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   254篇
  免费   0篇
林业   5篇
农学   8篇
  45篇
综合类   10篇
农作物   10篇
水产渔业   14篇
畜牧兽医   156篇
植物保护   6篇
  2022年   6篇
  2021年   10篇
  2020年   2篇
  2019年   4篇
  2018年   2篇
  2017年   1篇
  2016年   4篇
  2015年   4篇
  2014年   6篇
  2013年   41篇
  2012年   12篇
  2011年   8篇
  2010年   7篇
  2009年   6篇
  2008年   12篇
  2007年   14篇
  2006年   9篇
  2005年   10篇
  2004年   8篇
  2003年   8篇
  2002年   3篇
  2001年   7篇
  2000年   8篇
  1999年   9篇
  1998年   1篇
  1997年   1篇
  1994年   1篇
  1992年   6篇
  1991年   5篇
  1990年   5篇
  1989年   7篇
  1988年   5篇
  1987年   2篇
  1986年   5篇
  1985年   3篇
  1983年   4篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1966年   1篇
  1964年   1篇
排序方式: 共有254条查询结果,搜索用时 15 毫秒
121.
Soaking the seeds of most upland plants in water before sowing results in poor germination. Varietal differences in flooding tolerance of seeds have been reported in maize, soybean, barley and so on. This study was conducted to evaluate the varietal difference in wheat (2n = 42) seeds to soaking injury and to examine the importance of ethanol accumulation and seed coat as determinants of flooding tolerance. Of 342 varieties tested, many from Asia appeared more tolerant of flooding than the varieties from the Middle East. Soak-induced inhibition of germination and amounts of ethanol excreted were increased with soaking duration. Seeds of 26 wheat varieties were soaked 8 days at 20 °. Subsequent germination was correlated with amounts of ethanol excreted. Seeds with a red-colored coat exhibited higher tolerance to flooding than white ones, however, a varietal difference existed even in the case where the seed coat was peeled. These data suggest that soak-induced inhibition of wheat seed germination relates to accumulation of ethanol rather than seed coat color. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
122.
Changes in the taste of japonica, hybrid, and indica brown and milled rice, stored for 10 months at low (5 degrees C, 65-70% relative humidity) and room temperatures were observed by physicochemical analyses and a novel method using a taste sensing system. During storage, some properties increased or decreased while others were fairly constant. The main taste components of cooked rice such as sweetness (sucrose) and umami tastes (glutamic acid and aspartic acid) were reduced during storage, whereas glucose and fructose increased. The increase of fat acidity and consequent decrease of the pH value of the cooking solution may contribute to the off-taste of cooked stored rice. A taste sensing system with 10 lipid membrane sensors was also used to classify new and old rice samples using principal component analysis. Fresh and room temperature stored japonica and indica rice could be clearly distinguished; however, it was not possible to differentiate the samples stored at low temperature.  相似文献   
123.
124.
Pharmacokinetic profile and therapeutic range of plasma quinidine concentration were determined in dairy Holstein cows. Plasma half-life of intravenous quinidine was 1.28 +/- 0.492 (0.41-1.65) hr. The pattern of plasma quinidine transition after oral administration varied greatly among individuals. Total body clearance was 58.7 +/- 24.49 ml/min/kg, although renal quinidine clearance was 0.76 +/- 0.441 ml/min/kg. Therefore, the involvement of some extrarenal organ as the main site of excretion was suspected. Seven cows, diagnosed as atrial fibrillation or ventricular premature contraction, were orally administered with quinidine at various dosages. They showed plasma concentration of 2.3 +/- 1.59 mg/l when therapeutic effect was observed. Clinical signs of intoxication were observed at plasma quinidine concentrations over 10 mg/l. These results suggest the difficulty with the maintenance of effective plasma quinidine concentration by an oral or a single intravenous administration, and thus it is concluded that use of quinidine for treatment arrhythmic cows must be carefully done in order to avoid possible intoxication.  相似文献   
125.
A number of factors may be involved in the effect of nitrogen top-dressing applied during the stage of panicle primordia development on yield components of rice plants, such as varietal difference, climate condition, and soil fertility.  相似文献   
126.
The double-chambered right ventricle (DCRV) is a rare congenital cardiac disease in dogs, and its detailed epidemiological and morphological features are not clearly understood. By investigating the profile, clinical signs, and characteristics of examination findings of eleven dogs with DCRV by means of a retrospective study, we attempted to clarify the epidemiology and morphology of the condition. The study group consisted of nine males and two females. Breeds included Pug (n=3), Miniature Dachshund (n=1), French Bull-dog (n=1), Shiba (n=1), and Retrievers (n=5). The attachment site of the anomalous muscular bundle was continuous with the cardiac apex in nine dogs, and it was attached to the right ventricle free wall in the other two dogs. In dogs with DCRV, at least one of the following conditions was present concurrently: congenital or acquired tricuspid valve regurgitation (TR), ventricular septal defect, and atrial septal defect. Also, the pressure difference between the two chambers increased over time, and progressive right-sided heart failure was observed. In summary, DCRV occurs in small breeds of dog as well as in large breeds of dog and it may be more prevalent in males. The existence of two types of DCRV in dogs was established. Dog with DCRVs will have a high incidence of concurrent cardiac abnormalities. Concurrent TR may be either congenital or acquired. DCRV is a congenital disorder, but the clinical condition progresses as the dog develops.  相似文献   
127.
Eruption of 1-million-year-old tholeiitic basalt >1800 meters below sea level (>18 megapascals) in a backarc rift behind the Bonin arc produced a scoriaceous breccia similar in some respects to that formed during subaerial eruptions. Explosion of the magma is thought to have produced frothy agglutinate which welded either on the sea floor or in a submarine eruption column. The resulting 135-meter-thick pyroclastic deposit has paleomagnetic inclinations that are random at a scale of <2.5 meters. High magmatic water content, which is about 1.3 percent by weight after vesiculation, contributed to the explosivity.  相似文献   
128.
Abstract

Sulfur transformation in riee rhizosphere was investigated. Soil enzyme arylsulfatase in rhizosphere and non-rhizosphere soil, whieh is responsible for mineralization of organic sulfur to sulfate sulfur, was studied. The Michaelis constants of arylsulfatase from Maahas c1ay and Pila c1ay loam were 3.04 × 10-4 M and 3.97 × 10-4 M, respectively. The arylsulfatase of rhizosphere soil showed higher activity than that of non-rhizosphere soil. Applieation of sulfate had no marked elTect on the enzyme aetivity either in rhizosphere or non-rhizosphere soil under the submerged condition. This indieates that arylsulfatase activity under the submerged condition is not inhibited by applieation of sulfate. The amount of HI-reducible sulfur in the rhizosphere and non-rhizosphere soi! inereased with time. However, rhizosphere soil had a higher amount of HI-reducible sulfur than did non-rhizosphere. Thc ditl'erence in arylsulfatase activity between the rhizosphcre and non-rhizosphere soil was not directly associated with thc number of sulfur-redueing and -oxidizing bacteria.  相似文献   
129.
Abstract

To evaluate labile selenium (Se) content in agricultural soils in Japan and to investigate its determining factors, 178 soil samples were collected from the surface layer of paddy or upland fields in Japan and their soluble Se contents were determined. Two grams of soil was extracted with 20 mL of 0.1 mol L?1 sodium sulfate (Na2SO4) solution for 30 min in boiling water, and the released Se was reduced to Se (IV) after organic matter decomposition. The concentration of Se (IV) was then determined by high performance liquid chromatography (HPLC) with a fluorescence detector after treatment with 2,3-diaminonaphthalene (DAN) and extraction with cyclohexane. Soluble Se content ranged from 2.5 to 44.5 μg kg?1 with geometric and arithmetic means of 11.4 and 12.8 μg kg?1, respectively, and corresponded to 3.2% of the total Se on average. The overall data showed log-normal distribution. In terms of soil type, Non-allophanic Andosols and Volcanogenous Regosols had relatively high soluble Se content, and Wet Andosols and Lowland Paddy soils had relatively low soluble Se content. In terms of land use, upland soils had significantly higher soluble Se content than paddy soils (p < 0.01). The soluble Se content had significant positive correlation with total organic carbon (TOC) content of the extract, soil pH and total Se content (p < 0.01). In conclusion, total Se content in combination with soil pH was the main determining factor of the soluble Se content of agricultural soils in Japan.  相似文献   
130.
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