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   426篇
  免费   14篇
  国内免费   1篇
林业   24篇
农学   15篇
基础科学   6篇
  71篇
综合类   7篇
农作物   46篇
水产渔业   60篇
畜牧兽医   171篇
园艺   11篇
植物保护   30篇
  2023年   5篇
  2022年   20篇
  2021年   23篇
  2020年   27篇
  2019年   31篇
  2018年   22篇
  2017年   20篇
  2016年   17篇
  2015年   11篇
  2014年   13篇
  2013年   24篇
  2012年   27篇
  2011年   23篇
  2010年   13篇
  2009年   13篇
  2008年   10篇
  2007年   15篇
  2006年   17篇
  2005年   6篇
  2004年   10篇
  2003年   7篇
  2002年   13篇
  2001年   3篇
  2000年   2篇
  1999年   3篇
  1997年   3篇
  1996年   3篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   2篇
  1989年   4篇
  1986年   3篇
  1983年   2篇
  1982年   2篇
  1981年   3篇
  1980年   1篇
  1979年   3篇
  1978年   3篇
  1977年   3篇
  1976年   4篇
  1975年   1篇
  1974年   3篇
  1973年   1篇
  1970年   3篇
  1969年   2篇
  1968年   1篇
  1967年   3篇
  1966年   2篇
  1965年   1篇
排序方式: 共有441条查询结果,搜索用时 15 毫秒
21.
In this work, we report for the first time on the analysis of genetic diversity within a set of 36 Tunisian Opuntia ficus indica (L.) Mill. ecotypes using RAPD markers.  相似文献   
22.
Veterinary Research Communications - This study evaluated the diuretic, antioxidant, anti-inflammatory, and immunological effects of a commercial diuretic (CD) (composed of ammonium chloride,...  相似文献   
23.
Field applications usingBacillus thuringiensis (Dipel 2 X) againstSpodoptera exigua infesting corn and sunflower cultivations were carried out in two different localities in Egypt. The percentage of infested corn plants decreased to 2.5%, seven days after treatment with Dipel 2x, (250 g/fed) and the yield was significantly increased compared with untreated plots. The carbamate insecticide (Lannate) at 300 g/fed caused complete kill to the larvae and the highest yield was obtained. Application of Lannate, Dipel (250 g) or a combination of both (150 g/each/fed) caused a high reduction of the larvae existing in sunflower after seven days from application, while Dipel at 200 g/fed gave a lower effect. Ten days after application, the number of larvae and infested plants increased significantly in plots treated with Lannate alone, while plots treated with either Dipel (250 g) or Dipel combined with Lannate (150 g/each) still maintained a lower infestation. The estimated yield showed the highest increase in plots treated with Lannate followed by Dipel (250 g) and then a combination of both.  相似文献   
24.
In addition to luteolin and its 7-methyl ether, the CH2Cl2-MeOH (1:1) extract of Cyperus conglomeratus afforded two new prenylflavans identified as 7,3'-dihydroxy-5,5'-dimethoxy-8-prenylflavan and 5,7,3'-trihydroxy-5'-methoxy-8-prenylflavan. The structures were established by CIMS, 1H-NMR, 13C-NMR, H-H COSY, HMQC, HMBC and DEPT analysis.  相似文献   
25.
26.
The present study evaluates the effects of embryonic age and proteolytic enzymes on the isolation and primary culture of chicken enterocyte and to establish an effective technique for chicken intestinal epithelial cell (IEC) cultivation. Fourteen‐day‐old, 16‐day‐old and 18‐day‐old embryos (average weight: 52.23 ± 0.76 g, 50.86 ± 0.99 g, 48.98 ± 1.03 g) were the source for preparation of enterocyte culture, and trypsin‐ethylene diamine tetraacetic acid, collagenase, thermolysin and combination of collagenase and thermolysin were used for digestion medium. Optimal culture protocols were determined by qualitative assays of proliferation. Cells isolated by using 14‐day‐old embryo and collagenase obtain the best attachment and growth in culture, and the production of continuously growing IEC cultures. Thus, we conclude that the use of collagenase as a dissociating enzyme and 14‐day‐old embryo as a source can be advantageously applied to the isolation of chicken IEC and this method may be useful for various applications and basic studies of the intestinal tract concerning such objects as physiology, immunology and toxicology.  相似文献   
27.
Zhang  Yurou  Wu  Zhenchao  Yu  Mengnan  Zhang  Dongming  Wang  Qiuju  Lin  Lili  Wang  Guiqin  Elsadek  Mahmoud M.  Yao  Qi  Chen  Yuke  Guo  Zhixin 《Aquaculture International》2022,30(2):747-772

Probiotics have been widely used in aquaculture worldwide especially in China as antibiotics have been banned in aquaculture. In the present study, 27 potential strains were isolated from Rhynchocypris lagowskii Dybowski intestinal tract towards the assessment of their probiotic potential. Two potential probiotics were finally screened from the 27 candidate strains according to the results of enzyme-producing ability, in vitro against pathogens ability and antibiotic sensitivity test. The 2 potential probiotics were identified and confirmed on the basis of their colony morphology, biochemical characteristics, and 16S rRNA sequencing. The probiotic strains, LSG2-3–2 and LSG3-6, were identified to be Bacillus methylotrophicus and B. tequilensis, respectively. Further studies showed that LSG2-3–2 and LSG3-6 had excellent tolerance to high temperature (80℃), low pH (3–5), bile salts (0.3%), intestinal juice (10%), and gastric juice (0.5%). The adhesion rates of LSG2-3–2 and LSG3-6 in the in vitro intestinal mucosal adhesion model were 17.74% and 24.04%, respectively. Analysis of their bacteria surface adhesive proteins revealed that the lectins on the bacterial surface of LSG2-3–2 and LSG3-6 were mainly protein and glycoprotein properties, respectively. The adhesion receptor components in the mucus proteins of the two strains were all protein properties. The results of the inhibitory adhesion test indicated that LSG3-6 had a higher inhibitory effect on Aeromonas hydrophila and LSG2-3–2 had a better inhibitory effect on A. veronii. The biosafety assay confirmed that the isolates were not pathogenic to the host fish. Based on the presently observed characteristic features, it can be concluded that LSG2-3–2 (B. methylotrophicus) and LSG3-6 (B. tequilensis) retrieved from the digestive tract of R. lagowskii can be used for the healthy breeding and disease prevention of R. lagowskii.

  相似文献   
28.
Sesbania fiber is a fast-growing wood species that has been investigated for medium-density fiberboard (MDF) production. To assess the possibility of applying the local industrial defibration parameters of sugar-cane bagasse (SCB) on defibration of sesbania, the chemical constituents of unfibrated and defibrated sesbania, as well as their thermal stability and scanning electron micrographs, were estimated. Different preparation variables of MDF, such as density, level of urea-formaldehyde (UF) resin (with 0.19% free-formaldehyde [HCHO]), and pressing time were studied, in comparison with that produced by using SCB fibers. The results showed that most of the tested sesbania-based MDFs have mechanical properties that fulfill the minimum requirements of MDF ANSI standard. Additionally, applying 12% UF and pressing for 240 sec provided sesbania-based MDF with optimum reduction in thickness swelling (reached ~7%). It is important to note that the sesbania-based MDF produced under these conditions is characterized by a lower TS property, than that obtained from SCB, or that reported in standards. The preliminary feasibility study revealed that using sesbania fibers will be an added economical potential for MDF production.  相似文献   
29.
The karyotype and chromosomal characteristics of endangered Caspian salmon, Salmo trutta caspius, in the southern part of the Caspian Sea were investigated. From the total of 60 mitotic metaphases achieved from 15 individuals, 15, 9 and 36 metaphases were with the mode <76, 76 and 80 representing 25%, 15% and 60% of metaphases respectively. So, the most common pattern of chromosome number was 80 (36 metaphases, 60%) and the number of diploid chromosomes was thus confirmed as (2n=80) of this subspecies. The karyotype consists of seven metacentric, five submetacentric and 28 telocentric pairs. The karyological parameters of the Caspian salmon, the centromic index, arm ratio, relative length and length variation range of chromosomes, were 0–0.5, 1–∞, 0.011–0.045 and 0.507–2.028 μm respectively. The total length of chromosomes in haploid series was 44.776 μm and fundamental number of chromosome arms was 104. This study may provide the first knowledge on chromosome analysis in Caspian salmon and add basic information useful for its chromosomal manipulations.  相似文献   
30.
This research examined the haematological and immunological responses of quadruplicate groups of juvenile (~400 g initial weight) Atlantic salmon (Salmo salar L.) that had each been fed daily to satiation for 12 weeks one of three high‐energy extruded diets of identical composition except for the supplemental dietary lipid (234.7 g kg?1) source. The three experimental diets varied in the composition of supplement lipid; diet 1 contained 100% anchovy oil (AO), while diets 2 and 3 replaced 29.8% and 59.7% of the AO (respectively) with a 1:1 blend of canola oil (CO) and poultry fat (PF). Immediately following the feeding trial, a random sample of fish from each diet was sampled for determination of baseline levels of various haematological and immunological parameters. Thereafter, duplicate diet groups were vaccinated (against Listonella anguillarum) and reared on their respective experimental diets for an additional 4 weeks. At that time, the remaining fish were sampled similarly, and the different parameters were measured again. Comparisons between the different diet treatment groups were made before and after vaccination. There were no significant diet treatment effects at either sample time, for haematocrit, differential leucocyte counts, erythrocyte counts, serum hemolytic activity or head kidney leucocyte respiratory burst activity. The fish fed diet 1 however, did show significantly higher post‐vaccination levels of peripheral blood leucocyte respiratory burst activity and higher serum antibody titres against L. anguillarum. The results suggest that the relatively low n‐6/n‐3 fatty acid ratios in the muscle and presumably other tissues of fish fed diet 1, may have resulted in a reduced production of immunocompromising eicosanoids than were produced in fish ingesting the other two diets that were based in part on the different amounts of the CO and PF blend. Long‐term studies are required to confirm this possibility.  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