全文获取类型
收费全文 | 1257篇 |
免费 | 118篇 |
国内免费 | 693篇 |
专业分类
安全科学 | 189篇 |
废物处理 | 98篇 |
环保管理 | 88篇 |
综合类 | 1071篇 |
基础理论 | 174篇 |
污染及防治 | 363篇 |
评价与监测 | 56篇 |
社会与环境 | 10篇 |
灾害及防治 | 19篇 |
出版年
2024年 | 5篇 |
2023年 | 34篇 |
2022年 | 79篇 |
2021年 | 75篇 |
2020年 | 69篇 |
2019年 | 62篇 |
2018年 | 66篇 |
2017年 | 90篇 |
2016年 | 83篇 |
2015年 | 100篇 |
2014年 | 134篇 |
2013年 | 122篇 |
2012年 | 130篇 |
2011年 | 110篇 |
2010年 | 94篇 |
2009年 | 100篇 |
2008年 | 66篇 |
2007年 | 106篇 |
2006年 | 100篇 |
2005年 | 58篇 |
2004年 | 44篇 |
2003年 | 60篇 |
2002年 | 45篇 |
2001年 | 32篇 |
2000年 | 27篇 |
1999年 | 27篇 |
1998年 | 22篇 |
1997年 | 17篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 11篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有2068条查询结果,搜索用时 31 毫秒
871.
872.
对钢铁厂铁鳞、铁红的基本物化性能和还原性能进行了研究。结果表明:粒度较粗、全铁较高铁鳞的还原性较好,适于作为优质海绵铁的原料。粒度极细、全铁高且杂质含量很低的铁红还原性也较好,适于作还原铁粉生产的原料。 相似文献
873.
874.
钢渣处置工艺的清洁生产研究与实施 总被引:1,自引:0,他引:1
该课题研究了用水淬法和蒸汽法相结合的技术消除钢渣中的游离氧化钙;用传统的破碎磁选与高精度的强磁选相结合,以独创的递进除铁技术使钢渣中的含铁量由18%降至1%;用专项技术改制的管式磨、活化环,蒸汽熟化,递进式除铁,o-sepa选粉,高频振动粉磨,PPC集料器组成钢渣微粉清洁生产工艺.结果表明该工艺在国内尚属首例,具有较好的推广应用价值. 相似文献
875.
876.
A prospective study of maternal serum alphafetoprotein (α-FP) screening of 9838 women in an area with low prevalence of neural tube defects and predominance of anencephalics revealed that an intervention point of single serum α-FP level above 2·8 times the median was appropriate for this population. Ninety per cent of anencephalics and all fetuses with anterior abdominal wall defects were detected. There was no spina bifida among the population screened. Two per cent of the population screened had serum α-FP level above this cut-off level. Thirty-two per cent of twin pregnancies, 7 per cent of small-for-gestational age infants and 9 per cent of pregnancies which ended in either abortion or perinatal death in the population screened also had one serum α-FP level above this intervention point. The false positive rate was 66 per cent. This false positive rate was only reduced to 63 per cent if instead of one, two serum α-FP level above this intervention point was considered abnormal. Using this strategy there was no significant reduction in the detection rate of fetal anomalies and other pregnancy complications. Because of the predominance of anencephalics in this population the diagnosis of fetal anomaly in women with abnormal serum a-FP level was made by ultrasound examination alone. The reason amniocentesis was not performed in these patients was to avoid unnecessary loss of normal pregnancies which may result from this procedure. 相似文献
877.
Susan J. Gross MD Owen P. Phillips Lee P. Shulman N. Lawrette Bright Jeffrey S. Dungan Joe Leigh Simpson Sherman Elias 《黑龙江环境通报》1994,14(7):609-613
An association between various abnormal mid-trimester maternal serum analyte values and adverse perinatal outcome has been reported. From an original sample of 14 857 women, we observed five women who were ‘screen-positive’ for both neural tube defects [maternal serum alpha-fetoprotein (MSAFP) ≥2·5 multiples of the median] and Down syndrome [risk ≥1/274 using MSAFP, maternal serum unconjugated oestriol (MSuE3), maternal serum human chorionic gonadotropin (MShCG), and maternal age]. The four patients who elected to undergo amniocentesis all demonstrated both normal karyotype and normal amniotic fluid AFP levels. All five cases were associated with intrauterine growth retardation (IUGR) and abnormal pregnancy outcomes. Two cases exhibiting severe IUGR on ultrasound examination were terminated at 19·1 and 21·2 weeks, respectively; the former also exhibited fetal calcifications and positive maternal serology for toxoplasmosis. In another case, fetal demise occurred at 36 weeks' gestation in a patient who had been treated for syphilis in the second trimester. Neither infection was confirmed in fetal tissue studies. Though resulting in live births, the remaining two cases required operative deliveries; emergency Caesarean sections for fetal distress were performed at 38 and 32 weeks, respectively, the latter case being associated with severe pre-eclampsia. We conclude that elevated mid-trimester MSAFP levels concurrent with maternal serum analyte values associated with increased risk for fetal Down syndrome may presage a poor perinatal outcome, particularly IUGR and possibly congenital infection. 相似文献
878.
The glial fibrillary acidic protein (GFAP) is the subunit protein of intermediate filaments in astrocytes and closely related cell types. By means of an enzyme immunoassay we have determined the concentration of GFAP in amniotic fluids from normal pregnancies and from pregnancies complicated by various fetal malformations. The group of 20 cases of fetal anencephaly had a significantly higher mean amniotic fluid GFAP concentration (115 μg/1±133.6 (S.D.), range 6–378 μg/1) than the control group of 117 normal pregnancies (13 μg/1k±5.5 (S.D.), range 0–31 μg/1), (P<0.001). Two cases of fetal encephalocele likewise had very high amniotic fluid GFAP concentrations. None of the other cases of fetal malformations investigated, including 12 cases of spina bifida, had increased amniotic fluid GFAP concentrations. We conclude that determination of the amniotic fluid GFAP concentration may give additional information in the prenatal diagnosis of fetal nervous system malformations. 相似文献
879.
Wang Hong liang Department of Biology Lanzhou University Lanzhou China Zhao Zhen jie Li Fa shen Department of Physics Lanzhou University Lanzhou China 《环境科学学报(英文版)》1998,(4)
1IntroductionAlthoughfiltermethodisverytimeconsuming,ithasbeenemployedintheinvestigationsofaerosolsforalongtime(Kopcewicz,19... 相似文献
880.
用自组装的膜吸收器试验研究了不同操作条件下的烟气脱硫特性。实验结果表明,脱硫过程传质阻力主要集中在气相和膜上,利用螺旋管技术可以强化气相的传质。 相似文献