全文获取类型
收费全文 | 13563篇 |
免费 | 1631篇 |
国内免费 | 7147篇 |
专业分类
安全科学 | 2245篇 |
废物处理 | 544篇 |
环保管理 | 1637篇 |
综合类 | 11882篇 |
基础理论 | 2527篇 |
环境理论 | 21篇 |
污染及防治 | 1983篇 |
评价与监测 | 523篇 |
社会与环境 | 698篇 |
灾害及防治 | 281篇 |
出版年
2024年 | 65篇 |
2023年 | 482篇 |
2022年 | 701篇 |
2021年 | 808篇 |
2020年 | 860篇 |
2019年 | 847篇 |
2018年 | 723篇 |
2017年 | 712篇 |
2016年 | 863篇 |
2015年 | 923篇 |
2014年 | 811篇 |
2013年 | 1498篇 |
2012年 | 1408篇 |
2011年 | 1529篇 |
2010年 | 1013篇 |
2009年 | 1162篇 |
2008年 | 913篇 |
2007年 | 1120篇 |
2006年 | 1069篇 |
2005年 | 780篇 |
2004年 | 657篇 |
2003年 | 595篇 |
2002年 | 433篇 |
2001年 | 372篇 |
2000年 | 354篇 |
1999年 | 303篇 |
1998年 | 207篇 |
1997年 | 191篇 |
1996年 | 152篇 |
1995年 | 165篇 |
1994年 | 112篇 |
1993年 | 120篇 |
1992年 | 73篇 |
1991年 | 35篇 |
1990年 | 42篇 |
1989年 | 28篇 |
1988年 | 22篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1973年 | 8篇 |
1971年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
281.
Ossie Geifman-Holtzman Eliezer J. Holtzman Theresa J. Vadnais Vincent E. Phillips Eleanor L. Capeless Diana W. Bianchi MD 《黑龙江环境通报》1995,15(3):261-268
The objective of this study was to detect fetal HLA-DQα gene sequences in maternal blood. HLA-DQα genotypes of 70 pregnant women and their partners were determined for type A1. We specifically sought couples where the father, but not the mother, had genotype A1. In 12 women, maternal blood samples were flow-sorted. Candidate fetal cells were isolated and amplified by using PCR primers specific for a paternal HLA-DQα A1 allele. Fetal HLA-DQα A1 genotype was predicted from sorted cells; amniocytes or cheek swabs were used for confirmation. Six of twelve sorted samples had amplification products indicating the presence of the HLA-DQα A1 allele; 6/12 did not. Prediction of the fetal genotype was 100 per cent correct, as determined by subsequent amplification of amniocytes or cheek swabs. We conclude that paternally inherited uniquely fetal HLA-DQα gene sequences can be identified in maternal blood. This system permits the identification of fetal cells independent of fetal gender, and has the potential for non-invasive prenatal diagnosis of paternally inherited conditions. 相似文献
282.
B. N. Chodirker M.D. A. E. Chudley K. M. Macdonald C. R. Harman J. A. Evans 《黑龙江环境通报》1994,14(11):1086-1089
This study was undertaken to evaluate the relationship between maternal serum alpha-fetoprotein (MSAFP) levels and oesophageal atresia (OA). OA occurred in 16 fetuses of mothers who had an MSAFP test in the study interval. The multiple of the median (MOM) value for MSAFP averaged 1·54 ± 0·65 (range 0·5–2·9 MOM), which was significantly higher than the value seen in controls. The median MOM was 1·35. Using a cut-off of 2·5 MOM, the sensitivity of MSAFP for detecting OA was 19 per cent. Although OA should be considered in the differential diagnosis of an elevated MSAFP level, MSAFP cannot be considered an appropriate screening test for OA given the low sensitivity. 相似文献
283.
A stopped-flow reversed flow injection method for the determination of free cyanide is proposed. Pyridine-barbituric acid mixture is injected in the flow system as reagent to form the colour species with cyanide. The flow is stopped when the reagent zone comes in the flow cell, where absorbance-time data are collected at 580nm wavelength. The linear range of the determination is 0.1 -10μg/ml CN-. The sampling rate is 60h-1 and the relative standard deviation is 1.6% (n=16) at 5.0 μg/ml CN-1 level. With satisfactory results, the proposed method was applied to the determination of free cyanide in wastewater without sample pretreatment. 相似文献
284.
William D. Boelter MD Beth Ann Burt Elaine B. Spector David R. Hinton Zdena Pavlova Atsuko Fujimoto 《黑龙江环境通报》1990,10(11):703-715
A pregnant woman with indeterminate Duchenne muscular dystrophy (DMD) carrier status, but with DMD diagnosed in her deceased brother (unavailable for study), presented for prenatal diagnosis, intending to continue the pregnancy only if proven unaffected with DMD with near absolute certainty. Creatine kinase (CK) assays to clarify carrier status were inconclusive. Male sex in the fetus was identified, but DNA restriction fragment length polymorphism (RFLP) analysis was not yet available to this centre to investigate the possible transmission of the DMD gene, and the pregnancy was terminated. Tissue histology and dystrophin protein analysis demonstrated the absence of DMD. In a situation with proven maternal carrier status, future fetal inheritance of the opposite maternal X chromosome would indicate the presence of DMD. However, maternal carrier status remained in doubt through a second pregnancy, even with RFLP studies, and was finally established when dystrophin analysis confirmed the presence of DMD in the second fetus. Histologic findings are presented, contrasting features in the two fetuses. The value of dystrophin analysis for establishing the diagnosis of fetal DMD, in this case proving maternal carrier status in a difficult situation, and for demonstrating DMD gene:RFLP haplotype relationships is illustrated. 相似文献
285.
讨论了聚氧硫酸根合高铁处理煤泥水的作用机理及使用的影响因素,有助于选择厂实现洗煤水闭路循环,以提高选煤厂的经济效益和社会效益。 相似文献
286.
绿色高强混凝土——硅灰混凝土 总被引:4,自引:0,他引:4
硅灰是冶金厂生产硅铁和工业硅过程中产生的废灰,硅灰混凝土为绿色混凝土,它不仅节约了水泥熟料,而且改善了环境,大大促进了混凝土和建筑工程的健康发展,混凝土中掺入硅灰可得到高强和超高强混凝土,用此混凝土浇制的结构物其安全度大大提高,经济效益显著,硅灰混凝土还可以有效抑制碱骨料反应,提高结构物的安全度和耐久性,延长使用寿命。 相似文献
287.
288.
289.
290.
Experimental data are presented to test and validate a kinetic model for the oxidation of 2-chlorophenol wastewater by photo-assisted Fenton process. The data showed that this process had produced good effects under acidic conductions. Up to 90% 2-chlorophenol was removed after 90-minute reaction time with H2O2 of 25% CODCr. in, while in UV/H2O2 system ordy 16.8% 2-chlorophenol was removed after one hour treatment. The optimal pH in this reaction occurred between pH 3.0 and pH 4.0. The reaction kinetics for photo-assisted Fenton process experimented in this research was investigated. Kinetic models were proposed for the treatment of 2-chlorophenol wastewater. The reaction was found to follow the 2nd order. The equations of reaction kinetics are as follows:-d[RH]/dt=KRH[RH][H2O2]0exp(-KH2o2t);-d[CODCr]/dt=KCODCr[CODCr][H2O2]0exp(-K′t).The prediction of the models was found to be in a good agreement with experimental results, thus confimfing the proposed reaction mechanism. 相似文献