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41.
Marco Franchini 《Water Resources Management》1994,8(3):225-238
With reference to the kinematic wave theory coupled with the hypothesis of constant linear velocity for the rating curve, rising limb analytical solutions have been calculated for overland flow, over an Hortonian-infiltrating surface, and sediment discharge. These analytical solutions are certainly easier to use than the numerical integration of the basic equations and they may be used to obtain an initial evaluation of the parameters of more complex models generally devised for complicated cases.Notation
a
exponent of the Horton law [T–1]
-
b
exponent of the rill erosion equation
-
B
inter-rill erosion coefficient [ML–m–2T
m–1]
-
c
sediment concentration [ML–3]
-
c
o
reference sediment concentration [ML–3]
-
E
I
inter-rill erosion [ML–2T–1]
-
E
R
rill erosion [ML–2T–1]
-
f
c
final infiltration rate of the soil [LT–1]
-
f
o
initial infiltration rate of the soil [LT–1]
-
h
flow depth [L]
-
h
o
reference flow depth [L]
-
i
infiltration rate [LT–1]
-
k
rill erosion coefficient [ML–1–b
T–1]
-
K
integration constant
-
L()
Laplace transformation
-
m
exponent of the inter-rill erosion equation
-
n
Manning's coefficient [L–1/3T]
-
p
rainfall intensity [LT–1]
-
q
water discharge per unit width [L2T–1]
-
q
s
sediment discharge per unit width [ML–1T–1]
-
t
time [T]
-
t
p
ponding time [T]
-
x
distance along the flow direction [L]
Greek Letters
coefficient of the stage-discharge equation [L2–T–1]
-
exponent of the stage-discharge equation
-
rill erosion coefficient [L–1] 相似文献
42.
43.
通过分析牡丹江干流中下游河道泥沙特性,研究河道泥沙输移及补给规律,在对牡丹江干流河道梯级枢纽建成前后河道的水沙变化进行分析的基础上,并根据已有的泥沙资料,结合社会经济发展对砂石的需求,对牡丹江干流中下游河道的泥沙沉积量进行计算,研究确定泥沙补给量与开采量的关系,从而为牡丹江干流河道合理采砂提供依据. 相似文献
44.
Suspended sediment and organic contaminants were measured during a period of 2 years in the San Lorenzo River, central California, which discharges into the Pacific Ocean within the Monterey Bay National Marine Sanctuary, in an effort to quantify the potential environmental effects of storm events from a steep, mountainous coastal urban watershed. Most suspended sediment transport occurred during flooding caused by winter storms; 56% of the total sediment load for the 2‐year study was transported by the river during one storm event in January 2010. Concentrations of polycyclic aromatic hydrocarbons can exceed regulatory criteria during high‐flow events in the San Lorenzo River, and total annual polycyclic aromatic hydrocarbon load was on the order of 10 kg in water year 2010. These results highlight the importance of episodic sediment and contaminant transport in steep, mountainous coastal watersheds and emphasize the importance of understanding physical processes and quantifying chemical constituents in discharge from coastal watersheds on event‐scale terms. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
45.
Sharon L. Kanfoush 《Lakes & Reservoirs: Research and Management》2013,18(2):99-113
Fourth Lake is a drainage lake at 43°N, 74°W, from which a 37‐cm long mud‐water interface core was recovered. 210Pb dating indicates the core spans ≈340 years, from the Little Ice Age through modern global warming. Diatom accumulation responds to anthropogenic watershed disturbances, declining slightly up‐core until a peak in the late‐1800s attributable to sediment and nutrient influx from logging and enlargement of the outlet dam. A dramatic decrease occurs ≈1900 as logging and lake filling ceased, and a smaller peak ≈1960 accompanies residential development. Similar changes occur in organic carbon accumulation, which ranges from 0.0038–0.024 mg cm?2 year?1, with generally decreasing values up‐core, punctuated by maximum values in the late‐1800s. Expressing diatoms as concentration, however, reveals a doubling up‐core that positively correlates with changes extending beyond the watershed, including Northern Hemisphere temperature, atmospheric CO2 concentration and solar irradiance (R = 0.627, 0.675 and 0.400, respectively). A >50% increase in % organic carbon, from 3.8% to 5.9%, also positively correlates with these larger‐scale environmental conditions (R = 0.828, 0.830 and 0.832), while negative correlations with the extrabasinal records are exhibited by magnetic susceptibility (R = ?0.654, ?0.496, and ?0.660) and clay (R = ?0.770, ?0.762, and ?0.737). These changes are consistent with decreased sediment influx and reduced dilution of biogenous sedimentary components. In contrast to total diatoms, the accumulation of planktonic genus Asterionella displays a long‐term increase up‐core. Potential explanations include increasing duration of the ice‐free season or a shift in the timing of the spring bloom and a mismatch with abundance of predator(s). Asterionella also increases as a percentage of total diatoms, being positively correlated with extrabasinal conditions (R = 0.827, 0.774 and 0.674). This change occurs at the expense of many benthic genera and, over the past century, at the expense of tychoplanktonic genus, Aulacosiera. Heavily silicified, Aulacosiera requires strong mixing to remain within the epilimnion. Thus, its decline might result from increasing stratification caused by warming. 相似文献
46.
梭锥管混浊流体分离装置流场PIV 测试及分析 总被引:1,自引:0,他引:1
利用粒子图像测速技术,测试了两种工况下梭锥管混浊流体分离装置(简称梭锥管)内的水沙两相流的速度场,给出了梭锥管内泥沙运动的流速矢量分布及流速大小云图。对测试结果的分析表明,实测结果与理论分析结果一致。含沙水流进入梭锥管后,其内设置的多层锥圈把泥沙沉降区域分割成若干个沉降距离较短且相互独立的沉降空间,缩短了泥沙的自由沉降距离。相邻锥圈组成的水沙分离空间内,形成了沿锥圈上表面向下运动的泥沙流和沿锥圈下表面向上运动的清水流,使分离后的泥沙流和清水流沿各自独立路径流动,泥沙流流入排沙装置中心的排沙通道,而清水流流入装置边壁处的清水流通道,相互之间无混掺和干扰,加快了水沙分离速度。 相似文献
47.
Modeling and analysis of effects of precipitation and vegetation coverage on runoff and sediment yield in Jinsha River Basin 总被引:1,自引:0,他引:1
This paper focuses on the effects of precipitation and vegetation coverage on runoff and sediment yield in the Jinsha River Basin. Results of regression analysis were taken as input variables to investigate the applicability of the adaptive network-based fuzzy inference system (ANFIS) to simulating annual runoff and sediment yield. Correlation analysis indicates that runoff and sediment yield are positively correlated with the precipitation indices, while negatively correlated with the vegetation indices. Furthermore, the results of stepwise regression show that annual precipitation is the most important factor influencing the variation of runoff, followed by forest coverage, and their contributions to the variation of runoff are 69.8% and 17.3%, respectively. For sediment yield, rainfall erosivity is the most important factor, followed by forest coverage, and their contributions to the variation of sediment yield are 49.3% and 24.2%, respectively. The ANFIS model is of high precision in runoff forecasting, with a relative error of less than 5%, but of poor precision in sediment yield forecasting, indicating that precipitation and vegetation coverage can explain only part of the variation of sediment yield, and that other impact factors, such as human activities, should be sufficiently considered as well. 相似文献
48.
49.
50.
瓯江河口入海水沙通量的变化规律 总被引:1,自引:0,他引:1
根据瓯江流域圩仁水文站1950-2008年的实测流量资料和1956-1998年的实测输沙量资料,采用水文学和数理统计学方法,分析瓯江河口入海水、沙通量的变化规律及其相关性,并对人类活动的影响进行了探讨。研究结果表明:瓯江多年平均入海流量和悬沙通量分别为442m3/s、61.9kg/s;入海水、沙通量具有明显的年际和季节变化特征,沙通量的变幅要大于水通量;瓯江洪枯季流量、输沙量悬殊,洪峰暴涨暴落,是输水、输沙最集中时期;入海水、沙通量之间具有较好的峰、谷对应关系,但1975年特大洪水导致流域侵蚀模量发生较大变化;紧水滩、石塘水库的建成和运行,对瓯江入海径流起到了明显的调节作用,水沙通量年内分配趋于均匀化。 相似文献