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   277727篇
  免费   16044篇
  国内免费   635篇
林业   24086篇
农学   14157篇
基础科学   2977篇
  44453篇
综合类   27583篇
农作物   17202篇
水产渔业   17488篇
畜牧兽医   115708篇
园艺   6386篇
植物保护   24366篇
  2021年   2420篇
  2020年   2920篇
  2019年   3689篇
  2018年   4328篇
  2017年   4702篇
  2016年   4993篇
  2015年   4437篇
  2014年   5840篇
  2013年   16403篇
  2012年   7503篇
  2011年   9601篇
  2010年   7911篇
  2009年   8391篇
  2008年   8957篇
  2007年   8170篇
  2006年   8488篇
  2005年   7695篇
  2004年   7513篇
  2003年   7374篇
  2002年   6569篇
  2001年   7496篇
  2000年   6970篇
  1999年   6204篇
  1998年   3950篇
  1997年   3997篇
  1996年   3873篇
  1995年   4574篇
  1994年   3976篇
  1993年   3641篇
  1992年   4959篇
  1991年   5220篇
  1990年   4988篇
  1989年   5002篇
  1988年   4444篇
  1987年   4478篇
  1986年   4337篇
  1985年   4521篇
  1984年   4107篇
  1983年   3818篇
  1982年   3056篇
  1981年   2910篇
  1980年   2860篇
  1979年   3487篇
  1978年   3041篇
  1977年   2812篇
  1976年   2628篇
  1975年   2502篇
  1974年   2670篇
  1973年   2751篇
  1972年   2447篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Realizing sustainable development has become a global priority. This holds, in particular, for agriculture. Recently, the United Nations launched the Sustainable Development Goals (SDGs), and the Nineteenth National People’s Congress has delivered a national strategy for sustainable development in China—realizing green development. The overall objective of Agriculture Green Development (AGD) is to coordinate “green” with “development” to realize the transformation of current agriculture with high resource consumption and high environmental costs into a green agriculture and countryside with high productivity, high resource use efficiency and low environmental impact. This is a formidable task, requiring joint efforts of government, farmers, industry, educators and researchers. The innovative concept for AGD will focus on reconstructing the whole crop-animal production and food production-consumption system, with the emphasis on high thresholds for environmental standards and food quality as well as enhanced human well-being. This paper addresses the significance, challenges, framework, pathways and potential solutions for realizing AGD in China, and highlights the potential changes that will lead to a more sustainable agriculture in the future. Proposals include interdisciplinary innovations, whole food chain improvement and regional solutions. The implementation of AGD in China will provide important implications for the countries in developmental transition, and contribute to global sustainable development.  相似文献   
102.
Moharana  P. C.  Jena  R. K.  Pradhan  U. K.  Nogiya  M.  Tailor  B. L.  Singh  R. S.  Singh  S. K. 《Precision Agriculture》2020,21(2):426-448
Precision Agriculture - Delineation of management zones (MZs) are needed to manage fields in order to maximize economic return, minimize environmental impact, and improve soil and crop management....  相似文献   
103.
Lin  P.  Lee  W. S.  Chen  Y. M.  Peres  N.  Fraisse  C. 《Precision Agriculture》2020,21(2):387-402
Precision Agriculture - An accurate and robust strawberry flower representation and detection scheme is a key step to enable the reliable forecasting of fruit yield for use in precision...  相似文献   
104.

Grid sampling allows a variable rate of lime to be applied and has been marketed as a cost saver to producers. However, there is little research that shows if this precision application is profitable or not. Previous research on variable-rate lime has considered only a small number of fields. This paper uses soil sampling data from 111 fields provided by producers in Oklahoma and Kansas. The 5-year average net present values are compared between variable-rate and uniform-rate lime for grain-only wheat production, dual-purpose wheat grain and forage production, and a wheat–soybean rotation. Sensitivity analysis was done for varying grain prices as well as grain yield potential. When using historical average yields and recent prices for Oklahoma, variable rate was not profitable on average for these 111 fields for either a grain-only, dual-purpose, or wheat–soybean production. However, when yield or prices were above average, variable rate was profitable. Thus, variable rate liming can be profitable for these fields, but it requires either above average yields, a high value crop, or above average prices.

  相似文献   
105.
Precision Agriculture - In recent years, different algorithms have been utilised to delineate management zones, areas with similar properties, within agricultural fields. However, there are few...  相似文献   
106.
Precision Agriculture - Golf course superintendent’s knowledge of variability may be an overlooked and underutilized tool for precision turfgrass management (PTM). This case study used a...  相似文献   
107.
108.
Melatonin (MT) influences lipid metabolism in animals; however, the mechanistic effect of melatonin on liver fat and abdominal adipose deposition requires further clarity. In order to study the effects of melatonin on lipid metabolism, and hepatic fat and abdominal adipose deposition in animals, twenty Sprague–Dawley (SD) rats of 6 weeks of age with similar bodyweight were randomly divided into two groups: control (CTL) and MT-treated (10 mg/kg/day). During a 60-day experiment, food intake and bodyweight were measured daily and weekly respectively. At the end of treatment, blood samples were collected to collect plasma to quantify hormones and metabolic indicators of lipid metabolism. In addition, organ and abdominal adipose depots including liver, and omental, perirenal, and epididymal fat were weighed. Liver tissue was sampled for sectioning, long-chain fatty acid (LCFA) quantification, and gene chip and Real-time quantitative PCR (qPCR) analyses. The results showed that liver weight and index (ratio of liver weight to body weight) in MT group reduced by 20.69% and 9.63% respectively; omentum weight and index reduced by 59.88% and 54.93% respectively, and epididymal fat weight reduced by 45.34% (p = 0.049), relative to CTL. Plasma lipid indices, triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL) and total cholesterol (TC) with MT treatment decreased significantly compared with the control. Fat and 8 LCFA content in liver in MT group also decreased. Gene chip and qPCR demonstrated that there were 289 genes up-regulated and 293 genes down-regulated by MT. Further analysis found that the mRNA expression of lipolysis-related genes increased, while the mRNA expression of lipogenesis-related enzymes decreased (p < 0.05) with MT. This study concluded that melatonin greatly affected fat deposition, and hepatic LCFA supply and the expression of genes associated with lipogenesis and lipolysis.  相似文献   
109.
Eurasian Soil Science - The results of experiments on possible reduction of soil allelotoxicity level for grain crops are presented. It was found that autoclaving of soils significantly reduces...  相似文献   
110.
Eurasian Soil Science - Immobilized metal affinity chromatography (IMAC) has been used to fractionate organic compounds in alkaline extracts from forest soils of the Komi Republic by their ability...  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