全文获取类型
收费全文 | 14904篇 |
免费 | 107篇 |
国内免费 | 163篇 |
专业分类
安全科学 | 361篇 |
废物处理 | 614篇 |
环保管理 | 1653篇 |
综合类 | 3322篇 |
基础理论 | 3468篇 |
环境理论 | 8篇 |
污染及防治 | 3749篇 |
评价与监测 | 1138篇 |
社会与环境 | 779篇 |
灾害及防治 | 82篇 |
出版年
2022年 | 134篇 |
2021年 | 113篇 |
2019年 | 107篇 |
2018年 | 208篇 |
2017年 | 217篇 |
2016年 | 315篇 |
2015年 | 242篇 |
2014年 | 414篇 |
2013年 | 1079篇 |
2012年 | 463篇 |
2011年 | 614篇 |
2010年 | 490篇 |
2009年 | 545篇 |
2008年 | 593篇 |
2007年 | 616篇 |
2006年 | 566篇 |
2005年 | 511篇 |
2004年 | 477篇 |
2003年 | 476篇 |
2002年 | 453篇 |
2001年 | 603篇 |
2000年 | 385篇 |
1999年 | 276篇 |
1998年 | 152篇 |
1997年 | 172篇 |
1996年 | 180篇 |
1995年 | 196篇 |
1994年 | 184篇 |
1993年 | 137篇 |
1992年 | 168篇 |
1991年 | 176篇 |
1990年 | 174篇 |
1989年 | 146篇 |
1988年 | 158篇 |
1987年 | 98篇 |
1986年 | 133篇 |
1985年 | 131篇 |
1984年 | 125篇 |
1983年 | 122篇 |
1982年 | 123篇 |
1981年 | 124篇 |
1980年 | 89篇 |
1979年 | 101篇 |
1978年 | 103篇 |
1976年 | 95篇 |
1974年 | 105篇 |
1972年 | 87篇 |
1971年 | 85篇 |
1967年 | 102篇 |
1964年 | 92篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
31.
S. Savas S. Eraslan S. Kantarci B. Karaman D. Acarsoz T. Tükel O. Cogulu F. Ozkinay S. Basaran K. Aydınlı M. Yuksel-Apak B. Kirdar 《黑龙江环境通报》2002,22(8):703-709
Childhood-onset spinal muscular atrophy (SMA) is one of the most common neurodegenerative genetic disorders. SMN1 is the SMA-determining gene deleted or mutated in the majority of SMA cases. There is no effective cure or treatment for this disease yet. Thus, the availability of prenatal testing is important. Here we report prenatal prediction for 68 fetuses in 63 Turkish SMA families using direct deletion analysis of the SMN1 gene by restriction digestion. The genotype of the index case was known in 40 families (Group A) but unknown in the remaining 23 families (Group B). A total of ten fetuses were predicted to be affected. Eight of these fetuses were derived from Group A and two of these fetuses were from Group B families. Two fetuses from the same family in Group A had the SMNhyb1 gene in addition to homozygous deletion of the NAIP gene. One fetus from Group A was homozygously deleted for only exon 8 of the SMN2 gene, and further analysis showed the presence of both the SMN1 and SMNhyb1 genes but not the SMN2 gene. In addition, one carrier with a homozygous deletion of only exon 8 of the SMN1 gene was detected to have a SMNhyb2 gene, which was also found in the fetus. To our knowledge, these are the first prenatal cases with SMNhyb genes. Follow-up studies demonstrated that the prenatal predictions and the phenotype of the fetuses correlated well in 33 type I pregnancies demonstrating that a careful molecular analysis of the SMN genes is very useful in predicting the phenotype of the fetus in families at risk for SMA. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
32.
This paper summarizes developments made in the field of waste-to-energy technology between the 1980s and the present. In the USA, many waste-to-energy systems were developed in the 1980s and early 1990s. These plants generated power relatively efficiently (typically 23%) in 60 bar/ 443 degrees C boilers. Unfortunately, the development came to a stop when the US Supreme Court rejected the practice of waste flow control in 1994. Consequently, waste was directed to mega-landfills, associated with very negative environmental impacts. However, given landfill taxes and increased fuel prices, new waste-to-energy projects have recently been developed. Attractive premiums for renewable power production from municipal waste have been introduced in several European countries. This triggered important innovations in the field of improved energy recovery. Examples of modern waste-to-energy plants are Brescia and Amsterdam with net efficiencies of 24 and 30%, respectively. Incineration is traditionally preferred in Japan due to space constraints. New legislation promoted ash melting or gasification to obtain improved ash quality. However, these processes reduce the efficiency in terms of energy, cost and availability. A new oxygen-enriched waste-to-energy system is under development in order to better achieve the required inert ash quality. 相似文献
33.
Geochemical characteristics of surficial sediments in the Panangad region of Cochin estuary, the largest brackish-water humid ecosystem in the south-west coast of India, were analysed. Temporal variations in nutrient stoichiometry, seasonal characteristics of redox elements Fe and S, and the phosphorus geochemistry were employed for the purpose. The stoichiometric analysis pointed towards autochthonous origin of organic matter, possibility of nitrogen limitation, and allochthonous modification of redox conditions. Seasonal variations were not statistically significant for all the geochemical parameters, whereas significant spatial variations were observed with lower values at sandy stations, suggesting that the texture of the sediments is the main factor influencing the sediment geochemistry. Significant inter-relations between the geochemical parameters also suggest a common control mechanism. Based on these geochemical characteristics, the study region can be effectively categorized into two distinct zones, viz. (1) erosion and transportation and (2) deposition zones. 相似文献
34.
35.
36.
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
37.
This paper examines the relationship between survivor reactions to a downsizing and retention subsequent to a downsizing. We hypothesize that survivors who experience the downsizing as distributively, procedurally, and interactionally just and who see top management as trustworthy will feel more attached to the organization because each reduces the threat inherent in downsizing. In addition, we hypothesize that survivors who feel empowered will also feel more attached to the organization because they feel better able to cope with the downsizing. We further hypothesize that those survivors who feel more attached to the organization following the downsizing will be more likely to remain with the organization in the coming year. The theoretical model is tested on a sample of aerospace employees who survived an organizational downsizing. The trustworthiness of management, distributive justice, procedural justice, and three dimensions of empowerment are found to facilitate more organizational attachment. Higher levels of attachment are found, in turn, to facilitate less voluntary turnover in the year following the downsizing. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
38.
39.
Stormwater runoff is now a major contributor to the pollution of coastal waters in the United States. Public agencies are responding by requiring stormwater monitoring to satisfy the National Pollutant Discharge Elimination System stormwater permit. However, studies to understand the utility of the current programs or to improve their usefulness have not yet been performed. In this paper, we evaluate the land-use-based program, the industrial stormwater permit program, and beach water-quality monitoring in the County of Los Angeles, California, to determine if the results will be helpful to planners and regulators in abating stormwater pollution. The utility of the program has been assessed based on the programs' ability to accurately estimate the emissions for different classes of land use. The land-use program appears successful, while the industrial monitoring program does not. Beach water-quality monitoring suffers from a lack of real-time monitoring techniques. We also provide suggested improvements, such as sampling method and time, and parameter selection. 相似文献
40.