全文获取类型
收费全文 | 30277篇 |
免费 | 302篇 |
国内免费 | 264篇 |
专业分类
安全科学 | 836篇 |
废物处理 | 1252篇 |
环保管理 | 3963篇 |
综合类 | 4504篇 |
基础理论 | 8241篇 |
环境理论 | 8篇 |
污染及防治 | 8246篇 |
评价与监测 | 1974篇 |
社会与环境 | 1617篇 |
灾害及防治 | 202篇 |
出版年
2022年 | 232篇 |
2021年 | 237篇 |
2020年 | 184篇 |
2019年 | 225篇 |
2018年 | 401篇 |
2017年 | 438篇 |
2016年 | 644篇 |
2015年 | 541篇 |
2014年 | 846篇 |
2013年 | 2501篇 |
2012年 | 984篇 |
2011年 | 1309篇 |
2010年 | 1083篇 |
2009年 | 1150篇 |
2008年 | 1313篇 |
2007年 | 1427篇 |
2006年 | 1217篇 |
2005年 | 1026篇 |
2004年 | 1052篇 |
2003年 | 997篇 |
2002年 | 985篇 |
2001年 | 1237篇 |
2000年 | 892篇 |
1999年 | 508篇 |
1998年 | 371篇 |
1997年 | 391篇 |
1996年 | 434篇 |
1995年 | 459篇 |
1994年 | 433篇 |
1993年 | 366篇 |
1992年 | 359篇 |
1991年 | 339篇 |
1990年 | 369篇 |
1989年 | 345篇 |
1988年 | 303篇 |
1987年 | 302篇 |
1986年 | 275篇 |
1985年 | 280篇 |
1984年 | 294篇 |
1983年 | 282篇 |
1982年 | 269篇 |
1981年 | 267篇 |
1980年 | 231篇 |
1979年 | 249篇 |
1978年 | 198篇 |
1977年 | 198篇 |
1976年 | 153篇 |
1975年 | 169篇 |
1973年 | 180篇 |
1972年 | 164篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Diana W. Bianchi MD Gretchen K. Zickwolf Melissa C. Yih Alan F. Flint Ossie H. Geifman Marlena S. Erikson John M. Williams 《黑龙江环境通报》1993,13(4):293-300
Fetal nucleated erythrocytes (NRBC) in maternal blood are a non-invasive source of fetal DNA for prenatal genetic screening. We compared the effectiveness of three monoclonal antibodies for the separation of fetal cells from maternal blood by flow sorting. Mononuclear blood cells from 49 healthy pregnant women were incubated with antibody to CD 71, CD 36, and/or glycophorin A (GPA), employed singly or in combination with each other. These monoclonal antibodies recognize surface antigens on haematopoietic precursor cells. Successful isolation of fetal cells was defined as detection of Y chromosomal sequences in maternal blood from women carrying male fetuses, with absence of Y sequences when female fetuses were carried. Thus, gender prediction accuracy was used as a measure of fetal cell separation. Using anti-CD 71 to isolate fetal cells, gender prediction was 57 per cent correct; with anti-CD 36, it was 88 per cent correct. Anti-GPA, an erythrocyte-specific antigen, used alone or in combination with anti-CD 71 or 36, improved gender prediction to 100 per cent. We conclude that antibody to GPA improves the retrieval of fetal NRBC from maternal blood, permitting genetic analysis by the polymerase chain reaction. 相似文献
994.
J. H. A. M. Tuerlings MD A. S. P. M. Breed R. Vosters G. J. P. A. Anders 《黑龙江环境通报》1993,13(4):301-306
A 70,XXX, +18 karyotype was found by chorionic villus sampling, while the fetal fibroblast culture of the affected fetus revealed a 47,XX,+ 18 karyotype. From several possible mechanisms, we assume that a second gamete fusion occurred after the first cell division of the zygote. According to this interpretation, the mosaicism arose in very early pregnancy (at the two-cell stage). This discrepancy can therefore be explained by selection pressure, due to the differentiation processes in the embryonic tissues. 相似文献
995.
Lee P. Shulman MD Patricia L. Gordon Donald S. Emerson R. Sidney Wilroy Sherman Elias 《黑龙江环境通报》1993,13(5):403-409
We describe the prenatal diagnosis of isolated bilateral fetal microphthalmia in a woman at increased risk of having a fetus with microphthalmia. Ultrasound examinations at 161 and 19-5 weeks' gestation demonstrated bilateral fetal microphthalmia with no other associated structural defects. The patient elected to terminate her pregnancy at 19.5 weeks. Pathological evaluation of the products of conception obtained by dilation and evacuation confirmed the prenatal diagnosis of isolated bilateral fetal microphthalmia. 相似文献
996.
Influence of titanium dioxide nanoparticles on speciation and bioavailability of arsenite 总被引:2,自引:0,他引:2
Sun H Zhang X Zhang Z Chen Y Crittenden JC 《Environmental pollution (Barking, Essex : 1987)》2009,157(4):1165-1170
In this study, the influence of the co-existence of TiO2 nanoparticles on the speciation of arsenite [As(III)] was studied by observing its adsorption and valence changing. Moreover, the influence of TiO2 nanoparticles on the bioavailability of As(III) was examined by bioaccumulation test using carp (Cyprinus carpio). The results showed that TiO2 nanoparticles have a significant adsorption capacity for As (III). Equilibrium was established within 30 min, with about 30% of the initial As (III) being adsorbed onto TiO2 nanoparticles. Most of aqueous As (III) was oxidized to As(V) in the presence of TiO2 nanoparticles under sunlight. The carp accumulated considerably more As in the presence of TiO2 nanoparticles than in the absence of TiO2 nanoparticles, and after 25-day exposure, As concentration in carp increased by 44%. Accumulation of As in viscera, gills and muscle of the carp was significantly enhanced by the presence of TiO2 nanoparticles. 相似文献
997.
Steen Solvang Jensen Tim Larson K.C. Deepti Joel D. Kaufman 《Atmospheric environment (Oxford, England : 1994)》2009,43(30):4544-4556
We evaluated the Danish AirGIS air quality and exposure model system using air quality measurement data from New York City in the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). Measurements were used from three US EPA Air Quality System (AQS) monitoring stations and a comprehensive MESA Air measurement campaign including about 150 different locations and about 650 samples of about 2 week measurements of NOx, NO2 and PM2.5. AirGIS is a deterministic exposure model system based on the dispersion models Operational Street Pollution Model (OSPM) and the Urban Background Model (UBM). The UBM model reproduced the annual levels within 1–26% depending on station and pollutant at the three urban background EPA monitor stations, and generally reproduced well the seasonal and diurnal variation. The full model with OSPM and UBM reproduced the MESA Air measurements with a correlation coefficient of r2 = 0.51 for NOx, r2 = 0.28 for NO2 and r2 = 0.73 for PM2.5. 相似文献
998.
The types of treatment most commonly used by pulp mills are biological treatments in combination with sedimentation or coagulation/flocculation as pretreatment. The main issues faced by these types of treatment are low efficiency in the removal of organic matter and the loss of aggregate value for the recovered fiber. Therefore, this study aims to evaluate the use of microfiltration (MF) combined with a membrane bioreactor (MBR) for the treatment of bleach pulp mill effluents. The results showed that the use of the MF-MBR system was an excellent alternative for the treatment of bleach pulp mill effluents with an average COD removal of 95%. The microfiltration allowed the recovery of fibers, which can be returned to the production process without losing economic value, and produced a better quality effluent for further treatment in the MBR. The MBR presented high efficiency removal of organic matter. 相似文献
999.
1000.