全文获取类型
收费全文 | 42276篇 |
免费 | 562篇 |
国内免费 | 545篇 |
专业分类
安全科学 | 1492篇 |
废物处理 | 1952篇 |
环保管理 | 5901篇 |
综合类 | 6674篇 |
基础理论 | 11054篇 |
环境理论 | 15篇 |
污染及防治 | 10555篇 |
评价与监测 | 2774篇 |
社会与环境 | 2672篇 |
灾害及防治 | 294篇 |
出版年
2022年 | 390篇 |
2021年 | 435篇 |
2020年 | 332篇 |
2019年 | 341篇 |
2018年 | 636篇 |
2017年 | 647篇 |
2016年 | 1000篇 |
2015年 | 756篇 |
2014年 | 1157篇 |
2013年 | 3486篇 |
2012年 | 1450篇 |
2011年 | 1982篇 |
2010年 | 1588篇 |
2009年 | 1688篇 |
2008年 | 1982篇 |
2007年 | 1944篇 |
2006年 | 1731篇 |
2005年 | 1498篇 |
2004年 | 1463篇 |
2003年 | 1372篇 |
2002年 | 1284篇 |
2001年 | 1524篇 |
2000年 | 1137篇 |
1999年 | 721篇 |
1998年 | 516篇 |
1997年 | 545篇 |
1996年 | 552篇 |
1995年 | 661篇 |
1994年 | 554篇 |
1993年 | 495篇 |
1992年 | 502篇 |
1991年 | 489篇 |
1990年 | 466篇 |
1989年 | 456篇 |
1988年 | 402篇 |
1987年 | 343篇 |
1986年 | 363篇 |
1985年 | 352篇 |
1984年 | 413篇 |
1983年 | 359篇 |
1982年 | 402篇 |
1981年 | 345篇 |
1980年 | 273篇 |
1979年 | 307篇 |
1978年 | 237篇 |
1977年 | 210篇 |
1975年 | 211篇 |
1974年 | 208篇 |
1973年 | 234篇 |
1972年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We present a case of ultrasonographic prenatal diagnosis at 24 weeks of femur—fibula—ulna (FFU) complex. To our knowledge, this is the first report of an early prenatal diagnosis of FFU. 相似文献
82.
83.
Observations of air temperature changes in a steppe marmot burrow were performed from late July to mid-October. Until early September, temperature in the burrow remained relatively constant, but then it began to decrease rapidly. This occurred after air temperature above the ground became equal to the temperature in the burrow. Supposedly, it is in this particular period that marmots begin to plug the entrance to the burrow with earth, thus reducing heat exchange between the increasingly cold aboveground air and the air in the burrow. 相似文献
84.
V. I. Kolmakov N. A. Gaevskii E. A. Ivanova O. P. Dubovskaya I. V. Gribovskaya E. S. Kravchuk 《Russian Journal of Ecology》2002,33(2):97-103
In the periods of summer and autumn bloom of the Stephanodiscus hantzschii Crun. in recreational water bodies, studies on the vertical distribution of chlorophyll a, its contents per unit biomass, efficiency in using photosynthetically active radiation (EPhAR), and assimilative activity of microalgae were performed. The results confirmed the existence of two ecophysiological forms of St. hantzschii and provided evidence that both forms are typically autotrophic and can efficiently use low-intensity PhAR for photosynthesis. 相似文献
85.
On-going population growth and resulting domestic demand for water require rapid and effective decision-making as regards groundwater management and control of the various sources of salinization and pollution in Coastal aquifers. Sustainability of water resources for utilization by future generations must therefore be a high priority, not only for the purpose of fulfilling needs for water usage but also for bringing people into harmony with their ambient natural environment.The objective of this paper is to propose an empirical approach for prioritization of the needs involved for sustainable aquifer management. The approach involves a schematic format to:(1) develop a global understanding of an aquifer's hydrological and environmental properties in order to delineate appropriate eco-hydrological scenarios and recommend corresponding operational management activities; and(2) emphasize the importance of educating and increasing the awareness of the population involved as to the need for and viability of socially acceptable measures for sustainable management of groundwater and other resources.The psychologist Abraham Maslow utilized a pyramid to illustrate that until people's most basic needs were fulfilled, higher levels of needs would remain irrelevant. This paper postulates a comparable pyramid prioritizing hydrological needs required for progressing towards sustainable groundwater resources. Two sub-regions of Israel's Coastal aquifer in the Sharon region have been presented as representative areas, each characterized by different stress of exploitation. In assessing these sub-regions situation, specific measures have been recommended for achieving and/or maintaining sustainable groundwater resources in light of the ambient environment, and the level of the population on the pyramidal hierarchy of groundwater needs. 相似文献
86.
87.
The main purpose of this study is to assess economic vulnerability of small island development regions as part of their sustainability constraints. By combining economic and environmental time series data, we assessed a composite index of economic vulnerability which is constructed from three exogenous variables, namely economic exposure, economic remoteness, and economic impact of environmental and natural disasters. We used the Amami Islands, Kagoshima Prefecture, Japan as the case studies for this paper.The results indicated that using a gross island products based valuation index, Kikaijima is the most vulnerable island in the Amami Islands with a composite economic vulnerability index (CEVI) value of 0.678, while by using a per capita based index, Okinoerabujima is considered the most vulnerable island with a CEVI value of 0.680. From the results we also revealed that smaller islands have relative higher vulnerability than the bigger one, which also confirms some previous country-level vulnerability studies.However, it is matter of fact that some islands that have relatively high vulnerability also have good economic performance as shown by their per capita income. In this regard, it can be argued that the success of these small islands could have been achieved in spite of and not because of their inherent vulnerability conditions as an indicator of sustainability constraint. Regarding these findings, we also examined a comparison between vulnerability results and the preliminary concept of an island's resilience in order to capture another perspective on sustainability assessment in a small island region. 相似文献
88.
N. P. Kosykh N. P. Mironycheva-Tokareva A. M. Peregon E. K. Parshina 《Russian Journal of Ecology》2008,39(7):466-474
New experimental data on biological productivity of plant communities in oligotrophic and mesotrophic bogs of the middle taiga
subzone over the past five years are presented. The relationship between net primary production and the stock of live phytomass
is estimated. The stock of necromass in oligotrophic bog ecosystems increases from west to east, while the stock of live phytomass
and net primary production decrease. 相似文献
89.
Although stewardship has been widely defined and used in environmental management and planning, there is a dearth of studies
that describe how the lay public perceives this concept. A national sample of residents in 14 states who live near DOE nuclear
facilities were interviewed to delineate public understanding and awareness of the stewardship program of the U.S. Department
of Energy (DOE). This study discusses the findings of the survey and discusses how institutional trust influences public participation
and resident’s choices of potential stewards. Almost 40% of the respondents could not define stewardship; those who did, believed
that ‘responsibility,’ ‘management,’ and ‘accountability’ are key elements of stewardship. In addition, about a third of the
respondents identified Federal groups and the DOE as potential stewards.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue 相似文献
90.
Studies on paleosols under an archaeological landmark of a rare type (a complex of kurgans with “whiskers”) dating from the Early Iron Age (the fourth century AD) have been performed in the steppe zone of the Transural Plateau. The size and shape of third-order soil polygons under stony ridges (“whiskers”) between the kurgans have been described in detail. The results have shown that the paleosol under the kurgans erected at the turn of the Late Sarmatian and Hun times (1600 years ago) is characterized by a higher humus content and deeper location of the carbonate horizon, compared to the recent soil. This indicates that an increase in atmospheric humidity took place in the fourth century AD. 相似文献