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   2777篇
  免费   281篇
  国内免费   1篇
  2023年   18篇
  2022年   36篇
  2021年   78篇
  2020年   63篇
  2019年   62篇
  2018年   68篇
  2017年   67篇
  2016年   95篇
  2015年   144篇
  2014年   162篇
  2013年   193篇
  2012年   227篇
  2011年   206篇
  2010年   116篇
  2009年   120篇
  2008年   151篇
  2007年   137篇
  2006年   137篇
  2005年   125篇
  2004年   102篇
  2003年   120篇
  2002年   96篇
  2001年   46篇
  2000年   36篇
  1999年   30篇
  1998年   28篇
  1997年   18篇
  1996年   14篇
  1995年   21篇
  1994年   15篇
  1993年   9篇
  1992年   25篇
  1991年   17篇
  1990年   16篇
  1989年   15篇
  1988年   10篇
  1987年   16篇
  1986年   16篇
  1985年   20篇
  1984年   20篇
  1983年   6篇
  1981年   11篇
  1980年   14篇
  1979年   7篇
  1978年   12篇
  1974年   10篇
  1879年   6篇
  1878年   14篇
  1877年   14篇
  1876年   13篇
排序方式: 共有3059条查询结果,搜索用时 15 毫秒
51.
The International Journal of Life Cycle Assessment - This study has two aims: first, propose the use of the driver-pressure-state-impact-response (DPSIR) framework to expand the normal focus of...  相似文献   
52.
53.
Journal of Ethology - Noise pollution may impair the cognitive performances of several animal species, producing suboptimal behavioral responses. Involuntary shifts in attention from noise...  相似文献   
54.
55.
Highlights? Transformation-associated glucose shortage triggers ER stress ? The ER stress acts as barrier to malignancy by triggering UPR-dependent apoptosis ? p58IPK expression removes the UPR barrier by attenuating its PERK-CHOP branch ? This adaptive mechanism enables implementation of UPR cytoprotective features  相似文献   
56.
A retrospective cohort study was conducted on 1541 HIV-infected patients to determine variables associated with the incidence of herpes zoster. A single failure Cox model showed that herpes zoster incidence increased following the first 6 months of antiretroviral treatment adjusted hazard ratio (AHR)=5 (95%CI=2.6-9.2), P<0.001; in the >60 years age group AHR=2 (95%CI=1-4), P=0.04; in patients in the top CD8 quartile AHR=2.1 (95%CI=1.3-3.6), P<0.001; and in patients previously reported to use crack cocaine AHR=5.9, (95%CI=1.4-25), P=0.02. Herpes zoster incidence increased in patients with CD4 counts<500 per mm3 and gradually declined since 1992-1996, with AHR=0.3 (95%CI=0.2-0.5), P<0.001 for the 1997-2002 period and AHR=0.24 (95%CI=0.14-0.4), P<0.001 for the 2002-2008 period. Contrary to what has been described elsewhere, there was no specific effect of protease inhibitors on herpes zoster incidence. The present study is the first to suggest that crack cocaine is associated with an increased incidence of herpes zoster. The neurological or immunological effects of crack are discussed.  相似文献   
57.
58.
Impairments in flexible goal-directed decisions, often examined by reversal learning, are associated with behavioral abnormalities characterized by impulsiveness and disinhibition. Although the lateral orbital frontal cortex (OFC) has been consistently implicated in reversal learning, it is still unclear whether this region is involved in negative feedback processing, behavioral control, or both, and whether reward and punishment might have different effects on lateral OFC involvement. Using a relatively large sample (N = 47), and a categorical learning task with either monetary reward or moderate electric shock as feedback, we found overlapping activations in the right lateral OFC (and adjacent insula) for reward and punishment reversal learning when comparing correct reversal trials with correct acquisition trials, whereas we found overlapping activations in the right dorsolateral prefrontal cortex (DLPFC) when negative feedback signaled contingency change. The right lateral OFC and DLPFC also showed greater sensitivity to punishment than did their left homologues, indicating an asymmetry in how punishment is processed. We propose that the right lateral OFC and anterior insula are important for transforming affective feedback to behavioral adjustment, whereas the right DLPFC is involved in higher level attention control. These results provide insight into the neural mechanisms of reversal learning and behavioral flexibility, which can be leveraged to understand risky behaviors among vulnerable populations.  相似文献   
59.
Cholangiocacinoma (CC) is a cancer disease with rising incidence. Notch signaling has been shown to be deregulated in many cancers. However, the role of this signaling pathway in the carcinogenesis of CC is still not fully explored. In this study, we investigated the effects of Notch inhibition by γ-secretase inhibitor IX (GSI IX) in cultured human CC cell lines and we established a transgenic mouse model with liver specific expression of the intracellular domain of Notch (Notch-ICD) and inactivation of tumor suppressor p53. GSI IX treatment effectively impaired cell proliferation, migration, invasion, epithelial to mesenchymal transition and growth of softagar colonies. In vivo overexpression of Notch-ICD together with an inactivation of p53 significantly increased tumor burden and showed CC characteristics. Conclusion: Our study highlights the importance of Notch signaling in the tumorigenesis of CC and demonstrates that additional inactivation of p53 in vivo.  相似文献   
60.
Noma (cancrum oris) is a gangrenous disease of unknown etiology affecting the maxillo-facial region of young children in extremely limited resource countries. In an attempt to better understand the microbiological events occurring during this disease, we used phylogenetic and low-density microarrays targeting the 16S rRNA gene to characterize the gingival flora of acute noma and acute necrotizing gingivitis (ANG) lesions, and compared them to healthy control subjects of the same geographical and social background. Our observations raise doubts about Fusobacterium necrophorum, a previously suspected causative agent of noma, as this species was not associated with noma lesions. Various oral pathogens were more abundant in noma lesions, notably Atopobium spp., Prevotella intermedia, Peptostreptococcus spp., Streptococcus pyogenes and Streptococcus anginosus. On the other hand, pathogens associated with periodontal diseases such as Aggregatibacter actinomycetemcomitans, Capnocytophaga spp., Porphyromonas spp. and Fusobacteriales were more abundant in healthy controls. Importantly, the overall loss of bacterial diversity observed in noma samples as well as its homology to that of ANG microbiota supports the hypothesis that ANG might be the immediate step preceding noma.  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