全文获取类型
收费全文 | 8527篇 |
免费 | 547篇 |
国内免费 | 998篇 |
专业分类
林业 | 799篇 |
农学 | 780篇 |
基础科学 | 696篇 |
1823篇 | |
综合类 | 3437篇 |
农作物 | 476篇 |
水产渔业 | 438篇 |
畜牧兽医 | 790篇 |
园艺 | 187篇 |
植物保护 | 646篇 |
出版年
2024年 | 68篇 |
2023年 | 217篇 |
2022年 | 388篇 |
2021年 | 451篇 |
2020年 | 420篇 |
2019年 | 483篇 |
2018年 | 305篇 |
2017年 | 462篇 |
2016年 | 575篇 |
2015年 | 457篇 |
2014年 | 455篇 |
2013年 | 581篇 |
2012年 | 748篇 |
2011年 | 658篇 |
2010年 | 485篇 |
2009年 | 457篇 |
2008年 | 383篇 |
2007年 | 426篇 |
2006年 | 316篇 |
2005年 | 255篇 |
2004年 | 217篇 |
2003年 | 163篇 |
2002年 | 160篇 |
2001年 | 126篇 |
2000年 | 119篇 |
1999年 | 106篇 |
1998年 | 74篇 |
1997年 | 53篇 |
1996年 | 78篇 |
1995年 | 61篇 |
1994年 | 55篇 |
1993年 | 51篇 |
1992年 | 55篇 |
1991年 | 34篇 |
1990年 | 37篇 |
1989年 | 36篇 |
1988年 | 21篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1956年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
101.
Studyin g the processin g tech n ology of mak in g holee by laser com plicated sur-face,and developing a CAD/CAM flexible manufacture system. 相似文献
102.
103.
The datum line and mainly three profile height parameters of surface roughness are briefly introduced and the operation principle and system structure of AFM. IPC - 208B with high-resolution, which was successfully developed by Chongqing University, are described in detail, and the emphasis is laid on its application on the nanometer scale surface roughness. Taking stainless steel for example, its micro-structure was observed, and the surface data were analyzed and transacted by special evaluator and the values of three profile height parameters were obtained. Finally the experimental results are briefly analyzed. 相似文献
104.
用ImageWare实现缺损点云的曲面重构 总被引:1,自引:0,他引:1
针对有缺损的点云数据,提出了在逆行工程软件ImageWare平台下进行曲面重构的途径;介绍了运用逆向工程技术进行CAD模型设计的操作流程;用平行面截取点云数据,拟合出曲线线条;通过对曲线条的桥接,利用完整的曲线条重构出曲面。 相似文献
105.
106.
Crop tolerance to land submergence is an important criterion for designing a surface drainage system for agricultural lands. This paper collates the available data from various places in India related to the studies on the submergence tolerance of crops. The paper hypothesizes that a piecewise linear model could be used to describe crop response to land submergence. According to this hypothesis, there would be no yield decline for a few initial days of submergence. If submergence continues beyond this period then there would be linear decline in yield. The unknown parameters in the model are: optimum yield, threshold time and the slope which represents the per cent yield reduction per day of additional submergence beyond the threshold.Data in respect of wheat, pigeon peas, cowpeas, pearlmillet, maize and groundnuts indicate that the model describes the data well, although in many cases the threshold is 0.0. The yield reduction varies from 5.3 to 23.2% for each day of submergence beyond the threshold. It appears that to allow for more than 1–2 days of submergence will result in more than 10% reducation in yield of dryfoot crops. For the maize crop, the seedling stage is the most sensitive stage followed by the silking stage. The grain formation stage is the least sensitive, although even at this stage the threshold is 0.0 and yield reduction is 9.3% for each day of submergence beyond the threshold. The data for 9 test crops from Texas and Venezuela were well described by the model. It is concluded that the piecewise linear model is a useful tool for describing submergence tolerance of crops and for working out surface drainage requirements for a given level of yield reduction. Frequency analysis of the daily rainfall data from some selected locations indicates that there is every likelihood of submergence at most of the stations. It is suggested that there is an urgent need for developing wet farming techniques analogous to dry farming techniques. 相似文献
107.
108.
109.
在水泵制造企业中应用成组技术 总被引:1,自引:0,他引:1
通过水泵生产企业现状的调查分析,在为某水泵厂开发计算机辅助企业现代化管理系统的基础上,提出了水泵生产企业运用成组技术,强化企业内部管理的内容和方法。 相似文献
110.