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   406篇
  免费   25篇
林业   66篇
农学   10篇
  48篇
综合类   25篇
农作物   20篇
水产渔业   45篇
畜牧兽医   155篇
园艺   10篇
植物保护   52篇
  2023年   1篇
  2022年   4篇
  2021年   13篇
  2020年   10篇
  2019年   10篇
  2018年   14篇
  2017年   11篇
  2016年   14篇
  2015年   16篇
  2014年   13篇
  2013年   37篇
  2012年   21篇
  2011年   40篇
  2010年   20篇
  2009年   16篇
  2008年   22篇
  2007年   19篇
  2006年   19篇
  2005年   17篇
  2004年   11篇
  2003年   15篇
  2002年   15篇
  2001年   12篇
  2000年   15篇
  1999年   9篇
  1998年   4篇
  1997年   1篇
  1996年   2篇
  1994年   1篇
  1992年   2篇
  1991年   5篇
  1990年   5篇
  1988年   4篇
  1987年   4篇
  1985年   1篇
  1984年   1篇
  1983年   3篇
  1981年   1篇
  1980年   1篇
  1972年   1篇
  1967年   1篇
排序方式: 共有431条查询结果,搜索用时 328 毫秒
31.
Programmed cell death (PCD) in animals depends on caspase protease activity. Plants also exhibit PCD, for example as a response to pathogens, although a plant caspase remains elusive. Here we show that vacuolar processing enzyme (VPE) is a protease essential for a virus-induced hypersensitive response that involves PCD. VPE deficiency prevented virus-induced hypersensitive cell death in tobacco plants. VPE is structurally unrelated to caspases, although VPE has a caspase-1 activity. Thus, plants have evolved a regulated cellular suicide strategy that, unlike PCD of animals, is mediated by VPE and the cellular vacuole.  相似文献   
32.
Suspended gold nanowires were made in an ultra-high vacuum. The finest of them was 0.6 nanometer in diameter and 6 nanometers in length. By high-resolution electron microscopy, they were shown to have a multi-shell structure composed of coaxial tubes. Each tube consists of helical atom rows coiled round the wire axis. The difference between the numbers of atom rows in outer and inner shells is seven, resulting in magic shell-closing numbers.  相似文献   
33.
Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but oxygen isotopic compositions of asteroids themselves have not been established. We measured, using secondary ion mass spectrometry, oxygen isotopic compositions of rock particles from asteroid 25143 Itokawa returned by the Hayabusa spacecraft. Compositions of the particles are depleted in (16)O relative to terrestrial materials and indicate that Itokawa, an S-type asteroid, is one of the sources of the LL or L group of equilibrated ordinary chondrites. This is a direct oxygen-isotope link between chondrites and their parent asteroid.  相似文献   
34.
Methanol extracts of 11 kinds of commonly available vegetables were examined for hydroxyl radical scavenging potency using the bleomycin-Fe method. In this method, the iron ion and bleomycin in water form hydroxyl radicals, and the scavenging activity is monitored by the modified thiobarbituric acid method. All extracts showed scavenging capacity, even though the activity of some of them was lower than that of l-ascorbic acid. Those vegetables were classified into three groups according to their activity, groups showing strong activity, moderate activity, and weak activity, as compared to the activity of l-ascorbic acid at the same concentration. Among them, the methanol extract of radish sprout (Japanese name "kaiware-daikon") exhibited the highest potency (1.8 times as l-ascorbic acid). Then, we investigated the constituents of the methanol extract of radish sprout and the contribution to the overall activity of each compound by examining their activity. As the result, several kinds of sinapinic acid esters and flavonoids were isolated with high radical scavenging potency, which must contribute substantially to the activity.  相似文献   
35.
From the leaves of barley, Hordeum vulgare, one new flavone C-glucoside and three known flavone glucosides were isolated and characterized by (1)H and (13)C NMR and MALDI-TOF-MS. The novel flavone C-glucoside was isovitexin 7-O-beta-[6' "-O-(E)-p-coumaroyl]glucoside (6' "-coumaroylsaponarin), and the known compounds were isovitexin 7-O-beta-[6' "-O-(E)-feruloyl]glucoside, isoorientin 7-O-beta-[6' "-O-(E)-feruloyl]glucoside, and tricin 7-O-beta-glucoside. The sum of all the flavone glycosides and soluble phenolic acids in the leaves decreased with increased rate of plant nutrients given in animal manure and with increased crop yield. All of the major phenylpropanoids showed the same general response to nutrient level. The concentration of nitrogen in the leaves was not directly related to nutrient application or to contents of phenylpropanoids.  相似文献   
36.
Preface     
Water, Air, &; Soil Pollution -  相似文献   
37.
38.
Since the isotopes can not be utilized for veterinary patients in Japan, the authors developed a simple calculation formula of shunt fraction of portosystemic shunt based on the hepatic circulation model. The shunt fraction can be calculated utilizing only 2 portal pressure measurements of pre-shunt ligation and temporary or permanent shunt ligation. The calculated shunt fraction can obtained pre-ligation and post-ligation either temporally or permanent complete shunt ligation: complete ligation group of PSS (n=59) had 48.2 +/- 16.9% of shunt fractions, whereas the partial ligation group (n=48) had 71.6 +/- 10.7% of shunt fractions.  相似文献   
39.
The dog of this case was a 10-year-old Shih Tzu with refractory vomiting, diarrhea and anorexia. Endoscopy revealed an unclear at gastric angle, a stenosis at pyloric antrum and congestion in duodenal mucosa. Since abnormal shadows of irregular echo-levels were disclosed by pancreas ultrasonography, serum gastrin level was determined with a suspect of gastrinoma. And an increase of serum gastrin was demonstrated. In addition, postmortem histological examination revealed that the pancreatic cells were positive for gastrin. Based on these findings, the dog was diagnosed as pancreatic gastrinoma.  相似文献   
40.
In the summer of 2003, sporadic cases and an outbreak of human leptospirosis probably related to recreation in rivers occurred in the northern part of Okinawa Main Island. Sixteen of 22 suspected cases were definitely diagnosed as leptospirosis by serological test or isolation. The infective leptospiral serovar in 14 cases was presumed to be Hebdomadis. Transmission was thought to occur by exposure to river water that was contaminated by the urine of infected animals. The findings indicate that recreation in rivers in this area is a significant risk factor for infection with leptospires.  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