全文获取类型
收费全文 | 43098篇 |
免费 | 478篇 |
国内免费 | 396篇 |
专业分类
安全科学 | 1434篇 |
废物处理 | 1946篇 |
环保管理 | 5939篇 |
综合类 | 6218篇 |
基础理论 | 11391篇 |
环境理论 | 11篇 |
污染及防治 | 11168篇 |
评价与监测 | 2962篇 |
社会与环境 | 2620篇 |
灾害及防治 | 283篇 |
出版年
2022年 | 363篇 |
2021年 | 427篇 |
2020年 | 259篇 |
2019年 | 348篇 |
2018年 | 618篇 |
2017年 | 652篇 |
2016年 | 996篇 |
2015年 | 772篇 |
2014年 | 1182篇 |
2013年 | 3759篇 |
2012年 | 1423篇 |
2011年 | 1888篇 |
2010年 | 1534篇 |
2009年 | 1628篇 |
2008年 | 1957篇 |
2007年 | 1923篇 |
2006年 | 1767篇 |
2005年 | 1498篇 |
2004年 | 1491篇 |
2003年 | 1427篇 |
2002年 | 1356篇 |
2001年 | 1628篇 |
2000年 | 1194篇 |
1999年 | 715篇 |
1998年 | 552篇 |
1997年 | 531篇 |
1996年 | 594篇 |
1995年 | 655篇 |
1994年 | 595篇 |
1993年 | 529篇 |
1992年 | 514篇 |
1991年 | 504篇 |
1990年 | 484篇 |
1989年 | 476篇 |
1988年 | 441篇 |
1987年 | 369篇 |
1986年 | 369篇 |
1985年 | 360篇 |
1984年 | 420篇 |
1983年 | 398篇 |
1982年 | 414篇 |
1981年 | 376篇 |
1980年 | 278篇 |
1979年 | 320篇 |
1978年 | 266篇 |
1977年 | 218篇 |
1976年 | 198篇 |
1975年 | 217篇 |
1973年 | 246篇 |
1972年 | 226篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
Assessment of environmental changes in the Orinoco River delta 总被引:1,自引:0,他引:1
H. Echezuría J. Córdova M. González V. González J. Méndez C. Yanes 《Regional Environmental Change》2002,3(1-3):20-35
Major anthropogenic driven changes in the hydrologic and sedimentation patterns of the Orinoco River have had an impact on
environmental conditions in the delta. The abrupt water flow reduction from 3,600 to 200 m3 s–1 in one of its major distributaries resulting from dam construction forced its transformation from a fresh-water body into
a tidal channel with an increase in salinity level (as far as 100 km upstream) and with well-mixed water at the mouth and
estuarine connection to the Paria Gulf. Three different sectors along this distributary can be identified (indicated by the
Na/Cl ratio in the water). As a result, noticeable changes have occurred in the mangrove community which moved about 60 km
further upstream. The changes have also promoted the formation of new islands of sediment progradation at the mouth of this
distributary, where successional colonization and species replacement by different species of grasses and mangroves take place.
Electronic Publication 相似文献
93.
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
94.
95.
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
96.
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
97.
98.
In situ assessment of modification of sediment properties by burrowing invertebrates 总被引:4,自引:0,他引:4
Benthic organisms can significantly alter the physical properties of marine sediments, but it has hitherto been difficult to assess and quantify the effects of bioturbation. In situ geophysical techniques offer new methods for measuring these effects: measurement of acoustic shear-wave velocity and electrical resistivity allows nondestructive assessment of the properties of the grain framework and pore-fluid matrix, respectively, of the seabed sediment. The influence of burrowing invertebrates on the structural properties of sandy sediments at intertidal locations on the coast of Wales (UK) was investigated during the periol 1986–1987 using these techniques. Three species (Arenicola marina, Corophium arenarium and Lanice conchilega) were selected on the basis of their contrasting styles of burrow construction. All three species produced measurable and significant, although different, changes in bed properties. They modified shear-wave propagation through the bed by changing bed rigidity: while A. marina and C. arenarium decreased rigidity by creating open burrows, L. conchilega increased rigidity by building shell-lined tubes. All produced a decrease in electrical resistivity by altering porosity and/or tortuosity, which implies an increase in permeability; these changes were attributable not only to the presence of the burrows but also to modification of the between-burrow sediment texture and bed properties. 相似文献
99.
Danny Reible David Lampert David Constant Robert D. Mutch Jr. Yuewei Zhu 《补救:环境净化治理成本、技术与工艺杂志》2006,17(1):39-53
An active capping demonstration project in Washington, D.C., is testing the ability to place sequestering agents on contaminated sediments using conventional equipment and evaluating their subsequent effectiveness relative to conventional passive sand sediment caps. Selected active capping materials include: (1) AquaBlokTM, a clay material for permeability control; (2) apatite, a phosphate mineral for metals control; (3) coke, an organic sequestration agent; and (4) sand material for a control cap. All of the materials, except coke, were placed in 8,000‐ft test plots by a conventional clamshell method during March and April 2004. Coke was placed as a 1.25‐cm layer in a laminated mat due to concerns related to settling of the material. Postcap sampling and analysis were conducted during the first, sixth, and eighteenth months after placement. Although postcap sampling is expected to continue for at least an additional 24 months, this article summarizes the results of the demonstration project and postcap sampling efforts up to 18 months. Conventional clamshell placement was found to be effective for placing relatively thin (six‐inch) layers of active material. The viability of placing high‐value or difficult‐to‐place material in a controlled manner was successfully demonstrated with the laminated mat. Postcap monitoring indicates that all cap materials effectively isolated contaminants, but it is not yet possible to differentiate between conventional sand and active cap layer performance. Monitoring of the permeability control layer indicated effective reductions in groundwater seepage rates through the cap, but also showed the potential for gas accumulation and irregular release. All of the cap materials show deposition of new contaminated sediment onto the surface of the caps, illustrating the importance of source control in maintaining sediment quality. © 2006 Wiley Periodicals, Inc. 相似文献
100.
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