全文获取类型
收费全文 | 810篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
安全科学 | 11篇 |
废物处理 | 31篇 |
环保管理 | 60篇 |
综合类 | 183篇 |
基础理论 | 167篇 |
污染及防治 | 254篇 |
评价与监测 | 62篇 |
社会与环境 | 47篇 |
灾害及防治 | 5篇 |
出版年
2023年 | 10篇 |
2022年 | 32篇 |
2021年 | 19篇 |
2020年 | 9篇 |
2019年 | 14篇 |
2018年 | 29篇 |
2017年 | 32篇 |
2016年 | 49篇 |
2015年 | 18篇 |
2014年 | 49篇 |
2013年 | 59篇 |
2012年 | 37篇 |
2011年 | 67篇 |
2010年 | 34篇 |
2009年 | 31篇 |
2008年 | 44篇 |
2007年 | 43篇 |
2006年 | 39篇 |
2005年 | 28篇 |
2004年 | 31篇 |
2003年 | 18篇 |
2002年 | 19篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1983年 | 2篇 |
1979年 | 2篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1964年 | 5篇 |
1963年 | 4篇 |
1962年 | 2篇 |
1961年 | 4篇 |
1960年 | 5篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1957年 | 5篇 |
1942年 | 2篇 |
1941年 | 2篇 |
排序方式: 共有820条查询结果,搜索用时 343 毫秒
571.
572.
Kari Hiltunen Jukka V. SeppÄlÄ Merja ItÄvaara Mika HÄrkönen 《Journal of Polymers and the Environment》1997,5(3):167-173
The biodegradability of lactic acid based poly(ester-urethanes) was studied using the headspace test method, which was performed
at several elevated temperatures. The poly(ester-urethanes) were prepared using a straight two-step lactic acid polymerization
process. The lactic acid is first condensation polymerized to a low molecular weight hydroxyl-terminated telechelic prepolymer
and then the molecular weight is increased with a chain extender such as diisocyanate. In the biodegradation studies the effect
of different stereostructures (different amounts of D-units in the polymer chain), the length of ester units, and the effect
of crosslinking on the biodegradation rate were studied. The results indicate that poly(ester-urethanes) do not biodegrade
at 25‡C, but at elevated temperatures they biodegrade well. The different stereostructures and crosslinking have a strong
influence on the biodegradation rate. The length of ester units in the polymer chain also affects the biodegradation rate,
but much less than crosslinking and stereostructure. 相似文献
573.
574.
575.
A remarkable congruence among areas of endemism, panbiogeographic nodes, and refugia in western North America, Japan, south-western China, Tasmania, and New Caledonia indicates that these areas deserve special status for conservation. Here we propose that areas identified by different biogeographic methods are significant candidates for designation as hotspots. 相似文献
576.
577.
578.
Chorionic villus biopsy specimens were studied electron microscopically in six pregnancies at risk of the infantile type of neuronal ceroid lipofuscinosis (INCL). The biopsy was performed in all cases in the first trimester of pregnancy (8–10 gestation weeks) by the transcervical route. In one case, the biopsy was repeated at 17 weeks by the transabdominal procedure. In two pregnancies, the endothelial cells and, to a lesser extent, the mesenchymal cells of the chorionic villi contained unit membrane-bound inclusions typical of INCL. In both cases, the pregnancy was terminated and in one of them identical inclusions were found in the brains and kidneys of the fetus at 20 weeks of gestational age. The children from the remaining four pregnancies are healthy and have shown no signs of the disease. 相似文献
579.
Ilkka Kaitila M.D. Pirkko Ämmälä Olavi Karjalainen Sirkka Liukkonen Juhani Rapola 《黑龙江环境通报》1983,3(3):237-244
Diastrophic dysplasia, an autosomal recessive disorder, results in severe short-limbed dwarfism, progressive spinal and joint problems, and secondary psychosocial disability. The results of treatments are unsatisfactory. Four pregnant mothers at risk for an affected fetus were studied with an ultrasound scanner at 16 and 19 weeks of gestation. Each mother had a previous child with diastrophic dysplasia. The biparietal distance and the length of the long bones of the extremities were normal in three fetuses, whereas in one fetus there was a 30 per cent shortening of all long bones. The biparietal distance corresponded with the gestational age in all fetuses. In one fetus, diastrophic dysplasia was confirmed by fetoscopy and fetal radiograph at 19 weeks of gestation after the parents had decided to terminate the pregnancy. The skeletal radiograph and autopsy findings of the fetus verified the diagnosis. All other mothers were followed with repeated ultrasound examinations, and they delivered healthy babies. The retrospective follow-up of the four previous pregnancies and of the present one with affected fetuses disclosed that two mothers had had vaginal bleeding, two lymphedema, one abdominal pains, and one mother had had polyhydramnios. These complications were, however, mild and transient, and they could not be regarded as specific for pregnancies with affected fetuses. 相似文献
580.