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   277篇
  免费   20篇
林业   18篇
农学   13篇
基础科学   5篇
  53篇
综合类   39篇
农作物   21篇
水产渔业   12篇
畜牧兽医   108篇
园艺   4篇
植物保护   24篇
  2024年   2篇
  2022年   7篇
  2021年   6篇
  2020年   5篇
  2019年   8篇
  2018年   8篇
  2017年   9篇
  2016年   9篇
  2015年   7篇
  2014年   10篇
  2013年   14篇
  2012年   8篇
  2011年   15篇
  2010年   10篇
  2009年   10篇
  2008年   14篇
  2007年   8篇
  2006年   6篇
  2005年   16篇
  2004年   10篇
  2003年   7篇
  2002年   5篇
  2001年   9篇
  2000年   4篇
  1999年   5篇
  1998年   3篇
  1996年   3篇
  1995年   2篇
  1993年   4篇
  1991年   2篇
  1990年   4篇
  1989年   3篇
  1987年   2篇
  1986年   4篇
  1985年   4篇
  1983年   2篇
  1982年   5篇
  1979年   4篇
  1978年   5篇
  1977年   2篇
  1976年   4篇
  1975年   2篇
  1974年   2篇
  1972年   2篇
  1971年   2篇
  1970年   5篇
  1968年   2篇
  1967年   3篇
  1966年   4篇
  1958年   1篇
排序方式: 共有297条查询结果,搜索用时 15 毫秒
81.
Three-dimensionally ordered array of air bubbles in a polymer film   总被引:1,自引:0,他引:1  
We report the formation of a three-dimensionally ordered array of air bubbles of monodisperse pore size in a polymer film through a templating mechanism based on thermocapillary convection. Dilute solutions of a simple, coil-like polymer in a volatile solvent are cast on a glass slide in the presence of moist air flowing across the surface. Evaporative cooling and the generation of an ordered array of breath figures leads to the formation of multilayers of hexagonally packed water droplets that are preserved in the final, solid polymer film as spherical air bubbles. The dimensions of these bubbles can be controlled simply by changing the velocity of the airflow across the surface. When these three-dimensionally ordered macroporous materials have pore dimensions comparable to the wavelength of visible light, they are of interest as photonic band gaps and optical stop-bands.  相似文献   
82.
83.
84.
85.
Intestinal sections from both experimental and field cases of turkey coronaviral enteritis (TCE) were examined by scanning electron microscopy and light microscopy through 10 days after inoculation and by a direct fluorescent antibody test for TCE through 12 days. Serums were collected for an indirect fluorescent antibody test for TCE through 160 days after inoculation. Lesions observed with the scanning electron microscopy were catarrhal enteritis with hemorrhage per diapedesis, epithelial desquamation, and villous atrophy which developed and regressed within 6 days after inoculation. Light microscopy demonstrated similar lesions, except that villus-to-crypt ratios remained depressed 10 days. The direct fluorescent antibody test demonstrated the presence of coronaviral antigen throughout the sampling period, and serum antibodies to TCE were present until at least 160 days, when the experiment was terminated.  相似文献   
86.
87.
88.
89.
Ultrasonographic examination was carried out in a cow with an ovarian abscess. Real time ultrasound scanning using a 7.5 MHz linear probe per rectum revealed an active left ovary with follicles of up to 11 mm in diameter and an enlarged right ovary measuring 6 x 6 cm, with a mass of 4 x 3 cm. The mass had varied echotexture, a thick hyperechoic boundary and a hypoechoic centre with echoic foci. It was tentatively diagnosed as an ovarian tumour or abscess. After ovariectomy, grossly the right ovary measured 6 x 6 x 5 cm and on cutting cheesy pus oozed out. The abscess was completely localised within the ovary, 4 cm in diameter and encapsulated thickly. On bacteriological examination Staphylococcus spp. was isolated. This is a rare case of ovarian abscess.  相似文献   
90.
Differences in the degree of starch granule swelling and granule morphology are shown as a function of iodine concentration during heating. The observations reveal a restriction and delay in wheat and corn starch swelling in presence of iodine (0.02%) and a lack of swelling at higher iodine concentration (0.2%). The presence of iodine during heating did not influence waxy corn starch granule swelling, even at the higher concentration. A delay in the increase in paste viscosity during heating was observed, and gel formation was precluded after cooling at the higher iodine concentration. Waxy corn starch pastes formed a weak gel even at the higher iodine concentration. Spectrophotometric analyses showed that polymers leach into the solution when heated in the presence of 0.02% iodine, while no leaching was observed at 0.2% iodine concentration. Furthermore, the length and the amount of polymers leaching from normal corn were different from that observed for wheat starch. Thermal analyses reveal a shift in the onset of gelatinization temperature and an increase in the enthalpy in the amylose‐lipid region of the endotherm. While the iodine‐polymer complex did not appear to exhibit an endotherm during heating, the granules exhibited a diffused polarized cross, suggesting the presence of an ordered complex.  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