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   2519篇
  免费   147篇
  国内免费   19篇
耳鼻咽喉   118篇
儿科学   100篇
妇产科学   150篇
基础医学   446篇
口腔科学   123篇
临床医学   194篇
内科学   489篇
皮肤病学   44篇
神经病学   207篇
特种医学   51篇
外科学   177篇
综合类   11篇
一般理论   2篇
预防医学   113篇
眼科学   37篇
药学   230篇
中国医学   1篇
肿瘤学   192篇
  2023年   10篇
  2022年   40篇
  2021年   84篇
  2020年   53篇
  2019年   61篇
  2018年   81篇
  2017年   67篇
  2016年   76篇
  2015年   71篇
  2014年   85篇
  2013年   129篇
  2012年   202篇
  2011年   214篇
  2010年   88篇
  2009年   109篇
  2008年   145篇
  2007年   174篇
  2006年   143篇
  2005年   150篇
  2004年   107篇
  2003年   87篇
  2002年   97篇
  2001年   25篇
  2000年   43篇
  1999年   34篇
  1998年   25篇
  1997年   14篇
  1996年   13篇
  1994年   9篇
  1992年   20篇
  1991年   10篇
  1990年   16篇
  1989年   8篇
  1988年   7篇
  1987年   13篇
  1986年   15篇
  1985年   23篇
  1984年   13篇
  1983年   11篇
  1982年   8篇
  1980年   6篇
  1979年   11篇
  1978年   9篇
  1976年   8篇
  1974年   6篇
  1973年   5篇
  1972年   7篇
  1969年   8篇
  1968年   6篇
  1967年   5篇
排序方式: 共有2685条查询结果,搜索用时 46 毫秒
51.
Gliomas attract brain‐resident (microglia) and peripheral macrophages and reprogram these cells into immunosuppressive, pro‐invasive cells. M‐CSF (macrophage colony‐stimulating factor, encoded by the CSF1 gene) has been implicated in the control of recruitment and polarization of macrophages in several cancers. We found that murine GL261 glioma cells overexpress GM‐CSF (granulocyte–macrophage colony‐stimulating factor encoded by the CSF2 gene) but not M‐CSF when compared to normal astrocytes. Knockdown of GM‐CSF in GL261 glioma cells strongly reduced microglia‐dependent invasion in organotypical brain slices and growth of intracranial gliomas and extended animal survival. The number of infiltrating microglia/macrophages (Iba1+ cells) and intratumoural angiogenesis were reduced in murine gliomas depleted of GM‐CSF. M1/M2 gene profiling in sorted microglia/macrophages suggests impairment of their pro‐invasive activation in GM‐CSF‐depleted gliomas. Deficiency of M‐CSF (op/op mice) did not affect glioma growth in vivo and the accumulation of Iba1+ cells, but impaired accumulation of Iba1+ cells in response to demyelination. These results suggest that distinct cytokines of the CSF family contribute to macrophage infiltration of tumours and in response to injury. The expression of CSF2 (but not CSF1) was highly up‐regulated in glioblastoma patients and we found an inverse correlation between CSF2 expression and patient survival. Therefore we propose that GM‐CSF triggers and drives the alternative activation of tumour‐infiltrating microglia/macrophages in which these cells support tumour growth and angiogenesis and shape the immune microenvironment of gliomas. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.  相似文献   
52.
Interleukin 6 (IL-6) plays an important role in the initiation and acceleration of chronic inflammation and could contribute to development of microvascular complications in patients with type 1 diabetes (DM1). Therefore, this study was aimed to investigate the association between concentration of IL-6 in relation to glucose control, lipid profile, and body mass index (BMI) in 69 DM1 patients subdivided according to the absence or presence of microvascular complications. BMI, level of fasting plasma glucose (FPG), and concentrations of total cholesterol (TCH), LDL cholesterol (LDL-C), and IL-6 were higher in DM1 patients compared to the control group. In DM1 patients, IL-6 concentration was positively correlated with level of FPG, LDL-C, TCH concentrations, and BMI. These correlations were stronger in the subgroup of patients with microvascular complications. In addition, BMI independently influences IL-6 concentration in DM1 patients. In conclusion, elevated IL-6 concentration is associated with diabetes-related variables which could accelerate progression of microvascular complications in DM1 patients.  相似文献   
53.
54.
Maternal malnutrition during gestation and lactation is known to have adverse effects on offspring. We evaluate the impact of maternal diet on offspring bony labyrinth morphology. The bony labyrinth develops early and is thought to be stable to protect vital sensory organs within. For these reasons, bony labyrinth morphology has been used extensively to assess locomotion, hearing function, and phylogeny in primates and numerous other taxa. While variation related to these parameters has been documented, there is still a component of intraspecific variation that is unexplained. Although the labyrinthine developmental window is small, it may provide the opportunity for developmental instability to produce corresponding shape differences, as measured by fluctuating asymmetry (FA). We hypothesized that (a) offspring with poor maternal diet would exhibit increased FA, but (b) no unilateral shape difference. To test these hypotheses, we used two groups of rats (Rattus norvegicus; Crl:WI[Han] strain), one control group and one group exposed to a isocaloric, protein-restricted maternal diet during gestation and suckling. Individuals were sampled at weaning, sexual maturity, and old age. A Procrustes analysis of variance identified statistically significant FA in all diet-age subgroups. No differences in level of FA were identified among the subgroups, rejecting our first hypothesis. A principal components analysis identified no unilateral shape differences, supporting our second hypothesis. These results indicate that bony labyrinth morphology is remarkably stable and likely protected from a poor maternal diet during development. In light of this result, other factors must be explored to explain intraspecific variation in labyrinthine shape.  相似文献   
55.
Using whole‐genome array testing instead of karyotyping in prenatal diagnosis for all indications may be desirable because of the higher diagnostic yield and shorter reporting time. The goal of this research was finding the optimal array resolution that could replace routine prenatal karyotyping in cases without ultrasound abnormalities, for example, referred for advanced maternal age or abnormal first trimester screening. As variants of unknown clinical significance (VOUS), if reported, might complicate decision‐making about continuation of pregnancy, such an optimal array resolution should have a high abnormality detection rate and reveal a minimal amount of VOUS. The array data of 465 fetuses were retrospectively evaluated with several resolution levels, and the Decipher microdeletion/microduplication syndrome list was reviewed to assess what could be theoretically missed with a lower resolution. A 0.5‐Mb resolution showed a high diagnostic yield potential and significantly minimized the number of VOUS. Based on our experience, we recommend genomic SNP array as a first‐tier test in prenatal diagnosis. The resolution should be chosen based on the indication. In cases of fetal ultrasound abnormalities or intrauterine fetal death (IUFD), high‐resolution analysis should be done. In other cases, we advise replacing karyotyping by SNP array analysis with 0.5 Mb resolution.  相似文献   
56.
Novel functionalized (biofunctionalization followed by cisplatin immobilization) Fe3O4@SiO2@Au nanoparticles (NPs) were designed. The encapsulation of Fe3O4 cores inside continuous SiO2 shells preserves their initial structure and strong magnetic properties, while the shell surface can be decorated by small Au NPs, and then cisplatin (cPt) can be successfully immobilized on their surface. The fabricated NPs exhibit very strong T2 contrasting properties for magnetic resonance imaging (MRI). The functionalized Fe3O4@SiO2@Au NPs are tested for a potential application in photothermal cancer therapy, which is simulated by irradiation of two colon cancer cell lines (SW480 and SW620) with a laser (λ = 808 nm, W = 100 mW cm−2). It is found that the functionalized NPs possess low toxicity towards cancer cells (∼10–15%), which however could be drastically increased by laser irradiation, leading to a mortality of the cells of ∼43–50%. This increase of the cytotoxic properties of the Fe3O4@SiO2@Au NPs, due to the synergic effect between the presence of cPt plus Au NPs and laser irradiation, makes these NPs perspective agents for potential (MRI)-guided stimulated chemo-photothermal treatment of cancer.

Novel functionalized nanoparticles, with toxicity controlled by laser irradiation, are perspective agents for potential (MRI)-guided stimulated chemo-photothermal treatment of cancer.  相似文献   
57.
Both hyperphosphatemia and hypophosphatemia are associated with increased morbidity and mortality among patients on dialysis. The control of serum phosphate concentration is a considerable clinical problem. Our study aimed to improve understanding of phosphate kinetics in patients on dialysis using mathematical modeling. Three consecutive hemodialysis sessions with breaks of 2–2–3 days were monitored in 25 patients. Phosphate concentration was measured every hour and 45 min after the end of dialysis in blood serum and every 30 min in dialysate during each session. Volume of fluid compartments and body composition were assessed by bioimpedance. The pseudo one‐compartment model was applied to describe the profile of phosphate in blood serum during intra‐ and interdialytic periods of 1‐week cycle of three hemodialysis sessions. Model parameters, such as phosphate internal clearance (KM) and the rate of phosphate mobilization (RM), were correlated with the reduction of serum phosphate concentration during dialysis (Cpost/Cpre) and with equivalent continuous clearance (ECC) for phosphate. KM correlated negatively with predialysis serum phosphate concentration. There was significant positive correlation between RM and age. Postdialysis volume of phosphate central compartment was lower than, but correlated to, extracellular water volume. Parameters of the pseudo one‐compartment model, phosphate internal clearance, and the rate of phosphate inflow to the central compartment (the one accessible for dialysis) from other phosphate body reservoirs correlated with the indices of dialysis adequacy, such as reduction of serum phosphate and ECC. The pseudo one‐compartment model can be successfully extended from a single hemodialysis to the standard weekly cycle of sessions and the model parameters strongly correlate with the adequacy parameters of dialytic removal of phosphate.  相似文献   
58.
59.
Recent progress in understanding stem cell biology has been remarkable, especially in deciphering signals that support differentiation towards tissue-specific lineages. This achievement positions us firmly at the beginning of an era of patient-specific regenerative medicine and human disease modeling. It will be necessary to equip the progress in this era with a reliable source of self-renewing progenitor cells that differentiate into functional target cells. The generation of pancreatic progenitors that mature in vivo into functional beta-cells has raised the hope for new therapeutic options in diabetes, but key challenges still remain including the production of sufficient numbers of cells for research and transplantation. Recent approaches to this problem have shown that the presence of organ- and stage-specific mesenchyme improves the generation of progenitors, from endoderm to endocrine cells. Alternatively, utilization of three-dimensional culture may improve the efficiency and yield of directed differentiation. Here, we review the current knowledge of pancreatic directed differentiation and ex vivo expansion of pancreatic progenitors, including recent advances in differentiation strategies for the generation of pancreatic progenitors, and we discuss persistent challenges which will need to be overcome before personalized cell-based therapy becomes a practical strategy.  相似文献   
60.

Background

Because antileukotrienes may inhibit inflammation, it is plausible that montelukast administered for a long time could suppress skin wheal and flare reaction, and thus, it should be discarded prior to the tests. This study assessed the effect of long-lasting treatment with montelukast alone or in combination with antihistamines on wheal and flare in skin pricks tests (SPT) in patients sensitized to perennial allergens.

Methods

We conducted a 32-week, double-blind, placebo-controlled, cross-over and randomized trial that implicated two arms: arm A, 20 patients received levocetirizine, montelukast with or without levocetirizine or placebo; arm B, 20 patients received desloratadine, montelukast with or without desloratadine or placebo. All treatment periods lasted 6 weeks and were separated by 2-week washouts. At baseline and on the last day of each treatment period, SPT were performed in all participants.

Results

Both levocetirizine and desloratadine in monotherapy, or in combination with montelukast, were effective in reducing wheal and flare in SPT. Monotherapy with montelukast did not change the size of the wheal for either histamine or for house dust mites, in either arm of the study, but significantly reduced the size of flare for histamine in arm A. Addition of montelukast to antihistamine did not exceed efficacy of monotherapy with antihistamine in both arms of the study.

Conclusions

Since the size of wheal determines the results of SPT, montelukast, even taken for a long time, does not have to be discarded prior to the tests.  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