全文获取类型
收费全文 | 39312篇 |
免费 | 392篇 |
国内免费 | 412篇 |
专业分类
安全科学 | 889篇 |
废物处理 | 1991篇 |
环保管理 | 5237篇 |
综合类 | 6841篇 |
基础理论 | 10265篇 |
环境理论 | 13篇 |
污染及防治 | 9306篇 |
评价与监测 | 2747篇 |
社会与环境 | 2660篇 |
灾害及防治 | 167篇 |
出版年
2022年 | 254篇 |
2021年 | 260篇 |
2020年 | 232篇 |
2019年 | 229篇 |
2018年 | 1822篇 |
2017年 | 1691篇 |
2016年 | 1734篇 |
2015年 | 620篇 |
2014年 | 742篇 |
2013年 | 2304篇 |
2012年 | 1356篇 |
2011年 | 2579篇 |
2010年 | 1667篇 |
2009年 | 1703篇 |
2008年 | 2122篇 |
2007年 | 2484篇 |
2006年 | 1190篇 |
2005年 | 1026篇 |
2004年 | 1058篇 |
2003年 | 1029篇 |
2002年 | 1011篇 |
2001年 | 1159篇 |
2000年 | 828篇 |
1999年 | 551篇 |
1998年 | 360篇 |
1997年 | 401篇 |
1996年 | 412篇 |
1995年 | 460篇 |
1994年 | 404篇 |
1993年 | 385篇 |
1992年 | 345篇 |
1991年 | 369篇 |
1990年 | 344篇 |
1989年 | 314篇 |
1988年 | 301篇 |
1987年 | 266篇 |
1986年 | 273篇 |
1985年 | 270篇 |
1984年 | 341篇 |
1983年 | 296篇 |
1982年 | 315篇 |
1981年 | 282篇 |
1980年 | 236篇 |
1979年 | 252篇 |
1978年 | 212篇 |
1977年 | 199篇 |
1976年 | 167篇 |
1975年 | 183篇 |
1974年 | 192篇 |
1972年 | 170篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
62.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
63.
The occurrence and impact of psychological contract violations were studied among graduate management alumni (N = 128) who were surveyed twice, once at graduation (immediately following recruitment) and then two years later. Psychological contracts, reciprocal obligations in employment developed during and after recruitment, were reported by a majority of respondents (54.8 per cent) as having been violated by their employers. The impact of violations are examined using both quantitative and qualitative data. Occurrence of violations correlated positively with turnover and negatively with trust, satisfaction and intentions to remain. 相似文献
64.
N. L. Ivanova 《Russian Journal of Ecology》2002,33(2):125-129
Environmental conditions in cooling ponds of thermal power plants are favorable for marsh frogs. Their populations inhabiting Verkhne-Tagil and Reftinskoe reservoirs differ in some traits, such as size and age composition, growth rate after metamorphosis, spawning type, fecundity, and characteristics of larval development. Differentiation in body size manifests itself at the early stages of terrestrial life and progresses at later stages. As a consequence, larger individuals may reach maturity and participate in reproduction at an earlier age. 相似文献
65.
Long-term stationary studies on the ecology of the northern mole vole (Ellobius talpinus Pall.), performed by the mark–recapture method from 1985 to 1997, have provided original data on population dynamics and structure. The analysis shows that, to reveal cyclic fluctuations of population size in this species, the period of three years should be taken as a unit of time for estimating the duration of one phase. The 12-year population cycle in E. talpinus has four distinct phases: an increase, a peak, a decline, and a minimum. At each phase, the population is characterized by certain features of family structure, age composition, birth and death rates, and the composition of migrants. 相似文献
66.
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
67.
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
68.
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
69.
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
70.
Whereas past research has treated co-management of common pool resources as if villagers and project implementing authorities
were the only relevant actors, numerous external factors beyond the control of these two partners create barriers to successful
co-management. This paper draws on discussions with Forest Department officials to examine the influence of these forces on
the outcomes of Joint Forest Management (JFM) in Tamil Nadu, India. An empirical inquiry into the operational aspects of JFM
indicates the important roles of political parties, powerful people, and other state institutions and functionaries as well
as the flow of foreign funding. Further, the strong demand by local people for socio-economic development interventions as
opposed to improvement of degraded forests belittles the role of the Forest Department relative to other departments. Numerous
other conditioning factors and relationships are explored. The authors call for reforms in public governance to allow better
participation of all the actors involved for this participatory management approach to succeed and sustain. 相似文献