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   379篇
  免费   8篇
  国内免费   1篇
林业   16篇
农学   14篇
基础科学   2篇
  43篇
综合类   16篇
农作物   13篇
水产渔业   49篇
畜牧兽医   203篇
园艺   4篇
植物保护   28篇
  2023年   2篇
  2022年   10篇
  2021年   27篇
  2020年   8篇
  2019年   3篇
  2018年   4篇
  2017年   6篇
  2016年   9篇
  2015年   18篇
  2014年   32篇
  2013年   27篇
  2012年   17篇
  2011年   33篇
  2010年   15篇
  2009年   22篇
  2008年   32篇
  2007年   22篇
  2006年   18篇
  2005年   12篇
  2004年   15篇
  2003年   21篇
  2002年   17篇
  2001年   4篇
  2000年   9篇
  1999年   1篇
  1998年   1篇
  1993年   1篇
  1991年   1篇
  1959年   1篇
排序方式: 共有388条查询结果,搜索用时 15 毫秒
351.
352.
353.
The Carnivora include the superfamilies Canoidea and Feloidea. In species of Canoidea other than the domestic dog, Canis lupus, the milk contains only traces of lactose and much larger concentrations of oligosaccharides. In this study, lactose was found to be the dominant saccharide in the milk or colostrum of two species of Feloidea, namely the African lion (Panthera leo) and the clouded leopard (Neofelis nebulosa). In addition to lactose, the following oligosaccharides were characterized in the milk of a lion; Neu5Gc(α2‐3)Gal(β1‐4)Glc (3′‐NGc‐SL), Fuc(α1‐2)Gal(β1‐4)Glc (2′‐fucosyllactose) and GalNAc(α1‐3)[Fuc(α1‐2)]Gal(β1‐4)Glc (A‐tetrasaccharide). The colostrum of a clouded leopard contained 3′‐NGc‐SL, Gal(α1‐3)Gal(β1‐4)Glc (isoglobotriose) and A‐tetrasaccharide. These oligosaccharides differ in some respects from those previously identified in another species of Feloidea, the spotted hyena (Crocuta crocuta). These milks contained 3′‐NGc‐SL and A‐tetrasaccharide, while spotted hyena colostrum did not; however, it contained Neu5Ac(α2‐3)Gal(β1‐4)Glc (3′‐NAc‐SL) and Gal(α1‐3)[Fuc(α1‐2)]Gal(β1‐4)Glc (B‐tetrasaccharide).  相似文献   
354.
Plant recognition of elicitors derived from pathogens induces various resistant reactions, including production of reactive oxygen species, hypersensitive cell death and accumulation of phytoalexins. Previously, we isolated a ceramide elicitor from Phytophthora infestans, which activates O2 production of potato suspension-cultured cells. In this study, we employed nine ceramide-related chemicals to test their elicitor activity. Although, none of the tested chemicals induced O2 production, N,N-dimethylsphingosine (DMS) induced accumulation of phytoalexin in potato tubers. In potato, tobacco and Nicotiana benthamiana, DMS also induced rapid cell death. DMS-treated potato cells stained with 4′,6-diamidino-2-phenylindole (DAPI) showed chromatin condensation, and isolated DNA from DMS-treated cells had ladder pattern, confirming that DMS-induced plant cell death is a hypersensitive reaction-like programmed cell death. Involvement of ceramide signaling in induction of plant defense reactions is discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
355.
In summer 2007, leaf and stem rot of ice plants was found in a hydroponic greenhouse in Japan. The causal agent was a fungus identified as Choanephora cucurbitarum (Berkeley & Ravenel) Thaxter, based on pathogenicity, morphology, mating tests, and sequence analysis of the ribosomal DNA ITS region.  相似文献   
356.
357.
358.
SHUNGO  OSHITANI  HIDEKI  NAKANO  SHO  TANAKA 《Fisheries Science》2003,69(3):456-464
ABSTRACT:   The present study estimated the age and growth of the silky shark Carcharhinus falciformis in the Pacific Ocean. Samples and biological data were collected from Japanese tuna longline and purse seine fisheries from 1992 to 1999. Vertebra centra were picked from 145 males and 153 females for age determination. The number of annual rings observed for males and females was 0–8 and 0–13, respectively. Combined sex von Bertalanffy growth equations were obtained as follows: Lt  = 216.4(1 − e−0.148( t +1.76)) where Lt is precaudal length in cm at age t . A mature size for males was considered to be approximately 135–140 cm (precaudal length), with an estimated age of 5–6 years, whereas corresponding values for females were 145–150 cm and 6–7 years, respectively. Birth size ranged from 48 to 60 cm. There was no remarkable difference in growth, birth size and age at maturity between the Pacific and Atlantic Oceans. The life history parameters of the silky shark are approximately the same in both oceans.  相似文献   
359.
Morphological changes to and collagen loss from the rat uterus during postpartum involution were investigated. The expression patterns of collagen type III and myeloperoxidase (MPO) were also determined. Morphological changes were studied on days 1, 3, 5, 10, 15, 20, 22 and 25 postpartum. As a control, diestrus rats’ uterine were used. Specimens from the uterine horn were embedded in paraffin, cut into 8 µm coronal sections, and stained with hematoxylin‐eosin. The thickness of the longitudinal and circular smooth muscle layers and of the endometrium were measured. The collagen content was determined using hydroxyproline analysis. Immunostaining was used to examine the expression of collagen type III on days 1, 3, 5, 10, 15 and 20 postpartum; and MPO on days 1, 3, 5, 10 and 22 postpartum. The thickness of the smooth muscle layers was found to decrease rapidly postpartum: the circular smooth muscle layer returned to that of a non‐pregnant, control uterus by day 5 postpartum and the longitudinal smooth muscle layer by day 15 postpartum. Eosinophilic cells were observed in the endometrial stroma adjacent to the myometrium on days 10, 15 and 20 postpartum, and were confirmed as collagenous cells. Immunostaining identified collagen type III positive cells in the vessel‐rich layer adjacent to the placental site on days 1, 3, 5 and 10 postpartum, and these cells were confirmed to be phagocytic. Postpartum reduction in the weight of the uterus was accompanied by decreases in both the collagen content and the thickness of the longitudinal and circular smooth muscle layers. Furthermore, the phagocytic cells were shown to express MPO during postpartum involution of the uterus.  相似文献   
360.
Eight pregnant heifers (primiparous cows) and seven pregnant cows in their second, third and forth pregnancies (multiparous cows) were assigned to two groups and fed either a low calcium (Ca) diet (Ca, 0.46%) or a high Ca diet (Ca, 0.86%) ad libitum from 3 weeks before the expected calving date to 3 days after parturition. All cows were examined for a change in dry matter intake (DMI), plasma minerals and bone turnover around parturition. The dietary Ca level did not affect the DMI in both primiparous and multiparous cows. The DMI of primiparous cows was significantly lower than that of multiparous cows (P < 0.05) in both the low and high dietary Ca groups. The dietary Ca level did not affect the concentrations of plasma Ca, phosphorus, magnesium and parathyroid hormone throughout the experimental period. Plasma phosphorus in primiparous cows was significantly higher (P < 0.05) than that of multiparous cows around parturition. Plasma Ca and magnesium tended to be higher (P < 0.10) in primiparous cows. The dietary Ca level did not affect the plasma osteocalcin (OC) level measured as bone formation or the urinary deoxypyridinoline (DPD) excretion measured as bone resorption before parturition in both primiparous and multiparous cows. After parturition, the plasma OC level was lower than it was before parturition in multiparous cows fed a low Ca diet, and in primiparous cows. There were no significant differences in urinary DPD excretion between each group before and after parturition. Both the plasma OC level and urinary DPD excretion of primiparous cows were significantly higher than those of multiparous cows in both the low and high dietary Ca groups.  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