全文获取类型
收费全文 | 6722篇 |
免费 | 59篇 |
国内免费 | 43篇 |
专业分类
安全科学 | 185篇 |
废物处理 | 361篇 |
环保管理 | 558篇 |
综合类 | 1101篇 |
基础理论 | 1572篇 |
环境理论 | 2篇 |
污染及防治 | 1675篇 |
评价与监测 | 536篇 |
社会与环境 | 787篇 |
灾害及防治 | 47篇 |
出版年
2023年 | 52篇 |
2022年 | 90篇 |
2021年 | 89篇 |
2020年 | 46篇 |
2019年 | 57篇 |
2018年 | 113篇 |
2017年 | 139篇 |
2016年 | 152篇 |
2015年 | 101篇 |
2014年 | 200篇 |
2013年 | 504篇 |
2012年 | 210篇 |
2011年 | 317篇 |
2010年 | 268篇 |
2009年 | 283篇 |
2008年 | 322篇 |
2007年 | 313篇 |
2006年 | 289篇 |
2005年 | 257篇 |
2004年 | 246篇 |
2003年 | 280篇 |
2002年 | 224篇 |
2001年 | 306篇 |
2000年 | 190篇 |
1999年 | 126篇 |
1998年 | 56篇 |
1997年 | 69篇 |
1996年 | 57篇 |
1995年 | 71篇 |
1994年 | 74篇 |
1993年 | 71篇 |
1992年 | 73篇 |
1991年 | 64篇 |
1990年 | 70篇 |
1989年 | 58篇 |
1988年 | 62篇 |
1987年 | 56篇 |
1986年 | 59篇 |
1985年 | 49篇 |
1984年 | 51篇 |
1983年 | 55篇 |
1982年 | 56篇 |
1981年 | 29篇 |
1980年 | 32篇 |
1979年 | 34篇 |
1978年 | 30篇 |
1977年 | 29篇 |
1976年 | 30篇 |
1974年 | 32篇 |
1973年 | 31篇 |
排序方式: 共有6824条查询结果,搜索用时 31 毫秒
101.
102.
介绍了喷射沉积耐热铝合金管坯经挤压变形 ,变薄旋压筒体的研制过程 ;重点论述了热旋成形筒体的工艺路线。试验探讨了耐热铝合金的旋压温度为 35 0~ 45 0℃ ,道次变薄率约为2 0 % ,累计变薄率约 5 0 % ,需中间退火 ,退火温度宜取 35 0℃。热旋结果认为 ,喷射沉积耐热粉末铝合金铸坯直接热旋成形困难 ,需经挤压比大于 4的变形致密 ,有助于热旋成形。耐热粉末铝合金挤压坯加热变薄旋压 ,应采用小压下量多道次的变形过程 ,逐渐细化晶粒组织 ,才能旋出综合性能良好的筒形件。 相似文献
103.
IntroductionBecauseofthelowefficiencyoftheelectrostaticprecipitator (ESP)forcollectingthesubmicronparticles ,theelectricalagglomerationmethodhasledtoanincreasinginterestinreducingtheemissionofthefineparticles .Manyauthorshavestudiedelectricalagglomerati… 相似文献
104.
105.
上海市大气颗粒物高浓度区污染物的源解析 总被引:37,自引:0,他引:37
应用受体模式的化学质量平衡法支9个监测点的大气颗粒物进行污染源的源解析,得出这9个监测点的各类污染源平均贡献率为建筑尘占32.1%,土壤尘占27.5%,钢铁尘占24.9%,燃煤尘占14.8%,汽车尘和燃油尘分别占0.2%和0.4%。 相似文献
106.
Three cases of unusual chromosomal mosaicism are reported for which the cytogenetic data show inconsistent findings between CVS and AC or fetal tissue, and which cannot be explained simply by non-disjunction. For case 1, in CVS the karyotype was 46,XY, whereas lymphocytes and fibroblasts revealed 69,XXY. DNA fingerprinting indicated one paternal and two maternal chromosome sets, the latter most probably due to omission of maternal meiosis II. For case 2, in CVS mos 46,XX/47,XX,+mar de novo was observed. Amniotic fluid cells had the karyotype 46,XX. The origin of the marker chromosome might be explained by at least two events of unknown order (a somatic chromosome/chromatid deletion and non-disjunction of the homologous chromosome). In case 3 (CVS: mos 46,XY/46,XY,19q+ de novo; amniotic fluid cells, lymphocytes, and fibroblasts: 46,XY), the surplus of chromosome material in 19q+ might be explained on the basis of a somatic translocation. The idea of a chimera is less convincing, as the mosaic finding is restricted to one tissue. Furthermore, there was no hint of a vanishing twin. Hitherto, no case of structural chromosome mosaicism in CVS has been reconfirmed in fetal tissues. 相似文献
107.
108.
109.
The Henze precipitate, a peculiar blue-green microparticulate obtained by lysis of the blood cells of the ascidian Phallusia mammillata (Protochordata), was investigated with atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray microanalysis. The precipitate was collected from the Henze solution, an unstable red-brown product obtained by treating blood with distilled water, whose degradation yields a characteristic blue-green product. The microparticulates measured 50–100 µm in diameter and appeared irregular in shape. SEM examination showed smooth, roughly round boundaries. The microparticulate surface examined with AFM appeared as an irregular matrix formed by 70–320-nm-wide mammillate composites, including and embedding small (500–800 nm wide) crystal-like multilayered formations. X- ray analysis showed that the elements present in these same precipitates were mainly C, Si, Al and O. The microparticulate composition appeared close to those of natural waxes or lacquers, embedding amorphous silicates and/or other Si–Al components. The unusual occurrence of Si in ascidian blood and its role are discussed. 相似文献
110.
Circulating placental [human chorionic gonadotrophin (hCG), Schwangerschafts protein 1 (SP1), pregnancy-associated plasma protein A (PAPP-A), decidual (pregnancy protein) 12 (PP12), and fetal alphafetoprotein (AFP)] proteins were measured immediately before and within 1 h in 18 women undergoing diagnostic chorionic villus sampling (CVS) in the first trimester. An elevation of serum AFP levels was consistently seen, while fluctuations in excess of 10 per cent of the pre-CVS levels of SP1 and PP12 were seen in the majority of patients. Fluctuations in hCG and PAPP-A were consistently less than 10 per cent of pre-CVS values. Post-CVS changes in levels were not apparently associated with any feature of the technique, the pregnancy, or its outcome (one missed abortion). As feto-maternal haemorrhage is a common event, anti-D should be offered to rhesus-negative women undergoing CVS. In the prediction of subsequent miscarriage, only hCG and PAPP-A measurements should be considered. 相似文献