全文获取类型
收费全文 | 8897篇 |
免费 | 58篇 |
国内免费 | 39篇 |
专业分类
安全科学 | 197篇 |
废物处理 | 518篇 |
环保管理 | 688篇 |
综合类 | 1201篇 |
基础理论 | 2056篇 |
环境理论 | 7篇 |
污染及防治 | 2634篇 |
评价与监测 | 714篇 |
社会与环境 | 942篇 |
灾害及防治 | 37篇 |
出版年
2023年 | 85篇 |
2022年 | 168篇 |
2021年 | 202篇 |
2020年 | 86篇 |
2019年 | 101篇 |
2018年 | 206篇 |
2017年 | 220篇 |
2016年 | 306篇 |
2015年 | 171篇 |
2014年 | 348篇 |
2013年 | 741篇 |
2012年 | 406篇 |
2011年 | 495篇 |
2010年 | 408篇 |
2009年 | 345篇 |
2008年 | 446篇 |
2007年 | 462篇 |
2006年 | 400篇 |
2005年 | 332篇 |
2004年 | 289篇 |
2003年 | 290篇 |
2002年 | 254篇 |
2001年 | 292篇 |
2000年 | 188篇 |
1999年 | 124篇 |
1998年 | 53篇 |
1997年 | 67篇 |
1996年 | 63篇 |
1995年 | 75篇 |
1994年 | 73篇 |
1993年 | 64篇 |
1992年 | 62篇 |
1991年 | 65篇 |
1990年 | 70篇 |
1989年 | 53篇 |
1988年 | 57篇 |
1987年 | 55篇 |
1986年 | 55篇 |
1985年 | 45篇 |
1984年 | 47篇 |
1983年 | 47篇 |
1982年 | 50篇 |
1980年 | 32篇 |
1979年 | 32篇 |
1978年 | 31篇 |
1976年 | 28篇 |
1974年 | 31篇 |
1973年 | 30篇 |
1964年 | 28篇 |
1958年 | 39篇 |
排序方式: 共有8994条查询结果,搜索用时 15 毫秒
431.
To restore food security to a traditional African cropping system following a sudden loss of seed, genetic diversity must be re-established. This study examines the extent to which Cowpea diversity was reinstated two years after a flood disaster in Gaza Province, Mozambique. The contribution that seed from various sources made to the recovery was assessed using semi-structured interviews and morphological and molecular data. Data suggest that diversity had recovered to some extent yet there was evidence of a narrowing of the genetic base, with fewer rare alleles and differences in the distribution of allele frequencies. Although the main channels for accessing seed after the flood were seed relief and markets, these sources contributed to minimal and different diversity. It appears that diversity was regained primarily through social networking in the form of loans or gifts of seed from friends and relatives. The results of the study are discussed in relation to seed relief approaches. 相似文献
432.
G. N. Tikhonova I. A. Tikhonov E. V. Kotenkova A. I. Munteanu I. G. Uspenskaya Yu. N. Konovalov V. I. Burlaku V. F. Kiku S. D. Georgitsa N. K. Karaman V. B. Nistreanu A. N. Mal’tsev 《Russian Journal of Ecology》2012,43(3):236-242
Comparative analysis of the structure of small mammal communities has been performed in two European cities located in different biomes: Chisinau (2008?C2009) and Yaroslavl (1994?C2002). The parameters studied included abundance, species composition, similarity and difference of faunas, species diversity, and proportions of groups differing in predisposition to synanthropy. It has been found that the structure of small mammal communities in these cities depends on specific physiographic conditions of the surrounding areas and on the distinctive features of the cities themselves (their structure, age, etc.). The similarity between the faunas is accounted for by the common ecological patterns of fauna formation in the biota of urban cenoses. 相似文献
433.
M. A. Potapov I. V. Zadubrovskaya P. A. Zadubrovskii O. F. Potapova V. I. Evsikov 《Russian Journal of Ecology》2012,43(1):40-44
A comparative analysis of reproductive behavior has been performed in the steppe lemming (Lagurus lagurus) and narrow-skulled vole (Microtus gregalis). The results show that the species are similar in certain behavioral features indicative of the stability of mating pairs.
However, in the narrow-skulled vole, unlike in the steppe lemming, mature males in olfactory tests show preference for receptive
sibling females versus non-kin females. Probably, it is the absence of the incest taboo that allows the involvement of young
of the year in reproduction within growing family groups and accounts for “coloniality” of the species. 相似文献
434.
The results are presented that have been obtained during long-term studies (1991–2009) on the efficiency of natural reproduction
of the beluga, Russian sturgeon, stellate sturgeon, and sterlet in different spawning zones of the Volga. The influence of
major environmental factors on the formation of the offspring of these fishes is analyzed. It is shown that the productivity
of Volga spawning grounds varies depending on the river flow volume during spring floods and the abundance of active spawners.
Practical recommendations are proposed for enhancing sturgeon reproduction in the Volga. 相似文献
435.
The levels of total lipids, peroxidation products, and antioxidant activity in the liver were studied in fish species living in unequally polluted areas of the Rybinsk Reservoir and differing in their ecology and taxonomic position: the bream (Abramis brama L.), roach (Rutilus rutilus L.), burbot (Lota lota L.), and zander (Stizostedion lucioperca L.). The fish from polluted water areas were characterized by higher levels of total lipids and malonic dialdehyde and a deficiency of antioxidants. It is shown that the test parameters depend on the type of feeding and mode of life of the fish species. 相似文献
436.
J. B. Koogler R. S. Sholtes A. L. Danis C. I. Harding 《Journal of the Air & Waste Management Association (1995)》2013,63(4):211-214
In conjunction with a 15-month air quality survey of Jacksonville, Fia., a mathematical model has been developed to describe the dispersion of atmospheric pollutants. The source inventory used with the model was compiled, in part, from the data obtained from the sampling of all major sources within the area. The major sources were considered separately from the one-mile square area sources which accounted for the remainder of the emissions. Meteorological data was recorded continuously in the city including vertical temperature observations to 750 ft. The model was compiled in FORTRAN and can be used for both gaseous and particulate pollutants, by utilizing proper decay rates. The variant nature of meteorological parameters and emission rates are considered. The ground level concentrations of several pollutants which were determined for 24 hr periods at 11 sites and continuously at two other sites were used to check the model. A limited tracer study was carried out in conjunction with the project. 相似文献
437.
Walter W. Heck John A. Dunning I. J. Hindawi 《Journal of the Air & Waste Management Association (1995)》2013,63(11):511-515
Before potential damage to vegetation can be adequately forecast, even after an air pollution alert has been placed in effect, a clear understanding of the interactions of environment on plant sensitivity must be ascertained. This involves detailed study of single factors and then multiple factors using the phytotoxicants in question. Factors studied or suggested include light (quality, intensity, and duration), temperature, carbon dioxide concentration, humidity, wind, soil moisture, soil aeration, nutrient levels, and soil texture. This paper presents a review of the work relating plant injury to specific air pollutants as conditioned by several environmental conditions supported by research on the interactions of ozone with these environmental conditions. 相似文献
438.
S. F. Galeano C.I. Harding 《Journal of the Air & Waste Management Association (1995)》2013,63(8):536-539
The use of soda ash liquor to scrub SO2 rich power plant flue gases was studied using an Airetron pilot scrubber with a maximum capacity of 3000 cfm. The relative effects of the major operating variables— temperature, soda ash concentration, and the gas/liquid flow ratio—on the absorption phenomenon were determined. Orthogonal factorial experiments were used to derive a response function relating mass transfer values to operating variables. The economics of a full scale NSSC installation are discussed. 相似文献
439.
S. I. Schwartz 《Journal of the Air & Waste Management Association (1995)》2013,63(10):845-852
A comprehensive analysis of inspection maintenance programs is proposed. Effectiveness, costs to the state and to the individual, distribution of cost and benefits, and political and administrative feasibility are examined. Effectiveness is probably the most difficult aspect to project because of changes in design and consequences of maintenance repair on performance. However, using sensitivity analysis, substantial reductions in hydrocarbons and carbon monoxide are foreseen, along with a slight increase in NOx emissions. The cost to the state to administer the program is estimated to be between $2.00 and $2.50 per vehicle, which could be covered by the inspection fee. The other direct costs for the driver, lost time, travel, and repairs, may be offset by fuel and tuneup savings which could amount to as much as 50% of the repair bill. Analysis of distribution costs and indirect social consequences cannot be completed until additional information about the effect of income on maintenance is generated. Politically the program is feasible but depends on public support which in turn is sensitive to direct repair costs. Administratively the program suffers greatly if private repair facilities do not have enough adequately trained mechanics. It is concluded that the benefits of an inspection program do not convincingly outweigh the high costs, possible adverse social impacts, and public opposition and that other alternatives should be examined. 相似文献
440.