全文获取类型
收费全文 | 30272篇 |
免费 | 302篇 |
国内免费 | 264篇 |
专业分类
安全科学 | 836篇 |
废物处理 | 1252篇 |
环保管理 | 3962篇 |
综合类 | 4503篇 |
基础理论 | 8240篇 |
环境理论 | 8篇 |
污染及防治 | 8244篇 |
评价与监测 | 1974篇 |
社会与环境 | 1617篇 |
灾害及防治 | 202篇 |
出版年
2022年 | 232篇 |
2021年 | 237篇 |
2020年 | 184篇 |
2019年 | 225篇 |
2018年 | 401篇 |
2017年 | 438篇 |
2016年 | 644篇 |
2015年 | 540篇 |
2014年 | 846篇 |
2013年 | 2501篇 |
2012年 | 984篇 |
2011年 | 1307篇 |
2010年 | 1083篇 |
2009年 | 1150篇 |
2008年 | 1313篇 |
2007年 | 1427篇 |
2006年 | 1217篇 |
2005年 | 1026篇 |
2004年 | 1052篇 |
2003年 | 997篇 |
2002年 | 985篇 |
2001年 | 1237篇 |
2000年 | 892篇 |
1999年 | 508篇 |
1998年 | 371篇 |
1997年 | 391篇 |
1996年 | 434篇 |
1995年 | 459篇 |
1994年 | 433篇 |
1993年 | 366篇 |
1992年 | 359篇 |
1991年 | 339篇 |
1990年 | 368篇 |
1989年 | 345篇 |
1988年 | 303篇 |
1987年 | 302篇 |
1986年 | 275篇 |
1985年 | 280篇 |
1984年 | 294篇 |
1983年 | 282篇 |
1982年 | 269篇 |
1981年 | 267篇 |
1980年 | 231篇 |
1979年 | 249篇 |
1978年 | 198篇 |
1977年 | 198篇 |
1976年 | 153篇 |
1975年 | 169篇 |
1973年 | 180篇 |
1972年 | 164篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
Forty-two open neural tube defects (NTDs) were identified in our series of 7440 amniocenteses tested between 11 and 15 weeks of gestation. Using a cut-off of ≥2.0 MOM, the detection rate for open NTDs was 95 per cent; 100 per cent each for anencephaly and spina bifida; and 78 per cent for encephalocele. Two encephaloceles had AFP levels less than 2.0 MOM and negative AChEs. Thirty-four (81 per cent) of these NTDs were tested between 13 and 15 weeks and 8 (19 per cent) before 13 weeks. There were 0.6 per cent false positives by AFP (excluding serious abnormalities and fetal death) and 0.1 per cent after AChE. The likelihood of an open NTD after an elevated AFP (≥2.0 MOM) was 24 and 77 per cent for any serious abnormality. These results, when combined with an earlier study, indicate that amniotic fluid AFP appears to be as sensitive a test for open NTDs between 13 and 15 weeks as between 16 and 20 weeks. Additional experience is necessary to determine this before 13 weeks. 相似文献
962.
Tzipora C. Falik-Borenstein MD Stuart A. Holmes Zvi Borochowitz Abi Levin A. Rosenmann Richard A. Spritz 《黑龙江环境通报》1995,15(4):345-349
We describe molecular prenatal diagnosis and carrier detection of tyrosinase-negative oculocutaneous albinism (OCA1A) in two families. In one family, we carried out DNA-based prenatal diagnosis of OCA1A. In the other family, mutation analysis and carrier detection obviated the need for prenatal diagnosis. Molecular analysis is safer and probably more accurate than fetoscopy and fetal scalp biopsy, and should become the method of first choice for prenatal diagnosis of OCA1. 相似文献
963.
ISO 14001 certification and financial performance: selection-effect versus treatment-effect 总被引:1,自引:0,他引:1
Iñaki Heras-Saizarbitoria José F. Molina-Azorín Gavin P.M. Dick 《Journal of Cleaner Production》2011,19(1):1-12
The paper explores the bi-directional relationship between ISO 14001 certification and financial performance with the aim of shedding light on whether better performance is due to the beneficial effects of ISO 14001 or due to selection-effects where better performance precedes accreditation. The study uses a five year longitudinal analysis to compare the financial performance of firms in Spain before and after certification. The results of a multivariate panel data analysis find that firms with better than average performance have a greater propensity to pursue accreditation but there is no evidence that improvements in performance follow certification. This suggests that the inference that environmental variables cause improved financial performance may be unwise in research studies that can only measure association. 相似文献
964.
J. García-Ten E. Monfort M.P. Gómez-Tena V. Sanz 《Journal of Cleaner Production》2011,19(9-10):1110-1116
The manufacture of traditional ceramic products (ceramic tiles, roof tiles, and bricks) is often associated with the emission of F, Cl, and S compounds during the firing stage. According to the literature, fluorine emissions can be reduced by adding CaCO3 to the raw materials mixture used in fabricating these products. However, data available to the authors indicate that this procedure, which has been successfully applied in manufacturing structural ceramics (roof tiles and bricks), is ineffective in ceramic tile manufacture and modifies tile end properties.This paper examines the possibility of reducing such emissions by applying coatings of alkaline-earth carbonates on to the ceramic tile bottom surface to retain the acid compounds emitted during tile firing. The effectiveness of MgCO3, CaCO3, SrCO3, and BaCO3 coatings for retaining these acid emissions was studied, using the evolved gas analysis (EGA) technique with a TG-DSC-FTIR-QM instrument.The SrCO3 coating was found to provide the greatest retention, showing that SO2 and HCl were retained more efficiently than HF. The presence of fluorides, chlorides, and sulphates of Ca, Sr, and Ba was verified in the respective fired coatings, confirming the existence of chemical reactions between the emitted acid compounds and the coating materials at high temperature. 相似文献
965.
966.
967.
Introduction
This study examined the impact of the British Petroleum (BP) Baker Panel Report, reviewing the March 2005 BP-Texas City explosion, on the field of process safety.Method
Three hundred eighty-four subscribers of a process safety listserv responded to a survey two years after the BP Baker Report was published.Results
Results revealed respondents in the field of process safety are familiar with the BP Baker Report, feel it is important to the future safety of chemical processing, and believe that the findings are generalizable to other plants beyond BP-Texas City. Respondents indicated that few organizations have administered the publicly available BP Process Safety Culture Survey. Our results also showed that perceptions of contractors varied depending on whether respondents were part of processing organizations (internal perspective) or government or consulting agencies (external perspective).Conclusions
This research provides some insight into the beliefs of chemical processing personnel regarding the transportability and generalizability of lessons learned from one organization to another.Impact on Industry
This study has implications for both organizational scientists and engineers in that it reveals perceptions about the primary mechanism used to share lessons learned within one industry about one major catastrophe (i.e., investigation reports). This study provides preliminary information about the perceived impact of a report such as this one. 相似文献968.
Introduction
Falls in older Australians are a significant public health issue with one in three older people falling one or more times each year.Method
Many fall prevention randomized controlled trials have been conducted in Australia as well as across the world.Results
The findings of these studies now constitute a substantial evidence base that can provide direction for health and lifestyle interventions for preventing falls in older people. This research evidence has contributed to health policy in Australia to some extent, but is yet to be widely implemented into practice. This opinion piece overviews previous policy initiatives and describes a new Partnership research program funded by the Australian National Health and Medical Research Council (NHMRC), which seeks to further influence health policy and address the ongoing research-practice gap. 相似文献969.
970.