全文获取类型
收费全文 | 27428篇 |
免费 | 620篇 |
国内免费 | 3273篇 |
专业分类
安全科学 | 1114篇 |
废物处理 | 1278篇 |
环保管理 | 3069篇 |
综合类 | 8147篇 |
基础理论 | 6144篇 |
环境理论 | 12篇 |
污染及防治 | 8079篇 |
评价与监测 | 1534篇 |
社会与环境 | 1454篇 |
灾害及防治 | 490篇 |
出版年
2023年 | 234篇 |
2022年 | 621篇 |
2021年 | 532篇 |
2020年 | 411篇 |
2019年 | 458篇 |
2018年 | 590篇 |
2017年 | 664篇 |
2016年 | 797篇 |
2015年 | 775篇 |
2014年 | 1085篇 |
2013年 | 2433篇 |
2012年 | 1262篇 |
2011年 | 1510篇 |
2010年 | 1197篇 |
2009年 | 1207篇 |
2008年 | 1386篇 |
2007年 | 1297篇 |
2006年 | 1221篇 |
2005年 | 954篇 |
2004年 | 877篇 |
2003年 | 934篇 |
2002年 | 830篇 |
2001年 | 968篇 |
2000年 | 813篇 |
1999年 | 589篇 |
1998年 | 459篇 |
1997年 | 454篇 |
1996年 | 426篇 |
1995年 | 404篇 |
1994年 | 362篇 |
1993年 | 357篇 |
1992年 | 343篇 |
1991年 | 313篇 |
1990年 | 259篇 |
1989年 | 238篇 |
1988年 | 193篇 |
1987年 | 163篇 |
1986年 | 188篇 |
1985年 | 181篇 |
1984年 | 180篇 |
1983年 | 188篇 |
1982年 | 183篇 |
1981年 | 182篇 |
1980年 | 161篇 |
1979年 | 159篇 |
1978年 | 120篇 |
1977年 | 129篇 |
1974年 | 116篇 |
1973年 | 101篇 |
1972年 | 117篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
611.
Samples of cloudwater, rainwater and ambient aerosol were collected over Maoer Mountain in the northeast of Guangxi Province in March 1988. The pH value of cloudwater ranged from 3.37 to 6.20 with a mean value of 4.34. SO42- , NO3- , NH4+, Ca2+ and H+ were the principal ionic species of cloudwater. The advance of cold fronts into Maoer Mountain appeared to lead to higher major ionic concentration and acidity than that of warm fronts. The relative acidity and concentration of NO3- of cloudwater were much greater than that of aerosol samples. With the exception of. NO3- and H+, most of the concentration of SO42- and NH4+ in cloudwater came from the nucleation scavenging of aerosol. Gaseous nitric acid and organic acid from local may be one of the important source of cloudwater acidity. Compared with other sites, Maoer Mountain can be as a clean contrast station for studying acidic precipitation in Guangdong and Guangxi provinces. 相似文献
612.
本文以大气污染监测数据的随机分析为主,阐述了如何根据统计学理论,对大量已有的环境监测数据进行随机分析,以便充分利用环境数据库资源,改善环境监测管理工作。 相似文献
613.
G. A. Hackett Dr. J. H. Smith M. T. Rebello C. T. H. Gray D. E. Rooney R. W. Beard F. E. Loeffler D. V. Coleman 《黑龙江环境通报》1991,11(5):311-315
Early arnniocentesis between 11 and 14 weeks' gestation was offered to 110 women at risk of a chromosomally abnormal fetus due to maternal age. Four were found to be unsuitable for the procedure, and 106 early amniocenteses were performed. In 102 cases, clear amniotic fluid was obtained with a single tap. There were two dry taps and two bloodstained tapis; sampling was repeated in three of these cases before 15 weeks. In the fourth case, placental biopsy was performed at 16 weeks. Thus, we were able to obtain a satisfactory sample in all but three cases(2.8 percent). Karyotyping of cells harvested from the early amniotic fluid samples was successful in all the 105 cases. Cell culture from the initial samples revealed a normal karyotype in 99 cases, two balanced translocations, two tetraploid karyotypes, and two cases of pseudomosaicism. Of the 105 pregnancies successfully sampled, there have been two losses to date (1–8 per cent). Two further patients presented with premature rupture of membranes, both pregnancies having successful outcomes. Sixty-two babies have delivered to date, with four congenital anomalies. There were no respiratory problems. Twenty-nine pregnancies are continuing without known complications, and details are not yet available on the remaining 12. The results indicate that early arnniocentesis may replace the traditional test at 15–17 weeks. 相似文献
614.
A new dimension in the prevention of birth defects will be achieved when genetic diseases can be routinely diagnosed in embryos prior to implantation. The impressions and attitudes towards preimplantation diagnosis were studied in prospective patients, women at high reproductive risk for a genetic disease. Their perspective highlighted not only the advantages and disadvantages of this new approach, but also those changes necessary in order for preimplantation diagnosis to become a useful and practical technique. The data presented are based on information obtained by a mailed questionnaire answered by 58 women. The main benefit of preimplantation diagnosis for these high-risk women would be the ability to undertake a pregnancy without having to be subjected to the physical and/or emotional trauma of elective termination. Their major concerns related to possible damage to the embryo following biopsy, the cost of the procedure, and the low success rate of completed pregnancies. Other issues to be addressed before preimplantation diagnosis could begin to compare favourably with existing forms of prenatal testing were that the methods of obtaining oocytes or embryos should be simple, well tolerated, highly efficient, and low in maternal risk, and that the genetic analysis of embryonic or extraembryonic cells should be unequivocally accurate. 相似文献
615.
616.
C. Marchese M.D. E. Savin E. Dragone F. Carozzi M. De Marchi M. Campogrande G. C. Dolfin G. Pagliano E. Viora A. Carbonara 《黑龙江环境通报》1985,5(3):221-227
Six cases of cystic hygromas detected during second trimester ultrasound examination are reported: 4 fetuses (67 per cent) had a 45, X karyotype, 1 fetus had trisomy 18, 1 fetus had a normal karyotype (46,XX) and at autopsy multiple anomalies were observed. In the latter case the family history suggested an autosomal recessive pattern of inheritance. In order to reach a definite diagnosis and give proper genetic counselling when a fetus is found to have cystic hygroma, a fetal karyotype as well as a family and reproductive history should be obtained. 相似文献
617.
In 40 pregnancies at risk for the Hurler syndrome 13 affected fetuses were detected by the demonstration of an α-L -iduronidase deficiency and an increased level of 35S-sulphate incorporation. The diagnoses were confirmed by the analysis of fetal tissues and/or cultured fetal skin fibroblasts. Microassays for α-L -iduronidase, using phenyl α-L -iduronide and more recently 4–methyl-umbelliferyl α-L -iduronide, enabled a reliable diagnosis to be made within 15 to 18 days after amniocentesis. 35S-sulphate incorporation has been a valuable adjunct in cases with a low (heterozygote) enzyme activity. 相似文献
618.
619.
620.