全文获取类型
收费全文 | 367篇 |
免费 | 25篇 |
国内免费 | 15篇 |
专业分类
407篇 |
出版年
2024年 | 1篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 5篇 |
2019年 | 12篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 19篇 |
2014年 | 25篇 |
2013年 | 24篇 |
2012年 | 31篇 |
2011年 | 20篇 |
2010年 | 23篇 |
2009年 | 15篇 |
2008年 | 32篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 17篇 |
2004年 | 8篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1978年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有407条查询结果,搜索用时 15 毫秒
31.
Christina B. Madsen-Duggan John S. Debenham Thomas F. Walsh Lin Yan Pei Huo Junying Wang Xinchun Tong Julie Lao Tung M. Fong Jing Chen Xiao Cathy R.-R.C. Huang Chun-Pyn Shen D.Sloan Stribling Lauren P. Shearman Alison M. Strack Mark T. Goulet Jeffrey J. Hale 《Bioorganic & medicinal chemistry letters》2010,20(12):3750-3754
Synthesis and structure–activity relationships of cannabinoid-1 receptor (CB1R) inverse agonists based on dihydro-pyrano[2,3-b] pyridine and tetrahydro-1,8-naphtyridine scaffolds are presented. Rat food intake and pharmacokinetic evaluation of 13g, 13i, 13k and 17a revealed these compounds to be highly efficacious orally active modulators of CB1R. 相似文献
32.
33.
Ren TH Wu J Yew D Ziea E Lao L Leung WK Berman B Hu PJ Sung JJ 《American journal of physiology. Gastrointestinal and liver physiology》2007,292(3):G849-G856
Early life stress has been implicated as a risk factor for irritable bowel syndrome (IBS). We studied the effect of neonatal maternal separation on the visceromotor response and the expression of c-fos, 5-HT, and its receptors/transporters along the brain-gut axis in an animal model of IBS. Male neonatal Sprague-Dawley rats were randomly assigned to a 3-h daily maternal separation (MS) or nonhandling (NH) on postnatal days 2-21. Colorectal balloon distention (CRD) was performed for assessment of abdominal withdrawal reflex as a surrogate marker of visceral pain. Tissues from dorsal raphe nucleus in midbrain, lumbar-sacral cord, and distal colon were harvested for semiquantitative analysis of c-fos and 5-HT. The expression of 5-HT expression, 5-HT3 receptors, and 5-HT transporter were analyzed by RT-PCR. Pain threshold was significantly lower in MS than NH rats. The abdominal withdrawal reflex score in response to CRD in MS rats was significantly higher with distension pressures of 40, 60, and 80 mmHg. In MS rats, the number of c-fos-like immunoreactive nuclei at dorsal horn of lumbar-sacral spinal cord increased significantly after CRD. 5-HT content in the spinal cord of MS rats was significant higher. In the colon, both 5-HT-positive cell number and 5-HT content were comparable between MS and NH groups before CRD. Post-CRD only MS rats had significant increase in 5-HT content. Protein and mRNA expression levels of 5-HT3 receptors and 5-HT transporter were similar in MS and NH rats. Neonatal maternal separation stress predisposes rats to exaggerated neurochemical responses and visceral hyperalgesia in colon mimicking IBS. 相似文献
34.
Modification of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) film by chemical graft copolymerization
The graft copolymerization of 2-hydroxyethylmethacrylate (HEMA) onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) films has been investigated. The graft copolymerization was conducted in aqueous media using benzoyl peroxide (BPO) as chemical initiator. PHBHV films were prepared by solvent casting. Different parameters affecting the graft yield were studied such as monomer concentration, initiator concentration, and reaction time. The extent of grafting has been modulated by the preparation conditions, in particular the concentration of HEMA. However, it is interesting to note that the initiator concentration had only a slight influence on the graft yield. Characterization of the grafted PHBHV films assumed that the graft copolymerization not only occurred on the film surface but also took place into the film bulk. Differential scanning calorimetry showed that crystallinity dramatically decreased with increasing graft yield, indicating that graft copolymerization hindered the crystallization process. Wettability has been obviously improved by grafting a hydrophilic monomer such as HEMA for high graft yield (>130%). 相似文献
35.
Fu H Li W Liu Y Lao Y Liu W Chen C Yu H Lee NT Chang DC Li P Pang Y Tsim KW Li M Han Y 《Journal of proteome research》2007,6(7):2435-2446
Increasing evidence supports that the mitochondrial dysfunction, mainly caused by abnormal changes in mitochondrial proteins, plays a pivotal role in glutamate-induced excitotoxicity, which is closely associated with the pathogenesis of acute and chronic neurodegenerative disorders, such as stroke and Alzheimer's disease. In this study, post-treatment of cerebellar granule neurons with bis(7)-tacrine significantly reversed declines in mitochondrial membrane potential, ATP production, and neuronal cell death induced by glutamate. Moreover, this reversal was independent of NMDA antagonism, acetylcholinesterase inhibition, and cholinergic pathways. Using two-dimensional differential in-gel electrophoresis, we conducted a comparative analysis of mitochondrial protein patterns. In all, 29 proteins exhibiting significant differences in their abundances were identified in the glutamate-treated group when compared with the control. The expression patterns in 22 out of these proteins could be reversed by post-treatment with bis(7)-tacrine. Most of the differentially expressed proteins are involved in energy metabolism, oxidative stress, and apoptosis. In particular, the altered patterns of four of these proteins were further validated by Western blot analysis. Our findings suggest that multiple signaling pathways initiated by the altered mitochondrial proteins may mediate glutamate-induced excitotoxicity and also offer potentially useful intracellular targets for the neuroprotection provided by bis(7)-tacrine. 相似文献
36.
Shota Sawake Noriaki Tajima Jenny C. Mortimer Jeemeng Lao Toshiki Ishikawa Xiaolan Yu Yukiko Yamanashi Yoshihisa Yoshimi Maki Kawai-Yamada Paul Dupree Yoichi Tsumuraya Toshihisa Kotake 《The Plant cell》2015,27(12):3397-3409
Humans are unable to synthesize l-ascorbic acid (AsA), yet it is required as a cofactor in many critical biochemical reactions. The majority of human dietary AsA is obtained from plants. In Arabidopsis thaliana, a GDP-mannose pyrophosphorylase (GMPP), VITAMIN C DEFECTIVE1 (VTC1), catalyzes a rate-limiting step in AsA synthesis: the formation of GDP-Man. In this study, we identified two nucleotide sugar pyrophosphorylase-like proteins, KONJAC1 (KJC1) and KJC2, which stimulate the activity of VTC1. The kjc1kjc2 double mutant exhibited severe dwarfism, indicating that KJC proteins are important for growth and development. The kjc1 mutation reduced GMPP activity to 10% of wild-type levels, leading to a 60% reduction in AsA levels. On the contrary, overexpression of KJC1 significantly increased GMPP activity. The kjc1 and kjc1kjc2 mutants also exhibited significantly reduced levels of glucomannan, which is also synthesized from GDP-Man. Recombinant KJC1 and KJC2 enhanced the GMPP activity of recombinant VTC1 in vitro, while KJCs did not show GMPP activity. Yeast two-hybrid assays suggested that the stimulation of GMPP activity occurs via interaction of KJCs with VTC1. These results suggest that KJCs are key factors for the generation of GDP-Man and affect AsA level and glucomannan accumulation through the stimulation of VTC1 GMPP activity. 相似文献
37.
38.
Engineering temporal accumulation of a low recalcitrance polysaccharide leads to increased C6 sugar content in plant cell walls 下载免费PDF全文
Miguel E. Vega‐Sánchez Dominique Loqué Jeemeng Lao Michela Catena Yves Verhertbruggen Thomas Herter Fan Yang Jesper Harholt Berit Ebert Edward E. K. Baidoo Jay D. Keasling Henrik V. Scheller Joshua L. Heazlewood Pamela C. Ronald 《Plant biotechnology journal》2015,13(7):903-914
Reduced cell wall recalcitrance and increased C6 monosaccharide content are desirable traits for future biofuel crops, as long as these biomass modifications do not significantly alter normal growth and development. Mixed‐linkage glucan (MLG), a cell wall polysaccharide only present in grasses and related species among flowering plants, is comprised of glucose monomers linked by both β‐1,3 and β‐1,4 bonds. Previous data have shown that constitutive production of MLG in barley (Hordeum vulgare) severely compromises growth and development. Here, we used spatio‐temporal strategies to engineer Arabidopsis thaliana plants to accumulate significant amounts of MLG in the cell wall by expressing the rice CslF6 MLG synthase using secondary cell wall and senescence‐associated promoters. Results using secondary wall promoters were suboptimal. When the rice MLG synthase was expressed under the control of a senescence‐associated promoter, we obtained up to four times more glucose in the matrix cell wall fraction and up to a 42% increase in saccharification compared to control lines. Importantly, these plants grew and developed normally. The induction of MLG deposition at senescence correlated with an increase of gluconic acid in cell wall extracts of transgenic plants in contrast to the other approaches presented in this study. MLG produced in Arabidopsis has an altered structure compared to the grass glucan, which likely affects its solubility, while its molecular size is unaffected. The induction of cell wall polysaccharide biosynthesis in senescing tissues offers a novel engineering alternative to enhance cell wall properties of lignocellulosic biofuel crops. 相似文献
39.
A new quantum dot (QD)-aptamer (apt) beacon that acts by folding-induced dissociation of a DNA intercalating dye, BOBO-3(B), is demonstrated with label-free thrombin detection. The beacon, denoted as QD-apt:B, is constructed by (1) coupling of a single-stranded thrombin aptamer to Qdot 565 via EDC/Sulfo-NHS chemistry and (2) staining the duplex regions of the aptamer on QD with excess BOBO-3 before thrombin binding. When mixing a thrombin sample with QD-apt:B, BOBO-3 is competed away from the beacon due to target-induced aptamer folding, which then causes a decrease in QD fluorescence resonance energy transfer (FRET)-mediated BOBO-3 emission and achieves thrombin quantitation. In this work, the effects of Mg(2+), coupling time, and aptamer type on the beacon's performances are investigated and discussed thoroughly with various methods, including transmission electron microscopy (TEM), dynamic light scattering (DLS), and two-color differential gel electrophoresis. Using the best aptamer beacon (HTQ37), we attain highly specific and wide-range detection (from nM to μM) of thrombin in buffer, and the beacon can sense nM-range thrombin in 15% diluted serum. Compared to the reported QD aptamer assays, our method is advantageous from the aspect of using a simple sensory unit design without losing the detection sensitivity. Therefore, we consider the QD-apt:B beacon a potential alternative to immuno-reagents and an effective tool to study nucleic acid folding on QD as well. 相似文献
40.
Hoffmann TJ Kvale MN Hesselson SE Zhan Y Aquino C Cao Y Cawley S Chung E Connell S Eshragh J Ewing M Gollub J Henderson M Hubbell E Iribarren C Kaufman J Lao RZ Lu Y Ludwig D Mathauda GK McGuire W Mei G Miles S Purdy MM Quesenberry C Ranatunga D Rowell S Sadler M Shapero MH Shen L Shenoy TR Smethurst D Van den Eeden SK Walter L Wan E Wearley R Webster T Wen CC Weng L Whitmer RA Williams A Wong SC Zau C Finn A Schaefer C Kwok PY Risch N 《Genomics》2011,98(2):79-89
The success of genome-wide association studies has paralleled the development of efficient genotyping technologies. We describe the development of a next-generation microarray based on the new highly-efficient Affymetrix Axiom genotyping technology that we are using to genotype individuals of European ancestry from the Kaiser Permanente Research Program on Genes, Environment and Health (RPGEH). The array contains 674,517 SNPs, and provides excellent genome-wide as well as gene-based and candidate-SNP coverage. Coverage was calculated using an approach based on imputation and cross validation. Preliminary results for the first 80,301 saliva-derived DNA samples from the RPGEH demonstrate very high quality genotypes, with sample success rates above 94% and over 98% of successful samples having SNP call rates exceeding 98%. At steady state, we have produced 462 million genotypes per week for each Axiom system. The new array provides a valuable addition to the repertoire of tools for large scale genome-wide association studies. 相似文献