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   354篇
  免费   27篇
  国内免费   3篇
林业   27篇
农学   33篇
基础科学   4篇
  67篇
综合类   42篇
农作物   28篇
水产渔业   41篇
畜牧兽医   114篇
园艺   12篇
植物保护   16篇
  2024年   1篇
  2022年   16篇
  2021年   8篇
  2020年   12篇
  2019年   9篇
  2018年   9篇
  2017年   16篇
  2016年   15篇
  2015年   17篇
  2014年   6篇
  2013年   21篇
  2012年   15篇
  2011年   23篇
  2010年   25篇
  2009年   27篇
  2008年   17篇
  2007年   16篇
  2006年   22篇
  2005年   16篇
  2004年   18篇
  2003年   16篇
  2002年   11篇
  2001年   8篇
  2000年   5篇
  1999年   4篇
  1998年   5篇
  1997年   7篇
  1996年   2篇
  1995年   1篇
  1993年   7篇
  1992年   4篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1983年   1篇
  1980年   1篇
排序方式: 共有384条查询结果,搜索用时 734 毫秒
31.
32.
33.
34.
Detection and isolation of H1N1 influenza virus from pigs in Korea   总被引:5,自引:0,他引:5  
Choi C  Ha SK  Chae C 《The Veterinary record》2004,154(9):274-275
  相似文献   
35.
The expression of three isoforms of nitric oxide synthase (NOS) were examined in the testis and epididymis of a thoroughbred horse. Immunohistochemical studies demonstrated the presence of eNOS immunostaining in some germ cells in the seminiferous tubules and in vascular endothelial cells in the interstitial tissues. Interstitial cells, most likely Leydig cells, were also intensely immunopositive for eNOS. The pattern of immunostaining for nNOS was similar to that for eNOS in the testis. Weak expression of iNOS was detected in the seminiferous tubules of the testis, but intense expression was found in interstitial cells. Inducible NOS was also strongly detected in stereocilia, sperm, epithelium and connective tissue of the epididymis of normal horses. These findings suggest that three isoforms of NOS are expressed in the testis and epididymis of horse and that they play important roles in the biology of interstitial cells that produce testosterone, as well as in spermatogenesis in the seminiferous tubules.  相似文献   
36.
A total of 1002 Escherichia coli strains isolated from pre-weaned pigs with diarrhoea on 1114 swine farms were screened for the presence of the adhesin involved in diffuse adherence (AIDA) gene by polymerase chain reaction (PCR). Escherichia coli isolates that carried AIDA genes were also tested by PCR for the detection of five fimbriae (F4, F5, F6, F18 and F41), heat-stable (STa, STb) and heat-labile (LT) enterotoxin, enteroaggregative E. coli heat-stable enterotoxin 1 (EAST1), and Shiga toxin 2 oedema disease (Stx2e) genes. Twenty-three (2.3%) of the 1002 E. coli isolates carried the gene for AIDA. Among 23 isolates shown to carry genes for AIDA, three carried the AIDA gene as the only shown virulence factor. Other isolates carried other virulence factor genes in addition to AIDA. Four isolates carried genes for at least one of the fimbrial adhesins and enterotoxins. Sixteen isolates carried genes for enterotoxins only. The AIDA may represent an additional virulence determinant in pre-weaned pigs with diarrhoea.  相似文献   
37.
Field trials testing a total of 27 clones of the interspecific hybrid Acacia mangium × A. auriculiformis and seedling controls of the parental species were established at Ba Vi and Yen Thanh in the north of Vietnam and Long Thanh in the south. At both Ba Vi and Yen Thanh there were significant (P < 0.001) differences in height and diameter at breast height (DBH) among 22 tested clones at 4 years. At Long Thanh, twelve hybrid clones did not differ significantly in DBH at age 3 years, but did (P < 0.001) at age 5 years. At the two northern sites the acacia hybrid clones had significantly greater DBH than control seedlots of the parental species. At Long Thanh, DBH of the hybrid clones and A. mangium was similar, with a genetically improved seedlot of A. mangium displaying the best DBH. Mean wood basic density at breast height of the acacia hybrid clones was 539 kg m−3 at Yen Thanh at age 8 years, and 473 kg m−3 at Long Thanh at age 5 years; density for A. mangium at Long Thanh was only slightly lower than the hybrid clones at 461 kg m−3. Linear regressions of Pilodyn penetration (PP) at breast height on wood basic density explained 60% of the variance in density of treatments (clones and control seedlots) at Yen Thanh and 36% at Long Thanh. There were significant differences between hybrid clones in PP at all three trial sites. Clonal DBH performance was not strongly correlated across the three trial sites; Pearson correlations of clone mean DBH between pairs of sites ranged from −0.47 to 0.20. Clonal rankings for PP were more stable, with Pearson correlations between pairs of sites ranging from r = 0.71 to 0.78.  相似文献   
38.
Accumulating data suggest a relationship between chemerin and energy metabolism. Our group previously described gene cloning, expression analysis and the regulatory mechanism of chemerin and its own receptor in mice and cattle. The objective of the present study was to investigate the physiological effect of chemerin on endocrine changes and energy metabolism in sheep using a biologically stable chemerin analog. The chemerin analog was intravenously administrated (100 or 500 µg/head) to sheep, and plasma insulin and metabolites (glucose, nonesterified fatty acids (NEFA), triglyceride, total cholesterol and high‐density lipoprotein (HDL) cholesterol) were analyzed. The chemerin analog dramatically increased the insulin levels, and glucose levels were decreased. NEFA levels were slightly decreased at 20 min but then increased gradually from 60 to 180 min after analog administration. In addition, injection of the chemerin analog immediately increased triglyceride and total cholesterol but not HDL levels. These results suggested that chemerin analog regulated insulin secretion related to glucose metabolism and the release of triglycerides in sheep in vivo. This study provides new information about endocrine and metabolic changes in response to chemerin in sheep.  相似文献   
39.
This study was conducted to evaluate the growth characteristics and fatty acid composition among 15 kenaf mutants derived from the kenaf germplasm C14 and 15 kenaf accessions originating from Russia, India, China, Iran, and Italy. The overall growth performance (plant height, stem diameter, flowering date, leaf, and flower size) of the stem color mutant lines derived from C14 are similar to those of the original variety. However, the flower color mutant lines derived from C14 showed flowering to occur 10 days later when compared with the original variety and showed smaller leaf sizes than the original variety. Late-ripened kenaf accessions (Jinju, Auxu, and Jnagdae) can yield more bio-mass compared with early or medium-maturing germplasm. The late maturity kenaf (Auxu, Jinju, and Jangdae) has a higher oil percentage than the early maturity germplasm. Linoleic, oleic, and palmitic acids were the predominant fatty acids in all kenaf seeds. The stem color mutant lines significantly surpassed the parental means of all saturated fatty acids. In addition, the flower color mutant lines showed broad ranges of variation in oleic acid. The 15 accessions showed a wide range of fatty acid compositions, spanning from 29.75 to 38.30% saturated fatty acids and 61.70 to 70.24% total unsaturated fatty acids, and the late maturity kenaf has a higher linoleic acid percentage than the early maturity germplasm. The flowering period was highly positively (P ≤ 0.01) correlated with the plant height, stem diameter, oil percent, and linolenic acid (C18:3), and it was significantly negatively (P ≤ 0.01) correlated with stearic acid (C18:0). These results will provide valuable information to assist the parental selection of kenaf breeding.  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