全文获取类型
收费全文 | 8658篇 |
免费 | 246篇 |
国内免费 | 745篇 |
专业分类
林业 | 96篇 |
农学 | 2259篇 |
基础科学 | 506篇 |
727篇 | |
综合类 | 4166篇 |
农作物 | 593篇 |
水产渔业 | 51篇 |
畜牧兽医 | 183篇 |
园艺 | 327篇 |
植物保护 | 741篇 |
出版年
2024年 | 44篇 |
2023年 | 129篇 |
2022年 | 188篇 |
2021年 | 253篇 |
2020年 | 217篇 |
2019年 | 279篇 |
2018年 | 245篇 |
2017年 | 271篇 |
2016年 | 356篇 |
2015年 | 293篇 |
2014年 | 390篇 |
2013年 | 386篇 |
2012年 | 537篇 |
2011年 | 587篇 |
2010年 | 489篇 |
2009年 | 521篇 |
2008年 | 439篇 |
2007年 | 447篇 |
2006年 | 433篇 |
2005年 | 394篇 |
2004年 | 342篇 |
2003年 | 271篇 |
2002年 | 301篇 |
2001年 | 233篇 |
2000年 | 218篇 |
1999年 | 194篇 |
1998年 | 180篇 |
1997年 | 169篇 |
1996年 | 149篇 |
1995年 | 120篇 |
1994年 | 112篇 |
1993年 | 102篇 |
1992年 | 114篇 |
1991年 | 61篇 |
1990年 | 62篇 |
1989年 | 43篇 |
1988年 | 32篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1963年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有9649条查询结果,搜索用时 15 毫秒
131.
Waseem Akbar Anilkumar Gowda Jeffrey E Ahrens Jason W Stelzer Robert S Brown Scott L Bollman John T Greenplate Jeffrey Gore Angus L Catchot Gus Lorenz Scott D Stewart David L Kerns Jeremy K Greene Michael D Toews David A Herbert Dominic D Reisig Gregory A Sword Peter C Ellsworth Larry D Godfrey Thomas L Clark 《Pest management science》2019,75(3):867-877
132.
QianBing ZHANG Ling YANG ZhenZhu XU YaLi ZHANG HongHai LUO Jin WANG WangFeng ZHANG 《干旱区科学》2014,(4):468-477
Changes in both soil organic C storage and soil respiration in farmland ecosystems may affect atmospheric CO2 concentration and global C cycle. The objective of this field experiment was to study the effects of three crop field management practices on soil CO2 emission and C balance in a cotton field in an arid region of Northwest China. The three management practices were irrigation methods(drip and flood), stubble managements(stubble-incorporated and stubble-removed) and fertilizer amendments(no fertilizer(CK), chicken manure(OM), inorganic N, P and K fertilizer(NPK), and inorganic fertilizer plus chicken manure(NPK+OM)). The results showed that within the C pool range, soil CO2 emission during the whole growing season was higher in the drip irrigation treatment than in the corresponding flood irrigation treatment, while soil organic C concentration was larger in the flood irrigation treatment than in the corresponding drip irrigation treatment. Furthermore, soil CO2 emission and organic C concentration were all higher in the stubble-incorporated treatment than in the corresponding stubble-removed treatment, and larger in the NPK+OM treatment than in the other three fertilizer amendments within the C pool range. The combination of flood irrigation, stubble incorporation and application of either NPK+OM or OM increased soil organic C concentration in the 0-60 cm soil depth. Calculation of net ecosystem productivity(NEP) under different management practices indicated that the combination of drip irrigation, stubble incorporation and NPK+OM increased the size of the C pool most, followed by the combination of drip irrigation, stubble incorporation and NPK. In conclusion, management practices have significant impacts on soil CO2 emission, organic C concentration and C balance in cotton fields. Consequently, appropriate management practices, such as the combination of drip irrigation, stubble incorporation, and either NPK+OM or NPK could increase soil C storage in cotton fie 相似文献
133.
江西棉铃虫综合治理措施 总被引:1,自引:0,他引:1
江西省棉铃虫猖獗成因及治理措施的研究课题组 《江西植保》1999,(1):1-3
近几年来江西棉铃虫几乎年年大发生。本文提出适合江西棉区推广应用的棉铃虫综合治理措施,包括种植抗虫棉、农业防治、化学防治等。冬耕、中耕和灌水灭蛹,整枝灭卵,杨柳枝把或高压汞灯诱蛾都是有效的综防措施。防治策略、防治指标和施药技术是化学防治的关键。 相似文献
134.
135.
136.
137.
提出一种基于静电吸附方法分级去除机采棉中残地膜的方法,以新疆阿拉尔地区种植的新陆早26号机采棉为研究对象,根据机采棉中残地膜曲直形态与荷电极化程度存在一定的相关性,利用图像处理提取机采棉中各种残地膜杂质特征并进行聚类算法分级,将残地膜分成Ⅰ、Ⅱ、Ⅲ等级。搭建静电吸附分离平台,对掺有不同等级残地膜的机采棉进行不同荷电时间、飞入速度、极板电压下的试验,以除杂率为测定指标,找出对应级别残地膜的最佳参数组合,以期达到残地膜杂质与机采棉的分离最大化。试验表明,对除杂率影响显著的因素由大到小为:飞入速度、荷电时间、极板电压。掺有Ⅰ级残地膜的机采棉除杂最佳荷电时间为24 s,飞入速度为4. 7 m/s,极板电压为39 k V,分离率为96. 2%;Ⅱ级最佳荷电时间为29. 8 s,飞入速度为5. 8 m/s,极板电压为37. 6 k V,分离率为98. 1%;Ⅲ级最佳荷电时间为30. 1 s,飞入速度为3. 5 m/s,极板电压为46. 2 k V,分离率为97. 2%。研究结果表明:基于静电吸附分级去除残地膜的方法可行,能够满足实际生产需要。 相似文献
138.
基于结构光三维点云的棉花幼苗叶片性状解析方法 总被引:1,自引:0,他引:1
针对传统的棉花叶片表型测量方法主观、低效,对复杂性状如卷叶程度、黄叶占比等很难量化的问题,提出一种基于结构光三维成像的棉花幼苗叶片性状解析方法。首先,采用结构光扫描仪获取棉花幼苗的三维点云数据;然后,利用直通滤波、超体聚类、条件欧氏距离算法,实现叶片点云的识别与分割;最后,基于分割的叶片点云,采用三角面片化、随机采样一致性、Lab颜色分割等处理,实现叶片面积、周长、生长角度、卷曲度、黄叶占比等参数的快速、准确、无损提取。对40株棉花幼苗进行三维结构光成像试验,结果表明,3D叶片面积、周长测量的平均绝对误差分别为2. 59%、2. 85%,具有较高的测量精度,还证明叶片卷曲度和黄叶占比能显著区分病叶和正常叶。 相似文献
139.
对2016-2017年引进的62个陆地棉新品种进行了形态特征、生物学特性和品质特性的鉴定及分析。结果表明:目前收集的新材料以中早熟棉为主,铃重以中等大小为主,衣分中等,悬殊较大,马克隆数值普遍偏大。 相似文献
140.
Zira Mavunganidze Ignacio Casper Madakadze Justice Nyamangara Paramu Mafongoya Nester Mashingaidze 《Weed Research》2020,60(5):334-342
Understanding drivers of weed density and diversity is essential for the development of weed management strategies. Here, we compared temporal changes in weed density and diversity under no-till (NT) and conventional (CONV) tillage systems in cotton–maize rotations on loam, clay loam and sandy loam soils immediately after transition to NT in Kadoma, Zimbabwe. The effect of tillage system on weed density varied through the growth season and was dependent upon soil type and species composition of the weed community. Although weed responses to tillage system varied amongst species, we identified general trend effects on weed density on specific soils. At 3 weeks after crop emergence (WACE), weed density on loam soils was 76% and 96% higher in NT than in CONV during the 2009/2010 and 2010/2011 seasons, respectively, and on clay loam soils it was 37% and 33% higher in NT than CONV, respectively. Weed densities in NT and CONV were similar across all soil types at 6 WACE during the 2009/2010 and 2010/2011 seasons and at 9 WACE in 2009/2010. Tillage system did not affect weed density during the growth season on sandy loam soils. Weed diversity (Shannon index) was at least 75% higher in NT than CONV on loam and clay loam soils at 3 WACE during both seasons. It is likely these increases in weed densities following conversion to NT will exacerbate already prevalent weed management problems in the smallholder sector. Earlier weeding is recommended to suppress weed emergence and reduce likely associated crop yield losses. 相似文献