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   3371篇
  免费   202篇
  国内免费   9篇
  2023年   47篇
  2022年   70篇
  2021年   158篇
  2020年   98篇
  2019年   127篇
  2018年   127篇
  2017年   87篇
  2016年   135篇
  2015年   170篇
  2014年   192篇
  2013年   277篇
  2012年   232篇
  2011年   272篇
  2010年   137篇
  2009年   133篇
  2008年   135篇
  2007年   150篇
  2006年   125篇
  2005年   111篇
  2004年   104篇
  2003年   88篇
  2002年   91篇
  2001年   50篇
  2000年   30篇
  1999年   38篇
  1998年   26篇
  1997年   23篇
  1996年   14篇
  1995年   12篇
  1994年   24篇
  1993年   13篇
  1992年   17篇
  1991年   17篇
  1990年   12篇
  1989年   15篇
  1988年   24篇
  1987年   13篇
  1986年   18篇
  1985年   17篇
  1984年   9篇
  1983年   14篇
  1982年   12篇
  1981年   8篇
  1980年   8篇
  1979年   13篇
  1977年   12篇
  1976年   10篇
  1974年   6篇
  1973年   10篇
  1971年   7篇
排序方式: 共有3582条查询结果,搜索用时 21 毫秒
991.
Here, we have investigated the therapeutic potency of EW-7197, a transforming growth factor-β type I receptor kinase inhibitor, against postsurgical adhesion band formation. Our results showed that this pharmacological inhibitor prevented the frequency and the stability of adhesion bands in mice model. We have also shown that downregulation of proinflammatory cytokines, reduce submucosal edema, attenuation of proinflammatory cell infiltration, inhibition of oxidative stress, decrease in excessive collagen deposition, and suppression of profibrotic genes at the site of surgery are some of the mechanisms by which EW-7197 elicits its protective responses against adhesion band formation. These results clearly suggest that EW-7197 has novel therapeutic properties against postsurgical adhesion band formation with clinically translational potential of inhibiting key pathological responses of inflammation and fibrosis in postsurgery patients.  相似文献   
992.
The Helicobacter pylori outer membrane proteins play an important role in pathogenesis; the outer inflammatory protein A (OipA) is one of these proteins which play the main role in the development of inflammation. In this study, purification of recombinant H. pylori OipA was performed by Ni–NTA affinity chromatography. Gastric carcinoma epithelial cells (AGS cell) were treated by different concentrations of recombinant OipA for various lengths of time and cell viability was evaluated by the viability assay. Statistical analysis showed that OipA had toxic effects on AGS cells in a concentration of 500 ng/ml after 24 and 48 h, and this toxic dose was 256 ng/ml after 72 h. OipA had direct toxic effects on gastric epithelial cells and the toxicity was observed to depend on time and dose of H. pylori exposure. Attachment of H. pylori to gastric epithelial cells is a key part in the pathogenesis and enables H. pylori to damage the epithelial cells with OipA.  相似文献   
993.
The aim of this study was to evaluate the effect of a 5-kHz repetition frequency of electroporating electric pulses in comparison to the standard 1-Hz frequency on blood flow of invasive ductal carcinoma tumors in Balb/C mice. Electroporation was performed by the delivery of eight electric pulses of 1,000 V cm−1 and 100 μs duration at a repetition frequency of 1 Hz or 5 kHz. Blood flow changes in tumors were measured by laser Doppler flowmetry. Monitoring was performed continuously for 10 min before application of the electric pulses as well as immediately after application of the electric pulses for 40 min. The delivery of electric pulses to tumors induced changes in tumor blood flow. The reduction in blood flow started after the stimulation and continued for the 40-min period of observation. There was a significant difference in blood flow changes 3 min after application of the electric pulses at 1-Hz or 5-kHz repetition frequency. However, after 3 min the difference became nonsignificant. The findings showed that the high pulse frequency (5 kHz) had an effect comparable to the 1-Hz frequency on tumor blood flow except at very short times after pulse delivery, when pulses at 5 kHz produced a more intense reduction of blood flow.  相似文献   
994.
International Journal of Peptide Research and Therapeutics - Prostate cancer is one of the most common cancers around the world. Vaccines are a new hope for prevention of this cancer. In the case...  相似文献   
995.
The chemical and pharmacological profiles of essential oils (EOs) hydrodistilled in yields of 0.03–0.77 % (w/w) from three exotic (Cinnamomum camphora, Petroselinum crispum, and Syzygium samarangense) and two endemic (Pittosporum senacia subsp. senacia and Syzygium coriaceum) medicinal plants were studied. GC-MS/GC-FID analysis of the EOs identified the most dominant components to be myristicin (40.3 %), myrcene (62.2 %), 1,8-cineole (54.0 %), β-pinene (21.3 %) and (E)-β-ocimene (24.4 %) in P. crispum, P. senacia and C. camphora, S. samarangense and S. coriaceum EOs, respectively. All EOs were found to possess anti-amylase (0.70–1.50 mM ACAE/g EO) and anti-tyrosinase (109.35–158.23 mg KAE/g) properties, whereas no glucosidase inhibition was displayed. Only Syzygium EOs acted as dual inhibitors of both acetyl- and butyryl-cholinesterases, while P. senacia and C. camphora EOs inhibited acetylcholinesterase selectively and P. crispum EO was inactive (AChE: 4.64–4.96 mg GALAE/g; BChE: 5.96 and 7.10 mg GALAE/g). Molecular docking revealed 1,8-cineole to present the best binding affinities with butyrylcholinesterase, amylase and tyrosinase, while both myristicin and β-pinene with acetylcholinesterase and finally β-pinene with glucosidase. In vitro antioxidant potency was also demonstrated in different assays (DPPH: 13.52–53.91 mg TE/g, ABTS: 5.49–75.62 mg TE/g; CUPRAC: 45.38–243.21 mg TE/g, FRAP: 42.49–110.64 mg TE/g; and phosphomolybdenum assay: 82.61–160.93 mM TE/g). Principal component analysis revealed the EOs to differ greatly in their bioactivities due to their chemodiversity. This study has unveiled some interesting preliminary pharmacological profiles of the EOs that could be explored for their potential applications as phytotherapeutics.  相似文献   
996.
Enterotoxigenic Escherichia coli produce various heat-labile and heat-stable enterotoxins. STb is a low molecular weight heat-resistant toxin responsible for diarrhea in farm animals, mainly young pigs. A previous study demonstrated that cells having internalized STb toxin induce epithelial barrier dysfunction through changes in tight junction (TJ) proteins. These modifications contribute probably to the diarrhea observed. To gain insight into the mechanism of increased intestinal permeability following STb exposure we treated human colon cells (T84) with purified STb toxin after which cells were harvested and proteins extracted. Using a 1% Nonidet P-40-containing solution we investigated the distribution of claudin-1, a major structural and functional TJ protein responsible for the epithelium impermeability, between membrane (NP40-insoluble) and the cytoplasmic (NP-40 soluble) location. Using immunoblot and confocal microscopy, we observed that treatment of T84 cell monolayers with STb induced redistribution of claudin-1. After 24 h, cells grown in Ca++-free medium treated with STb showed about 40% more claudin-1 in the cytoplasm compare to the control. Switching from Ca++-free to Ca++-enriched medium (1.8 mM) increased the dislodgement rate of claudin-1 as comparable quantitative delocalization was observed after only 6 h. Medium supplemented with the same concentration of Mg++ or Zn++ did not affect the dislodgement rate compared to the Ca++-free medium. Using anti-phosphoserine and anti-phosphothreonine antibodies, we observed that the loss of membrane claudin-1 was accompanied by dephosphorylation of this TJ protein. Overall, our findings showed an important redistribution of claudin-1 in cells treated with STb toxin. The loss of phosphorylated TJ membrane claudin-1 is likely to be involved in the increased permeability observed. The mechanisms by which these changes are brought about remain to be elucidated.  相似文献   
997.
Pregnancy is characterized by the infiltration of leukocytes in the reproductive tissues and at the maternal-fetal interface (decidua basalis and decidua parietalis). This interface is the anatomical site of contact between maternal and fetal tissues; therefore, it is an immunological site of action during pregnancy. Infiltrating leukocytes at the maternal-fetal interface play a central role in implantation, pregnancy maintenance, and timing of delivery. Therefore, phenotypic and functional characterizations of these leukocytes will provide insight into the mechanisms that lead to pregnancy disorders. Several protocols have been described in order to isolate infiltrating leukocytes from the decidua basalis and decidua parietalis; however, the lack of consistency in the reagents, enzymes, and times of incubation makes it difficult to compare these results. Described herein is a novel approach that combines the use of gentle mechanical and enzymatic dissociation techniques to preserve the viability and integrity of extracellular and intracellular markers in leukocytes isolated from the human tissues at the maternal-fetal interface. Aside from immunophenotyping, cell culture, and cell sorting, the future applications of this protocol are numerous and varied. Following this protocol, the isolated leukocytes can be used to determine DNA methylation, expression of target genes, in vitro leukocyte functionality (i.e., phagocytosis, cytotoxicity, T-cell proliferation, and plasticity, etc.), and the production of reactive oxygen species at the maternal-fetal interface. Additionally, using the described protocol, this laboratory has been able to describe new and rare leukocytes at the maternal-fetal interface.  相似文献   
998.
One response to humanity's unsustainable use of natural resources and consequent degradation, even destruction of the environment, is to establish conservation areas to protect Nature and preserve biodiversity at least in selected regions. In Qatar, the government has shown strong support for this approach, confronted by the environmental consequences of oil and gas extraction and rapid urban development, by designating about one-tenth of the country a conservation area. Located in the west of the peninsula, it comprises the Al Reem Reserve, subsequently declared a UNESCO Biosphere Reserve. Several approaches have figured in conservation, currently popular is co-management featuring participation of the local population, which recognises that people's activities often contribute to today's environment, with the promotion of bio-cultural diversity. However, these assumptions may not hold where rapid social and cultural change occurs, as in Qatar. We explore the implications of such change, notably in land use. We detail changes resulting with the move from nomadic to sedentary lifestyles: in land access, which now features tribal-state control, and herding strategies, which now feature migrant labour and depend on imported fodder and water, underwritten by the country's large gas and oil revenues. Current stocking arrangements - animals herded in much smaller areas than previously - are thought responsible for the degradation of natural resources. The place of animals, notably camels, in Qatari life, has also changed greatly, possibly further promoting overstocking. Many local people disagree. What are the implications of such changes for the participatory co-management of conservation areas? Do they imply turning the clock back to centrally managed approaches that seek to control access and local activities?  相似文献   
999.
MAP/Microtubule affinity-regulating kinase 4 (MARK4) belongs to the family of serine/threonine kinases that phosphorylate the microtubule-associated proteins (MAP) causing their detachment from the microtubules thereby increasing microtubule dynamics and facilitating cell division, cell cycle control, cell polarity determination, cell shape alterations, etc. The MARK4 gene encodes two alternatively spliced isoforms, L and S that differ in their C-terminal region. These isoforms are differentially regulated in human tissues including central nervous system. MARK4L is a 752-residue-long polypeptide that is divided into three distinct domains: (1) protein kinase domain (59–314), (2) ubiquitin-associated domain (322–369), and (3) kinase-associated domain (703–752) plus 54 residues (649–703) involved in the proper folding and function of the enzyme. In addition, residues 65–73 are considered to be the ATP-binding domain and Lys88 is considered as ATP-binding site. Asp181 has been proposed to be the active site of MARK4 that is activated by phosphorylation of Thr214 side chain. The isoform MARK4S is highly expressed in the normal brain and is presumably involved in neuronal differentiation. On the other hand, the isoform MARK4L is upregulated in hepatocarcinoma cells and gliomas suggesting its involvement in cell cycle. Several biological functions are also associated with MARK4 including microtubule bundle formation, nervous system development, and positive regulation of programmed cell death. Therefore, MARK4 is considered as the most suitable target for structure-based rational drug design. Our sequence, structure- and function-based analysis should be helpful for better understanding of mechanisms of regulation of microtubule dynamics and MARK4 associated diseases.  相似文献   
1000.
In the lungs of cystic fibrosis patients, overproduction of mucus leads to morbidity and mortality by obstructing airflow and shielding bacteria from antibiotics. Here we demonstrate that overproduction of mucus is a direct result of the activation of mucin gene expression by Gram-positive bacteria. Bacterial lipoteichoic acid activates the platelet-activating factor receptor, which is G protein-coupled. This results in activation of a disintegrin and metalloproteinase (ADAM10), kuzbanian, cleavage of pro heparin-binding epidermal growth factor and activation of the epidermal growth factor receptor. Unlike responses in macrophages, the epithelial-cell response to lipoteichoic acid does not require Toll-like receptor 2 or 4.  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