全文获取类型
收费全文 | 30362篇 |
免费 | 344篇 |
国内免费 | 457篇 |
专业分类
安全科学 | 951篇 |
废物处理 | 1439篇 |
环保管理 | 3675篇 |
综合类 | 5070篇 |
基础理论 | 7957篇 |
环境理论 | 18篇 |
污染及防治 | 8029篇 |
评价与监测 | 2072篇 |
社会与环境 | 1773篇 |
灾害及防治 | 179篇 |
出版年
2023年 | 140篇 |
2022年 | 323篇 |
2021年 | 316篇 |
2020年 | 240篇 |
2019年 | 284篇 |
2018年 | 478篇 |
2017年 | 477篇 |
2016年 | 742篇 |
2015年 | 569篇 |
2014年 | 886篇 |
2013年 | 2418篇 |
2012年 | 1061篇 |
2011年 | 1435篇 |
2010年 | 1169篇 |
2009年 | 1198篇 |
2008年 | 1437篇 |
2007年 | 1485篇 |
2006年 | 1263篇 |
2005年 | 1093篇 |
2004年 | 983篇 |
2003年 | 1075篇 |
2002年 | 949篇 |
2001年 | 1238篇 |
2000年 | 863篇 |
1999年 | 517篇 |
1998年 | 347篇 |
1997年 | 358篇 |
1996年 | 356篇 |
1995年 | 423篇 |
1994年 | 446篇 |
1993年 | 352篇 |
1992年 | 375篇 |
1991年 | 352篇 |
1990年 | 386篇 |
1989年 | 341篇 |
1988年 | 296篇 |
1987年 | 278篇 |
1986年 | 223篇 |
1985年 | 248篇 |
1984年 | 265篇 |
1983年 | 256篇 |
1982年 | 241篇 |
1981年 | 222篇 |
1980年 | 175篇 |
1979年 | 194篇 |
1978年 | 176篇 |
1975年 | 140篇 |
1974年 | 117篇 |
1972年 | 131篇 |
1971年 | 131篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
461.
462.
463.
464.
465.
466.
David M. Sherer MD James R. Woods Jr Jacques S. Abramowicz John A. Dipreta Leon A. Metlay Richard Jaffe 《黑龙江环境通报》1993,13(12):1079-1084
Although malignant transformation of fetal cervical teratoma is extremely rare, perinatal morbidity is high and usually related to the size of the tumour, which may compromise fetal swallowing and subsequently lead to upper airway obstruction. We present a case in which mid-trimester serial sonography demonstrated markedly rapid early growth of a lesion of this type between 17 and 19 weeks' gestation indicating the aggressive nature of this tumour, assisting parental decision to terminate the pregnancy. Histopathology confirmed grade 3 immaturity of the lesion. 相似文献
467.
The coastal seawater of Mediterranean of Alexandria receives large amount of discharged waters containing industrial wastes, sewage, and agricultural and domestic drainage. Fluoride and some parameters were(chemical and physical) determined. The data gave indication that the content and the amount of the discharged water largely affect the chemical composition of the coastal water. Stepwise regression analysis was highly significant and the model was very fruitful, where the observed and calculated values were mostly concordant. This may indicated that there was a relation between fluoride content in coastal seawater and its content in the discharged water. 相似文献
468.
P. Robbins-Furman J. T. Hecht M. Rocklin N. Maklad G. Greenhaw I. Wilkins MD 《黑龙江环境通报》1995,15(2):179-182
The diagnosis of Freeman–Sheldon syndrome was made by ultrasonographic evaluation of a 20-week fetus with a positive family history. The ultrasonographic features were abnormalities of the extremities and mouth. 相似文献
469.
M. Van Blerk MD J. Smitz L. De Catte C. Kumps J. Van Der Elst A. C. Van Steirteghem 《黑龙江环境通报》1992,12(12):1062-1066
This study explores if assay of cancer antigen 125 (CA 125) in maternal serum might aid the detection of Down's syndrome in the second trimester of pregnancy. CA 125 levels were determined retrospectively in stored maternal serum samples from ten Down's syndrome pregnancies and 78 controls matched for gestational and maternal age. In addition, second-trimester amniotic fluid samples from nine Down's syndrome and 109 unaffected pregnancies were analysed for CA 125. Maternal serum CA 125 values for Down's syndrome pregnancies were lower, with the median being 0.72 multiples of the unaffected population median. The medians for affected and unaffected pregnancies did not differ significantly and there was a considerable overlap in the range of values of cases and controls. The distribution of amniotic fluid CA 125 levels for Down's syndrome pregnancies resembled that for controls. From our present results, we could not find an association between Down's syndrome and second-trimester maternal serum or amniotic fluid CA 125 levels. 相似文献
470.
Mr. M. T. Rebello G. Hackett J. Smith F. E. Loeffler S. Robson N. Maclachlan R. W. Beard C. H. Rodeck R. Williamson D. V. Coleman C. Williams 《黑龙江环境通报》1991,11(1):41-46
Ten-ml samples of amniotic fluid were taken from pregnancies being terminated at 8–14 weeks' gestation. DNA was extracted from the amniotic cells by sequential centrifugation and analysed using the polymerase chain reaction (PCR). Fifteen samples were analysed for evidence of maternal contamination using Mfd5 oligo-nucleotide primers for repeat polymorphisms. Ten amniotic fluid samples were tested for the Delta-F508 deletion characteristic of cystic fibrosis to demonstrate a diagnostic application for the technique. In each case, DNA extracted from fetal tissue from the same pregnancy was included in the controls. In 14 of the 15 cases tested with the Mfd5 primers, both the amniotic fluid DNA and the fetal DNA showed no evidence of contaminating DNA. In one case, neither the amniotic fluid cells nor the fetal cells yielded results. In nine of the ten cases tested with the Delta-F508 primers, the amniotic fluid cell DNA provided accurate information about the genetic status of the fetus; in the tenth, the fetal DNA failed to amplify. The results indicate that adequate DNA can be extracted from amniotic fluid from 8 weeks' gestation onward and these samples are suitable for prenatal diagnosis using PCR. 相似文献