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51.
52.
Determination of alkali-labile phosphoprotein phosphorus from fish plasma using the Tb^3+-tiron complex as a fluorescence probe 总被引:1,自引:0,他引:1
A sensitive method based on the fluorescence quenching effect of the Tb^3+-Tiron complex is proposed for the determination of alkali-labile phosphoprotein phosphorus (ALP) released from fish plasma. The detection limit was 5.4 ng/ml (S/N=2), and the relative standard deviation of the quenching effect (6 replicates) was 4.6%. The results obtained by the proposed method were in good agreement with those obtained by the colorimetric assay. The advantages of the present method are its relatively simple detection procedure, the lack of toxic organic solvents, and high sensitivity. 相似文献
53.
水中总氮测定相关问题的实验探讨 总被引:1,自引:0,他引:1
通过对国家标准测定方法《碱性过硫酸钾消解紫外分光光度法》进行水样中总氮的测定,进一步理解在220nm、275nm波长处进行吸光度测定的重要性。并提出:在已经知道水样中没有氨氮、亚硝酸盐氮,只有硝酸盐氮的情况下.就能通过快速的方法一即不加氧化剂、不加压,可以进行总无机氮的测定。快速测定无机总氮对于工程应用来说很有意义。因为国标的方法需要半天时间测定。而用此方法则仅需几分钟就可完成测定。、另外对于有机物对于测定结果的影响,参考吸光度比值(A275/A220×100%)应小于20%,越小越好,超过时应予鉴别。 相似文献
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针对数值模拟参数选取主观性强、量化难度大的问题,在高精度无人机地形数据的基础上,通过对11起滑坡案例进行了407组参数反演实验,对结果准确度定量评价后,得到基于Massflow数值软件关键参数λ0的分布范围,进而运用小样本极大似然估计理论,分析区间边界长度对反演精度的影响,最终提出基于均匀分布的参数取值概率模型,并选用案例验证该模型的准确性。结果表明:地形约束会导致反演过程中所需的内聚力减小,反演获得的11组最优λ0的极差和方差分别为0.29、0.01,在置信度为95%下,极大似然法得到区间边界估计长度仅为0.0998,表明参数λ收敛性较好;反演过程中质心滑动距离ψ准确度优于堆积面积重叠率η,在λ0±0.05的范围,参数估计区间内任意值对模拟误差影响较小,评价指标ψ、η与λ0对应案例的相对误差不超过15%;所选案例验证了在置信度为95%下,以反演得到的最优参数区间边界中点构建概率分布函数的可行性和准确性,研究方法可为单体滑坡数值模拟风险评价提供理论支撑。 相似文献
56.
《International Journal of Sustainable Engineering》2013,6(2):106-120
There is a widespread recognition of the need for better information sharing and provision to improve the viability of end-of-life (EOL) product recovery operations. The emergence of automated data capture and sharing technologies such as RFID, sensors and networked databases has enhanced the ability to make product information; available to recoverers, which will help them make better decisions regarding the choice of recovery option for EOL products. However, these technologies come with a cost attached to it, and hence the question ‘what is its value?’ is critical. This paper presents a probabilistic approach to model product recovery decisions and extends the concept of Bayes' factor for quantifying the impact of product information on the effectiveness of these decisions. Further, we provide a quantitative examination of the factors that influence the value of product information, this value depends on three factors: (i) penalties for Type I and Type II errors of judgement regarding product quality; (ii) prevalent uncertainty regarding product quality and (iii) the strength of the information to support/contradict the belief. Furthermore, we show that information is not valuable under all circumstances and derive conditions for achieving a positive value of information. 相似文献
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David H. Moreau 《Journal of the American Water Resources Association》1991,27(1):117-123
ABSTRACT: A risk-based model is presented for determining action levels in real-time operation of public water supplies under drought conditions. The model, applicable to surface water supplies, is built around the almost universally adopted structure for drought management, a sequence of increasingly stringent measures to reduce demand. Action levels are determined by finding minimum storage levels that will satisfy a prescribed set of probability constraints over the remainder of a drawdown-refill cycle. Results are presented for the City of Raleigh, NC. 相似文献
59.
Malcolm J. R. Clark Paul H. Whitfield 《Journal of the American Water Resources Association》1994,30(6):1063-1079
ABSTRACT: Current conventions for reporting analytical results from environmental samples brings the objectives of laboratory scientists into conflict with those of environmental scientists. The objective of chemical analyses is to provide estimates of the true composition of samples. Reported results must reflect the analytical uncertainty. Current conventions require left-censoring of those results below the Limit of Detection. The objective of statistical interpretation of environmental data is to provide estimates of the characteristics of ecosystems. Such statistical analyses are often confounded by left-censoring of analytical results. We review the different points of view and propose a compromise which recognizes these conflicting perspectives. 相似文献
60.
James P. Hughes Steven P. Millard 《Journal of the American Water Resources Association》1988,24(3):521-531
ABSTRACT: A common problem arises in testing for trends in water quality when observations are reported as “less than detection limit.” If a single detection limit is used for the entire study, existing non-parametric statistical methods, modified for ties, are applicable. If, however, the detection limit varies during the course of the study, resulting in multiple detection limits, then the commonly used trend detection methods are not appropriate. A statistic similar to Kendall's tau, but based on expected ranks, is proposed. Monte Carlo simulations show that the normal approximation to the distribution of this statistic is quite good, even for small samples and a large proportion of censored observations. The statistic is also shown to have greater power than the ad-hoc method of treating all observations less than the target censored observation as tied. 相似文献