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141.
Land use changes operate at different scales. They trigger a cascade of effects that simultaneously modify the composition
or structure of the landscape and of the local vegetation. Mobil animals, and birds in particular, can respond quickly to
such multi-scalar changes. We took advantage of a long term study on the response of songbirds to land-use changes on four
Mediterranean islands in Corsica and Sardinia to explore the benefits of a multi-scale analysis of the relationships between
songbird distribution, vegetation structure and landscape dynamics. Field data and aerial photographs were used to describe
the vegetation at three different scales. Birds were censused by point counts. We used statistical variance decomposition
to study how bird distribution and vegetation at various scales were linked. We analysed multi-scale vegetation changes (floristic
composition, plot vegetation type, and landscape structure) and their consequences on bird distribution with multivariate
and non-parametrical tests. The distribution of most species was linked to at least two spatial scales. The weight of a given
scale was consistent with life-history traits for species whose biology was well-known. In the examples studied, vegetation
composition, vegetation type and landscape changes that resulted from land abandonment negatively affected birds depending
on open or heterogeneous areas. Our results emphasize that multi-scale analyses can greatly enhance our understanding of bird
distribution and of their changes. Management of these populations should take into account measures at various spatial scales
depending on the sensitivity of the species. 相似文献
142.
Heike Kappes Kurt Jordaens Frederik Hendrickx Jean-Pierre Maelfait Luc Lens Thierry Backeljau 《Landscape Ecology》2009,24(5):685-697
Habitat fragmentation is a major cause for species loss, but its effect on invertebrates with low active dispersal power,
like terrestrial gastropods, has rarely been studied. Such species can not cross a hostile habitat matrix, for which the predictions
of island theory, such as positive relations between species richness and patch size, should apply. In order to test this
prediction, we studied gastropod species diversity by assessing gastropod assemblage characteristics from 35 sites in 19 fragments
of deciduous old-growth forests in the Lower Rhine Embayment, Germany. Assemblages differed between larger (≥700 ha) and smaller
forests (<400 ha), those of large forests held a higher percentage of forest species. Although α-diversity was similar between
the two forest size classes, small forests often comprised matrix species, resulting in a higher β-diversity. Edge effects
on the species richness of matrix species were noticeable up to 250 m into the forest. Hierarchical partitioning revealed
that distance to disturbances (external edge, internal edges like roads) explained most assemblage variables, whereas forest
size and woodland cover within a 1 km radius from the sites explained only a few assemblage variables. Densities of two forest-associated
species, Discus rotundatus and Arion fuscus, decreased with forest size. Yet, forest size was positively correlated with richness of typical forest species and densities
of Limax cinereoniger. The latter species seems to need forests of >1,000 ha, i.e., well above the size of most fragments. In conclusion, the prediction
is valid only for forest species. The response to fragmentation is species specific and seems to depend on habitat specialization
and macroclimatic conditions.
Jean-Pierre Maelfait: Deceased. 相似文献
143.
EGF in mouse neurons LI Juan WANG Li CHEN Rong LIU Xiao-yan MEI Zhi-qiang HE Tao 《园艺学报》2011,27(4):779-782
AIM: To explore the mechanism of signaling transduction and cross talk between cholecystokinin octapeptide (CCK8) and epidermal growth factor (EGF) in mouse neurons and to observe the effect of CCK8 in coordination with EGF on neuron growth and cell viability. METHODS: For determining which kind of CCK receptor mediated the phosphorylation of EGF receptor, the cultured neurons were randomly divided into control group, CCK8 stimulation group, CCKA receptor antagonist group, CCKB receptor antagonist group, and CCKA+CCKB receptor antagonist group. Control and stimulation groups were stimulated with DMEM and CCK8 (10-7 mol/L) for 5 min, respectively, while antagonist groups were pre-incubated with different types of receptor antagonists (10-8 mol/L) for 10 min and followed by stimulating the neurons with CCK8. For observing the effect of CCK8 and EGF on the phosphorylation of EGFR in neurons and on neuron growth and cell viability, the cultured neurons were randomly divided into control group, CCK8 stimulation group, EGF stimulation group and CCK8+EGF stimulation group, which were stimulated with DMEM, CCK8 (10-7 mol/L), EGF (40 μg/L) and CCK8+EGF for 5 min, respectively. Reactions were terminated by freezing the neurons in liquid nitrogen and the phosphorylated EGFR was detected by Western blotting. Meanwhile, the viability of the neurons was observed by MTT method after stimulated for 24 h, 48 h, 72 h and 96 h. RESULTS: The phosphorylation levels of EGFR were decreased in the neurons treated with either of the two CCK receptor antagonists, and more obvious decrease was observed when the two CCK receptor antagonists were used in combination. Compared with control group, the phosphorylation levels of EGFR in the neurons were significantly increased(P<0.05) after stimulated with CCK8 or EGF, and the increase was more remarkable in CCK8+EGF stimulation group. CCK8 or EGF improved the viability and prolonged the life span of the neuron, and synergism of these two reagents was observed. CONCLUSION: Both CCKA and CCKB receptors are involved in the phosphorylation of EGFR in the neurons stimulated by CCK8, and the type A receptor may play a more important role. There is cross-talk between CCK8 and EGF signaling pathways in neurons. The signaling cross-talk between CCK8 and EGF may be the underlying molecular mechanism responsible for the synergistic effect on the neuron growth and viability in vitro. 相似文献
144.
以分离自新疆古尔班通古特沙漠土壤的放线菌为试材,采用琼脂块法和生长速率法,研究了供试放线菌对草莓灰霉病菌的抑菌活性;采用形态学特征、生理生化特性、16SrDNA序列分析等方法对筛选出的高活性拮抗菌株进行种类鉴定。结果表明:从141株放线菌中筛选出1株对草莓灰霉病菌的抑菌圈直径为20.67mm的高活性拮抗菌株XJ93。该菌株无菌发酵滤液对多种植物病原真菌具有明显抑制作用,抑菌率为25.00%~71.67%;80℃处理60min其抑菌率未见明显变化,在pH 5~9范围内其抑菌活性稳定,在可见光和紫外线照射150min内亦保持良好的抑菌活性。拮抗菌株XJ93经鉴定为唐德链霉菌(Streptomyces tendae)。拮抗放线菌XJ93具有广谱抑菌活性,对环境有良好的稳定性,可作为防治果蔬草莓灰霉病的生物农药潜力菌株进行开发应用。 相似文献
145.
以川农泡椒1号为试验材料,研究遮阳网+薄膜、遮阳网和露地3种栽培模式对川农泡椒1号品质的影响。试验结果表明,在夏季采用避雨栽培后,辣椒品质有所下降,其中VC、还原糖的含量均极显著低于对照,总糖含量差异不显著。而在避雨栽培的两种模式中,遮阳网+薄膜模式比遮阳网模式VC含量高5.4%,差异显著;还原糖高10.8%,差异极显著;总糖高0.8%,差异不显著。 相似文献
146.
为明确苹果锈果类病毒(Apple scar skin viroid,ASSVd)在烟台市富士苹果上的变异情况,通过特异性引物对携带苹果锈果类病毒的富士嫩叶进行ASSVd全长扩增,利用生物学软件DNAMAN对所得变异序列进行分析并构建系统进化树。结果表明,从130个样品中筛选到36个阳性样品,36个阳性样品中共克隆获得52条329~333 nt的ASSVd变异序列,其中30个阳性样品含2条或2条以上的ASSVd序列。对所得变异序列进行序列比对发现,同一样品不同克隆间核苷酸序列相似性为94.0%~100.0%,所有变异序列核苷酸序列相似性为94.0%~99.7%,与Gen Bank中来自不同国家或地区的10条ASSVd分离物核苷酸序列相似性为88.3%~99.7%。将序列相似性低于97.0%的12条变异序列进行系统进化分析,结果显示除了333 nt变异序列ZS2-6与伊朗苹果分离物在同一分支外,其余11条变异序列位于同一分支。52条变异序列多序列比对发现,变异位点主要集中在TL区、P区和C区。研究表明烟台市富士苹果上ASSVd存在一定的分子变异。 相似文献
147.
加快现代植保技术体系建设的对策研究 总被引:3,自引:0,他引:3
植保技术体系呈现出病虫害预测预报能力明显提高,防控技术体系日臻完善,农药与药械应用技术稳步发展,植物检疫监管技术基础更加牢固的现状;承载着为领导部门和农民提供病虫灾害防控信息、病虫害科学防控技术指导、农药与药械科学使用监管、依法开展植物疫情管控的重大任务。发展现代植保技术体系,要突出病虫害测报公益性,着力病虫害防控的防灾性,确保农药与药械应用的安全性,关切植物疫情蔓延的毁灭性。建设现代植保技术体系的对策措施是:强化病虫害测报体系与信息网络建设,提升测报技术水平;加强病虫害防控技术支撑与推广能力建设,创新推广模式,大力推进绿色防控;推进农药与药械产品应用技术研发推广和专业化统防统治;加大植物检疫技术研发和执法监管力度。 相似文献
148.
149.
引入遗传算法优化BP神经网络权重和阈值的方法建立黄土坡面产流入渗模型.模型以雨强、降雨历时、表层40 cm土壤前期含水量、坡度值为输入项,径流量、入渗量为输出项,用实测资料对网络进行模拟和预测.模拟结果平均误差6.32%和1.93%,预测结果平均误差为5.71%和1.92%.并与传统BP神经网络模型和定雨强Philip... 相似文献
150.
Christopher R. Thornton 《European journal of plant pathology / European Foundation for Plant Pathology》2008,121(3):347-353
Species of the genus Trichoderma are ubiquitous soil-borne fungi that exhibit antagonism towards a number of economically important plant-pathogenic fungi
and oomycetes. This review discusses recent developments in the use of monoclonal antibodies to detect these fungi in their
natural soil environments and to quantify their population dynamics during antagonistic interactions with saprotrophic competitors
in soil-based systems. Immunological approaches to detection and quantification are examined in relation to conventional plate
enrichment techniques and to nucleic acid-based procedures. An example of recent research using a mAb-based assay to quantify
the effects of saprotrophic competition on the growth of Trichoderma isolates in mixed species, soil-based, microcosms is presented. Future technological developments in immunoassays for tracking
Trichoderma populations in soil are discussed and results presented showing the accurate detection and visualization of a plant growth-promoting
isolate of T. hamatum in the rhizosphere of lettuce using mAb-based immunodiagnostic assays. 相似文献