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   737篇
  免费   32篇
  国内免费   1篇
林业   56篇
农学   58篇
基础科学   10篇
  152篇
综合类   26篇
农作物   66篇
水产渔业   48篇
畜牧兽医   274篇
园艺   12篇
植物保护   68篇
  2023年   7篇
  2022年   22篇
  2021年   31篇
  2020年   31篇
  2019年   25篇
  2018年   46篇
  2017年   43篇
  2016年   31篇
  2015年   20篇
  2014年   25篇
  2013年   68篇
  2012年   36篇
  2011年   53篇
  2010年   21篇
  2009年   18篇
  2008年   25篇
  2007年   26篇
  2006年   14篇
  2005年   10篇
  2004年   17篇
  2003年   18篇
  2002年   9篇
  2001年   14篇
  2000年   12篇
  1999年   10篇
  1998年   6篇
  1996年   3篇
  1995年   3篇
  1994年   3篇
  1993年   2篇
  1992年   4篇
  1991年   5篇
  1990年   15篇
  1989年   8篇
  1988年   16篇
  1987年   8篇
  1986年   10篇
  1985年   6篇
  1984年   10篇
  1983年   6篇
  1982年   3篇
  1981年   2篇
  1980年   5篇
  1979年   3篇
  1978年   2篇
  1976年   3篇
  1974年   2篇
  1972年   4篇
  1967年   2篇
  1966年   4篇
排序方式: 共有770条查询结果,搜索用时 312 毫秒
681.
682.
683.
1. Nine hundred and sixty 1‐d‐old unsexed broiler chicks were used in a 4×4 eight weeks trial. Proprietary starter and finisher diets were given diluted with sand in the proportions of 0, 50, 75 and 100 g sand/kg diet.

2. At 8 weeks of age, birds receiving 50 and 75 g sand/kg diet were significantly heavier than those receiving the basal diet and 100 g sand/kg diet.

3. Birds receiving 0 and 100 g sand/kg diet consumed similar quantities of basal diet and yielded similar corrected food:gain ratios.

4. Dietary dilution with sand had no significant effect on mortality, apparent carcase yield, preventriculus weight, gizzard weight and intestinal length. Crop weights were significantly greater in birds given 100 g sand/kg diet to the age of 4 weeks.

5. The litter moisture content was significantly less in pens containing birds receiving 75 or 100 g sand/kg diet after 5 weeks of age.  相似文献   

684.
An avian paramyxovirus-1, which was previously isolated from ailing fancy Columba livia in Saudi Arabia, was characterized in this study using monoclonal antibodies (Mabs). The results indicate that although the virus belongs to the pigeon paramyxovirus-1 (PPMV-1) group 'P' still it shows some variation in its binding pattern to the Mabs.  相似文献   
685.
本文利用聚合酶链式反应对来自澳大利亚昆士兰州、维多利亚州和新南维尔士州的4株禽痘病毒田间分离株及二疫苗株中网状内皮组织增殖病毒的LTR片断、env及rel基因因进行了检测。所有4株痘病毒分离株均为LTR片断、env阳性,曾被PCR证实为LTR阳性的一疫苗株在本实验中也为LTR、env阳性,另一疫苗株为LTR、env阴性,所有上述禽痘病毒株均为rel阴性。  相似文献   
686.
油井采出液中微生物群落结构的T-RFLP分析   总被引:1,自引:0,他引:1  
应用末端标记限制性片段长度多态性(Terminal Restriction Fragment Length Polymorphism,T-RFLP)和克隆文库分析,以微生物群落16SrRNA基因(16S rDNA)为目标,对大庆油田过渡带油井采出液(于2005年7月和10月取样)中的微生物群落结构进行了解析和比较。T-RFLP分析表明,2005年7月和10月油井采出液中古菌群落结构较为单一,随时间变化不大;而细菌群落结构较为复杂,不同时间群落中的优势菌有明显的差别。古菌和细菌16S rDNA片段测序和系统发育分析表明,大庆油田过渡带油井采出液古菌群落中的优势菌均为产甲烷菌;细菌群落中的优势菌则与β、γ、δ、ε变形杆菌(Proteobacteria)、拟杆菌(Bacte-roidetes)和脱铁杆菌(Deferribacteres)有较高的相似性,细菌群落中检出了大量的未培养微生物(Deep-branching lineages)。  相似文献   
687.
Organic amendments considerably affect nutrient balance and interfraction mobility of nutrients by influencing the chemical, physical, and biological environment in soils. In this study, the effects of five amendments including: two composts, farmyard manure, packaging‐industry by‐product, and olive‐mill waste on time‐dependent interfraction mobility of P among mineral P fractions in two semiarid‐region soils differing in carbonate content and texture were investigated. Organic materials were applied at the rate of 0, 25, 50, and 100 g (kg soil)–1 soil thoroughly mixed and incubated at 27°C ± 2°C for 110 d. Phosphorus fractions were sequentially extracted by 0.1 M NaOH + 1 M NaCl (NaOH‐P), citrate‐bicarbonate‐dithionite (CBD‐P), and 0.5 M HCl (Ca‐P). Results showed that organic amendments especially farmyard manure significantly influenced NaOH‐P, CBD‐P, and Ca‐P. In addition, higher application rates of organic residues increased NaOH‐P fraction. NaOH‐P and CBD‐P fractions were increased after addition of organic residues and then converted to Ca‐P fraction within the end of incubation period. Increasing application rate of organic residues allowed P to be retained in more labile fractions for a longer period. The amount of Ca‐P was found to be related with carbonate content of soils. It can be concluded that organic residues applied to calcareous soils may enhance P nutrition of agricultural plants.  相似文献   
688.
Different proportions of tomato waste compost (TWC) were combined with peat moss and vermiculite as growth substrates used to evaluate the quality of seedlings of economic vegetables, including tomato, hot pepper, cucumber and summer squash. The seeding substrates used were: (T0), vermiculite: peat moss: TWC (4: 1: 0, by weight), 0% TWC; (T1), vermiculite: peat: TWC (4: 0.75: 0.25), 5% TWC; (T2), vermiculite: peat: TWC (4: 0.5: 0.5), 10% TWC; (T3), vermiculite: peat: TWC (4: 0.25: 0.75), 15% TWC; and (T4), vermiculite: peat: TWC (4: 0: 1), 20% TWC. The best seedling response was recorded in substrate mixtures supplemented with 5% and 10% TWC, which hastened seed germination and improved seedling morphology. Since vegetable seedlings produced with TWC-amended substrate were of higher quality, compared to those produced exclusively on peat substrate, we suggest that TWC may be used to replace partially peat-based substrate used for vegetable transplants production in nurseries.  相似文献   
689.
Yirdaw  Eshetu  Monge Monge  Adrian  Austin  Denis  Toure  Ibrahim 《New Forests》2019,50(6):1007-1026
New Forests - In Laos, there are extensive shifting cultivation areas and regrowth forests spontaneously established on fallow lands. The aims of the study were to conduct a comparative study of...  相似文献   
690.
Basal stem rot disease caused by the white‐rot fungus Ganoderma boninense is a major threat to the oil palm industry, and hence, the ability to detect infections at an early stage of development is desired. In this study, a headspace solid‐phase microextraction (HS‐SPME) method coupled with gas chromatography–mass spectrometry (GC‐MS) was employed to analyse the volatile organic compounds (VOCs) released from G. boninense cultures and infected oil palm wood. We examined VOCs released from three types of samples: G. boninense mycelium, oil palm wood and oil palm wood colonized by G. boninense. This preliminary study led to the tentative identification of 57 VOCs, including alcohols, alkanes, volatile acids, ketones, aldehydes, esters, sesquiterpenes and polycyclic aromatic hydrocarbon groups. Aliphatic compounds with eight‐carbon atoms, such as 1‐octen‐3‐ol, 3‐octanone, 1‐octanol and (E)‐2‐octenal, were the most abundant constituents of the Ganoderma samples, whereas furfural and hexanal were the major compounds detected in the oil palm wood samples. Chemometric analyses using cluster heat maps and principal component analyses were used to discriminate between the VOC profiles. The results indicated that the novel method described here could be used to detect Ganoderma disease and, more generally, for chemoecological studies of plant–pathogen interactions.  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