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51.
针对毛乌素沙地柠条不同种植密度对植物群落稳定性的影响,选择不同种植密度和自然恢复地进行研究对比,结果表明:自然恢复地以狗尾草、虫实、猪毛菜为主要优势种,建植柠条后,种植密度为1660丛/公顷的带间草本植物的重要值发生了很大的变化。多年生的植物种草木樨状黄芪、白草开始侵入并逐步成为优势种。种植密度为2490丛/公顷的带间草本植物则逐步演替为白草、沙蒿为主的植物群落。群落的植被盖度则以2490丛/公顷、1660丛/公顷的较高,分别达到了86.17%、80.33%,3330丛/公顷最低为64.17%,比自然恢复地低13.28%。通过对种植不同密度柠条林各样地群落种百分数与累积相对频度比值的计算,发现种植密度为2490丛/公顷、1660丛/公顷样地群落种百分数与累积相对频度比值最接近20/80的稳定点。可以看出随着柠条带间距的增加柠条带内的植物群落更加趋于稳定。 相似文献
52.
毛乌素沙地农业生态系统分析及评价 总被引:3,自引:1,他引:3
针对毛乌素沙地农业生态系统长期处于低而不稳的问题,结合毛乌素沙地农业生态系统自然环境优势,从整体上对毛乌素沙地农业生态系统结构进行了分析和评价。研究表明:毛乌素沙地农业生态系统在种植业上存在粮食生产压力过大、规模效益低下,特色产业开发不够、生态环境逐渐恶化;在养殖业上存在资金和科技投入不足、草畜矛盾突出、生产条件差等问题。但该沙地具有光、热、水、风能及土地等自然环境优势。因此,应大力调整种植业和养殖业结构,充分利用自然资源。并采取农牧结合、农林结合和沙区绿洲型发展模式,建立可持续发展的毛乌素沙地农业生态系统。 相似文献
53.
54.
Prediction of multinomial probability of land use change using a bisection decomposition and logistic regression 总被引:1,自引:1,他引:1
Land use change is an important research area in landscape ecology and urban development. Prediction of land use change (urban
development) provides critical information for making the right policies and management plans in order to maintain and improve
ecosystem and city functions. Logistic regression is a widely used method to predict binomial probabilities of land use change
when just two responses (change and no-change) are considered. However, in practice, more than two types of change are encountered
and multinomial probabilities are therefore needed. The existing methods for predicting multinomial probabilities have limits
in building multinomial probability models and are often based on improper assumptions. This is due to the lack of proper
methodology and inadequate software. In this study, a procedure has been developed for building models to predict the multinomial
probabilities of land use change and urban development. The foundation of this procedure consists of a special bisection decomposition
system for the decomposition of multiple-class systems to bi-class systems, conditional probability inference, and logistic
regression for binomial probability models. A case study of urban development has been conducted to evaluate this procedure.
The evaluation results demonstrated that different samples and bisection decomposition systems led to very similar quality
and performance in the developed multinomial probability models, which indicates the high stability of the proposed procedure
for this case study. 相似文献
55.
Neutral models for testing landscape hypotheses 总被引:5,自引:0,他引:5
Neutral landscape models were originally developed to test the hypothesis that human-induced fragmentation produces patterns
distinctly different from those associated with random processes. Other uses for neutral models have become apparent, including
the development and testing of landscape metrics to characterize landscape pattern. Although metric development proved to
be significant, the focus on metrics obscured the need for iterative hypothesis testing fundamental to the advancement of
the discipline. We present here an example of an alternative neutral model and hypothesis designed to relate the process of
landscape change to observed landscape patterns. The methods and program, QRULE, are described and options for statistical
testing outlined. The results show that human fragmentation of landscapes results in a non-random association of land-cover
types that can be describe by simple statistical methods. Options for additional landscape studies are discussed and access
to QRULE described in the hope that these methods will be employed to advance our understanding of the processes that affect
the structure and function in human dominated landscapes. 相似文献
56.
Land-use and vegetation cover have been linked to the nutrient levels (nitrogen, phosphorus) of surface waters in several
countries. However, the links generally relate to streams and rivers, or to specific types of standing water, for example
shallow lakes in a geologically defined region. We measured physical variables and nutrient chemistry of 45 water bodies representative
of the wide range of lentic wetland environments (swamps, riverine wetlands, estuaries, reservoirs, shallow lakes, deep lakes)
in Otago, New Zealand, and related these to catchment variables and land-use in order to assess the potential influence of
catchment modification on water quality of these diverse wetlands. Catchment boundaries and land cover were derived from maps
using ArcView GIS software. Our predictions that concentrations of nutrients and other components of water quality would correlate
positively with the nature and intensity of catchment modification were confirmed in multivariate analyses. Physical and chemical
measures were positively related to the extent of modification in the catchment (percentage of the catchment in pasture, planted
forest, scrub and urban areas), and negatively related to lack of catchment modification (more of the catchment in bare ground,
tussock grassland and indigenous forest). The strong negative correlations between nutrient concentrations, suspended sediment,
water colour and the percentage of tussock cover in the catchment imply that increased conversion of the␣native tussock grassland
to pastoral farming in␣Otago will increase nutrient concentrations and␣reduce water quality of the diverse lentic ecosystems. 相似文献
57.
通过对毛乌素沙地草木樨(Melilotus suaveolens)、胡枝子(Leapedeza bicolor)和沙打旺(Astragalus adsurgens)等3种豆科植物根际土壤样品和根样的采集和分析,研究了3种植物根际AM真菌的群落组成和生态分布.试验结果表明,在已分离出的3属28种AM真菌中,球囊霉属(Glomus)种类占绝对优势;3种豆科植物都有较高的AM真菌定殖率和孢子密度,但不同种之间或同一种植物在不同样地之间的AM真菌种类和分布差异显著.AM真菌泡囊定殖率和总定殖率与土壤速效N有显著负相关,其定殖强度可能主要取决于宿主植物和AM真菌的相互选择性. 相似文献
58.
根据盐池县毛乌素沙地自然特点,坚持以发展种植业、畜牧业为主线,以科技创新为动力,开发出5种毛乌素沙地草地畜牧业经营模式并进行示范,以扩宽增加农民经济收入渠道,促进区域经济的发展,实现生态环境、经济、社会的协调发展。 相似文献
59.
60.
从农民土地利用偏好以及居民地域性认同出发,将农民土地利用偏好分为农业生产功能偏好和经济生产功能偏好2类;并运用数学方法求取居民地域性认同综合指数,建立Logistic二项回归模型,研究农民土地利用偏好和居民地域性认同的相关性。结果表明,地域性认同程度高的农民更偏好于土地的经济生产功能。地方在开展土地整理或制定土地利用计划时,可根据当地居民地域性认同程度选择增大农地面积或是商铺、工厂的面积,提高人民的满意度。 相似文献