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   11024篇
  免费   477篇
  国内免费   81篇
耳鼻咽喉   375篇
儿科学   508篇
妇产科学   542篇
基础医学   773篇
口腔科学   357篇
临床医学   913篇
内科学   2774篇
皮肤病学   185篇
神经病学   586篇
特种医学   451篇
外科学   2579篇
综合类   156篇
一般理论   1篇
预防医学   231篇
眼科学   374篇
药学   416篇
中国医学   24篇
肿瘤学   337篇
  2024年   4篇
  2023年   107篇
  2022年   147篇
  2021年   326篇
  2020年   202篇
  2019年   238篇
  2018年   298篇
  2017年   246篇
  2016年   385篇
  2015年   438篇
  2014年   572篇
  2013年   647篇
  2012年   840篇
  2011年   738篇
  2010年   507篇
  2009年   504篇
  2008年   775篇
  2007年   889篇
  2006年   789篇
  2005年   784篇
  2004年   653篇
  2003年   561篇
  2002年   445篇
  2001年   101篇
  2000年   67篇
  1999年   62篇
  1998年   50篇
  1997年   35篇
  1996年   42篇
  1995年   28篇
  1994年   16篇
  1993年   13篇
  1992年   19篇
  1991年   10篇
  1990年   8篇
  1989年   6篇
  1988年   4篇
  1987年   2篇
  1986年   5篇
  1985年   4篇
  1984年   3篇
  1982年   2篇
  1980年   2篇
  1979年   1篇
  1976年   1篇
  1974年   1篇
  1970年   1篇
  1969年   1篇
  1966年   1篇
  1960年   1篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
21.
Organ-specific injury after transplantation presents with a variety of clinical and pathological phenotypes, yet the factors influencing development of each outcome are poorly understood. Because primed T lymphocytes must re-encounter their antigen within the target organ to engage effector functions, we postulated that the cellular location of antigen within that organ could significantly impact the induced pathology. We challenged female Marilyn CD4 T-cell receptor transgenic mice, in which all T cells are specific for the male minor transplantation antigen, with male heart transplants expressing the relevant peptide: major histocompatibility complex on either graft parenchymal/vascular cells or alternatively, on graft-infiltrating mononuclear cells. The two different graft donors led to equivalent activation of recipient T cells as assessed by frequency, cell surface marker expression, cytokine production, and the ability to traffic to the graft. Nonetheless, if the target antigen was expressed on graft vascular and/or parenchymal cells, the outcome was acute graft destruction. In contrast, if the antigen was expressed only on graft-infiltrating mononuclear cells the same effector T-cell repertoire caused chronic rejection and vasculopathy. This unique result, that target antigen location can influence pathological outcome, has significant implications for understanding the pathogenesis of chronic allograft injury in humans.  相似文献   
22.
23.
Green tea polyphenols (GrTP), the active ingredient of green tea, may have immunosuppressive properties, but whether and how GrTP affect transplant-reactive T cells is unknown. To address this, we tested the effects of GrTP on in vitro and in vivo transplant-reactive T cell immunity. GrTP inhibited IFNgamma secretion by cultured monoclonal T cells and by alloreactive T cells in mixed lymphocyte reactions. Oral GrTP significantly prolonged minor antigen-disparate skin graft survival and decreased the frequency of donor-reactive interferon gamma-producing T cells in recipient secondary lymphoid organs compared to controls. In contrast to other hypothesized actions, oral GrTP did not alter dendritic cell trafficking to lymph nodes or affect metalloproteinase activity in the graft. This is the first report of an immunosuppressive effect of GrTP on transplant-reactive T cell immunity. The results suggest that oral intake of green tea could act as an adjunctive therapy for prevention of transplant rejection in humans.  相似文献   
24.
Mast cells have been implicated as important in tissue remodeling and fibrosis. We investigated the effect of mechanical ventricular unloading upon myocardial fibrosis and cardiac mast cell density in patients undergoing left ventricular assist device (LVAD) implantation. Paired myocardial tissue samples were obtained from 30 patients with end-stage cardiomyopathy at the time of LVAD implantation and at the time of removal and were compared with samples taken from donor hearts. Tissue sections were stained and quantitated for mast cells and myocardial fibrosis. Mast cell density (tryptase positive cells) in cardiomyopathy was higher than that in donor hearts (33.5 +/- 3.6 SEM cells/10 fields vs.15.2 +/- 2.0 SEM cells/10 fields respectively, p = 0.04) and was lower than LVAD supported hearts (33.5 +/- 3.6 SEM cells/10 fields vs. 49.8 +/- 5.7 SEM cells/10 fields respectively, p = 0.01). Mast cells are primarily localized in areas of increased interstitial fibrosis adjacent to myocardial cells and not vessels. There was statistically significant correlation between mast cells and interstitial collagen (p = 0.03) in patients before LVAD implantation that did not persist after mechanical support (p = 0.18). These results suggest that mechanical support with left ventricular assist devices induces an increase in mast cell number in the myocardium and an associated decrease in myocardial fibrosis. We believe these data demonstrate a dual role for cardiac mast cells in the increase in fibrosis in heart failure and the decrease after LVAD and its associated cardiac improvement.  相似文献   
25.
26.
The role of survivin that regulates the biological behavior of non-small-cell lung carcinoma (NSCLC) is still controversial. We aimed to investigate survivin expression in NSCLC and to define any correlation with expressions of p53, bcl-2, bax, apoptotic index (AI), tumor cell proliferation, clinicopathologic variables, and overall survival. Tumors of 63 patients with NSCLC were examined for expressions of survivin, p53, bcl-2, bax, and Ki-67 by immunohistochemistry. AI was also evaluated. Results for each antibody were correlated with each other, and with clinicopathologic variables including age, sex, histologic subtype, TNM (T: primary tumor, N: regional lymph node metastasis, M: distant metastasis) stage, lymph node status, smoking history, and prognosis. Nuclear survivin expression was inversely correlated with p53 expression (P = 0.04, r = - 0.367), and tumor stage (P = 0.03, r = - 0.273), and positively correlated with tumor cell proliferation (P = 0.009, r = 0.329). Cytoplasmic survivin expression positively correlated with smoking history (P = 0.02, r = 0.282). Survivin/bax ratio was inversely correlated with AI (r: - 0.004). By Kaplan-Meier analysis, TNM stage (P < or = 0.001), lymph node metastasis (P = 0.04), and Ki-67 index (P < or = 0.001) were associated with survival, whereas survivin was not. In multivariate analysis, only TNM stage was an independent predictor. Although survivin and other apoptosis-related protein expressions fail to predict the clinical outcome, the present findings suggest that survivin is involved in tumor cell apoptosis and proliferation and may play a role in critical steps of cancer progression in NSCLC.  相似文献   
27.

Background

Hereditary angioedema (HAE) attacks can be provoked with psychological factors. The aim of this study was to assess the effects of anxiety, depression and stress related to COVID-19 pandemic on disease activity of HAE patients during the quarantine period (QP) and the return to normal period (RTNP).

Methods

This study was conducted between March 2020 and September 2020 in four allergy centres. Demographic, clinical features and mental health status were evaluated in QP (from March to the beginning of June) and RTNP (from June to the beginning of September) applied by the government. The 10-point visual analogue scale (VAS10) was used to define the severity of HAE attacks. Depression, Anxiety and Stress Scales-21 (DASS-21) and Fear of COVID-19 (FC-19) scale were performed to assess mental health status.

Results

139 HAE patients were included in the study. In QP, median attack numbers and median VAS10 scores were 5 (min-max: 0–45) and 6 (min-max: 0–10), respectively. HAE attack numbers, DASS-21 stress, anxiety, depression and total DASS-21 scores, and FC-19 scores were higher in QP than RTNP (p = 0.001, p < 0.001, p = 0.001, p < 0.001, p < 0.001, p < 0.001, respectively). However, there was no difference in attack severity scores between the two periods (p > 0.05).

Conclusions

This study revealed that the restriction measures during COVID-19 outbreak cause an increase in the number of HAE attacks in relation to anxiety, depression, stress and fear of COVID-19 pandemic. Therefore, it is important to provide psychological support to HAE patients during the pandemic.
  相似文献   
28.
In a previous study on the pathogenesis of endometriosis, we observed that constituents of menstrual effluent induce morphological alterations in human mesothelial cells. In this study, we investigated whether these alterations were associated with apoptosis or necrosis or were the result of cellular remodelling. After overnight incubation of confluent monolayers of human omental mesothelial cells (HOMEC) with conditioned media prepared from menstrual effluent shed anterogradely, severe alterations in morphology were observed. Typical polygonal mesothelial cell cultures at confluency acquired elongated spindle morphology, resulting in gaps between the cells. In contrast, mesothelial cells from the control groups receiving culture medium only, retained a normal morphology. Immunofluorescence staining revealed that cytokeratin, vimentin and actin filaments were still present, homogeneously distributed in the cell cytoplasm following changes in morphology. To evaluate whether the morphological alterations were associated with apoptosis and/or necrosis, the cells were stained with the M30 CytoDeath antibody or annexin V with propidium iodide and analysed using flow cytometry. The results showed that only a small percentage (1-7%) of the affected HOMEC were undergoing apoptosis or necrosis. We conclude that the profoundly altered morphology of HOMEC is a result of cellular remodelling and that the role of apoptosis and necrosis is negligible. Soluble paracrine factors released by cells isolated from menstrual effluent shed anterogradely may induce a reorganization of the cytoskeleton. As a result, the underlying basement membrane will be exposed and the mesothelium may no longer prevent implantation of endometrium shed retrogradely into the peritoneum, thus facilitating the development of endometriosis.  相似文献   
29.
The relationships between cancer caused by HPV and some vitamins, as well as leucocytes and their ratios, have been investigated in the literature. Our aim is to evaluate these relationships at the level of genital wart in terms of the investigated parameters and lesion numbers. Data were obtained from 98 and 94 patients for groups one and two, including warts patients and healthy people respectively. The Neutrophil/Monocyte ratio and lesion numbers in the warts patients were reported and analysed in terms of vitamin B12 and D, ferritin and leucocytes. A correlation was established between lesion numbers, age and midcorpuscular volume (p <0.05). There was no correlation between lesion numbers and recurrence. According to the comparative analysis, there were differences in terms of ferritin, neutrophil, monocyte, haemoglobin, midcorpuscular volume and neutrophil/monocyte ratio between groups. The cut-off values for neutrophil, monocyte and N/M ratios were 56.45, 4.91 and 7.825 respectively. While our study showed that wart development may be affected by blood ferritin levels and in this situation, midcorpuscular volume, neutrophil, monocyte and N/M ratios may change, a relation was found between lesion numbers and age and mean midcorpsucular volume values only. However, further studies are needed to clarify this issue.  相似文献   
30.
In the study, the ameliorating effects of alfa lipoic acid (ALA) against doxorubicin-induced testicular apoptosis, oxidative stress and disrupted mitochondrial fusion were investigated in male rats. Rats were divided into four groups as control, doxorubicin (DOX), DOX + ALA and ALA. A single dose of 15 mg/kg DOX was administered i.p to the DOX and DOX + ALA groups. 50 mg/kg ALA was given to the DOX + ALA and ALA groups by oral gavage every other day. After 28 days, rat testes and serum samples were collected and analysed. Administration of DOX alone caused a decrease in body and relative testicular weights, seminiferous tubule diameter and germinal epithelium thickness, Johnsen's score and serum testosterone levels. DOX treatment led to severe testicular damage such as tubular degeneration, and atrophic tubules. Also, the activities of superoxide dismutase and glutathione peroxidase were reduced, while the level of malondialdehyde was increased in the testis. The mRNA levels of apoptotic-related genes (CASP3, TP53, BAX, BCL2) and apoptotic index were increased, while mitofusin-2 decreased. DOX caused an increase in CASP3 and a decrease in mitofusin-2 immunoreactivities. Treatment with ALA markedly improved all of DOX-induced biochemical, histochemical and molecular alterations in rat testis. Consequently, ALA has a therapeutic role in ameliorating DOX-induced testicular damage in rats.  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