全文获取类型
收费全文 | 2055篇 |
免费 | 245篇 |
国内免费 | 105篇 |
专业分类
安全科学 | 38篇 |
废物处理 | 24篇 |
环保管理 | 471篇 |
综合类 | 477篇 |
基础理论 | 1089篇 |
环境理论 | 3篇 |
污染及防治 | 105篇 |
评价与监测 | 55篇 |
社会与环境 | 136篇 |
灾害及防治 | 7篇 |
出版年
2023年 | 66篇 |
2022年 | 58篇 |
2021年 | 88篇 |
2020年 | 86篇 |
2019年 | 77篇 |
2018年 | 76篇 |
2017年 | 86篇 |
2016年 | 97篇 |
2015年 | 111篇 |
2014年 | 103篇 |
2013年 | 132篇 |
2012年 | 89篇 |
2011年 | 119篇 |
2010年 | 129篇 |
2009年 | 134篇 |
2008年 | 116篇 |
2007年 | 143篇 |
2006年 | 97篇 |
2005年 | 79篇 |
2004年 | 77篇 |
2003年 | 40篇 |
2002年 | 39篇 |
2001年 | 46篇 |
2000年 | 35篇 |
1999年 | 26篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 21篇 |
1995年 | 27篇 |
1994年 | 25篇 |
1993年 | 24篇 |
1992年 | 21篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 4篇 |
1968年 | 1篇 |
排序方式: 共有2405条查询结果,搜索用时 46 毫秒
31.
Rapid detection of numerical aberrations of chromosomes 13, 18 and 21 in chorionic mesenchymal cells
We have devised and evaluated a rapid screening method for the detection of numerical aberrations of chromosomes13, 18 and 21 in chorionic villus cells. We used non-radioactive in situ hybridization (ISH) with three chromosome-specific probes on overnight-attached mesenchymal cells from chorionic villi. A blind study was performed of 47 karyotypically normal samples, one triploid sample, two samples trisomic for chromosome 21, and two samples from a fetus with putative mosaicism (46/47, +21). All samples were hybridized with the chromosome 18- and 21-specific probes. Thirty samples were additionally hybridized with the chromosome 13-specific probe. The test could be completed within 3-4 days of sampling. In samples disomic with respect to the probed chromosomes, an average of 2 per cent (range 0-9 per cent) had three hybridization signals. By contrast, in the samples trisomic for the probed chromosome(s), 57 per cent (chromosome 13), 51 per cent (chromosome 18), and an average of 74 per cent (55-86 per cent) (chromosome 21) of the nuclei exhibited three signals. In the putative mosaic samples, the number of nuclei with three chromosome 21-specific signals ranged from 41 to 69 per cent. We conclude that this technique rapidly and clearly distinguishes between normal and trisomic/triploid samples, and consequently may be of use in future prenatal diagnosis. 相似文献
32.
马场垣至平安高速公路水土保持方案的探讨 总被引:4,自引:0,他引:4
通过对马平高速公路沿线水土流失现状和特点的分析,对沿线公路施工区和弃土弃渣场的水土流失进行了预测,预测结果表明,本项目建设可能新增的水土流失量为934.33kt,根据预测结果和水土流失防治分区提出了具体的防治措施。 相似文献
33.
34.
典型黄土塬区不同植物措施水土保持效应分析 总被引:6,自引:2,他引:6
基于黄土高原典型黄土塬区2014-2016年的自然降雨数据及5种植被措施(乔木、灌木、撂荒、人工种草、耕地)下的坡面产流、产沙情况的观测数据,系统分析了不同植被覆盖措施下的黄土坡地水土流失对不同类型侵蚀性降雨的响应机制,结果表明:(1)降水集中于4-10月份,其中引发水土流失的侵蚀性降雨集中于7月、8月。(2)根据最大30分钟降雨强度I30及降雨总量可将侵蚀性降雨分为5种类型,其中小雨量、小雨强类型的降雨是当地发生频率最多的侵蚀性降雨类型;降雨强度最大的Ⅴ雨型降雨侵蚀力最大,降雨量最大的Ⅰ雨型降雨侵蚀力次之,而Ⅱ雨型降雨侵蚀力最低;Ⅴ雨型在观测期内产流产沙量最大。(3)5种植被措施在不同降雨类型下均有明显的水土保持效应,在不同类型降雨下不同植物措施减沙率和减流率变化规律不同。研究结果对于黄土高原地区水土保持及资源可持续利用具有重要的指导意义。 相似文献
35.
In this paper we describe the use of five-colour fluorescence in situ hybridization for prenatal diagnosis of aneuploidy using uncultured amniotic fluid cells. The analysis is based on ratio mixing of dual-labelled probes and digital imaging for the detection and visualization of five different probes specific for the five target chromosomes, 13, 18, 21, X, and Y. A retrospective blind analysis of 30 coded uncultured amniotic fluid samples correctly detected fetal sex and five trisomy 21 cases. Multicolour fluorescence in situ hybridization used in this way allows rapid and simultaneous detection of the most frequent aneuploidies. 相似文献
36.
37.
An amniocentesis was performed at 13.3 weeks' gestation for advanced maternal age. A mosaic sex chromosome pattern was found: of 50 cells examined, 34 had a 45,X karyotype. In 14 cells with a modal number of 46, a recognizable Y was substituted by a small non-fluorescent marker. C-banding identified the marker as an isodicentric in 12 cells. In two cells, the non-fluorescent marker appeared to be monocentric and looked like a non-fluorescent del (Yq), but could have been an isodicentric Y with inactivation of one of the centromeres. Two cells with a modal number of 47 showed two copies of the monocentric marker. Fluorescent in situ hybridization with an alpha satellite Y-specific centromeric probe confirmed the Y-chromosome origin of the markers and allowed for more accurate prenatal diagnostic information. 相似文献
38.
Soil water characteristics in mountain poplar stand and its benefits to soil and water conservation in loess hilly region 总被引:2,自引:0,他引:2
SoilwatercharacteristicsinmountainpoplarstandanditsbenefitstosoilandwaterconservationinloesshillyregionWuQinxiao;LiuXiangdong... 相似文献
39.
矿产资源的开发利用与环境保护 总被引:8,自引:1,他引:8
作者论述了人口、资源、环境三者之间的辩证关系,提出环境保护是矿产资源开发利用的前提,不能以牺牲环境为代价来开发利用矿产资源。以此为基点,作者概述了我国矿产资源开发利用对环境的影响,以及我国矿山环境保护工作的现状,提出了加强矿产资源开发利用中环境保护的五项建议。 相似文献
40.
Geraldo Ferrer 《Resources, Conservation and Recycling》1997,19(4):221-255
The world market for tires is described to identify the current material flow from raw materials to tires and the used tire disposal problem. Then, I describe the value-adding operations in the tire production process and in the tire retreading process. Once retreading is identified as the only recovery alternative that maximizes tire utilization, I explain why heat generation is the only recovery alternative, when retreading is not technically feasible. The economic values of heat generation in electric plants and in cement kilns are discussed. The paper culminates with the case of retreading, the tire remanufacturing process and the recommendation of a simple decision rule for selecting the number of times a tire should be retreaded to maximize its utilization. 相似文献