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:      
  示例: 沙坡头地区,人工植被区,变化  检索词用空格隔开表示必须包含全部检索词,用“,”隔开表示只需满足任一检索词即可!
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   2524篇
  免费   69篇
  国内免费   10篇
耳鼻咽喉   16篇
儿科学   101篇
妇产科学   110篇
基础医学   258篇
口腔科学   120篇
临床医学   352篇
内科学   389篇
皮肤病学   66篇
神经病学   182篇
特种医学   41篇
外国民族医学   1篇
外科学   174篇
综合类   58篇
现状与发展   1篇
一般理论   1篇
预防医学   209篇
眼科学   40篇
药学   263篇
  2篇
中国医学   50篇
肿瘤学   169篇
  2024年   86篇
  2023年   56篇
  2022年   139篇
  2021年   182篇
  2020年   138篇
  2019年   144篇
  2018年   180篇
  2017年   139篇
  2016年   127篇
  2015年   108篇
  2014年   123篇
  2013年   172篇
  2012年   232篇
  2011年   196篇
  2010年   112篇
  2009年   68篇
  2008年   91篇
  2007年   110篇
  2006年   63篇
  2005年   47篇
  2004年   35篇
  2003年   19篇
  2002年   13篇
  2000年   4篇
  1999年   3篇
  1998年   3篇
  1997年   4篇
  1996年   3篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1988年   1篇
  1980年   1篇
排序方式: 共有2603条查询结果,搜索用时 15 毫秒
91.
Mesenchymal stem cells (MSCs) are a population of multipotent cells with the ability of expansion and plastic-adherence in vitro. MSCs can differentiate into chondrocytes, osteocytes and adipocytes; they lack co-stimulatory molecules and have small amount of MHC-I that makes no immunogenicity. These characteristics are empowering MSCs’ huge in vivo applications. In addition, MSCs possess the ability of regulating the immune responses in many diseases. Many studies have shown that MSCs have immunosuppressive as well as immunoenhancing properties such as inhibition of T-lymphocytes proliferation and cytokines production which lead to the balance of Th1 and Th2. Some other immunomodulatory features of MSCs are increasing suppressive capacity of Treg, reducing activity of B-lymphocytes and immunoglobulins secretion, inhibition of dendritic cells maturation and antigen presenting capacity, and inhibition of NK-cells activity. MSCs also exert inhibitory effects on neutrophil apoptosis and reduce reactive oxygen species production. The purpose of this paper is to focus on the MSCs? effects on immune cells, especially neutrophils.  相似文献   
92.

Background

Calprotectin (S100A8/S100A9), a heterodimeric EF-hand Ca2+?binding protein, are abundant in cytosol of neutrophils and are involved in inflammatory processes and several cancerous pathogens.

Objective

The purpose of the present systematic review is to evaluate the pro- and anti-tumorigenic functions of calprotectin and its relation to inflammation.

Materials and methods

We conducted a review of studies published in the Medline (1966–2018), Scopus (2004–2018), ClinicalTrials.gov (2008–2018) and Google Scholar (2004–2018) databases, combined with studies found in the reference lists of the included studies.

Results

Elevated levels of S100A8/S100A9 were detected in inflammation, neoplastic tumor cells and various human cancers. Recent data have explained that many cancers arise from sites of infection, chronic irritation, and inflammation. The inflammatory microenvironment which largely includes calprotectin, has an essential role on high producing of inflammatory factors and then on neoplastic process and metastasis.

Conclusion

Scientists have shown different outcomes in inflammation, malignancy and apoptosis whether the source of the aforementioned protein is extracellular or intracellular. These findings are offering new insights that anti-inflammatory therapeutic agents and anti-tumorigenic functions of calprotectin can lead to control cancer development.
  相似文献   
93.
Abstract

This investigation was conducted to evaluate comparison of myo-inositol and metformin on glycemic control, lipid profiles, and gene expression related to insulin and lipid metabolism in women with polycystic ovary syndrome (PCOS). This randomized controlled trial was conducted on 53 women with PCOS, aged 18–40 years old. Subjects were randomly allocated into two groups to take either myo-inositol (n?=?26) or metformin (n?=?27) for 12 weeks. Myo-inositol supplementation, compared with metformin, significantly reduced fasting plasma glucose (FPG) (β ?5.12?mg/dL; 95% CI, ?8.09, ?2.16; p=.001), serum insulin levels (β ?1.49 µIU/mL; 95% CI, ?2.28, ?0.70; p<.001), homeostasis model of assessment-insulin resistance (β ?0.36; 95% CI, ?0.55, ?0.17; p<.001), serum triglycerides (β 12.42?mg/dL; 95% CI, ?20.47, ?4.37; p=.003) and VLDL-cholesterol levels (β ?2.48?mg/dL; 95% CI, ?4.09, ?0.87; p=.003), and significantly increased the quantitative insulin sensitivity check index (β 0.006; 95% CI, 0.002, 0.01; p=.006) compared with metformin. Moreover, myo-inositol supplementation upregulated gene expression of peroxisome proliferator-activated receptor gamma (PPAR-γ) (p=.002) compared with metformin. Overall, taking myo-inositol, compared with metformin, for 12 weeks by women with PCOS had beneficial effects on glycemic control, triglycerides and VLDL-cholesterol levels, and gene expression of PPAR-γ.  相似文献   
94.
95.

Background and Aims  

Among the ethnic groups, the age-standardized incidence rate of colorectal cancer (CRC) is highest among African-Americans. The majority of CRC arise from preexisting adenoma. It is shown that 30% of the US adult population has adenomas. The potential risk of malignant transformation in adenomas differs by specific pathologic and clinical characteristics that we aimed to study in AAs.  相似文献   
96.
97.
98.

Skeletal muscle contractions are caused to release myokines by muscle fiber. This study investigated the myogenic regulatory factors, as MHC I, IIA, IIX, Myo-D, MRF4, Murf, Atrogin-1, Decorin, Myonection, and IL-15 mRNA expression in the response of eccentric vs concentric contraction. Eighteen healthy men were randomly divided into two eccentric and concentric groups, each of 9 persons. Isokinetic contraction protocols included maximal single-leg eccentric or concentric knee extension tasks at 60°/s with the dominant leg. Contractions consisted of a maximum of 12 sets of 10 reps, and the rest time between each set was 30 s. The baseline biopsy was performed 4 weeks before the study, and post-test biopsies were taken immediately after exercise protocols from the vastus lateralis muscle. The gene expression levels were evaluated using Real-Time PCR methods. The eccentric group showed a significantly lower RPE score than the concentric group (P?≤?0.05). A significant difference in MyoD, MRF4, Myonection, and Decorin mRNA, were observed following eccentric or concentric contractions (P?≤?0.05). The MHC I, MHC IIA, IL-15 mRNA has been changed significantly compared to the pre-exercise in the concentric group (P?≤?0.05). While only MHC IIX and Atrogin-1 mRNA changed significantly in the eccentric group (P?≤?0.05). Additionally, the results showed a significant difference in MyoD, MRF4, IL-15, and Decorin at the follow-up values between eccentric or concentric groups (P?≤?0.05). Our findings highlight the growing importance of elucidating the different responses of muscle growth factors associated with a myogenic activity such as MHC IIA, Decorin, IL-15, Myonectin, Decorin, MuRF1, and MHC IIX mRNA in following various types of exercise.

  相似文献   
99.
During simple sensorimotor decision making, neurons in the parietal cortex extract evidence from sensory information provided by visual areas until a decision is reached. Contextual information can bias parietal activity during the task and change the decision-making parameters. One type of contextual information is the availability of reward for correct decisions. We tested the hypothesis that the frontal lobes and basal ganglia use contextual information to bias decision making to maximize reward. Human volunteers underwent functional MRI while making decisions about the motion of dots on a computer monitor. On rewarded trials, subjects responded more slowly by increasing the threshold to decision. Rewarded trials were associated with activation in the ventral striatum and prefrontal cortex in the period preceding coherent dot motion, and the degree of activation predicted the increased decision threshold. Decreasing dopamine transmission, using a tyrosine-depleting amino acid mixture, abolished the reward-related corticostriatal activation and eliminated the correlation between striatal activity and decision threshold. These observations provide direct evidence that some reward-related functional MRI signals in the striatum are the result of dopamine neuron activity and demonstrate that mesolimbic dopamine transmission can influence perceptual and decision-making neural processes engaged to maximize reward harvest.  相似文献   
100.
The aim of this article was to evaluate the expression of E-cadherin and CD44 adhesion molecule in oral tongue squamous cell carcinoma (SCC) since inappropriate expression of adhesion molecules raises the metastatic ability of the tumor cells.Biopsy specimens from 92 patients with tongue SCC were examined for the expression of E-cadherin and CD44 by immunohistochemistry. The relationship of immunoreactivity with tumor stage and cervical lymph node metastasis was then analyzed.Sixty-one patients (66.3%) had reduced or negative staining for CD44. Weak or absent staining for E-cadherin was seen in 14 patients (15.21%). Cervical lymph node metastasis is associated with decreased or negative staining for CD44, but no association was found between E-cadherin immunoreactivity and nodal metastasis.Our study reveals that reduced expression of CD44 could be an indicator of high invasiveness of tumor by increasing cervical lymph node metastasis.  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