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   687篇
  免费   40篇
  国内免费   81篇
  808篇
  2024年   9篇
  2023年   19篇
  2022年   23篇
  2021年   41篇
  2020年   42篇
  2019年   54篇
  2018年   30篇
  2017年   21篇
  2016年   20篇
  2015年   40篇
  2014年   60篇
  2013年   46篇
  2012年   68篇
  2011年   47篇
  2010年   40篇
  2009年   25篇
  2008年   38篇
  2007年   32篇
  2006年   24篇
  2005年   14篇
  2004年   18篇
  2003年   8篇
  2002年   12篇
  2001年   3篇
  2000年   9篇
  1999年   12篇
  1998年   9篇
  1997年   10篇
  1996年   6篇
  1995年   4篇
  1994年   5篇
  1993年   4篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   2篇
  1987年   3篇
  1985年   3篇
  1983年   1篇
  1978年   1篇
排序方式: 共有808条查询结果,搜索用时 15 毫秒
61.
Serum levels of C-reactive proteins (CRP), Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), total protein, albumin and globulins were investigated using high sensitivity Immunoturbidometric and colorimetric techniques in individuals with hepatitis (n=50), Malaria (n=50) and 40 control subjects in age range of 30 to 65 years. The hepatitis patients had a significantly higher (P < 0.01) level of aminotransferases when compared to malaria patients and control subjects. The mean value of ALT was 103.50 ± 71.4 IU/L and 46.72 ±17.48 IU/L for hepatitis and malaria respectively. The values for AST were 116.76 ± 63.27 IU/L and 57.74 IU/L ± 15.18 IU/L for hepatitis and malaria respectively while the values for control were 34.75 ± 14.64 and 35.25 ± 15.56 IU/L for AST and ALT respectively. The malaria patients showed a significantly higher level (P < 0.01) of aminotransferases when compared to the control. The mean serum CRP levels were 0.71 ± 0.11 mg/dL and 0.78 ± 0.13 mg/dL for hepatitis and malaria respectively. These values were significantly higher (P < 0.01) than those of the controls which was 0.32 ± 0.12 mg/dL. The values of CRP in malaria were significantly higher (P< 0.05) when compared with hepatitis. In malaria, AST correlated with CRP (r = 0.58). The mean serum proteins of hepatitis patients were significantly lower (P < 0.05) than those of the control and malaria while there were no significant differences between the total protein in malaria when compared with control. Albumin levels in both patients were significantly lower (P > 0.05) than those of the controls. The mean values were 33.40 ± 3.40g/L and 34.47 ± 3.56g/L for hepatitis and malaria respectively and 37.00 ± 3.43 g/L for the control. C-reactive protein correlated negatively with albumin in malaria (r = -0.26) while albumin had a negative correlation with globulin(r = -0.36). Also albumin-globulin ratio were significantly (P < 0.05) decreased in both patients when compared with controls. This result suggests that a systemic acute phase response is present in hepatitis and malaria patients hence measurement of C-reactive proteins may be helpful in the diagnosis and management of hepatitis and malaria; especially in the malaria endemic region such as Nigeria. Keywords: Hepatitis B, Malaria, C-reactive protein, Liver function tests.  相似文献   
62.
63.
Regulation of microtubule dynamics at the cell cortex is important for cell motility, morphogenesis and division. Here we show that the Drosophila katanin Dm-Kat60 functions to generate a dynamic cortical-microtubule interface in interphase cells. Dm-Kat60 concentrates at the cell cortex of S2 Drosophila cells during interphase, where it suppresses the polymerization of microtubule plus-ends, thereby preventing the formation of aberrantly dense cortical arrays. Dm-Kat60 also localizes at the leading edge of migratory D17 Drosophila cells and negatively regulates multiple parameters of their motility. Finally, in vitro, Dm-Kat60 severs and depolymerizes microtubules from their ends. On the basis of these data, we propose that Dm-Kat60 removes tubulin from microtubule lattice or microtubule ends that contact specific cortical sites to prevent stable and/or lateral attachments. The asymmetric distribution of such an activity could help generate regional variations in microtubule behaviours involved in cell migration.  相似文献   
64.
To A  Bai Y  Shen A  Gong H  Umamoto S  Lu S  Liu F 《PloS one》2011,6(4):e17796
Human cytomegalovirus (HCMV) is the largest human herpesvirus and its virion contains many viral encoded proteins found in the capsid, tegument, and envelope. In this study, we carried out a yeast two-hybrid (YTH) analysis to study potential binary interactions among 56 HCMV-encoded virion proteins. We have tested more than 3,500 pairwise combinations for binary interactions in the YTH analysis, and identified 79 potential interactions that involve 37 proteins. Forty five of the 79 interactions were also identified in human cells expressing the viral proteins by co-immunoprecipitation (co-IP) experiments. To our knowledge, 58 of the 79 interactions revealed by YTH analysis, including those 24 that were also identified in co-IP experiments, have not been reported before. Novel potential interactions were found between viral capsid proteins and tegument proteins, between tegument proteins, between tegument proteins and envelope proteins, and between envelope proteins. Furthermore, both the YTH and co-IP experiments have identified 9, 7, and 5 interactions that were involved with UL25, UL24, and UL89, respectively, suggesting that these "hub" proteins may function as the organizing centers for connecting multiple virion proteins in the mature virion and for recruiting other virion proteins during virion maturation and assembly. Our study provides a framework to study potential interactions between HCMV proteins and investigate the roles of protein-protein interactions in HCMV virion formation or maturation process.  相似文献   
65.
Differentiation of pluripotent stem cells is tightly controlled by temporal and spatial regulation of multiple key signaling pathways. One of the hurdles to its understanding has been the varied methods in correlating changes of key signaling events to differentiation efficiency. We describe here the use of a mouse embryonic stem (ES) cell based assay to identify critical time windows for Wnt/β-catenin and BMP signal activation during cardiogenic induction. By scoring for contracting embryonic bodies (EBs) in a 96-well plate format, we can quickly quantify cardiogenic efficiency and identify crucial time windows for Wnt/β-catenin and BMP signal activation in a time course following specific modulator treatments. The principal outlined here is not limited to cardiac induction alone, and can be applied towards the study of many other cell lineages. In addition, the 96-well format has the potential to be further developed as a high throughput, automated assay to allow for the testing of more sophisticated experimental hypotheses.  相似文献   
66.
The practical use of Zn metal anodes in aqueous zinc batteries is impeded by the growth of dendrites, anode corrosion, and hydrogen evolution reaction in aqueous electrolytes. In this study, a simple, energy-efficient, and scalable approach is reported to mitigate these detrimental issues effectively. Using 1-hexanethiol (HT), a hydrophobic self-assembled mercaptan layer (SAML) with a highly ordered structure is in situ created on the surface of the Zn anode. This ultrathin interfacial structure guides uniform Zn deposition and shields the Zn anode from water and oxygen-induced corrosion, thus effectively inhibiting dendrite formation and side reactions. Consequently, the HT-Zn electrode showcases impressive electrochemical stability and reversibility, and the as-assembled HT-Zn||I2 full cell delivers increased specific capacity (from 112 to 155 mAh g−1 at 1 A g−1) and ultra-stable cyclability (zero capacity decay during the extended 1500 cycles at 4 A g−1). To validate the effectiveness of this simple and scalable method, a large-sized pouch cell is prepared, which can be stably operated for 1000 cycles with a capacity decay of merely 0.0098% per cycle and Coulombic efficiency exceeding 99.1%. The presented SAML strategy highlights the potential of molecular engineering in improving the performance of aqueous zinc batteries.  相似文献   
67.
The heterodimerization of WT Cu, Zn superoxide dismutase-1 (SOD1), and mutant SOD1 might be a critical step in the pathogenesis of SOD1-linked amyotrophic lateral sclerosis (ALS). Rates and free energies of heterodimerization (ΔGHet) between WT and ALS-mutant SOD1 in mismatched metalation states—where one subunit is metalated and the other is not—have been difficult to obtain. Consequently, the hypothesis that under-metalated SOD1 might trigger misfolding of metalated SOD1 by “stealing” metal ions remains untested. This study used capillary zone electrophoresis and mass spectrometry to track heterodimerization and metal transfer between WT SOD1, ALS-variant SOD1 (E100K, E100G, D90A), and triply deamidated SOD1 (modeled with N26D/N131D/N139D substitutions). We determined that rates of subunit exchange between apo dimers and metalated dimers—expressed as time to reach 30% heterodimer—ranged from t30% = 67.75 ± 9.08 to 338.53 ± 26.95 min; free energies of heterodimerization ranged from ΔGHet = -1.21 ± 0.31 to -3.06 ± 0.12 kJ/mol. Rates and ΔGHet values of partially metalated heterodimers were more similar to those of fully metalated heterodimers than apo heterodimers, and largely independent of which subunit (mutant or WT) was metal-replete or metal-free. Mass spectrometry and capillary electrophoresis demonstrated that mutant or WT 4Zn-SOD1 could transfer up to two equivalents of Zn2+ to mutant or WT apo-SOD1 (at rates faster than the rate of heterodimerization). This result suggests that zinc-replete SOD1 can function as a chaperone to deliver Zn2+ to apo-SOD1, and that WT apo-SOD1 might increase the toxicity of mutant SOD1 by stealing its Zn2+.  相似文献   
68.
Measuring chlorophyll fluorescence and P700 absorbance has been widely used to study photosynthesis in both terrestrial plants and algae. However, in order to apply these measurement techniques to study microalgae, a concentrated suspension of algae, which is usually prepared by centrifugation, is required. In this study, instead of using centrifugation, we concentrated microalgae on a nitrocellulose membrane using filtration to create an ‘artificial leaf’ before analysis. Overall, we were able to generate values of the appropriate photosynthetic parameters that were comparable to those obtained when chlorophyll fluorescence and P700 absorbance were measured following centrifugation. There were no statistically significant differences (P > 0.05) between the artificial leaf method and the traditional cuvette method for determining chlorophyll fluorescence or P700 absorbance at appropriate chlorophyll concentrations. We were also able to reduce background noise by using a filter membrane as a carrier. Therefore, an artificial leaf has the potential to be a valuable tool for phycologists interested in studying microalgal photosynthesis by enabling them to eliminate tedious centrifugation steps. In addition, fluorometers commonly used for studying the leaves of higher plants will also be suitable for studying microalgae.  相似文献   
69.
70.
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