. F. SMITH† D. A. GRIFFITHS† I. J. O'DONNELL‡ 《Australian veterinary journal》1985,62(5):153-159
A highly purified pilus vaccine prepared from cells of Bacteroides nodosus strain 198 provided a high level of protection against homologous challenge and small, not statistically significant, levels of protection against challenge with 4 other strains each from different serogroups. In a second experiment, a partially purified pilus vaccine from strain 198 induced significant immunity to 1 of 4 heterologous strains which were different from those used in the first experiment. In a third experiment a strain 198 whole cell vaccine produced significant immunity against 3 of 6 heterologous strains used in the first 2 experiments. There was no obvious relationship between the colony type, degree of piliation and level of cross-protection obtained against a particular strain. The results provide further evidence that immunogens associated with, but distinct from, the pilus are involved in cross-protection and that cross-protective antigens are common to some, but not all, strains. 相似文献