全文获取类型
收费全文 | 3308篇 |
免费 | 30篇 |
国内免费 | 171篇 |
专业分类
安全科学 | 96篇 |
废物处理 | 195篇 |
环保管理 | 289篇 |
综合类 | 590篇 |
基础理论 | 775篇 |
环境理论 | 2篇 |
污染及防治 | 1127篇 |
评价与监测 | 239篇 |
社会与环境 | 183篇 |
灾害及防治 | 13篇 |
出版年
2023年 | 17篇 |
2022年 | 69篇 |
2021年 | 39篇 |
2020年 | 24篇 |
2019年 | 37篇 |
2018年 | 116篇 |
2017年 | 51篇 |
2016年 | 76篇 |
2015年 | 84篇 |
2014年 | 89篇 |
2013年 | 265篇 |
2012年 | 88篇 |
2011年 | 158篇 |
2010年 | 138篇 |
2009年 | 150篇 |
2008年 | 160篇 |
2007年 | 187篇 |
2006年 | 140篇 |
2005年 | 117篇 |
2004年 | 143篇 |
2003年 | 138篇 |
2002年 | 114篇 |
2001年 | 239篇 |
2000年 | 143篇 |
1999年 | 71篇 |
1998年 | 41篇 |
1997年 | 47篇 |
1996年 | 33篇 |
1995年 | 40篇 |
1994年 | 42篇 |
1993年 | 41篇 |
1992年 | 30篇 |
1991年 | 35篇 |
1990年 | 27篇 |
1989年 | 32篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 18篇 |
1983年 | 22篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1975年 | 12篇 |
1973年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有3509条查询结果,搜索用时 265 毫秒
691.
Sediments collected from Tap Mun (within Tolo Harbour) and Yim Tin Tsai (outside Tolo Harbour) were extracted sequentially
and the copper, cadmium, and chromium contents were determined. Total contents of copper, cadmium, chromium, and arsenic were
also detected by acid digestion. The level of heavy metal extracted was higher in sequential extraction (which extracted all
forms of metal ions) than total acid digestion. Among the four heavy metals studied, only copper showed a significantly higher
(P<0.001) level in samples collected from Yim Tin Tsai (16.10 mg/kg) than that from Tap Mun (3.19 mg/kg). Such a difference
in copper level is mainly attributed to the significantly higher (P<0.05) levels of copper in the organic, carbonate, and sulfide forms, whereas there was no significant difference (P>0.05) in the exchangeable and sorbed forms.
Green-lipped mussel (Perna viridis) samples collected from the two sites were dissected into seven parts (gill, byssus, siphon, shell, digestive gland, soft
tissue, and adductor muscle) and the concentrations of copper, cadmium, chromium, and arsenic were measured. The highest concentration
of copper was obtained in the byssus. A higher concentration of copper was also noted in the mussels collected from Yim Tin
Tsai than those collected from Tap Mun. No specific trend was revealed for the other metals tested. Chromium and arsenic concentrations
were found to be independent of the body size of the mussels. Copper had a lower concentration in larger mussels and cadmium
level was found to decrease with size. In addition, the mussels collected from Tap Mun were much larger than those collected
from Yim Tin Tsai. 相似文献
692.
Yacov Y Haimes James H. Lambert Duan Li 《Journal of the American Water Resources Association》1992,28(1):201-209
ABSTRACT: This paper summarizes advances made in risk-based decisionmaking in water resources through use of the partitioned multiobjective risk method (PMRM). (Risk is a measure of the probability and severity of adverse effects.) In the PMRM, the risk of extreme events is differentiated from risk involving less extreme damage severity and is evaluated within a multiobjective framework. Study of the extreme-event risk function f4(*) has addressed the following issues: methods for calculating f4(*); the sensitivity of f4(*) to various parameters, particularly to the partitioning point of the extreme-event range and the selection of probability density functions; insight provided by the statistics of extremes; and the impact of f4(*) on risk management, for example, in the application of the PMRM to water resources problems. In particular, this paper shares with the reader recent research results on the PMRM, the relationship between the statistics of extremes and the conditional expected value, derived formulas for f4(*), distribution-free estimates of f4(*), documented case studies in dam safety, and future research directions. 相似文献
693.
Susanna T. Y. Tong 《Environmental management》1990,14(1):107-113
Roadside dusts and soils were collected from various nonindustrial districts in Cincinnati, Ohio, USA, and analyzed for lead
and copper contents. Results showed that the recent lead phase-down action has reduced the level of lead, but the concentrations
of both metals are still higher than the background levels for normal soil. Elevated concentrations of copper in heavily traveled
highways were noted, suggesting that much of the copper pollutants is probably of automotive origin. The concentration of
lead was found to vary with housing age, and higher levels of contamination in the older neighborhoods were observed. This
result is probably ascribable to the accumulation of residues from leaded gasoline and lead-based paint in the past and the
use of coal fire for space heating in older houses. 相似文献
694.
695.
696.
697.
698.
699.
1 Introduction1-1 DiatomsDiatoms(ClassBacillariophyceae)arecommonandwidelydistributedinbothfreshandmarinewaters(Moser,1996).ThesemicroscopicunicellularplantsfixamajorportionoftheEarth○scarbon,generateoxygen,andsupplyfoodtoanimalswhichfeedonthem(Dixit… 相似文献
700.
Between August 1989 and December 1991, 356 patients underwent first-trimester transvaginal amniocentesis (10–12 weeks). The same number of patients referred in the same period for mid-trimester amniocentesis (14–21 weeks) was matched also for maternal age and indication. A third group consisted of the first 356 cases in which chorionic villus sampling (CVS) was attempted. The overall success rate was 99·7 and 100 per cent for early and mid-trimester amniocentesis, respectively, and 97·2 per cent for CVS. The mean harvesting time was 12·8, 11, and 7·9 days, respectively. The percentage of patients rescheduled was 3·4 per cent in first-trimester amniocentesis, 1·7 per cent in mid-trimester amniocentesis, and 6·2 per cent in the CVS group. The early (less than 2 weeks) pregnancy loss was 1·7 and 0·6 per cent in early and mid-trimester amniocentesis, respectively, and 1·7 per cent in CVS. The total pregnancy loss was 3·2, 0·9, and 2·9 per cent, respectively. The rate of preterm birth was 6·0, 5·2 and 6·9 per cent, respectively. The results indicate that CVS has the shortest procedure-result interval, but the highest rescheduling rate. First-trimester amniocentesis has a higher procedure and laboratory success rate but, until otherwise proved, mid-trimester amniocentesis is the most efficient and safest procedure. 相似文献