全文获取类型
收费全文 | 1612篇 |
免费 | 6篇 |
国内免费 | 6篇 |
专业分类
安全科学 | 12篇 |
废物处理 | 71篇 |
环保管理 | 82篇 |
综合类 | 528篇 |
基础理论 | 370篇 |
污染及防治 | 372篇 |
评价与监测 | 98篇 |
社会与环境 | 81篇 |
灾害及防治 | 10篇 |
出版年
2018年 | 17篇 |
2017年 | 16篇 |
2016年 | 20篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 70篇 |
2012年 | 23篇 |
2011年 | 47篇 |
2010年 | 47篇 |
2009年 | 50篇 |
2008年 | 68篇 |
2007年 | 55篇 |
2006年 | 48篇 |
2005年 | 49篇 |
2004年 | 42篇 |
2003年 | 37篇 |
2002年 | 48篇 |
2001年 | 60篇 |
2000年 | 54篇 |
1999年 | 35篇 |
1998年 | 20篇 |
1997年 | 30篇 |
1996年 | 28篇 |
1995年 | 30篇 |
1994年 | 28篇 |
1993年 | 26篇 |
1992年 | 19篇 |
1991年 | 36篇 |
1990年 | 51篇 |
1989年 | 23篇 |
1988年 | 27篇 |
1987年 | 20篇 |
1985年 | 21篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 30篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1974年 | 17篇 |
1972年 | 17篇 |
1968年 | 12篇 |
1967年 | 23篇 |
1966年 | 19篇 |
1965年 | 13篇 |
1964年 | 12篇 |
1962年 | 13篇 |
1958年 | 14篇 |
1957年 | 12篇 |
排序方式: 共有1624条查询结果,搜索用时 15 毫秒
991.
The process of steppe pasture digression resulting from grazing by different farm animals was studied by the transect method. Sheep, cattle, and horse pastures under similar grazing loads markedly differed in the dynamics of steppe vegetation. The most critical changes in plant communities occurred in sheep pastures, whereas the state of plant communities in horse pastures was good. 相似文献
992.
993.
We describe a 2-year-old boy with chondrodysplasia punctata (CDP). The boy was exposed to phenytoin, in combination with carbamazepine, during pregnancy. There has been previous evidence for a connection between phenytoin exposure during pregnancy and chondrodysplasia punctata. The boy had clinical and some radiological characteristic features of CDP, of the tibia-metacarpal type. We know of no other report on a child exposed to phenytoin during pregnancy who developed CDP of this type. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
994.
Validation of the CANDY model with Russian long-term experiments 总被引:1,自引:1,他引:0
The CANDY model has been qualitatively assessed for simulating long-term dynamics of soil organic carbon and tested against
different long-term experiments representing various land uses and geographical sites, but never before against conditions
of the Former Soviet Union (FSU). Our goal was to simulate long-term trends in soil organic carbon for the long-term experiments
of Barybino (Moscow region, Russia), Grakov (Kharkow region, Ukraine) and Yachenka (Minsk region, Belarus) representing the
predominant arable soil types, climate conditions and typical management strategies for the investigated arable areas. The
fit of modelled results to the observed data was evaluated to assess the suitability of the model for further applications
in the FSU. The crop parameters of the CANDY model had to be adapted to the low yields observed under the Russian site conditions
resulting in a higher sensitivity to crop-derived carbon input as a function of yield. The results show that the approach
of treating the organic carbon situated in micro pores as inert, is an applicable solution for simulating soil carbon dynamics
under Russian conditions. This evaluation of CANDY, against long-term experiments from Russia, gives confidence for its wider
application in this region. 相似文献
995.
Studies on pigments,proteins and photosynthetic rates in some mangroves and mangrove associates from Bhitarkanika,Orissa 总被引:6,自引:0,他引:6
Pigment contents, proteins and net photosynthesis were investigated in fully developed leaf of 1-year-old seedlings of six mangroves (Bruguiera gymnorrhiza, Rhizophora apiculata) and mangrove associates (Caesalpinia bonduc, Cerbera manghas, Derris heterophylla, Thespesia populnea), collected from Bhitarkanika, located on the east coast of India. Large variations in the photosynthetic rates (PN) among the six species were observed, ranging from 10.16 µmol CO2 m-2 s-1 in C. bonduc to 15.28 µmol CO2 m-2 s-1 in R. apiculata. The total leaf protein content ranged from 12.09 mg g-1 dry wt in T. populnea to 51.89 mg g-1 dry wt in B. gymnorrhiza. The chlorophyll a/b ratio was typically about 3.0 in all the studied species, except C. bonduc (2.8). Photosynthetic rates and chl a/b ratio in the leaves were found to be correlated. Analysis of chlorophyll and xanthophyll spectra suggested: (1) variations in different forms and amounts of carotenes as well as xanthophylls and (2) the presence of high amounts of near-UV-absorbing substances in leaves, particularly in the two mangroves (B. gymnorrhiza, R. apiculata) and a mangrove associate (T. populnea), which appears to be an adaptive feature. Estimation of the chl a/b ratios in isolated thylakoids yielded a low value of 1.8 for R. apiculata and >2.6 for other species. The total protein/chlorophyll ratios in thylakoids varied considerably from 3.14 (D. heterophylla) to 10.88 (T. populnea) among the mangrove associates and from 16.09 to 18.88 between the members of the Rhizophoraceae. The chlorophyll/carotenoid ratios in thylakoids of the six species were more or less similar. The absorption spectra for washed thylakoids of C. manghas and D. heterophylla exhibited absorption characteristics typical for C3-plant thylakoids. However, thylakoids isolated from R. apiculata, B. gymnorrhiza, C. bonduc and T. populnea exhibited an unusual increase in absorption in the blue region (380-410 nm) of the absorption spectrum. The presence of high-absorbing (in the short-wavelength, near-UV region) pigments appears to be closely associated with the thylakoids in R. apiculata and T. populnea. Our results, therefore, suggest a wide range of variation, not only in protein and pigment contents of photosynthetic tissues, but also in the spectral characteristics and composition of the pigments in mangrove species. An understanding of the nature of these pigments in mangroves and their associates, under their natural conditions and especially in relation to eco-physiological adaptations, is necessary, not only in relation to conservation, but also to allow propagation under different salinity conditions. 相似文献
996.
J A Libra C Sahlmann A Schuchardt J Handschag U Wiesmann R Gnirss 《Water environment research》2005,77(5):447-454
The aeration systems of two full-scale, activated-sludge basins were compared during a period of three years, under the same operating conditions, using dynamic offgas testing. Only the material of the diffuser was different (membrane versus ceramic-tube diffusers). The investigation has shown that, although the membrane diffusers have higher initial standard-oxygen-transfer efficiency (alphaSOTE) and standard-aeration efficiency (alphaSAE), these decreased over time, while the alphaSAE of the ceramic diffusers started lower, but increased slightly over the whole period. A cost comparison makes clear how important it is to evaluate the aeration system under process conditions. The operating costs were the dominant factor (approximately 10x higher than capital costs), and operating costs were approximately 20% higher for membrane versus ceramic diffusers. The poor performance of the membrane-tube diffusers under process conditions could be explained on the basis of the actual alphaAE values in the basin, not the standardized values. 相似文献
997.
Profiles of alkyl homologues and isomers of LAS were monitored for an urban stream polluted with municipal wastewaters in Korea. Alkylchains of the stream LAS were shorter than commercial standards and higher I/E ratios were associated with lower LAS concentrations. These suggested a partial biodegradation of LAS in the stream. Higher LAS concentrations were observed in the upper stream. LAS levels were at their lowest during summer probably due to high precipitation and faster biodegradation rates. LAS contributed to about 29% of MBAS and could be used to roughly estimate BOD concentration of the stream. 相似文献
998.
Curtis C. J. Barbieri A. Camarero L. Gabathuler M. Galas J. Hanselmann K. Kopaček J. Mosello R. Nickus U. Rose N. Stuchlik E. Thies H. Ventura M. Wright R. 《Water, Air, & Soil Pollution: Focus》2002,2(2):115-126
Critical load models for acidityprovide a measure of the sensitivity of surfacewaters to acid deposition, and can be used todetermine critical load exceedance and potentiallong-term harmful effects. Three static models,the Steady-State Water Chemistry model, diatommodel and First-order Acidity Balance model, arehere applied to 11 high mountain lakes in Norway,Scotland, the Alps, the Pyrenees and the Tatras.Between five and seven of the lakes show criticalload exceedance, depending on the model used.Nitrogen as well as sulphur deposition isimportant in causing exceedance. Since soil andvegetation cover are generally sparse, geologyand lake retention time appear to be key factorsin the determination of critical load. Retentionof nitrogen is observed, but it is unclearwhether this occurs within the lake or theterrestrial part of the catchment. 相似文献
999.
Phase space prediction is a feature selection method which triesto exploit non-linear dynamics of an underlying system. We describe and offer a critical reconsideration of this approach,discuss questions of whether non-linear methods are justified by the data, and apply them to ozone time series from single locations. Our main objectives are to obtain air quality forecasts in order to provide public health warnings and to provide an insight into the dynamics of the underlying system.Interestingly, comparable linear data sets (surrogates)have very similar structure and give similar predictionaccuracy to that of the ozone data. In this instance theredoes not appear to be any advantage to applying the phasespace approach to univariate time series. 相似文献
1000.
Höllriegl V Greiter M Giussani A Gerstmann U Michalke B Roth P Oeh U 《Journal of environmental radioactivity》2007,95(2-3):149-160
The study investigated the changes in urinary thorium excretion by humans following ingestion of a therapeutic soil, which contains about 10 ppm of thorium. This well-known healing earth in Germany has been considered as an alternative medicine for diarrhoea and gastric hyper-acidity. Six adult volunteers ingested this therapeutic soil in varying quantities for 1-15 days at levels approximating those described in the package insert of the medicine (10-60 g of soil per day). The subjects ingested about 0.1-0.6 mg of thorium daily, which is 100-600 times higher than the normal daily intake of about 1 microg thorium in Germany. All 24-h urine samples collected from the subjects during pre-ingestion, ingestion and post-ingestion periods of the soil were analyzed for (232)Th using inductively coupled plasma mass spectrometry (ICP-MS). The measured excretion values varied in a wide range. Apparently, the high thorium amounts administered did not increase the (232)Th excretion in urine as expected, suggesting that this soil ingestion will not result in a considerably higher and harmful uptake of thorium into the human body. 相似文献