全文获取类型
收费全文 | 809篇 |
免费 | 74篇 |
国内免费 | 2篇 |
专业分类
林业 | 46篇 |
农学 | 18篇 |
基础科学 | 3篇 |
139篇 | |
综合类 | 84篇 |
农作物 | 28篇 |
水产渔业 | 60篇 |
畜牧兽医 | 434篇 |
园艺 | 21篇 |
植物保护 | 52篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 21篇 |
2019年 | 21篇 |
2018年 | 20篇 |
2017年 | 31篇 |
2016年 | 26篇 |
2015年 | 33篇 |
2014年 | 35篇 |
2013年 | 33篇 |
2012年 | 52篇 |
2011年 | 63篇 |
2010年 | 47篇 |
2009年 | 46篇 |
2008年 | 64篇 |
2007年 | 62篇 |
2006年 | 53篇 |
2005年 | 35篇 |
2004年 | 50篇 |
2003年 | 42篇 |
2002年 | 37篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有885条查询结果,搜索用时 15 毫秒
1.
Tim J Evans 《Veterinary Clinics of North America: Equine Practice》2002,18(2):371-8, viii
Ergopeptine alkaloid exposure is common in pregnant mares. Many mares live in geographic areas where Neotyphodium coenophialum-infected tall fescue is the dominant grass in pastures and hay. A variety of grasses and cereal grains can be infected by Claviceps purpurea, and fungal sclerotia can contaminate forage and especially ground and pelleted feed. An understanding of the endocrine alterations associated with ergopeptine alkaloid exposure during pregnancy is necessary for the diagnosis of potential exposure to these compounds and for eective prophylaxis and therapy. 相似文献
2.
3.
4.
5.
Gunn-Moore DA McFarland SE Schock A Brewer JI Crawshaw TR Clifton-Hadley RS Shaw DJ 《Journal of Feline Medicine and Surgery》2011,13(12):945-952
This study investigated 339 cases of feline mycobacterial infection, with histopathology findings from 225 cases, and treatment and outcome information from 184 cases. Tissue samples from cats with cutaneous lesions or suspicious masses at exploratory laparotomy were submitted to the Veterinary Laboratories Agency for mycobacterial culture over a 4-year period to December 2008. The study reviewed the files for information about histopathology, treatment and outcome, and blindly reviewed histopathological changes (including staining for acid-fast bacteria [AFB]) in a sub-set of 45 cases. When a cat is suspected of having a mycobacterial infection, accurate identification of the species involved helps to determine possible treatment options and prognosis. The study confirmed that histopathology and the presence of AFB are useful tools in the recognition of mycobacterial infection. Unfortunately, they did little to help determine the species of mycobacteria involved. The study identified a group of cats that were negative for AFB at the primary laboratory, but from which mycobacteria could be cultured; commonly Mycobacterium bovis or Mycobacterium microti. The study also identified a group of cats which where culture negative, despite typical signs of mycobacterial infection and positive AFB staining. Many cases responded favourably to treatment (56% of the cases where information was available), and many cats gained complete remission (42%). However, relapses were common (64%) and often followed by pulmonary and/or systemic spread that may have resulted from treatment with short courses of single drugs. This study shows that the diagnosis and treatment of feline mycobacteriosis is complex and challenging. 相似文献
6.
Boyer TC Ward MP Wallace RL Singer RS 《American journal of veterinary research》2007,68(11):1212-1219
OBJECTIVE: To estimate seroprevalence of bluetongue virus (BTV) and the geographic distribution of seropositive cattle herds in Illinois and western Indiana. SAMPLE POPULATION: 10,585 serum samples obtained from cattle in 60 herds during 3 transmission seasons (2000 through 2002). PROCEDURES: In a longitudinal study, serum samples were tested for BTV antibodies by use of a competitive ELISA. Four geographic zones were created by use of mean minimum January temperature. A multivariable mixed-effects logistic regression model with a random effect for herd was used to estimate seropositive risk for zone, age of cattle, herd type, and transmission season. RESULTS: Overall, BTV antibodies were detected in 156 (1.5%) samples. Estimated seroprevalence in 2000, 2001, and 2002 was 1.49%, 0.97%, and 2.18%, respectively. Risk of being seropositive for BTV was associated with geographic zone and age. Seroprevalence increased progressively from northern to southern zones, with no evidence of BTV infection in the northernmost zone. In the southernmost zone, annual seroprevalence ranged from 8.65% to 11.00%. Adult cattle were 2.35 times as likely as juvenile cattle to be seropositive. CONCLUSIONS AND CLINICAL RELEVANCE: Overall seroprevalence was lower than has been reported for Illinois cattle. Bluetongue virus antibodies were distributed heterogeneously in this region. Only in the southernmost zone was seroprevalence consistently > 2%. Regionalization of BTV risk based on state borders does not account for such variability. Serologic data could be combined with landscape, climate, and vector data to develop predictive models of BTV risk within transitional regions of the United States. 相似文献
7.
Kreuder C Miller MA Lowenstine LJ Conrad PA Carpenter TE Jessup DA Mazet JA 《American journal of veterinary research》2005,66(2):289-299
OBJECTIVE: To describe cardiac lesions and identify risk factors associated with myocarditis and dilated cardiomyopathy (DCM) in beach-cast southern sea otters. ANIMALS: Free-ranging southern sea otters. PROCEDURE: Sea otters were necropsied at the Marine Wildlife Veterinary Care and Research Center from 1998 through 2001. Microscopic and gross necropsy findings were used to classify sea otters as myocarditis or DCM case otters or control otters. Univariate, multivariate, and spatial analytical techniques were used to evaluate associations among myocarditis; DCM; common sea otter pathogens; and potential infectious, toxic, and nutritional causes. RESULTS: Clusters of sea otters with myocarditis and DCM were identified in the southern aspect of the sea otter range from May to November 2000. Risk factors for myocarditis included age, good body condition, and exposure to domoic acid and Sarcocystis neurona. Myocarditis associated with domoic acid occurred predominantly in the southern part of the range, whereas myocarditis associated with S. neurona occurred in the northern part of the range. Age and suspected previous exposure to domoic acid were identified as major risk factors for DCM. A sample of otters with DCM had significantly lower concentrations of myocardial L-carnitine than control and myocarditis case otters. CONCLUSIONS AND CLINICAL RELEVANCE: Cardiac disease is an important cause of death in southern sea otters. Domoic acid toxicosis and infection with S. neurona are likely to be 2 important causes of myocarditis in sea otters. Domoic acid-induced myocarditis appears to progress to DCM, and depletion of myocardial L-carnitine may play a key role in this pathogenesis. 相似文献
8.
A change in the European Union energy policy has markedly promoted the expansion of biogas production.Consequently,large amounts of nutrient-rich residues are being used as organic fertilizers.In this study,a pot experiment was conducted to simulate the high-risk situation of enhanced greenhouse gas (GHG) emissions following organic fertilizer application in energy maize cultivation.We hypothesized that cattle slurry application enhanced CO2 and N2O fluxes compared to biogas digestate because of the overall higher carbon (C) and nitrogen (N) input,and that higher levels of CO2 and N2O emissions could be expected by increasing soil organic C (SOC) and N contents.Biogas digestate and cattle slurry,at a rate of 150 kg NH4+-N ha-1,were incorporated into 3 soil types with low,medium,and high SOC contents (Cambisol,Mollic Gleysol,and Sapric Histosol,termed Clow,Cmedium,and Chigh,respectively).The GHG exchange (CO2,CH4,and N2O) was measured on 5 replicates over a period of 22 d using the closed chamber technique.The application of cattle slurry resulted in significantly higher CO2 and N2O fluxes compared to the application of biogas digestate.No differences were observed in CH4 exchange,which was close to zero for all treatments.Significantly higher CO2 emissions were observed in Chigh compared to the other two soil types,whereas the highest N2O emissions were observed in Cmedium.Thus,the results demonstrate the importance of soil type-adapted fertilization with respect to changing soil physical and environmental conditions. 相似文献
9.
10.
Navid Adnani Emmanuel Vazquez-Rivera Srikar N. Adibhatla Gregory A. Ellis Doug R. Braun Tim S. Bugni 《Marine drugs》2015,13(10):6082-6098
With respect to bacterial natural products, a significant outcome of the genomic era was that the biosynthetic potential in many microorganisms surpassed the number of compounds isolated under standard laboratory growth conditions, particularly among certain members in the phylum Actinobacteria. Our group, as well as others, investigated interspecies interactions, via co-culture, as a technique to coax bacteria to produce novel natural products. While co-culture provides new opportunities, challenges exist and questions surrounding these methods remain unanswered. In marine bacteria, for example, how prevalent are interspecies interactions and how commonly do interactions result in novel natural products? In an attempt to begin to answer basic questions surrounding co-culture of marine microorganisms, we have tested both antibiotic activity-based and LC/MS-based methods to evaluate Micromonosporaceae secondary metabolite production in co-culture. Overall, our investigation of 65 Micromonosporaceae led to the identification of 12 Micromonosporaceae across three genera that produced unique metabolites in co-culture. Our results suggest that interspecies interactions were prevalent between marine Micromonosporaceae and marine mycolic acid-containing bacteria. Furthermore, our approach highlights a sensitive and rapid method for investigating interspecies interactions in search of novel antibiotics, secondary metabolites, and genes. 相似文献