全文获取类型
收费全文 | 25812篇 |
免费 | 1513篇 |
国内免费 | 860篇 |
专业分类
林业 | 12595篇 |
农学 | 623篇 |
基础科学 | 627篇 |
2982篇 | |
综合类 | 9729篇 |
农作物 | 192篇 |
水产渔业 | 117篇 |
畜牧兽医 | 525篇 |
园艺 | 380篇 |
植物保护 | 415篇 |
出版年
2024年 | 106篇 |
2023年 | 315篇 |
2022年 | 411篇 |
2021年 | 554篇 |
2020年 | 591篇 |
2019年 | 813篇 |
2018年 | 368篇 |
2017年 | 581篇 |
2016年 | 805篇 |
2015年 | 773篇 |
2014年 | 1428篇 |
2013年 | 1317篇 |
2012年 | 2261篇 |
2011年 | 2119篇 |
2010年 | 1718篇 |
2009年 | 1739篇 |
2008年 | 1675篇 |
2007年 | 1826篇 |
2006年 | 1505篇 |
2005年 | 1278篇 |
2004年 | 1019篇 |
2003年 | 867篇 |
2002年 | 702篇 |
2001年 | 660篇 |
2000年 | 513篇 |
1999年 | 350篇 |
1998年 | 314篇 |
1997年 | 249篇 |
1996年 | 239篇 |
1995年 | 220篇 |
1994年 | 188篇 |
1993年 | 143篇 |
1992年 | 135篇 |
1991年 | 116篇 |
1990年 | 84篇 |
1989年 | 104篇 |
1988年 | 65篇 |
1987年 | 26篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
72.
73.
Construction and relative service is one of the important categories in international service trade set down by WTO. In order to strike a construction agreement, the developed countries and districts have designed a lot of prevailing standard treaty wording, in which FIDIC plays the most important part. We should take advantages of their experience to improve our standard treaty wording. 相似文献
74.
The agent - construction system, as a new public project management mode, has been practiced in some cities and attracted attention from the society. This paper firstly studies the features and operation modes of agent - construction system, and discusses the agent - construction system from the viewpoints of promoting competition, nourishing agent -construction enterprises, setting up a supervisory and encouraging mechanism, and its connection with the governmental project procurement system etc. 相似文献
75.
CHEN Zuo chang 《保鲜与加工》2002,(2):93-97
With social development, the environment has become one of the major topics in human life. Although the construction project may improve economy and environment, it also may exert negative impact on environment. Cost, schedule and quality are three important objectives of construction project and on the objective of environment have not been focused. The author of this paper reiterated the importance of environmental control for the construction project and key areas to be focused on during the whole process of construction project. 相似文献
76.
77.
农业企业的信息化建设过程 总被引:1,自引:0,他引:1
我国农业从传统生产模式向现代市场经济竞争环境下的企业化模式进行转换,依靠的是科学管理和管理科学;建设电子化、信息化的管理系统,是农业企业在市场环境下得以生存的有力支撑.为此,论述了农业企业的信息化建设过程. 相似文献
78.
试论农业机械化在建设社会主义新农村中的重要作用 总被引:1,自引:0,他引:1
建设社会主义新农村,是党中央从贯彻落实科学发展观、构建社会主义和谐社会的全局出发作出的重大战略部署,农业机械化发展必须适应农业现代化和建设社会主义新农村的需要,为我国实现农业现代化、解决“三农”问题,建设社会主义新农村作出农业机械化应有的贡献。 相似文献
79.
介绍了大直径现浇混凝土新型筒桩结构围堤,与目前常用的几种围堤方法相比,从设计计算理论、经济指标、施工特性、结构特性、使用功能、土地利用和环保及景观七个方面进行了比较,突出了该新型堤的优越性,并介绍了该围堤的施工工艺。 相似文献
80.
In this study, the prediction of pine mistletoe distribution in Scots pine ecosystems was explored using remote sensing variables to compare the multilayer perceptron (MLP) artificial neural network (ANN) and logistic regression (LR) model performances. For this purpose, 109 sample plots were distinguished in pure Scots pine forests (natural) in the Eastern Black Sea Region of Turkey. Distinguishing mistletoe-infected stands (69) and uninfected stands (40) was performed with field observations. The variables acquired from Landsat 8 (Level 1) images were used as independent variables for independent-sample t-test, MLP ANN and LR models. Remote sensing variables indicated that mistletoe-infected stands were in drier areas with a lower vegetation-leaf area index. Based on the performance results of both models, the sensitivity (SEN), specificity (SPE), positive predictive value (PPV), negative predictive value (NPV) and accuracy of the MLP ANN model were superior to those of the LR model. The prediction percentages (SEN, SPE, PPV and NPV) of mistletoe-infected stands were better than the prediction percentages of uninfected stands. The prediction accuracies of LR and MLP ANN models were 74.3% and 89.6%, respectively. However, all remote sensing variables were included in the prediction equation of the MLP ANN model, while the thermal infrared 1 (TIRS1) variable was included in the LR model. In the MLP ANN model, the TIRS1 variable also had the highest normalized importance (100%). The area under the curve (AUC) value for identifying the mistletoe-infected stands of Scots pine forests used by the MLP ANN model (0.892 ± 0.034) was higher than in the LR model (0.838 ± 0.039), explaining the more accurate predictions obtained from the MLP ANN model. The MLP ANN model showed much better performance than the LR model. The results of this study are expected to make important contributions to the identification of potential mistletoe-infected areas. 相似文献