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   492篇
  免费   20篇
林业   5篇
农学   25篇
基础科学   2篇
  36篇
综合类   95篇
农作物   73篇
水产渔业   22篇
畜牧兽医   237篇
园艺   4篇
植物保护   13篇
  2021年   7篇
  2020年   5篇
  2018年   5篇
  2017年   13篇
  2016年   5篇
  2014年   10篇
  2013年   26篇
  2012年   19篇
  2011年   13篇
  2010年   7篇
  2009年   10篇
  2008年   15篇
  2007年   16篇
  2006年   15篇
  2005年   12篇
  2004年   11篇
  2003年   22篇
  2002年   10篇
  2001年   7篇
  2000年   7篇
  1999年   13篇
  1998年   5篇
  1997年   7篇
  1996年   6篇
  1995年   5篇
  1994年   7篇
  1993年   7篇
  1992年   15篇
  1991年   9篇
  1990年   11篇
  1989年   7篇
  1988年   10篇
  1987年   8篇
  1985年   6篇
  1984年   6篇
  1983年   8篇
  1981年   5篇
  1980年   4篇
  1979年   7篇
  1977年   4篇
  1974年   9篇
  1973年   5篇
  1972年   13篇
  1971年   8篇
  1970年   8篇
  1969年   11篇
  1968年   5篇
  1967年   5篇
  1966年   8篇
  1905年   3篇
排序方式: 共有512条查询结果,搜索用时 15 毫秒
91.
92.

Background

Canine necrotizing meningoencephalitis (NME) is a fatal, noninfectious inflammatory disease of unknown etiology. NME has been reported only in a small number of dog breeds, which has led to the presumption that it is a breed‐restricted disorder.

Hypothesis/Objectives

Our objective was to describe histopathologically confirmed NME in dog breeds in which the condition has not been reported previously and to provide preliminary evidence that NME affects a wider spectrum of dog breeds than previously reported.

Animals

Four dogs with NME.

Methods

Archives from 3 institutions and from 1 author''s (BS) collection were reviewed to identify histopathologically confirmed cases of NME in breeds in which the disease has not been reported previously. Age, sex, breed, survival from onset of clinical signs, and histopathologic findings were evaluated.

Results

Necrotizing meningoencephalitis was identified in 4 small dog breeds (Papillon, Shih Tzu, Coton de Tulear, and Brussels Griffon). Median age at clinical evaluation was 2.5 years. Histopathologic abnormalities included 2 or more of the following: lymphoplasmacytic or histiocytic meningoencephalitis or encephalitis, moderate‐to‐severe cerebrocortical necrosis, variable involvement of other anatomic locations within the brain (cerebellum, brainstem), and absence of detectable infectious agents.

Conclusions and Clinical Importance

Until now, NME has only been described in 5 small dog breeds. We document an additional 4 small breeds previously not shown to develop NME. Our cases further illustrate that NME is not a breed‐restricted disorder and should be considered in the differential diagnosis for dogs with signalment and clinical signs consistent with inflammatory brain disease.  相似文献   
93.
An observation made in the laboratory led to a two-year study showing a relationship between after-cooking discoloration and potato size. This relationship, the larger the potato the greater the blackening tendency, was consistent for all potatoes examined in this sudy whether they blackened severely or slightly. These findings may help future researchers correct the conditions that cause blackening.  相似文献   
94.
Free amino acid content, total nitrogen, extractable nitrogen, ratio of extractable to total nitrogen, solids content, and specific gravity in Cobbler, Katahdin, Kennebec, Red Pontiac, and Russet Burbank potatoes was studied. Each variety was grown in six different locations (Idaho, Maine, Pennsylvania, Wisconsin, Long Island, and the Red River Valley) during the years 1961 through 1963. The mean values for each factor, with significant differences indicated, are listed along with the high and low range, the coefficient of variation and the overall mean. The percent of total variance contributed by each of the variables and their interactions also are listed. Long Island potatoes had the highest nitrogen and amino acid content. Varietal differences were less significant. Proline was the most variable of the constituents measured. Aspartic and glutamic acids had the highest variability with respect to years grown. The effect of each variable varies from one constituent to another.  相似文献   
95.
Plasticity of motor behavior in monkeys with crossed forelimb nerves   总被引:1,自引:0,他引:1  
Monkeys in which nerves innervating the flexor muscles of the forearm and hand (the ulnar or the median nerve) had been surgically cross-united with the nerve innervating the extensor muscles (the radial nerve), and vice versa, showed excellent (ulnar-radial crosses) to moderate (median-radial crosses) control of movement performance after regeneration. Antagonistic movement responses were seen occasionally, but these were corrected almost immediately. Stimulation of the crossed nerves showed that they had innervated the antagonistic muscle groups. The results reveal the capacity of the primate central nervous system to adapt to gross disturbances imposed on the execution of movements by changes in peripheral innervation.  相似文献   
96.
ABSTRACT Coverless petri dishes with water suspensions of sporangia and zoospores of Phytophthora infestans were embedded in sandy soil in eastern Washington in July and October 2001 and July 2002 to quantify longevity of spores in water under natural conditions. Effects of solar radiation intensity, presence of soil in petri dishes (15 g per dish), and a 2-h chill period on survival of isolates of clonal lineages US-8 and US-11 were investigated. Spores in water suspensions survived 0 to 16 days under nonshaded conditions and 2 to 20 days under shaded conditions. Mean spore survival significantly increased from 1.7 to 5.8 days when soil was added to the water. Maximum survival time of spores in water without soil exposed to direct sunlight was 2 to 3 days in July and 6 to 8 days in October. Mean duration of survival did not differ significantly between chilled and nonchilled sporangia, but significantly fewer chilled spores survived for extended periods than that of nonchilled spores. Spores of US-11 and US-8 isolates did not differ in mean duration of survival, but significantly greater numbers of sporangia of US-8 survived than did sporangia of US-11 in one of three trials.  相似文献   
97.
ABSTRACT The development of specific oligonucleotide primers for Plasmodiophora brassicae has led to a nested polymerase chain reaction (PCR) detection method for P. brassicae in soil and water. Initially, the PCR was used to amplify a section of the rDNA repeat. The PCR products were sequenced and the data used to design primers that were directed at the ribosomal RNA genes and internal transcribed spacer regions. Specificity was tested against more than 40 common soil organisms, host plants, and spore suspension contaminants, as well as P. brassicae isolates from around Australia and the world. Sensitivity was determined to be 0.1 fentograms (fg; 10(-15) g) for pure template and as low as 1,000 spores per g of potting mix. In soil, P. brassicae was detected in all soils where the inoculum was sufficient to result in clubroot symptoms. Also outlined is a simple method of DNA extraction from soil.  相似文献   
98.
A discussion of the problems involved in the determination of the melting point of α-solanine is combined with an estimation of the reliability of this physical property for establishing the purity of a preparation.  相似文献   
99.
Simulation of the timing of anthesis in wheat crops is achieved using two very different approaches. The older of these simulates progress to flowering by calculating the duration of phases between significant events on the shoot apex. The alternative method tracks development through leaf appearance, using the prediction of final mainstem leaf number to control the duration of the phase from emergence to flowering. Although these methods appear to differ substantially, we show in this paper that the number of leaves on the mainstem when the stage of terminal spikelet occurs is extremely tightly coupled to final mainstem leaf number. We conclude that accurate prediction of the terminal spikelet stage or similar prediction of mainstem leaf number amount to the same thing, so reconciling the methods.  相似文献   
100.
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