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991.
992.
采用小流域平行对比法,分析研究小流域的次降雨洪水过程,研究水土保持综合治理对小流域洪水的作用过程,通过双环入渗法测定流域土壤入渗速率,分析不同土地利用类型对土壤入渗速率的影响,结果表明,水土保持林草措施通过改变流域下垫面条件,改善土壤的入渗性能并对洪水过程产生影响。 相似文献
993.
994.
Background, Aims, and Scope As a consequence of human living and activity, water infiltration to the urban subsurface occurs from a variety of different
sources, like precipitation, irrigation, leaking pipes and sewers, septic tanks and rainwater infiltration ponds. This infiltration
is strongly related with quality issues of the infiltrated water and further impact on groundwater quality. In order to set
up an integrated urban water balance it becomes essential to estimate the infiltration processes, i.e. water flow and solute
transport, from these different infiltration sources and to take into account the large spatial variability of sediment properties,
the geometric settings of these sources and the groundwater table. For that purpose, the development of simple, physically-based
quantification approaches is required in order to establish an efficiently working prediction and risk analysis tool within
the framework of an integrated urban water management system. The scope of the presented work was to demonstrate the applicability
of the developed approaches at urban scale.
Methods Since a detailed, three-dimensional, numerical quantification of the infiltration processes within the entire urban area is
not possible, the individual sources were considered as independent within the EU AISUWRS project. Different models were developed
for balancing infiltration from areal and point sources with respect to the related flow pattern. The analytical model UL_FLOW,
based on one-dimensional, steady state analytical solutions, allows the estimation of conservative tracer residence times
in layered sediments under varying infiltration rates. The numerical model WSTM, based on a three-dimensional random walk
approach, calculates water and solute transport from pipe leaks. Additionally, the sources were classified in accordance to
the spatial distribution of the parameters determining the infiltration processes.
Results UL_FLOW was applied to data sets from the city of Rastatt within a case study of the AISUWRS project. Each neighbourhood of
water balance computation by the Urban Volume and Quality Model (UVQ) was defined as an areal infiltration source with unique
parameter values for sediment depth, profile and properties, as well as infiltration rate time series. Groundwater recharge
and residence time series were computed for each neighbourhood. Relevant statistical parameters obtained by time series analyses
from those time series could be mapped by GIS. Point infiltration, particularly from sewers, was classified due to the sediment
parameters and the distance to the groundwater table at each source location in order to reduce computational efforts. WSTM
computations provided time series of groundwater recharge and tracer breakthrough for some specific cases.
Discussion The analytical model UL_FLOW provides fast and efficient computation of groundwater recharge and residence times accounting
for storage effects within the unsaturated zone of urban areas. The reliability of this model has been shown by cross validation
with HYDRUS1D. Because of the high computational effort, WSTM could provide only short-term simulations for some specific
parameter sets for which residence time estimates could be derived.
Conclusions UL_FLOW provides an analytical modelling tool for balancing one-dimensional areal infiltration and estimating residence times
under varying conditions including spatial parameter variability. These balances could be used for assessing the impact of
those infiltration sources on groundwater quality. The tracer breakthrough from point infiltration sources computed by WSTM
could also be used for such kinds of assessment. The larger spatial parameter variability associated with these sources could
be handled by classification in GIS environments.
Recommendations and Perspectives Similar to the areal sources, a simple balance approach for point sources based on analytical solutions needs to be developed
for estimating residence times in order to avoid large computational efforts. Such a model would complete the balancing of
all kinds of infiltration sources in urban areas efficiently. Since the approaches are based on the balance of the physical
processes, they have a large predictive capability and could be included into an integrated urban water balance and management
system. The mapping of the statistical values of the residence times provides a tool to compare parts of the urban areas and
to visualize differences between urban water management scenarios. 相似文献
995.
利用室内模拟实验研究4种密度(1.20、1.30、1.45和1.55g/cm3)及3种煤土体积比(1∶0.5、1∶1.0、1∶2.0)条件下风化煤矸石的渗透规律。结果表明:随着密度的增大,煤矸石的渗透速率迅速减小,密度为1.20g/cm3煤矸石的初始渗透速率、稳渗速率和平均渗透速率分别是密度为1.30 g/cm3煤矸石的2.211、.92和2.30倍,分别是密度为1.55g/cm3煤矸石的60.00、102.54和129.13倍,且减小关系呈幂函数关系;随着煤土体积比的增大,煤矸石的渗透速率迅速减小,煤土体积比为1∶0.5煤矸石的初始入渗速率、稳定入渗速率和平均入渗速率分别是煤土体积比为1∶1.0煤矸石的1.05、1.23和1.42倍,分别是煤土体积比为1∶2.0煤矸石的3.98、1.45和3.18倍;在密度为1.20和1.30g/cm3及煤土体积比为1∶0.51、∶1.0的情况下,用通用经验公式和考斯加可夫经验公式表达煤矸石的入渗过程较为理想,而在密度为1.45和1.55g/cm3及煤土体积比为1∶2.0的情况下,用通用经验公式与实测数据的拟合度表达最好。 相似文献
996.
以莲花湖库区红松水源涵养林为研究对象,由入渗速率拟合入渗模型,运用地统计学理论与方法对模型参数进行空间异质性分析。结果表明:采用Philip公式对入渗过程进行数学模拟最佳,模型参数吸渗率和稳渗率均服从对数正态分布,结构比分别为0.773、0.678,变程分别为8.04和6.69m,分维数分别为1.954、1.978。二者相比,吸渗率空间依赖性强,空间相关范围大,空间分布较简单,在空间分布格局上二者呈极显著正相关关系,相关系数R为0.52。 相似文献
997.
采用双环入渗法研究了豫西低山丘陵区6种不同植被恢复类型表层土壤入渗规律的差异,并选择Kostiakov公式、Horton公式和Philip公式对6种类型植被恢复土壤的入渗过程进行了模拟.结果表明:①不同植被恢复类型土壤的初渗率、稳渗率、孔隙度和含水量均存在显著差异(P<0.01),初渗率和稳渗率均表现出栓皮栎次生林>栓皮栎人工林>刺槐人工林>侧柏人工林>灌丛>荒草地的规律;②Philip公式对6种植被恢复类型土壤入渗过程的拟合精度最高,6种植被恢复类型土壤入渗过程呈现出相似的规律.可分为瞬变阶段(0~15 min)、渐变阶段(15~30 min)和稳定阶段(30 min后);③土壤的物理性质影响入渗率,稳渗率与土壤容重呈负相关,符合负指数曲线;林地由于土壤容重降低、孔隙度增加的缘故,其土壤入渗率明显高于荒草地.运用封育天然次生林和乡土树种人工林进行植被恢复有利于提高土壤的入渗性能. 相似文献
998.
研究了下插式土壤松耕方法,分析了其工作原理、理想的刀具结构和合适的松土距离为50~70 mm,并用这种方法松土后进行了施水试验。结果表明:灌水入渗深度比未耕地或旋耕地对应值平均增加20 mm以上,且土壤湿润区整体下移约13 mm,灌水水平方向和垂直方向入渗深度的比值由1.3降低到0.8,而且,土壤紧实度和含水率均满足玉米施水播种的需要。这种方法有效增加了玉米施水播种灌溉水的下渗深度,减少了水分蒸发。 相似文献
999.
应用遥感和GIS技术以及景观格局理论,以历史文化资源丰富的吐鲁番为研究区,利用1990年、1999年和2010年的遥感数据,研究吐鲁番周边历史文化资源景观类型变化。结果表明:① 自然科学的研究方法和先进的空间信息技术手段,可以改进部分社会学科对历史文化资源保护定量化的不足;② 整个时段(1990-2010年)周边历史文化资源总斑块数目变化不大,Shannon多样性指数由0.965 2减小到了0.837 6,Shannon均匀度指数由0.436 8增加到0.521 7,优势度指数有所降低;③ 从不同景观类型来看,受人类干扰较小的历史文化资源有海洋墓地、阿萨协亥尔古城、阔坦吐尔古城;受人类干扰较大的有高昌故城、交河故城、苏公塔。研究结果可为吐鲁番地区的历史文化资源管理和保护提供科学依据。 相似文献
1000.
Jeremy Roffey 《国际虫害防治杂志》2013,59(1):12-17
Abstract Imperata cylindrica is one of the most noxious weeds in South East Asia. Over the past two decades significant advances have been made in the understanding of its biology and control. This paper reviews work over this period and concludes that despite such advances, there remains much scope for improvement of control, particularly in development of methods appropriate for small scale farmers with limited resources. 相似文献