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   274篇
  免费   6篇
林业   22篇
农学   7篇
  20篇
综合类   25篇
农作物   7篇
水产渔业   40篇
畜牧兽医   145篇
园艺   1篇
植物保护   13篇
  2024年   1篇
  2022年   3篇
  2021年   2篇
  2020年   1篇
  2019年   2篇
  2018年   5篇
  2017年   2篇
  2016年   4篇
  2015年   3篇
  2014年   7篇
  2013年   17篇
  2012年   9篇
  2011年   17篇
  2010年   6篇
  2009年   6篇
  2008年   22篇
  2007年   14篇
  2006年   17篇
  2005年   24篇
  2004年   11篇
  2003年   11篇
  2002年   9篇
  2001年   12篇
  2000年   8篇
  1999年   5篇
  1998年   6篇
  1997年   3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280条查询结果,搜索用时 0 毫秒
31.
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   
32.
Mammalian tooth crowns have precise functional requirements but cannot be substantially remodeled after eruption. In developing teeth, epithelial signaling centers, the enamel knots, form at future cusp positions and are the first signs of cusp patterns that distinguish species. We report that ectodin, a secreted bone morphogenetic protein (BMP) inhibitor, is expressed as a "negative" image of mouse enamel knots. Furthermore, we show that ectodin-deficient mice have enlarged enamel knots, highly altered cusp patterns, and extra teeth. Unlike in normal teeth, excess BMP accelerates patterning in ectodin-deficient teeth. We propose that ectodin is critical for robust spatial delineation of enamel knots and cusps.  相似文献   
33.
34.
35.
36.
We observed a significant difference in the organic acid profile of diarrheal feces between pigs infected with and free from pathogenic spirochetes. Diarrhea and loose feces were collected from growing pigs, held at 15 different commercial farms. A total of 106 samples were measured for organic acid concentration by HPLC and were checked for the presence of B. hyodysenteriae and B. pilosicoli by PCR. B. hyodysenteriae was detected in 3 samples collected from one farm. B. pilosicoli was detected in 5 samples collected from another farm. Lower concentrations of iso-butyrate and iso-valerate were likely associated with development of pathogenic spirochete infection.  相似文献   
37.
Sampling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.  相似文献   
38.
Fiber quality is very important for all the steps of the textile area. Underwater shock wave has been utilized for metal, wood, food processing and medical applications and renewed and increased application during the last decade. The main object of this study, is to demonostrate underwater shock wave as a surface treatment of natural fibers such as jute and cotton in form of yarn and to report characterized properties of the treated fibers. The underwater shock wave was generated by the explosion of the detonation fuse in the water tank. The process of bubble generation and expansion inside the water results in the formation of shock wave. Natural fibers were exposed to shock wave treatment depending on the different pressures and detonatinon fuse separation distance. After shock-loading, fibers were selected for physicomechanical and physicochemical tests such as Scaning Elecron Microscopy (SEM) analysis, breaking strength, moisture behavior, permeability and wicking test. The maximum effect with improved moisture content, permeabilty and wicking properties were observed from 100 MPa. The treated fiber showed high performance necessary for use in woven and non woven purpose.  相似文献   
39.
Reproductive functions decline with the onset of diabetes in female mice. Diabetic mice have smaller uteri with an underdeveloped endometrium, suggesting diminished estrogen-induced growth. We aimed to clarify the changes in the estrous cycle and in insulin-like growth factor 1 (IGF1) expression in the uteri of streptozotocin (STZ)-treated diabetic mice, because IGF1 is one of the main growth factors involved in estrogen-induced uterine growth. ICR female mice were intraperitoneally administered STZ (10 mg/100 g BW), and blood glucose levels were determined. Mice with blood glucose levels > 200 mg/dl were classified as diabetic mice. The onset of diabetes was associated with acyclic estrous cycles. Diabetes was also induced with STZ in ovariectomized mice. Uterine Igf1 mRNA levels were reduced in ovariectomized STZ-treated diabetic mice. Estrogen is known to stimulate Igf1 mRNA expression in the uterus, but estrogen action was abolished in the uteri of STZ-treated diabetic mice. mRNA expressions of estrogen receptor α (ERα) and steroid hormone receptor coactivators (SRC-1/Ncoa1, SRC-2/Ncoa2, SRC-3/Ncoa3 and CBP/p300/Crebbp) were reduced in the uteri of ovariectomized STZ-treated diabetic mice. The present study demonstrates that diabetes induces a decline in female reproductive functions in mice. Igf1 expression in ovariectomized diabetic female mice was decreased, and decreased responsiveness to estrogen in the uteri of diabetic mice is probably associated with a reduction in ERα and steroid receptor coactivator mRNA expression.  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