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   338篇
  免费   26篇
  国内免费   1篇
林业   12篇
农学   2篇
  44篇
综合类   77篇
农作物   10篇
水产渔业   12篇
畜牧兽医   199篇
植物保护   9篇
  2021年   16篇
  2020年   4篇
  2019年   11篇
  2018年   9篇
  2017年   7篇
  2016年   6篇
  2015年   5篇
  2014年   8篇
  2013年   11篇
  2012年   22篇
  2011年   13篇
  2010年   16篇
  2009年   8篇
  2008年   10篇
  2007年   12篇
  2006年   15篇
  2005年   16篇
  2004年   20篇
  2003年   8篇
  2002年   11篇
  2001年   12篇
  2000年   14篇
  1999年   10篇
  1998年   5篇
  1997年   2篇
  1996年   2篇
  1994年   2篇
  1992年   4篇
  1991年   5篇
  1989年   4篇
  1988年   2篇
  1987年   2篇
  1986年   2篇
  1984年   2篇
  1983年   4篇
  1982年   2篇
  1980年   2篇
  1979年   7篇
  1978年   2篇
  1977年   5篇
  1976年   3篇
  1974年   4篇
  1970年   3篇
  1969年   16篇
  1968年   3篇
  1937年   2篇
  1935年   1篇
  1932年   1篇
  1928年   1篇
  1914年   2篇
排序方式: 共有365条查询结果,搜索用时 531 毫秒
361.
The removal of atmospheric effects from Nimbus-7 Coastal Zone Color Scanner (CZCS) images reveals eddy-like ocean turbidity patterns not apparent in the original calibrated images. Comparisons of the phytoplankton pigment concentrations derived from the corrected CZCS radiances with surface measurements agree to within less than 0.5 log C, where C is the sum of the concentrations of chlorophyll a plus phaeopigments a (in milligrams per cubic meter).  相似文献   
362.
As a result of the redundancy of the genetic code, adjacent pairs of amino acids can be encoded by as many as 36 different pairs of synonymous codons. A species-specific "codon pair bias" provides that some synonymous codon pairs are used more or less frequently than statistically predicted. We synthesized de novo large DNA molecules using hundreds of over-or underrepresented synonymous codon pairs to encode the poliovirus capsid protein. Underrepresented codon pairs caused decreased rates of protein translation, and polioviruses containing such amino acid-independent changes were attenuated in mice. Polioviruses thus customized were used to immunize mice and provided protective immunity after challenge. This "death by a thousand cuts" strategy could be generally applicable to attenuating many kinds of viruses.  相似文献   
363.
The coagulant and inflammatory exacerbation in sepsis is counterbalanced by the protective protein C (PC) pathway. Activated PC (APC) was shown to use the endothelial cell PC receptor (EPCR) as a coreceptor for cleavage of protease activated receptor 1 (PAR1) on endothelial cells. Gene profiling demonstrated that PAR1 signaling could account for all APC-induced protective genes, including the immunomodulatory monocyte chemoattractant protein-1 (MCP-1), which was selectively induced by activation of PAR1, but not PAR2. Thus, the prototypical thrombin receptor is the target for EPCR-dependent APC signaling, suggesting a role for this receptor cascade in protection from sepsis.  相似文献   
364.
The objective of this study was to evaluate the efficacy of topical application of a hyaluronan (HA) derivative in wound healing with respect to the rate of epithelialization, fibroplasia, angiogenesis and contraction, magnitude of the local inflammatory response, local expression of transforming growth factor-β 1 and 3 (TGF-β 1 and 3), tumor necrosis factor-α (TNF-α), and collagen type III deposition. In six healthy adult horses, six full-thickness skin wounds were created on the dorsal aspect of both metacarpi using a sterile template. Sites were sampled at 0, 1, 2, 5, 14, 21, and 35 days following wounding. Wounds on one limb were dressed with commercially available esterified HA fleece under a nonadherent dressing. The opposite limb was covered with the nonadherent dressing alone (control). Images of the most proximal wounds were used to determine the area of total healing and the relative contributions of epithelialization and contraction to healing. At each sample time, a control and treatment biopsy were taken for histological evaluation and special stains. All samples were evaluated for degree of inflammation, fibroplasia and angiogenesis; in situ hybridization for type III collagen, TGFβ1 and 3, and immunohistochemistry for TNF-α. Mean percentages of total wound healing, epithelialization, and wound contraction were not significantly different between control and treatment groups. In treated horses, initial wound expansion was significantly decreased during the first 2 weeks. Mononuclear cell numbers, counted in the granulation tissue, increased in both control and treated limbs over the entire course of the study. However at day 35 the macrophage numbers counted in the treated horses were significantly increased compared with the control limbs (P < .05). Although not statistically significant, relative staining for type III collagen in the treated wounds was less than that of control wounds. Results of the present study do not support a benefit of an exogenous HA-derivative in the healing of distal limb wounds in horses. The shortcomings of the study design are discussed.  相似文献   
365.
The study evaluated the effect of gender status on carcass and meat quality of feedlot Angus × Nellore cattle. A total of 176 cattle, 20 months old, were confined for 190‐days and assigned to four treatments: bulls, immunocastrated, steers, and heifers. Bulls had greater rib eye area and HCW (p = 0.0001). Heifers had increased fat thickness (p = 0.0001). Steers and heifers had higher marbling scores (p = 0.0001). There was interaction between gender and aging time for Warner‐Bratzler Shear Force (p = 0.0002), L* (p = 0.0118), and b* (p = 0.0113) values of beef. The sensory panel results showed that beef from bulls had the lowest consumer overall acceptance (p = 0.0278). Especially, regardless tenderness, steers and immunocastrated beef were considered tender, independent of aging time. Beef produced by heifers, steers, and immunocastrated is considered to be of higher quality than bulls. Thus, it is may be an interesting alternative to produce high‐quality beef than bulls, to attend the consumer demand for high‐quality products. Additionally, the low fatty acids n6 levels and low n6:n3 ratio, high levels of CLA, MUFAs, and oleic acid suggests that the heifer meat is favorable for human health.  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