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   615篇
  免费   54篇
  669篇
  2023年   2篇
  2022年   5篇
  2021年   12篇
  2020年   7篇
  2019年   9篇
  2018年   15篇
  2017年   13篇
  2016年   23篇
  2015年   35篇
  2014年   21篇
  2013年   42篇
  2012年   36篇
  2011年   44篇
  2010年   21篇
  2009年   27篇
  2008年   40篇
  2007年   40篇
  2006年   35篇
  2005年   36篇
  2004年   27篇
  2003年   25篇
  2002年   19篇
  2001年   7篇
  2000年   6篇
  1999年   15篇
  1998年   8篇
  1997年   3篇
  1996年   2篇
  1995年   4篇
  1994年   2篇
  1993年   6篇
  1992年   10篇
  1991年   14篇
  1990年   11篇
  1989年   9篇
  1988年   6篇
  1987年   4篇
  1986年   3篇
  1985年   3篇
  1984年   6篇
  1982年   4篇
  1978年   1篇
  1976年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1961年   1篇
  1960年   1篇
  1954年   1篇
排序方式: 共有669条查询结果,搜索用时 15 毫秒
621.
With the objective to understand structural features responsible for the biological activity, novel nonelectrophilic biphenyl derivatives and peptide-biphenyl hybrids have been synthesized and evaluated as calpain I inhibitors. The preliminary results indicate that the presence of additional aromatic rings (besides the biphenyl system) makes these compounds potent calpain inhibitors with IC50 values in the nanomolar range.  相似文献   
622.
Plant Cell, Tissue and Organ Culture (PCTOC) - The high nutritional potential of native potatoes makes them an invaluable genetic resource for breeding. However, pathogens have caused both yield...  相似文献   
623.
624.
625.

Rheological and textural characteristics of cookie doughs were measured to characterise the effect of two microalgae biomasses additions (Arthrospira platensis and Chlorella vulgaris) in 3D printed cookies. The rheological characteristics determined the addition of microalgae lead to a greater mechanical resistance and a predominance of the elastic component ahead of the viscous component, this behaviour was confirmed by the textural analysis that showed a greater force for the extrusion of microalgae-enriched doughs. Besides, the influence of processing parameters, including filament diameter (26 and 27 mm) and layer height (1.3 and 1.5 mm), on the geometric accuracy of a 3D printed food structure made of cookie dough before and after baking process, was evaluated. The addition of microalgae biomass in dough, for 3D printed cookies, improves the printability in terms of dimensional properties, achieving 3D structures more stable and resistant to baking.

  相似文献   
626.
Soil-Transmitted Helminths (STH) are highly prevalent Neglected Tropical Disease in Ethiopia, an estimated 26 million are infected. Geographic Information Systems and Remote Sensing (RS) technologies assist data mapping and analysis, and the prediction of the spatial distribution of infection in relation to environmental variables. The influence of socioeconomic, environmental and soil characteristics on hookworm infection at the individual and household level is explored in order to identify spatial patterns of infection in rural villages from Zenzelema (Amhara region). Inhabitants greater than 5 years old were recruited in order to assess the presence of STH. Socioeconomic and hookworm infection variables at the household level and environmental variables and soil characteristics using RS were obtained. The dominant STH found was hookworm. Individuals which practiced open defecation and those without electricity had a significant higher number of hookworm eggs in their stool. Additionally, adults showed statistically higher hookworm egg counts than children. Nonetheless, the probability of hookworm infection was not determined by socioeconomic conditions but by environmental characteristics surrounding the households, including a combination of vigorous vegetation and bare soil, high temperatures, and compacted soils (high bulk density) with more acidic pH, given a pH of 6.0 is optimal for hatching of hookworm eggs. The identification of high-risk environmental areas provides a useful tool for planning, targeting and monitoring of control measures, including not only children but also adults when hookworm is concerned.  相似文献   
627.
N‐glycosylation is critical for recombinant glycoprotein production as it influences the heterogeneity of products and affects their biological function. In most eukaryotes, the oligosaccharyltransferase is the central‐protein complex facilitating the N‐glycosylation of proteins in the lumen of the endoplasmic reticulum (ER). Not all potential N‐glycosylation sites are recognized in vivo and the site occupancy can vary in different expression systems, resulting in underglycosylation of recombinant glycoproteins. To overcome this limitation in plants, we expressed LmSTT3D, a single‐subunit oligosaccharyltransferase from the protozoan Leishmania major transiently in Nicotiana benthamiana, a well‐established production platform for recombinant proteins. A fluorescent protein‐tagged LmSTT3D variant was predominately found in the ER and co‐located with plant oligosaccharyltransferase subunits. Co‐expression of LmSTT3D with immunoglobulins and other recombinant human glycoproteins resulted in a substantially increased N‐glycosylation site occupancy on all N‐glycosylation sites except those that were already more than 90% occupied. Our results show that the heterologous expression of LmSTT3D is a versatile tool to increase N‐glycosylation efficiency in plants.  相似文献   
628.
1. Hypertension can be induced by some types of stress in the rat. The aim of the present work was to study the putative implication of brain norepinephrine (NE) in blood pressure increase due to social deprivation stress. 2. The effects of 6-hydroxydopamine (6-OHDA) lesions of the ventral noradrenergic bundle (VNEB) on the hypertensive response induced by brief social deprivation stress in young Wistar rats were examined. NE, dopamine (DA), and epinephrine (EPI) levels were measured by HPLC coupled with electrochemical detection in two brain areas (hypothalamus and medulla oblongata) relevant for blood pressure regulation. 3. VNEB lesions prevented the hypertensive response produced by isolation. Twelve or 20 days after 6-OHDA administration, NE and EPI but not DA levels decreased in the hypothalamus of the lesioned rats. In contrast, no catecholamine changes were detected in medulla oblongata. 4. These data suggest that the VNEB plays a role in the triggering of the hypertensive response induced by social deprivation stress in young Wistar rats.  相似文献   
629.
Studies on temperature–mortality time trends especially address heat, so that any contribution on the subject of cold is necessarily of interest. This study describes the modification of the lagged effects of cold on mortality in Castile-La Mancha from 1975 to 2003, with the novelty of also approaching this aspect in terms of mortality trigger thresholds. Cross-correlation functions (CCFs) were thus established with 15 lags, after application of ARIMA models to the mortality data and minimum daily temperatures (from November to March), and the results for the periods 1975–1984, 1985–1994 and 1995–2003 were then compared. In addition, daily mortality residuals for the periods 1975–1989 and 1990–2003 were related to minimum temperatures grouped in 2°C intervals, with a cold threshold temperature being obtained in cases where such residuals increased significantly (p < 0.05) with respect to the mean for the study period. A cold-related mortality trigger threshold of −3°C was obtained for Ciudad Real for the period 1990–2003. The significant number of lags (p < 0.05) in the CCFs declined every 10 years in Toledo (5–2–0), Cuenca (4–2–0), Albacete (4–3–0) and Ciudad Real (3–2–1). This meant that, while the trend in cold-related mortality trigger thresholds in the region could not be ascertained, it was possible to establish a reduction in the lagged effects of cold on mortality, attributable to the improvement in socio-economic conditions over the study period. Evidence was shown of the effects of cold on mortality, a finding that renders the adoption of preventive measures advisable in any case where intense cold is forecast.  相似文献   
630.
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