全文获取类型
收费全文 | 17479篇 |
免费 | 285篇 |
国内免费 | 321篇 |
专业分类
安全科学 | 613篇 |
废物处理 | 740篇 |
环保管理 | 2617篇 |
综合类 | 2919篇 |
基础理论 | 4490篇 |
环境理论 | 7篇 |
污染及防治 | 4561篇 |
评价与监测 | 996篇 |
社会与环境 | 1017篇 |
灾害及防治 | 125篇 |
出版年
2022年 | 160篇 |
2021年 | 163篇 |
2020年 | 181篇 |
2019年 | 144篇 |
2018年 | 283篇 |
2017年 | 258篇 |
2016年 | 400篇 |
2015年 | 319篇 |
2014年 | 448篇 |
2013年 | 1417篇 |
2012年 | 605篇 |
2011年 | 885篇 |
2010年 | 665篇 |
2009年 | 762篇 |
2008年 | 827篇 |
2007年 | 869篇 |
2006年 | 720篇 |
2005年 | 605篇 |
2004年 | 622篇 |
2003年 | 563篇 |
2002年 | 537篇 |
2001年 | 645篇 |
2000年 | 520篇 |
1999年 | 315篇 |
1998年 | 210篇 |
1997年 | 228篇 |
1996年 | 221篇 |
1995年 | 268篇 |
1994年 | 209篇 |
1993年 | 209篇 |
1992年 | 176篇 |
1991年 | 182篇 |
1990年 | 178篇 |
1989年 | 183篇 |
1988年 | 153篇 |
1987年 | 133篇 |
1986年 | 156篇 |
1985年 | 143篇 |
1984年 | 191篇 |
1983年 | 147篇 |
1982年 | 171篇 |
1981年 | 157篇 |
1980年 | 130篇 |
1979年 | 149篇 |
1978年 | 94篇 |
1977年 | 98篇 |
1975年 | 88篇 |
1974年 | 94篇 |
1973年 | 86篇 |
1972年 | 96篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
311.
Prenatal diagnosis in a pregnancy at risk for a juvenile B1 variant of GM2-gangliosidosis was carried out. The biochemical study of the cultured amniocytes and the affected fetal brain is reported. The results obtained show that the sulphated artificial substrate can be used in the diagnosis of B1 variant, but not the neutral one. The accumulation of GM2-ganglioside in the fetal brain of the B1 juvenile form and an infantile form of GM2-gangliosidosis (0 variant) was compared. 相似文献
312.
313.
314.
315.
316.
以某矿的一、二采区为例,介绍了评价开采沉陷对矿区生态环境影响的基本方法和过程.重点以土地作为评价因素,据地表沉陷预测结果和评价指标体系,对塌陷区内的土地损害形式进行了总结,对塌陷引起的土地损害这一环境因素的影响进行了评价,获得了塌陷区的影响程度和区域. 相似文献
317.
Sequential extraction analysis of heavy metals using a chelating agent (NTA) to counteract resorption 总被引:3,自引:0,他引:3
The geochemical partitioning of Pb, Ni and Zn in contaminated quartz-rich sediment and soil samples was characterized by sequential extraction analysis in the presence and absence of nitrilotriacetic acid (NTA). With NTA, levels of metals recovered are higher in the earlier steps and lower in the later steps of the procedure. This suggests that post-extraction resorption is effectively counteracted by chelation, thereby improving the accuracy of the method. An NTA concentration of 200 mg liter(-1) appears to be sufficient for counteracting resorption without causing significant dissolution of non-targeted phases in the samples studied. However, experiments using reference materials spiked with solutions containing Pb, Ni, Cu and Zn suggest that resorption will remain a problem when large amounts of strong sorbents such as organic matter are present. The results also show that although post-extraction resorption does occur in the absence of NTA, the magnitude of resorption is small (<20 to 30% of the summed total of metal present in the sample) in quartz-rich sediments. 相似文献
318.
Johnstone RM Court GS Fesser AC Bradley DM Oliphant LW MacNeil JD 《Environmental pollution (Barking, Essex : 1987)》1996,93(2):109-120
Levels of eggshell thinning, and organochlorine residues in egg contents, blood plasma of adults and juveniles, tissue samples, and prey species were determined for a population of migratory Peregrine Falcons (Falco peregrinus tundrius) breeding in the Canadian Arctic. Temporal trends were assessed by comparing data collected during 1991-1994, with data from 1982-1986, for the same population. Shells (n=54) from 1991-1994 averaged 15% thinner than eggs produced prior to the introduction of DDT. No improvement in shell thickness was detected between decades. Mean DDE residue levels in eggs showed a decline from 7.6 mg kg (1982-1986) to 4.5 mg kg (1991-1994), but there was no significant change in SigmaPCB residues. Moreover, the proportion of clutches with eggs exceeding critical SigmaPCB, DDE, and dieldrin residue levels (10%) did not change between decades. Relative to Greenland and Alaskan populations, F. p. tundrius at Rankin Inlet show high levels of organochlorine contamination and little reduction in residues over the last decade. These Tundra Peregrines continue to be exposed to organochlorines in Latin America; however, results also link relatively high levels in the study population with waterfowl species that do not leave Canada in winter. 相似文献
319.
France RL 《Environmental pollution (Barking, Essex : 1987)》1996,94(2):189-193
Population biomass and production of the amphipod Hyalella azteca (Saussure) were found to be related to alkalinity (ranging from 0.2 to 58.1 mg liter(-1)) in 10 Canadian Shield lakes in south-central Ontario. Biomass and production of amphipods in the two lakes characterized by spring depressions of pH below 5.0 were found to be lower than those for populations inhabiting lakes that did not experience such acid pulses. The proportional biomass of amphipods in relation to the total littoral zoobenthos community was lower in lakes of low alkalinity than in circumneutral or hardwater lakes. Because production in these amphipod populations is known to depend closely on population abundance, the labour-intensive derivation of production rates yields relatively little information for biomonitoring that cannot be obtained from abundance data alone. 相似文献
320.
Nast W Mortensen L Fischer K Fitting I 《Environmental pollution (Barking, Essex : 1987)》1993,80(1):85-90
Grafted Norway spruce trees were subjected to exposure beginning in April 1988, to one of four different air treatments in open-top chambers: Charcoal filtered air (CF), non-filtered air (NF), non-filtered air with the addition of O(3) during summer (NFO), and SO(2) plus NO(2) during winter (NFOSN). CF trees were considered as the reference group. No effects on growth parameters were observed. Samples of the two youngest needle year classes were taken late in November 1989 for enzyme determinations. The activity of ascorbic acid peroxidase (A-POD) increased the same level in all treatments, and activities of catalase and dehydroascorbic acid reductase (DHA-R) increased only in NF and NFO treatments. A higher level of activity in the NFOSN treatment was observed only for glucose-6-phosphate-dehydrogenase (Glc-6-P-DH) and non-specific peroxidase (POD). Isoelectric focusing of POD showed a changed pattern in the NFOSN treatment. Neither activity nor isoelectric focusing of superoxidase dismutase (SOD) was changed in any of the treatments. 相似文献