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   1445篇
  免费   143篇
林业   107篇
农学   75篇
基础科学   3篇
  292篇
综合类   70篇
农作物   97篇
水产渔业   147篇
畜牧兽医   602篇
园艺   41篇
植物保护   154篇
  2023年   12篇
  2022年   32篇
  2021年   58篇
  2020年   62篇
  2019年   79篇
  2018年   88篇
  2017年   96篇
  2016年   89篇
  2015年   45篇
  2014年   93篇
  2013年   84篇
  2012年   109篇
  2011年   120篇
  2010年   70篇
  2009年   67篇
  2008年   69篇
  2007年   77篇
  2006年   51篇
  2005年   45篇
  2004年   53篇
  2003年   42篇
  2002年   26篇
  2001年   24篇
  2000年   11篇
  1999年   10篇
  1998年   4篇
  1997年   7篇
  1996年   3篇
  1995年   8篇
  1992年   6篇
  1991年   6篇
  1990年   7篇
  1989年   2篇
  1988年   4篇
  1987年   2篇
  1984年   2篇
  1983年   2篇
  1981年   3篇
  1980年   2篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1971年   2篇
  1969年   1篇
  1967年   1篇
  1951年   1篇
  1942年   1篇
  1941年   1篇
  1940年   1篇
排序方式: 共有1588条查询结果,搜索用时 31 毫秒
11.
12.
The immunological biomarkers profiles were evaluated using Luminex as putative measures to monitor canine mammary carcinomas (MCs). Forty female dogs were categorized into benign mixed tumour (MC‐BMT = 28) and mammary carcinoma (MC=12). The ascendant biomarker signatures were used to compare the groups. For example, a higher frequency of MC‐BMT animals producing IL‐6, CXCL‐8 and CXCL‐10 was observed, whereas for the MC group IL‐2 and CXCL‐8 were detected. MC‐BMT animals without metastasis had an increase in the levels of IL‐2, CXCL‐8, CXCL‐10, IL‐6, TNF‐α, IL‐15 and a decrease in IL‐10 and CXCL‐8. MC‐BMT animals with metastasis showed only an increase in CXCL‐10 and a decrease in IL‐18. After comparing the ascendant signatures following the presence of metastasis in both groups, a higher frequency of dogs exhibiting IL‐10 production was observed. Pearson correlation (P = 0.0273) and receiver operating characteristic (ROC) curve analysis revealed that this pattern was associated with worse outcome and lower survival rates in MC animals.  相似文献   
13.
14.
15.
16.
17.
The aim of this experiment was to compare the level of fish female stress during induced reproduction with pituitary extract by two different methods, natural and semiextruded. The reproductive efficiency was 62.5% in the seminatural treatment and 100% in the extruded. Obtained egg volume was 5200 ml and 4000 ml, for seminatural and extruded treatments respectively. The mean number of eggs was 46.7 for the seminatural and 52.0 and for the extruded treatment. The percentage of viable eggs was, respectively, 87.2% and 8.17% for the natural treatment and extruded semimethods. Blood samples were collected to quantify cortisol and glucose levels, as well as red cell series and lymphocyte count. Fishes submitted to induction procedures showed elevated cortisol and glucose levels, compared to the control animals. The results for haematocrit, haemoglobin concentration and red blood cell count showed no significant differences among groups. Significant differences found in the number of lymphocytes and monocytes suggest the general adaptation syndrome. Our results suggest the reproductive induction process with extrusion of gametes as a more stressful method than seminatural reproduction process.  相似文献   
18.
19.

Background

In Kenya, rice (Oryza sativa L.) is mainly produced under irrigation by small-scale farmers. Mwea irrigation scheme (MIS) in Kirinyaga County accounts for 80–88% of rice production. Here, rice is the main source of livelihood and a source of revenue generation for the county. However, a recently established invasive freshwater snail, Pomacea canaliculata (Lamarck) (family: Ampullariidae), a species of apple snail, presents a serious threat to rice production.

Results

Household surveys, focus group discussions and key informant interviews highlight apple snail as a serious problem in MIS. Households that observed at least a moderate level of infestation (>20% of cultivated area) experienced significant reductions in rice yield (~14%) and net rice income (~60%). Farmers reported increased use of chemical pesticides for management of apple snail. In addition, the cost of hired labor for physical removal of egg masses and snails is resulting in substantial negative effects on net income. Farmer age, area of land owned, responsibility for decision-making, receipt of extension advice, training, and membership of a farmer organization, were all statistically significant variables to explain farmers awareness of the need for area-wide apple snail management.

Conclusion

Strategies to limit the spread of apple snail are urgently needed. A Multi-Institutional Technical Team (MITT) has been established to spearhead management efforts and consolidate advice to farmers on how to manage apple snail. However, without action to mitigate spread, the consequences could be disastrous for rice production and food security in Kenya, and for other rice growing regions across Africa. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   
20.
Journal of Plant Diseases and Protection - Tobacco (Nicotiana tabacum L.) is one of the major nonfood crops in the Southern of Brazil. During 2019/2020 and 2020/2021 crop seasons, Root Knot...  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