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   1739篇
  免费   98篇
  国内免费   3篇
林业   130篇
农学   62篇
基础科学   4篇
  460篇
综合类   123篇
农作物   108篇
水产渔业   93篇
畜牧兽医   697篇
园艺   48篇
植物保护   115篇
  2023年   27篇
  2022年   25篇
  2021年   79篇
  2020年   83篇
  2019年   94篇
  2018年   75篇
  2017年   62篇
  2016年   72篇
  2015年   58篇
  2014年   64篇
  2013年   116篇
  2012年   139篇
  2011年   149篇
  2010年   84篇
  2009年   53篇
  2008年   114篇
  2007年   104篇
  2006年   93篇
  2005年   77篇
  2004年   61篇
  2003年   48篇
  2002年   41篇
  2001年   14篇
  2000年   8篇
  1999年   11篇
  1998年   4篇
  1997年   4篇
  1996年   7篇
  1995年   5篇
  1994年   6篇
  1993年   6篇
  1992年   4篇
  1991年   3篇
  1990年   7篇
  1989年   2篇
  1986年   4篇
  1985年   6篇
  1984年   4篇
  1983年   4篇
  1982年   2篇
  1980年   3篇
  1977年   2篇
  1973年   2篇
  1972年   2篇
  1968年   1篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
  1958年   1篇
  1955年   1篇
排序方式: 共有1840条查询结果,搜索用时 15 毫秒
41.
Completion of a thorough neurological examination of a rabbit is essential for clinicians to determine the location of a neurological problem. Determination of the location of a lesion (whether solitary or multifocal/diffuse) enables a clinician to list the most likely causes of the problem. This article presents the neurological examination of the rabbit, followed by a practical guide to lesion localization in this species.  相似文献   
42.
The typical technologies used in veterinary hematology and biochemical analyzers are reviewed, along with associated advantages and disadvantages. Guidelines for implementing a successful in-clinic laboratory are provided, including criteria for system evaluation and expectations for comparative performance evaluations. The more common problems and limitations associated with in-clinic laboratory diagnostics and how to best prevent them are also discussed.  相似文献   
43.
Verticillium longisporum is a soil-borne fungal pathogen causing vascular wilt of Brassica crops. This study was conducted to enhance our knowledge on the host range of V. longisporum. Seven crop species (barley, oat, oilseed rape, pea, red clover, sugar beet and wheat) and five weed species (barren brome, black-grass, charlock, cleavers and scentless mayweed) all common in southern Sweden were evaluated for infection by response to V. longisporum. Oat, spring wheat, oilseed rape, scentless mayweed and charlock inoculated with V. longisporum in a greenhouse showed stunting to various degrees close to the fully ripe stage. Based on the extent of microsclerotia formation, explants were separated into four groups: for pea and wheat, <5% of the samples had formed microsclerotia; for scentless mayweed, 5–10%; for oat, 10–20%; and for charlock and oilseed rape >80%. The results suggest that plant species outside the Brassicaceae can act as reservoirs of V. longisporum inoculum. Soil inoculum densities in nine fields were monitored over a period of 12 months, which ranged from 1 to 48 cfu g−1 soil. Density of microsclerotia was lowest just after harvest, reaching its maximum six months later. No significant correlation between inoculum density in soil and disease incidence on oilseed rape plants was found. However, the data suggest that a threshold of 1 cfu g−1 soil is needed to cause disease on oilseed rape. Species identification based on microsclerotia morphology and PCR analysis showed that V. longisporum dominated in soil of seven, and V. dahliae in two of the nine fields studied.  相似文献   
44.
A 5-year-old Holstein cow, pregnant with a valuable calf, was presented with signs of heart failure (tachycardia, peripheral edema, and distended jugular veins) related to pericardial lymphoma and associated cardiac tamponade. In addition, pleural effusion was present in both hemithoraces. Medical treatment, which consisted of repeated pericardiocenteses, placement of indwelling pleural catheters, administration of intravenous fluid therapy, antibiotics and anti-inflammatory drugs, was ineffective in controlling recurrence of clinical signs despite a temporary improvement. A standing thoracoscopic pericardiotomy was performed in an attempt to reduce clinical signs of heart failure and to prolong life. Clinical signs of heart failure abated and no recurrence was seen. Standing thoracoscopic pericardiotomy along with possible corticosteroids can be recommended as palliative treatment in an effort to extend life for reproductive performance in genetically valuable animals.  相似文献   
45.
对鸵鸟进行早期的性别鉴定,可以确保期望的鸵鸟雌雄性别比例,雏鸟雌雄分群饲养,加快鸵鸟驯养进程,提高育雏成活率都有着重要意义。本研究采用翻肛法,对人工饲养的1~3月龄育雏期非洲鸵鸟进行试验与研究。结果表明,在1月龄时就可根据有无生殖交媾器及其形态、大小的差别进行雌雄鉴别,打破了通常认为鸵鸟在4月龄时才可以进行性别鉴定的传统做法,为非洲鸵鸟的饲养管理提供了有利的依据。  相似文献   
46.
Urban dwellers experience conflicting thoughts and feelings about urban woodlands; valued for their natural qualities, the relief they provide from the stress of modern urban living and the opportunities they afford for children's play and exploration. At the same time the seclusion inherent in this type of urban greenspace seems fraught with risk from crime, vandalism and abuse. Whilst many of these characteristics are well-researched, less is known about the differing perceptions of particular social groups. This study aimed to explore the ways in which age affects urban dwellers’ aspirations, values and fears concerning the woods, and woodland accessibility, focusing on the views of elderly people (aged over 65). This pilot study was based in Norfolk Heritage Park, an urban park containing a variety of woodland settings located in Sheffield, UK. The questionnaire survey (participantsn=97) revealed that although walking is the most popular leisure activity, most respondents did not visit urban parks as often as they would like, regardless of age. Whilst many of the meanings associated with urban woodland (“relaxation”, “peacefulness”, “seasonal change”, “scenery” and “education”) were shared amongst age groups, it seemed that the elderly respondents particularly valued the woods for their links with the past, and opportunities for immersion in the natural world. Some respondents from all age groups had fears about their personal security in the woodland, and the concerns of the elderly were heightened by their perceived frailty, reduced mobility and sense of vulnerability; this age group had a corresponding need for particular measures to alleviate these problems. The study provides preliminary evidence for the idea that adults of different ages have differing perceptions and requirements in relation to urban woodlands. Due to the small sample size and other methodological issues, further research is needed to confirm and develop the findings.  相似文献   
47.
Sequence comparisons and phylogenetic analysis of the 16S rRNA genes and the 16S/23S spacer regions of the phytoplasmas associated with Australian grapevine yellows, papaya dieback and Phormium yellow leaf diseases revealed minimal nucleotide differences between them resulting in the formation of a monophyletic group. Therefore, along with Australian grapevine yellows, the phytoplasmas associated with Phormium yellow leaf and papaya dieback should also be considered as Candidatus Phytoplasma australiense.  相似文献   
48.
Anna German 《Phytoparasitica》1985,13(3-4):209-213
A 5-minute contact of nursing mothers of the Levant vole,Microtus guentheri, with paper impregnated with a DES suspension in soybean oil (125 μg/cm2 ) caused sterilization of 60% of the newborn female offspring. A 1-hour contact was sufficient to sterilize more than 90% of them. When the DES concentration was decreased to 1 μg/cm2 only 44% of the newborn female offspring were sterile although their nursing mothers had been exposed to contact with the treated paper for a period of 2 hours. The concentration of 0.1 μg/cm2 was totally ineffective in causing sterilization. Treatment of nesting material with DES offers a promising means of reproductive suppression in Levant voles.  相似文献   
49.
Post-harvest apple treatment with 1-methylcyclopropene (1-MCP) was previously found to inhibit fruit ripening but also to inhibit the production of volatile compounds that contribute to apple flavor. The first objective of this study was to determine if consumers could distinguish 1-MCP treated and untreated Gala apples [Malus sylvestris L. (Mill.) var. domestica Borkh. Mansf.] following long-term storage. Chemical analysis showed 1-MCP treated fruit had reduced flavor volatiles compared to untreated fruit. Consumer difference tests showed they could distinguish between 1-MCP treated and untreated fruit. A second objective was to compare consumers’ acceptance for 1-MCP treated to untreated apples. Both 1-MCP treated and untreated apples received high overall liking scores that were not significantly different. Equal numbers of consumers indicated preference for 1-MCP treated and untreated fruit and there was no difference in purchase intent. However, subsets of consumers who eat Gala, Fuji or Red Delicious apples showed preference for untreated over 1-MCP treated fruit compared to consumers who do not eat these varieties.  相似文献   
50.
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