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目的 试图给出确定森林群落树种丰富度的方法,解决物种丰富度测度问题,完善森林生物多样性研究的方法。 方法 采用Monod模型表达种-面积曲线,通过数学手段确定最小森林群落面积和最大树种数。 结果 用本研究提出的方法对不同气候带森林物种丰富度进行测算,结果表明:热带森林群落具有更高的最大树种数和更大的群落最小面积,物种丰富度随气候带由热带到寒温带逐渐减少。 结论 用最大树种数能够确切表达不同气候带森林群落树种丰富度,克服了现有研究中直接把不同大小调查面积上的树种数量视为树种丰富度的弊端。 相似文献
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1982-2006年华北植被指数时空变化特征 总被引:3,自引:0,他引:3
利用1982-2006年GIMMS/NDVI数据,研究华北近25 a来植被指数在时间和空间上的变化。结果表明:①植被指数的年内变化呈单峰型,最大值出现在夏季,其中北京市NDVI最大,森林NDVI比农田和草地NDVI大;②华北年平均NDVI呈增加趋势,河北省植被指数增加最快,北京市次之,不同土地覆盖类型中,农田NDVI增加最快,草地次之,森林最小;③空间趋势分析结果显示,华北植被指数改善的面积占整个地区面积的15.96%,退化面积占11.86%,其中,河北省改善面积最大,内蒙古退化较明显,不同土地覆盖类型中,农田植被改善最明显;④基于华北近年暖干化发展趋势下,人类活动对该区域NDVI变化起到了重要作用。 相似文献
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介绍燕麦的营养价值及其市场前景,阐述法库县在土质、气候、地理环境、人文环境等方面种植燕麦的条件优势,通过对比种植燕麦与玉米的经济收益,探索燕麦在法库县种植的潜力。 相似文献
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A Gis-derived integrated moisture index to predict forest composition and productivity of Ohio forests (U.S.A.) 总被引:9,自引:0,他引:9
Iverson Louis R. Dale Martin E. Scott Charles T. Prasad Anantha 《Landscape Ecology》1997,12(5):331-348
A geographic information system (GIS) approach was used in conjunction with forest-plot data to develop an integrated moisture index (IMI), which was then used to predict forest productivity (site index) and species composition for forests in Ohio. In this region, typical of eastern hardwoods across the Midwest and southern Appalachians, topographic aspect and position (rather than elevation) change drastically at the fine scale and strongly influence many ecological functions. Elevational contours, soil series mapping units, and plot locations were digitized for the Vinton Furnace Experimental Forest in southeastern Ohio and gridded to 7.5-m cells for GIS modeling. Several landscape features (a slope-aspect shading index, cumulative flow of water downslope, curvature of the landscape, and water-holding capacity of the soil) were used to create the IMI, which was then statistically analyzed with site-index values and composition data for plots. On the basis of IMI values for forest land harvested in the past 30 years, we estimated oak site index and the percentage composition of two major species groups in the region: oak (Quercus spp.), and yellow poplar (Liriodendron tulipifera) plus black cherry (Prunus serotina). The derived statistical relationships were then applied in the GIS to create maps of site index and composition, and verified with independent data. The maps show the oaks will dominate on dry, ridge top positions (i.e., low site index), while the yellow poplar and black cherry will predominate on mesic sites. Digital elevation models with coarser resolution (1:24K, 1:100K, 1:250K) also were tested in the same manner. We had generally good success for 1:24K, moderate success for 1:100K, but no success for 1:250K data. This simple and portable approach has the advantage of using readily available GIS information which is time-invariant and requires no fieldwork. The IMI can be used to better manage forest resources where moisture is limiting and to predict how the resource will change under various forms of ecosystem management. 相似文献
27.
拓宽蚕沙有机肥在农业生产领域的应用范围,对促进蚕沙资源产业化开发利用具有重要意义。通过盆栽试验研究蚕沙发酵有机肥对烟草生长和烟叶品质的影响,结果表明:施用蚕沙发酵有机肥能够有效提高烟草植株叶片的生物量,烟叶的干质量与不施肥的对照相比,增加了46.16%,有显著差异(P<0.05);施用蚕沙发酵有机肥可增加烟叶中氮(N)、磷(P)、钾(K)的吸收量(分别比对照高出68.51%、59.15%、100.32%),且优化N、P、K 3种营养元素在烟草植株不同部位的分配比率,减少N、K在根和茎中的积累,提高N、K在烟叶中的分配比率;与对照相比,施用蚕沙发酵有机肥可使烟叶中的水溶性总糖含量提高30.17%,施木克值趋于适中,使烟叶的化学成分更趋合理。研究结果显示出蚕沙发酵有机肥在烟草大田生产中的应用潜力。 相似文献
28.
为探究坡位对油松林土壤理化性质的影响,以冀西北不同坡位油松林为研究对象,分析不同坡位土壤理化性质差异。结果表明:(1)冀西北油松林土壤容重在1.01~1.09 g/cm3之间变动,土壤容重坡上普遍高于坡下,二者差异显著;垂直梯度土壤容重随土层深度增加而增加。(2)土壤总孔隙度变化范围为43.48%~61.48%,随土层厚度增加而减少,坡上与坡下差异显著,平均来看坡下高于坡上。(3)土壤持水能力坡上与坡下差异较大,坡下总体高于坡上,其土壤饱和持水量最大相差108 t/hm2。(4)土壤养分坡上和坡下总体差异显著,均呈现坡下>坡上;从土壤垂直梯度来看,全氮、全磷与有效磷随土层厚度增加而增加,全钾、碱解氮与速效钾在土层垂直梯度上变化不明显。有机碳随土层厚度增加而减小,土壤pH值坡上与坡下差异不明显 相似文献
29.
The high rates of urban in-migration and poverty common in many developing country towns potentially increases the reliance of urban populations on the direct benefits provided by trees. Yet understanding of the extent of such use and the sources of these tree products is limited. Here we report on the extent of use of urban tree products by 450 households in the poorer areas of three towns along a rainfall gradient based on household questionnaires. We considered the proportion of households making use of each of several tree products and the collection or purchasing frequency which we disaggregated by source of the product, including trees in homesteads, urban spaces, edges of towns and via purchase from traders. Most households (91%) used firewood, which was most frequently collected from the urban fringe or purchased, although one-third at times also collected firewood from trees on their home plot. All households used fruits, most commonly sourced through purchase (98%), but nearly half of whom also supplemented by harvesting fruits from their home plot. Other products used included wood for building, fencing and utensils, herbal medicines, planting material and mulch. Collection of products from urban homestead trees was highest amongst households in the informal settlements and least in the more established townships. Residents of new low-cost housing areas made extensive use of urban tree products harvested in urban spaces because they had fewer homestead trees than residents of informal areas or townships. Overall, urban residents made use of a wide array of tangible products from trees which they sourced from a variety of places, including their homestead plot. This urges that planning agencies ensure that homestead plot sizes or other urban spaces that provide tree products are large enough to support the direct needs of poorer urban residents. 相似文献
30.