全文获取类型
收费全文 | 3533篇 |
免费 | 60篇 |
国内免费 | 33篇 |
专业分类
安全科学 | 203篇 |
废物处理 | 116篇 |
环保管理 | 945篇 |
综合类 | 323篇 |
基础理论 | 864篇 |
环境理论 | 7篇 |
污染及防治 | 784篇 |
评价与监测 | 224篇 |
社会与环境 | 130篇 |
灾害及防治 | 30篇 |
出版年
2023年 | 14篇 |
2022年 | 23篇 |
2021年 | 27篇 |
2020年 | 26篇 |
2019年 | 35篇 |
2018年 | 43篇 |
2017年 | 64篇 |
2016年 | 83篇 |
2015年 | 72篇 |
2014年 | 75篇 |
2013年 | 446篇 |
2012年 | 132篇 |
2011年 | 175篇 |
2010年 | 117篇 |
2009年 | 132篇 |
2008年 | 156篇 |
2007年 | 194篇 |
2006年 | 136篇 |
2005年 | 118篇 |
2004年 | 124篇 |
2003年 | 127篇 |
2002年 | 108篇 |
2001年 | 63篇 |
2000年 | 78篇 |
1999年 | 49篇 |
1998年 | 56篇 |
1997年 | 44篇 |
1996年 | 61篇 |
1995年 | 57篇 |
1994年 | 64篇 |
1993年 | 52篇 |
1992年 | 47篇 |
1991年 | 39篇 |
1990年 | 38篇 |
1989年 | 31篇 |
1988年 | 40篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 37篇 |
1982年 | 48篇 |
1981年 | 47篇 |
1980年 | 25篇 |
1979年 | 28篇 |
1978年 | 25篇 |
1977年 | 29篇 |
1976年 | 13篇 |
1974年 | 10篇 |
1972年 | 11篇 |
排序方式: 共有3626条查询结果,搜索用时 343 毫秒
391.
Robert Wallerstein Sonya Misra R. Bryce Dugar Monika Alem Ronit Mazzoni Matthew J. Garabedian 《黑龙江环境通报》2015,35(9):841-847
Genetic counseling for prenatal diagnosis of autosomal trisomy is complex because of the uncertainty of outcome, which is important for management decisions. Compilation of cases of prenatally diagnosed autosomal trisomies in amniocytes has been done previously in an attempt to elucidate the clinical phenotype of these pregnancies. It has been greater than a decade since these studies were completed. To update this work, we reviewed cases reported in the literature since that time. These cases are correlated with the prior reports to increase knowledge about outcomes and to hopefully improve the data available for genetic counseling. The risk of abnormal outcome can be summarized as: very high risk (>60%) for 47,+2/46; 47,+9/46; 47,+16/46; 47,+20/46; and 47,+22/46; high risk (40–59%) for 47,+5/46; 47,+14/46; and 47,+15/46; moderately high risk (20–39%) for 47,+7/46 47,+12/46; and 47,+17/46; moderate risk (up to 19%) for 47,+6/46 and 47,+8/46, and none were low risk. 47,+6/46 was originally indeterminate, 47,+7/46 was originally moderate risk, 47,+9/46 was originally high risk, and 47,+17/46 was originally low risk. © 2015 John Wiley & Sons, Ltd. 相似文献
392.
Robert E. Mace Roberto Anaya 《Journal of the American Water Resources Association》2004,40(4):1099-1100
393.
Attaining recycling goals of 25 to 50% over the next few years will require substantial recycling of residential wastes. A combined program of curbside recycling of conventional post-consumer materials and collection and composting of both leaves and grass will yield a composite diversion rate of 12 to 21% by weight. But in many communities, particularly in the west central and south central states of the American heartland, implementation of such programs will result in a net increase in solid waste management costs. Case studies of four communities in Oklahoma are used to estimate the potential increase in first-year net costs that would result from implementing a combined recycling and yard waste composting program. The results are compared to survey data from Oklahoma and Florida that define the amount residents are likely to be willing to pay for the benefits of recycling. The potential to close the apparent willingness-to-pay gap through state subsidies is then assessed. Where state capital grants programs are insufficient to bridge the gap, and local officials are reluctant to impose costs that are not publicly supported, public education efforts will be needed to increase the value residents ascribe to the nonexclusive positive externalities and local nonmarket benefits of recycling. 相似文献
394.
We have evaluated the role of a rapid and radical method of amniodrainage in the treatment of severe twin–twin transfusion. The outcome of 15 patients with severe twin–twin transfusion for which a amniodrainage was performed by means of a vacuum bottle system was compared with the outcome of 15 patients with a similar condition, matched for gestational age at the time of the initial procedure and drained using a standard procedure. In the study group the amniodrainage ended when no amniotic fluid could be aspirated, whereas the women in the standard group were drained with a syringe system and the fluid was removed until the deepest amniotic fluid pool was <8 cm. At the initial procedure, the mean volume of amniotic fluid drained was significantly (p<0.05) higher (3252 vs 2153 ml) and the length of the procedure significantly (p<0.001) shorter (21 vs 41 min) in the study group than in the standard group. The mean post-procedure amniotic fluid index was significantly (p<0.001) smaller (2.9 vs 7.7 cm) after radical amniodrainage than after the standard amniodrainage. The mean number of procedures was significantly (p<0.001) lower (1.5 vs 5.6) in the study group compared to the standard group. In the study group the mean placental thickness increased significantly (p<0.001) from 9 mm before the procedure to 49 mm after, and the overall perinatal survival rate was 80% and the proportion of pregnancies with at least one survivor was 93%. The present data indicate that early, rapid and radical amniodrainage is an effective and low-cost therapy for severe twin–twin transfusion syndrome. Compared to the standard amniodrainage technique it also appears to reduce the need for multiple procedures. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
395.
396.
The measurement properties of the Rizzo, House and Lirtzman (1970) role conflict and role ambiguity scales have been debated in the research literature for several years. The criticisms are that the scales do not measure separate constructs and are contaminated by method variance. However, some researchers have presented evidence supporting the scales' continued use as independent measures. We attempted to clarify the running debate by re-examining these issues and presenting additional data, which focused on the item level of analysis. Using confirmatory factor analyses and item statistics, we show discriminant validity for the role conflict and ambiguity scales across three diverse samples of workers. We also contend that the evidence for method bias is not as strong as previously argued. 相似文献
397.
398.
399.
400.
Silvicultural guidelines are presented for the management of intermountain Douglas-fir (Pseudotsuga menziesii) stands for sawtimber production and goshawk (Accipiter gentilis) nesting habitat in the northern Rocky Mountains. Data from 14 goshawk nest stands in Douglas-fir forests on the Targhee
National Forest in Idaho (Patla 1991) were used to characterize the range of stand conditions considered suitable for goshawk
nesting. A density management regime is presented using Reineke's stand density index that includes a technical rotation designed
to produce sawlogs with a single commercial thinning. On average timber-growing sites, stands reach goshawk habitat suitability
when site height is 25 m at age 75 and provide 65 years of goshawk nesting habitat until the final harvest at age 140. Approximately
1320 m3/ha are harvested over the rotation. On higher-quality sites, rotation length declines from 140 to 85 years, of which roughly
35 years are suitable for goshawk nesting. 相似文献