全文获取类型
收费全文 | 26427篇 |
免费 | 701篇 |
国内免费 | 3708篇 |
专业分类
安全科学 | 1157篇 |
废物处理 | 1312篇 |
环保管理 | 2613篇 |
综合类 | 8413篇 |
基础理论 | 6064篇 |
环境理论 | 4篇 |
污染及防治 | 7626篇 |
评价与监测 | 1576篇 |
社会与环境 | 1484篇 |
灾害及防治 | 587篇 |
出版年
2023年 | 250篇 |
2022年 | 689篇 |
2021年 | 573篇 |
2020年 | 485篇 |
2019年 | 482篇 |
2018年 | 604篇 |
2017年 | 700篇 |
2016年 | 805篇 |
2015年 | 801篇 |
2014年 | 1276篇 |
2013年 | 2235篇 |
2012年 | 1364篇 |
2011年 | 1587篇 |
2010年 | 1341篇 |
2009年 | 1237篇 |
2008年 | 1409篇 |
2007年 | 1331篇 |
2006年 | 1183篇 |
2005年 | 920篇 |
2004年 | 884篇 |
2003年 | 915篇 |
2002年 | 901篇 |
2001年 | 983篇 |
2000年 | 824篇 |
1999年 | 600篇 |
1998年 | 438篇 |
1997年 | 452篇 |
1996年 | 422篇 |
1995年 | 410篇 |
1994年 | 366篇 |
1993年 | 305篇 |
1992年 | 304篇 |
1991年 | 270篇 |
1990年 | 239篇 |
1989年 | 225篇 |
1988年 | 177篇 |
1987年 | 179篇 |
1986年 | 168篇 |
1985年 | 166篇 |
1984年 | 153篇 |
1983年 | 143篇 |
1982年 | 135篇 |
1981年 | 126篇 |
1980年 | 115篇 |
1979年 | 126篇 |
1978年 | 101篇 |
1977年 | 114篇 |
1974年 | 89篇 |
1973年 | 99篇 |
1972年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
11.
陈光辉 《中国个体防护装备》2015,(1):41-43
本文从医学测试、体质测试和心理测试三个方面论述了消防员职业健康测试项目研究的重要性,以促进我国消防员职业健康研究水平的提高。 相似文献
12.
13.
14.
15.
16.
A transition zone in the otoliths of orange roughy (Hoplostethus atlanticus) is described where annulus width decreases markedly. For fish sampled at spawning time, the relationship between gonad stage
and the presence or absence of a transition zone is consistent with the hypothesis that this zone marks the onset of maturity,
if allowance is made for some error in gonad staging and identification of the zone. Another data set from a non-spawning
area after the spawning season is not consistent with the hypothesis. However, these latter data are considered less reliable
because of the small size of the fish in the sample and difficulties in determining, outside the spawning season, whether
a fish has been reproductively active. This hypothesis was used to provide estimates of the median age (30 yr) and length
(31 cm) at the onset of maturity for the Chatham Rise, New Zealand population. These estimates are unaffected by the biases
associated with the usual ogive method of estimation.
Received: 27 June 1997 / Accepted: 1 July 1997 相似文献
17.
重点开发长江是90年代中国经济重大战略布署。将长江产业带建设成具有强大经济实力的国家一级经济轴线,宜采用分层次推进与中心辐射相结合的发展战略,以浦东开发和三峡建设为契机,加强基础产业,发展新兴产业和第三产业,优化产业结构,以能源和交通建设先行,改善基础设施。同时,要协调产业带建设与浦东开发、三峡工程建设的关系。 相似文献
18.
Rapid growth of clones of the red alga Chondrus crispus: applications in assays of toxic substances and in physiological studies 总被引:1,自引:0,他引:1
Growth rates of excised apical segments from three Chondrus crispus Stackhouse clones were rapid, reproducible and easily measured using simple equipment. Clonal segments exhibited a high degree of phenotypic stability, with coefficients of variation in growth rates being typically less than 5%. Sensitivity of the assay was demonstrated using 24-h pulses of the toxicants Cu2+ (10 to 150 ppb) and the molluscicide Bayluscide (100 to 500 ppb). As a further demonstration of applicability of this assay system, growth rates were measured over two consecutive 24-h photoperiods using a normally pigmented red gametophytic clone and a green colored mutant derived from it. Growth rates were highest in the first hours of the light phase for both clones, with growth of the green mutant being consistently inferior to that of the normally pigmented one. Significant changes were measured with intervals as short as 4 h using only five apical segments for each treatment. The C. crispus assay described is sensitive, relatively rapid, and statistically robust when applied to toxicant testing in seawater and to physiological studies. 相似文献
19.
The feasibility of using U.K. coal-fired power station waste materials for artificial reef production is being examined. in June, 1989, an experimental artificial reef was constructed in Poole Bay, off the central south coast of the U.K., using three different mixtures of pulverised fuel ash (PFA), flue gas desulphurisation (FGD) gypsum and slurry, stabilized with cement and formed into blocks. Fifty tonnes of 40 × 20 × 20 cm blocks were formed into eight conical reef units replicating three different PFA/gypsum mixtures and one concrete control. the reef structure is 10m below chart datum on a flat sandy sea-bed.
Combustion of coal concentrates the heavy metal content in the resultant ash. the purpose of stabilization of the ash as blocks is twofold: to immobilize heavy metals (or other components) and to provide hard substratum for the attachment of organisms. to examine the effectiveness of this stabilization and hence the environmental compatibility of the block materials, heavy metal (Cd, Cr, Cu, Pb, Mn, Ni, Zn) content of the blocks has been monitored routinely over two years, to determine leaching rates. Sectional profiles indicate partial replacement of calcium content by magnesium. Associated with this there has also been some redistribution of heavy metals. Only in the case of cadmium has there been a detectable loss from the surface of blocks. Chromium and manganese concentrations appear to have increased. the metal content of the reef epibiota (including ascidians, Ascidia mentula; hydroids, Halecium spp.; bryozoans, Bugula spp. and red algae) growing on the ash blocks has been compared to that of epibiota attached to the concrete controls and surrounding sea-bed. to date no evidence of excess bioaccumulation of metals has been detected.
The physical integrity of the ash reef blocks has been maintained. There is evidence that the blocks are increasing in compressive strength.
An indication of the fishery enhancement potential of the experimental structure is given by the presence of eight commercially fished species (crustaceans and molluscs) including lobsters (Homarus gammarus). 相似文献
Combustion of coal concentrates the heavy metal content in the resultant ash. the purpose of stabilization of the ash as blocks is twofold: to immobilize heavy metals (or other components) and to provide hard substratum for the attachment of organisms. to examine the effectiveness of this stabilization and hence the environmental compatibility of the block materials, heavy metal (Cd, Cr, Cu, Pb, Mn, Ni, Zn) content of the blocks has been monitored routinely over two years, to determine leaching rates. Sectional profiles indicate partial replacement of calcium content by magnesium. Associated with this there has also been some redistribution of heavy metals. Only in the case of cadmium has there been a detectable loss from the surface of blocks. Chromium and manganese concentrations appear to have increased. the metal content of the reef epibiota (including ascidians, Ascidia mentula; hydroids, Halecium spp.; bryozoans, Bugula spp. and red algae) growing on the ash blocks has been compared to that of epibiota attached to the concrete controls and surrounding sea-bed. to date no evidence of excess bioaccumulation of metals has been detected.
The physical integrity of the ash reef blocks has been maintained. There is evidence that the blocks are increasing in compressive strength.
An indication of the fishery enhancement potential of the experimental structure is given by the presence of eight commercially fished species (crustaceans and molluscs) including lobsters (Homarus gammarus). 相似文献
20.
本文从柑桔冻害和热害的危害因子和指标等级划分的研究和选取入手,着重探讨了长江三峡地区(湖北境内)两害显著的时空变化特征、差异与关联性及对柑桔生产的影响;揭示了80年代以来冬暖春热的重大气候变化是使两害向“两极分化”的根本原因;讨论了三峡水利工程对两害时空格局的可能调整及减灾原理;最后提出了可能的对策。 相似文献