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21.
为深入了解油用亚麻主要品质和农艺性状的遗传变异,以253份油用亚麻种质为研究对象,在3个环境下(内蒙古呼和浩特市、集宁市和锡林郭勒盟太仆寺旗)对其全生育天数、株高、工艺长度、单株果数、每果粒数、单株粒重、千粒重和分枝数8个农艺性状及棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸、粗脂肪含量6个品质性状进行鉴定。结果表明,8个农艺性状的变异系数为5.66%~42.65%;6个品质性状的变异系数为4.10%~30.14%。全生育天数在太仆寺旗表现最长,为112.51 d;千粒重和单株粒重在集宁地区表现最大,分别为5.94和0.55 g;果粒数和单株果数在呼和浩特地区表现最多,分别为5.65和16.90;粗脂肪和亚麻酸含量在太仆寺旗地区表现最大,分别为39.53%和53.45%;亚油酸和棕榈酸含量在集宁地区最大,分别为16.41%和5.09%;油酸和硬脂酸含量在呼和浩特地区表现最大,分别为24.03%和8.31%。聚类分析表明,253份油用亚麻种质被划分为4个类群,相同地理来源的油用亚麻种质被聚到1个类群,为油用亚麻种质资源的收集保存与繁殖提供了科学依据。  相似文献   
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Physiological mechanisms by which nitrogen (N) fertilization affects growth and development in temperate deciduous forest trees are not clearly understood, especially under intensive silvicultural systems. Grafted, Tippecanoe 1 cultivar black walnut (Juglans nigra L.) trees were grown in an intensively managed plantation in west-central Spain and subjected to six, fixed-nutrient-ratio complete fertilizer treatments (defined as 0, 25, 50, 75, 150, and 300 g N tree?1) delivered via daily fertigation. Leaf chemistry and morphology were evaluated from June to September, and gas exchange was measured in July. Specific leaf mass, leaflet nitrogen (N), and chlorophyll concentrations varied over the course of the growing season, yet consistently increased with increasing fertilization. Net photosynthesis at ambient (A net) and light-saturated (A max) conditions increased from the unfertilized control to lowest treatment (25 g N) but did not increase at higher fertilizer rates. Photosynthetic N and chlorophyll use efficiencies decreased with increasing fertilization, but photosynthetic phosphorus and water use efficiencies increased. Transpiration rates and dark respiration were not significantly affected by treatment. Overall, the lowest fertilizer treatment (25 g N) had the greatest photosynthetic efficiency. Interactions between N and other nutrients with increasing fertilizer application suggested potential for nutrient imbalances at high fertilization rates. Our results provide a physiological justification for the use of low-to-moderate fertilization as an efficient strategy to promote black walnut plantation establishment under intensive cultural systems.  相似文献   
23.
Three fish-loading systems were used to harvest food-size channel catfish (Ictalurus punctatus). Loading rates of equipment and their effect on post-harvest fish survival and weight gain during cool and warm weather were studied.

The turbine pump loading rate (300·7 kg/min) was greater than the lift net (158·00 kg/min) and vacuum pump (54·1 kg/min), while the lift net was greater than the vacuum pump (p < 0·05).

Mean survivals (± SD) for catfish loaded by lift net, turbine pump and vacuum pump from earthen ponds during cool and warm weather were 96·6% (±2·8), 93·9% (±7·4) and 97·7% (±1·1) and 94·0% (±5·7), 85·3% (±8·6) and 89·0% (±12·5), respectively. Mean weight change (± SD) per catfish loaded by the same equipment during cool-and warm-weather tests were −8·2 g/fish (±31·1), −12·4 g/fish (±15·2) and −17·5 g/fish (±19·9), and 67·6 g/fish (±60·6), 33·9 g/fish (±137·4) and 32·4 g/fish (±142·1), respectivley. There were no significant differences among loading systems for survival or mean weight change per fish. The turbine pump is a possible alternative to the traditional life net as a means of loading food-size channel catfish. Further testing on commercial catfish farms is required.  相似文献   

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人工林UHF频段电波传播场强预测模型   总被引:1,自引:0,他引:1  
人工林无线电波传播场强模型是合理设计人工林环境无线电遥测遥控等通信电路的理论依据.该文在分析无线电波传播机理的基础上确定了人工林UHF频段传播损耗的三大组成部分及相应的计算方法,提出了人工林中某接收点处电场强度的预测模型.经过对北京西山人工侧柏林中不同参数的场强测试数据进行分析,校验了所建模型具有很高的精度.   相似文献   
27.
A toxin isolated from apple fruit tissue infected by Erwinia amylovora is 98 percent galactose in polymeric form, 0.375 percent protein, and has an average molecular weight of approximately 165,000. Young shoots of rosaceous, but not nonrosaceous, species wilt in a manner characteristic of the disease when placed in toxin solutions with concentrations as low as 10 micrograms per milliliter. Varieties of apple and pear susceptible to Erwinia amylovora wilt in 1 to 3 hours, whereas resistant varieties display symptoms 12 to 24 hours after treatment.  相似文献   
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Discovery of intense gamma-ray flashes of atmospheric origin   总被引:1,自引:0,他引:1  
Detectors aboard the Compton Gamma Ray Observatory have observed an unexplained terrestrial phenomenon: brief, intense flashes of gamma rays. These flashes must originate in the atmosphere at altitudes above at least 30 kilometers in order to escape atmospheric absorption and reach the orbiting detectors. At least a dozen such events have been detected over the past 2 years. The photon spectra from the events are very hard (peaking in the high-energy portion of the spectrum) and are consistent with bremsstrahlung emission from energetic (million-electron volt) electrons. The most likely origin of these high-energy electrons, although speculative at this time, is a rare type of high-altitude electrical discharge above thunderstorm regions.  相似文献   
30.
Sequences from the upstream and downstream flanking DNA regions of the psi eta-globin locus in Pan troglodytes (common chimpanzee), Gorilla gorilla (gorilla), and Pongo pygmaeus (orangutan, the closest living relative to Homo, Pan, and Gorilla) provided further data for evaluating the phylogenetic relations of humans and African apes. These newly sequenced orthologs [an additional 4.9 kilobase pairs (kbp) for each species] were combined with published psi eta-gene sequences and then compared to the same orthologous stretch (a continuous 7.1-kbp region) available for humans. Phylogenetic analysis of these nucleotide sequences by the parsimony method indicated (i) that human and chimpanzee are more closely related to each other than either is to gorilla and (ii) that the slowdown in the rate of sequence evolution evident in higher primates is especially pronounced in humans. These results indicate that features (for example, knuckle-walking) unique to African apes (but not to humans) are primitive and that even local molecular clocks should be applied with caution.  相似文献   
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