全文获取类型
收费全文 | 27323篇 |
免费 | 367篇 |
国内免费 | 461篇 |
专业分类
安全科学 | 912篇 |
废物处理 | 1100篇 |
环保管理 | 3945篇 |
综合类 | 4767篇 |
基础理论 | 7111篇 |
环境理论 | 14篇 |
污染及防治 | 7012篇 |
评价与监测 | 1597篇 |
社会与环境 | 1490篇 |
灾害及防治 | 203篇 |
出版年
2022年 | 254篇 |
2021年 | 246篇 |
2020年 | 248篇 |
2019年 | 229篇 |
2018年 | 419篇 |
2017年 | 385篇 |
2016年 | 592篇 |
2015年 | 491篇 |
2014年 | 673篇 |
2013年 | 2137篇 |
2012年 | 891篇 |
2011年 | 1290篇 |
2010年 | 1017篇 |
2009年 | 1147篇 |
2008年 | 1255篇 |
2007年 | 1281篇 |
2006年 | 1081篇 |
2005年 | 933篇 |
2004年 | 898篇 |
2003年 | 870篇 |
2002年 | 823篇 |
2001年 | 1023篇 |
2000年 | 786篇 |
1999年 | 495篇 |
1998年 | 332篇 |
1997年 | 359篇 |
1996年 | 360篇 |
1995年 | 422篇 |
1994年 | 378篇 |
1993年 | 338篇 |
1992年 | 289篇 |
1991年 | 324篇 |
1990年 | 309篇 |
1989年 | 314篇 |
1988年 | 250篇 |
1987年 | 222篇 |
1986年 | 254篇 |
1985年 | 222篇 |
1984年 | 279篇 |
1983年 | 240篇 |
1982年 | 266篇 |
1981年 | 243篇 |
1980年 | 213篇 |
1979年 | 245篇 |
1978年 | 157篇 |
1977年 | 166篇 |
1975年 | 154篇 |
1974年 | 145篇 |
1973年 | 145篇 |
1972年 | 154篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Tanay B. Yıldırım Tutku Ak Zuhal Ölmez 《Environment, Development and Sustainability》2008,10(6):871-881
While the world is going into different tourism expectations, the tourism understanding in Turkey is defined as tourism in the sea-sand-sun triangle. However, it is possible to contribute to the income and local development of the indigenous people by developing nature-based tourism. Besides, with the sustainable use and preservation of the natural-cultural assets, the damage of the traditional tourism industry on the natural and cultural environment could be reduced. In this study, it is aimed to bring up the nature-based tourism concept in Çanakkale by evaluating the nature-based tourism industry in the general of Turkey and assessing the natural-cultural resources that Çanakkale comprehends. The most important areas that have a nature-based tourism potential in Çanakkale and the tourism activities that are most suitable for these areas have been determined. 相似文献
23.
24.
25.
Rapid growth of clones of the red alga Chondrus crispus: applications in assays of toxic substances and in physiological studies 总被引:1,自引:0,他引:1
Growth rates of excised apical segments from three Chondrus crispus Stackhouse clones were rapid, reproducible and easily measured using simple equipment. Clonal segments exhibited a high degree of phenotypic stability, with coefficients of variation in growth rates being typically less than 5%. Sensitivity of the assay was demonstrated using 24-h pulses of the toxicants Cu2+ (10 to 150 ppb) and the molluscicide Bayluscide (100 to 500 ppb). As a further demonstration of applicability of this assay system, growth rates were measured over two consecutive 24-h photoperiods using a normally pigmented red gametophytic clone and a green colored mutant derived from it. Growth rates were highest in the first hours of the light phase for both clones, with growth of the green mutant being consistently inferior to that of the normally pigmented one. Significant changes were measured with intervals as short as 4 h using only five apical segments for each treatment. The C. crispus assay described is sensitive, relatively rapid, and statistically robust when applied to toxicant testing in seawater and to physiological studies. 相似文献
26.
27.
28.
Jürgen Breitung Dirk Bruns-Nagel Eberhard von Löw Klaus Steinbach Lothar Kaminski Rainer Haas Diethard Gemsa 《Environmental Sciences Europe》1995,7(4):195-200
Within the limits of a feasability study abouton-site bioremediation methods for TNT-contaminated soils, composting was chosen as a very promising and cheap method. This method was critically compared with those described in the literature and was primarily rated under ecotoxicological aspects. The investigated location is the former munition plant «Tanne» in the aerea of Clausthal-Zellerfeld in Lower Saxony, Germany. To estimate the autochtonic microflora, we assessed the number of aerobic heterotrophic bacteria and determined their respiration activity in soils. In addition, we isolated bacteria and examined their capacity to metabolize TNTin vitro. Both the amount of autochtonic microrganisms (4.7×108 to 1.2×1010 colony forming units (cfu)/kg dryweight) as well as their respiration activity did not correlate with the concentrations of nitrotoluenes in the soils. With high contaminated soil (20 g TNT/kg dry weight) we carried out a small compost in the range of 10 liters. During 28 days of composting TNT-concentration decrease over 90% and only minor amounts of monoaminodinitrotoluenes were generated. However, an acidic pretreatment of the compost material at the end of the reaction showed that TNT could be partially resolved under these extreme conditions and that an ecotoxicological risk may still exist. Possible changes in the realization of the composting process in order to make sure that the contaminants are savely bound to the humin matrix are discussed. 相似文献
29.
Certain hydrothermal vent invertebrates, e.g. Riftia pachyptila and Calyptogena magnifica, are clearly established as harboring dense populations of chemoautotrophic sulfur bacteria in specialized tissues. By contrast, the physiological characteristics of the abundant intracellular gill symbiont of the vent mussel Bathymodiolus thermophilus have been questioned. The low activities of enzymes diagnostic for CO2 fixation (Calvin cycle) and for sulfur-driven energy generation, as measured by other investigators, have been attributed to bacterial contamination of the gill surface. Based on research at the Galápagos Rift hydrothermal vents in 1988 and subsequent laboratory experiments, the current study confirms that the B. thermophilus symbiont is a psychrophile for which thiosulfate and sulfide stimulate CO2 fixation. It strongly indicates that the symbiont is a chemoautotroph by establishing the following: (1) Sulfide and thiosulfate can stimulate CO2 fixation by partially purified symbionts by up to 43-fold and 120-fold, respectively; (2) the ribulose-1,5-bisphosphate carboxylase/oxygenase activity of the symbiont is sufficient to account for its sulfide- or thiosulfate-stimulated CO2 incorporation; (3) the symbiont's molar growth yield on thiosulfate, as judged by CO2 incorporation, is indistinguishable from that of free-living chemoautotrophs. Due to the high protein-degrading activity of B. thermophilus gill lysate, it is also suggested that host lysis of symbionts plays a more important role in the nutrition of the vent mussel than in R. pachyptila or C. magnifica, for which no comparable protein-degrading activity was found. 相似文献
30.
CARMEL L. WITTE§ MICHAEL J. SREDL† REW S. KANE§‡ LAURA L. HUNGERFORD†† 《Conservation biology》2008,22(2):375-383
Abstract: We examined factors that may independently or synergistically contribute to amphibian population declines. We used epidemiologic case–control methodology to sample and analyze a large database developed and maintained by the Arizona Game and Fish Department that describes historical and currently known ranid frog localities in Arizona, U.S.A. Sites with historical documentation of target ranid species ( n = 324) were evaluated to identify locations where frogs had disappeared during the study period (case sites) and locations where frog populations persisted (control sites). Between 1986 and 2003, 117 (36%) of the 324 sites became case sites, of which 105 were used in the analyses. An equal number of control sites were sampled to control for the effects of time. Risk factors, or predictor variables, were defined from environmental data summarized during site surveys and geographic information system data layers. We evaluated risk factors with univariate and multifactorial logistic-regression analyses to derive odds ratios (OR). Odds for local population disappearance were significantly related to 4 factors in the multifactorial model. Disappearance of frog populations increased with increasing elevation (OR = 2.7 for every 500 m, p < 0.01). Sites where disappearances occurred were 4.3 times more likely to have other nearby sites that also experienced disappearances (OR = 4.3, p < 0.01), whereas the odds of disappearance were 6.7 times less (OR = 0.15, p < 0.01) when there was a source population nearby. Sites with disappearances were 2.6 times more likely to have introduced crayfish than were control sites (OR = 2.6, p = 0.04). The identification of factors associated with frog disappearances increases understanding of declines occurring in natural populations and aids in conservation efforts to reestablish and protect native ranids by identifying and prioritizing implicated threats. 相似文献