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   1539篇
  免费   104篇
  国内免费   8篇
耳鼻咽喉   7篇
儿科学   40篇
妇产科学   13篇
基础医学   233篇
口腔科学   65篇
临床医学   94篇
内科学   404篇
皮肤病学   45篇
神经病学   147篇
特种医学   45篇
外科学   135篇
综合类   7篇
预防医学   66篇
眼科学   31篇
药学   143篇
中国医学   23篇
肿瘤学   153篇
  2024年   1篇
  2023年   19篇
  2022年   52篇
  2021年   68篇
  2020年   24篇
  2019年   40篇
  2018年   58篇
  2017年   27篇
  2016年   41篇
  2015年   55篇
  2014年   55篇
  2013年   82篇
  2012年   107篇
  2011年   158篇
  2010年   76篇
  2009年   62篇
  2008年   80篇
  2007年   104篇
  2006年   96篇
  2005年   99篇
  2004年   94篇
  2003年   68篇
  2002年   65篇
  2001年   10篇
  2000年   11篇
  1999年   6篇
  1998年   11篇
  1997年   12篇
  1996年   9篇
  1995年   11篇
  1994年   10篇
  1993年   7篇
  1992年   3篇
  1991年   3篇
  1990年   4篇
  1989年   4篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1981年   3篇
  1980年   2篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有1651条查询结果,搜索用时 15 毫秒
71.

Background

Some patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) also have positivity of rheumatoid factor (RF). However, the clinical significance of this occurrence remains unknown in AAV patients. The aim of this study was to clarify an association between the presence of RF and clinical features in patients with AAV.

Results

Forty-seven patients diagnosed with AAV who were not complicated with RA were enrolled in this study. We compared clinical manifestations of AAV between an RF-positive subset (n?=?29) and an RF-negative subset (n?=?18). The Birmingham Vasculitis Activity Score (BVAS) was higher (P?=?0.026) in the RF-positive subset than in the RF-negative subset. The levels of CRP and ESR were higher in the RF-positive patients (P?=?0.020 and P?=?0.007, respectively) compared to the RF-negative subset. IgM-RF titers were significantly correlated with the BVAS (r?=?0.50, P?=?0.0004). In addition, the IgM-RF titers had significant correlations with the levels of CRP (r?=?0.41, P?=?0.004), ESR (r?=?0.39, P?=?0.016), IgM (r?=?0.36, P?=?0.016) and IgG (r?=?0.37, P?=?0.015). The frequency of commencement of dialysis therapy, usage of mechanical ventilation and mortality were higher in the RF-positive subset than in the RF-negative subset.

Conclusions

In patients with AAV, RF titers were significantly correlated with disease activity and the levels of inflammatory markers. The presence of RF could be a poor prognostic factor in patients with AAV.
  相似文献   
72.
Babesia microti, a hemoprotozoan parasite of rodents, is also important as a zoonotic agent of human babesiosis. The Maltese cross form, which consists of four masses in an erythrocyte, is characteristic of the developmental stage of B. microti. Monoclonal antibody (MAb) 2-1E, which specifically recognizes the Maltese cross form of B. microti, has been described previously. In the present study, we examined the roles of the Maltese cross form during the infectious course of B. microti in mice. The number of the Maltese cross form increased in the peripheral blood of infected mice prior to the peak of parasitemia. With confocal laser scanning microscopy, MAb 2-1E was found to be reactive with the ring form, with the parasites undergoing transformation to the Maltese cross form and subsequent division, and also with extracellular merozoites. Furthermore, the Maltese cross form-related antigen (MRA) gene was isolated from a B. microti cDNA library by immunoscreening with MAb 2-1E, and the nucleotide sequence was determined. Genomic analyses indicated that the MRA gene exists as a single-copy gene in B. microti. Immunization of mice with recombinant MRA induced significant protective immunity against B. microti infection. These findings indicate that the Maltese cross form plays important roles in both the development of parasitemia and the protective response against the infection.  相似文献   
73.
In human testis, expression of a novel member of the aldo-keto reductase family was identified. Based on its testis-specific expression, we termed this protein human testis aldo-keto reductase (htAKR). In addition to four major isoforms, the existence of multiple alternatively spliced products of htAKR was detected using RT-PCR followed by nested PCR. htAKR was a homologue of mouse liver keto-reductase, AKR1E1, with close similarity in their genomic organizations. htAKR4, the longest isoform, was expressed as a non-fused native form. It exhibited a limited activity toward 9,10-phenanthrenequinone, while no activity toward the steroids or prostaglandins was demonstrated. Using the laser capture microdissection technique and RT-PCR, expression of htAKR was detected in testicular germ cells as well as in interstitial cells. The levels of htAKR mRNA in the tissues obtained from seminoma were much lower than those in normal testes. A significant decline in the htAKR expression was observed when NEC8, a cell line originated from a human testicular germ cell tumour, was exposed to phorbol 12-myristate 13-acetate or 5alpha-dihydrotestosterone. These results indicate that the expression of htAKR, down-regulated in the testicular tumour, is possibly controlled by mitogenic and hormonal signals.  相似文献   
74.
PURPOSE: The activation of peroxisome proliferator-activated receptor gamma (PPAR gamma) has been implicated in the inhibition of tumor progression in lung cancers through the induction of differentiation and apoptosis. Recently, we identified a novel splice variant of human PPAR gamma1 (hPPAR gamma1) that exhibits dominant-negative activity in human tumor-derived cell lines. This study aimed to examine the expression and pathophysiologic roles of a truncated splice variant of hPPAR gamma1 (hPPAR gamma1(tr)) in primary human lung cancer tissues. EXPERIMENTAL DESIGN: The expression and localization of hPPAR gamma1(tr) was surveyed in human primary lung cancer tissues using immunohistochemistry and Western blot analysis. Using transfectants stably expressing wild-type hPPAR gamma1 (hPPAR gamma1(wt)) and hPPAR gamma1(tr), we also analyzed the pathophysiologic roles of hPPAR gamma1(tr). RESULTS: We showed that PPAR gamma is expressed predominantly in the nucleus of nontumorous tissues, whereas it is present in both the nucleus and the cytoplasm of tumorous tissues in squamous cell carcinoma (SCC) of the lung. Western blot analysis confirmed the presence of PPAR gamma1(tr) in primary lung SCC tissue but not in nontumorous tissue. Expression of PPAR gamma1(tr) in Chinese hamster ovary cells attenuated their susceptibility to cell death induced by oxidative stress or cisplatin, whereas their susceptibility was completely recovered by down-regulation of PPAR gamma1(tr) with small interfering RNA. CONCLUSIONS: hPPAR gamma1(tr) is expressed strongly in tumorous tissues of primary human lung SCC and its overexpression renders transfected cells more resistant to chemotherapeutic drug- and chemical-induced cell death. These data suggest that the decreased drug sensitivity of PPAR gamma1(tr)-expressing cells may be associated with increased tumor aggressiveness and poor clinical prognosis of patients.  相似文献   
75.
Caroli's disease is a rare congenital anomaly of the liver. Since new diagnostic techniques for the evaluation of hepatic disease have been introduced, the number of reported cases of Caroli's disease has been gradually increasing. This report describes the case of a 13 year old girl with nausea, vomiting, fever and hepatomegaly. The diagnosis of Caroli's disease was established by ultrasonography and CT scan. The complications and management are discussed. The important points in management are to relieve symptoms and to conduct regular examinations by ultrasonography for the early detection of hepatobiliary carcinoma.  相似文献   
76.
Five cell lines were established from four undifferentiated carcinomas and one squamous cell carcinoma of the thyroid. The levels of several kinds of cytokines were measured in the conditioned media of these cell lines by enzyme-linked immunosorbent assay (ELISA). Interleukin-6 (IL-6) was produced by four of the five cell lines, interleukin-1α (IL-lα) by three cell lines, and granulocyte-colony stimulating factor (G-CSF) by two cell lines. The mRNA of IL-lα or IL-6 was detected by Northern blot analysis in all the cell lines which secreted these cytokines into culture medium. These results suggest that undifferentiated carcinoma and squamous cell carcinoma of the thyroid frequently produce cytokines. Further studies are needed to clarify the possible clinical effects of these cytokines in patients with thyroid carcinoma. © Wiley-Liss, Inc.  相似文献   
77.
Summary In a patient with non-palpable breast carcinoma, c-erbB-2 gene amplification was detected by means of polymerase chain reaction (PCR) in the small number of breast carcinoma cells present in nipple discharge. Amplification of the c-erbB-2 gene is more frequent in carcinoma in situ than in invasive types. Detection by a PCR-based method may help diagnose non-palpable breast carcinoma with nipple discharge. Since this gene amplification is related to high proliferation, it might provide useful preoperative information regarding intraductal carcinoma of comedo type and predict responses to chemotherapy.  相似文献   
78.
BACKGROUND: We evaluated the effect of olprinone hydrochloride on intraocular pressure (IOP) and ocular blood flow in patients after cardiac surgery under cardiopulmonary bypass (CPB). METHODS: Nine patients after cardiac surgery under CPB were investigated. We measured IOP of the left eye using tonometer (Tonopen XL, BIO RAD, Osaka), and mean blood flow velocity in the left ophthalmic artery (Vm) and calculated the pulsatility index in the left ophthalmic artery (PI) using 2 MHz Doppler ultrasound system (Multidop P, DWL, Germany). After baseline measurement, the olprinone hydrochloride loading dosage was increased from 0.15 to 0.3 microgram.kg-1.min-1 every 60 minutes. The intraocular pressure and ocular blood flow were measured at each point. RESULTS: IOP and PI decreased significantly, and Vm increased significantly at the infusion rate of 0.3 microgram.kg-1.min-1 from baseline. There was a significant linear correlations between IOP and Vm. CONCLUSION: We demonstrated that olprinone hydrochloride led to a decrease in IOP and an increase in ocular blood flow in patients after cardiac surgery under CPB.  相似文献   
79.
3,4-dihydroxyphenylacetaldehyde (DOPALD), an oxidative metabolite of dopamine (DA), induced dose-dependent DA release from pheochromocytoma (PC12) cells without affecting leakage of lactate dehydrogenase from the cells. DOPALD-induced DA release was independent of extracellular Ca2+ concentration and was not blocked by nifedipine, an L-type Ca2+ channel antagonist. These results indicated a novel intrinsic role of DOPALD in dopaminergic nerve terminals that may take part in the activation of dopamine neurons.  相似文献   
80.
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