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   321篇
  免费   12篇
林业   23篇
农学   8篇
  29篇
综合类   23篇
农作物   6篇
水产渔业   48篇
畜牧兽医   176篇
园艺   1篇
植物保护   19篇
  2024年   1篇
  2022年   4篇
  2021年   11篇
  2020年   3篇
  2019年   4篇
  2018年   10篇
  2017年   5篇
  2016年   6篇
  2015年   7篇
  2014年   9篇
  2013年   21篇
  2012年   12篇
  2011年   22篇
  2010年   11篇
  2009年   6篇
  2008年   26篇
  2007年   17篇
  2006年   20篇
  2005年   26篇
  2004年   10篇
  2003年   10篇
  2002年   7篇
  2001年   12篇
  2000年   8篇
  1999年   5篇
  1998年   5篇
  1997年   2篇
  1996年   2篇
  1993年   2篇
  1992年   9篇
  1991年   4篇
  1990年   4篇
  1989年   8篇
  1988年   5篇
  1987年   3篇
  1986年   3篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1969年   1篇
  1967年   1篇
  1940年   1篇
排序方式: 共有333条查询结果,搜索用时 453 毫秒
31.
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   
32.
Morphiceptin (Tyr-Pro-Phe-Pro-NH(2)), tetrapeptide, was synthesized using dipeptidyl aminopeptidase IV (DP IV, EC 3.4.14.5) derived from Aspergillus oryzae RIB 915 as a catalyst. Tyr-Pro-OEt was incubated with Phe-Pro-NH(2) in the presence of DP IV under various conditions of temperature, concentrations of ethylene glycol, pH, reaction time, and others. Morphiceptin was obtained at 40% yield under the optimal reaction conditions: substrate, 4 mM Tyr-Pro-OEt.HCl and 20 mM Phe-Pro-NH(2).HCl; enzyme, DP IV, 0.275 nkat; solvent, 60% ethylene glycol containing 20 mM phosphate buffer at pH 7.0; amine, 4.2 mM diisopropylamine at 4 degrees C for 24 h. Amino group protection was unnecessary for synthesis of morphiceptin by DP IV.  相似文献   
33.
In clinical, patients usually take many kinds of drugs at the same time. Thus, drug-drug interactions involving transporters can often directly affect the therapeutic safety and efficacy of many drugs. However, there have been few studies on food-drug interactions involving transporters. Dietary polyphenols have been widely assumed to be beneficial to human health. Polyphenols are commercially prepared and used as functional foods. We report here for the first time that ferulic acid, which is widely used as a functional food, affects the transport of clinical agents. It is important to be aware of the potential of food-drug interactions and to act in order to prevent undesirable and harmful clinical consequences.  相似文献   
34.
35.
36.
37.
Giardia intestinalis antigen in fecal samples was examined in 361 dogs of 14 breeding kennels located at various areas in Japan, using a commercial enzyme-linked immunosorbent assay (ELISA) kit. G. intestinalis antigen was detected in 37.4% of the fecal specimens. All of the 14 breeding kennels were positive for G. intestinalis antigen with the range from 6.7 to 59.3%. The prevalence in puppies (54.5%) was significantly (p < 0.01) higher than that in adults (30.9%). There was no difference in prevalence between males and females, and between the puppies from the mother dogs positive and negative for Giardia antigen. In conclusion, G. intestinalis widely invaded the breeding kennels in Japan.  相似文献   
38.
A cutaneous mass at the base of the retroauricular region of a 4-year-old, female Golden Retriever was examined pathologically. Histologically, the mass formed multiple nodules consisting of a proliferation of large clear cells with abundant cytoplasm. Mitotic figures among the neoplastic cells were very sparse. The large clear cells were intensely positive for cytokeratins (AE1/AE4, cytokeratin 8 and 18) and moderately positive for lysozyme and contained periodic acid-Schiff-positive granules in the cytoplasm. In addition, small flat cells lined the islands of neoplastic large clear cells, and these were strongly positive for alpha-smooth muscle actin and vimentin, and some were positive for cytokeratin (AE1/AE4), suggesting they were myoepithelial cells. No local recurrence or metastasis has been recognized during the 18 months since surgical excision. On the basis of these findings, the present tumor was diagnosed as apocrine sweat gland adenoma, clear cell variant. There have been few previous reports of canine apocrine adenomas showing a clear cell morphology.  相似文献   
39.
Equine alpha 1-acid glycoprotein (alpha 1AG) was isolated from equine serum by successive ammonium precipitation, anion- and cation-exchange chromatographies, and gel filtration. Purified equine alpha 1AG had a molecular weight of 46,000 +/- 1,000, and contained 31.4% carbohydrate. Gel isoelectric focusing revealed an isoelectric point range of 2.8 to 3.7. With immunoelectrophoresis, it was found that alpha 1AG migrated to the alpha 1-globulin region. Single radial immunodiffusion was used for quantitative measurement of alpha 1AG in equine serum. In clinically normal foals, serum alpha 1AG was undetectable (less than or equal to 20 micrograms/ml) in less than or equal to 7-day-old foals, but was detected by 14 days. The alpha 1AG concentration (mean +/- SD) increased to reach mean adult values of 99.23 +/- 26.90 micrograms/ml by 1 year of age. The alpha 1AG concentration in pregnant mares decreased at 2 to 3 months before parturition, then gradually increased until 1 day after parturition, when a brief decrease was observed. The concentration increased again at 2 weeks after foaling, then a decrease was observed, after which the alpha 1AG concentration increased again by 2 to 4 months after parturition. The concentration of serum alpha 1AG quickly rose to peak values 2 to 3 days after castration and jejunojejunostomy in adult horses, returning to baseline values by 14 to 28 days after surgery. The alpha 1AG was concluded to be an acute-phase reactive protein in horses.  相似文献   
40.
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