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   364篇
  免费   4篇
林业   59篇
农学   18篇
  31篇
综合类   20篇
农作物   27篇
水产渔业   31篇
畜牧兽医   132篇
园艺   5篇
植物保护   45篇
  2024年   1篇
  2022年   6篇
  2021年   19篇
  2020年   4篇
  2019年   7篇
  2018年   14篇
  2017年   6篇
  2016年   9篇
  2015年   27篇
  2014年   19篇
  2013年   22篇
  2012年   20篇
  2011年   30篇
  2010年   19篇
  2009年   17篇
  2008年   28篇
  2007年   19篇
  2006年   15篇
  2005年   20篇
  2004年   14篇
  2003年   11篇
  2002年   9篇
  2001年   10篇
  2000年   5篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1992年   3篇
  1991年   3篇
  1989年   1篇
  1978年   1篇
  1969年   1篇
排序方式: 共有368条查询结果,搜索用时 15 毫秒
111.
112.
Fisheries Science - In the original publication the text in right column of page 330, the sequences of primers were incorrectly published as.  相似文献   
113.
Journal of General Plant Pathology - Bacterial brown stripe caused by Acidovorax avenae subsp. avenae (Aaa) causes serious damage on creeping bentgrass on golf course greens. However, there are few...  相似文献   
114.
Eucrites are a class of basaltic meteorites that share common mineralogical, isotopic, and chemical properties and are thought to have been derived from the same parent body, possibly asteroid 4 Vesta. The texture, mineralogy, and noble gas data of the recently recovered meteorite, Northwest Africa (NWA) 011, are similar to those of basaltic eucrites. However, the oxygen isotopic composition of NWA011 is different from that of other eucrites, indicating that NWA011 may be derived from a different parent body. The presence of basaltic meteorites with variable oxygen isotopic composition suggests the occurrence of multiple basaltic meteorite parent bodies, perhaps similar to 4 Vesta, in the early solar system.  相似文献   
115.
Mitotic indices of the ruminal epithelium of two castrated male sheep fed at 11:00 h were determined at 00:00, 04:00, 08:00, 12:00, 16:00 and 20:00 h. The schedules were repeated in four trials done in December 1975, February, March and June 1976 respectively. The indices ranged from 0.13 to 0.92 per cent, both animals showing a similar tendency in these fluctuations. The mean rate of cell division was low in the morning, high in the afternoon and in the evening, and declined at about midnight. Another pair of male castrated sheep were fed at 07:00, and rumen samples were biopsied six times in three days. The mean rate of epithelial cell division in the rumen was low at 08:00, but high at noon, suggesting that the rate possibly was affected by the food intake of the experimental animals.  相似文献   
116.
To investigate the influence of heating and drying history on the microstructure of dry wood, in addition to the dynamic viscoelastic properties, CO2 adsorption onto dry wood at ice.water temperature (273 K) was measured, and the micropore size distribution was obtained using the Horvath-Kawazoe (HK) method. Micropores smaller than 0.6 nm exist in the microstructures of dry wood, and they decreased with elevating out-gassing temperature and increased again after rewetting and drying. Dry wood subjected to higher temperatures showed larger dynamic elastic modulus (E′) and smaller loss modulus (E″). This is interpreted as the result of the modification at higher temperature of the instability caused by drying. Drying history influenced the number of micropores smaller than 0.6 nm in dry wood not subjected to high temperature, although the difference in the number of micropores resulting from the drying history decreased with increasing out-gassing temperature. A larger number of micropores smaller than 0.6 nm exist in the microstructure of dry wood in more unstable states, corresponding to smaller E′ and larger E″ than in the stable state. Consequently, unstable states are considered to result from the existence of temporary micropores in the microstructures of dry wood, probably in lignin. Part of this report was presented at the 55th Annual Meeting of the Japan Wood Research Society, Kyoto, March 2005, and at the 56th Annual Meeting of the Japan Wood Research Society, Akita, August 2006  相似文献   
117.
To investigate micropores and mesopores in the cell walls of dry wood, CO2 gas and N2 gas adsorption onto dry wood were measured at ice-water temperature (273 K) and liquid nitrogen temperature (77 K). CO2 gas adsorption isotherms obtained were used for determining micropore volumes smaller than 0.6 nm by the HK method (Horvath-Kawazoe method), and N2 gas adsorption isotherms obtained were used for determining the mesopore volume between 2 nm and 50 nm by the Barrett-Joyner-Halenda (BJH) method. Micropores and mesopores existed in cell walls of dry wood, and the cumulative pore volume was much larger for micropores than for mesopores. Micropores in the cell wall of dry wood decreased with elevating heat treatment temperature, and the decreased micropore was reproducible by wetting and drying. Mesopores did not decrease so much with elevating heat treatment temperature. Micropore volumes for the softwood Hinoki and the hardwood Buna were compared. A larger amount of micropores existed in hardwood Buna than in softwood Hinoki, and this relationship was considered to correspond to the difference in thermal softening properties for lignin in water-swollen Hinoki and Buna. This result probably indicates that micropores in the cell walls of dry wood relate to the structure of lignin.  相似文献   
118.
Severe rot of stem bases caused by Pythium aphanidermatum was found on ulluco (Ullucus tuberosus) grown in Kagawa Prefecture, Japan, in September 1999. The name “foot rot of ulluco” is proposed for this new disease. Received 14 November 2001/ Accepted in revised form 7 January 2002  相似文献   
119.
This study examined the feasibility of near infrared spectroscopy as a novel technique for log assessment on the basis of wood property. Near infrared (NIR) spectra were obtained from the transverse section of green log and multivariate regression analysis was carried out to predict the stiffness of veneer processed from the log. The stiffness of the veneer was dynamic modulus of elasticity measured using ultrasonic method. The calibrations of veneer stiffness had moderate relationships between measured and NIR-predicted values, with regression coefficients ranging from 0.84 to 0.88. The calibration equations were applied to the test set and it was found that predictions were also well fitted, with regression coefficients ranging from 0.67 to 0.89. The results indicate that the variation of wood stiffness within the logs could be assessed using the NIR spectra from the cross-section of logs. The spectra were obtained from green condition of the log and the stiffness of veneer was measured after kiln drying. Thus, the results imply that the wood stiffness in dry condition could be predicted using the spectra collected from green logs. If the models obtained in this study put into the imaging system, the two-dimensional map of the stiffness would be visualized on the cross-section of logs. The NIR spectroscopy coupled with imaging system could compensate the weak point of the traditional methods for log assessment.  相似文献   
120.
To investigate the effect of CO2 laser incising under five drying methods on drying characteristics of Sugi lumber, the squares (120 mm × 120 mm) of Sugi lumber with length of 650 mm were used. A half of samples were incised by CO2 laser with incising density of 2,500 holes/m2. Five types of drying methods were used: microwave drying, steam injection drying, and three combinations of microwave heating and steam injection drying. Steam injection drying was conducted by injecting superheated steam of 120 °C through a perforated plate heated to 140 °C of an injection press. Microwave was irradiated with the power of 3 kW at frequency of 2.45 GHz. The results indicated that incising helps heat through a specimen and thus the whole temperature raised rapidly, which was up to threefolds compared to that of no-incised one. Incised specimens dried by a combination of microwave heating for 1 h and steam injection showed the highest drying rate, which was up to 5.3 %/h. Incising and microwave heating contributed positively to dry lumber under more uniform distribution of moisture content and to reduce surface and internal checks. Incised specimen dried by microwave showed the most uniform distribution of moisture content without surface and internal checks.  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