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   385篇
  免费   18篇
  国内免费   15篇
林业   12篇
农学   15篇
基础科学   5篇
  110篇
综合类   81篇
农作物   59篇
水产渔业   35篇
畜牧兽医   70篇
园艺   6篇
植物保护   25篇
  2024年   2篇
  2023年   4篇
  2022年   3篇
  2021年   7篇
  2020年   9篇
  2019年   12篇
  2018年   7篇
  2017年   13篇
  2016年   12篇
  2015年   15篇
  2014年   22篇
  2013年   18篇
  2012年   27篇
  2011年   46篇
  2010年   12篇
  2009年   13篇
  2008年   25篇
  2007年   25篇
  2006年   16篇
  2005年   14篇
  2004年   9篇
  2003年   14篇
  2002年   6篇
  2001年   5篇
  2000年   7篇
  1999年   5篇
  1998年   3篇
  1996年   8篇
  1995年   2篇
  1993年   4篇
  1992年   1篇
  1991年   5篇
  1990年   4篇
  1989年   7篇
  1988年   4篇
  1987年   3篇
  1985年   4篇
  1981年   1篇
  1979年   3篇
  1977年   1篇
  1976年   1篇
  1975年   2篇
  1974年   3篇
  1971年   1篇
  1970年   2篇
  1969年   3篇
  1968年   1篇
  1965年   1篇
  1964年   1篇
  1963年   4篇
排序方式: 共有418条查询结果,搜索用时 15 毫秒
51.
PH Hong  YD Su  JH Su  YH Chen  TL Hwang  CF Weng  CH Lee  ZH Wen  JH Sheu  NC Lin  YH Kuo  PJ Sung 《Marine drugs》2012,10(5):1156-1168
Two new briarane diterpenoids, briarenolides, F (1) and G (2), were isolated from an octocoral identified as Briareum sp. The structures of briaranes 1 and 2 were established by spectroscopic methods and by comparison of the spectroscopic data with those of known briarane analogues. Briarenolide F was proven to be the first 6-hydroperoxybriarane derivative and this compound displayed a significant inhibitory effect on the generation of superoxide anion by human neutrophils.  相似文献   
52.
YH Chen  J Kuo  JH Su  TL Hwang  YH Chen  CH Lee  CF Weng  PJ Sung 《Marine drugs》2012,10(7):1566-1571
A novel 15C compound, pseudoalteromone B (1), possessing a novel carbon skeleton, was obtained from a marine bacterium Pseudoalteromonas sp. CGH2XX. This bacterium was originally isolated from a cultured-type octocoral Lobophytum crassum, that was growing in cultivating tanks equipped with a flow-through sea water system. The structure of 1 was established by spectroscopic methods. Pseudoalteromone B (1) displayed a modestly inhibitory effect on the release of elastase by human neutrophils.  相似文献   
53.
The present study aims to understand whether genotypic differences in grain iron (Fe) concentration in four rice genotypes are related to its association with protein bodies containing phytate‐rich inclusions. Rice genotypes with high and low grain Fe concentrations in unpolished brown rice were grown in a greenhouse at Chiang Mai, Thailand, and grains were harvested at maturity. The presence of protein bodies and phytate‐rich inclusions in rice grain tissues were examined by means of light and transmission electron microscopy (TEM). The composition of mineral elements in different grain tissues was examined using energy dispersive X‐ray microanalysis (EDX) and chemical analysis. The relative distribution pattern of protein bodies in the tissues was similar among the four rice genotypes, which resembled the pattern of grain N concentrations in these tissues. The high grain Fe genotypes (based on brown rice Fe concentration) had more protein bodies containing phytate‐rich inclusions in the embryo and aleurone layer tissues than the low Fe genotypes. Phytate‐rich inclusions were not detected in the endosperm tissues in all genotypes. In conclusion, the presence of protein bodies with phytate‐rich inclusions predominantly in the embryo and aleurone regions of the grain is an important parameter contributing to the variation in brown rice Fe concentration among the genotypes, but not in the white rice (the endosperm). Iron associated with the phytate‐rich inclusions present in the embryo and aleurone layer tissues are largely lost during the polishing process to produce white rice.  相似文献   
54.
【目的】克隆玉米Zea mays淀粉合成酶SSⅡa启动子,并分析其功能,为进一步研究和应用SSⅡa启动子奠定基础。【方法】通过NCBI上公布的玉米基因组序列,在网站Maize GDB上BLAST查找到SSⅡa 5'侧翼序列,利用PCR方法从玉米B73中克隆SSⅡa启动子;通过Plant Care在线分析启动子顺式作用元件,用特异性引物分别克隆出长度为1 407、867、633、483和365 bp的片段,与植物表达载体p CAMBIA3301连接,构建5种5'缺失体的植物表达载体,命名为P1、P2、P3、P4和P5。用农杆菌介导法转化拟南芥Arabidopsis thaliana,获得转基因拟南芥。【结果】以玉米B73基因组DNA为模板,用特异性引物SSⅡa F/SSⅡaR进行扩增,得到2 526 bp序列;除草剂筛选的阳性拟南芥植株PCR验证均检测出gus基因;GUS组织化学分析表明,5种类型启动子构建的表达载体在成熟期叶片、果荚中均显蓝色;gus基因定量分析表明,成熟期5种转基因拟南芥叶片中,gus基因表达量P1最高,其他基本一致;种子中gus基因表达量P1和P2相近,且高于P3、P4和P5。【结论】成功克隆玉米SSⅡa启动子;构建的5种SSⅡa启动子缺失体表达载体在转基因拟南芥中均具有活性,长度为1 407 bp(P1)和867 bp(P2)的启动子具有胚乳特异性。  相似文献   
55.
Sung PJ  Li GY  Su YD  Lin MR  Chang YC  Kung TH  Lin CS  Chen YH  Su JH  Lu MC  Kuo J  Weng CF  Hwang TL 《Marine drugs》2010,8(10):2639-2646
Two new 12-hydroxybriarane diterpenoids, designated as excavatoids O (1) and P (2), were isolated from the octocoral Briareum excavatum. The structures of briaranes 1 and 2 were established on the basis of extensive spectral data analysis. Excavatoid P (2) is the first metabolite which possesses a 6β -chlorine atom in briarane analogues.  相似文献   
56.
南疆不同品种绵羊MSTN基因克隆及其组织表达谱分析   总被引:2,自引:0,他引:2  
本研究旨在对山区型和田羊、平原型和田羊、卡拉库尔羊的MSTN基因进行组织表达谱分析。参考GenBank上(登录号:NM_001009428.1)绵羊MSTN基因序列设计引物,采用RT-PCR技术克隆绵羊MSTN基因序列,进行组织表达谱分析。结果表明:MSTN基因在各品种绵羊不同组织中表达的差异较大,MSTN在各品种绵羊的肌肉、肾脏和脾脏中都有表达,其中肌肉中表达量最高,其次是肾脏和脾脏;MSTN在山区型、平原型和田羊的心脏中表达丰度较低,而在卡拉库尔羊心脏中则几乎无表达;MSTN在山区型、平原型和田羊的肝脏中几乎无表达,而在卡拉库尔羊肝脏中则有一定量表达;MSTN在山区型和田羊、平原型和田羊与卡拉库尔羊的肺脏中则都无表达。  相似文献   
57.
The orphan G protein-coupled receptor (GPCR) GPR124/tumor endothelial marker 5 is highly expressed in central nervous system (CNS) endothelium. Here, we show that complete null or endothelial-specific GPR124 deletion resulted in embryonic lethality from CNS-specific angiogenesis arrest in forebrain and neural tube. Conversely, GPR124 overexpression throughout all adult vascular beds produced CNS-specific hyperproliferative vascular malformations. In vivo, GPR124 functioned cell-autonomously in endothelium to regulate sprouting, migration, and developmental expression of the blood-brain barrier marker Glut1, whereas in vitro, GPR124 mediated Cdc42-dependent directional migration to forebrain-derived, vascular endothelial growth factor-independent cues. Our results demonstrate CNS-specific angiogenesis regulation by an endothelial receptor and illuminate functions of the poorly understood adhesion GPCR subfamily. Further, the functional tropism of GPR124 marks this receptor as a therapeutic target for CNS-related vascular pathologies.  相似文献   
58.
以宣化牛奶葡萄的贮藏保鲜为研究对象,通过肥料组、奇宝组、益果灵组3种植物生长调节剂进行采前处理牛奶葡萄贮藏保鲜试验研究。结果表明:普通肥料组采前处理对牛奶葡萄贮藏的品质和寿命影响不显著,益果灵和奇宝2种植物调节剂对牛奶葡萄贮藏的品质和寿命的影响显著。  相似文献   
59.
Blood clotting exhibits various important functions, including the prevention of body fluid loss and invasion of pathogens in shrimp. The effects of pathogenic Vibrio harveyi on plasma of white shrimp (Litopenaeus vannamei) in vitro and in vivo were investigated in this study. The clotting protein (coagulogen) in plasma of white shrimp pre‐incubated with extracellular products (ECP) of V. harveyi was found apparently decreased and fast‐migrated in crossed immunoelectrophoresis (CIE) gels. In addition, the coagulogen had been degraded to many low molecular‐weight protein bands in plasma pre‐incubated with ECP on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) gels. When pre‐challenged with bacterial cells and ECP of V. harveyi, the white shrimp began to die at about 30 and 16 h respectively. Moreover, plasma coagulogen was decreased more obvious in shrimp challenged with ECP than that with bacterial cells as visualized in CIE gels, and total plasma protein in both group of shrimp were all decreased. Haemolymph withdrawn from moribund shrimp pre‐challenged with V. harveyi or its ECP was observed unclottable. However, the addition of clotting factors (transglutaminase and/or Ca2+) to these unclottable plasma could apparently promote their re‐clotting ability as jelly‐like solid observed in microtubes. The recovery of clotting ability of plasma from moribund shrimp was due to the reformation of coagulogen (200 kDa) after adding the two clotting factors as shown on CIE and SDS‐PAGE gels. The present results suggest that the infection of V. harveyi in white shrimp may not only degrade coagulogen but also influence the presence of transglutaminase and Ca2+ ion.  相似文献   
60.
3个单倍体诱导系的初步评价   总被引:2,自引:0,他引:2  
为了评价3个诱导系,将诱导系与6个玉米组合杂交,分析了初步诱导率。结果表明:诱导系间的初步诱导率存在显著差异;美诱系的初步诱导率(6.52%)显著高于日诱系(3.89%)和高诱1号(3.21%);基础组合间的初步诱导率差异不显著。  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