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   224篇
  免费   12篇
  236篇
  2021年   2篇
  2020年   5篇
  2019年   4篇
  2018年   17篇
  2017年   13篇
  2016年   22篇
  2015年   8篇
  2014年   9篇
  2013年   12篇
  2012年   15篇
  2011年   21篇
  2010年   18篇
  2009年   13篇
  2008年   14篇
  2007年   14篇
  2006年   8篇
  2005年   6篇
  2004年   6篇
  2003年   3篇
  2002年   5篇
  2001年   4篇
  2000年   3篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1995年   1篇
  1994年   1篇
  1992年   1篇
  1988年   1篇
  1979年   1篇
  1974年   1篇
  1969年   1篇
  1947年   1篇
排序方式: 共有236条查询结果,搜索用时 15 毫秒
41.
Mitochondria are sub-cellular organelles that produce adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS). As suggested over 70 years ago by Otto Warburg and recently confirmed with molecular techniques, alterations in respiratory activity and in mitochondrial DNA (mtDNA) appear to be common features of malignant cells. Somatic mtDNA mutations have been reported in many types of cancer cells, and some reports document the prevalence of inherited mitochondrial DNA polymorphisms in cancer patients. Nevertheless, a careful reanalysis of methodological criteria and methodology applied in those reports has shown that numerous papers can't be used as relevant sources of data for systematic review, meta-analysis, or finally for establishment of clinically applicable markers.  相似文献   
42.
43.
Extremophiles - By applying the culturomics concept and using culture conditions containing a high salt concentration, we herein isolated the first known halophilic archaeon colonizing the human...  相似文献   
44.
45.
The emergence of stretchable textile‐based mechanical energy harvester and self‐powered active sensor brings a new life for wearable functional electronics. However, single energy conversion mode and weak sensing capabilities have largely hindered their development. Here, in virtue of silver‐coated nylon yarn and silicone rubber elastomer, a highly stretchable yarn‐based triboelectric nanogenerator (TENG) with coaxial core–sheath and built‐in spring‐like spiral winding structures is designed for biomechanical energy harvesting and real‐time human‐interactive sensing. Based on the two advanced structural designs, the yarn‐based TENG can effectively harvest or respond rapidly to omnifarious external mechanical stimuli, such as compressing, stretching, bending, and twisting. With these excellent performances, the yarn‐based TENG can be used in a self‐counting skipping rope, a self‐powered gesture‐recognizing glove, and a real‐time golf scoring system. Furthermore, the yarn‐based TENG can also be woven into a large‐area energy‐harvesting fabric, which is capable of lighting up light emitting diodes (LEDs), charging a commercial capacitor, powering a smart watch, and integrating the four operational modes of TENGs together. This work provides a new direction for textile‐based multimode mechanical energy harvesters and highly sensitive self‐powered motion sensors with potential applications in sustainable power supplies, self‐powered wearable electronics, personalized motion/health monitoring, and real‐time human‐machine interactions.  相似文献   
46.
Rhaponticum carthamoides transformed root extract induces double strand DNA damage by increasing the number of phosphorylated H2A.X- and cleaved PARP1-positive U87MG cells and patient-derived IV grade glioma cells. Furthermore, treatment of these cells with root extract causes down-regulation of UHRF1 and DNMT1. Transformed root extract is rich in caffeoylquinic acid derivatives, especially tricaffeoylquinic acid derivatives. Our findings demonstrate that the R. carthamoides transformed root extract may trigger apoptosis in glioma cells by induction of DNA damage, PARP cleavage and epigenetic modification.  相似文献   
47.
We report synthesis of silver nanoparticles (AgNPs) from Streptomyces xinghaiensis OF1 strain, which were characterised by UV–Vis and Fourier transform infrared spectroscopy, Zeta sizer, Nano tracking analyser, and Transmission electron microscopy. The antimicrobial activity of AgNPs alone, and in combination with antibiotics was evaluated against bacteria, namely Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis, and yeasts viz., Candida albicans and Malassezia furfur by using micro-dilution method. The minimum inhibitory concentration (MIC) and minimum biocidal concentration of AgNPs against bacterial and yeast strains were determined. Synergistic effect of AgNPs in combination with antibacterial and antifungal antibiotics was determined by FIC index. In addition, MTT assay was performed to study cytotoxicity of AgNPs alone and in combination with antibiotics against mouse fibroblasts and HeLa cell line. Biogenic AgNPs were stable, spherical, small, polydispersed and capped with organic compounds. The variable antimicrobial activity of AgNPs was observed against tested bacteria and yeasts. The lowest MIC (16 µg ml?1) of AgNPs was found against P. aeruginosa, followed by C. albicans and M. furfur (both 32 µg ml?1), B. subtilis and E. coli (both 64 µg ml?1), and then S. aureus and Klebsiella pneumoniae (256 µg ml?1). The high synergistic effect of antibiotics in combination with AgNPs against tested strains was found. The in vitro cytotoxicity of AgNPs against mouse fibroblasts and cancer HeLa cell lines revealed a dose dependent potential. The IC50 value of AgNPs was found in concentrations of 4 and 3.8 µg ml?1, respectively. Combination of AgNPs and antibiotics significantly decreased concentrations of both antimicrobials used and retained their high antibacterial and antifungal activity. The synthesis of AgNPs using S. xinghaiensis OF1 strain is an eco-friendly, cheap and nontoxic method. The antimicrobial activity of AgNPs could result from their small size. Remarkable synergistic effect of antibiotics and AgNPs offer their valuable potential in nanomedicine for clinical application as a combined therapy in the future.  相似文献   
48.
49.
The arms race between Maculinea butterflies and Myrmica host ants leads to local host-parasite adaptations. In our study, we assessed whether sympatric and allopatric Myrmica scabrinodis populations exhibit behavioural differences towards Maculinea teleius larvae during the adoption-period when butterfly larvae need to be taken inside the Myrmica nest. The second aim was to assess the butterfly survival rate inside ant colonies from different populations. We used one sympatric host population and three allopatric populations: one infested by M. teleius and two uninfested populations. We found that ants from the sympatric population showed a higher number of positive behaviours toward M. teleius larvae during adoption than ants from the allopatric populations. There were no differences in the number of inspection or negative behaviour events. The survival of butterfly larvae was highest inside sympatric host colonies and differed from the survival of M. teleius reared by ants from the allopatric, uninfested populations. No difference was found for the survival rate of M. teleius raised by infested, allopatric host colonies compared to sympatric host populations. Our results suggest the lack of behavioural counter-adaptations of local hosts of M. teleius that more easily adopt and rear butterfly caterpillars compared to naive M. scabrinodis colonies. Our results may also have implications for Maculinea butterfly conservation, especially for reintroduction programmes. We suggest that the existence of behavioural host defences should be checked for the source host population, as well as for the Myrmica population from the reintroduction site. It may also be reasonable to introduce several Myrmica host colonies from the source butterfly host population.  相似文献   
50.
This paper investigates the effect of temperature on nitrogen and carbon removal by aerobic granules from landfill leachate with a high ammonium concentration and low concentration of biodegradable organics. The study was conducted in three stages; firstly the operating temperature of the batch reactor with aerobic granules was maintained at 29 °C, then at 25 °C, and finally at 20 °C. It was found that a gradual decrease in operational temperature allowed the nitrogen-converting community in the granules to acclimate, ensuring efficient nitrification even at ambient temperature (20 °C). Ammonium was fully removed from leachate regardless of the temperature, but higher operational temperatures resulted in higher ammonium removal rates [up to 44.2 mg/(L h) at 29 °C]. Lowering the operational temperature from 29 to 20 °C decreased nitrite accumulation in the GSBR cycle. The highest efficiency of total nitrogen removal was achieved at 25 °C (36.8 ± 10.9 %). The COD removal efficiency did not exceed 50 %. Granules constituted 77, 80 and 83 % of the biomass at 29, 25 and 20 °C, respectively. Ammonium was oxidized by both aerobic and anaerobic ammonium-oxidizing bacteria. Accumulibacter sp., Thauera sp., cultured Tetrasphaera PAO and AzoarcusThauera cluster occurred in granules independent of the temperature. Lower temperatures favored the occurrence of denitrifiers of Zooglea lineage (not Z. resiniphila), bacteria related to Comamonadaceae, Curvibacter sp., Azoarcus cluster, Rhodobacter sp., Roseobacter sp. and Acidovorax spp. At lower temperatures, the increased abundance of denitrifiers compensated for the lowered enzymatic activity of the biomass and ensured that nitrogen removal at 20 °C was similar to that at 25 °C and significantly higher than removal at 29 °C.  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