全文获取类型
收费全文 | 6841篇 |
免费 | 352篇 |
国内免费 | 513篇 |
专业分类
林业 | 1624篇 |
农学 | 636篇 |
基础科学 | 313篇 |
564篇 | |
综合类 | 2995篇 |
农作物 | 529篇 |
水产渔业 | 56篇 |
畜牧兽医 | 253篇 |
园艺 | 404篇 |
植物保护 | 332篇 |
出版年
2024年 | 34篇 |
2023年 | 95篇 |
2022年 | 189篇 |
2021年 | 207篇 |
2020年 | 218篇 |
2019年 | 271篇 |
2018年 | 157篇 |
2017年 | 305篇 |
2016年 | 382篇 |
2015年 | 300篇 |
2014年 | 470篇 |
2013年 | 380篇 |
2012年 | 585篇 |
2011年 | 508篇 |
2010年 | 416篇 |
2009年 | 397篇 |
2008年 | 332篇 |
2007年 | 364篇 |
2006年 | 274篇 |
2005年 | 257篇 |
2004年 | 200篇 |
2003年 | 172篇 |
2002年 | 125篇 |
2001年 | 151篇 |
2000年 | 114篇 |
1999年 | 109篇 |
1998年 | 99篇 |
1997年 | 95篇 |
1996年 | 76篇 |
1995年 | 80篇 |
1994年 | 69篇 |
1993年 | 42篇 |
1992年 | 51篇 |
1991年 | 59篇 |
1990年 | 37篇 |
1989年 | 23篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 4篇 |
1955年 | 1篇 |
排序方式: 共有7706条查询结果,搜索用时 15 毫秒
61.
62.
樟子松容器苗造林是一项实用高效的林业造林生产技术,对半干旱固定沙地较为适宜。文章介绍了樟子松容器育苗技术及容器苗造林技术,旨在提高樟子松育苗成活率,并在当地推广此项技术。 相似文献
63.
64.
Field experiments were conducted over two growing seasons to investigate the effects of variations in water regime and planting pattern on the growth of rice plant roots and shoots and on yield. Four water regimes were evaluated with split plot design: intermittent flooding during the vegetative stage only (IF‐V); intermittent flooding extending into the reproductive stage (IF‐R); not flooded (NF); and continuously flooded (CF), interacting with three different planting patterns: single seedling per hill with wider 30 × 30 cm spacing (P1); single seedling per hill with closer 20 × 20 cm spacing (P2); and three to four seedlings per hill with 20 × 20 cm spacing (P3). The treatment combination CF/P3 corresponds most closely with current conventional practice. The other combinations were evaluated to contribute to a better understanding of the effects of the two parameters studied, respectively and together. IF‐V/P1 was considered as an approximation of System of Rice Intensification (SRI) practice. This study found that the combination of singly transplanted seedlings, both P1 and P2, with the IF‐V water regime improved root length density, root physiological activity, and chlorophyll content of the upper and lower leaves, leading to higher grain yield compared with the other treatment combinations. With continuous flooding (CF), P2 gave 23 % more yield compared with the P3 planting pattern. Combining IF‐V and P2 produced 32 % more grain yield compared with the CF/P3 treatment. These results showed a synergistic effect on grain yield from reduced intra‐hill competition and IF‐V water management. In these trials, there was no significant yield difference between the IF‐V/P1 and CF/P3 treatments. Wider spacing improved the performance of individual hills when grown under IF‐V water regimes, but tiller number per unit area remained a dominant determinant of yield. The yield reduction observed for CF/P1 compared with CF/P3 indicated that in more hypoxic CF soils, denser plant populations can produce more than sparser ones, whereas the latter benefit from more aerobic soil conditions. Intermittent irrigation during the vegetative growth stage and transplanting single seedlings/hill are major elements of SRI methodology. These findings contribute to an understanding of why SRI methods can produce the higher yields reported. A consideration of the effects of interaction between planting pattern and water regime shows the need to establish empirically the optimum values for these treatments according to varietal, soil and climatic characteristics for the greatest yield response. 相似文献
65.
苗木切根技术研究进展 总被引:5,自引:0,他引:5
精准培育的理念已经渗入到森林培育的各个环节。切根作为干扰根系最为重要的技术,也受到越来越多地重视。切根可以划分为芽苗切根、苗期切根和起苗后切根等3种类型,把平截、扭根、侧方修根、盒式修根等称为苗期切根,是狭义切根范畴。结合苗木形态指标、生理指标和造林效果,综述每一类型的切根对苗木质量和造林效果的影响。以辐射松为代表的主根发达树种,通过芽苗切根、苗期的平截和扭根,抑制根系顶端优势,从而降低苗木高生长,促进侧根发育,形成发达、紧凑的根系,调整苗木地上和地下比例,最终提高苗木造林效果。以花旗松为代表的慢生常绿树种,侧根较为发达,切根效果不一。苗木平截和扭根后,内源激素、矿质营养、碳水化合物、水分等均会发生变化,这种变化如何影响苗木质量的机制尚不明确。 相似文献
66.
花生组培苗嫁接技术的研究 总被引:5,自引:0,他引:5
为解决花生组培再生苗及转基因苗驯化移栽成活率低的难题,本试验以花生实生苗作为砧木,对花生嫁接技术进行了研究。试验结果表明:超净台内无菌嫁接效果较好,以再生苗或实生苗为接穗进行无菌嫁接,其成活率均达90%以上,明显高于室内嫁接成活率(71%~72%);无菌嫁接时12~15d苗龄的砧木效果最好;将无菌嫁接苗在培养基中培养3~5d后进行驯化移栽为最佳时期;不同花生基因型嫁接苗成活率在87%~95%;嫁接苗移栽田间后,其成活率高达94%,且100%结果。 相似文献
67.
68.
69.
《Communications in Soil Science and Plant Analysis》2012,43(7):768-777
The aims of this work are to test whether boron (B) may alleviate soil acidification and aluminum (Al) phytotoxicity to rape (Brassica napus L.) in acidic soil. The Al hydroxide that reacted with borax was called ad-B-Al hydroxide. Point of zero charge (PZC) of Al hydroxide (pH 4.86) was greater than that of ad-B-Al hydroxide (pH 4.68). Compared with the control, ad-B-Al hydroxide raised the soil pH significantly by 0.10 pH units. Rape was planted in the control soil, the soil treated with Al hydroxide, and the soil treated with ad-B-Al hydroxide. It was found that the B content of the soil and rape seedlings grown on the soil treated with ad-B-Al hydroxide was greater than the others. Biomass production of rape seedlings grown in the soil treated with ad-B-Al hydroxide was significantly increased compared to that in the others. These demonstrated that ad-B-Al hydroxide can be an important source of B for plants and alleviate acidity of acidic soils because it can decrease exchangeable acid and Al toxicity in soil significantly. 相似文献
70.