全文获取类型
收费全文 | 592篇 |
免费 | 47篇 |
专业分类
林业 | 21篇 |
农学 | 19篇 |
基础科学 | 1篇 |
84篇 | |
综合类 | 45篇 |
农作物 | 84篇 |
水产渔业 | 103篇 |
畜牧兽医 | 241篇 |
园艺 | 7篇 |
植物保护 | 34篇 |
出版年
2023年 | 5篇 |
2022年 | 13篇 |
2021年 | 21篇 |
2020年 | 18篇 |
2019年 | 21篇 |
2018年 | 33篇 |
2017年 | 15篇 |
2016年 | 24篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 34篇 |
2012年 | 36篇 |
2011年 | 52篇 |
2010年 | 34篇 |
2009年 | 30篇 |
2008年 | 27篇 |
2007年 | 32篇 |
2006年 | 23篇 |
2005年 | 28篇 |
2004年 | 13篇 |
2003年 | 34篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有639条查询结果,搜索用时 15 毫秒
221.
Ideta A Hayama K Urakawa M Jung YG Lim KT Lee WY Song HB Aoyagi Y 《The Journal of reproduction and development》2007,53(5):1015-1021
In this study, we first attempted to determine whether the timing of artificial insemination affects the sex ratio of seven-day-old embryos in superovulated Holstein heifers. The superovulatory treatment consisted of eight decreasing doses of FSH for 4 days and 2 doses of PGF(2alpha) given with the last two doses of FSH. The superovulated heifers were given a GnRH analogue 48 h after the first PGF(2alpha) treatment and were artificially inseminated 48 h (n=10) or 56 h (n=8) after the first PGF(2alpha) treatment. There were no significant differences in the percentages of unfertilized ova and transferable embryos (grades 1 to 3) between the two groups. The proportions of female grade 1 embryos did not significantly differ from the expected ratio of 50:50 (49.3% at 48 h and 52.5% at 56 h). We then compared the estrous behavior and superovulatory responses of the heifers with a proportion of female embryos of 50% or less (n=7, Low group) to those of the heifers with a proportion of female embryos of more than 50% (n=9, High group). The Low group had a longer duration of estrus and a higher superovulatory response than the High group. These findings offer little encouragement for prediction of the population of female embryos collected from superovulated heifers. Further studies are necessary to evaluate to what degree maternal hormone levels are related to estrus duration and sex ratio. 相似文献
222.
223.
Effects of population, age, and cultivation methods on ginsenoside content of wild American ginseng (Panax quinquefolium) 总被引:1,自引:0,他引:1
Genotype and environmental effects on ginsenoside content among eight wild populations of American ginseng (Panax quinquefolium) were investigated. Root concentrations of six ginsenosides were determined at the time of collection of plants from the wild (T0) and 2 years (T2) after transplanting roots from each of the eight populations to each of two different forest garden locations. Both location and population had significant effects on root and shoot growth. Overall, ginsenoside Rb1 was most abundant, followed by Rg1 and Re. Concentrations of Rg1 and Re were inversely related among and within populations. The relative ranking of populations differed depending upon the particular ginsenoside and sampling time. The relative importance of genotype and environment was not the same for all ginsenosides. Ginsenoside Re was influenced by population but not location, whereas Rb1, Rc, and Rb2 were influenced only by location (environment), while Rg1 and Rd were influenced by both. Ginsenoside levels were consistently lower, but growth was consistently higher at the more intensively managed garden location. 相似文献
224.
Due to the lack of large cross-section wood, the concern regarding the utilization of small-diameter logs from forest thinning has increased as a worldwide issue recently. Round shape is advantageous to efficient use of small-diameter logs, there is a difficulty of drying and preservative treatment. It is necessary to apply a new technique. In this study, center-boring technology was applied to improve the efficiency of manufacturing. The effect of a hole was not expected to make a significant effect on the flexural performance because the hole is located at the centroid of beam under bending moment. Unlike a round timber beam, the failure of center-bored round timber beam starts with a crack and is followed by a longitudinal split. When designing center-bored round timber as guardrail beam, additional strength reduction by flattening should be considered. 相似文献
225.
Seong-Rin Lim 《Water, air, and soil pollution》2009,199(1-4):67-77
Environmental and energy performances of a water network system (WNS) utilizing water reuse are compared to those of a conventional water system (CWS) supplying only freshwater from the perspective of an entire economy and life cycle. Environmental input–output analysis (EIOA) is used to evaluate their air pollutant emissions and energy consumptions. The global warming potential and the emissions of carbon monoxide and of volatile organic compounds from the WNS are less than those from the CWS because of the decrease in the consumption of industrial water, while the emissions of sulfur dioxide and of nitrogen oxides and energy consumption from the WNS are greater because of the increase in electricity consumption for pumping. For perfectly environmentally-friendly water reuse, electricity consumption should be constrained or optimized in water network synthesis, and primary energy mix for electricity generation should be shifted towards renewable energy. 相似文献
226.
Soo-Hyeon Kim Byung-Joon Seung Seung-Hee Cho Ha-Young Lim Min-Kyung Bae Jung-Hyang Sur 《Journal of veterinary science (Suw?n-si, Korea)》2021,22(5)
BackgroundHepatocellular carcinoma is the most common primary hepatic malignancy in humans and dogs. Several differentially expressed molecules have been studied and reported in human hepatocellular carcinoma and non-neoplastic liver lesions. However, studies on the features of canine hepatocellular carcinoma are limited, especially related to the differential characteristics of neoplastic and non-neoplastic lesions.ObjectivesThe study''s objective was 1) to examine and evaluate the expression of arginase-1, P-glycoprotein, and cytokeratin 19 in canine liver tissues and 2) to investigate the differential features of hepatocellular carcinomas, liver tissue with non-neoplastic lesions, and paracancerous liver tissues in dogs.MethodsThe expression levels of three markers underwent immunohistochemical analysis in 40 non-neoplastic liver tissues, 32 hepatocellular carcinoma tissues, and 11 paracancerous liver tissues. Scoring of each marker was performed semi-quantitatively.ResultsArginase-1 and P-glycoprotein were significantly downregulated in hepatocellular carcinoma, compared with hepatic tissues with non-neoplastic diseases (p < 0.001). Expression levels of arginase-1 and P-glycoprotein were also significantly lower in hepatocellular carcinoma than in paracancerous liver tissues (arginase-1, p = 0.0195; P-glycoprotein, p = 0.047). Few cytokeratin 19-positive hepatocytes were detected and only in one hepatocellular carcinoma and one cirrhotic liver sample.ConclusionsThe results of this study suggest that downregulation of arginase-1 and P-glycoprotein is a feature of canine hepatocellular carcinoma; thus, those markers are potential candidates for use in differentiating hepatocellular carcinomas from non-neoplastic liver lesions in dogs. 相似文献
227.
Dong-Jun An Wooseog Jeong Hye-Young Jeoung Myoung-Heon Lee Jee-Yong Park Ji-Ae Lim Bong-Kyun Park 《Research in veterinary science》2012,93(1):515-519
A novel peptide nucleic acid (PNA)-based array was developed for use in ante-mortem antigenic typing discrimination in dogs with canine parvovirus (CPV). Cyclic benzothiazole-2-sulfonyl PNA monomers were synthesized that recognized GTA (CPV-2) and TAT (CPV-2a, -2b and -2c) at the nt 913–915 positions, and AAT (CPV-2 and CPV-2a), GAT (CPV-2b), and GAA (CPV-2c) at the nt 1276–1278 positions of the VP2 gene. The detection limits for aa 305 and aa 426 of the VP2 proteins belonging to the four CPV antigenic types were determined optically to be 40–2000 DNA copies, and the optimal cut-off fluorescence signaling value was fixed at 5000. The PNA array described here was developed from 135 field dog fecal specimens and had 89.8% (62/69) sensitivity and 90.4% (66/73) specificity compared with a real-time PCR using the TaqMan assay, a gold standard method. This CPV PNA array could be used together with MGB probe assays as an attractive novel tool for ante-mortem antigenic typing discrimination. 相似文献
228.
Audrey C. Muguet‐Chanoit DVM MS Ji‐Hey Lim DVM PhD Ryan Gallagher DVM Zachary Niman DVM Diplomate ACVIM Neurology Stacy Dillard DVM Diplomate ACVIM Neurology James Campbell DVM PhD Peter Early DVM Diplomate ACVIM Neurology Karen R. Muñana DVM MS Diplomate ACVIM Neurology Courtenay Freeman DVM Marc Kent DVM Diplomate ACVIM Neurology Carley Giovanella DVM Diplomate ACVIM Neurology 《Veterinary surgery : VS》2012,41(2):200-206
229.
Kang BT Kim SG Lim CY Gu SH Jang DP Kim YB Kim DY Woo EJ Cho ZH Park HM 《The Canadian veterinary journal. La revue veterinaire canadienne》2010,51(9):986-992
This study characterized the [(18)F]2-deoxy-2-fluoro-D-glucose positron emission tomography (FDG-PET) findings of encephalitis in dogs and assessed the role of FDG-PET in the diagnosis of meningoencephalitis. The medical records, magnetic resonance (MR), and FDG-PET images of 3 dogs with necrotizing meningoencephalitis (NME), 1 dog with granulomatous meningoencephalitis (GME), and 1 dog with meningoencephalitis of unknown etiology (MUE) were reviewed. On the FDG-PET, glucose hypometabolism was identified in the dog with NME, whereas hypermetabolism was noted in the dog with GME. The T2-weighted images (WI) and fluid attenuated inversion recovery (FLAIR) images were characterized by hyperintensity, whereas the signal intensity of the lesions on the T1-WI images was variable. The metabolic changes on the brain FDG-PET corresponded well to the hyper- and hypointense lesions seen on the MR imaging. This type of tomography (FDG-PET) aided in the differentiation of different types of inflammatory meningoencephalitis when the metabolic data was combined with clinical and MR findings. 相似文献
230.
BACKGROUND: Identification of Bactrocera carambolae Drew and Hancock, B. papayae Drew and Hancock, B. tau Walker, B. latifrons Hendel, B. cucurbitae Coquillett, B. umbrosa Fabricius and B. caudata Fabricius would pose a problem if only a body part or an immature stage were available. Analysis of polymerase chain reaction–restriction fragment length polymorphism (PCR‐RFLP) of cytochrome oxidase I (COI) gene using primers COIR, COIF, UEA7 and UEA10 and restriction enzymes (MseI, RsaI and Alu1) was carried out. The banding profiles in the electrophoresis gel were analysed. RESULTS: The COI gene in six Bactrocera spp. was successfully amplified by COIR and COIF, as well as UEA7 and UEA10, while B. caudata was amplified successfully only by UEA primers. Using COI amplified PCR products and restriction enzymes, distinct banding profiles for B. tau, B. latifrons, B. cucurbitae and B. umbrosa were observed, but not for B. carambolae and B. papayae. However, using UEA7, UEA10 and RsaI, B. caudata could be identified, while B. carambolae and B. papayae might possibly be separated from one another. It was also shown that adult body parts or immature life stages of B. carambolae, B. papayae, B. latifrons and B. cucurbitae produced the same banding profiles as the adults. CONCLUSION: PCR‐RFLP analyses are able to identify positively five Bactrocera species, while B. papayae and B. carambolae might possibly be separated from one another, even if immature life stages or adult body parts are used. Copyright © 2009 Society of Chemical Industry 相似文献