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   129篇
  免费   5篇
  国内免费   3篇
林业   7篇
农学   7篇
基础科学   1篇
  21篇
综合类   40篇
农作物   2篇
水产渔业   1篇
畜牧兽医   41篇
园艺   6篇
植物保护   11篇
  2023年   1篇
  2022年   2篇
  2021年   3篇
  2020年   2篇
  2019年   5篇
  2018年   1篇
  2017年   10篇
  2016年   5篇
  2015年   6篇
  2014年   4篇
  2013年   6篇
  2012年   8篇
  2011年   10篇
  2010年   9篇
  2009年   5篇
  2008年   7篇
  2007年   9篇
  2006年   4篇
  2005年   5篇
  2004年   2篇
  2003年   2篇
  2002年   1篇
  2001年   4篇
  2000年   3篇
  1999年   3篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1989年   1篇
  1988年   1篇
  1973年   3篇
  1933年   2篇
  1930年   1篇
  1912年   1篇
  1908年   1篇
  1858年   1篇
排序方式: 共有137条查询结果,搜索用时 15 毫秒
101.
干旱条件下糜子叶片衰老与保护酶活性变化   总被引:4,自引:1,他引:4  
在干旱棚栽培条件下以宁糜13号、内糜5号和晋糜4号糜子品种为材料,观测分析不同品种花后叶片叶绿素含量、保护酶活性(SOD、CAT、POD)以及丙二醛含量变化。结果表明,参试品种各功能叶片叶绿素含量及SOD、CAT、POD活性均在开花14 d后逐渐下降,MDA含量随着叶片的衰老而升高;参试品种叶片衰老的总体变化趋势一致,但衰老进程存在差异。与内糜5号和晋糜4号相比,宁糜13号叶绿素下降幅度小,各功能叶片衰老过程中SOD、CAT活性下降较慢,POD活性下降较快,MDA含量增加幅度小,叶片功能期长,衰老缓慢,有利于光合产物的积累;干旱条件下,叶绿素含量、过氧化氢酶CAT、超氧化物歧化酶SOD与单株产量呈正相关,而过氧化物酶POD、丙二醛MDA与单株产量呈负相关。  相似文献   
102.
Background: Histopathology is widely used for the diagnosis of inflammatory bowel disease in dogs. Variations in lesions and unavailability of uniform grading systems limit the usefulness of histologic examination.
Hypothesis: CD3 cell numbers in chronic enteropathies of dogs correlate with clinical activity of the disease and with severity of histopathologic changes.
Animals: Nineteen client-owned dogs examined because of chronic diarrhea, vomiting, or both.
Methods: Samples of duodenal and colonic mucosa were collected endoscopically before and after treatment. Dogs that responded to a hypoallergenic diet were grouped as food-responsive diarrhea dogs (FRD, n = 10). Dogs with no clinical improvement after 10 days of treatment then received prednisolone (immunosuppressive doses) and were grouped as steroid-responsive diarrhea dogs (SRD, n = 9). Histopathologic assessment with a standardized grading system was performed retrospectively on the intestinal samples. Histologic score, total number of infiltrating cells, and CD3-positive cells were counted and compared with the clinical scoring.
Results: No statistically significant difference was detected among histologic grading, total number of cells in the lamina propria, and T-cell numbers in biopsies before and after treatment in either group (FRD and SRD).
Conclusions and Clinical Importance: Currently used histopathologic grading scores, total numbers of cells, and numbers of CD3-positive cells did not allow differentiation between FRD and SRD and did not correlate with clinical response to therapy. Based on these results, new grading scores assessing other criteria than total cell numbers and CD3-positive cells should be evaluated in the future.  相似文献   
103.
运用层次分析法和模糊数学综合评判方法,对新疆天然甜型葡萄酒原料种植区域进行了研究,并建立了数学模型.结果表明,吐鲁番的评价最高,其次为和田,昌吉为不适宜种植区.  相似文献   
104.
A reduction of arbuscules in roots of grapevines (Vitis vinifera) observed when ring nematodes were added to field microplots led to the hypothesis that nematode feeding suppresses arbuscules by competing for root carbohydrates. Support for this hypothesis was tested by growing ‘Pinot noir’ grapevines in a factorial experiment with three levels of initial nematode densities (0, 0.1, 1.0 nematodes g?1 soil), two levels of light (full sun, 50% sun), and two levels of AMF (nonAMF, +AMF). Effects on plant growth were primarily driven by a light and AMF treatment interaction, such that low light increased stem dry matter accumulation at the expense of roots in +AMF vines only. Nematodes had only a minor influence on plant growth (leaf mass was reduced at the highest nematode density), but nematodes did not affect overall plant dry matter accumulation. Since nonAMF vines were severely limited by P and their growth was so poor, the impact of nematode and light treatments was further analyzed in +AMF plants only. Nematode populations, AMF colonization, and root carbohydrates were differentially affected by initial nematode density or light levels. Root biomass, and reducing sugar and starch concentrations in fine roots were reduced by low light, but the final nematode populations and arbuscule frequencies in roots were unaffected by light. Nematodes reduced arbuscules and starch concentrations in fine roots, but did not affect total colonization by AMF (hyphae, vesicles or arbuscules). Nematodes reduced plant P and K uptake at the highest density, and low light reduced Mg uptake. These findings are consistent with the hypothesis that ring nematodes suppress arbuscules in roots via competition for root carbohydrates. However, the lack of a treatment interaction between light and nematodes in our study suggests that ring nematode–AMF interactions in grape roots are controlled by more than competition for photosynthate.  相似文献   
105.
沙地柏人工林和天然林风沙土特性研究   总被引:1,自引:0,他引:1  
为了深入了解固沙植被恢复对土壤理化性质的影响,以毛乌素沙地东南缘沙地柏人工林和天然林为研究对象,通过收集灌丛下5个土层(0-100 cm)的土壤样品,分析其土壤颗粒组成及8个理化指标,探讨了沙地柏生长对风沙土特性的影响。结果表明:研究区土壤粒度组成以砂粒(体积分数97.09%)为主,其次是粉粒和黏粒,并形成以中砂(50.26%)为主的单峰,土壤弱碱性,其养分含量整体水平低,且具有明显表层聚集现象。土壤养分含量与土壤粒度之间存在良好的相关性,表现为土壤有机质、速效钾和盐分含量与细沙物质(粒径<100μm)含量呈线性正相关,与粗砂物质(100~500μm)呈线性负相关。沙地柏生长对风沙土改良效果呈现出人工林16 a树龄优于7 a树龄,天然林地迎风坡优于背风坡。整体上,造林时间增加土壤颗粒的粗细分配趋于良好态势发展,土壤结构优化,土地荒漠化进程减缓。因此,沙地柏可作为毛乌素沙地生态恢复工程的优良灌木。  相似文献   
106.
Ohne Zusammenfassung  相似文献   
107.
采用酵母双杂交系统,利用SMART技术,在酵母菌株AH109中构建了小粒野生稻全长cDNA文库,文库容量约为1×106,插入片段平均大小约为640bp。该文库可以用于进一步的酵母双杂交筛选。  相似文献   
108.
Processing reduces the glucosinolate (GSL) content of plant food, among other aspects due to thermally induced degradation. Since there is little information about the thermal stability of GSL and formation of corresponding breakdown products, the thermally induced degradation of sulfur-containing aliphatic GSL was studied in broccoli sprouts and with isolated GSL in dry medium at different temperatures as well as in aqueous medium at different pH values. Desulfo-GSL have been analyzed with HPLC-DAD, while breakdown products were estimated using GC-FID. Whereas in the broccoli sprouts structural differences of the GSL with regard to thermal stability exist, the various isolated sulfur-containing aliphatic GSL degraded nearly equally and were in general more stable. In broccoli sprouts, methylsulfanylalkyl GSL were more susceptible to degradation at high temperatures, whereas methylsulfinylalkyl GSL were revealed to be more affected in aqueous medium under alkaline conditions. Besides small amounts of isothiocyanates, the main thermally induced breakdown products of sulfur-containing aliphatic GSL were nitriles. Although they were most rapidly formed at comparatively high temperatures under dry heat conditions, their highest concentrations were found after cooking in acidic medium, conditions being typical for domestic processing.  相似文献   
109.
110.
疾病是全球范围内危害畜禽健康的主要问题,解析免疫系统调控相关基因成为当前抗病分子育种的研究热点。为研究小鼠黑色素瘤模型功能异常CD8~+T细胞对免疫抗体处理的应答机制,通过基因调控网络方法筛选功能异常CD8~+T细胞在Ig G和PD1抗体处理的特定基因、转录因子和细胞表面受体。结果发现对照组、PD1抗体与Ig G抗体处理组分别有28、17、33个特定表达基因。与对照组相比,Ig G和PD1处理组有2个转录因子Zfx、Zfhx3关闭表达,PD1处理组细胞表面受体Raet1b表达。Raet1b基因的表达可能使小鼠黑色素瘤功能异常CD8~+T细胞恢复功能,结果为抗病育种的相关基因研究提供理论基础。  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