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   887篇
  免费   64篇
林业   47篇
农学   52篇
基础科学   3篇
  154篇
综合类   114篇
农作物   46篇
水产渔业   84篇
畜牧兽医   352篇
园艺   22篇
植物保护   77篇
  2022年   12篇
  2021年   18篇
  2020年   18篇
  2019年   18篇
  2018年   17篇
  2017年   19篇
  2016年   19篇
  2015年   26篇
  2014年   15篇
  2013年   33篇
  2012年   46篇
  2011年   52篇
  2010年   23篇
  2009年   32篇
  2008年   42篇
  2007年   43篇
  2006年   40篇
  2005年   38篇
  2004年   33篇
  2003年   44篇
  2002年   36篇
  2001年   18篇
  2000年   14篇
  1999年   13篇
  1998年   12篇
  1997年   14篇
  1996年   8篇
  1995年   12篇
  1992年   8篇
  1991年   10篇
  1990年   7篇
  1988年   9篇
  1987年   6篇
  1986年   11篇
  1985年   8篇
  1984年   12篇
  1983年   12篇
  1982年   8篇
  1981年   6篇
  1980年   14篇
  1978年   10篇
  1976年   12篇
  1975年   9篇
  1974年   7篇
  1973年   10篇
  1972年   9篇
  1971年   6篇
  1970年   6篇
  1969年   7篇
  1966年   7篇
排序方式: 共有951条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
The methanol extract of the dried fruit powder of Terminalia pallida was evaluated for antimicrobial activity. The methanol extract showed a broad spectrum of antibacterial activity.  相似文献   
55.
In 2011, following severe flooding in Eastern Australia, an unprecedented epidemic of equine encephalitis occurred in South-Eastern Australia, caused by Murray Valley encephalitis virus (MVEV) and a new variant strain of Kunjin virus, a subtype of West Nile virus (WNVKUN). This prompted us to assess whether a delta inulin-adjuvanted, inactivated cell culture-derived Japanese encephalitis virus (JEV) vaccine (JE-ADVAX™) could be used in horses, including pregnant mares and foals, to not only induce immunity to JEV, but also elicit cross-protective antibodies against MVEV and WNVKUN. Foals, 74–152 days old, received two injections of JE-ADVAX™. The vaccine was safe and well-tolerated and induced a strong JEV-neutralizing antibody response in all foals. MVEV and WNVKUN antibody cross-reactivity was seen in 33% and 42% of the immunized foals, respectively. JE-ADVAX™ was also safe and well-tolerated in pregnant mares and induced high JEV-neutralizing titers. The neutralizing activity was passively transferred to their foals via colostrum. Foals that acquired passive immunity to JEV via maternal antibodies then were immunized with JE-ADVAX™ at 36–83 days of age, showed evidence of maternal antibody interference with low peak antibody titers post-immunization when compared to immunized foals of JEV-naïve dams. Nevertheless, when given a single JE-ADVAX™ booster immunization as yearlings, these animals developed a rapid and robust JEV-neutralizing antibody response, indicating that they were successfully primed to JEV when immunized as foals, despite the presence of maternal antibodies. Overall, JE-ADVAX™ appears safe and well-tolerated in pregnant mares and young foals and induces protective levels of JEV neutralizing antibodies with partial cross-neutralization of MVEV and WNVKUN.  相似文献   
56.
Dry deciduous forests of the eastern lateritic part of India are a typical case where forest valuation is yet to be integrated with the non-timber forest products like wild edible mushrooms (WEMs), which have a wide use in subsistence and cash income. A detailed accounting of the production and utilization of WEMs harvested from that region was made to highlight the economic worth of WEMs to the Santal community of this region. The WEMs production in the forest was in a polynomial pattern during the monsoon period. The net present value of revenues from WEMs was estimated to be contributing 9.83 and 10.29 % of total annual income of a Santal family of the Choupahari and Gonpur forests, respectively. The ecological footprint of the Santal communities on WEMs was higher in the forest area which was closer to the local markets than did the distant ones. Forest areas of the eastern lateritic part of India have a strong potentiality to produce WEMs that may be helpful for socio-economic upliftment of local tribal communities through the development of entrepreneurship and policy making.  相似文献   
57.
Within aquaculture, genetic engineering (GE) is emerging as a powerful method for breeding of fish and shellfish, and for developing alternative sources of feed and vaccines to combat diseases. On the other hand, the use of GE in aquaculture raises ecological, ethical and economic concerns. For instance, genetically modified (GM) feed could be spread to the aquatic environment and consumed by other marine organisms, and horizontal gene transfer may conceivably occur from DNA in feed or vaccines to a recipient genome or by faeces to the environment. Numerous reports have described beneficial effects such as viral disease resistance following DNA vaccination. However, side effects, such as activation of other genes than those which are central in immune defence mechanisms, may occur and warrant further investigations. In order to achieve sustainable introduction of GE, it is crucial that appropriate scientific investigations and ethical considerations are done prior to large-scale introduction of GE products such as DNA/GE vaccines and GM feed in commercial fish farming. This may result in a solid basis for the avoidance of potentially undesirable health and environmental effects. If GE can help make aquaculture a sustainable industry, this opens the possibility of positive market and consumer responses. This can best be achieved by involving the stakeholders from the conceptual stage to the commercial stage by facilitating a transparent process whose purpose is to inform research, to identify decision stakes, and to influence design, adoption and implementation of pro-active policy.  相似文献   
58.
Genetic Resources and Crop Evolution - Selection of elite accessions is important to get the maximum quantity of bioactive compounds in medicinal plants. In this study, thirteen accessions...  相似文献   
59.
Within the framework of a molecular exploration of target resistance in populations of Myzus persicae on oilseed rapes in France, (1) the S431F mutation (coding gene ace2), although previously reckoned to be rare, revealed to be frequent, (2) M918L (phenotypically characterised) and L932F (both on para) were found for the first time in M. persicae, and (3) a linkage was revealed between M918L and S431F. While until recently populations developing on French oilseed rapes were dominated by genotypes possessing pyrethroid target resistance and esterase overproduction, to date a different type of dominating genotype, equipped with carbamate and pyrethroid target resistance, seems to be invading such fields.  相似文献   
60.
The suitability of inland saline groundwater as a medium to culture juvenile cobia, Rachycentron canadum, was assessed. In the first experiment, juvenile cobia stocked in raw (unamended) saline groundwater at salinities of 5, 10, and 15 g/L exhibited complete mortality after 108, 176, and 195 hr, respectively. The second experiment evaluated the rearing of juvenile cobia (mean weight ~9.23 ± 0.12 g) in potassium (K+)‐amended saline groundwater (100% K+ fortified) and reconstituted seawater at salinities of 5, 10, and 15 g/L to assess growth and osmoregulation in distinct culture media. Following 60 days of culture, all fish survived the experimental period. Final mean bodyweight of cobia reared in K+‐amended saline groundwater (103.2–115.8 g) and seawater (111.2–113.8 g) of different salinities did not vary significantly (p > .05). No differences (p > .05) were observed in specific growth rate, weight gain (%), and feed conversion ratio between treatment groups. Serum osmolality increased with salinity and was significantly higher (p < .05) for fish in K+‐amended saline groundwater (353–361 mOsmol/Kg) than in reconstituted seawater (319–332 mOsmol/Kg), although differences were not observed between salinities by water type. Cobia stocked in saline groundwater of different salinities were osmoregulating normally, and the higher values observed may be because of variations in ionic composition and other interfering ions in saline groundwater. Trial results suggest that juvenile cobia can achieve optimal growth in K+‐amended saline groundwater of low and intermediate salinities.  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