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81.
82.
本文分析了目前乡镇农机站存在的困难。从基层农机工作者的角度提出了具体对策以及远期发展的思考。 相似文献
83.
84.
目前常规RTK技术在测区情况复杂的条件下时常遇到作业距离短、流动站失锁频繁、架设基准站次数多的问题,造成作业效率低下,不能充分发挥RTK技术的特色。基于网络基站的RTK技术是GPS-RTK技术的进一步延伸,其通过互联网接入的通讯方式向流动站传送参考站数据,采用网络通讯大大延伸了RTK的作业半径,扩展其作业范围,并将定位精度和可靠性进一步提高。以十漫高速公路土地登记测量项目为例,通过作业流程和数据精度分析表明,网路基站技术比常规RTK技术更加优越,从而为类似工程线性测量工作开辟了新的途径。 相似文献
85.
文章介绍了张河湾抽水蓄能电站转子结构特点及安装工艺,分析了转子安装过程中出现的磁轭冲片受损、拉紧度不够等原因及解决办法,介绍了如何解决安装过程中分块式压板的水平度调整。 相似文献
86.
基于ARCENGINE空间分析的林业区划界线自动提取方法 总被引:1,自引:0,他引:1
使用ARCENGINE的空间分析接口,编程实现林业区划界线的自动提取。与传统方法相比,该方法极大地提高了林业区划界线提取的效率和准确度,且自动化程度高,极易推广。 相似文献
87.
燃气轮机驱动压气站的设备维护费用较高,现行的基于时间的维护策略存在一些缺陷,可以借助以可靠性为中心的维护思想,降低维护成本。结合相关理论及燃气轮机驱动压缩机组的实际运行维护情况,提出依据以可靠性为中心的维护理论及相关分析方法,优化现有维护大纲,使该理论为实际设备的管理活动服务。以压气站燃气轮机进气滤芯为例,进行故障危害性分析、故障后果分析、故障模型分类、性能参数预测,优化维护大纲,包括将多项原有维护项目的时间推后;将多项原有的定时维护内容删除,改为事后或视情维护;新增对现有测点数据的分析,最终实现在保证设备可靠性的基础上,简化维护、节约成本的目的。 相似文献
88.
Junzeng Xu Weiguang Wang Shihong Yang Qi Wei Yufeng Luo 《Archives of Agronomy and Soil Science》2013,59(11):1487-1501
Prediction of daily reference evapotranspiration (ET 0) is the basis of real-time irrigation scheduling. A multiple regression method for ET 0 prediction based on its seasonal variation pattern and public weather forecast data was presented for application in East China. The forecasted maximum temperature (T max), minimum temperature (T min) and weather condition index (WCI) were adopted to calculate the correction coefficient by multilinear regression under five time-division regimes (10 days, monthly, seasonal, semi-annual and annual). The multiple regression method was tested for its feasibility for ET 0 prediction using forecasted weather data as the input, and the monthly regime was selected as the most suitable. Average absolute error (AAE) and root mean square error (RMSE) were 0.395 and 0.522 mm d?1, respectively. ET 0 prediction errors increased linearly with the increase in temperature prediction error. A temperature error within 3 K is likely to result in acceptable ET 0 predictions, with AAE and average absolute relative error (AARE) <0.142 mm d?1 and 5.8%, respectively. However, one rank error in WCI results in a much larger error in ET 0 prediction due to the high sensitivity of the correction coefficient to WCI and the large relative error in WCI caused by one rank deviation. Improving the accuracy of weather forecasts, especially for WCI prediction, is helpful in obtaining better estimations of ET 0 based on public weather data. 相似文献
89.
R. A. Daamen W. Stol 《European journal of plant pathology / European Foundation for Plant Pathology》1990,96(5):251-260
In the period 1974–1986, ca. 100 commercial winter wheat fields were surveyed annually for stembase diseases. In these years, on average 6% of the tillers was infected with eyespot in spring at the first-second, node stage. Eyespot intensity in spring was high in years with high temperature during winter. Eyespot, intensity in the milky-ripe stage in July, averaged 13% of the culms and was high in years with high temperature in April and high precipitation in March, April and May. These data may improve forecasts.In the milky-ripe stage, 2% of the culms were infected with sharp eyespot, but its intensity has gradually increased during the survey years. No significant correlation of sharp eyespot intensity with dry periods in autumn, spring or summer was found.Symptoms of take-all were found on 0.2% of the stem-bases during ripening. Its intensity was low in years with high precipitation in March, April, May and June and high temperature in May and June.Samenvatting Een honderdtal percelen wintertarwe werd in 1974–86 jaarlijks op voetziekten geïnventariseerd. In het voorjaar, tijdens het, eerste en tweede knoopstadium van het gewas, was gemiddeld 6% van de spruiten aangetast door oogvlekkenziekte. De intensiteit van de ziekte was hoog in jaren met een hoge gemiddelde wintertemperatuur. Tijdens het melkrijpe stadium, in juli was gemiddeld 13% van de halmen aangetast door oogvlekkenziekte. De aantasting in juli was hoog in jaren met een hoge temperatuur in april en veel neerslag in de maanden maart, april en mei. Met deze gegevens kunnen adviessystemen worden verbeterd.Scherpe oogvlekkenziekte was op gemiddeld 2% van de halmen in juli aanwezig. De ziekte nam geleidelijk met de jaren toe. De jaarlijkse intensiteit was niet gecorreleerd met droge perioden in de herfst, voorjaar of zomer.Symptomen van halmdoder waren op gemiddeld 0.2% van de halmen aanwezig. De intensiteit van de ziekte was hoog in jaren met weinig neerslag in maart, april, mei en juni en met een lage temperatuur in mei en juni. 相似文献
90.
Surveys of cereal diseases and pests in the Netherlands. 4. Occurrence of powdery mildew and rusts in winter wheat 总被引:1,自引:0,他引:1
R. A. Daamen R. W. Stubbs W. Stol 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(5):301-312
Results of annual surveys of winter wheat fields from 1974 to 1986 were compiled to describe epidemics of powdery mildew and rusts in relation to weather and cultivar resistance.An average of 29 and 70% of fields were infected by powdery mildew in May and July, respectively. Mildew prevalence in May was positively correlated with average temperature in October and with average temperature over the months December, January, February and March. In addition, it was correlated negatively with the average grade of mildew resistance of the cultivars sown each year. Prevalence of mildew in July did not show consistent correlations with weather characteristics nor with mildew prevalence in May.Yellow rust was usually not detected in May and on average 18% of the fields was infected in July. The occurrence of yellow rust decreased after 1977, when the farmers adopted cultivars resistant or moderately resistant to yellow rust.Brown rust was usually not detected in May, while in July on average 48% of the fields was infected. Brown rust intensity in July was high in years with a high March temperature and high precipitation during April and May.Black rust was rare in the Netherlands, with 3 and 1% of the fields infected in July 1977 and 1981, respectively. 相似文献