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   2859篇
  免费   128篇
  国内免费   6篇
耳鼻咽喉   9篇
儿科学   39篇
妇产科学   25篇
基础医学   269篇
口腔科学   78篇
临床医学   223篇
内科学   685篇
皮肤病学   96篇
神经病学   221篇
特种医学   83篇
外科学   597篇
综合类   7篇
预防医学   80篇
眼科学   39篇
药学   182篇
中国医学   6篇
肿瘤学   354篇
  2022年   28篇
  2021年   67篇
  2020年   20篇
  2019年   19篇
  2018年   37篇
  2017年   26篇
  2016年   52篇
  2015年   40篇
  2014年   68篇
  2013年   85篇
  2012年   111篇
  2011年   149篇
  2010年   94篇
  2009年   68篇
  2008年   124篇
  2007年   124篇
  2006年   100篇
  2005年   114篇
  2004年   111篇
  2003年   135篇
  2002年   126篇
  2001年   117篇
  2000年   90篇
  1999年   116篇
  1998年   42篇
  1997年   43篇
  1996年   32篇
  1995年   21篇
  1994年   22篇
  1993年   23篇
  1992年   80篇
  1991年   72篇
  1990年   57篇
  1989年   54篇
  1988年   50篇
  1987年   56篇
  1986年   46篇
  1985年   62篇
  1984年   28篇
  1983年   32篇
  1981年   13篇
  1979年   20篇
  1978年   19篇
  1977年   18篇
  1975年   17篇
  1974年   13篇
  1973年   17篇
  1972年   14篇
  1969年   26篇
  1968年   16篇
排序方式: 共有2993条查询结果,搜索用时 0 毫秒
81.
Distinguishing corticobasal degeneration (CBD) from progressive supranuclear palsy (PSP) is clinically and pathologically difficult, and a useful biological marker to discriminative these two diseases has been a subject of clinical interest. In the present study, we assessed tau protein levels in cerebrospinal fluids by sandwich ELISA to distinguish CBD from PSP. The subjects consisted of 27 cases of CBD, 30 cases of PSP, and 36 healthy controls (CTL). The tau values in CBD were significantly higher than those in PSP (P<0.001) and those in CTL (P<0.001). The assay of CSF tau provided diagnostic sensitivity of 81.5% and specificity of 80.0% between CBD and PSP according to receiver-operating characteristic (ROC) curve analysis. When values were compared separately with respect to stage of the disease, differences in the values for moderate CBD vs. moderate PSP had the greatest significance (P<0.001 sensitivity 92.3%, specificity 100.0%), followed by cases of mild CBD and PSP (P<0.005, sensitivity 100.0%, specificity 87.5%). The values in severe CBD and PSP were not significantly different (P=0.07, sensitivity 100%, specificity 75.0%). Using data obtained from a larger number of disease cases, we confirmed our previous findings that tau protein levels in cerebrospinal fluids in patients with CBD are significantly higher than those in patients with PSP. Because tau protein levels in cerebrospinal fluids are significantly higher in early CBD cases than in early PSP cases, measurement of tau protein levels in cerberospinal fluids may be useful for the differential diagnosis of early CBD from early PSP.  相似文献   
82.
83.
Aim: The present study was undertaken to evaluate the effects of 1‐O‐hexyl‐2,3,5‐trimethylhydroquinone (HTHQ), a synthesized vitamin E derivative, on carbon tetrachloride (CCl4)‐induced cirrhosis. Methods: Rats were treated with hypodermic injections of CCl4 twice a week to induce the hepatic cirrhosis, and given drinking water containing HTHQ or solvent. Primary cultures of rat hepatocytes were performed to evaluate the effects of HTHQ on the expression of inducible nitric oxide synthase (iNOS). Results: Masson's staining of rat livers showed fibrosis around pseudo‐lobules in the CCl4 group, the lesions being reduced in the CCl4 HTHQ group. Increases in liver tissue hydroxyproline and α1(I) collagen, α‐smooth muscle actin and iNOS induced by CCl4, were also markedly diminished by HTHQ. Furthermore, both HTHQ and vitamin E attenuated interleukin‐1β‐induced iNOS protein expression in cultured hepatocytes, the potency of HTHQ being 10‐times higher than that of vitamin E. Conclusion: HTHQ may inhibit development of hepatic cirrhosis in rats, more potently than vitamin E, by inhibiting the iNOS expression in hepatocytes. Because vitamin E has a radical scavenging action, roles of NO and peroxynitrite will be discussed in the effects of HTHQ on the fibrosis.  相似文献   
84.

Background

This study was conducted to evaluate Japanese treatment guidelines for patients with chronic hepatitis C virus (HCV) infection and normal alanine aminotransferase (N-ALT) levels from the viewpoint of the incidence of hepatocellular carcinoma (HCC).

Methods

Four groups of patients with chronic HCV infection treated with pegylated interferon (Peg-IFN) plus ribavirin, and classified according to the N-ALT guidelines, were examined for HCC incidence: group A (n = 353), ALT ≤30 IU/L and platelet (PLT) ≥15 × 104/mm3; group B (n = 123), ALT ≤30 IU/L and PLT <15 × 104/mm3; group C (n = 233), 30 < ALT ≤ 40 IU/L and PLT ≥15 × 104/mm3; and group D (n = 100), 30 < ALT ≤ 40 IU/L and PLT <15 × 104/mm3. The mean observation period was 36.2 ± 16.5 months

Results

In groups A and C, the HCC incidence was low even in patients with non-response (NR) (cumulative rates at 3 years, 0.0 and 2.9 %, respectively). In groups B and D, 14.5 and 5.3 % of NR patients had developed HCC at 3 years, but none of the patients with sustained virologic response (SVR) or relapse had developed HCC. In group B, no patients with mild fibrosis developed HCC irrespective of the antiviral effect of the treatment. Among patients with PLT <15 × 104/mm3 (group B plus group D), the HCC incidence was significantly lower in patients with SVR and relapse than in NR patients (p < 0.001, p = 0.021, respectively).

Conclusion

These results suggest that N-ALT patients with PLT <15 × 104/mm3 could be candidates for early antiviral therapy.  相似文献   
85.
86.
Sarcoplasmic reticulum (SR) Ca release has been shown not to be the predominant mechanism responsible for excitation-contraction (E-C) coupling in fetal myocytes. However, most of the studies have been conducted either on primary cultures or acutely isolated cells, in which an apparent reduction of ryanodine receptor density have been reported. We aimed to elucidate the contribution of SR Ca release and Ca transporters on sarcolemmal channels to Ca transients in fetal mouse whole hearts. On embryonic day 13.5, ryanodine significantly reduced the amplitude of the Ca transient to 27.2 ± 4.4% of the control, and both nickel and SEA0400 significantly prolonged the time to peak from 84 ± 2 ms to 140 ± 5 ms and 129 ± 6 ms, respectively, whereas nifedipine did not alter it. Therefore, at early fetal stages, SR Ca release should be an important component of E-C coupling, and T-type Ca channel and reverse mode sodium-calcium exchanger (NCX)-mediated SR Ca release could be the predominant contributors. Using embryonic mouse cultured cardiomyocytes, we showed that both nifedipine and nickel inhibited the ability of NCX to extrude Ca from the cytosol. From these results, we propose a novel idea concerning E-C coupling in immature heart.  相似文献   
87.
An extremely rare case of malignant fibrous histiocytoma In the pancreas Is reported. A 70-year-old man complained of upper abdominal discomfort. A tumor in the head of the pancreas was demonstrated by ultrasonography and computed tomography. The surgical specimen revealed a relatively well demarcated tumor, 9 × 7 × 6.5cm in size. Microscopically, fibroblastic, histiocytic, and muitinucleated giant tumor cells were observed in the myxoid area, but some tumor cells had proliferated in a storiform-pleomorphlc pattern. Immunohtstochemically, some tumor cells were positive for lysozyme, α-1-antitrypsin, α-1-antichymotrypsin, and vimentin. Electron microscopically, tumor cells showed a combination of fibroblastic and histiocytic features. The patient Is currently well with no evidence of recurrence or metastasis 22 months after operation.  相似文献   
88.
Anti‐endothelial cell antibodies (AECA) have been frequently detected in systemic vasculitis, which affects blood vessels of various sizes. To understand the pathogenic roles of AECA in systemic vasculitis, we attempted to identify target antigens for AECA comprehensively by a proteomic approach. Proteins extracted from human umbilical vein endothelial cells (HUVEC) were separated by two‐dimensional electrophoresis, and Western blotting was subsequently conducted using sera from patients with systemic vasculitis. As a result, 53 autoantigenic protein spots for AECA were detected, nine of which were identified by mass spectrometry. One of the identified proteins was peroxiredoxin 2 (Prx2), an anti‐oxidant enzyme. Frequency of anti‐Prx2 autoantibodies, measured by enzyme‐linked immunosorbent assay (ELISA), was significantly higher in systemic vasculitis (60%) compared to those in collagen diseases without clinical vasculitis (7%, P < 0·01) and healthy individuals (0%, P < 0·01). Further, the titres changed in parallel with the disease activity during time–courses. The presence of anti‐Prx2 autoantibodies correlated significantly with elevation of serum d ‐dimers and thrombin–antithrombin complex (P < 0·05). Immunocytochemical analysis revealed that live endothelial cells expressed Prx2 on their surface. Interestingly, stimulation of HUVEC with rabbit anti‐Prx2 antibodies increased secretion of interleukin (IL)‐6, IL‐1β, IL‐1ra, growth regulated oncogene (GRO)‐α, granulocyte colony‐stimulating factor (G‐CSF), granulocyte macrophage colony‐stimulating factor (GM–CSF), IL‐8 and monocyte chemoattractant protein (MCP)‐1 more than twofold compared to that of with rabbit immunoglobulin (Ig)G. Taken together, our data suggest that anti‐Prx2 autoantibodies would be a useful marker for systemic vasculitis and would be involved in the inflammatory processes of systemic vasculitis.  相似文献   
89.
Background: Airway viral infections provoke exacerbations of asthma and chronic obstructive pulmonary disease. B7-H1 is a costimulatory molecule that is implicated in an escape mechanism of viruses from host immune systems. This escape may be associated with the persistence of viral infection and lead to exacerbation of underlying diseases. We have shown that an analog of viral double-stranded RNA, polyinosinic-polycytidylic acid (poly IC), upregulated the expression of B7-H1 on airway epithelial cells, an effect which was corticosteroid-resistant. We investigated the effects of corticosteroids plus long-acting β(2)-agonists (LABAs; fluticasone/salmeterol or budesonide/formoterol) on the expression of B7-H1. Methods: BEAS-2B cells and primary airway epithelial cells were stimulated with poly IC or respiratory syncytial virus. The expression of B7-H1 was assessed by flow cytometry. Results: Poly IC upregulated the expression of B7-H1, which was suppressed by high-concentration corticosteroids but not by LABAs. The upregulation was suppressed by very low-concentration corticosteroids when used in combination with LABAs. Their combination also suppressed the virus-induced upregulation of B7-H1. Poly IC stimulation induced the nuclear translocation of nuclear factor ?B (NF-?B). Inhibitors of NF-?B activation prevented the poly IC-induced upregulation of B7-H1. Low-concentration corticosteroids in combination with LABAs enhanced the de novo induction of I?Bα, the endogenous inhibitor of NF-?B activation. Conclusions: Fluticasone/salmeterol or budesonide/formoterol attenuate the virus-associated upregulation of B7-H1 on airway epithelial cells via suppression of NF-?B activation.  相似文献   
90.
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