首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   532篇
  免费   19篇
  国内免费   3篇
安全科学   32篇
废物处理   48篇
环保管理   84篇
综合类   87篇
基础理论   111篇
环境理论   1篇
污染及防治   128篇
评价与监测   27篇
社会与环境   24篇
灾害及防治   12篇
  2023年   3篇
  2022年   10篇
  2021年   9篇
  2020年   9篇
  2019年   12篇
  2018年   17篇
  2017年   18篇
  2016年   22篇
  2015年   19篇
  2014年   21篇
  2013年   50篇
  2012年   28篇
  2011年   41篇
  2010年   21篇
  2009年   21篇
  2008年   23篇
  2007年   29篇
  2006年   30篇
  2005年   22篇
  2004年   15篇
  2003年   16篇
  2002年   18篇
  2001年   12篇
  2000年   3篇
  1999年   4篇
  1998年   1篇
  1997年   8篇
  1996年   8篇
  1995年   10篇
  1994年   15篇
  1993年   8篇
  1992年   6篇
  1991年   9篇
  1990年   1篇
  1989年   1篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1980年   1篇
  1977年   1篇
  1968年   1篇
  1956年   1篇
排序方式: 共有554条查询结果,搜索用时 126 毫秒
261.
262.
Nevus sebaceous is a complex hamartoma most commonly found on the scalp, face, and neck and is often present at birth, although some may be diagnosed later in infancy. We report the first prenatal diagnosis of isolated nevus sebaceous that presented at 19 weeks' gestation as a large and exophytic tumor of the scalp. This case emphasizes the crucial role of ultrasound examination performed with high-frequency probes, which revealed associated diffuse lesions of the face. Identification of such a facial involvement could have a dramatic prognostic impact. © 2013 John Wiley & Sons, Ltd.  相似文献   
263.
264.
265.
Noroviruses (NoVs), currently recognised as the most common human food-borne pathogens, are ubiquitous in the environment and can be transmitted to humans through multiple foodstuffs. In this study, we evaluated the prevalence of human NoV genogroups I (GI) and II (GII) in 493 food samples including soft red fruits (n = 200), salad vegetables (n = 210) and bivalve mollusc shellfish (n = 83), using the Bovine Enterovirus type 1 as process extraction control for the first time. Viral extractions were performed by elution concentration and genome detection by TaqMan Real-Time RT-PCR (RT-qPCR). Experimental contamination using hepatitis A virus (HAV) was used to determine the limit of detection (LOD) of the extraction methods. Positive detections were obtained from 2 g of digestive tissues of oysters or mussels kept for 16 h in seawater containing 2.0–2.7 log10 plaque-forming units (PFU)/L of HAV. For lettuces and raspberries, the LOD was, respectively, estimated at 2.2 and 2.9 log10 PFU per 25 g. Of the molluscs tested, 8.4 and 14.4 % were, respectively, positive for the presence of GI NoV and GII NoV RNA. Prevalence in GI NoVs varied from 11.9 % for the salad vegetables samples to 15.5 % for the red soft fruits. Only 0.5 % of the salad and red soft fruits samples were positive for GII NoVs. These results highlight the high occurrence of human NoVs in foodstuffs that can be eaten raw or after a moderate technological processing or treatment. The determination of the risk of infection associated with an RT-qPCR positive sample remains an important challenge for the future.  相似文献   
266.
The virucidal efficacy of a pulsed light treatment applied to viral suspensions, glass beads and herb powders was studied for the F-RNA bacteriophage MS2. The experimental results obtained demonstrated the high potential of this technology to efficiently decontaminate simple matrices but underlined the complexity of application to complex food matrices.  相似文献   
267.
268.
Calluna vulgaris/peat microcosms have been used in an outdoor simulated acid rain experiment to test a series of hypotheses about sulphuric acid deposition effects upon the growth of Calluna on peat soil, namely: (1) Initially, enhanced acid input will enhance base cation and ammonium concentrations in soil solution. This may enhance uptake of these species, increasing foliar concentrations of base cations and nitrogen, and possibly foliar chlorophyll a and b concentrations. (2) If changes are induced in nutritional status, they may influence plant growth. (3) in the longer term, enhanced ammonium and base cation solubility occurring as a consequence of cation exchange reactions will lead, especially in winter months, to enhanced leaching losses. Hence any positive effects upon plant nutrition will not be sustainable. (4) the peat will acidify significantly over two years, in the shorter term primarily as a consequence of an enhanced mobile anion effect. (5) Acidification may reduce the rate of mineralisation of organic phosphorus and, in a phosphorus-deficient peat soil, this may lead to reduced foliar phosphate concentration and possibly induce phosphorus deficiency.

Most of these hypotheses were supported to some extent by the experimental results. the peat soil solution pH fell immediately in response to the acid treatments, and longer-term acidification continued progressively over the two years of the experiment. in the first year, the treatments significantly influenced the calcium, magnesium, phosphorus and nitrogen status of the leaves from Calluna new shoots, whereas in the second year calcium, potassium and phosphorus were influenced. However, in both years foliar phosphate concentration was enhanced, rather than reduced, in response to increased acid load. Foliar carbon and nitrogen concentrations fell with increasing acidity of  相似文献   
269.
270.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号