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401.
David R. Brillinger 《Journal of the American Water Resources Association》1985,21(5):743-756
Fourier inference is a collection of analytic techniques and philosophic attitudes, for the analysis of data, wherein essential use is made of empirical Fourier transforms. This paper sets down some basic results concerning the finite Fourier transforms of stationary process data and then, to illustrate the approach, uses those results to develop procedures for: 1) estimating cloud and storm motion, 2) passive sonar and 3) fitting finite parameter models to nonGaussian time series via bispectral fitting. This last procedure is illustrated by an analysis of a stretch of Mississippi River runoff data. Examples 1), 2) refer to data having the form Y(xj, yj, t) for j = 1, …, J and t = 0, …, T-l say, and view that data as part of a realization of a spatial-temporal process. Such data has become common in geophysics generally and in hydrology particularly. The goal of this paper is to present some new statistical procedures pertinent to problems in the water sciences, equally it is to illustrate the genesis of those procedures and how their properties may be approximated. 相似文献
402.
Much attention has been invested in the model choice problem for peak annual flows, in the context of flood frequency analysis. The authors would sidestep this dilemma through non-parametric density estimation methodology, but recognize that the standard nonparametric estimators preclude the use of prior information and related data, and furthermore have virtually no tail at all. Here we offer a remedy for these inadequacies by introducing an estimator which mixes parametric and nonparametric density estimates. We prove that our mixture rule is consistent. By this procedure, we do allow incorporation of prior information, experience, and regional data information, but nevertheless provide a safeguard against incorrect model choice. 相似文献
403.
Vujica Yevjevich Nilgun Bayraktar Harmancioglu 《Journal of the American Water Resources Association》1985,21(4):625-633
ABSTRACT: water resources supply and demand time series consist of several or all of the four basic characteristics: tendency, intermittency, periodicity and stochasticity. Their importance changes from one type of variables to another. Historic developments of analysis of time series in hydrology have varied significantly over the past, from the stress on search for periodicities and persistence in annual series to the emphasis on the series stochastic properties. Supply and demand series are often highly interrelated, which fact is most often neglected in planning water resources systems in general, and water storage capacities in particular. The future of series analysis in water resources will likely be by a joint use of physically-based structural analysis and the use of advanced methods of treating data by stochastic processes, statistical estimation and inference techniques. The most intriguing challenge of the future of this analysis may be the treatment of nonnormal, nonlinear and in general nonstationary hydrologic and water use time series. The proper treatment of complex multivariate processes will also challenge the specialists, especially for the purposes of transfer of information between data on variables at given points, or between data at several points of a given variable, or both. 相似文献
404.
Fölster J Göransson E Johansson K Wilander A 《Environmental monitoring and assessment》2005,102(1-3):389-403
Variation in water chemistry was studied in 80 lakes in southern Sweden. The lakes had forest dominated catchments. The length of the time series was 14 years. Synchrony was calculated as Pearsons product moment correlation coefficients for all combinations of lakes, i.e. 3160 lake-pairs. The chemical variables studied were non-marine sulphate (SO4
*), non-marine calcium (Ca*), absorbance and acid neutralising capacity (ANC). Statistically significant synchrony occurred in 93% of all lake-pairs for SO4
*, and between 58 and 67% for absorbance, Ca* and ANC. In 70% of all lake-pairs, the synchrony was \s>0.71 for SO4
*, which means that more than half of the variation in one lake could be explained by the variation in the other lake. For absorbance, Ca* and ANC, about 25% of the lake-pairs had a synchrony \s>0.71. The relatively high synchrony for SO4
* occurred during an overall downward trend in SO4
* concentration.The degree of synchrony in our study was at a level comparable to other studies in northern America and England. However, our study included lakes in a much larger area, with distances of up to 500 km between the lakes, while earlier studies were made on small lake districts with lakes located within approximately 50 km. In contrast to these earlier studies, there was no correlation between synchrony and distance, lake characteristics or catchment characteristics. However, when a small subset of 15 lakes in the southeast of Sweden was selected, such relations were found. 相似文献
405.
酒石酸钾钠溶液对氨氮标准曲线的影响 总被引:1,自引:0,他引:1
通过对酒石酸钾钠溶液存放时间和保存条件的跟踪试验,发现该试剂的存放时间越长,绘制的氨氮标准曲线的截距就越大;并分析了在绘制氨氮标准曲线时显色液易浑浊和截距常常偏大的原因;就此提出了酒石酸钾钠溶液的有效期和保存方法,以进一步提高氨氮测定的准确度。 相似文献
406.
本文利用曲线补偿,变时溶出示差技术提高了测定Cu、Pb、Zn、Cd的灵敏度、精密度和准确度,进一步改变了谱图的分辨率,避免了O2波的干扰 相似文献
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