全文获取类型
收费全文 | 3119篇 |
免费 | 6篇 |
国内免费 | 42篇 |
专业分类
安全科学 | 45篇 |
废物处理 | 122篇 |
环保管理 | 337篇 |
综合类 | 404篇 |
基础理论 | 1427篇 |
环境理论 | 1篇 |
污染及防治 | 491篇 |
评价与监测 | 149篇 |
社会与环境 | 185篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 13篇 |
2022年 | 45篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 95篇 |
2017年 | 66篇 |
2016年 | 114篇 |
2015年 | 64篇 |
2014年 | 41篇 |
2013年 | 126篇 |
2012年 | 179篇 |
2011年 | 116篇 |
2010年 | 71篇 |
2009年 | 77篇 |
2008年 | 75篇 |
2007年 | 65篇 |
2006年 | 61篇 |
2005年 | 409篇 |
2004年 | 570篇 |
2003年 | 451篇 |
2002年 | 53篇 |
2001年 | 104篇 |
2000年 | 43篇 |
1999年 | 24篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 20篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1980年 | 6篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 7篇 |
1972年 | 12篇 |
1971年 | 5篇 |
1966年 | 5篇 |
1965年 | 5篇 |
1959年 | 5篇 |
1957年 | 5篇 |
排序方式: 共有3167条查询结果,搜索用时 46 毫秒
501.
N.Z. Lupwayi K.N. Harker G.W. Clayton J.T. O’Donovan R.E. Blackshaw 《Agriculture, ecosystems & environment》2009,129(1-3):171-176
Adoption of glyphosate-resistant canola (Brassica napus L.) has increased glyphosate applications to this crop, and concerns have been raised about unintended consequences of these multiple applications. A field trial was conducted to evaluate the effects of pre-seed and in-crop glyphosate and alternative herbicides on soil microbial community functional structure, diversity and biomass. Pre-seed treatments were 2,4-D, glyphosate and 2,4-D + glyphosate, and in-crop treatments were glyphosate applied once, glyphosate applied twice, ethalfluralin, ethalfluralin + sethoxydim + ethametsulfuron + clopyralid, and sethoxydim + ethametsulfuron. Rhizosphere and bulk soil was collected at flowering stage of canola and analyzed for bacterial community-level substrate utilization patterns and microbial biomass C (MBC). Where differences were significant, pre-seed application of both 2,4-D and glyphosate altered the functional structure and reduced the functional diversity of soil bacteria, but increased MBC. These effects were not necessarily concurrent. The reduction in functional diversity was due to reduction in evenness, which means that the soil where both pre-seed herbicides had been applied was dominated by only few functional groups. In 1 year, two in-crop applications of glyphosate also reduced the functional diversity of soil bacteria when applied after pre-seed 2,4-D, as did in-crop sethoxydim + ethametsulfuron following pre-seed glyphosate. Even though significant differences between herbicides were fewer than non-significant differences, i.e., there were no changes in soil microbial community structure, diversity or biomass in response to glyphosate or alternative herbicides applied to glyphosate-resistant canola in most cases, the observed changes in soil microbial communities could affect soil food webs and biological processes. 相似文献
502.
Joseph?M.?Kimetu Josephine?M.?Hill Maen?Husein Joule?Bergerson David?B.?LayzellEmail author 《Mitigation and Adaptation Strategies for Global Change》2016,21(5):761-777
This study explored the feasibility of using residual biomass to both mitigate greenhouse gas (GHG) emissions and remediate water contaminated by hydrocarbons. Using produced (process-affected) water from Canada’s oil sands operations as a case study, activated biochar (ACB) was found to have a higher affinity to organics than activated coal and removed 75 % of total organic carbon (TOC) from produced water in steam-assisted gravity drainage (SAGD) operations or 90 % of the TOC from synthetic tailings (ST) water sample. Up to 6 Tg dry biomass year?1 would be required to treat the waters associated with the 93?×?106-m3 of bitumen recovered per year. Landfilling the spent ACB and flaring any biogas produced were estimated to provide a greater GHG benefit than the combustion of the biochar + organics for heat to offset natural gas demand. Net costs for the ACB were about 13.84?$?m?3 bitumen for SAGD operations and 1.76?$?m?3 bitumen for mining operations. The values for mining operations justify further work to create a value chain that will integrate bioprocesses into the fossil fuel industry. 相似文献
503.
504.
Govindasamy?BalaEmail author Ranjith?Gopalakrishnan Mathangi?Jayaraman Ramakrishna?Nemani N.?H.?Ravindranath 《Mitigation and Adaptation Strategies for Global Change》2011,16(2):143-160
There is huge knowledge gap in our understanding of many terrestrial carbon cycle processes. In this paper, we investigate
the bounds on terrestrial carbon uptake over India that arises solely due to CO
2
-fertilization. For this purpose, we use a terrestrial carbon cycle model and consider two extreme scenarios: unlimited CO2-fertilization is allowed for the terrestrial vegetation with CO2 concentration level at 735 ppm in one case, and CO2-fertilization is capped at year 1975 levels for another simulation. Our simulations show that, under equilibrium conditions,
modeled carbon stocks in natural potential vegetation increase by 17 Gt-C with unlimited fertilization for CO2 levels and climate change corresponding to the end of 21st century but they decline by 5.5 Gt-C if fertilization is limited
at 1975 levels of CO2 concentration. The carbon stock changes are dominated by forests. The area covered by natural potential forests increases
by about 36% in the unlimited fertilization case but decreases by 15% in the fertilization-capped case. Thus, the assumption
regarding CO2-fertilization has the potential to alter the sign of terrestrial carbon uptake over India. Our model simulations also imply
that the maximum potential terrestrial sequestration over India, under equilibrium conditions and best case scenario of unlimited
CO2-fertilization, is only 18% of the 21st century SRES A2 scenarios emissions from India. The limited uptake potential of the
natural potential vegetation suggests that reduction of CO2 emissions and afforestation programs should be top priorities. 相似文献
505.
The agricultural non-point source pollution by nitrogen (N) and phosphorus (P) loss from typical paddy soil (whitish soil, Bai Tu in Chinese) in the Taihu Lake region was investigated through a case study. Results shown that the net load of nutrients from white soil is 34.1 kg ha(-1) for total nitrogen (TN), distributed as 19.4 kg ha(-1), in the rice season and 14.7 kg ha(-1) in the wheat season, and for total phosphorus (TP) 1.75 kg ha(-1), distributed as 1.16 kg ha(-1) in the rice season and 0.58 kg ha(-1) in the wheat season. The major chemical species of N loss is different in the two seasons. NH4-N is main the form in the rice season (53% of TN). NO3-N is the main form in wheat season (46% of TN). Particle-P is the main form in both seasons, (about 56% of TP). The nutrient loss varied with time of the year. The main loss of nutrients happened in the 10 days after planting, 64% of TN and 42% of TP loss, respectively. Rainfall and fertilizer application are the key factors which influence nitrogen and phosphorus loss from arable land, especially rainfall events shortly after fertilizer application. So it is very important to improve the field management of the nutrients and water during the early days of planting. 相似文献
506.
The Kumamoto oyster Crassostrea sikamea is distinguished from the closely related Pacific oyster C. gigas by concordant differences in 16S rDNA, allozymes, and a one-way gametic incompatibility. After repeated failures to find
this oyster in its native habitat, we speculated in 1994 that “the Kumamoto oyster may be extinct in Japan”. In September
1996, we sampled small, deep-cupped oysters from the Ariake Sea and typed these for 16S rDNA and ITS-1 DNA markers previously
shown to be diagnostic for the three most common oysters in the Ariake Sea, C. gigas, C. sikamea and C. ariakensis. Our earlier suggestion of the demise of C. sikamea proved incorrect. Of the 256 oysters sampled, 181 (71%) were C. gigas, 53 (21%) were C. sikamea, and 22 (9%) were C. ariakensis; no interspecific hybrids were observed. The distributions of C. sikamea and C. ariakensis are clumped in the Ariake Sea: C. sikamea occurs on the eastern and northern shores, C. ariakensis occurs only in the northern part. These results emphasize the value of molecular markers for discriminating these morphologically
plastic species both in the field and in aquaculture.
Received 6 July 1998 / Accepted 8 October 1998 相似文献
507.
The effect of feeding the flagellate Isochrysis galbana (Parke; clone T-Iso) of modified lipid composition on the growth and lipid composition of juvenile scallops [Placopecten magellanicus (Gmelin)] was investigated in the spring of 1993. I. galbana grown in 85-liter cage culture turbidostats under conditions of nitrogen limitation had a significantly higher total lipid
content than when grown under nutrient-replete conditions. This was due mainly to a doubling in the amount of less unsaturated
triacylglycerol in the cells. The concentrations of methyl and ethyl ketones were also greater in nitrogen-limited cells.
Diets of nitrogen-limited I. galbana and nutrient-replete I. galbana grown in continuous and semi-continuous cultures were compared. Scallop juveniles were batch fed daily, and measurements
of ingestion were determined. Samples of juveniles were removed periodically for determination of organic weight. The juveniles
did not grow when fed nitrogen-limited or nutrient-replete I. galbana alone; however, when each diet was supplemented with 20% of the diatom Chaetoceros muelleri (Lemm.), there was a significant increase in growth in the juveniles receiving the nitrogen-limited I. galbana compared with juveniles on other diets. In comparison with I. galbana, C. muelleri provided a rich source of carbohydrates and the essential fatty acid 20:4ω6. This study shows the importance of providing
optimal dietary levels of ω3 and ω6 polyunsaturated fatty acids, as well as less unsaturated fatty acids and carbohydrates.
Received: 29 September 1997 / Accepted: 2 October 1998 相似文献
508.
IntroductionCeramic,consistofearthymaterialslikeclaykaolin ,limestoneandsandglass .Ceramicmaterialsarenonmetalic ,inorganiccompoundsprimaryoxides ,alsocarbides ,nitridesandsilicides .Twotypesofbondingmechanismsoccurinceramicmaterial ,ionicandcovalent.Theo… 相似文献
509.
Paula?Adánez SanjuánEmail author Belinda?Flem Juan?F.?Llamas Borrajo Juan?Locutura Rupérez Angel?Garcia Cortés 《Environmental geochemistry and health》2016,38(2):449-468
Changes in the principal sources of Pb in overbank sediment profiles have been documented for two Spanish areas by using Pb isotopes and Pb concentrations. These locations (Madrid and Tinto–Odiel basin) represent two of the most contaminated regions in Spain. The Community of Madrid is characterized by heavy industrial and urban activity, focused mainly in Madrid City. The Tinto–Odiel basin drains the Iberian Pyrite Belt, which hosts many polymetallic massive sulphides and is heavily affected by mining activities in their headwaters. It has been proven that the influence of anthropogenic activity is reflected in these overbank deposits by variations in Pb concentrations that, in general, correlate with shifts in the 206Pb/207Pb ratio. Rivas profile (downstream of Madrid) was found to be the most anthropogenically influenced site. The sediments within this profile which were recently deposited (170 ± 40 years BP) have the least radiogenic signatures. 206Pb/207Pb ratios ranged between 1.1763 and 1.1876 indicating significant contributions of anthropogenic Pb. In contrast, profiles upstream of Madrid possess an average 206Pb/207Pb ratio of 1.2272. It is difficult to clearly identify the most prominent source as the sediments appear to be characterized by an input from several sources. The floodplain profiles in the Tinto–Odiel basin exhibit uniform 206Pb/207Pb ratios ranging from 1.1627 (Odiel river) to 1.1665 (Tinto river). These ratios are similar to the ones possessed by sulphide ores in the area and differ from the ratios of other nonmineralized formations in the basin, indicating that mining activities are the primary, if not sole, source of Pb to the sediments. 相似文献
510.