全文获取类型
收费全文 | 19543篇 |
免费 | 298篇 |
国内免费 | 466篇 |
专业分类
安全科学 | 712篇 |
废物处理 | 940篇 |
环保管理 | 2848篇 |
综合类 | 3244篇 |
基础理论 | 4838篇 |
环境理论 | 8篇 |
污染及防治 | 5326篇 |
评价与监测 | 1170篇 |
社会与环境 | 1082篇 |
灾害及防治 | 139篇 |
出版年
2023年 | 105篇 |
2022年 | 203篇 |
2021年 | 204篇 |
2020年 | 200篇 |
2019年 | 190篇 |
2018年 | 353篇 |
2017年 | 324篇 |
2016年 | 487篇 |
2015年 | 382篇 |
2014年 | 511篇 |
2013年 | 1575篇 |
2012年 | 731篇 |
2011年 | 1019篇 |
2010年 | 757篇 |
2009年 | 877篇 |
2008年 | 951篇 |
2007年 | 1002篇 |
2006年 | 836篇 |
2005年 | 705篇 |
2004年 | 718篇 |
2003年 | 653篇 |
2002年 | 618篇 |
2001年 | 691篇 |
2000年 | 547篇 |
1999年 | 336篇 |
1998年 | 228篇 |
1997年 | 247篇 |
1996年 | 236篇 |
1995年 | 282篇 |
1994年 | 226篇 |
1993年 | 224篇 |
1992年 | 184篇 |
1991年 | 198篇 |
1990年 | 189篇 |
1989年 | 189篇 |
1988年 | 160篇 |
1987年 | 135篇 |
1986年 | 163篇 |
1985年 | 150篇 |
1984年 | 198篇 |
1983年 | 154篇 |
1982年 | 179篇 |
1981年 | 163篇 |
1980年 | 139篇 |
1979年 | 152篇 |
1978年 | 99篇 |
1977年 | 100篇 |
1974年 | 97篇 |
1973年 | 90篇 |
1972年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
451.
M. L. Amadori C. Del Vais P. Fermo P. Pallante 《Environmental science and pollution research international》2017,24(16):13921-13949
The aim of this study is to setup a first chemical database that could represent the starting point for a reliable classification method to discriminate between Archaic Phoenician and Punic pottery on the base of their chemical data. This database up to now can discriminate between several different areas of production and provenance and can be applied also to unknown ceramic samples of comparable age and production areas. More than 100 ceramic fragments were involved in this research, coming from various archaeological sites having a crucial importance in the context of the Phoenician and Punic settlement in central and western Mediterranean: Carthage (Tunisia), Toscanos (South Andalusia, Spain), Sulci, Monte Sirai, Othoca, Tharros (Sardinia, Italy) and Pithecusa (Campania, Italy). Since long-time archaeologists hypothesised that Mediterranean Archaic Phoenician and Punic pottery had mainly a local or just a regional diffusion, with the exception of some particular class like transport amphorae. To verify the pottery provenance, statistical analyses were carried out to define the existence of different ceramic compositional groups characterised by a local origin or imported from other sites. The existing literature data are now supplemented by new archaeometric investigations both on Archaic Phoenician ceramics and clayey raw materials from Sardinia. Therefore, diffractometric analyses, optical microscopy observations and X-ray fluorescence analyses were performed to identify the mineralogical and chemical composition of Othoca ceramics and clayey raw material. The obtained results were then compared with own literature data concerning Phoenician and Punic pottery in order to find features related to the different ceramic productions and their provenance. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were also performed on the chemical compositional data in order to discriminate ceramic groups. A very complex situation was found: imported ceramics coming from Carthage, with a large-scale distribution, were found together with a predominant local production pottery. The archaeometric results demonstrate that historical and typological approach has to be supported by scientific analyses to better understand local or Mediterranean exchanges. 相似文献
452.
Chukwujindu M. A. Iwegbue Godwin E. Nwajei Jude E. Ogala Chukwudumebi L. Overah 《Environmental geochemistry and health》2010,32(5):415-430
The concentrations of trace metals (Cd, Pb, Cu, Cr, Fe, Ni, Zn and Co) were studied in soil profiles of eight municipal waste
dump sites in Warri metropolis. The results indicate that concentrations of trace metals varied widely among the different
dumpsites and decreased with depths in a studied soil profile. The accumulation pattern for the heavy metals in the soil profiles
follows the order: Fe > Pb > Mn > Co > Cr > Zn > Ni > Cu > Cd. The concentrations of metals found in these sites was below
the Canadian remediation criteria for land for agricultural, residential and commercial/industrial purposes except for the
cadmium levels in some sites that exceeded criterion values for agricultural and residential. In such sites, remedial actions
are required before any form of chosen development can take place. The levels of heavy metals found in these dump sites were
higher than that of the control site. The examined metals showed no significant correlation with soil physicochemical properties
at the surface horizon, which is suggestive evidence that these metals arise from anthropogenic input. 相似文献
453.
Sellin Arne Alber Meeli Keinänen Markku Kupper Priit Lihavainen Jenna Lõhmus Krista Oksanen Elina Sõber Anu Sõber Jaak Tullus Arvo 《Regional Environmental Change》2017,17(7):2135-2148
Regional Environmental Change - Increasing atmospheric humidity—a climate trend predicted for northern Europe—will reduce water flux through vegetation. Diminished transpirational water... 相似文献
454.
BRENT J. SEWALL AMY L. FREESTONE MOHAMED F. E. MOUTUI NASSURI TOILIBOU ISHAKA SAÏD SAINDOU M. TOUMANI DAOUD ATTOUMANE CHEIKH M. IBOURA 《Conservation biology》2011,25(4):688-696
Abstract: Systematic conservation assessment (an information‐gathering and prioritization process used to select the spatial foci of conservation initiatives) is often considered vital to conservation‐planning efforts, yet published assessments have rarely resulted in conservation action. Conservation assessments may lead more directly to effective conservation action if they are reoriented to inform conservation decisions. Toward this goal, we evaluated the relative priority for conservation of 7 sites proposed for the first forest reserves in the Union of the Comoros, an area with high levels of endemism and rapidly changing land uses in the western Indian Ocean. Through the analysis of 30 indicator variables measured at forest sites and nearby villages, we assessed 3 prioritization criteria at each site: conservation value, threat to loss of biological diversity from human activity, and feasibility of reserve establishment. Our results indicated 2 sites, Yiméré and Hassera‐Ndrengé, were priorities for conservation action. Our approach also informed the development of an implementation strategy and enabled an evaluation of previously unexplored relations among prioritization criteria. Our experience suggests that steps taken to ensure the closer involvement of practitioners, include a broader range of social data, encourage stakeholder participation, and consider the feasibility of conservation action can improve the relevance of assessments for conservation planning, strengthen the scientific basis for conservation decisions, and result in a more realistic evaluation of conservation alternatives. 相似文献
455.
T. Glytsos J. Ondráček L. Džumbová I. Kopanakis M. Lazaridis 《Atmospheric environment (Oxford, England : 1994)》2010,44(12):1539-1549
Indoor sources have been identified as a major contributor to the increase of particle concentration in indoor environments. The work presented here is a study of the characteristics of particulate matter number size distribution and mass concentration under controlled indoor activities in a laboratory room. The objective is to characterize particulate matter concentrations indoors resulted under the influence of specific sources. Measurements were performed in an empty laboratory (period September–October 2006) using a GRIMM SMPS+C system (particle size range between 11.1 and 1083.3 nm), a DustTrak Aerosol Monitor (TSI) and a P-Trak Ultrafine Particle Counter (TSI). The studied indoor activities included candle burning, hot plate heating, water boiling, onion frying, vacuuming, hair drying, hair spraying, smoking and burning of incense stick. The AMANpsd computer algorithm was used to evaluate the modal structure of measured particle number size distribution data. Furthermore, the change of the particle number size distribution shape under the influence of different emission sources was studied versus time. Finally the particle emission rates were computed. High particle number concentrations were observed during smoking, onion frying, candle burning and incense stick burning. The highest particle mass concentrations were measured during smoking and hair spraying. The shift of the particle size distribution to larger diameters suggests the presence of strong coagulation effect during candle burning, incense stick burning, smoking and onion frying. The size distribution was mainly bimodal during onion frying and candle burning, whereas the size distribution remained unimodal during incense stick burning and smoking experiments. 相似文献
456.
Patrick L. Hanrahan 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1332-1338
ABSTRACT A previous paper1 discusses the methodology for a new method for deriving the nitrogen dioxide/nitrogen oxide (NO2/NOx) ratio in plumes that originally are composed mainly of (NOx). It is called the Plume Volume Molar Ratio Method (PVMRM). This paper documents its performance against six different data sets. These performance evaluations show that the PVMRM can realistically predict the NO2 fraction at close-in receptors yet still provide conservative estimates so that the air quality standards can be protected. 相似文献
457.
458.
A. P. Altshuller S. L. Kopczynski D. Wilson W. Lonneman F. D. Sutterfield 《Journal of the Air & Waste Management Association (1995)》2013,63(10):791-794
Effects associated with photochemical air pollution were measured during irradiation of n-butane-nitrogen oxide or n-butane-ethane-nitrogen oxide mixtures, with small amounts of propylene or toluene added. The effects measured including nitrogen dioxide and oxidant dosages, yields of formaldehyde and peroxy-acetyl nitrate, and eye irritation response. The results obtained clearly show that beneficial effects result from selective changes in hydrocarbon composition as well as from reduction of total hydrocarbon concenfration. Exclusion of olefins and alkylbenzenes was highly effective in reducing oxidant dosage, formaldehyde and peroxyacetyl nitrate concentrations, and eye irritation response. The only penalty was a modest increase in nitrogen dioxide dosage. A large reduction in nitrogen oxide concentration reduced nitrogen dioxide dosage and eye irritation response, but with the penalty of a large increase in oxidant dosage. The desirability of preferentially reducing olefins and alkylbenzenes rather than paraffinic hydrocarbons, acetylene, and benzene is strongly supported by this study. Research and development efforts should be directed toward preferential hydrocarbon control by mechanical or catalytic control 相似文献
459.
460.
REED F. NOSS ERICA FLEISHMAN† DOMINICK A. DELLASALA‡ JOHN M. FITZGERALD§ MART R. GROSS MARTIN B. MAIN†† FIONA NAGLE‡‡ STACEY L. O'MALLEY JON ROSALES§§ 《Conservation biology》2009,23(4):825-833
Abstract: The Society for Conservation Biology (SCB) can enhance conservation of biodiversity in North America by increasing its engagement in public policy. Toward this end, the North America Section of SCB is establishing partnerships with other professional organizations in order to speak more powerfully to decision makers and taking other actions—such as increasing interaction with chapters—geared to engage members more substantively in science-policy issues. Additionally, the section is developing a North American Biodiversity Blueprint, which spans the continental United States and Canada and is informed by natural and social science. This blueprint is intended to clarify the policy challenges for protecting continental biodiversity, to foster bilateral collaboration to resolve common problems, and to suggest rational alternative policies and practices that are more likely than current practices to sustain North America's natural heritage. Conservation scientists and practitioners can play a key role by drawing policy makers' attention to ultimate, as well as proximate, causes of biodiversity decline and to the ecological and economic consequences of not addressing these threats. 相似文献