全文获取类型
收费全文 | 164102篇 |
免费 | 8485篇 |
国内免费 | 143篇 |
专业分类
林业 | 6955篇 |
农学 | 4643篇 |
基础科学 | 1090篇 |
18324篇 | |
综合类 | 32622篇 |
农作物 | 6504篇 |
水产渔业 | 7271篇 |
畜牧兽医 | 83934篇 |
园艺 | 1892篇 |
植物保护 | 9495篇 |
出版年
2018年 | 1997篇 |
2017年 | 2239篇 |
2016年 | 2059篇 |
2015年 | 1764篇 |
2014年 | 2185篇 |
2013年 | 5890篇 |
2012年 | 4148篇 |
2011年 | 5102篇 |
2010年 | 3305篇 |
2009年 | 3366篇 |
2008年 | 5122篇 |
2007年 | 4735篇 |
2006年 | 4533篇 |
2005年 | 4261篇 |
2004年 | 4291篇 |
2003年 | 4296篇 |
2002年 | 4066篇 |
2001年 | 4977篇 |
2000年 | 4972篇 |
1999年 | 3759篇 |
1998年 | 1593篇 |
1997年 | 1597篇 |
1995年 | 1857篇 |
1994年 | 1665篇 |
1993年 | 1681篇 |
1992年 | 3386篇 |
1991年 | 3732篇 |
1990年 | 3625篇 |
1989年 | 3619篇 |
1988年 | 3275篇 |
1987年 | 3397篇 |
1986年 | 3565篇 |
1985年 | 3479篇 |
1984年 | 2747篇 |
1983年 | 2511篇 |
1982年 | 1677篇 |
1981年 | 1631篇 |
1979年 | 2583篇 |
1978年 | 2045篇 |
1977年 | 1709篇 |
1976年 | 1619篇 |
1975年 | 1732篇 |
1974年 | 2277篇 |
1973年 | 2325篇 |
1972年 | 2303篇 |
1971年 | 2211篇 |
1970年 | 2103篇 |
1969年 | 1931篇 |
1968年 | 1606篇 |
1967年 | 1720篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Efficacy of ivermectin treatment (0.2 mg/kg) against 28-day experimental infections of Parascaris equorum was determined in 18 pony foals6–17.5 weeks old. There were 6 foals in each group: nontreated control, ivermectin injectable or oral paste. In comparison with larvae found in the nontreated controls, ivermectin injectable or paste was 96.0% and 99.9% efficacious. There was a distinct difference in drug effect against the larger (ca 26mm.) vs the smaller (13–19mm) larvae by the 2 formulations of ivermectin. There were no adverse signs related to treatment of the young foals. 相似文献
102.
T R Thedford L W Johnson 《Veterinary Clinics of North America: Food Animal Practice》1989,5(1):145-157
Although there are notable infectious conditions that are capable of producing clinical disease in the NWC, overall, these species are quite healthy. Of the bacterial diseases, enterotoxemia caused by Clostridium perfringens types C and D would be deemed the most significant in North America, while type A also would be regarded as important in South America. Other important bacterial infections of potential concern are tuberculosis, Johne's disease, anthrax, malignant edema, actinomycosis, tetanus, and the South American condition referred to as alpaca fever, which, to date, has not been observed in North America. Fungal infections include classical ringworm, principally caused by Trichophyton spp., and the cases of coccidioidomycosis that are associated with the arid desert lands of the southwestern United States. Most notable of naturally occurring viral infections in the NWC would be rabies, ecthyma, and a recently described blindness neuropathy that has been associated with the equine herpesvirus I. NWC can be infected experimentally with agents causing hoof-and-mouth disease and vesicular stomatitis, but naturally occurring cases do not seem to occur. Serological evidence of exposure to many viral agents, including blue tongue, parainfluenza 3, bovine respiratory syncytial virus, bovine herpesvirus I, bovine viral diarrhea, influenza A, and rotavirus, has been demonstrated; however, no clinical disease associated with these agents, as yet, is apparent. 相似文献
103.
The responses of some clinical and microbiological parameters of periodontal disease (PD) in sheep were examined subsequent to transferring animals between PD-affected and PD-free farms. Previously healthy animals showed transient deterioration in some clinical, but not microbiological parameters, which suggests either that a different microbiota to the one studied may be more important in the initiation of the disease, or that sampling did not intercept periods of destructive disease activity in the early lesions. In sheep with established disease, those parameters indicative of periodontitis which included pocket depth and bleeding on probing as well as the proportions of black-pigmented Bacteroides species were not significantly altered by environmental changes. This observation suggests that once the disease is established on PD-affected farms, the hand, some clinical signs of the disease including lengthening and mobility of incisor teeth increased in sheep on the PD-affected farm relative to the PD-free farm. This suggests that the disease may have a complex aetiology. 相似文献
104.
W Ahne J R Winton T Kimura 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1989,36(8):561-567
Infectious diseases remain one of the most important limitations to the successful propagation of aquatic animals. Most of the losses caused by pathogens in aquaculture could be prevented by health inspection, adequate environment and sound management practices. Effective control measures, mainly based upon 1) avoidance of pathogens 2) modification of the environment 3) improvement of host resistance 4) vaccination and 5) chemoprophylaxis are described. 相似文献
105.
Enzyme-linked immunosorbent assay for the detection of circulating antigens of Toxoplasma gondii in the serum of cats 总被引:1,自引:0,他引:1
M R Lappin C E Greene A K Prestwood D L Dawe R L Tarleton 《American journal of veterinary research》1989,50(9):1586-1590
An ELISA was developed to detect circulating antigens of Toxoplasma gondii in the serum of cats. For the experiment, toxoplasmosis was induced in a group of cats by oral administration of bradyzoites. An ELISA that detects anti-Toxoplasma IgG, an ELISA to detect circulating antigens, and fecal examinations were performed on samples from each cat for 1 year after inoculation. When coupled with IgG-class antibody measurement, antigen detection can aid in the diagnosis of some cases of subclinical feline toxoplasmosis. 相似文献
106.
A survey of the potential use of synthetic oligopeptides in the field of virology is given. The potential value of synthetic peptides as vaccines and diagnostic antigens is discussed. The advantages compared to conventional vaccines as well as the limitations, e.g. the poor efficiency of immune response, are described. 相似文献
107.
A B Gardner C E Gardner 《Veterinary Clinics of North America: Food Animal Practice》1989,5(3):653-664
Dairy practice often requires substantial time commitments. Those veterinarians with families may find that if they do not actively budget some time for spouse and children, the family unit may suffer. A successful practice and meaningful family life are both possible if the doctor or doctors involved are willing to work for their achievement. 相似文献
108.
The kidney's microvascularization of the Pudu pudu is mostly similar to that of domestic animals. The renal parenchymatous arteries do not give off capsular branches. The majority of the Pudu pudu's glomerula shows spherical shape. Glomerula next to the medulla have a diameter which is an average of 25 microns larger than the diameter of those situated more peripherally. Their volume is comparable to that of the angora rabbit. The capillaries form anastomosis in the inner and outer part of the glomerulus. 相似文献
109.
A total of 739 cattle from nine breeds maintained at the Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska were tested for 42 class I antigens of the bovine major histocompatibility system (BoLA). Each antigen appears to be the product of a distinct co-dominant allele of the BoLA-A locus. The number of antigens present in each breed ranged from a minimum of 10 in Hereford to a maximum of 21 in Charolais cattle. There were large differences among breeds in the frequencies of antigens. The effect of each antigen on birth weight, preweaning weight gain and postweaning weight gain was estimated in a gene substitution model. Each breed was analyzed separately. There were significant effects of some BoLA antigens on birth weight, preweaning weight gain and postweaning weight gain, which is consistent with previous reports showing associations between the major histocompatibility system and growth parameters in mice, rats and pigs. However, further research is necessary to confirm these findings and to determine the biological mechanisms underlying these associations. 相似文献
110.
Corneal diseases are common in domestic rabbits. It is important to carefully evaluate the cornea and the entire eye when rabbit present with clinical signs such as squinting, tearing, or conjunctival hyperemia. Complete ophthalmic examination and general physical examination should be performed on all rabbits with corneal disease. Important diagnostic testing include culture and sensitivity, cytology, and fluorescein staining. Breed predispositions do not occur for most corneal problems, although some diseases are selected genetically in research rabbits. Corneal disease can be a primary condition or can occur secondary to other ocular or systemic disease. 相似文献