全文获取类型
收费全文 | 27333篇 |
免费 | 245篇 |
国内免费 | 161篇 |
专业分类
安全科学 | 585篇 |
废物处理 | 1426篇 |
环保管理 | 3931篇 |
综合类 | 4169篇 |
基础理论 | 7415篇 |
环境理论 | 12篇 |
污染及防治 | 6099篇 |
评价与监测 | 2072篇 |
社会与环境 | 1888篇 |
灾害及防治 | 142篇 |
出版年
2022年 | 138篇 |
2021年 | 150篇 |
2020年 | 137篇 |
2019年 | 168篇 |
2018年 | 1663篇 |
2017年 | 1584篇 |
2016年 | 1553篇 |
2015年 | 451篇 |
2014年 | 436篇 |
2013年 | 1587篇 |
2012年 | 998篇 |
2011年 | 2016篇 |
2010年 | 1255篇 |
2009年 | 1204篇 |
2008年 | 1567篇 |
2007年 | 1907篇 |
2006年 | 721篇 |
2005年 | 590篇 |
2004年 | 614篇 |
2003年 | 637篇 |
2002年 | 602篇 |
2001年 | 601篇 |
2000年 | 464篇 |
1999年 | 284篇 |
1998年 | 242篇 |
1997年 | 228篇 |
1996年 | 245篇 |
1995年 | 262篇 |
1994年 | 240篇 |
1993年 | 237篇 |
1992年 | 233篇 |
1991年 | 229篇 |
1990年 | 230篇 |
1989年 | 193篇 |
1988年 | 176篇 |
1987年 | 152篇 |
1986年 | 188篇 |
1985年 | 176篇 |
1984年 | 202篇 |
1983年 | 190篇 |
1982年 | 183篇 |
1981年 | 187篇 |
1980年 | 166篇 |
1979年 | 160篇 |
1978年 | 118篇 |
1977年 | 129篇 |
1974年 | 117篇 |
1973年 | 95篇 |
1972年 | 114篇 |
1971年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
281.
E.F. Brünig 《Agriculture, ecosystems & environment》1984,11(2):191
282.
This paper considers relationships between sustainability objectives, transport, spatial design of the built environment and rational use of energy. Conventional transport modelling, housing supply and energy assessment tools are drawn together to provide a common platform for appraisal of city-wide energy use by stationary and mobile sources. The paper outlines methodologies developed for the city of Belfast, Northern Ireland. The paper concludes by briefly reviewing the effect in terms of mobile and stationary energy consumption and travel behaviour of implementing sustainable policy measures in current and future years within the study area. 相似文献
283.
Scale,context, and decision making in agricultural adaptation to climate variability and change 总被引:3,自引:0,他引:3
Risbey James Kandlikar Milind Dowlatabadi Hadi Graetz Dean 《Mitigation and Adaptation Strategies for Global Change》1999,4(2):137-165
This work presents a framework for viewing agricultural adaptation, emphasizing the multiple spatial and temporal scales on which individuals and institutions process information on changes in their environment. The framework is offered as a means to gain perspective on the role of climate variability and change in agricultural adaptation, and developed for a case study of Australian agriculture. To study adaptation issues at the scale of individual farms we developed a simple modelling framework. The model highlights the decision making element of adaptation in light of uncertainty, and underscores the importance of decision information related to climate variability. Model results show that the assumption of perfect information for farmers systematically overpredicts adaptive performance. The results also suggest that farmers who make tactical planting decisions on the basis of historical climate information are outperformed by those who use even moderately successful seasonal forecast information. Analysis at continental scales highlights the prominent role of the decline in economic operating conditions on Australian agriculture. Examples from segments of the agricultural industry in Australia are given to illustrate the importance of appropriate scale attribution in adapting to environmental changes. In particular, adaptations oriented toward short time scale changes in the farming environment (droughts, market fluctuations) can be limited in their efficacy by constraints imposed by broad changes in the soil/water base and economic environment occuring over longer time scales. The case study also makes the point that adaptation must be defined in reference to some goal, which is ultimately a social and political exercise. Overall, this study highlights the importance of allowing more complexity (limited information, risk aversion, cross-scale interactions, mis-attribution of cause and effect, background context, identification of goals) in representing adaptation processes in climate change studies. 相似文献
284.
While true mosaicism occurs in only 0–25 per cent of genetic amniocenteses, nearly 2–5 per cent of amniotic fluid cell cultures contain a second cell line. In the common practice of prenatal diagnosis, an aberrant cell line confined to a single colony is usually disregarded. We present a case of mosaic trisomy 14 which was not detected on initial chromosome analysis. At birth, multiple malformations were apparent. Newborn cytogenetic studies revealed mosaicism [46,XX/46,XX,-14,+i(14q)] with an isochromosome 14 in 37 per cent of lymphocytes. Additional cells from the initial amniotic fluid culture were analysed post-delivery and the isochromosome 14 identified in only one of 12 total colonies. This case illustrates two important lessons in prenatal diagnosis. First, amniotic fluid cell cultures may not accurately reflect the relative distribution of the normal and abnormal cell lines within a mosaic fetus. Second, while it is generally reasonable to disregard mosaicism confined to a single colony, this policy will, on rare occasion, result in diagnostic error. This should be taken into consideration, particularly when dealing with autosomal trisomies potentially compatible with livebirth. 相似文献
285.
Prenatal diagnosis of trisomy 20 mosaicism was made in two pregnancies by chromosome analysis of cultured amniotic fluid cells. In both cases, the pregnancy continued to term and a healthy male infant was delivered. Regular assessments up to the age of 6-5 years revealed normal physical and intellectual development in both children. 相似文献
286.
Citrullinaemia was presumed to be excluded in a fetus at risk by the direct assay of argininosuccinate synthetase in chorionic villi. The diagnosis was confirmed after amniocentesis by normal argininosuccinate synthetase activity in the cultured amniotic fluid cells and by a normal citrulline concentration in the amniotic fluid. The prediction of a normal fetus was confirmed at term by the birth of a non-citrullinaemic boy. 相似文献
287.
Pregnancies with fetal trisomy 21 have been associated with low amniotic fluid alpha-fetoprotein levels (AFAFP). This observation led to the suggestion that low AFAFP levels be used as a criterion for completion of a chromosomal analysis in patients who are not otherwise at increased risk for a fetal chromosome abnormality and in whom karyotyping might not have been completed for economic reasons. In order to assess the usefulness of such criteria, we reviewed the AFAFP levels of 90 cases of fetal trisomy 21, 23 cases of trisomy 18, and 10 cases of trisomy 13. These were compared with 2400 control samples with normal chromosome constitution. AFAFP levels were generally lower in pregnancies with trisomy 21, showing a median value of 0·72 MoM. However, 40 per cent of the trisomy 21 samples had AFAFP values greater than 0·8 MoM and 20 per cent were over 1·0 MoM. These data imply that over 50 per cent of Down syndrome cases might have been missed using a cut-off level of 0·70 MoM for completion of chromosome analysis. Using a higher cut-off level will leave only a small percentage of samples unkaryotyped. The distribution of AFP levels in trisomy 13 and 18 is no different from controls; we therefore believe that fetal karyotyping should be completed in every amniotic fluid sample obtained. 相似文献
288.
289.
Manganese-oxidizing fungi and bacteria 总被引:1,自引:0,他引:1
The Science of Nature - 相似文献
290.