全文获取类型
收费全文 | 1372篇 |
免费 | 36篇 |
国内免费 | 89篇 |
专业分类
安全科学 | 52篇 |
废物处理 | 22篇 |
环保管理 | 66篇 |
综合类 | 958篇 |
基础理论 | 162篇 |
污染及防治 | 51篇 |
评价与监测 | 160篇 |
社会与环境 | 16篇 |
灾害及防治 | 10篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 16篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 18篇 |
2014年 | 36篇 |
2013年 | 59篇 |
2012年 | 49篇 |
2011年 | 122篇 |
2010年 | 98篇 |
2009年 | 83篇 |
2008年 | 66篇 |
2007年 | 111篇 |
2006年 | 90篇 |
2005年 | 85篇 |
2004年 | 90篇 |
2003年 | 83篇 |
2002年 | 80篇 |
2001年 | 57篇 |
2000年 | 40篇 |
1999年 | 25篇 |
1998年 | 22篇 |
1997年 | 31篇 |
1996年 | 33篇 |
1995年 | 49篇 |
1994年 | 43篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 1篇 |
排序方式: 共有1497条查询结果,搜索用时 281 毫秒
701.
火焰原子吸收分光光度法测定废水中总铬 总被引:5,自引:0,他引:5
研究环境样品中总铬用火焰原子吸收分光光度法测定。选择不同实验条件 ,确定了最佳的分析条件 ,并通过标准样品和实验样品的分析 ,验证了方法的准确度和精密度。实验证明 ,此方法快速方便、准确度高、精密度好。 相似文献
702.
通过对紫外法测定水中总氮影响准确度因素的分析得出前处理、工作曲线的绘制、样品的重复性测定及标准物质的配制是影响准确度的主要因素,可通过采取提高操作人员的业务技术水平、多次绘制工作曲线、适当增加样品重复次数等方法来提高测量准确性。 相似文献
703.
704.
705.
Fetuses of women with alloantibodies to RhD (D) are at risk from hemolytic disease of the fetus and newborn, but only if the fetal red cells are D-positive. In such pregnancies, it is beneficial to determine fetal D type, as this will affect the management of the pregnancy. It is possible to predict, with a high level of accuracy, fetal blood group phenotypes from genotyping tests on fetal DNA. The best source is the small quantity of fetal DNA in the blood of pregnant women, as this avoids the requirement for invasive procedures of amniocentesis or chorionic villus sampling (CVS). Many laboratories worldwide now provide noninvasive fetal D genotyping as a routine service for alloimmunized women, and some also test for c, E, C and K. In many countries, anti-D immunoglobulin injections are offered to D-negative pregnant women, to reduce the chances of prenatal immunization, even though up to 40% of these women will have a D-negative fetus. High-throughput, noninvasive fetal D genotyping technologies are being developed so that unnecessary treatment of pregnant women can be avoided. Trials suggest that fetal D typing of all D-negative pregnant women is feasible and should become common practice in the near future. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
706.
707.
708.
The discovery of cell-free fetal (cff) DNA and RNA in the maternal circulation has driven developments in noninvasive prenatal diagnosis (NIPD) for the past decade. Detection of paternally derived alleles in cff DNA is becoming well established. Now much interest is focussing on NIPD of fetal chromosomal abnormalities, such as trisomy 21, which is a considerable challenge because this demands accurate quantitative measurements of the amounts of specific cff DNA or cff RNA sequences in maternal blood samples. Emerging strategies for distinguishing and quantifying the fetal nucleic acids in the maternal circulation promise continued development of the field, and pose a number of unanswered questions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
709.
710.
GRAEME C. HAYS SABRINA FOSSETTE KOSTAS A. KATSELIDIS GAIL SCHOFIELD MIKE B. GRAVENOR 《Conservation biology》2010,24(6):1636-1643
Abstract: Species that have temperature‐dependent sex determination (TSD) often produce highly skewed offspring sex ratios contrary to long‐standing theoretical predictions. This ecological enigma has provoked concern that climate change may induce the production of single‐sex generations and hence lead to population extirpation. All species of sea turtles exhibit TSD, many are already endangered, and most already produce sex ratios skewed to the sex produced at warmer temperatures (females). We tracked male loggerhead turtles (Caretta caretta) from Zakynthos, Greece, throughout the entire interval between successive breeding seasons and identified individuals on their breeding grounds, using photoidentification, to determine breeding periodicity and operational sex ratios. Males returned to breed at least twice as frequently as females. We estimated that the hatchling sex ratio of 70:30 female to male for this rookery will translate into an overall operational sex ratio (OSR) (i.e., ratio of total number of males vs females breeding each year) of close to 50:50 female to male. We followed three male turtles for between 10 and 12 months during which time they all traveled back to the breeding grounds. Flipper tagging revealed the proportion of females returning to nest after intervals of 1, 2, 3, and 4 years were 0.21, 0.38, 0.29, and 0.12, respectively (mean interval 2.3 years). A further nine male turtles were tracked for short periods to determine their departure date from the breeding grounds. These departure dates were combined with a photoidentification data set of 165 individuals identified on in‐water transect surveys at the start of the breeding season to develop a statistical model of the population dynamics. This model produced a maximum likelihood estimate that males visit the breeding site 2.6 times more often than females (95%CI 2.1, 3.1), which was consistent with the data from satellite tracking and flipper tagging. Increased frequency of male breeding will help ameliorate female‐biased hatchling sex ratios. Combined with the ability of males to fertilize the eggs of many females and for females to store sperm to fertilize many clutches, our results imply that effects of climate change on the viability of sea turtle populations are likely to be less acute than previously suspected. 相似文献