全文获取类型
收费全文 | 4318篇 |
免费 | 68篇 |
国内免费 | 242篇 |
专业分类
安全科学 | 205篇 |
废物处理 | 207篇 |
环保管理 | 433篇 |
综合类 | 875篇 |
基础理论 | 325篇 |
污染及防治 | 1841篇 |
评价与监测 | 451篇 |
社会与环境 | 248篇 |
灾害及防治 | 43篇 |
出版年
2024年 | 11篇 |
2023年 | 28篇 |
2022年 | 37篇 |
2021年 | 39篇 |
2020年 | 34篇 |
2019年 | 38篇 |
2018年 | 41篇 |
2017年 | 34篇 |
2016年 | 29篇 |
2015年 | 31篇 |
2014年 | 58篇 |
2013年 | 22篇 |
2012年 | 388篇 |
2011年 | 499篇 |
2010年 | 87篇 |
2009年 | 116篇 |
2008年 | 439篇 |
2007年 | 468篇 |
2006年 | 405篇 |
2005年 | 307篇 |
2004年 | 280篇 |
2003年 | 247篇 |
2002年 | 239篇 |
2001年 | 135篇 |
2000年 | 115篇 |
1999年 | 63篇 |
1998年 | 21篇 |
1997年 | 41篇 |
1996年 | 33篇 |
1995年 | 25篇 |
1994年 | 37篇 |
1993年 | 32篇 |
1992年 | 24篇 |
1991年 | 26篇 |
1990年 | 32篇 |
1989年 | 25篇 |
1988年 | 26篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 21篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有4628条查询结果,搜索用时 15 毫秒
41.
Circling and linear flights of a hairstreak Chrysozephyrus smaragdinus were recorded in natural habitat with a high-speed video camera. Circling flight paths were resolved into rotation and shift
components; values on X- and Y-coordinates of the butterfly position were separately extracted against time and fitted with a regression line composed of
a sinusoidal curve and a linear line. From the obtained parameters, diameter, rotation number, and flight velocity were calculated.
Flapping movements were also analyzed. Two types of circling flights, horizontal and vertical, were discriminated. In both
flights, the rotation diameter was about 10 cm, rotation number of 3/s, flight velocity of 0.9 m/s, and wing-beat frequency
of 20/s. The coordination of paired butterflies in circling flight showed a higher correlation in the horizontal circling
flight. In the vertical circling flight, butterflies accelerated the downstroke speed of the wing in the ascending phase.
They flew about four times faster in linear flights than in circling flights due to the higher frequency of wing beats. 相似文献
42.
43.
44.
Yoshida S Muramatsu Y Yamazaki S Ban-Nai T 《Journal of environmental radioactivity》2007,96(1-3):85-93
Plutonium isotopes in forest soils collected in Nishiyama area, Nagasaki, were successfully determined by high resolution inductively coupled plasma mass spectrometry after the treatment with a microwave decomposition system. The (240)Pu/(239)Pu atom ratios observed in the samples in the Nishiyama area were obviously lower than the range of the global fallout. The low ratios (minimum 0.032) observed in Nishiyama area indicated the influence of detonation of the Pu nuclear weapon in 1945. Since the area is contaminated also by global fallout, the (240)Pu/(239)Pu atom ratio can be more sensitive indicator of bomb-derived Pu than Pu activity concentration. 相似文献
45.
Ishii N Sakashita T Takeda H Kubota Y Fuma S Doi M Takahashi S 《Journal of environmental radioactivity》2007,97(2-3):159-167
Extracellular DNA is omnipresent in aquatic environments and is thought to be a genetic material for horizontal gene transformation between microorganisms. We studied the impact of gamma irradiation on the transformation efficiency (transformants number per ng of DNA per ml) of extracellular DNA. Plasmid pEGFP as a model extracellular DNA was irradiated by gamma rays. The transformation efficiency decreased with the increase in radiation dose. A total dose of 10Gy is normally not lethal for microorganisms but certainly affects the transformation efficiency of extracellular DNA. The decrease in the efficiency would be induced by strand breaks of extracellular DNA because the yield of both single-strand breaks (SSBs) and double-strand breaks (DSBs) increased with the increase in radiation dose. The relative transformation efficiency of SSBs and DSBs to that of covalently closed circles (CCCs) was 30.3% and 0.2%, respectively. This impact on natural transformation suggests an inability of microorganisms to acquire new characteristics which should be normally acquired. 相似文献
46.
Lauritzen B Baklanov A Mahura A Mikkelsen T Sørensen JH 《Journal of environmental radioactivity》2007,96(1-3):110-115
A simplified means of probabilistic risk assessment (PRA) for long-range atmospheric transport based on a K-diffusion model is presented. In a case study, model parameters are estimated by comparing with the results of long-range atmospheric dispersion model calculations using one-year numerical weather prediction model data. It is found that the estimated ensemble mean provides a reasonable first approximation to the total dry and wet deposition from the one-year continuous release. 相似文献
47.
伴随着21世纪的到来,国民经济的不断发展刺激了社会对石油能源的需求,世界石油炼化企业的发展迎来了新的机遇。但是机遇是把双刃剑,同时也带来了一系列的问题,使石油炼化企业在环保问题上面临了新的挑战。本文概括了石油炼化企业在环保上所遇到的挑战,并针对这些的挑战、问题,提出了一系列的对策,使人们更加清楚的认识到石头炼化企业在快速发展的同时,也要高度注重环保问题。 相似文献
48.
项目综合报告编写组何建坤解振华李政张希良 《中国人口.资源与环境》2020,(11):1-25
前言2020年是一个特殊的年份,在这一年中,新冠肺炎疫情肆虐,席卷全球,造成上千万人感染,夺去了上百万人的生命,对各国的公共卫生系统、公众健康、经济活动和居民生活造成了严重冲击,也深刻影响了并将重塑世界政治经济贸易格局。 相似文献
49.
Luo J Shukla R Adhikari A Reponen T Grinshpun SA Zhang Q LeMasters GK 《Journal of environmental monitoring : JEM》2006,8(9):955-962
A time series model was fitted to the pollen concentration data collected in the Greater Cincinnati area for the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS). A traditional time series analysis and temporal variogram approach were applied to the regularly spaced databases (collected in 2003) and irregularly spaced ones (collected in 2002), respectively. The aim was to evaluate the effect of the sampling frequency on the sampling precision in terms of inverse of standard error of the overall level of mean value across time. The presence of high autocorrelation in the data was confirmed and indicated some degree of temporal redundancy in the pollen concentration data. Therefore, it was suggested that sampling frequency could be reduced from once a day to once every several days without a major loss of sampling precision of the overall mean over time. Considering the trade-offs between sampling frequency and the possibility of sampling bias increasing with larger sampling interval, we recommend that the sampling interval should take values from 3 to 5 days for the pollen monitoring program, if the goal is to track the long-term average. 相似文献
50.