全文获取类型
收费全文 | 9660篇 |
免费 | 160篇 |
国内免费 | 19篇 |
专业分类
林业 | 1076篇 |
农学 | 289篇 |
基础科学 | 62篇 |
1482篇 | |
综合类 | 490篇 |
农作物 | 576篇 |
水产渔业 | 599篇 |
畜牧兽医 | 4402篇 |
园艺 | 244篇 |
植物保护 | 619篇 |
出版年
2021年 | 48篇 |
2020年 | 49篇 |
2019年 | 57篇 |
2018年 | 178篇 |
2017年 | 256篇 |
2016年 | 238篇 |
2015年 | 277篇 |
2014年 | 259篇 |
2013年 | 312篇 |
2012年 | 558篇 |
2011年 | 409篇 |
2010年 | 182篇 |
2009年 | 165篇 |
2008年 | 184篇 |
2007年 | 160篇 |
2006年 | 152篇 |
2005年 | 884篇 |
2004年 | 729篇 |
2003年 | 531篇 |
2002年 | 179篇 |
2001年 | 192篇 |
2000年 | 73篇 |
1999年 | 183篇 |
1995年 | 52篇 |
1992年 | 133篇 |
1991年 | 154篇 |
1990年 | 183篇 |
1989年 | 162篇 |
1988年 | 180篇 |
1987年 | 119篇 |
1986年 | 153篇 |
1985年 | 126篇 |
1984年 | 99篇 |
1983年 | 94篇 |
1982年 | 43篇 |
1979年 | 142篇 |
1978年 | 101篇 |
1977年 | 99篇 |
1976年 | 82篇 |
1975年 | 143篇 |
1974年 | 134篇 |
1973年 | 121篇 |
1972年 | 143篇 |
1971年 | 123篇 |
1970年 | 97篇 |
1969年 | 104篇 |
1968年 | 122篇 |
1967年 | 129篇 |
1966年 | 109篇 |
1965年 | 75篇 |
排序方式: 共有9839条查询结果,搜索用时 15 毫秒
71.
72.
The distribution of olive fruit fly captures with McPhail traps within an olive orchard 总被引:1,自引:0,他引:1
Ioannis?DimouEmail author Constantin?Koutsikopoulos Aristidis?Economopoulos Josef?Lykakis 《Phytoparasitica》2003,31(2):124-131
The spatial distribution of olive fruit flyBactrocera (Dacus) oleae (Gmelin) (Diptera: Tephritidae) field captures with McPhail traps within an experimental orchard was evaluated. Contour maps
were constructed to examine the patterns in the 3-year trapping data. Captures varied widely inside the olive orchard, with
traps suspended on wild olive trees exhibiting the poorest performance. Favorable microclimate, created by a standing water
pool, appeared to be responsible for increased trap captures during the hot summer months. The positive role of the olive
tree fruit load is also discussed.
http://www.phytoparasitica.org posting Feb. 2, 2003. 相似文献
73.
B. Kohlmayr J. Weiser R. Wegensteiner U. H?ndel Z. Zizka 《Anzeiger für Sch?dlingskunde》2003,4(2):65-73
Canningia tomici sp. n. (Microsporidia, Unikaryonidae) infects the midgut epithelium, the gut muscules, Malpighian tubules, connective tissues, adipose tissues and the gonads of the pine shoot beetle, Tomicus piniperda (L.) (Coleoptera, Scolytidae). The infection is present in populations of Tomicus piniperda in Europe and in the United States. Uninucleate oval single spores occur in two sizes: 2.8±0.4× 1.4±0.4m and 3.8±0.3×2.0±0.2m. The polar filament of this microsporidium is fixed subapically in a flat anchoring disc. The thick posterior lamellae of the binary polaroplast are asymmetric due to the lateral fixation of the polar filament. 相似文献
74.
Johannes Trini Hans Peter Maurer Sigrid Weissmann Tobias Würschum 《Plant Breeding》2020,139(5):906-915
Accurate hybrid prediction and knowledge about the relative contribution of general (GCA) and specific combining ability (SCA) are of utmost importance for efficient hybrid breeding. We therefore evaluated 91 triticale single-cross hybrids in field trials at seven environments for plant height, heading time, fresh biomass, dry matter content and dry biomass. Fresh and dry biomass showed the highest proportion (23%) of variance due to SCA. Prediction accuracies based on GCA were slightly higher than based on mid-parent values. Utilizing parental kinship information yielded the highest prediction accuracies when both parental lines have been tested in other hybrid combinations, but still moderate-to-low prediction accuracies for two untested parents. Thus, hybrid prediction for biomass traits in triticale is currently promising based on mid-parent values as emphasized by our simulation study, but can be expected to shift to GCA-based prediction with an increasing importance of GCA due to selection in hybrid breeding. Moreover, the performance of potential hybrids between newly developed lines can be predicted with moderate accuracy using genomic relationship information. 相似文献
75.
淮北地区氮肥群体最高生产力水稻钾素吸收利用特征 总被引:1,自引:1,他引:1
以淮北地区有代表性的34个中熟中粳品种为试材,设置7个氮肥水平(0、150.0、187.5、225.0、262.5、300.0、337.5 kg hm~(–2)),得出各品种的最高产量,将该最高产量定义为氮肥群体最高生产力。在此基础上,明确处于顶层水平(≥10.50 t hm~(–2))、高层水平(9.75~10.50 t hm~(–2))、中层水平(9.00~9.75 t hm~(–2))和底层水平(≤9.00 t hm~(–2))水稻品种的钾素积累、分配及转运特征。结果表明,4个生产力等级水稻品种地上部植株、茎鞘和叶片的含钾率在拔节期最高;抽穗期顶层水平品种的这3个参数高于其他3个等级的品种;穗部含钾率差异不显著。随着氮肥群体生产力等级的提高,钾素总积累量增多;拔节前底层水平钾素积累量最多,两年平均为120.56 kg hm~(–2),比例占50.56%,顶层水平为最少,两年平均为108.02 kg hm~(–2),比例占35.99%;拔节至抽穗期和抽穗至成熟期顶层水平钾素阶段积累量及比例显著高于其他3个等级。移栽至拔节期,钾素积累速率为中层底层高层顶层水平,拔节后则为顶层高层中层底层水平。叶片的钾素转运量及转运率明显高于茎鞘;顶层水平叶片的钾素转运量高于其他3个等级,高层水平叶片的转运率最高;穗部增加量随生产力等级的递增而变大;抽穗到成熟期,茎鞘、叶片对穗的钾素转运贡献率表现为底层最高,中层次之,顶层最低。4个等级水稻品种籽粒生产率和百千克籽粒吸钾量差异不显著;钾素偏生产力和钾收获指数均表现为顶层高层中层底层水平。总之,氮肥群体最高生产力越高,水稻中后期植株钾素积累量及器官对钾素的吸收利用效率越显著。抽穗后保持较高的钾素吸收利用及转运效率是高产水稻品种的重要特征。 相似文献
76.
A novel single phase boost type power factor correction circuit is introduced .The converter's efficiency is greatly improved by improving on the traditional boost type power factor correction circuit. Integrate Reset Control circuit is adopted to realize unity power factor. The Integrate Reset Control high efficiency single phase boost type power factor corrector has these characteristics as follows: It's constant frequency operation, which is of advantage of the design of filter. The control circuit is very simple and no need for multiplier. The result is quiet perfect, the input current follows the input voltage very well. The efficiency is very high. The result of simulation and experiment proves the correction of theory analysis. 相似文献
77.
s:It is proposed that the research of the structural durability is necessary considering the structural damages under the effect of deterioration of reinforced concrete. The most common reasons, which cause the deterioration of structures in China, are reinforcement corrosion and freeze thaw cycles of concrete. Based on the summarizing of research works of the effect of reinforced concrete deterioration on structures, it is indicated that the structural durability research should be carried out either in view of material science or that of structural science, and should be also considered the interaction of several factors with uncertain nature instead of the determined individual factor analysis. The structural durability of serviceable should be paid much more attention while researching the durability of structural capacity. The effect of reinforced concrete deterioration on structural capacity, rigidity and durability should be researched henceforth. 相似文献
78.
79.
Daylily rust fungus, Puccinia hemerocallidis, was proven to host-alternate between a wild daylily, Hemerocallis fulva var. longituba, and a patrinia, Patrinia villosa. No proof was obtained for the early belief that the fungus is pathogenic to plantainlilies, Hosta species, in addition to daylilies, Hemerocallis species. The fungus seems to alternate regularly between daylilies and patrinias in Japan because most daylily species are deciduous, and a vegetatively reproducing stage of the pathogen does not seem capable of successfully overwintering free of the living host tissue. 相似文献
80.