首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   317篇
  免费   21篇
林业   12篇
农学   18篇
基础科学   2篇
  55篇
综合类   15篇
农作物   89篇
水产渔业   26篇
畜牧兽医   108篇
园艺   3篇
植物保护   10篇
  2022年   5篇
  2021年   15篇
  2020年   7篇
  2019年   13篇
  2018年   11篇
  2017年   6篇
  2016年   15篇
  2015年   20篇
  2014年   19篇
  2013年   27篇
  2012年   22篇
  2011年   24篇
  2010年   15篇
  2009年   15篇
  2008年   23篇
  2007年   19篇
  2006年   9篇
  2005年   13篇
  2004年   18篇
  2003年   10篇
  2002年   7篇
  2001年   8篇
  2000年   12篇
  1999年   1篇
  1998年   2篇
  1993年   1篇
  1985年   1篇
排序方式: 共有338条查询结果,搜索用时 109 毫秒
61.
Two dogs with acute onset atrial fibrillation (AF) were cardioverted to sinus rhythm by the administration of 2 mg/kg lidocaine given intravenously. Each dog was believed to have AF initiated because of elevated vagal tone. This report has potential clinical impact for a subset of dogs because it offers a treatment to circumvent persistent AF. Furthermore, this encouraging result of a pharmacologic cardioversion suggests that further investigation would be of interest to ascertain the effectiveness and mechanism of the antiarrhythmic action of lidocaine in vagally induced AF.  相似文献   
62.
The production of miniature animals has been suggested for use in organ transplantation. At present, many of the studies about application of animal organs to human have been focused on pigs because of the number of advantages involved and due to their similarities with human. However, a physiological analysis of the organs to be transplanted has not yet been carried out. Therefore, this study analyzed whether or not there were physiological and morphological differences in the hearts of conventionally-reared pigs and micropigs. In this study, the morphological and physiological functions of the heart were examined using radiographic and echocardiographic equipment. In the lateral radiographic view, the heart of the micropig has a larger cardiac long axis : short axis ratio than does the conventional pig, but the difference in the vertebral heart score was not significant. In addition, there were no morphological differences on the X-ray fluoroscopic view. There were no differences in echocardiographic values, except for several values in the left ventricle traces. Overall, it is expected that the values measured in this study will contribute to understanding of the physiological characteristics of micropigs.  相似文献   
63.
Toxicogenomics, the subdiscipline that merges genomics with toxicology, hold the promise to contributing toward the goal of elucidating mechanism by studying genomic profiling related with various drugs. The application of gene expression profiling technology to examine multiple genes and signaling pathways promises a significant advance in understanding the toxic mechanisms of various drugs and prediction of new drug candidate. Toxicogenomics is emerging field combining genomics and bioinformatics to identify and characterize mechanisms of toxicity of drug and various compounds. The principal hypothesis underlying on this field is that chemical-specific pattern of altered gene expression is related with each chemicals properties, especially toxicological property, and it will be revealed using high-density microarray analysis of sample from exposed organisms. So, in this study we compare the gene expression pattern of two anticancer drugs paclitaxel and orally absorbable paclitaxel, using the cDNA microarray. And from the result of this study, it is possible to provide the new possibility for genome-wide insight into mechanism of their anticancer activity and toxicological phenotype.  相似文献   
64.
Seung HS  Lee DD 《Science (New York, N.Y.)》2000,290(5500):2268-2269
One of the great puzzles of visual perception is how an image that is in perpetual flux can still be seen by the observer as the same object. In an informative Perspective, Seung and Lee explain the mathematical intricacies of two new algorithms for modeling the variability of perceptual stimuli and other types of high-dimensional data (Tenenbaum et al., and Roweis and Saul).  相似文献   
65.
An alternative strategy to reduce the percolation threshold of carbon black (CB) in polymer blends was investigated using random copolymer ternary blends of polystyrene (PS), poly(methyl methacrylate) (PMMA), and a styrene-methyl methacrylate random copolymer (SMMA). The target morphology was to selectively locate CB particles in the encapsulating layer of SMMA during melt mixing. The CB used in this study is BP-2000 from Cabot and has a strong selective affinity to PS. Even when the CB was premixed with SMMA, it moves to the PS phase during the melt mixing. However, we also observed the CB particles located at the interface between SMMA and PS phases. Through this study it is found that the interaction between polymers and CB particles is critical for selectively localizing CB particles in multi-component polymer blends. Although appropriate processing condition may retard the movement of CB particles to the polymer phase with affinity, it cannot prevent it completely and locate them to the SMMA phase, which is not thermodynamically favored. To locate CB particles in an encapsulating layer of ternary polymer blends, first of all, polymers forming it should have selective affinity to CB.  相似文献   
66.
Pitch precursors were synthesized from coal tar(CT) and pyrolysis fuel oil(PFO, petroleum residue oil) at relatively low temperature of 250°C, in the presence of borontrifluoride/diethyletherate complex(BFDE) as a catalyst and nitrobenzene(NB) as a co-catalyst. The softening point, nitrogen content and carbon yield increased with an increase of concentration of NB. The pitch precursors with good spinnability were prepared by removing the volatile components through N2 blowing. The precursor pitches were spun through a circular nozzle, stabilized at 310°C and finally carbonized at 1000°C. The optically anisotropic structure formed at the absence of NB was changed into isotropic structure, showing a decrease in size of the flow domain. The hollow carbon fiber could be prepared in the process of stabilization. The results proposed that the morphology of carbon materials could be controlled by changing the concentration of catalyst and/or co-catalyst and/or stabilization condition that affect on the mobility of molecules during carbonization.  相似文献   
67.
This study was carried out to investigate the growth performance, carcass yield and meat quality of large-type Korean native ducks (KND). A total of 420 day-old ducklings were divided into four treatments (seven replicates/treatment, 15 birds/replicate) by strains (A and B) and gender (male and female) in a 2 × 2 factorial arrangement under complete randomized design. The body weight (BW) of female KND was higher at week 2 and for male it was higher in week 8 (P 〈 0.05). BW gain, feed intake and feed conversion ratio of male KND were higher than those of female KND (P 〈 0.05) during week 0 to week 8. The carcass yield of both strains increased from 6 weeks to 8 weeks (P 〈 0.05). The breast meat ratio was the highest at week 8 whereas the leg meat ratio was the highest at 6 weeks of age in both strains (P 〈 0.01). Lightness (L*), yellowness (b*) and juiciness of meat were the highest at 6 weeks (P 〈 0.05). Moisture, ash and fat contents of meat were the highest at 7 weeks (P 〈 0.05) and protein content was the highest at 8 weeks (P 〈 0.01). These results may provide the basic data on growth performance and meat quality of large-type KND, which can be used for genetic improvements and rearing at commercial scale.  相似文献   
68.
The present study was undertaken to compare the effect of salinomycin and Bacillus subtilis on growth performance, serum antibody levels against Clostridium spp. and Eimeria spp., and cytokine mRNA expression levels in broiler chickens raised in the used litter. Broiler chickens fed a diet containing salinomycin showed lower (P < 0.05) body weights compared with the control diet-fed counterparts. Serum nitric oxide levels were significantly (P < 0.05) elevated in chickens fed the B. subtilis-enriched diet compared with those on either the salinomycin-fed or control diet-fed chickens. None of the dietary treatments affected (P > 0.05) serum antibody levels against Clostridium perfringens toxins. Both salinomycin and B.subtilis significantly lowered (P < 0.05) the serum levels of Eimeria-specific antibodies compared with the control group. Salinomycin, but not B. subtilis, significantly modulated (P < 0.05) the expression of cytokines encoding interferon-γ (IFN-γ), interleukin10 (IL-10) and tumor necrosis factor superfamily 15 (TNFSF15) compared with the control group. In conclusion, dietary salinomycin and B. subtilis affected serum anticoccidial antibody and intestinal cytokine expression, but failed to improve growth performance in broiler chickens. Further study is warranted to investigate the mode of action of salinomycin on host immune response and growth performance in broiler chickens.  相似文献   
69.
The net energy (NE) content of canola meals (CM; i.e. Brassica napus yellow and Brassica juncea yellow) in growing pigs was determined using an indirect calorimetry chamber or published prediction equations. The study was conducted as a completely randomized design (n = 6), with (i) a basal diet and (ii) 2 diets containing 700 g/kg of the basal diet and 300 g/kg of either of the two varieties of CM. A total of 18 growing barrows were housed in metabolism crates for the determination of digestible (DE) and metabolizable (ME) energy. Thereafter, pigs were transferred to the indirect calorimetry chamber to determine heat production (HP). The NE contents of diets containing Brassica napus yellow and Brassica juncea yellow determined with the direct determination technique and prediction equations were 9.8 versus 10.3 MJ/kg dry matter (DM) and 10.2 versus 10.4 MJ/kg DM, respectively. Retained energy (RE) and fasting heat production (FHP) of diets containing Brassica napus yellow and Brassica juncea yellow were 5.5 versus 5.7 MJ/kg and 4.3 versus 4.5 MJ/kg, respectively, when measured with the direct determination technique and prediction equations. The NE contents of Brassica napus yellow and Brassica juncea yellow were determined to be 8.8 and 9.8 MJ/kg DM, respectively, using the direct determination technique.  相似文献   
70.
This study was aimed to evaluate the effect of dietary supplementation of lipid‐encapsulated (coated) zinc oxide ZnO on post‐weaning diarrhea (colibacillosis) in weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC). Thirty‐two 35‐day‐old weaned piglets were orally challenged with 3 × 1010 colony forming units of ETEC K88 while eight piglets received no challenge (control). Each eight challenged piglets received a diet containing 100 ppm ZnO (low ZnO), 2500 ppm ZnO (high ZnO) or 100 ppm of lipid (10%)‐coated ZnO (coated ZnO) for 7 days; control pigs received the low ZnO diet. Daily gain, goblet cell density in the villi of the duodenum, jejunum and ileum, and villus height in the jejunum and ileum, which decreased due to the challenge, were equally greater in the coated ZnO and high ZnO groups versus low ZnO group. Fecal consistency score, serum interleukin‐8 concentration, subjective score of fecal E. coli shedding, and digesta pH in the stomach, jejunum and ileum, which increased due to the challenge, were equally low in the coated ZnO and high ZnO groups versus low ZnO. Results suggest that a low level of coated ZnO might well substitute for a pharmacological level of native ZnO in dietary supplementation to alleviate colibacillosis of weaned piglets.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号