全文获取类型
收费全文 | 40039篇 |
免费 | 429篇 |
国内免费 | 322篇 |
专业分类
安全科学 | 1095篇 |
废物处理 | 1514篇 |
环保管理 | 5299篇 |
综合类 | 6421篇 |
基础理论 | 11379篇 |
环境理论 | 24篇 |
污染及防治 | 10361篇 |
评价与监测 | 2484篇 |
社会与环境 | 1949篇 |
灾害及防治 | 264篇 |
出版年
2022年 | 278篇 |
2021年 | 261篇 |
2019年 | 293篇 |
2018年 | 524篇 |
2017年 | 559篇 |
2016年 | 791篇 |
2015年 | 668篇 |
2014年 | 980篇 |
2013年 | 3037篇 |
2012年 | 1183篇 |
2011年 | 1735篇 |
2010年 | 1441篇 |
2009年 | 1433篇 |
2008年 | 1688篇 |
2007年 | 1810篇 |
2006年 | 1591篇 |
2005年 | 1339篇 |
2004年 | 1327篇 |
2003年 | 1276篇 |
2002年 | 1238篇 |
2001年 | 1630篇 |
2000年 | 1163篇 |
1999年 | 718篇 |
1998年 | 536篇 |
1997年 | 565篇 |
1996年 | 574篇 |
1995年 | 630篇 |
1994年 | 575篇 |
1993年 | 511篇 |
1992年 | 539篇 |
1991年 | 490篇 |
1990年 | 500篇 |
1989年 | 528篇 |
1988年 | 446篇 |
1987年 | 404篇 |
1986年 | 377篇 |
1985年 | 401篇 |
1984年 | 399篇 |
1983年 | 420篇 |
1982年 | 409篇 |
1981年 | 347篇 |
1980年 | 320篇 |
1979年 | 351篇 |
1978年 | 300篇 |
1977年 | 265篇 |
1976年 | 244篇 |
1975年 | 244篇 |
1974年 | 232篇 |
1973年 | 245篇 |
1972年 | 264篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
551.
In the case-control study of 118 women with autosomal trisomy identified at prenatal diagnosis and their 442 karyotypically normal matched controls, we found that there was no overall association between risk of trisomy and the presence of vaginal bleeding during pregnancy. However, a lengthy duration of bleeding appears to predict increased risk of trisorny. 相似文献
552.
Citrullinaemia was presumed to be excluded in a fetus at risk by the direct assay of argininosuccinate synthetase in chorionic villi. The diagnosis was confirmed after amniocentesis by normal argininosuccinate synthetase activity in the cultured amniotic fluid cells and by a normal citrulline concentration in the amniotic fluid. The prediction of a normal fetus was confirmed at term by the birth of a non-citrullinaemic boy. 相似文献
553.
554.
555.
556.
557.
Maternal age specific rates for all major chromosome aberrations have been determined in 52 965 pregnancies in mothers 35 years of age and over at the time of amniocentesis. Rates increase exponentially with advancing maternal age for trisomies 21, 18 and 13, and for the XXX and XXY syndromes, but in the autosomal trisomies this rise appears to be followed by a levelling off at the upper end of the age range. A significant inverse relationship with maternal age is found for 45,X cases. It is postulated that these various patterns are the result of the interaction of three principal factors: a maternal age effect acting particularly on first meiotic nondisjunction: a higher spontaneous abortion rate with advancing maternal age for aneuploid as compared to euploid conceptions; and an increased probability of spontaneous abortion before the time of amniocentesis for conceptions with more extensive chromosome imbalance. A stepwise logistic regression analysis of 13 299 pregnancies in which both parental ages are known shows that the father's age does not influence these maternal age specific rates, with the possible exception of the 47,XXY syndrome. 相似文献
558.
In this paper we deal with the problem of identifying environmental principles for the design and operation of supply chains. The operations that are included in supply chains are briefly described along with the approaches that are applied in order to improve their environmental performance. A background of environmental principles for achieving eco-efficiency and building of environmentally friendly organizational systems is presented and emphasis is put on the application of such principles “from cradle to grave”. Then, environmental principles applicable to particular objects of logistics networks planning are identified and commented upon. In addition, selective case studies from the literature, which show the applicability of the formulated principles and their relevance to practice, are discussed. The paper concludes with some remarks regarding the benefits for companies and societies, in general, that occur as a result of the application of the formulated principles. 相似文献
559.
560.
Jörg Pfleiderer 《Die Naturwissenschaften》1989,76(7):297-300
Die Idee zu dieser Arbeit geht auf Diskussionen mit W. Priester über die Reduktion von Radiobeobachtungen ausgedehnter Galaxien im Jahre 1974 zurück. Die wesentlichen Teile wurden während eines Aufenthalts des Autors am Department of Astronomy, University of Florida, Gainesville, im Jahre 1987 entworfen. Ich habe ferner vielen Kollegen für hilfreiche Hinweise zu danken, darunter E. E. Baart, J. Condon, T. Cornwell, L. Erickson, S. Gottesman, J. Högbom, J. Skilling. 相似文献