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   435篇
  免费   33篇
  国内免费   12篇
  2024年   2篇
  2023年   4篇
  2022年   10篇
  2021年   18篇
  2020年   14篇
  2019年   13篇
  2018年   9篇
  2017年   6篇
  2016年   3篇
  2015年   16篇
  2014年   18篇
  2013年   13篇
  2012年   14篇
  2011年   23篇
  2010年   25篇
  2009年   21篇
  2008年   19篇
  2007年   17篇
  2006年   14篇
  2005年   23篇
  2004年   11篇
  2003年   18篇
  2002年   15篇
  2001年   10篇
  2000年   8篇
  1999年   10篇
  1998年   11篇
  1997年   8篇
  1996年   7篇
  1995年   4篇
  1994年   5篇
  1993年   4篇
  1992年   11篇
  1991年   12篇
  1990年   7篇
  1989年   11篇
  1988年   5篇
  1987年   5篇
  1986年   5篇
  1985年   3篇
  1984年   7篇
  1983年   5篇
  1982年   6篇
  1981年   1篇
  1979年   1篇
  1978年   3篇
  1975年   2篇
  1973年   3篇
排序方式: 共有480条查询结果,搜索用时 62 毫秒
451.
This study objective is to validate a method for the measurement of two compound phantoms as a proof of concept for oxygen saturation level measurement via a thermal imaging bundle. The method consists of a thermal imaging system and an algorithm which estimates the compound concentration according to temperature rise. A temperature rise is obtained by illuminating the tissue with a laser with different wavelengths in the NIR range and measured using a thermal camera. A coherent thermal imaging bundle was used for image transmittance for minimal invasive transendoscopic use. The algorithm's estimation ability was evaluated using agar phantoms of varying Methylene Blue and ICG ratios as well as blood samples The Methylene Blue ratio in each phantom was estimated and the calculated average RMS of the error was 9.38%, a satisfying value for this stage, verifying the algorithm's and bundle's suitability for the use in a minimal invasive system. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
452.
453.
《Endocrine practice》2023,29(3):221-227
A better understanding of the molecular aberrations prevalent in thyroid cancers had led to significant advances in the management of advanced thyroid cancer. The landscape of thyroid cancer treatment has grown rapidly. Molecular profiling is the key to identify actionable targets for treatment of advanced disease. In the past decade, there have been regulatory approvals of 9 kinase inhibitors or kinase inhibitor combinations. There are now drugs approved for all of the different types of thyroid cancers, including anaplastic thyroid cancer. However, these drugs are not curative and therefore new strategies and treatments continue to be sought.  相似文献   
454.
《Neuron》2023,111(11):1732-1747.e6
  1. Download : Download high-res image (285KB)
  2. Download : Download full-size image
  相似文献   
455.
456.
Plants can detect pathogen invasion by sensing microbe‐associated molecular patterns (MAMPs). This sensing process leads to the induction of defense responses. Numerous MAMP mechanisms of action have been described in and outside the guard cells. Here, we describe the effects of chitin, a MAMP found in fungal cell walls and insects, on the cellular osmotic water permeability (Pf) of the leaf vascular bundle‐sheath (BS) and mesophyll cells (MCs), and its subsequent effect on leaf hydraulic conductance (Kleaf). BS is a parenchymatic tissue that tightly encases the vascular system. BS cells (BSCs) have been shown to influence Kleaf through changes in their Pf, for example, after sensing the abiotic stress response‐regulating hormone abscisic acid. It was recently reported that, in Arabidopsis, the chitin receptors‐like kinases, chitin elicitor receptor kinase 1 (CERK1) and LYSINE MOTIF RECEPTOR KINASE 5 (LYK5) are highly expressed in the BS as well as the neighboring mesophyll. Therefore, we studied the possible impact of chitin on these cells. Our results revealed that BSCs and MCs exhibit a sharp decrease in Pf in response to chitin treatment. In addition, xylem‐fed chitin decreased Kleaf and led to stomatal closure. However, Atlyk5 mutant showed none of these responses. Complementing AtLYK5 in the BSCs (using the SCARECROW promoter) resulted in the response to chitin that was similar to that observed in the wild‐type. These results suggest that BS play a role in the perception of apoplastic chitin and in initiating chitin‐triggered immunity.  相似文献   
457.
Extracellular fluid levels of dopamine and neurotensin in the rat prefrontal cortex were measured using in vivo microdialysis. Electrical stimulation of the median forebrain bundle resulted in increased release of both dopamine and neurotensin from the prefrontal cortex. Thus, stimulation of neurons in which dopamine and neurotensin are colocalized can evoke the in vivo release of both substances.  相似文献   
458.
《Genomics》2022,114(2):110302
The genetic origins of novelty are of central interest in evolutionary biology. ISG15 and UBA7 are present only in vertebrates. The emergence and evolution of them are not clear. Phylogenetic comparisons revealed that UBA7 descends from gene duplication, and ISG15 and UBA7 arose from UBB/UBC and UBA1, respectively. Uba7 exhibits ubiquitin-activation activity in fish but not tetrapods, suggesting that the relationship of ISG15/Uba7 was promiscuous in origin but was later coopted toward higher specificity. Zebrafish Uba7 is capable of activating the ubiquitin cascade in vitro and in vivo, and it displays distinct specificity preference toward substrates and E2 enzymes compared to zebrafish Uba1. These results together provide a framework for understanding the origin and diversification of ISG15/Uba7 and may serve as a paradigmatic example in which an originally minor functionality in an old gene is made into a new high-specificity protein through random mutations and natural selection.  相似文献   
459.
Renal cortex (C) has predominantly aerobic metabolism, whereas inner medulla (IM) has both aerobic and anaerobic capacities. This study was undertaken (1) to assess how well rat IM anaerobic metabolism maintains this region's ATP content during ischemia; and (2) to determine whether regional variations in adenylate pool/catabolite responses to ischemia exist, obscuring interpretation of cellular energetics in rat studies of acute renal failure (ARF). Adenine nucleotides/catabolites were measured in rat C, IM and outer medulla (OM) after 15 and 45 min of ischemia. After 15 min, all regions showed profound ATP depletion, although the IM maintained slightly higher (by 0.23 μmol/g) absolute ATP levels than C/OM tissues (normal ATP value = 8.7 μmol/g). By 45 min, significant differences in regional ATP levels did not exist. Striking regional catabolite differences were apparent at both 15 and 45 min. Most prominent were: (1) intrarenal purine base/inosine gradients, levels falling approx. 22–50% from C to IM; and (2) preferential OM AMP/IMP/adenosine accumulation. To assess whether more homogeneous results might be found in rabbit kidney, possibly making this animal preferable to rats for studies of renal ischemia, rabbit C, OM and IM adenylate pools were analyzed after 15 min of ischemia. C vs. IM ATP differences were greater (approx. 1.3 μmol/g) and large catabolite concentration differences were still apparent. Conclusions: (1) anaerobic mechanisms support IM ATP levels during ischemia but, in terms of normal concentrations, the impact is small, particularly in the rat; and (2) marked regional differences in adenylate catabolite levels exist within ischemic kidneys. These need to be recognized when analyzing adenylate pool responses in ischemic ARF.  相似文献   
460.
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