全文获取类型
收费全文 | 1317篇 |
免费 | 56篇 |
专业分类
林业 | 132篇 |
农学 | 25篇 |
基础科学 | 3篇 |
227篇 | |
综合类 | 138篇 |
农作物 | 52篇 |
水产渔业 | 75篇 |
畜牧兽医 | 635篇 |
园艺 | 21篇 |
植物保护 | 65篇 |
出版年
2021年 | 20篇 |
2020年 | 31篇 |
2019年 | 33篇 |
2018年 | 21篇 |
2017年 | 25篇 |
2016年 | 25篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 53篇 |
2012年 | 44篇 |
2011年 | 68篇 |
2010年 | 44篇 |
2009年 | 36篇 |
2008年 | 67篇 |
2007年 | 58篇 |
2006年 | 52篇 |
2005年 | 42篇 |
2004年 | 56篇 |
2003年 | 54篇 |
2002年 | 32篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 24篇 |
1998年 | 15篇 |
1996年 | 10篇 |
1994年 | 13篇 |
1992年 | 21篇 |
1991年 | 29篇 |
1990年 | 15篇 |
1989年 | 28篇 |
1988年 | 10篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1982年 | 10篇 |
1980年 | 11篇 |
1979年 | 17篇 |
1978年 | 15篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 15篇 |
1973年 | 11篇 |
1972年 | 14篇 |
1970年 | 20篇 |
1969年 | 11篇 |
1968年 | 14篇 |
1967年 | 21篇 |
1966年 | 9篇 |
排序方式: 共有1373条查询结果,搜索用时 20 毫秒
11.
12.
Thomas R. De Ridder Justine E. Campbell Cheryl Burke‐Schwarz David Clegg Emily L. Elliot Samuel Geller Wendy Kozak Stephen T. Pittenger Jennifer B. Pruitt Jocelyn Riehl Julie White Melissa L. Wiest Chad M. Johannes John Morton Pamela D. Jones Peter F. Schmidt Victoria Gordon Paul Reddell 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2021,35(1):415-429
13.
14.
Coetzee JF Schmidt PL Apley MD Reinbold JB Kocan KM 《American journal of veterinary research》2007,68(8):872-878
OBJECTIVE: To compare sensitivity of a complement fixation (CF) test and competitive ELISA (cELISA) for detection of Anaplasma marginale in experimentally infected steers. ANIMALS: 40 crossbred (Angus-Simmental) steers. PROCEDURES: Steers were inoculated with 2.6 x 10(9) A marginale-infected erythrocytes (day 0). Blood samples were collected on days 9, 13, 20, 28, 34, 41, 61, 96, 126, and 156 days after inoculation. The percentage of parasitized erythrocytes (PPE) was determined by microscopic examination of stained blood films, and sera were evaluated with the CF test and cELISA by use of USDA-approved methods. Sensitivity and agreement (kappa statistic) between the 2 methods were determined. Persistent infections were confirmed by inoculation of blood obtained from infected steers into susceptible, splenectomized calves. RESULTS: 9 days after inoculation, sensitivity of the cELISA was 47.5%, whereas the CF test failed to identify seropositive steers. After day 13, sensitivity of the cELISA and CF test was 100% and 20%, respectively. During peak parasitemia (day 20), sensitivity of the cELISA and CF test was 100%. Thereafter, sensitivity of the CF test fluctuated between 7.5% and 37.5%, whereas sensitivity of the cELISA remained at 100%. Overall sensitivity of the cELISA and CF test was 94.8% and 26.5%, respectively (kappa statistic, 0.039). CONCLUSIONS AND CLINICAL RELEVANCE: The cELISA had superior sensitivity for serologic detection of A marginale.The CF test and cELISA each had a high percentage of false-negative results during the prepatent period. These findings are relevant for export certification and anaplasmosis prevention or eradication programs. 相似文献
15.
Enterohemorrhagic Escherichia coli (EHEC) are a subgroup of Shiga toxin-producing Escherichia coli (STEC) that are able to cause serious food-borne intestinal diseases which can be followed in 5 to 15% by extraintestinal sequelae such as the hemolytic-uremic syndrome (HUS). One of the major pathogenicity factors of EHEC is the production of one or more Shiga toxins (Stx), which act as inhibitors of protein biosynthesis and have profound effects on the signal transduction and immunological response in eukaryotic cells. The stx genes are located in the genome of heterogeneous, lambdoid, functional or cryptic bacteriophages and are expressed during the phage life cycle. Due to the linkage between the phage life cycle and stx expression, STEC and their bacteriophages are useful as a model for the analysis of stress response and virulence of this food-borne pathogen. 相似文献
16.
17.
Diniz PP Maggi RG Schwartz DS Cadenas MB Bradley JM Hegarty B Breitschwerdt EB 《Veterinary research》2007,38(5):697-710
The purpose of this study was to determine the serological and molecular prevalence of Bartonella spp. infection in a sick dog population from Brazil. At the S?o Paulo State University Veterinary Teaching Hospital in Botucatu, 198 consecutive dogs with clinicopathological abnormalities consistent with tick-borne infections were sampled. Antibodies to Bartonella henselae and Bartonella vinsonii subsp. berkhoffii were detected in 2.0% (4/197) and 1.5% (3/197) of the dogs, respectively. Using 16S-23S rRNA intergenic transcribed spacer (ITS) primers, Bartonella DNA was amplified from only 1/198 blood samples. Bartonella seroreactive and/or PCR positive blood samples (n=8) were inoculated into a liquid pre-enrichment growth medium (BAPGM) and subsequently sub-inoculated onto BAPGM/blood-agar plates. PCR targeting the ITS region, pap31 and rpoB genes amplified B. henselae from the blood and/or isolates of the PCR positive dog (ITS: DQ346666; pap31 gene: DQ351240; rpoB: EF196806). B. henselae and B. vinsonii subsp. berkhoffii (pap31: DQ906160; rpoB: EF196805) co-infection was found in one of the B. vinsonii subsp. berkhoffii seroreactive dogs. We conclude that dogs in this study population were infrequently exposed to or infected with a Bartonella species. The B. henselae and B. vinsonii subsp. berkhoffii strains identified in this study are genetically similar to strains isolated from septicemic cats, dogs, coyotes and human beings from other parts of the world. To our knowledge, these isolates provide the first Brazilian DNA sequences from these Bartonella species and the first evidence of Bartonella co-infection in dogs. 相似文献
18.
Lasmar Chaim J. Queiroz Antônio C. M. Rosa Clarissa Carvalho Nathália S. Schmidt Fernando A. Solar Ricardo R. C. Paolucci Lucas N. Cuissi Rafael G. Ribas Carla R. 《Landscape Ecology》2021,36(9):2583-2597
Landscape Ecology - Harmful effects of habitat loss and fragmentation can be detected across multiple spatial scales, yet most studies that aim to characterize these effects take place at a single... 相似文献
19.
Walter Oettmeier Ursula Hilp Wilfried Draber Carl Fedtke Robert R. Schmidt 《Pest management science》1991,33(4):399-409
Weeds resistant to the s-triazine herbicide atrazine also show resistance to the triazinone herbicide metribuzin. However, with highly lipophilic triazinones, thylakoids isolated from atrazine-resistant Amaranthus retroflexus (mutation at position Ser264 of the photosystem II D-1 reaction centre protein) in general show a higher pI50 value in photosystem II electron transport than those from the wild type (i.e. negative cross-resistance; ‘supersensitivity’). A quantitative structure–activity relationship (QSAR) can be established, wherein the lipophilicity of the compound plays a major role. In in-vivo experiments, it was found that the triazinone DRW2698 killed resistant Amaranthus retroflexus and Chenopodium album whereas the wild type was almost unaffected. Triazinones were further investigated in five different mutants of Chlamydomonas rheinhardtii (mutations in the D-1 protein at positions Ser264, Ala251, Leu275, Phe255, and Val219). Inhibitory activity of all triazinones was generally enhanced in the Phe255 mutant but decreased in the Val219 mutant. In the other mutants, biological activity was decreased when position 3 of the triazinone was substituted by CH3, OCH3, SCH3, NHCH3 or N(CH3)2. However, negative cross-resistance was again observed when this position was occupied by free thiol. It is therefore suggested that these two groups of triazinones orient themselves differently within the herbicide binding niche of the photosystem II D-1 protein. 相似文献
20.
The metabolism of [ 14 C]-4-nitrophenol and [ 14 C]-3,4-dichloroaniline (the xenobiotics are degradation products of parathion and propanil, respectively) was studied in cell suspension cultures of carrot (Daucus carota L.). 4-Nitrophenol was transformed almost quantitatively to water-soluble conjugates with minor amounts of non-extractable residues. The conjugates identified were 1-(O-β-D-glucopyranosyl)-4-nitrobenzene and 1-(6′-O-malonyl-O-β-D-glucopyranosyl)-4-nitrobenzene. In addition, two unidentified metabolites were observed, possibly a disaccharide and another malonylated glycoside of 4-nitrophenol. Time-course studies demonstrated that 4-nitrophenol was rapidly taken up and conjugated; all metabolites remained associated with the cells rather than nutrient medium. 3,4-Dichloroaniline was transformed quantitatively to water-soluble conjugates and bound residues (3.6%). The water-soluble metabolites were identified as 6′-O-malonyl-N-(β-D-glucopyranosyl)-3,4-dichloroaniline, N-(β-D-glucopyranosyl)-3,4-dichloroaniline and N-malonyl-3,4-dichloroaniline. A time-course study showed that the glucosides were formed initially, then decreased, possibly due to hydrolysis. This decrease was paralleled by an increase of the main metabolite, N-malonyl-3,4-dichloroaniline, which was predominantly recovered from the medium. 相似文献