全文获取类型
收费全文 | 25823篇 |
免费 | 237篇 |
国内免费 | 244篇 |
专业分类
安全科学 | 679篇 |
废物处理 | 898篇 |
环保管理 | 3350篇 |
综合类 | 6005篇 |
基础理论 | 6153篇 |
环境理论 | 9篇 |
污染及防治 | 6430篇 |
评价与监测 | 1576篇 |
社会与环境 | 1063篇 |
灾害及防治 | 141篇 |
出版年
2022年 | 177篇 |
2018年 | 312篇 |
2017年 | 318篇 |
2016年 | 464篇 |
2015年 | 376篇 |
2014年 | 581篇 |
2013年 | 1897篇 |
2012年 | 713篇 |
2011年 | 967篇 |
2010年 | 748篇 |
2009年 | 856篇 |
2008年 | 956篇 |
2007年 | 1009篇 |
2006年 | 909篇 |
2005年 | 768篇 |
2004年 | 753篇 |
2003年 | 782篇 |
2002年 | 702篇 |
2001年 | 962篇 |
2000年 | 646篇 |
1999年 | 447篇 |
1998年 | 281篇 |
1997年 | 300篇 |
1996年 | 331篇 |
1995年 | 346篇 |
1994年 | 358篇 |
1993年 | 293篇 |
1992年 | 327篇 |
1991年 | 335篇 |
1990年 | 349篇 |
1989年 | 319篇 |
1988年 | 300篇 |
1987年 | 250篇 |
1986年 | 251篇 |
1985年 | 276篇 |
1984年 | 252篇 |
1983年 | 260篇 |
1982年 | 264篇 |
1981年 | 269篇 |
1980年 | 225篇 |
1979年 | 227篇 |
1978年 | 227篇 |
1977年 | 200篇 |
1976年 | 213篇 |
1975年 | 181篇 |
1974年 | 228篇 |
1973年 | 195篇 |
1972年 | 199篇 |
1971年 | 174篇 |
1967年 | 201篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
681.
This study provides data on the incidence of fetal trisomies 21, 18, and 13 at 9–14 weeks' gestation in women aged 35–45 years and estimates of maternal age-specific risks in women aged 20–45 years. Our data from 5814 singleton pregnancies undergoing first-trimester karyotyping for the sole indication of maternal age ⩾ 35 years were combined with those from two previous reports and the incidence of the trisomies was calculated from a total of 15 793 pregnancies. Comparison of incidences at 9–14 weeks' gestation with published data at 15–20 weeks' gestation and in livebirths demonstrated that at birth the maternal age-specific incidence of trisomy 21 is 33 per cent lower than at 15–20 weeks' gestation and 54 per cent lower than at 9–14 weeks' gestation. Furthermore, the relative frequency of trisomies 18 and 13 decreases from 30 per cent at 9–14 weeks to 22 per cent at 15–20 weeks and 14 per cent at birth. 相似文献
682.
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
683.
Ultrasound examination at 12 weeks' gestation revealed severe generalised subcutaneous oedema in a pregnancy at risk for achondrogenesis type II. Transvaginal scanning confirmed the oedema and suggested abnormal limb development. The prenatal diagnosis was confirmed by X-ray examination after transvaginal termination. 相似文献
684.
Gross scoliosis of the fetal thoracic spine was diagnosed at 18 weeks gestation. The pregnancy was terminated and the fetus found to have webbing of the neck and an imperforate anus in addition to vertebral defects. 相似文献
685.
686.
687.
688.
C. Clark K. F. Kelly N. Smith N. Fairweather T. Brown A. Johnston N. E. Haites 《黑龙江环境通报》1991,11(7):467-470
The polymerase chain reaction has been used to detect an abundant class of short repeat DNA families of the form (dC-dA)n.(dG-dT)n, known as microsatellites. These units are found throughout the human genome and have been characterized for several loci including APOC2 on chromosome 19ql2-ql3.2. The locus APOC2 is linked to the gene for dystrophia myotonica and a microsatellite within this locus was used to derive polymorphisms in a family to predict the inheritance of the disease. Chorionic villus sampling (CVS) was performed at 151/2 weeks' gestation. Following DNA extraction from the CVS material and parental blood samples, microsatellite analysis was carried out by the polymerase chain reaction. 相似文献
689.
Fetal urinary insulin-like growth factor I and binding protein 3 in bilateral obstructive uropathies
L. Bussieres K. Laborde J. C. Souberbielle F. Muller M. Dommergues C. Sachs 《黑龙江环境通报》1995,15(11):1047-1055
Fetal urinary concentrations of insulin-like growth factor I (UIGF-I) and binding protein 3 (UIGFBP-3) were determined in patients with prenatal diagnosis of bilateral obstructive uropathy. Patients were retrospectively assigned to three groups, on the basis of outcome: group 1, termination of pregnancies (n = 11) with sonographic evidence of severe oligohydramnios or renal dysplasia, confirmed at histological examination; group 2, patients (n = 10) with postnatal plasma creatinine > 50 μmol/1 at the age of 1 year (1 yr-pCreat); and group 3, patients (n = 16) with 1 yr-pCreat ≤ μmol/1. The results show a significant increase in UIGF-I and UIGFBP-3 in groups 1 (18 159 ± 9083 pg/ml; 2657 ± 669 ng/ml) and 2 (1574 ± 847 pg/ml; 176 ± 50 ng/ml) in comparison with group 3 (35 ± 6 pg/ml; 21 ± 2 ng/ml). UIGF-I and UIGFBP-3 were significantly correlated with postnatal plasma creatinine, and were both sensitive (90 per cent; 80 per cent) and specific (88 per cent; 88 per cent) for prediction of elevated 1 yr-pCreat (>50 μmol/1). Fetal urinary IGF-I and IGFBP-3 are increased in severe fetal bilateral obstructive uropathy, possibly reflecting tubular dysfunction or/and increased synthesis consequent upon fetal kidney injury. Their predictive value for postnatal renal function needs further assessment. 相似文献
690.
通过两季马铃薯大田试验,研究了嗪草酮在灌溉沙壤土中的消失和移动情况。结果表明,表层土壤中,嗪草酮施用后最初7~15天内其含量急剧降低,此后随时间推移降低幅度平缓,1993年和1994年试验结束时的残留量分别为5.9μg/kg和2.3μg/kg。两年共采集的379个土样(分布在15~75cm各土层)中只有5个检测到有嗪草酮。1994年大田135cm土层处的水样中,嗪草酮的检测率高达66%,检测浓度范围为0.06~15.85μg/kg,平均浓度为1.94μg/kg。相比较,嗪草酮在大田试验中的消失速率远大于实验室控制条件下的降解速率。 相似文献