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   7798篇
  免费   591篇
  国内免费   536篇
林业   652篇
农学   572篇
基础科学   375篇
  1278篇
综合类   3701篇
农作物   301篇
水产渔业   471篇
畜牧兽医   993篇
园艺   243篇
植物保护   339篇
  2024年   27篇
  2023年   200篇
  2022年   323篇
  2021年   307篇
  2020年   357篇
  2019年   354篇
  2018年   230篇
  2017年   339篇
  2016年   442篇
  2015年   463篇
  2014年   521篇
  2013年   500篇
  2012年   634篇
  2011年   634篇
  2010年   472篇
  2009年   459篇
  2008年   404篇
  2007年   441篇
  2006年   323篇
  2005年   286篇
  2004年   210篇
  2003年   174篇
  2002年   127篇
  2001年   105篇
  2000年   84篇
  1999年   78篇
  1998年   59篇
  1997年   62篇
  1996年   51篇
  1995年   55篇
  1994年   42篇
  1993年   37篇
  1992年   20篇
  1991年   30篇
  1990年   17篇
  1989年   15篇
  1988年   13篇
  1987年   9篇
  1986年   4篇
  1985年   5篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1956年   2篇
排序方式: 共有8925条查询结果,搜索用时 21 毫秒
61.
李晨阳  蒙凤群 《植物保护》2023,49(4):108-114
了解我国松毛虫发生的空间分布格局及其驱动因子, 对松毛虫暴发的预防?控制和治理具有重要意义?本研究基于我国各行政区2004年-2012年间每年松毛虫发生面积及其寄主植物面积, 使用一般线性模型分析气候因子是否以及如何驱动我国松毛虫发生的空间分布格局?结果表明:在全国尺度上, 最暖季降水量是松毛虫发生的主要气候驱动因子, 松毛虫平均发生率与最暖季降水量显著正相关?在最暖季降水量的作用下, 我国松毛虫的发生呈现明显的空间分布格局, 最暖季降水量较高的南方和北方部分地区松毛虫发生率较高, 而降水量较低的西北和青藏地区松毛虫发生率较低?我们的研究结果可为松毛虫暴发的预防和管理工作提供指导?  相似文献   
62.
联合国粮食及农业组织2018年向全球发布草地贪夜蛾Spodoptera frugiperda是重要的预警害虫。据报道,2019年我国已有26个省(区、市)的作物受到草地贪夜蛾为害。目前已经发现草地贪夜蛾幼虫对某些化学农药产生抗性的现象,为缓解其抗药性产生,具有主动寻找寄主害虫的昆虫病原线虫为草地贪夜蛾的生物防治提供了应用潜能。该文从昆虫病原线虫高效侵染种(品系)及其浓度、共生菌、草地贪夜蛾幼虫易感龄期、田间致死力及影响防控效果的因素等方面进行综述,以期为田间有效利用昆虫病原线虫防治草地贪夜蛾提供参考。  相似文献   
63.
饲料因素对鸡蛋风味的影响及其改善措施   总被引:1,自引:0,他引:1  
随着畜牧业的快速发展,畜产品供应日益充裕,人们对畜产品的质量要求不断提高,其安全性、营养性及风味等逐渐成为消费者关注的热点。本文综述了形成鸡蛋风味的前体物质、影响鸡蛋风味的饲料因素及改善鸡蛋风味的措施,旨在为相关研究提供参考。  相似文献   
64.
The veterinary profession is experiencing a shortage of veterinarians, with attrition recognised as a substantial contributor. Research has also indicated increased levels of mental ill health and alarming suicide rates in practitioners. The primary aim of this study was to investigate the impact of eleven modifiable workplace factors on mental health outcomes, job appreciation and intention to leave the veterinary profession. The second aim was to ascertain whether workplace factors influence mental health outcomes after controlling for individual resilience. An online survey was completed by 73 practising Australian veterinarians. Unfavourable workplace factors correlated with adverse outcomes including depression, stress, reduced job appreciation and increased likelihood of leaving both the role and the profession. Workplace factors remained linked with the outcomes of job appreciation, depression and stress whilst controlling for practitioner resilience. Job appreciation was a significant predictor of intention to leave both the current role and the profession. Via multiple linear regression, two categories were identified as associated with improved psychological outcomes and job appreciation. These were workplace factors that represent breaks from workload and control or decision latitude in the workplace. Whilst resilience represents a key area for intervention, workplace factors potentially represent an easier-to-modify area for intervention.  相似文献   
65.
Surveillance of hepatitis E virus (HEV) in risk groups is an important strategy to monitor its circulation pattern and to timely detect changes thereof. The aims of this cross-sectional study were to estimate the prevalence of HEV infections in pigs and humans from different regions of the country, to identify risk factors for increasing anti-HEV IgG prevalence and to characterize HEV strains. The presence of anti-HEV antibodies was assessed by commercial ELISA in serum samples from the general population, farm and slaughterhouse employees, as well as pigs sampled in the three regions of Cuba from February to September 2016. Overall, individuals with occupational exposure to swine or swine products (70/248, 28.2%) were 4 times more likely to be seropositive compared to the general population (25/285, 8.7%; OR: 4.18; p < .001). Within the risk group, risk factors included age, number of years working in a professional activity with direct exposure to swine, geographic region and distance between residence and closest professional swine setting, while wearing gloves had a protective effect. Prevalence of total anti-HEV antibodies in swine was 88.2% (165/187) and HEV RNA was detected by real-time RT-PCR in 9.2% (16/173) swine stools. All HEV strains sequenced clustered within genotype 3. Some strains clearly belonged to subtype 3a, while another group of strains was related with subtypes 3b and 3 k but partial HEV sequences did not allow unequivocal subtype assignment. These findings suggest that the high HEV exposure in Cuban individuals with swine-related occupations could be due to enzootic HEV in certain regions, direct contact with infectious animals or their products as well as environmental contamination.  相似文献   
66.
67.
The aim of the present study was to evaluate the expression and localization of lymphangiogenic factors (VEGF-C and VEGF-D), their receptor (VEGFR3) and lymphatic endothelial marker (LYVE1) in buffalo placenta during early pregnancy [EP], and to investigate the functional role of lymphangiogenic growth factors in placental lymphangiogenesis. The mRNA and protein expression of VEGF-C, VEGF-D, their receptor VEGFR3 and LYVE1 showed significant expression in EP1 (29–42 days) and EP2 stages (51–82 days) both in caruncle (maternal part) and cotyledon (foetal part) of the buffalo placenta. Immunoreactivity of VEGF-C, VEGF-D and LYVE1 was observed around the endometrial gland, in lymphatics and trophoblast cells, whereas VEGFR3 mainly localized in lymphatics of the caruncle and cotyledons. Cultured trophoblast cells were treated with VEGF-C/VEGF-D (50, 100 and 150 ng/ml) and combined doses of VEGF-C and VEGF-D (150 ng/ml) each for different time durations (24, 48 and 72 h). The mRNA expression of LYVE1 and PCNA was significantly (p < .001) upregulated with VEGF-C and VEGF-D and combined treatment (@150 ng/ml), as well as significantly downregulating Caspase-3 at 48 and 72 h. Thus, the present study provides evidence that lymphangiogenic factors are expressed in buffalo placental compartments and they may play a significant role in the regulation of placental function in water buffaloes.  相似文献   
68.
69.
70.
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