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   2761篇
  免费   29篇
  国内免费   15篇
安全科学   71篇
废物处理   68篇
环保管理   379篇
综合类   1072篇
基础理论   483篇
环境理论   4篇
污染及防治   498篇
评价与监测   139篇
社会与环境   83篇
灾害及防治   8篇
  2023年   22篇
  2022年   22篇
  2021年   26篇
  2020年   24篇
  2019年   23篇
  2018年   39篇
  2017年   48篇
  2016年   45篇
  2015年   49篇
  2014年   52篇
  2013年   162篇
  2012年   74篇
  2011年   108篇
  2010年   81篇
  2009年   96篇
  2008年   99篇
  2007年   119篇
  2006年   84篇
  2005年   76篇
  2004年   75篇
  2003年   78篇
  2002年   86篇
  2001年   34篇
  2000年   26篇
  1999年   19篇
  1998年   30篇
  1997年   27篇
  1996年   19篇
  1995年   76篇
  1994年   75篇
  1993年   51篇
  1992年   46篇
  1991年   41篇
  1990年   43篇
  1989年   37篇
  1988年   49篇
  1987年   40篇
  1986年   36篇
  1985年   19篇
  1984年   20篇
  1983年   24篇
  1982年   21篇
  1979年   15篇
  1919年   47篇
  1918年   44篇
  1917年   36篇
  1916年   53篇
  1915年   37篇
  1914年   71篇
  1913年   106篇
排序方式: 共有2805条查询结果,搜索用时 14 毫秒
91.
A 26 year old nulligravida presented at 24 weeks gestation for the second opinion of abnormal fetal profile and mid-face views on ultrasound at another institution. A detailed fetal anatomic ultrasound at our facility revealed the absence of fetal lens and globes bilaterally consistent with bilateral anophthalmia (HP: 0000528) without other anomalies. Karyotype and chromosomal microarray analysis were completed from amniocentesis sample. After these results, duo exome testing with paternal sequencing was completed from proband amniotic fluid sample and parental blood samples. A pathogenic variant in SOX2 (NM_003106.3: c.513C>G p.(Tyr171*Ter)) with heterozygous autosomal dominant inheritance resulted. On duo exome testing with paternal segregation analysis, the variant was found to be consistent with likely sporadic de novo inheritance. The SOX2 variant reported is consistent with the fetal phenotype in this case. While germline mosaicism could exist, this identified variant provided the family with a likely explanation for this proband's finding. This ultrasound and genetic testing allowed the family to make decisions related to planning in current and future pregnancies.  相似文献   
92.
93.
We investigated the global metabolite response to artificial selection for tolerance to stressful conditions such as cold, heat, starvation, and desiccation, and for longevity in Drosophila melanogaster. Our findings were compared to data from other levels of biological organization, including gene expression, physiological traits, and organismal stress tolerance phenotype. Overall, we found that selection for environmental stress tolerance changes the metabolomic 1H NMR fingerprint largely in a similar manner independent of the trait selected for, indicating that experimental evolution led to a general stress selection response at the metabolomic level. Integrative analyses across data sets showed little similarity when general correlations between selection effects at the level of the metabolome and gene expression were compared. This is likely due to the fact that the changes caused by these selection regimes were rather mild and/or that the dominating determinants for gene expression and metabolite levels were different. However, expression of a number of genes was correlated with the metabolite data. Many of the identified genes were general stress response genes that are down-regulated in response to selection for some of the stresses in this study. Overall, the results illustrate that selection markedly alters the metabolite profile and that the coupling between different levels of biological organization indeed is present though not very strong for stress selection at this level. The results highlight the extreme complexity of environmental stress adaptation and the difficulty of extrapolating and interpreting responses across levels of biological organization.  相似文献   
94.
This study analyzes the effectiveness and efficiency of the two principal United Nations (UN) climate change mitigation finance mechanisms, the Clean Development Mechanism (CDM) and the Global Environment Facility (GEF). The realised abatement and costs of the two mechanisms in India and Brazil (using data from 28 GEF and 233 CDM project documents) are compared with theoretical marginal abatement cost curves, based on bottom-up technology studies. We find that both mechanisms have focused on negative and low-cost abatement potential but still leave substantial theoretical potential in this cost range untapped. CDM has more effectively harvested abatement potential of industrial gases and methane emissions, whereas GEF has more successfully targeted demand-side energy efficiency (EE) and transport emission reduction opportunities. CDM has excelled at capturing abatement potential in areas with a limited understanding of abatement, highlighting the shortcomings of theoretical estimates (such as Marginal Abatement Cost Curves) and the benefits of a market mechanism. In some sectors and technologies (particularly renewable energy), the two mechanisms overlapped, which suggests a need for better coordination in the future.  相似文献   
95.
How best to optimize the biodiversity gain from agri-environment schemes (AES) has recently been identified as a key policy-relevant question. Here, the effects of two features of lowland agricultural landscapes on the abundance and diversity of larger moths are contrasted. Although both features bring about positive effects, hedgerow trees have a larger impact than 6 m wide grassy field margins. Whilst AES payments are given to create and maintain grass margins, no financial reward is currently offered for the retention of hedgerow trees. Furthermore, it was only in areas where the amount of land under AES was experimentally increased, by targeting farmers, that the presence of hedgerow trees resulted in a substantially higher abundance (+60%) and diversity (+38%) of moths. Thus, by using larger moths as bio-indicators of landscape-scale quality, it is demonstrated that improvements to the cost-effectiveness of AES could be achieved, firstly, by providing more appropriate financial rewards to farmers for different landscape features, and secondly, through landscape-scale targeting of farmers to encourage participation in AES.  相似文献   
96.
There are fears that global warming will lead to degradation of peatlands, higher emissions of greenhouse gases from peat, and accelerated warming. Anaerobic decomposition of organic soils produces methane (CH4), a potent greenhouse gas. Two peat bogs differing in mean annual temperature, Velke Darko (VD, Czech Republic, 7.2 °C), and Stor Åmyran (SA, Sweden, 4.0 °C), were selected for a comparative study of how organic soils in different climatic zones will respond to warmer and drier conditions. Twenty peat cores from each bog were incubated in growth chambers. Under present-day summer conditions, VD produced 14 times more CH4 than SA. Two different warming scenarios were used. Peat-core replicates were kept at temperatures of 11 versus 16 °C, and 11 versus 22 °C. From 11 to 16 °C, the CH4 production slightly decreased at SA, and slightly increased at VD. From 11 to 22 °C, the CH4 production increased 9 times at SA, but slightly decreased at VD. After an 8-month incubation, peat cores under drying conditions (water table at ?14 cm) were compared to samples with original water table (?2 cm). Drying conditions led to a steeper reduction in CH4 production at VD, compared to SA. The CH4 production decreased more than 100 times at VD. Then, the combined effect of simultaneous warming and drying at 11 and 22 °C was studied. We did not find any significant effect of interactions between increasing temperature and decreasing water table level. Overall, the warmer site VD responded more strongly to the simulated climate change than the colder site SA.  相似文献   
97.
Cytogenetic study of chorionic villi sampled because of advanced maternal age revealed, after overnight culture, an apparently non-mosaic trisomy 7. Amniocentesis showed exclusively normal mitoses, and the pregnancy continued normally. One hundred mitoses from cord blood of the normal newborn revealed a non-mosaic 46,XX complement. No cells with a proven trisomy 7 were found in cultures from either of two biopsies of the morphologically normal placenta, but the peripheral biopsy showed in multiple cultures an abnormal clone: 47,XX, + 20,-2,-21, + t(2;21)(p13;q22). To our knowledge, this is the first case of non-mosaic trisomy 7 detected on CVS which has had follow-up studies of amniotic fluid, cord blood, and term placenta.  相似文献   
98.
We report herein a de novo unbalanced chromosome translocation in a fetus resulting from in vitro fertilization technology. Prenatal diagnostic analysis of an amniotic fluid revealed a 46,XX,4p+ karyotype. The origin of the extra material on the short arm of chromosome 4 could not be identified by a variety of banding techniques. However, examination of fetal parts did reveal some dysmorphic features.  相似文献   
99.
The aim of this study was to determine whether there is increased leakage of neuron-specific enolase (NSE) and S-100 protein into amniotic fluid in pregnancies with neural tube defects, since both these proteins are produced by neural tissue, and to compare the value of these substances for detecting such defects with that of the more conventional techniques of alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) gel electrophoresis. Amniotic samples from 25 mid-pregnancies (15–17 weeks' gestation) with neural tube defects (14 with open spina bifida and 11 with anencephaly) and from seven mid-pregnancies with abdominal wall defects were compared with a control material consisting of 80 amniotic fluid samples from 80 consecutive mid-pregnancy amniocenteses, with normal karyotypes and AFP concentrations. All of the above cases of abnormalities were primarily detected through increased AFP levels in the amniotic fluid. Amniotic fluid samples from 13 pregnancies with fetuses with autosomal chromosomal abnormalities and seven amniotic fluid samples contaminated with blood were also included in the investigation. It is concluded from the results that the conventional AFP assay combined with AChE gel electrophoresis is the best method for screening amniotic fluid for neural tube defects and defects of the abdominal wall. Neither NSE nor S-100 assay alone proved to be superior for the detection of these cases in mid-trimester amniotic fluid. The S-100 assay, however, could give additional information in cases where AChE gel electrophoresis is not decisive; for example, in samples contaminated with blood.  相似文献   
100.
A case is presented in which percutaneous umbilical sampling (PUBS) was utilized in the second and third trimesters for the diagnosis and management of a pregnancy at risk for neonatal alloimmune thrombocytopenia (NAIT).  相似文献   
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