全文获取类型
收费全文 | 15601篇 |
免费 | 1019篇 |
国内免费 | 1482篇 |
专业分类
林业 | 1441篇 |
农学 | 1202篇 |
基础科学 | 690篇 |
1577篇 | |
综合类 | 7377篇 |
农作物 | 1261篇 |
水产渔业 | 699篇 |
畜牧兽医 | 2039篇 |
园艺 | 1041篇 |
植物保护 | 775篇 |
出版年
2024年 | 70篇 |
2023年 | 265篇 |
2022年 | 661篇 |
2021年 | 677篇 |
2020年 | 650篇 |
2019年 | 678篇 |
2018年 | 475篇 |
2017年 | 720篇 |
2016年 | 505篇 |
2015年 | 776篇 |
2014年 | 802篇 |
2013年 | 932篇 |
2012年 | 1298篇 |
2011年 | 1221篇 |
2010年 | 1246篇 |
2009年 | 1104篇 |
2008年 | 1076篇 |
2007年 | 964篇 |
2006年 | 804篇 |
2005年 | 717篇 |
2004年 | 444篇 |
2003年 | 308篇 |
2002年 | 422篇 |
2001年 | 371篇 |
2000年 | 327篇 |
1999年 | 137篇 |
1998年 | 62篇 |
1997年 | 58篇 |
1996年 | 45篇 |
1995年 | 51篇 |
1994年 | 40篇 |
1993年 | 43篇 |
1992年 | 30篇 |
1991年 | 29篇 |
1990年 | 27篇 |
1989年 | 26篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1956年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Rui Fang Wang Feng Lan Huang Jian Zhang Qiu Yan Zhang Li Na Sun Xing Shun Song 《Journal of Forest Research》2016,21(5):244-250
Cerasus humilis is a species of small, perennial, drought-resistant and multipurpose deciduous shrub grown in arid and semi-arid conditions in northern China. In this study, an efficient protocol for the rapid micropropagation of C. humilis has been standardized using stem and/or leaf explants. Direct multiple shoot induction was observed when the stem explants were cultured on Murashige and Skoog (MS) medium supplemented with different plant growth regulators. The highest shoot induction was obtained when stem explants from adult trees were cultured on MS medium supplemented with 2.0 mg L?1 6-benzyladenine (6-BA) and 0.9 mg L?1 α-naphthaleneacetic acid (NAA). The leaf and stem explants cultured on MS medium with 1.0 mg L?1 6-BA and 0.6 mg L?1 NAA, and 0.5 mg L?1 6-BA and 0.8 mg L?1 NAA, respectively, produced the highest induction frequency of callus. Maximum proliferation of callus was observed on MS medium containing a combination of 0.5 mg L?1 6-BA with 0.6 mg L?1 2,4-dichlorophenoxyacetic acid (2,4-d). Optimal shoots differentiated from callus were obtained on MS medium supplemented with 5.0mg L?1 6-BA and 0.9 mg L?1 NAA. In vitro rooting was achieved on half-strength (1/2) MS medium containing 0.5 mg L?1 NAA. Rooted plantlets were hardened under control conditions and successfully acclimatized under field conditions. 相似文献
993.
994.
995.
The effects of thermo-mechanical refining conditions on the properties of medium density fiberboard (MDF) made from black
spruce (Picea mariana) bark were evaluated. The bark chips were refined in the MDF pilot plant of Forintek Canada Corporation under nine different
refining conditions in which preheating retention time was adjusted from 3 to 5 to 7 min and steam pressure was set at either
0.6, 0.9 or 1.2 MPa. The resulting bark fibers were blended with 12% UF resin (based on oven-dry fiber weight) using a mechanical
blender. The resinated fibers were manually formed into fiber mats and hot-pressed into MDF panels using consistent parameters.
Two panels for each refining condition were produced, resulting in a total of 18 panels. Analysis of variance (ANOVA) was
used to analyze the significance of factors. Regression coefficients and 3D contour plots were used to quantify the relationship
between panel properties and the two test factors. The results from this study indicated that the preheating retention time
was a significant factor for both modulus of rupture (MOR) and modulus of elasticity (MOE), the steam pressure was a significant
factor for internal bond strength (IB), MOR and MOE, whereas both factors were insignificant for thickness swelling, water
absorption and linear expansion. The properties of MDF panels were quadratic functions of retention time and steam pressure.
Compared to the ANSI standard for 120-grade MDF, most panels with a nominal density of 950 kg/m3 had very high IB (>1 MPa) and acceptable MOR, MOE and dimension stabilities. These results suggest that black spruce bark
residues can be considered as a potentially suitable raw material for manufacturing MDF products. 相似文献
996.
Richards林木生长模型及其适用性 总被引:3,自引:0,他引:3
该文简述了Richards生长方程的可塑性,以毛白杨、华北落叶松、刺槐与斑克松的生长资料,讨论了描述林木生长过程的适用性。 相似文献
997.
998.
对广州市主导森林生态效益进行了影子价格评价,得出结论:目前广州市的森林生态效益补偿额的计量和实施存在着不合理现象。在此基础上提出了森林生态效益补偿额制定和补偿实施的四点建议,对促进我国森林生态效益补偿办法的改革具有积极作用。 相似文献
999.
银杏雄株开花生物学特性的研究 总被引:17,自引:0,他引:17
对从泰安和郯城共5050株银杏雄株中筛选出的26个优良单株的开花生物学特性进行了研究。这些单株具有花期长、花粉量大及花粉生活力强等特点。相关分析和方差分析结果表明,随海拔高度的增加,花期逐渐延长,但小孢子叶球数/短枝下降。每米长枝上的短枝数最高达45个。短枝长与小孢子叶球数/短枝呈极呈著的正相关。3年生枝段短枝开花率最高,达96%。每个短枝上小孢子叶球数最高达645个,每个小孢子叶球最多含花药58个,每个花药含有花粉粒最高达23×104个,平均每个小孢子叶球含花粉粒达65×104个。14#单株出粉率达683%。一株45年生雄株可产花粉165g。花粉生活力平均为92%。授粉后座果率90%,有胚率91%。 相似文献
1000.
通过对不同建设时期居住区的调查以及发展历程的论述,分析总结了各个时期深圳居住区园林植物配置特点.以此了解深圳居住区绿地园林植物配置的现状与存在问题,探讨深圳居住区园林植物配置特色,并为其今后的建设发展提出建议与对策. 相似文献