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   2949篇
  免费   198篇
  国内免费   4篇
林业   198篇
农学   71篇
基础科学   23篇
  491篇
综合类   713篇
农作物   68篇
水产渔业   242篇
畜牧兽医   1039篇
园艺   90篇
植物保护   216篇
  2024年   8篇
  2023年   21篇
  2022年   31篇
  2021年   71篇
  2020年   77篇
  2019年   91篇
  2018年   80篇
  2017年   80篇
  2016年   89篇
  2015年   70篇
  2014年   79篇
  2013年   108篇
  2012年   192篇
  2011年   225篇
  2010年   148篇
  2009年   97篇
  2008年   224篇
  2007年   214篇
  2006年   198篇
  2005年   191篇
  2004年   195篇
  2003年   185篇
  2002年   180篇
  2001年   33篇
  2000年   24篇
  1999年   29篇
  1998年   16篇
  1997年   7篇
  1996年   18篇
  1995年   15篇
  1994年   12篇
  1993年   9篇
  1992年   6篇
  1991年   11篇
  1990年   6篇
  1989年   12篇
  1988年   6篇
  1987年   11篇
  1986年   8篇
  1985年   8篇
  1984年   4篇
  1983年   3篇
  1982年   5篇
  1981年   3篇
  1980年   6篇
  1977年   3篇
  1976年   5篇
  1974年   9篇
  1973年   4篇
  1970年   3篇
排序方式: 共有3151条查询结果,搜索用时 46 毫秒
131.
With an apparent increase of harmful algal blooms (HABs) worldwide, healthcare providers, public health personnel and coastal managers are struggling to provide scientifically-based appropriately-targeted HAB outreach and education. Since 1998, the Florida Poison Information Center-Miami, with its 24 hour/365 day/year free Aquatic Toxins Hotline (1–888–232–8635) available in several languages, has received over 25,000 HAB-related calls. As part of HAB surveillance, all possible cases of HAB-related illness among callers are reported to the Florida Health Department. This pilot study evaluated an automated call processing menu system that allows callers to access bilingual HAB information, and to speak directly with a trained Poison Information Specialist. The majority (68%) of callers reported satisfaction with the information, and many provided specific suggestions for improvement. This pilot study, the first known evaluation of use and satisfaction with HAB educational outreach materials, demonstrated that the automated system provided useful HAB-related information for the majority of callers, and decreased the routine informational call workload for the Poison Information Specialists, allowing them to focus on callers needing immediate assistance and their healthcare providers. These results will lead to improvement of this valuable HAB outreach, education and surveillance tool. Formal evaluation is recommended for future HAB outreach and educational materials.  相似文献   
132.
A headspace sorptive extraction (HSSE) in combination with thermal desorption gas chromatography-mass spectrometry (TD-GC-MS) method for the analysis of volatile components (alcohols, esters, carbonyls, acids, phenols and lactones) in wine samples was developed. Extraction conditions such as salting-out effects, sorption time, stirring speed, phase ratio, extraction temperature, and effect of pH were thoroughly evaluated as part of method validation. The method was very sensitive with LODs and LOQs between 50 pg/L to 299 microg/L and 0.2 ng/L to 0.996 microg/L, respectively. Repeatability for all the compounds was between 3 and 22%. The intermediate repeatability was obtained within the acceptable range. Out of 39 volatile compounds selected, 37 were detected and quantitated. The method was found to be simple, cost-effective, sensitive, and use a small sample volume. The method was successfully applied for the routine analysis of 79 young red and white wine samples from various South African districts.  相似文献   
133.
134.
Desneux  Nicolas  Han  Peng  Mansour  Ramzi  Arn&#;  Judit  Br&#;vault  Thierry  Campos  Mateus R.  Chailleux  Anais  Guedes  Raul N. C.  Karimi  Javad  Konan  Kouassi Arthur J.  Lavoir  Anne-violette  Luna  Mar&#;a G.  Perez-Hedo  Meritxell  Urbaneja  Alberto  Verheggen  Fran&#;ois J.  Zappal&#;  Lucia  Abbes  Khaled  Ali  Abid  Bayram  Yunus  Cantor  Fernando  Cuthbertson  Andrew G. S.  De Vis  Raf  Erler  Fedai  Firake  Dnyaneshwar M.  Haddi  Khalid  Hajjar  M. Jamal  Ismoilov  Khasan  Jaworski  Coline C.  Kenis  Marc  Liu  Hao-tian  Madadi  Hossein  Martin  Thibaud  Mazih  Ahmed  J. Messelink  Gerben  Mohamed  Samira A.  Nofemela  Robert S.  Oke  Abiola  Ramos  C&#;sar  Ricupero  Michele  Roditakis  Emmanouil  Shashank  Pathour R.  Wan  Fang-Hao  Wang  Ming-hui  Wang  Su  Zhang  Yi-Bo  Biondi  Antonio 《Journal of pest science》2022,95(1):17-39
Journal of Pest Science - The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), has invaded most Afro-Eurasian countries and is threatening worldwide tomato...  相似文献   
135.
Agroforestry Systems - Tropical agroforestry practices play a crucial role in mitigating global climate change by absorbing CO2 from the atmosphere through photosynthesis and storing carbon in...  相似文献   
136.
Journal of Pest Science - The South American tomato pinworm, Tuta absoluta, (SATP) is now a devastating pest worldwide of crops in the family Solanaceae. Most prior studies of SATP’s thermal...  相似文献   
137.
This study investigated the overwintering survival and infectivity of free-living gastrointestinal nematode (GIN) stages on pasture. The presence of GIN larvae was assessed on 3 sheep farms in Ontario with a reported history of clinical haemonchosis, by collecting monthly pasture samples over the winter months of 2009/2010. The infectivity of GIN larvae on spring pastures was evaluated using 16 tracer lambs. Air and soil temperature and moisture were recorded hourly. Free-living stages of Trichostrongylus spp. and Nematodirus spp. were isolated from herbage samples. Gastrointestinal nematodes were recovered from all tracer lambs on all farms; Teladorsagia sp. was the predominant species. Very low levels of Haemonchus contortus were recovered from 1 animal on 1 farm. The results suggest that Haemonchus larvae do not survive well on pasture, while Teladorsagia sp., Trichostrongylus spp. and Nematodirus spp. are able to overwinter on pasture in Ontario and are still infective for sheep in the spring.  相似文献   
138.
Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are retroviruses found within domestic and wild cat populations. These viruses cause severe illnesses that eventually lead to death. Housing cats communally for long periods of time makes shelters at high risk for virus transmission among cats. We tested 548 cats from 5 different sites across the island of Newfoundland for FIV and FeLV. The overall seroprevalence was 2.2% and 6.2% for FIV and FeLV, respectively. Two sites had significantly higher seroprevalence of FeLV infection than the other 3 sites. Analysis of sequences from the FeLV env gene (envelope gene) from 6 positive cats showed that 4 fell within the FeLV subtype-A, while 2 sequences were most closely related to FeLV subtype-B and endogenous feline leukemia virus (en FeLV). Varying seroprevalence and the variation in sequences at different sites demonstrate that some shelters are at greater risk of FeLV infections and recombination can occur at sites of high seroprevalence.  相似文献   
139.
140.
Abstract Using underwater cameras, data were collected on the feeding behaviour and swimming speeds of Atlantic salmon Salmo salar L., gilthead sea bream Sparus aurata L. and European sea bass Dicentrarchus labrax L. in sea cages. Comparisons were made between the behaviours of fish fed on demand using interactive feedback systems and those of fish fed under the standard feeding practice of each farm (control). In all three species, swimming speeds were similar before feeding , but they were significantly higher in the control regimes during feeding. When fed on demand, sea bass had reduced swimming speed just before and during feeding compared with that observed during the non‐feeding periods. Higher proportions of feeding fish were observed in the control regime cages than in fish fed on demand for all three species, indicating a greater feeding intensity during meals in the control regimes. This was further supported by observations of an increase in the density of sea bass in the upper water in the control cages during feeding. The results suggest decreased levels of competition between the on demand‐fed fish during feeding, which might be hypothesized to lead to improved growth and production efficiency in aquaculture.  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