全文获取类型
收费全文 | 9866篇 |
免费 | 113篇 |
国内免费 | 94篇 |
专业分类
安全科学 | 283篇 |
废物处理 | 466篇 |
环保管理 | 1245篇 |
综合类 | 1198篇 |
基础理论 | 2671篇 |
环境理论 | 2篇 |
污染及防治 | 2785篇 |
评价与监测 | 708篇 |
社会与环境 | 667篇 |
灾害及防治 | 48篇 |
出版年
2022年 | 100篇 |
2021年 | 76篇 |
2020年 | 66篇 |
2019年 | 73篇 |
2018年 | 145篇 |
2017年 | 140篇 |
2016年 | 229篇 |
2015年 | 164篇 |
2014年 | 239篇 |
2013年 | 743篇 |
2012年 | 297篇 |
2011年 | 442篇 |
2010年 | 362篇 |
2009年 | 395篇 |
2008年 | 471篇 |
2007年 | 479篇 |
2006年 | 422篇 |
2005年 | 366篇 |
2004年 | 324篇 |
2003年 | 376篇 |
2002年 | 324篇 |
2001年 | 503篇 |
2000年 | 331篇 |
1999年 | 192篇 |
1998年 | 138篇 |
1997年 | 133篇 |
1996年 | 138篇 |
1995年 | 162篇 |
1994年 | 125篇 |
1993年 | 102篇 |
1992年 | 123篇 |
1991年 | 118篇 |
1990年 | 130篇 |
1989年 | 131篇 |
1988年 | 94篇 |
1987年 | 87篇 |
1986年 | 65篇 |
1985年 | 90篇 |
1984年 | 90篇 |
1983年 | 86篇 |
1982年 | 82篇 |
1981年 | 73篇 |
1980年 | 61篇 |
1979年 | 71篇 |
1978年 | 48篇 |
1977年 | 54篇 |
1976年 | 51篇 |
1975年 | 56篇 |
1974年 | 51篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
161.
162.
163.
164.
G. A. Hackett Dr. J. H. Smith M. T. Rebello C. T. H. Gray D. E. Rooney R. W. Beard F. E. Loeffler D. V. Coleman 《黑龙江环境通报》1991,11(5):311-315
Early arnniocentesis between 11 and 14 weeks' gestation was offered to 110 women at risk of a chromosomally abnormal fetus due to maternal age. Four were found to be unsuitable for the procedure, and 106 early amniocenteses were performed. In 102 cases, clear amniotic fluid was obtained with a single tap. There were two dry taps and two bloodstained tapis; sampling was repeated in three of these cases before 15 weeks. In the fourth case, placental biopsy was performed at 16 weeks. Thus, we were able to obtain a satisfactory sample in all but three cases(2.8 percent). Karyotyping of cells harvested from the early amniotic fluid samples was successful in all the 105 cases. Cell culture from the initial samples revealed a normal karyotype in 99 cases, two balanced translocations, two tetraploid karyotypes, and two cases of pseudomosaicism. Of the 105 pregnancies successfully sampled, there have been two losses to date (1–8 per cent). Two further patients presented with premature rupture of membranes, both pregnancies having successful outcomes. Sixty-two babies have delivered to date, with four congenital anomalies. There were no respiratory problems. Twenty-nine pregnancies are continuing without known complications, and details are not yet available on the remaining 12. The results indicate that early arnniocentesis may replace the traditional test at 15–17 weeks. 相似文献
165.
J. G. Hooker M. Lucas B. A. Richards I. M. Shirley B. D. Thompson R. H. T. Ward 《黑龙江环境通报》1984,4(1):29-33
Estimation of maternal serum alpha-fetoprotein (AFP) was used as a screening method for the detection of neural tube defects (NTDs) in 6344 women over three years. Of 88 (1.4 per cent) who had one or more serum AFP levels equal to, or greater than, 2.5 multiples of the median (MoM) for the relevant gestational age, 43 (0.68 per cent) underwent amniocentesis. There were eight NTDs. Four of these were screened by serum AFP, and all cases of spina bifida had serum AFP levels greater than 3.0 MoM, including one small open defect which was not seen on ultrasound. The other four cases of NTD, which were not screened, were identified by ultrasound. Of 64 singleton pregnancies 32 (50 per cent) had serum AFP levels between 2.5 and 3.0 MoM, and low birthweight (⪕2500 g) occurred in 29 per cent. Because of improvements in ultrasound techniques and the apparent falling incidence of NTD, the role of serum AFP as the primary screening procedure should be regularly reviewed. Effective screening is dependent on mothers booking early. 相似文献
166.
True microcephaly can be diagnosed at an early stage of gestation by serial measurements of fetal head growth as demonstrated by this case report in which the diagnosis of genetic microcephaly was made but termination refused. True microcephaly was evident at birth. 相似文献
167.
168.
ZHANG Tian-zhu 《环境科学学报(英文版)》2001,13(3):346-350
IntroductionCleanerproduction (CP)holdsgreatpromiseasaneffectivestrategyinthefaceofdoublechallengesofenvironmentalprotectionandeconomicdevelopment.In 1993,ademonstrationproject (B 4project) ,designedandexecutedbytheStateEnvironmentalProtectionAdministration (… 相似文献
169.
Dr. Yash P. Agrawal Päivi Ylikangas Markku T. Parviainen Ilkka M. Penttilä 《黑龙江环境通报》1994,14(12):1141-1149
The histochemical measurement of urea-resistant alkaline phosphatase from maternal blood neutrophils is known to have a high detection rate for the prenatal detection of Down's syndrome pregnancies. However, because the histochemical method is laborious and subjective to use, it has not gained widespread acceptance in prenatal screening programmes. We present a simple and objective method for the measurement of urea-resistant alkaline phosphatase by flow cytometry. The method should allow the design of larger studies aimed at evaluating the role of neutrophil urea-resistant alkaline phosphatase in the prenatal screening for Down's syndrome. 相似文献
170.
Information on maternal age and maternal serum alpha-fetoprotein, unconjugated oestriol (uE3), and human chorionic gonadotrophin (hCG) levels was used to investigate retrospectively the effect of estimating Edward's syndrome risk in women having multi-marker screening for Down's syndrome. The screened population comprised 15 pregnancies affected by Edward's syndrome, 15 with Down's syndrome and 5472 unaffected pregnancies. The use of all three markers to estimate Edward's syndrome risk would have led to the detection of 10–12 (67–80 per cent) cases with a false-positive rate of 0.3–0.6 per cent depending on the risk cut-off. A further case would have been detected as a result of screening for Down's syndrome alone. Similar results were obtained when the Edward's syndrome risk was based on uE3 and hCG only. These data suggest that extending Down's syndrome screening to include Edward's syndrome risk will yield a high detection rate with only a small increase in the false-positive rate. 相似文献