全文获取类型
收费全文 | 34929篇 |
免费 | 366篇 |
国内免费 | 273篇 |
专业分类
安全科学 | 974篇 |
废物处理 | 1457篇 |
环保管理 | 4805篇 |
综合类 | 5380篇 |
基础理论 | 9588篇 |
环境理论 | 15篇 |
污染及防治 | 9401篇 |
评价与监测 | 2181篇 |
社会与环境 | 1523篇 |
灾害及防治 | 244篇 |
出版年
2022年 | 224篇 |
2021年 | 267篇 |
2019年 | 250篇 |
2018年 | 423篇 |
2017年 | 453篇 |
2016年 | 743篇 |
2015年 | 579篇 |
2014年 | 873篇 |
2013年 | 2847篇 |
2012年 | 1058篇 |
2011年 | 1445篇 |
2010年 | 1158篇 |
2009年 | 1239篇 |
2008年 | 1483篇 |
2007年 | 1586篇 |
2006年 | 1393篇 |
2005年 | 1160篇 |
2004年 | 1170篇 |
2003年 | 1107篇 |
2002年 | 1079篇 |
2001年 | 1347篇 |
2000年 | 1008篇 |
1999年 | 569篇 |
1998年 | 444篇 |
1997年 | 449篇 |
1996年 | 493篇 |
1995年 | 524篇 |
1994年 | 504篇 |
1993年 | 464篇 |
1992年 | 432篇 |
1991年 | 419篇 |
1990年 | 448篇 |
1989年 | 419篇 |
1988年 | 390篇 |
1987年 | 369篇 |
1986年 | 330篇 |
1985年 | 315篇 |
1984年 | 384篇 |
1983年 | 345篇 |
1982年 | 390篇 |
1981年 | 361篇 |
1980年 | 297篇 |
1979年 | 320篇 |
1978年 | 262篇 |
1977年 | 231篇 |
1976年 | 209篇 |
1975年 | 213篇 |
1974年 | 210篇 |
1973年 | 224篇 |
1972年 | 230篇 |
排序方式: 共有10000条查询结果,搜索用时 177 毫秒
421.
422.
Diana W. Bianchi MD Gretchen K. Zickwolf Melissa C. Yih Alan F. Flint Ossie H. Geifman Marlena S. Erikson John M. Williams 《黑龙江环境通报》1993,13(4):293-300
Fetal nucleated erythrocytes (NRBC) in maternal blood are a non-invasive source of fetal DNA for prenatal genetic screening. We compared the effectiveness of three monoclonal antibodies for the separation of fetal cells from maternal blood by flow sorting. Mononuclear blood cells from 49 healthy pregnant women were incubated with antibody to CD 71, CD 36, and/or glycophorin A (GPA), employed singly or in combination with each other. These monoclonal antibodies recognize surface antigens on haematopoietic precursor cells. Successful isolation of fetal cells was defined as detection of Y chromosomal sequences in maternal blood from women carrying male fetuses, with absence of Y sequences when female fetuses were carried. Thus, gender prediction accuracy was used as a measure of fetal cell separation. Using anti-CD 71 to isolate fetal cells, gender prediction was 57 per cent correct; with anti-CD 36, it was 88 per cent correct. Anti-GPA, an erythrocyte-specific antigen, used alone or in combination with anti-CD 71 or 36, improved gender prediction to 100 per cent. We conclude that antibody to GPA improves the retrieval of fetal NRBC from maternal blood, permitting genetic analysis by the polymerase chain reaction. 相似文献
423.
Lee P. Shulman MD Patricia L. Gordon Donald S. Emerson R. Sidney Wilroy Sherman Elias 《黑龙江环境通报》1993,13(5):403-409
We describe the prenatal diagnosis of isolated bilateral fetal microphthalmia in a woman at increased risk of having a fetus with microphthalmia. Ultrasound examinations at 161 and 19-5 weeks' gestation demonstrated bilateral fetal microphthalmia with no other associated structural defects. The patient elected to terminate her pregnancy at 19.5 weeks. Pathological evaluation of the products of conception obtained by dilation and evacuation confirmed the prenatal diagnosis of isolated bilateral fetal microphthalmia. 相似文献
424.
C. A. Dell'Agnola V. Tomaselli E. Teruzzi B. Tadini A. G. Coran Surgeon-in-Chief 《黑龙江环境通报》1993,13(7):629-632
The impact of prenatal sonographic diagnosis of oesophageal and gastrointestinal obstructions has been analysed over a 10-year period. Three groups of patients were evaluated. The first group consisted of 46 newborns with abnormal prenatal sonogratns, 41 of which were confirmed to have intestinal obstruction postnatally. The second group consisted of 17 neonates with normal prenatal sonograms who had intestinal obstruction postnatally. The third group included 56 newborns who did not undergo a prenatal sonogram but who had intestinal obstruction confirmed at surgery. Polyhydramnios without the appearance of a stomach on ultrasound was diagnostic of pure oesophageal atresia. Polyhydramnios with intestinal dilation was diagnostic of intestinal obstruction. Although surgery was performed earlier in the infants diagnosed prenatally with ultrasound, mortality was no less than in the group that did not undergo a prenatal sonogram, probably because of the high incidence of associated anomalies. 相似文献
425.
Massimo Cordone Mario Lituania Giancarlo Bocchino Ubaldo Passamonti Paolo Tomà Gianni Camera 《黑龙江环境通报》1993,13(5):395-401
Prenatal diagnosis of heterozygous achondroplasia at 25 weeks is described. First-level fetal ultrasonography demonstrated short long bones of the lower limbs. Second-level examination showed a large head; shortened femur, fibula, and tibia; a ‘trident’-shaped hand; and an abnormal facial profile. 相似文献
426.
In the case-control study of 118 women with autosomal trisomy identified at prenatal diagnosis and their 442 karyotypically normal matched controls, we found that there was no overall association between risk of trisomy and the presence of vaginal bleeding during pregnancy. However, a lengthy duration of bleeding appears to predict increased risk of trisorny. 相似文献
427.
428.
Masera Omar R. Cerón Alma Delia Ordóñez Antonio 《Mitigation and Adaptation Strategies for Global Change》2001,6(3-4):291-312
We examine carbon (C) reference and mitigation scenarios for the Mexicanforest sector between the year 2000 and 2030. Estimates are presentedseparately for the period 2008–2012.Future C emissions and capture are estimated using a simulation modelthat: a) allocates the country land use/land cover classes among differentfuture uses and categories using demand-based scenarios for forestryproducts; b) estimates the total C densities associated to each land usecategory, and c) determines the net carbon implications of the process ofland use/cover change according to the different scenarios.The options analyzed include both afforestation/reforestation, such ascommercial, bionenergy and restoration plantations, and agroforestrysystems, and forest conservation, through the sustainable management ofnative forests and forest protection.The total mitigation potential, estimated as the difference between the totallong-term carbon stock in the reference and the mitigation scenario reaches300 × 106 Mg C in the year 2012 and increases to 1,382 × 106 Mg C in 2030. The average net sequestration in the 30 year period is 46 × 106 Mg C yr-1, or 12.5 × 106 Mg C yr-1 within the period 2008 to 2012. The costs of selected mitigation options range from 0.7–3.5 Mg C-1 to 35 Mg C-1. Some options are cost effective. 相似文献
429.
430.
The lessons of history indicate that mismanagement of natural resources and the environment often leads to potentially adverse consequences.The increasing interest in economic development,particularly in the developing countries of the world coupled with increasing population pressures and the globalization of economic activity is placing noticeable stresses on the ultimate sustainability of both human and environmental systems.Sustainable development is not a new concept.It has been an area of concern for different elements of society for some time.Yet efforts to understand the implications of sustainable development have not,until recently,been formalized.We have focused singularly on economic development and environmental quality as if they were mutually exclusive.This paper focuses on the concept of concurrency as both a conceptual framework and practicable method of understanding and implementing the ecology and economy of sustainability. 相似文献