全文获取类型
收费全文 | 20679篇 |
免费 | 186篇 |
国内免费 | 196篇 |
专业分类
安全科学 | 568篇 |
废物处理 | 878篇 |
环保管理 | 2763篇 |
综合类 | 2812篇 |
基础理论 | 5806篇 |
环境理论 | 4篇 |
污染及防治 | 5760篇 |
评价与监测 | 1342篇 |
社会与环境 | 1004篇 |
灾害及防治 | 124篇 |
出版年
2022年 | 130篇 |
2021年 | 162篇 |
2020年 | 100篇 |
2019年 | 143篇 |
2018年 | 350篇 |
2017年 | 354篇 |
2016年 | 573篇 |
2015年 | 386篇 |
2014年 | 518篇 |
2013年 | 1556篇 |
2012年 | 984篇 |
2011年 | 972篇 |
2010年 | 623篇 |
2009年 | 738篇 |
2008年 | 860篇 |
2007年 | 936篇 |
2006年 | 818篇 |
2005年 | 1003篇 |
2004年 | 1147篇 |
2003年 | 997篇 |
2002年 | 652篇 |
2001年 | 790篇 |
2000年 | 577篇 |
1999年 | 337篇 |
1998年 | 236篇 |
1997年 | 229篇 |
1996年 | 270篇 |
1995年 | 275篇 |
1994年 | 257篇 |
1993年 | 230篇 |
1992年 | 208篇 |
1991年 | 192篇 |
1990年 | 210篇 |
1989年 | 193篇 |
1988年 | 180篇 |
1987年 | 171篇 |
1986年 | 148篇 |
1985年 | 146篇 |
1984年 | 176篇 |
1983年 | 174篇 |
1982年 | 166篇 |
1981年 | 169篇 |
1980年 | 136篇 |
1979年 | 159篇 |
1978年 | 108篇 |
1977年 | 100篇 |
1976年 | 88篇 |
1975年 | 96篇 |
1973年 | 93篇 |
1972年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
We examined the impact of stressful job demands on employee attitudes and attendance. Using Karasek's (1979) theory of job decision latitude as the conceptual foundation, we hypothesized that mental and physical work demands would interact with employee beliefs of personal control. Survey data from 90 male manufacturing employees regarding their control beliefs were combined with objective job analysis data concerning mental and physical demands and one year's worth of archival data regarding unexcused absences, sick days, and days tardy. There were significant interactions between control and objective psychological demands that indicated that these demands were associated with higher levels of tardiness and sick days only under conditions of low perceived control. In contrast, subjective workload ratings showed no relationship with tardiness and sick days, but, in interaction with control, predicted work satisfaction and voluntary absence. We discussed these results in terms of a stress process that affects health-related attendance independent of employee attitudes. 相似文献
42.
43.
Paul C. James 《Conservation biology》1994,8(4):1161-1162
44.
45.
46.
47.
Dr. J. F. Bruch P. Metezeau N. Garcia-Fonknechten Y. Richard V. Tricottet B.-L. Hsi A. Kitzis C. Julien E. Papiernik 《黑龙江环境通报》1991,11(10):787-798
Three monoclonal antibodies (MAbs) against trophoblast (GB17, GB21, and GB25) and flow cytometry were used to sort trophoblast-like cells (TLCs) from peripheral blood of pregnant women. Sorted TLCs were processed for electron microscopy and fetal DNA amplification of the Y-specific sequences from mothers carrying male fetuses. At the ultra-structural level, most of the nucleated cells had the morphology of leucocytes, suggesting maternal contaminants, and we did not find the characteristic features of the free inter-villous trophoblast cells. Nevertheless, polymerase chain reaction (PCR) analysis showed an amplification of Y-specific sequences in two out of three samples of sorted TLCs. These results suggest that besides the maternal leucocytes, sufficient trophoblast nucleated fetal cells can be obtained using cell enrichment by sorting. This sensitive method holds promise for non-invasive prenatal diagnosis of fetal sex and if sufficient Y(positive) nuclei are found, for the diagnosis of selected numerical chromosome abnormalities. 相似文献
48.
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
49.
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
50.
Pyrite ash is created as waste from the roasting of pyrite ores during the production of sulphuric acid. These processes generate great amounts of pyrite ash waste that is generally land filled. This creates serious environmental pollution due to the release of acids and toxic substances. Pyrite ash waste can be utilized in the iron production industry as a blast furnace feed to process this waste and prevent environmental pollution. The essential parameters affecting the pelletization process of pyrite ash were studied using bentonite as a binder. Experiments were then carried out using bentonite and a mixture of bentonite with calcium hydroxide and calcium chloride in order to make the bentonite more effective. The metallurgical properties of pyrite ash, bentonite, calcium hydroxide, calcium chloride, a mixture of these and sintered pellets were studied using X-ray analysis. The crushing strength tests were carried out to investigate the strength of pyrite ash waste pellets. The results of these analyses showed that pyrite ash can be agglomerated to pellets and used in the iron production industry as a blast furnace feed. The crushing strength of the pellets containing calcium hydroxide and calcium chloride in addition to bentonite was better than the strength of pellets prepared using only bentonite binder. 相似文献