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   343篇
  免费   25篇
林业   27篇
农学   12篇
  68篇
综合类   14篇
农作物   28篇
水产渔业   46篇
畜牧兽医   139篇
园艺   8篇
植物保护   26篇
  2023年   7篇
  2022年   13篇
  2021年   29篇
  2020年   24篇
  2019年   24篇
  2018年   24篇
  2017年   21篇
  2016年   13篇
  2015年   16篇
  2014年   11篇
  2013年   23篇
  2012年   20篇
  2011年   23篇
  2010年   11篇
  2009年   8篇
  2008年   17篇
  2007年   16篇
  2006年   17篇
  2005年   8篇
  2004年   9篇
  2003年   9篇
  2002年   9篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1996年   3篇
  1994年   1篇
  1989年   1篇
  1986年   1篇
  1977年   1篇
排序方式: 共有368条查询结果,搜索用时 15 毫秒
341.
342.
Nitrification inhibitors can effectively decrease nitrification rates and nitrous oxide(N2O)emission while increasing crop yield under certain conditions.However,there is no information available on the effects of nitrification inhibitors and tillage practices on N2O emissions from maize cropping in Iran.To study how tillage practices and nitrapyrin(a nitrification inhibitor)affect N2O emission,a split factorial experiment using a completely randomized block design with three replications was carried out in Northeast Iran,which has a cold semiarid climate.Two main plots were created with conventional tillage and minimum tillage levels,and two nitrogen(N)fertilizer(urea)management systems(with and without nitrapyrin application)were created as subplots.Tillage level did not have any significant effect on soil ammonium(NH4+)and nitrate(NO3-)concentrations,cumulative amount and yield-scaled N2O emission,and aboveground biomass of maize,whereas nitrapyrin application showed significant effect.Nitrapyrin application significantly reduced the cumulative amount of N2O emission by 41%and 32%in conventional tillage and minimum tillage practices,respectively.A reduction in soil NO3-concentration by nitrapyrin was also observed.The average yield-scaled N2O emission was 13.6 g N2O-N kg-1N uptake in both tillage systems without nitrapyrin application and was significantly reduced to 7.9 and 8.2 g N2O-N kg-1N uptake upon the application of nitrapyrin in minimum tillage and conventional tillage practices,respectively.Additionally,nitrapyrin application increased maize biomass yield by 4%and 13%in the minimum tillage and conventional tillage systems,respectively.Our results indicate that nitrapyrin has a potential role in reducing N2O emission from agricultural systems where urea fertilizers are broadcasted,which is common in Iran due to the practice of traditional farming.  相似文献   
343.
Predicting and mapping productivity areas allows crop producers to improve their planning of agricultural activities. The primary aims of this work were the identification and mapping of specific management areas allowing coffee bean quality to be predicted from soil attributes and their relationships to relief. The study area was located in the Southeast of the Minas Gerais state, Brazil. A grid containing a total of 145 uniformly spaced nodes 50 m apart was established over an area of 31.7 ha from which samples were collected at depths of 0.00–0.20 m in order to determine physical and chemical attributes of the soil. These data were analysed in conjunction with plant attributes including production, proportion of beans retained by different sieves and drink quality. The results of principal component analysis (PCA) in combination with geostatistical data showed the attributes clay content and available iron to be the best choices for identifying four crop production environments. Environment A, which exhibited high clay and available iron contents, and low pH and base saturation, was that providing the highest yield (30.4l ha?1) and best coffee beverage quality (61 sacks ha?1). Based on the results, we believe that multivariate analysis, geostatistics and the soil–relief relationships contained in the digital elevation model (DEM) can be effectively used in combination for the hybrid mapping of areas of varying suitability for coffee production.  相似文献   
344.
Increased levels of stress hormones in the muscle could lead to post mortem metabolic/structural modiifcations that could be relfected on meat quality. The present study investigated the metabolic effect of either adrenaline or cortisol injected into lambs in order to obtain an animal model of acute stress. Results showed that adrenaline or cortisol injection lead to glucose metabolism and muscle temperature increase. Muscle pH immediately post mortem was affected by adrenaline treatment. Water holding capacity (WHC) of fresh muscle, ifnal muscle pH and temperature registered at 24 h post mortem were not affected by injected hormones. Hardness and adhesiveness of LD muscle evaluated 3 d post mortem tended to increase as a result of adrenaline or cortisol injection. Results demonstrated that injected hormones were able to affect the post mortem muscle biochemistry and the pH/T curve independently of ifnal muscle pH.  相似文献   
345.
Embryology belongs to the basic sciences and is usually an integral part of the anatomy. The subject is traditionally taught by visual inspection of embryonic tissue slides stained with Haematoxylin and Eosin (H&E) to expose the dynamics of tissue histology as development proceeds. While combining in situ hybridization for gene expression analysis and immunostaining for protein expression analysis is an established technique for embryology research, the implementation of this tool in embryology teaching has not been described. The present study was conducted to assess the use of an online multi-colour gene expression analysis technique, alongside histological sections and diagrams, to improve students' understanding of embryology. The participants of this study were bachelor's students of Veterinary Medicine at the University of Khartoum. The method was also evaluated by distributing questionnaire items to Veterinary students via Google forms; subsequently, their responses were analysed qualitatively. The majority of students stated that the new technique was beneficial for their learning of embryology. The multi-colour images proved a more effective means for learning embryology than the traditional H&E image. Results from the students strengthen the belief in applying the multi-colour technique for better embryology course learning.  相似文献   
346.
347.
Homozygous deletion of the survival motor neuron 1 gene (SMN1) causes spinal muscular atrophy (SMA), the most frequent genetic cause of early childhood lethality. In rare instances, however, individuals are asymptomatic despite carrying the same SMN1 mutations as their affected siblings, thereby suggesting the influence of modifier genes. We discovered that unaffected SMN1-deleted females exhibit significantly higher expression of plastin 3 (PLS3) than their SMA-affected counterparts. We demonstrated that PLS3 is important for axonogenesis through increasing the F-actin level. Overexpression of PLS3 rescued the axon length and outgrowth defects associated with SMN down-regulation in motor neurons of SMA mouse embryos and in zebrafish. Our study suggests that defects in axonogenesis are the major cause of SMA, thereby opening new therapeutic options for SMA and similar neuromuscular diseases.  相似文献   
348.
Tropical Animal Health and Production - This study aimed to estimate the genetic parameters for somatic cell count (SCC) and the genetic association between SCC and milk production traits using two...  相似文献   
349.
Tropical Animal Health and Production - This study aimed to estimate the genetic parameters of milk (305-day milk yield (MY305)), growth (weaning weight (WW), yearling weight (YW), and weight at...  相似文献   
350.
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