全文获取类型
收费全文 | 838篇 |
免费 | 196篇 |
国内免费 | 19篇 |
专业分类
安全科学 | 116篇 |
废物处理 | 10篇 |
环保管理 | 120篇 |
综合类 | 465篇 |
基础理论 | 128篇 |
污染及防治 | 85篇 |
评价与监测 | 76篇 |
社会与环境 | 11篇 |
灾害及防治 | 42篇 |
出版年
2025年 | 4篇 |
2024年 | 12篇 |
2023年 | 14篇 |
2022年 | 15篇 |
2021年 | 32篇 |
2020年 | 20篇 |
2019年 | 22篇 |
2018年 | 35篇 |
2017年 | 37篇 |
2016年 | 43篇 |
2015年 | 52篇 |
2014年 | 41篇 |
2013年 | 55篇 |
2012年 | 59篇 |
2011年 | 62篇 |
2010年 | 47篇 |
2009年 | 56篇 |
2008年 | 38篇 |
2007年 | 61篇 |
2006年 | 70篇 |
2005年 | 52篇 |
2004年 | 38篇 |
2003年 | 29篇 |
2002年 | 27篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1053条查询结果,搜索用时 15 毫秒
211.
对南县供水状况进行了简要的介绍,提出了修建水厂的必要性,然后从技术、运行、运行管理费用等方面对送水泵房选泵方案进行了比较,确定了最优方案. 相似文献
212.
Pierrick Blanchard Nicolas Hanuise Stéphanie Dano Henri Weimerskirch 《Behavioral ecology and sociobiology》2007,61(5):767-773
Sex ratio theory is one of the most controversial topics in evolutionary ecology. Many deviations from an equal production
of males and females are reported in the literature, but few patterns appear to hold across species or populations. There
is clearly a need to identify fitness effects of sex ratio variation. We studied this aspect in a population of a long-lived
seabird, the wandering albatross (Diomedea exulans), using molecular sex-identification techniques. We report that parental traits affect both (1) fledgling traits in a sex-dependent
way and (2) chick sex: Sons are overproduced when likely to be large at fledging and, to a lesser extent, daughters are overproduced
when likely to be in good body condition at fledging. Because for the same population, a previous study reported that post-fledging
survival was positively affected by size in males and by body condition in females, our results suggest that wandering albatrosses
manipulate offspring sex to increase post-fledging survival. 相似文献
213.
Guangquan Li Yuan Cheng Bei Zhao 《Journal of the American Water Resources Association》2012,48(6):1233-1240
Li, Guangquan, Yuan Cheng, and Bei Zhao, 2012. Analysis of the Effect of the Beavers‐Joseph Interface Condition on Flow in Karst Conduits. Journal of the American Water Resources Association (JAWRA) 1‐8. DOI: 10.1111/j.1752‐1688.2012.00683.x Abstract: In this study, we derive an approximate analytic solution for the distribution of flow velocity in a cylindrical conduit and the surrounding media, and analyze the effect of differing parameters (e.g., conduit radius) on the velocity of conduit flow. The solution is then employed to estimate the thickness of the boundary layer inside the media. The results reveal that when conduit radius is large, the Beavers‐Joseph condition has only a minor effect on the velocity of conduit flow (such that the nonslip condition on the conduit wall still works pretty well), and the boundary layer is so thin that the wall can still be treated as the interface between fast water in the conduit and slow water in the media. The solution indicates that the velocity of conduit flow is the superposition of the velocity profile in the nonslip situation onto the slip velocity on the wall. Our study theoretically shows that the coupled continuum pipe flow model in MODFLOW‐2005 constructed by the U.S. Geological Survey is reasonable in that there is no need to consider the Beavers‐Joseph condition when simulating flow in karst conduits. The role of the boundary layer in transport and its effect on the hyporheic zone is not clear, which is a suitable topic for future study. 相似文献
214.
215.
216.
David P. Larsen Anthony R. Olsen Steven H. Lanigan Chris Moyer Kim K. Jones Thomas M. Kincaid 《Journal of the American Water Resources Association》2007,43(2):384-397
Abstract: Multiple agencies in the Pacific Northwest monitor the condition of stream networks or their watersheds. Some agencies use a stream “network” perspective to report on the fraction or length of the network that either meets or violates particular criteria. Other agencies use a “watershed” perspective to report on the health or condition of watersheds. The agencies often use the same indicators and measurement protocols for data collection and often conduct monitoring in overlapping geographic regions. In these situations, agencies would like to combine data across different monitoring studies in a statistically sound manner to make regional estimates of condition. Three statistical survey design principles will facilitate combining such studies: (1) a clearly specified statistical target population of interest, including elements that comprise the population, (2) a consistent representation of that target population (such as a digital map of the stream network and watersheds), and (3) rules that incorporate randomization to guide the selection of the sample of sites on which measurements will be made. A case study illustrates the application of these design principles using two agency monitoring programs interested in combining stream channel data for different purposes: one for making network summaries and the other for evaluating watershed condition. 相似文献
217.
218.
ABSTRACT: The pebble count, a quick and simple technique for characterizing streambed materials, has long been used by geomorphologists, hydrologists, and river engineers. This paper describes how pebble counts have been used to monitor fine sediment (particles less then 6 mm in size) on the Boise National Forest. Data from two watersheds subjected to major wildfires and the failure of a dam are discussed. Following wildfires, pebble count data showed increases in streambed fines followed by improvement of the stream substrate with time as the watersheds recovered. For the dam failure, pebble count data showed an increase in fines in the stream below the failure and were used to track the distance of sediment movement downstream. Pebble counts may be best used where fine sediment on channel substrates are a concern, such as in granitic watersheds where coarse sands are a large component of bedload and land-disturbing activities introduce fine sediment into streams. Pebble counts are found to be a simple and rapid monitoring method that can be used to help determine whether or not land management activities or land disturbances are introducing fine sediment into streams. 相似文献
219.
220.
沼气液态深层发酵及秸秆的物理、化学和生物预处理方式存在效率低、污染重等问题。为了解决这些问题,对蒸汽爆破预处理方式以及固态发酵在玉米秸秆沼气化中的应用进行了研究。秸秆经过蒸汽爆破预处理后,在50℃的高温条件下进行固态发酵沼气,甲烷产量达到138.2 mL/g TS。通过单因素实验优化,确定最佳发酵条件为:固液比1∶7,初始pH值7.5,接种量35%,NH4HCO3添加量0.04 g/g干汽爆秸秆,纤维素酶用量30 IU/g干汽爆秸秆,发酵温度50℃。在上述实验条件下,汽爆秸秆的甲烷产量提高至153.0 mL/g TS,是未汽爆秸秆的2.9倍。发酵后秸秆纤维素和半纤维素的降解率分别为59.86%和67.22%。因此,蒸汽爆破预处理有助于提高秸秆的产气量和降解率。高温固态发酵不仅可以缩短发酵延迟期,提高产气效率,而且发酵结束后不会产生大量废液,对环境友好。 相似文献