全文获取类型
收费全文 | 4601篇 |
免费 | 244篇 |
国内免费 | 182篇 |
专业分类
林业 | 717篇 |
农学 | 227篇 |
基础科学 | 252篇 |
381篇 | |
综合类 | 2131篇 |
农作物 | 250篇 |
水产渔业 | 297篇 |
畜牧兽医 | 487篇 |
园艺 | 181篇 |
植物保护 | 104篇 |
出版年
2024年 | 19篇 |
2023年 | 73篇 |
2022年 | 119篇 |
2021年 | 164篇 |
2020年 | 167篇 |
2019年 | 200篇 |
2018年 | 76篇 |
2017年 | 148篇 |
2016年 | 204篇 |
2015年 | 218篇 |
2014年 | 349篇 |
2013年 | 394篇 |
2012年 | 473篇 |
2011年 | 450篇 |
2010年 | 353篇 |
2009年 | 308篇 |
2008年 | 225篇 |
2007年 | 230篇 |
2006年 | 178篇 |
2005年 | 147篇 |
2004年 | 113篇 |
2003年 | 92篇 |
2002年 | 53篇 |
2001年 | 48篇 |
2000年 | 36篇 |
1999年 | 31篇 |
1998年 | 31篇 |
1997年 | 29篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有5027条查询结果,搜索用时 140 毫秒
931.
黎意慧 《农业图书情报学刊》2007,19(12):70-72,75
通过对本馆科技期刊利用情况的历史记录进行统计调查,发现教师读者对科技期刊利用率偏低,同时揭示了原因,并提出了提高科技期刊教师读者利用率的几点发展对策。 相似文献
932.
[目的]厘清甘肃省农作物秸秆资源现状,可为减少农业面源污染,促进全省秸秆综合利用和农业可持续发展提供数据支撑。[方法]本文基于统计数据和农户调研数据,综述了全省主要农作物秸秆资源产生量、利用现状、秸秆资源量评估的主要影响因素及利用模式建议。分析了秸秆资源量变化趋势(2007-2017年);[结果]2017年甘肃省农作物秸秆理论资源量为1040.03万吨,可收集量923.62万吨,小麦、玉米、大豆三类农作物秸秆占总量的87.33%,利用量为829.79万吨,综合利用率达89.84%,资源化利用方式以饲料化为主,肥料化为辅。秸秆主要利用方式包括秸-饲-肥饲料化利用、 秸-菌-肥基料化利用、秸-沼-肥燃料化利用、秸-炭-肥原料化利用。[结论]以循环农业的角度出发,秸秆炭化还田作为一种重要的秸秆利用方式之一,具有培肥地力、固氮减排、间接增产增收等积极效用,可作为现有基础下秸秆资源化利用的一条重要的可行性新途径,对于资源短缺、环境污染和农业可持续发展具有重要意义。 相似文献
933.
通过野外调查和采集植物标本,调查沙河水库正常水位外50m范围内的植被现状。结果表明,沙河水库植物种类较丰富,以次生林和人工林为主,共有植物70科,253种。其中蕨类植物有7科,9种;被子植物有63科,244种。但部分地段的植被由于人类活动的干扰,破坏较严重,优势野生植物种类不多,且日趋减少。对此,有关部门应高度重视,及早采取有效措施保护沙河水库植被。 相似文献
934.
《Soil Science and Plant Nutrition》2013,59(5):698-704
Abstract A salt-sensitive cucumber cultivar “Jinchun No. 2” (Cucumis sativus L.) was used to investigate the role of proline in alleviating salt stress in cucumber. Proline was applied twice (day 0 and day 4 after salt treatment) as a foliar spray, with a volume of 25?mL per plant at each time. Plant dry weight, leaf relative water content, proline, malondialdehyde (MDA), Na+, K+ and Cl? contents, as well as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) activities in the plants were determined at day 8 after salt treatment. The results showed that 100?mmol?L–1 NaCl stress significantly decreased plant dry weight, leaf relative water and K+ contents, and increased leaf MDA, Na+ and Cl? contents and SOD, POD, CAT and APX activities. However, leaf proline accumulation was not affected by salinity. The exogenous application of proline significantly alleviated the growth inhibition of plants induced by NaCl, and was accompanied by higher leaf relative water content and POD activity, higher proline and Cl? contents, and lower MDA content and SOD activity. However, there was no significant difference in Na+ and K+ contents or in CAT and APX activities between proline-treated and untreated plants under salt stress. Taken together, these results suggested that the foliar application of proline was an effective way to improve the salt tolerance of cucumber. The enhanced salt tolerance could be partially attributed to the improved water status and peroxidase enzyme activity in the leaf. 相似文献
935.
In a three-year field experiment in Toulouse (in Southwest France), two indicators of plant nitrogen (N) status were compared on five durum wheat cultivars: the normalized SPAD index and the nitrogen nutrition index (NNI). SPAD value is a non-destructive measurement of chlorophyll content from the last expanded leaf. The normalized SPAD index is expressed relative to SPAD reading on a fully fertilized crop. The NNI is calculated from the crop biomass and total plant N content using a universal N-dilution curve for wheat. The normalized SPAD index and NNI were closely related irrespective of year, cultivar, and growth stage. When N was a limiting factor, the SPAD index measured at anthesis predicted grain yield and protein content accurately. Unlike NNI, SPAD index cannot be used to predict these variables when wheat is over-fertilized. 相似文献
936.
Characteristics of mineral elements in plants are often strongly influenced by species' abundance and heterogeneous habitats. Therefore, nutrient analysis, after excluding interference of habitat heterogeneity, would directly reflect genetic traits of species in the community. From another aspect, knowledge of responses of species to environmental variation would be helpful in the management of natural and man-made ecosystems, especially those containing rare and endangered plants conserved in gardens. We studied the characteristics of twelve nutrient elements in 90 species in Wuhan Botanical Garden (WBG) and provided explanations of their survival status. Concentrations of the 12 nutrients in the artificial garden were consistent with those in other natural communities in the subtropical zone of China. Features of nutrient-limited at the community level were also consistent with the regional characteristics (N:P ratio being 9.79 ± 3.22, as exhibiting N-limited). The Ca + Mg concentrations differed between evergreen and deciduous species. The 90 species were clustered into various functional nutrition groups. The artificial community of the garden was a “sick” one relative to natural ones with wholesome ecological functions. The proportion of element-pairs with significant correlations (P < 0.01 or P < 0.05) to total element-pairs was only 24.2%, being lower than that of species in the natural community, This suggests that the harmonious relationship among nutrient elements in these species was yet to be achieved. Correlation analysis between survival status of the 90 species and their foliar nutrient ratios were positive for nitrogen (N), phosphorus (P), potassium (K), iron (Fe), zinc (Zn), copper (Cu), and sodium (Na), but negative for calcium (Ca), magnesium (Mg), manganese (Mn), and aluminum (Al). Cluster analysis suggested that, among 23 species with the poorest survival status, 21 species had higher Ca and Mg, but lower N and P concentrations. 相似文献
937.
2007-2009年连续3年应用探照灯诱虫器和佳多自动虫情测报灯,并结合雌蛾卵巢解剖对稻纵卷叶螟种群进行了监测.结果表明:探照灯诱虫器能有效监测稻纵卷叶螟种群动态,其数量变化规律与佳多测报灯灯下虫量变化规律基本一致,监测峰次多于佳多灯.探照灯诱虫器对稻纵卷叶螟的诱蛾量显著高于佳多灯,且对起飞迁出、过境、迁入降落虫群均具有较强诱捕作用.据此提出了以探照灯诱虫器、佳多测报灯诱虫突增情况和雌蛾卵巢解剖情况为标准的探照灯诱虫器诱蛾虫源性质判断方法,并以此方法,对探照灯诱虫器诱捕迁入、过境和迁出稻纵卷叶螟进行了个例分析. 相似文献
938.
939.
940.
杭州市茶馆消费情况调查分析 总被引:2,自引:0,他引:2
通过问卷调查与统计分析相结合的方式对杭州市民喜爱的茶馆类型、茶馆吸引消费者的因素、消费茶类结构、消费目的、消费者满意度等方面进行了分析和总结。结果显示,目前市区、农家、风景区三种茶馆类型,各自占有一定的市场份额,自助茶馆相对于清茶馆更受欢迎。消费者对茶馆环境的要求很高。绿茶在消费中仍然占据主导地位。消费者的消费目的以自我放松和亲友聚会为主。认为茶馆价格不合理的消费者比例约为20%,认为物有所值的接近50%。大多数人对杭州茶馆的现状表示满意和基本满意。 相似文献