首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   350篇
  免费   9篇
  国内免费   1篇
林业   34篇
农学   14篇
  53篇
综合类   7篇
农作物   9篇
水产渔业   41篇
畜牧兽医   139篇
园艺   3篇
植物保护   60篇
  2023年   2篇
  2022年   3篇
  2021年   7篇
  2020年   3篇
  2019年   1篇
  2018年   8篇
  2017年   4篇
  2016年   15篇
  2015年   13篇
  2014年   8篇
  2013年   25篇
  2012年   18篇
  2011年   21篇
  2010年   17篇
  2009年   21篇
  2008年   27篇
  2007年   31篇
  2006年   26篇
  2005年   25篇
  2004年   20篇
  2003年   16篇
  2002年   18篇
  2001年   6篇
  2000年   5篇
  1999年   5篇
  1998年   1篇
  1996年   1篇
  1992年   1篇
  1991年   3篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1980年   3篇
排序方式: 共有360条查询结果,搜索用时 15 毫秒
131.
Two factorial pot experiments were conducted to evaluate the effect of biodecomposer (BD) and nutrient supplemented compost of pea residue on wheat and rice. Compost was prepared with green pea plant residue (PP), in the presence or absence of BD, without or with dried chicken manure (CM) and/or oilseed rape cake (RC). We assessed the effect of compost on yields and nutrient recovery efficiencies of both crops. Results revealed that BD reduced composting duration and enriched compost with N, P and K. Composts with CM and CM plus RC increased grain yields of wheat and rice. The composts increased grains of wheat and rice nearly 5 and 1.6 times, respectively, above the control. Nitrogen, P and K recovery efficiencies were positively correlated with yields, suggesting that supplementation in composting with CM or CM plus RC enabled effective accumulation of the nutrients, resulting in higher yield. Moreover, BD increased 9.4% of wheat and 6.9% of rice grains. So, composting of PP, in the presence of BD, with CM or CM plus RC is recommend for a pea-wheat-rice cropping system to improve soil fertility and effectiveness of pea on the system.  相似文献   
132.
133.
Total spikelet number per panicle (TSN) is thought to be one of the most important agronomic traits associated with grain production in rice (Oryza sativa L.). We previously reported the development of 334 introgression lines (ILs) with variations in agronomic traits in the genetic background of indica rice variety IR64. Among these, an IL derived from high-yielding rice variety Hoshiaoba showed significantly higher TSN than IR64. We therefore have conducted a quantitative trait locus (QTL) analysis for TSN in an F2 population of IL × IR64 to ascertain the genetic basis for the high TSN of the IL. The analysis revealed the presence of a QTL for TSN on chromosome 7, where several QTLs for grain number have been previously reported. We developed a near-isogenic line (NIL) for this QTL by using DNA marker-assisted selection and characterized its effect. The NIL showed significantly higher TSN than IR64. These results suggest that the QTL and the NIL will be useful materials in breeding programs aimed at increasing TSN.  相似文献   
134.
A potyvirus tentatively named Ornithogalum virus 3 (OV-3) was successfully isolated by single-aphid transmissions from O. thyrsoides mix-infected with OV-3, Ornithogalum mosaic virus (OrMV) and Ornithogalum stripe mosaic virus (OrSMV). OV-3, a flexuous, rod-shaped particle of ca. 690 nm, was sap and aphid transmissible. The virus had a narrow host range and caused necrotic mosaic on O. thyrsoides under cold conditions. We therefore propose the name Ornithogalum necrotic mosaic virus (OrNMV) for OV-3. A synergistic increase in symptom severity was apparent on O. thyrsoides mix-infected with OrSMV/OrNMV, but not with either OrMV/OrNMV or OrMV/OrSMV. The nucleotide sequence data reported is available in the DDBJ/EMBL/GenBank databases under accession number AB282754.  相似文献   
135.

Background  

Numerous processes in the living body exhibit daily rhythmicity. In this study, we characterized a daily rhythm of blood fluidity and identified its determinants.  相似文献   
136.
137.
Rhodococcus equi is a Gram-positive facultative intracellular bacterium that causes pyogranulomatous pneumonia in foals and immunocompromised people. In the present study, signature-tagged transposon mutagenesis was applied for the negative selection of R. equi mutants that cannot survive in vivo. Twenty-five distinguishable plasmid-transposon (plasposon) vectors by polymerase chain reaction (PCR), each containing a unique oligonucleotide tag, were constructed and used to select the transposon mutants that have in vivo fitness defects using a mouse systemic infection model. Of the 4,560 transposon mutants, 102 mutants were isolated via a real-time PCR-based screening as the mutants were unable to survive in the mouse model. Finally, 50 single transposon insertion sites were determined via the self-cloning strategy. The insertion of the transposon was seen on the virulence plasmid in 15 of the 50 mutants, whereas the remaining 35 mutants had the insertion of transposon on the chromosome. The chromosomal mutants contained transposon insertions in genes involved in cellular metabolism, DNA repair and recombination, gene regulation, non-ribosomal peptide synthesis, and unknown functions. Additionally, seven of the chromosomal mutants showed a reduced ability to multiply in the macrophages in vitro. In this study, we have identified several biosynthetic pathways as fitness factors associated with the growth within macrophages and survival in mice.  相似文献   
138.
Subtropical forests in the Ryukyu Islands have been degraded by silvicultural practices, and thus their structural attributes are being shifted to other states dominated by a few tree species. This study clarified the mechanisms of the change, and examined the effect of clear logging on the resilience of a subtropical forest. Sprouting regeneration and typhoon disturbance were introduced into an individual-based model, SEIB-DGVM, for describing stand development and succession. The regeneration dynamics from young secondary to old-growth stands were reproduced fairly well with the model. Sprouting recruitment produced high stem density at the beginning of stand development, which caused a self-thinning trajectory following the −3/2 power law. In the late development stage after 70 years, tree species diversity fluctuated because of the regenerative response of sprouting species and the facilitatory effect of typhoon disturbance on the coexistence of subordinate species. The death of canopy trees because of typhoon disturbances reduced the dominance of Castanopsis sieboldii, and depressed its dominance in the understory. Consequently, the understory species could establish by virtue of fallen canopy trees, and tree species diversity increased at the stand level. Clear logging experiments in the model revealed that species diversity deteriorated, especially in the stand dominated by sprouting species. Resilience of subtropical forests was determined by initial species composition before clear logging. Our simulation results suggest that repeated logging drives subtropical forests with high species diversity to a stand monopolized by C. sieboldii.  相似文献   
139.
The yields and properties of oil and gas fractions coproduced during carbonization of larch wood loaded with Ni 2%, Ni 2%+Ca 1%, and Ni 4% and without catalyst (None) at 700°–900°C were examined to clarify the catalytic effect in terms of conversion into fluid fuels. The net calorific value of oil occurred mainly below 500°C and increased in the order None < Ni 2% < Ni 4% < Ni 2%+Ca 1%, while the yield decreased in this order. The same order held for the production of gases enriched with hydrogen at 500°–700°C. Even above 800°C, markedly promoted evolution of hydrogen took place for all catalyst systems. These observations confirmed the effectiveness of nickel-catalyzed carbonization at 900°C, particularly Ni 2%+Ca 1%, for both upgrading of oil and gaseous fractions, although the quality of oil was not satisfactory. The catalysis of nickel with and without calcium is discussed on the basis of the modified Broid-Shafizadeh scheme, and the scheme was altered to adapt to the high temperature region where oil was no longer produced. Part of this study was presented at the 14th Annual Meeting of the Japan Institute of Energy, Suita, August 2005, and at the 18th Symposium, Session D, of the Materials Research Society of Japan, Tokyo, December 2007  相似文献   
140.
Magnaporthe oryzae chrysovirus 1 strain A (MoCV1-A) is associated with an impaired growth phenotype of its host fungus, Magnaporthe oryzae. In this report, we assayed the virulence and pathogenicity of MoCV1-A-infected and MoCV1-A-free M. oryzae on rice plants. MoCV1-A infection did not affect virulence-associated fungal traits, such as conidial germination and appressorium formation. However, after punch inoculation of leaves on rice plants, MoCV1-A-infected strain formed smaller lesions than the MoCV1-A-free strain did on all rice varieties tested, showing that MoCV1-A infection resulted in reduced virulence of host fungi in rice plants. In contrast, after spray inoculation of rice seedlings, in some cases, MoCV1-A-infected and MoCV1-A-free strains caused different lesion types (resistance to susceptible, or vice versa) on individual international differential rice varieties. However, we did not find any gain/loss of the fungal avirulence genes by PCR, suggesting that MoCV1-A infection can convert the pathogenicity of the host M. oryzae from avirulence to virulence, or from virulence to avirulence, depending on the rice variety. We also confirmed the correlation of these race conversion events and invasive hyphae growth of the fungi in a leaf sheath inoculation assay. These data suggested that MoCV1-A infection generally confers hypovirulence to the fungal host and could be a driving force to generate physiological diversity, including pathogenic races.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号