全文获取类型
收费全文 | 35057篇 |
免费 | 5229篇 |
国内免费 | 30591篇 |
专业分类
安全科学 | 2958篇 |
废物处理 | 1844篇 |
环保管理 | 2928篇 |
综合类 | 41212篇 |
基础理论 | 5881篇 |
环境理论 | 2篇 |
污染及防治 | 11280篇 |
评价与监测 | 2365篇 |
社会与环境 | 1044篇 |
灾害及防治 | 1363篇 |
出版年
2024年 | 25篇 |
2023年 | 403篇 |
2022年 | 1212篇 |
2021年 | 1085篇 |
2020年 | 1433篇 |
2019年 | 2549篇 |
2018年 | 2879篇 |
2017年 | 3061篇 |
2016年 | 2817篇 |
2015年 | 3405篇 |
2014年 | 4219篇 |
2013年 | 5048篇 |
2012年 | 4432篇 |
2011年 | 4226篇 |
2010年 | 3597篇 |
2009年 | 3693篇 |
2008年 | 3539篇 |
2007年 | 3277篇 |
2006年 | 2894篇 |
2005年 | 2090篇 |
2004年 | 1666篇 |
2003年 | 1528篇 |
2002年 | 1361篇 |
2001年 | 1218篇 |
2000年 | 1399篇 |
1999年 | 1282篇 |
1998年 | 995篇 |
1997年 | 921篇 |
1996年 | 904篇 |
1995年 | 762篇 |
1994年 | 560篇 |
1993年 | 448篇 |
1992年 | 465篇 |
1991年 | 350篇 |
1990年 | 281篇 |
1989年 | 226篇 |
1988年 | 172篇 |
1987年 | 91篇 |
1986年 | 84篇 |
1985年 | 56篇 |
1984年 | 57篇 |
1983年 | 44篇 |
1982年 | 49篇 |
1981年 | 37篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1972年 | 6篇 |
1971年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
研制了一种测定水中Mg2 + 的测试管 ,测定范围为 0 .5mg/L~ 2 .0mg/L。该测试管适用于现场应急监测 ,具有快速、简便、抗干扰能力强和价格低廉等特点 相似文献
202.
利用2017—2018年全国7个区域10个典型城市环境空气O3和PM2.5浓度数据,统计污染物累积速率,进而采用回归方法拟合污染物浓度及其累积速率的时间序列模型,分析不同区域污染物时序变化特征差异。结果表明:不同区域O3浓度时序曲线拟合程度总体高于PM2.5,石家庄O3拟合程度最高,西安PM2.5拟合程度最高。以07:00、14:00分别作为O3、PM2.5模拟起点是24 h中的最优模型。不同城市夏季O3小时浓度时序变化曲线均为单峰形态,O3浓度及累积速率峰值出现时间可能由城市所处经度决定,太原O3累积最快,西安O3消解最快。各城市间冬季PM2.5小时浓度及其累积速率时序变化曲线形态差异较大,沈阳PM2.5累积和消解均最快。与浓度相比,城市环境空气O3和PM2.5累积速率与光照、扩散条件等有更好的时间相关性。 相似文献
203.
连续采样与五日法采样效果及费用的对比分析 总被引:2,自引:0,他引:2
通过对连续采样与五日法采样五种方法监测结果及所需费用的比较,得出连续采样方法监测结果更具有代表性,合理性,一次性投资大,但运行费用并不高的结论。 相似文献
204.
Wuncheng Wang 《Environmental monitoring and assessment》1993,24(3):257-265
Paper substrate, especially circular filter paper placed inside a Petri dish, has long been used for the plant seed toxicity test (PSTT). Although this method is simple and inexpensive, recent evidence indicates that it gives results that are significantly different from those obtained using a method that does not involve paper, especially when testing metal cations. The study compared PSTT using three methods: filter paper, Growth Pouch-TM, and seed tray. The Growth Pouch-TM is a commercially available device. The seed tray is a newly designed plastic receptacle placed inside a Petri dish. The results of the Growth Pouch-TM method showed no toxic effects on rice for Ag up to 40 mg L–1 and Cd up to 20 mg L–1. Using the seed tray method, IC50 (50% inhibitory effect concentration) values were 0.55 and 1.4 mg L–1 for Ag and Cd, respectively. Although results of filter paper and seed tray methods were nearly identical for NaF, Cr(VI), and phenol, the toxicities of cations Ag and Cd were reduced by using the filter paper method; IC50 values were 22 and 18 mg L–1, respectively. The results clearly indicate that paper substrate is not advisable for PSTT. 相似文献
205.
Faculty position announcement 相似文献
206.
Yafa C Farmer JG Graham MC Bacon JR Barbante C Cairns WR Bindler R Renberg I Cheburkin A Emons H Handley MJ Norton SA Krachler M Shotyk W Li XD Martinez-Cortizas A Pulford ID MacIver V Schweyer J Steinnes E Sjøbakk TE Weiss D Dolgopolova A Kylander M 《Journal of environmental monitoring : JEM》2004,6(5):493-501
Given the increasing interest in using peat bogs as archives of atmospheric metal deposition, the lack of validated sample preparation methods and suitable certified reference materials has hindered not only the quality assurance of the generated analytical data but also the interpretation and comparison of peat core metal profiles from different laboratories in the international community. Reference materials play an important role in the evaluation of the accuracy of analytical results and are essential parts of good laboratory practice. An ombrotrophic peat bog reference material has been developed by 14 laboratories from nine countries in an inter-laboratory comparison between February and October 2002. The material has been characterised for both acid-extractable and total concentrations of a range of elements, including Al, As, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Na, Ni, P, Pb, Ti, V and Zn. The steps involved in the production of the reference material (i.e. collection and preparation, homogeneity and stability studies, and certification) are described in detail. 相似文献
207.
Using improved neural network model to analyze RSP,NOx and NO2 levels in urban air in Mong Kok,Hong Kong 总被引:4,自引:0,他引:4
As the health impact of air pollutants existing in ambient addresses much attention in recent years, forecasting of airpollutant parameters becomes an important and popular topic inenvironmental science. Airborne pollution is a serious, and willbe a major problem in Hong Kong within the next few years. InHong Kong, Respirable Suspended Particulate (RSP) and NitrogenOxides NOx and NO2 are major air pollutants due to thedominant diesel fuel usage by public transportation and heavyvehicles. Hence, the investigation and prediction of the influence and the tendency of these pollutants are ofsignificance to public and the city image. The multi-layerperceptron (MLP) neural network is regarded as a reliable andcost-effective method to achieve such tasks. The works presentedhere involve developing an improved neural network model, whichcombines the principal component analysis (PCA) technique and theradial basis function (RBF) network, and forecasting thepollutant levels and tendencies based in the recorded data. Inthe study, the PCA is firstly used to reduce and orthogonalizethe original input variables (data), these treated variables arethen used as new input vectors in RBF neural network modelestablished for forecasting the pollutant tendencies. Comparingwith the general neural network models, the proposed modelpossesses simpler network architecture, faster training speed,and more satisfactory predicting performance. This improvedmodel is evaluated by using hourly time series of RSP, NOx and NO2 concentrations collected at Mong Kok Roadside Gaseous Monitory Station in Hong Kong during the year 2000. By comparing the predicted RSP, NOx and NO2 concentrationswith the actual data of these pollutants recorded at the monitorystation, the effectiveness of the proposed model has been proven.Therefore, in authors' opinion, the model presented in the paper is a potential tool in forecasting air quality parameters and hasadvantages over the traditional neural network methods. 相似文献
208.
209.
210.