全文获取类型
收费全文 | 10119篇 |
免费 | 1篇 |
国内免费 | 3篇 |
专业分类
安全科学 | 8篇 |
废物处理 | 789篇 |
环保管理 | 1241篇 |
综合类 | 1116篇 |
基础理论 | 3179篇 |
污染及防治 | 1834篇 |
评价与监测 | 1044篇 |
社会与环境 | 912篇 |
出版年
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 1479篇 |
2017年 | 1375篇 |
2016年 | 1200篇 |
2015年 | 136篇 |
2014年 | 32篇 |
2013年 | 27篇 |
2012年 | 479篇 |
2011年 | 1358篇 |
2010年 | 702篇 |
2009年 | 605篇 |
2008年 | 901篇 |
2007年 | 1256篇 |
2006年 | 15篇 |
2005年 | 33篇 |
2004年 | 52篇 |
2003年 | 73篇 |
2002年 | 111篇 |
2001年 | 19篇 |
2000年 | 18篇 |
1999年 | 9篇 |
1998年 | 14篇 |
1997年 | 4篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1990年 | 4篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1979年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1966年 | 6篇 |
1965年 | 3篇 |
1964年 | 7篇 |
1963年 | 4篇 |
1962年 | 3篇 |
1961年 | 6篇 |
1960年 | 7篇 |
1959年 | 9篇 |
1958年 | 6篇 |
1957年 | 11篇 |
1956年 | 4篇 |
1955年 | 9篇 |
1954年 | 8篇 |
1952年 | 5篇 |
1950年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Cynthia J. Sims MD Don T. Fujito Dennis R. Burholt Josef Dadok Harlan R. Giles D. Allan Wilkinson 《黑龙江环境通报》1993,13(6):473-480
We have investigated the ability of high-resolution proton NMR spectroscopy to provide a biochemical constituent screening of human amniotic fluid (AF). Proton NMR spectra were obtained at 300 MHz on AF from patients undergoing amniocentesis in the mid-trimester. Only AF from normal pregnancies (normal fetal karyotype, normal a-fetoprotein levels, normal birth outcome) was used in this study. The AF supernatant was lyophilized and resuspended in deuterated water containing 0.1 mm phosphate buffer and 6.02 mm disodium maleate. Identification of low molecular weight compounds was confirmed by two-dimensional NMR spectra (primarily correlated spectroscopy, or COSY) and standard addition techniques. A broad profile of compounds were ‘NMR visible’ in a single proton spectrum, including creatinine, glucose, organic acids (acetate, citrate, and lactate) and several amino acids (alanine, histidine, leucine, phenylalanine, tyrosine and valine). The proton spectrum was unaffected by prior freezing/thawing of AF samples. We were able to quantify compounds by comparison with an added concentration standard (maleate) at concentrations as low as 30 μm. Good agreement with literature values based on other analytical techniques was obtained. 相似文献
5.
6.
7.
8.
9.
Traditional knowledge and practices are important in prudent resource use and biodiversity conservation. The implications of modernization and changing lifestyle are discussed in the context of agriculture and resource use, the two sectors in which maximum modernization has occurred. The information was gathered through observations and structured interviews over three years (July 1996 to July 1999) of field work in the western Himalaya. It was observed that forest based subsistence agriculture has given way to the market dependant cash crop cultivation. That apart from loss of genetic diversity, has also resulted in the degradation of forests. The use of wild plants in the day-to-day activities has also declined and dependence on high value market products has increased. Currently, wild plants are used only if no other cheap substitute is available in the market or if the use is economically beneficial to the people. Thus, the knowledge gathered through ages of experience is eroding because of the activities geared for short-term economic benefits which, in long run, may not be sustainable. 相似文献
10.
River damming provides a dominant human impact on river environments worldwide, and while local impacts of reservoir flooding
are immediate, subsequent ecological impacts downstream can be extensive. In this article, we assess seven research strategies
for analyzing the impacts of dams and river flow regulation on riparian ecosystems. These include spatial comparisons of (1)
upstream versus downstream reaches, (2) progressive downstream patterns, or (3) the dammed river versus an adjacent free-flowing
or differently regulated river(s). Temporal comparisons consider (4) pre- versus post-dam, or (5) sequential post-dam conditions.
However, spatial comparisons are complicated by the fact that dams are not randomly located, and temporal comparisons are
commonly limited by sparse historic information. As a result, comparative approaches are often correlative and vulnerable
to confounding factors. To complement these analyses, (6) flow or sediment modifications can be implemented to test causal
associations. Finally, (7) process-based modeling represents a predictive approach incorporating hydrogeomorphic processes
and their biological consequences. In a case study of Hells Canyon, the upstream versus downstream comparison is confounded
by a dramatic geomorphic transition. Comparison of the multiple reaches below the dams should be useful, and the comparison
of Snake River with the adjacent free-flowing Salmon River may provide the strongest spatial comparison. A pre- versus post-dam
comparison would provide the most direct study approach, but pre-dam information is limited to historic reports and archival
photographs. We conclude that multiple study approaches are essential to provide confident interpretations of ecological impacts
downstream from dams, and propose a comprehensive study for Hells Canyon that integrates multiple research strategies. 相似文献