全文获取类型
收费全文 | 31161篇 |
免费 | 295篇 |
国内免费 | 235篇 |
专业分类
安全科学 | 812篇 |
废物处理 | 1198篇 |
环保管理 | 3921篇 |
综合类 | 7252篇 |
基础理论 | 7486篇 |
环境理论 | 6篇 |
污染及防治 | 7733篇 |
评价与监测 | 1767篇 |
社会与环境 | 1357篇 |
灾害及防治 | 159篇 |
出版年
2022年 | 219篇 |
2019年 | 234篇 |
2018年 | 401篇 |
2017年 | 391篇 |
2016年 | 601篇 |
2015年 | 426篇 |
2014年 | 626篇 |
2013年 | 2234篇 |
2012年 | 770篇 |
2011年 | 1084篇 |
2010年 | 959篇 |
2009年 | 1011篇 |
2008年 | 1174篇 |
2007年 | 1209篇 |
2006年 | 1105篇 |
2005年 | 897篇 |
2004年 | 999篇 |
2003年 | 912篇 |
2002年 | 859篇 |
2001年 | 1211篇 |
2000年 | 810篇 |
1999年 | 513篇 |
1998年 | 403篇 |
1997年 | 377篇 |
1996年 | 397篇 |
1995年 | 445篇 |
1994年 | 475篇 |
1993年 | 391篇 |
1992年 | 427篇 |
1991年 | 402篇 |
1990年 | 457篇 |
1989年 | 427篇 |
1988年 | 339篇 |
1987年 | 316篇 |
1986年 | 301篇 |
1985年 | 312篇 |
1984年 | 349篇 |
1983年 | 340篇 |
1982年 | 352篇 |
1981年 | 354篇 |
1980年 | 282篇 |
1979年 | 305篇 |
1978年 | 249篇 |
1977年 | 237篇 |
1976年 | 211篇 |
1975年 | 224篇 |
1974年 | 246篇 |
1973年 | 232篇 |
1972年 | 244篇 |
1967年 | 227篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
S. H. Dinius 《Journal of the American Water Resources Association》1987,23(5):833-843
ABSTRACT: This paper describes the formulation of an Index of Water Quality to evaluate the level of pollution in fresh water. A Four-Round Delphi equation, using a panel of seven nationally recognized water scientists, was performed to ascertain the pollutants to be included in the index, the relationship between the quantity of these pollutants in the water and the resulting quality of the water, and the importance of each pollution variable to each water use as well as to overall pollution. A multiplicative index was used to bring the pollutants together into one system. 相似文献
63.
Living veligers of the Cassoidea have been observed to use a mantle appendage to form and resorb periostracum. Anatomical and histological examinations of a ranellid (Cymatium sp.) larva collected from the Red Sea in 1987 revealed the structure and location of the pallial appendage. The mantle edges of juvenile or adult species of the Cassoidea do not show a comparable specialization. It is demonstrated that cassoid larval conch characters are sufficient to prove the existence of a pallial appendage without anatomical confirmation. A mantle appendage is not known from teleplanic (long-living planktic) veligers of other gastropod superfamilies. In cases where the larval strategies of the latter are known they are totally different. Therefore it is suggested that the adaptation of cassoid larvae to pelagic life is unique among gastropods representing an autapomorphic character of the superfamily. 相似文献
64.
Global change, i.e. the mega-process radically transforming the relationship between nature and human civilization since
the end of World War II, is investigated from the point of view of systems analysis. It is argued that this unbridled process
should rather be domesticated by planetary control strategies transpiring from a new science called “geocybernetics”. The
formal aspects of geocybernetic theory are sketched and illustrated in a tutorial theatre world reflecting the overall environment
and development problematic. Within this setting a straightforward operationalization of the sweeping “sustainable development”
ideal through a set of concise paradigms can be achieved. Evidence is provided that geocybernetics is actually feasible on
the basis of earth system modelling and fuzzy-control techniques. 相似文献
65.
66.
H. T. Schreuder 《Environmental monitoring and assessment》1994,33(3):237-245
Simplicity and efficiency in design and estimation are all important in deciding on sampling strategies. A simple model is given and illustrated for four practical situations to show how a good sampling strategy should be selected.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. 相似文献
67.
This study examines 45 cases of trisomy 13 and 59 cases of trisomy 18 and reports an algorithm to identify pregnancies with a fetus affected by trisomy 13 or 18 by a combination of maternal age fetal nuchal translucency (NT) thickness, and maternal serum free β-hCG and PAPP-A at 11–14 weeks of gestation. In this mixed trisomy group the median MoM NT was increased at 2.819, whilst the median MoMs for free β-hCG and PAPP-A were reduced at 0.375 and 0.201 respectively. We predict that with the use of the combined trisomy 13 and 18 algorithm and a risk cut-off of 1 in 150 will for a 0.3% false positive rate allow 95% of these chromosomal defects to be identified at 11–14 weeks. Such algorithms will enhance existing first trimester screening algorithms for trisomy 21. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
68.
T. Antoniadi C. Yapijakis P. Kaminopetros C. Makatsoris V. Velissariou D. Vassilopoulos M. B. Petersen 《黑龙江环境通报》2002,22(5):425-429
The presence of maternal cells in fetal samples constitutes a serious potential source for prenatal misdiagnosis. Here we present our approach for detecting maternal cell contamination (MCC) at prenatal diagnosis for eight monogenic disorders (autosomal recessive: β-thalassaemia, sickle-cell anaemia, cystic fibrosis, prelingual deafness; autosomal dominant: achondroplasia, Huntington disease, myotonic dystrophy, neurofibromatosis type I; X-linked: spinobulbar muscular atrophy). Our aim was to apply a simple and low-cost approach, which would easily and accurately provide information on the fetal tissue MCC status. MCC testing was applied to cases of recessive inheritance where the primary mutation screening of the fetus revealed the presence of the maternal mutation, to cases concerning dominant inheritance and to cases of multiple gestation. The potential presence of maternal cells was determined by the amplification of the 3′-HVR/APO B, D1S80, THO1 and VNTRI of vWf polymorphic loci, which have previously demonstrated high heterozygosity in Caucasians. Among 135 prenatal diagnoses, 44 finally needed to be tested for MCC (32.6%). MCC was detected in four cases, where DNA was isolated directly from chorionic villi samples (CVS), and in one case with DNA isolated directly from amniotic fluid (AF). In almost 90% of cases a simple test of one polymorphic locus provided sufficient information about MCC. The choice of the appropriate locus is therefore essential, while the simultaneous screening of both parents provides the means for distinguishing non-informative sites about MCC. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
69.
70.