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   406篇
  免费   33篇
林业   20篇
农学   8篇
  47篇
综合类   43篇
农作物   10篇
水产渔业   33篇
畜牧兽医   244篇
园艺   12篇
植物保护   22篇
  2023年   2篇
  2022年   5篇
  2021年   13篇
  2020年   6篇
  2019年   14篇
  2018年   15篇
  2017年   10篇
  2016年   11篇
  2015年   6篇
  2014年   5篇
  2013年   17篇
  2012年   26篇
  2011年   32篇
  2010年   12篇
  2009年   15篇
  2008年   33篇
  2007年   34篇
  2006年   24篇
  2005年   31篇
  2004年   27篇
  2003年   21篇
  2002年   23篇
  2001年   7篇
  2000年   1篇
  1999年   3篇
  1998年   5篇
  1997年   4篇
  1996年   7篇
  1995年   3篇
  1994年   1篇
  1993年   3篇
  1992年   1篇
  1991年   4篇
  1990年   1篇
  1989年   3篇
  1988年   3篇
  1985年   1篇
  1983年   2篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1977年   2篇
  1973年   1篇
  1971年   1篇
  1958年   1篇
排序方式: 共有439条查询结果,搜索用时 312 毫秒
81.
A traditional preparation of Parmotrema saccatilobum (Taylor) Hale (Family: Parmeliaceae) is being considered for inclusion into the PNG national drug formulary by the Ministry of Health Taskforce on Traditional Medicines. The lichen preparation is traditionally used in the Milne Bay province of Papua New Guinea for analgesic and anti-inflammatory activities. A hexane extract of P. saccatilobum yielded the principle components atranorin and chloroatranorin. Atranorin and chloroatranorin were tested in a COX-1 and -2 enzyme inhibition assay, which showed that atranorin inhibited COX-1 in a dose dependent manner and suggests partial inhibition by atranorin and chloroatranorin of COX-2 and COX-1, respectively.  相似文献   
82.
83.
Irritant threshold concentration (ITC) for intradermal testing (IDT) was determined in 31 healthy, clinically nonallergic dogs. Twenty‐three allergens were tested at five variable concentrations ranging from 1000 to 8000 PNU/mL. To distinguish irritant reactions from subclinical IgE‐mediated hypersensitivities, serum allergy testing was performed. ITCs were determined by evaluating the lowest concentration to which no dogs (0% cut‐off) and to which at least 10% of dogs (≥10% cut‐off) reacted. ITCs at the 0% cut‐off were: 1000 PNU/mL (Johnson grass), 2000 PNU/mL (Ash, Lamb’s Quarter and Bermuda), 3000 PNU/mL (Bahia, Rye, Pig Weed and Virginia Oak), 4000 PNU/mL (Marsh Elder and Maple), 5000 PNU/mL (Sorrel sheep) and 7000 PNU/mL (Cocklebur and Black Willow). ITC for Dog Fennel, Box Elder and Red Cedar was <1000 PNU/mL. ITCs at the ≥10% cut‐off were: 2500 PNU/mL (Johnson), 3000 PNU/mL (Box Elder), 5000 PNU/mL (Bahia), 6000 PNU/mL (Pigweed and Marsh Elder) and 8000 PNU/mL (Virginia Oak and Black Willow). For all other allergens, the ITC was >8000 PNU/mL and could not be determined. No significant agreement between positive values was found for the same allergen on IDT and serum allergy testing for each dog suggesting reactions caused by the determined ITCs are less likely subclinical IgE‐mediated reactions. These results suggest that ITCs may vary, also they may be very high for the allergens tested and that higher test concentrations may be used for IDT for the tested allergens without inducing an irritant reaction. Further studies are needed to evaluate the benefit of higher IDT concentrations in atopic dogs.  相似文献   
84.
Metastasis is a defining feature of malignant tumors and is the most common cause of cancer-related death, yet the genetics of metastasis are poorly understood. We used exome capture coupled with massively parallel sequencing to search for metastasis-related mutations in highly metastatic uveal melanomas of the eye. Inactivating somatic mutations were identified in the gene encoding BRCA1-associated protein 1 (BAP1) on chromosome 3p21.1 in 26 of 31 (84%) metastasizing tumors, including 15 mutations causing premature protein termination and 5 affecting its ubiquitin carboxyl-terminal hydrolase domain. One tumor harbored a frameshift mutation that was germline in origin, thus representing a susceptibility allele. These findings implicate loss of BAP1 in uveal melanoma metastasis and suggest that the BAP1 pathway may be a valuable therapeutic target.  相似文献   
85.
86.
87.
In this study three different approaches were employed to identify key odorants in Sauvignon blanc wines. First, the concentrations of the odorants were compared to their respective aroma detection thresholds. The resulting odor activity values (OAV) were transformed into a normalized and weighted measure that allows the aroma profiles of different wines to be compared and the contribution of a single aroma in a complex mixture to be evaluated. Based on their OAV, 3-mercaptohexanol and 3-mercaptohexyl acetate were the two most important aroma compounds in many Marlborough Sauvignon blanc wines. Due to limitations with the OAV approach, the study was extended to include aroma extract dilution analysis (AEDA), which revealed that β-damascenone, together with the varietal thiols, esters, and higher alcohols, are key odorants in Sauvignon blanc wines. The final approach undertaken was aroma reconstitution and omission tests using a deodorized wine base and the creation of a model Marlborough Sauvignon blanc. Single compounds and groups of compounds were omitted from the model to study their impact on the sensory properties of the model wine. Reconstitution and omission confirmed that varietal thiols, esters, terpenes, and β-damascenone are all important contributors to Sauvignon blanc aroma. The methoxypyrazines showed an important but relatively low impact in all three of the approaches undertaken in this study.  相似文献   
88.
89.
Water, Air, &; Soil Pollution - Effective and reliable treatment is needed to treat selenium (Se) in petroleum refinery effluents to meet water discharge limits established under the Clean Water...  相似文献   
90.
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