全文获取类型
收费全文 | 25290篇 |
免费 | 214篇 |
国内免费 | 191篇 |
专业分类
安全科学 | 583篇 |
废物处理 | 1051篇 |
环保管理 | 3148篇 |
综合类 | 5582篇 |
基础理论 | 5779篇 |
环境理论 | 9篇 |
污染及防治 | 6409篇 |
评价与监测 | 1571篇 |
社会与环境 | 1463篇 |
灾害及防治 | 100篇 |
出版年
2022年 | 187篇 |
2021年 | 199篇 |
2019年 | 165篇 |
2018年 | 327篇 |
2017年 | 297篇 |
2016年 | 500篇 |
2015年 | 383篇 |
2014年 | 561篇 |
2013年 | 1792篇 |
2012年 | 661篇 |
2011年 | 957篇 |
2010年 | 772篇 |
2009年 | 868篇 |
2008年 | 986篇 |
2007年 | 1081篇 |
2006年 | 959篇 |
2005年 | 791篇 |
2004年 | 826篇 |
2003年 | 812篇 |
2002年 | 756篇 |
2001年 | 953篇 |
2000年 | 651篇 |
1999年 | 454篇 |
1998年 | 283篇 |
1997年 | 310篇 |
1996年 | 315篇 |
1995年 | 358篇 |
1994年 | 352篇 |
1993年 | 320篇 |
1992年 | 300篇 |
1991年 | 335篇 |
1990年 | 299篇 |
1989年 | 273篇 |
1988年 | 275篇 |
1987年 | 248篇 |
1986年 | 224篇 |
1985年 | 229篇 |
1984年 | 279篇 |
1983年 | 271篇 |
1982年 | 279篇 |
1981年 | 227篇 |
1980年 | 210篇 |
1979年 | 207篇 |
1978年 | 210篇 |
1977年 | 179篇 |
1976年 | 167篇 |
1975年 | 174篇 |
1974年 | 197篇 |
1973年 | 151篇 |
1967年 | 158篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
501.
502.
In several branches of science and technology a gaseous phase is dispersed into a liquid in the form of bubbles, a gaseous
component then dissolves into the liquid and subsequently undergoes chemical reaction. The overall process performance can
be improved substantially when the area of gas–liquid contact is increased. By subjecting the liquid phase to low frequency
vibrations, the bubbles are shown to suffer significant breakage, induced by resonance. When the vibration is properly tuned,
the interfacial area is found to increase by a factor of 1.8–2.4, depending on the properties of the liquid. Resonance-induced
bubble breakage phenomena have a great potential for improving the rates of chemical processes involving fast reactions, with
minimal energy input.
Received: 7 July 2000 / Accepted in revised form: 28 August 2000 相似文献
503.
This paper investigates the current treatment of environmental issues by two companies within the large made-to-order sector. Fifty questionnaires were issued to the design team of each company to assess current practice in the integration of environmental issues with design activities, awareness of environmental issues, awareness of existing environmental design tools and the preferred format for a potential clean design tool. 相似文献
504.
505.
506.
507.
Maternal serum alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (βhCG) measurements taken prior to chorionic villus sampling (CVS) in 21 patients who subsequently miscarried were compared with measurements in a control group of 113 patients with uneventful pregnancies. Patients with AFP levels of 10 iu/ml or more prior to the CVS had a 4·3 times greater risk of miscarriage (95 per cent confidence interval 1·3–13·6). AFP levels obtained 1 week after the CVS in the 13 patients with late miscarriages were higher than in the control group (P = 0·06). Patients miscarrying had a greater rise in AFP (P = 0·06) and a greater fall in βhCG levels (P = 0·04) following the CVS procedure, compared with the control subjects. Each 10-unit change in the difference between AFP or βhCG levels prior to and 1 week following the CVS was associated with a significantly increased risk for late miscarriage. Elevated maternal serum AFP levels early in pregnancy and changes in AFP and βhCG levels following CVS may predict an increased risk for subsequent miscarriage. 相似文献
508.
509.
510.