全文获取类型
收费全文 | 7478篇 |
免费 | 50篇 |
国内免费 | 14篇 |
专业分类
林业 | 729篇 |
农学 | 235篇 |
基础科学 | 49篇 |
919篇 | |
综合类 | 333篇 |
农作物 | 507篇 |
水产渔业 | 461篇 |
畜牧兽医 | 3602篇 |
园艺 | 201篇 |
植物保护 | 506篇 |
出版年
2022年 | 12篇 |
2019年 | 10篇 |
2018年 | 120篇 |
2017年 | 187篇 |
2016年 | 170篇 |
2015年 | 233篇 |
2014年 | 202篇 |
2013年 | 154篇 |
2012年 | 448篇 |
2011年 | 301篇 |
2010年 | 109篇 |
2009年 | 73篇 |
2008年 | 64篇 |
2007年 | 39篇 |
2006年 | 41篇 |
2005年 | 776篇 |
2004年 | 655篇 |
2003年 | 447篇 |
2002年 | 111篇 |
2001年 | 130篇 |
2000年 | 34篇 |
1999年 | 147篇 |
1992年 | 117篇 |
1991年 | 145篇 |
1990年 | 168篇 |
1989年 | 147篇 |
1988年 | 171篇 |
1987年 | 113篇 |
1986年 | 143篇 |
1985年 | 117篇 |
1984年 | 91篇 |
1983年 | 81篇 |
1982年 | 33篇 |
1981年 | 17篇 |
1980年 | 23篇 |
1979年 | 133篇 |
1978年 | 96篇 |
1977年 | 91篇 |
1976年 | 77篇 |
1975年 | 137篇 |
1974年 | 130篇 |
1973年 | 116篇 |
1972年 | 138篇 |
1971年 | 118篇 |
1970年 | 88篇 |
1969年 | 102篇 |
1968年 | 113篇 |
1967年 | 125篇 |
1966年 | 102篇 |
1965年 | 70篇 |
排序方式: 共有7542条查询结果,搜索用时 0 毫秒
41.
Zaida Mu?oz Assumpció Moret Sandra Garcés 《European journal of plant pathology / European Foundation for Plant Pathology》2008,120(4):331-337
The pathogenic fungi Verticillium alboatrum and Diplodia scrobiculata were assayed for biological control of Diplodia pinea on Aleppo pine (Pinus halepensis) in Catalonia (north-eastern Spain). Young shoots were pre-treated with inoculations of either V. dahliae or D. scrobiculata, by placing colonized agar plugs on wounds made by removing a single needle fascicle. An inoculation with D. pinea was performed 15 days later. Two months after the shoot inoculations, the canker length on the stems was measured and the
percentage of shoot dieback calculated. Verticillium dahliae and D. scrobiculata were found to significantly reduce the canker length of D. pinea (P < 0.05) when compared with positive controls. Diplodia pinea was slightly more sensitive to V. dahliae than to D. scrobiculata, but no significant differences (P > 0.05) were observed in the mean canker length between the two treatments. Trees pre-inoculated with V. dahliae resulted in 31.12% shoot dieback, while those pre-inoculated with D. scrobiculata resulted in 32.18% shoot dieback, compared with positive controls (42.85%). 相似文献
42.
Phytophthora root rot, caused byPhytophthora cinnamomi Rands, is the most important disease of avocado (Persea americana Miller). In an attempt to identify root rot-resistant rootstocks that could ultimately be used under conditions in southern
Florida, we screened open-pollinated progeny of avocado from the National Germplasm Repository in Miami. From 1996 to 1998,
a total of 2,355 seedlings from 51 accessions were examined in potting mix artificially infested withP. cinnamomi. Most seedlings developed severe root rot, but tolerance was observed in some families (i.e., progeny of certain accessions). Although the most susceptible families developed mean disease ratings of up to 97% root
necrosis, mean ratings for the most tolerant families were less than 60%. There was also a strong relationship between the
racial background of the female parent and the tolerance of seedlings. Seedlings of the West Indian race and hybrids between
it and the Guatemalan race were significantly more tolerant than those from other parents (P< 0.05). Individuals in several
families developed < 50% root necrosis, the arbitrary standard of tolerance in this study. Twelve families accounted for 82%
(188 of 229) of the tolerant seedlings, and only two of these did not have a West Indian or Guatemalan × West Indian pedigree.
Broad-sense heritability for PRR tolerance was 0.45. This is the first report on the inheritance of PRR tolerance in avocado
and on the influence of genotype and racial pedigree under controlled conditions. 相似文献
43.
为筛选适宜保定地区栽植的早熟苹果品种,以嫁接在SH40中间砧上的不同早熟苹果品种(系)为试材,测定了不同品种(系)早熟苹果树体生长发育指标和果实品质。结果表明:除嘎啦早熟变异外,其他供试品种(系)树体生长较好,3年生时Xu2-7、Xu3-2树高330.0~352.5 cm,4年生时为394.0~417.5 cm,Xu3-2、藤牧1号、信浓红4年生为336.5~381.0 cm。4年生时,干径以Xu2-5最大;短枝、中枝、叶丛枝均以Xu2-5最多,长枝以Xu2-7最多,总枝量以Xu2-5最多;藤牧1号短枝所占比例最高(57.4%)。应用模糊综合评判法得出Xu2-5、Xu2-7、信浓红、藤牧1号果实品质较高。 相似文献
44.
本试验旨在研究玉米青贮与花生秧配比对奶牛瘤胃中花生秧降解特性的影响。选择4头体重、生理状态、生产性能相近,装有永久瘤胃瘘管的中国荷斯坦奶牛,分别饲喂含有玉米青贮与花生秧不同配比的全混合日粮(TMR),3种TMR中玉米青贮与花生秧的干物质(DM)配比分别为3.9∶1.0(A组)、1.2∶1.0(B组)、0.4∶1.0(C组)。试验分3期进行,依次进行A、B、C组试验。每期预试15 d,采样期4 d;共57 d。采用尼龙袋瘤胃降解技术测定花生秧在奶牛瘤胃中DM、粗蛋白质(CP)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的72 h瘤胃降解率,并求得目标养分的动态降解参数及有效降解率。结果表明:1)花生秧的DM在瘤胃中有效降解率为56.49%~59.62%,CP为40.45%~47.36%,NDF为33.26%~35.20%,ADF为36.31%~37.45%。2)B组DM的有效降解率显著高于C组(P0.05),极显著高于A组(P0.01);B、C组的CP有效降解率显著高于A组(P0.05)。3)B、C组的NDF快速降解部分含量显著高于A组(P0.05);3种TMR对花生秧粗NDF和ADF有效降解率无显著影响(P0.05)。由此可见,花生秧具有较高的饲用价值。本试验条件下,玉米青贮与花生秧DM配比为1.2∶1.0时,可有效提高花生秧DM和CP的瘤胃降解率。 相似文献
45.
46.
Comparison of water status indicators for young peach trees 总被引:12,自引:1,他引:12
We measured a series of physiological and physical indicators and compared them to xylem sap flow, to identify the most sensitive and reliable plant water status indicator. In the growing season of 1998, 4-year-old peach trees (Prunus persica Batsch cv. 'Suncrest', grafted on 'GF 677' rootstock) were studied under two irrigation treatments, 25 l dayу and no irrigation, and during recovery. Trials were conducted near Pisa (Italy) in a peach orchard situated on a medium clay loam soil and equipped with a drip-irrigation system (four 4 l hу drippers per tree). Measurements of leaf water potential (W), stem water potential (S), and leaf temperature (Tl) were taken over 5 days (from dawn to sunset) and analyzed in conjunction with climatic data, sap flow (SF), trunk diameter fluctuation (TDF) and soil water content (SWC). Physiological indicators showed substantial differences in sensitivity. The first indication of changes in water status was the decrease of stem radial growth. TDF and SF revealed significant differences between the two irrigation treatments even in the absence of differences in pre-dawn leaf water potential (pdW), up until now widely accepted as the benchmark of water status indicators. Irrigated trees showed a typical trend in SF rate during the day, while in non-irrigated plants the maximum peak of transpiration was anticipated. Measurements of water potential showed S to be a better indicator of tree water status than W. Tl was found to have poor sensitivity. In conclusion, we found the sensitivity of the indicators from the most to the least was: TDF >SF rate >SF cumulated = pdW=S>mdW>Tl. 相似文献
47.
Yaohu?KangEmail author Feng-Xin?Wang Hai-Jun?Liu Bao-Zhong?Yuan 《Irrigation Science》2004,23(3):133-143
A field experiment comparing different irrigation frequencies and soil matric potential thresholds on potato evapotranspiration (ET), yield (Y) and water-use efficiency (WUE) was carried out in a loam soil. The experiment included five treatments for soil matric potential: F1 (-15 kPa), F2 (-25 kPa), F3 (-35 kPa), F4 (-45 kPa) and F5 (-55 kPa) and six treatments for irrigation frequency: N1 (once every day), N2 (once every 2 days), N3 (once every 3 days), N4 (once every 4 days), N6 (once every 6 days) and N8 (once every 8 days). Results indicate that both soil matric potential and drip irrigation frequency influenced potato ET, Y and WUE. Potato ET increased as irrigation frequency and soil matric potential increased. Comparing soil water potential, the highest ET was 63.4 mm (32.1%) more than the lowest value. Based on irrigation frequency treatments, the highest ET was 36.7 mm (19.2%) more than the lowest value. Potato Y and WUE were also found to increase as irrigation frequency increased. Potato Y increased with an increase in soil water potential then started to decrease. The highest Y and WUE values were achieved with a soil matric potential threshold of -25 kPa and an irrigation frequency of once a day.Communicated by J. Ayars 相似文献
48.
Shanshan?Chen Jiahuan?Tang Li?Fu Yong?Yuan Shungui?ZhouEmail author 《Journal of Soils and Sediments》2016,16(9):2326-2334
Purpose
The low conductivity of sediments for mass and electron transport is the most severe limiting factor in sediment microbial fuel cells (SMFCs), so that sediment ameliorations yielded more remarkable effects than electrode improvements. The objective of this research was to enhance the electricity generation of SMFCs with amendments of biochar to freshwater sediments for conductivity enhancement.Materials and methods
Laboratory-scale SMFCs were constructed and biochars were produced from coconut shells at different temperatures. Variations in the power output, electrode potential, internal resistance, total organic carbon (TOC) content, and microbial communities were measured.Results and discussion
Amending with biochar reduced the charge transfer resistances of SMFCs and enriched the Firmicutes (mainly Fusibacter sp.) in the sediment, which improved the SMFC power generation by two- to tenfold and enhanced the TOC removal rate by 1.7- to fourfold relative to those without the amendment.Conclusions
The results suggested that biochar amendment is a promising strategy to enhance SMFC power production, and the electrical conductivity of biochar should be considered important when interpreting the impact biochar has on the electrical performance of soil or freshwater sediment MFCs.49.
夷优180系福建省南平市农业科学研究所用自主选育的三系不育系夷A与恢复系南恢180配组而成的杂交中稻新品种。经多年在福建省各地试验、试种表现群体整齐、适应性广、产量高、抗性好等特点,2014年通过福建省农作物品种审定。简述了杂交水稻夷优180的选育及应用。 相似文献
50.