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   1349篇
  免费   43篇
  国内免费   3篇
林业   112篇
农学   67篇
基础科学   18篇
  236篇
综合类   82篇
农作物   148篇
水产渔业   142篇
畜牧兽医   425篇
园艺   25篇
植物保护   140篇
  2023年   14篇
  2022年   48篇
  2021年   65篇
  2020年   74篇
  2019年   66篇
  2018年   52篇
  2017年   53篇
  2016年   50篇
  2015年   52篇
  2014年   59篇
  2013年   114篇
  2012年   91篇
  2011年   102篇
  2010年   50篇
  2009年   31篇
  2008年   57篇
  2007年   54篇
  2006年   36篇
  2005年   31篇
  2004年   34篇
  2003年   28篇
  2002年   26篇
  2001年   11篇
  2000年   12篇
  1999年   11篇
  1997年   5篇
  1996年   10篇
  1995年   5篇
  1994年   4篇
  1993年   6篇
  1991年   10篇
  1990年   7篇
  1989年   13篇
  1988年   9篇
  1987年   8篇
  1986年   6篇
  1985年   9篇
  1984年   6篇
  1983年   6篇
  1981年   6篇
  1979年   5篇
  1977年   4篇
  1976年   5篇
  1975年   7篇
  1973年   4篇
  1972年   4篇
  1971年   5篇
  1970年   5篇
  1969年   4篇
  1967年   4篇
排序方式: 共有1395条查询结果,搜索用时 15 毫秒
11.
Tropical Animal Health and Production - The main objective of this research was to evaluate the effects of chemical treatment and sonication (ultrasound) processing on the fiber composition and...  相似文献   
12.
The oesophagus is a muscular tube comprised of cervical and thoracic regions. Several studies have clarified the histological structure of the oesophagus. However, its histoarchitecture in relation to variable dietary habits of each species is still unclear. In the current study, 21 pigeons, cattle egrets and ducks, n = 7, each was used. Macroscopically, the oesophagus of cattle egrets either the cervical or thoracic parts was the longest among the pigeons and ducks. Histologically, the oesophagus comprised of four distinct tunicae: mucosa, propria submucosa, musculosa and adventitia or serosa. A great structural variation in these layers among the three investigated species was recorded. In the cervical oesophagus of pigeons, the superficial squamous cells showed perinuclear halo zone, the propria submucosa was characteristically lacked any gland. Moreover, its musculosa was very thick. On the other hand, the intraepithelial glands were characteristically distributed along the whole length of the cattle egret’s oesophagus. Interestingly, the cervical esophagus of the ducks showed submucosal associated lymphatic tissue; diffuse and nodular Ultrastructurally, the oesophageal glands showed secretory granules of variable electron densities, electron - lucent in the pigeons and ducks and electron - dense in the cattle egrets.  相似文献   
13.
This study investigated the effect of pentoxifylline (PTX) and Basal Medium Eagle (BME) on frozen–thawed goat spermatozoa. Immediately after initial examination of ejaculated semen, samples were pooled and reexamined for quality. Then, samples were divided into eight equal aliquots and diluted with a basic tris-extender containing PTX (3, 6, 9 mM) and BME (5 mM) to reach a final concentration of 25 × 109 and frozen. After 24 hr, the samples were individually thawed at 37°C for 30 s and evaluated for different characteristics. Obtained post-thaw results from Computer-Assisted Sperm Analysis indicate using of 3 and 6 mM PTX led significantly to an improvement in total motility, progressive motility and velocity characteristics of spermatozoa, except the beat/cross frequency (BCF) which indicated statistically no differences (p > .05) among control and treatments. Diluents prepared with BME (5 mM) and PTX alone (3 and 6 mM) improved significantly the membrane integrity–functionality, acrosome integrity and also hyaluronidase activity. Regarding recovery rate, the results showed significantly (p < .05) higher values for diluents containing 3 and 6 mM PTX compared to other groups. Malondialdehyde concentration exhibited also a significant difference (p < .05) in diluents supplemented with 5 mM BME, 3, 6 and 9 mM PTX, and mixture of 3 mM PTX and 5 mM BME which illustrate a similarity for active mitochondria, apoptotic-like and dead spermatozoa. Finally, the ratio of sperm chromatin dispersion stained spermatozoa presented significant differences (p < .05) among treatments in which the diluents added PTX alone demonstrated significantly lower values than control and extenders containing the mixtures of BME and PTX. In conclusion, the observation in this study indicates using of 3 and 6 mM PTX and BME alone may improve significantly (p < .05) the quality of cryopreserved goat spermatozoa.  相似文献   
14.
15.
16.
17.
18.
In this study, retinal whole‐mount specimens were prepared and stained with 0.1% cresyl violet for the ganglion cell study in the native duck (Anas platyrhynchos). The total number, distribution and size of these cells were determined in different retinal regions. The mean total number of ganglion cells was 1 598 501. The retinal area centralis had the highest ganglion cell density with 11 200 cells/mm2. Number of ganglion cell bodies was the highest in temporal area, followed by dorsal, nasal and ventral areas. Ganglion cell size ranged from 5.25 to 80 μm2. In the temporal and nasal region, most of the cells were ranged from 15 to 25 μm2, and in the dorsal and ventral region, most of the cells were ranged from 12 to 25 μm2. There was a marked trend for the retinal ganglion cell size to increase as the population density decrease towards the periphery. A population of small ganglion cells persisted into the central area just above the optic disc and the largest soma area was in the ventral zone of the retina. Thus, the specialisation of ganglion cell densities and their sizes support the notion that the conduction of visual information towards the brain from all regions of the retina is not uniform, and the central area is the fine quality area for vision in native duck.  相似文献   
19.
20.
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