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   511篇
  免费   47篇
林业   23篇
农学   9篇
基础科学   2篇
  74篇
综合类   78篇
农作物   13篇
水产渔业   130篇
畜牧兽医   170篇
园艺   11篇
植物保护   48篇
  2021年   3篇
  2019年   10篇
  2018年   6篇
  2017年   13篇
  2016年   19篇
  2015年   15篇
  2014年   17篇
  2013年   17篇
  2012年   23篇
  2011年   31篇
  2010年   18篇
  2009年   11篇
  2008年   27篇
  2007年   27篇
  2006年   16篇
  2005年   32篇
  2004年   17篇
  2003年   22篇
  2002年   22篇
  2001年   21篇
  2000年   9篇
  1999年   9篇
  1998年   9篇
  1997年   7篇
  1996年   5篇
  1995年   12篇
  1994年   7篇
  1993年   5篇
  1992年   5篇
  1991年   7篇
  1990年   5篇
  1988年   5篇
  1987年   5篇
  1985年   5篇
  1984年   3篇
  1983年   7篇
  1982年   3篇
  1981年   4篇
  1979年   5篇
  1978年   10篇
  1977年   4篇
  1976年   3篇
  1974年   5篇
  1973年   6篇
  1970年   3篇
  1968年   5篇
  1966年   3篇
  1954年   2篇
  1948年   3篇
  1947年   3篇
排序方式: 共有558条查询结果,搜索用时 562 毫秒
81.
Anticoagulant rodenticides (ARs) are considered inhumane, show increasingly limited efficacy due to acquired resistance, and carry environmental consequences associated with non-target species uptake. In a questionnaire study of 499 UK farms that all deployed chemical rodenticide we found a high mean reliance (79%), on second generation ARs with just over half of the respondents using no other rodent control methods. Additional methods where deployed, alone or in combination, included predation (41%), kill-trap deployment (16%) and shooting (1%). Nearly 40% of all respondents deployed rodenticides year-round. There was no evidence to suggest that “tidy-farm” measures, such as clearing food spills and minimising on-farm rodent harbourage sites aimed at minimising rodent-associated problems, were associated with a lower likelihood of year-round deployment; in fact trends in our analyses suggested the opposite. We therefore encourage operators to fully evaluate the true necessity of rodenticide deployment before AR use.  相似文献   
82.
83.
84.
Rapid measurement of salmon flesh quality parameters (>400 samples day?1) was demonstrated in the laboratory and remotely at industrial sites. Visible‐near infrared spectroscopy (VNIRS) was applied to predict astaxanthin (AX) and fat content in farmed Atlantic salmon. Fish were sampled from thirteen batches (1–6 kg whole weight, containing 2.3–16.3% fat and 1.2–12.5 μg g?1 AX), and models validated on small (average ± SD: 1.4 ± 0.4 kg) and large fish (4.2 ± 0.9 kg). Both constituents were well predicted in minced Norwegian Quality Cutlet (NQC) samples (r2 ≥ 0.86; standard error of prediction (SEP) ≤0.7% for fat and ≤0.7 μg g?1 for AX). Comparable metrics were observed for AX prediction in whole NQCs (r2 = 0.80–0.88; SEP 0.7 μg g?1). Fat was better predicted in small fish than large fish for whole NQCs (r2 = 0.82, SEP 1.0% cf r2 = 0.59, SEP = 0.59%) and non‐destructive scanning through the skin of whole, gutted fish (r2 = 0.77, SEP = 1.2% cf r2 = 0.49, SEP = 1.5%). Models were also developed for screening polyunsaturated fatty acid (PUFA) concentrations, e.g. in NQCs for docosahexaenoic acid (r2 = 0.73) and n‐3:n‐6 PUFA (r2 = 0.89).  相似文献   
85.
Fisheries Science - Understanding the role different habitats play in the life histories of fishes is important for the development of holistic aquatic ecosystem management plans. We used otolith...  相似文献   
86.
Insufficient iron (Fe) is one of the most prevalent micronutrient deficiencies in humans, with billions of people affected. Cereal grains are an important source of Fe for humans but the bioavailability of Fe in cereals is generally low. Information regarding the cellular and sub-cellular localisation of Fe in wheat grain will aid optimising nutrient delivery for human health. In this study high resolution secondary ion mass spectrometry (NanoSIMS) was used to map the distribution of Fe in the aleurone layer and in the endosperm of immature wheat grain. Iron was shown to be localised strongly in the phytin globoids in the aleurone cells and to a lesser extent in the cytoplasm around the starch granules in the endosperm.  相似文献   
87.
BACKGROUND: For an oil adjuvant to enhance uptake of a particulate active ingredient (AI), it is hypothesised that closer association between the two should result in higher uptake. Accordingly, factors important for the spray deposit size on grapevine leaves have been investigated for a series of model suspoemulsion formulations containing colloidal crystalline AI or fluorescent pigment particles and an emulsion of an oil adjuvant with different degrees of wetting and different spray volumes. RESULTS: Low spray volumes (<100 L ha(-1)) produced small deposits with high particle-adjuvant association. Complementary uptake studies showed increased uptake with decreasing deposit size, in agreement with the above hypothesis. Higher spray volumes produced larger deposits that consisted of annuli formed by pinning of the contact line by particles. Low surfactant concentrations favoured particles in the annulus and adjuvant separated in the centre. Intermediate surfactant concentrations produced annuli containing both particles and adjuvant, while with high surfactant concentrations the deposits were large with few annuli.CONCLUSIONS: Small deposits result in high AI-adjuvant association. With larger deposits, annulus structures allow for enhanced AI-adjuvant association (5-20 times greater). The formation of annuli appears to be important in enhancing the biodelivery of particulate AIs in adjuvant-containing suspoemulsion formulations at intermediate spray volumes.  相似文献   
88.
89.
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