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   8992篇
  免费   466篇
  国内免费   26篇
耳鼻咽喉   88篇
儿科学   173篇
妇产科学   105篇
基础医学   1001篇
口腔科学   245篇
临床医学   604篇
内科学   2383篇
皮肤病学   147篇
神经病学   476篇
特种医学   259篇
外科学   1677篇
综合类   35篇
预防医学   230篇
眼科学   208篇
药学   702篇
  1篇
中国医学   33篇
肿瘤学   1117篇
  2023年   43篇
  2022年   79篇
  2021年   157篇
  2020年   83篇
  2019年   118篇
  2018年   164篇
  2017年   117篇
  2016年   168篇
  2015年   173篇
  2014年   212篇
  2013年   281篇
  2012年   431篇
  2011年   397篇
  2010年   238篇
  2009年   213篇
  2008年   413篇
  2007年   425篇
  2006年   398篇
  2005年   426篇
  2004年   409篇
  2003年   402篇
  2002年   415篇
  2001年   431篇
  2000年   407篇
  1999年   355篇
  1998年   102篇
  1997年   96篇
  1996年   78篇
  1995年   75篇
  1994年   72篇
  1993年   64篇
  1992年   209篇
  1991年   189篇
  1990年   172篇
  1989年   172篇
  1988年   141篇
  1987年   155篇
  1986年   123篇
  1985年   132篇
  1984年   90篇
  1983年   76篇
  1982年   32篇
  1979年   67篇
  1978年   36篇
  1975年   34篇
  1974年   35篇
  1973年   34篇
  1972年   40篇
  1971年   45篇
  1969年   37篇
排序方式: 共有9484条查询结果,搜索用时 15 毫秒
71.
72.
Aim: Angiopoietin 1 (Ang-1) and its antagonist, angiopoietin 2 (Ang-2), are novel ligands that regulate the Tie2 receptor. The Ang-2 gene is upregulated in the hypervascular type of human hepatocellular carcinoma (HCC). To gain a better understanding of the role of the Ang-Tie2 system in HCC the expression of these genes was investigated in a series of human HCCs. METHODS: The expression of the angiopoietin and Tie2 proteins was investigated in nine normal liver tissues and 52 surgically resected HCCs. In addition, the effects of hypoxic stimuli on Ang-1, Ang-2, vascular endothelial growth factor (VEGF), and erythropoietin (EPO) expression was investigated in Hep3B cells. RESULTS: Ang-1, rather than Ang-2, was more frequently expressed in the normal liver. Ang-1 was expressed in 68% of HCCs, whereas Ang-2 was expressed in 81%, and was significantly higher in poorly differentiated HCCs characterised by high vascularity (p = 0.02), and in tumours with a peliotic change (p = 0.02). Strong expression of Tie2 was seen in tumour vessels in accordance with Ang-2 expression. In Hep3B cells, hypoxic stimuli upregulated VEGF and EPO, but not Ang-1 or Ang-2. CONCLUSIONS: These data support the evidence that the reversal of Ang-1 and Ang-2 expression plays an important role in the angiogenic and dedifferentiation processes in HCC. The hypoxic stimuli were not responsible for Ang-2 upregulation, unlike that of VEGF, in human HCC cells.  相似文献   
73.
A 4-year-old boy with atrioventricular discordance, double-outlet right ventricle, pulmonary stenosis, and mitral regurgitation, was undergoing anatomical repair consisting of Senning, Rastelli, Damus–Kaye–Stansel procedures, and a mitral valve repair, complained of post-operative excessive airway tract secretion, which ultimately developed into acute respiratory distress syndrome (ARDS) 28 days after the operation. The cause of the ARDS was thought to be frequent manual positive pressure recruitment and prolonged inhalation of pure oxygen. At 45 days after the operation, hypercapnia and respiratory acidosis turned out to be irreversible, and therefore, veno-arterial extracorporeal membrane oxygenation (ECMO) was established utilizing the Endumo®4000 system. Pulmonic interstitial inflammation gradually improved while resting the lung under ECMO support; however, effective ventilation volume decreased critically because a massive pulmonary hemorrhage occurred at 2 and 9 days after the initiation of ECMO. To maximize the effectiveness of respiratory physical therapy, “Awake ECMO” was started and tidal volume dramatically increased with a regained cough reflex. Five days later, he was successfully weaned off from ECMO, and discharged 7 months after the operation without any neurological and physiological sequelae.  相似文献   
74.
Summary The histopathology of the liver and the detectability of intrahepatic hepatitis B virus (HBV) markers were studied in 34 autopsy cases in elderly patients (mean age 73.9 years, range 60–91 years) who had had a history of positive HBV surface antigenaemia prior to death. Seven of 14 persistent HBV carrier cases (group A) in which long-lasting HBV surface antigen (HBsAg) carriage in the sera had been confirmed by sequential assays, and 5 out of 15 HBV-infected people (group C, single assay) showed significant primary liver damages including chronic hepatitis, toxic hepatitis, liver cirrhosis and hepatocellular carcinoma. In 5 cases (group B), one of which was type B liver cirrhosis, HBsAg became negative and HBsAb appeared during the follow-up period (up to 33 months). Among confirmed HBV carriers, HBsAg and HBV core antigen were most frequently found in the liver of cirrhotic cases with and without hepatocellular carcinoma (5 of 6), whereas these were rarely detected in those with nonspecific changes or slight hepatitic activity (1 of 7). All 5 cases in group B were negative for histological HBV-related antigens and the findings in group C were variously interpreted. Post-mortem cases of the aged HBV carriers who survived their mean life expectancy represent an important population in which to study the natural history of HBV carriers.  相似文献   
75.
The design of a noninvasive reflectance pulse oximeter that uses the same principle of transmittance pulse oximeter and analyses the oxygen saturation of arterial blood was described. Four sets of red and infra-red LEDs were used as light sources. The respective reflectance photoelectric outputs were used to make an internal calibration curve of the instrument relative to the arterial oxygen saturation values measured with a Co-Oximeter (OSM-3) in five healthy nonsmoking subjects during steady-state hypoxaemia. The accuracy of the present instrument was studied in six patients with respiratory failure. From 22 samples, a good correlation coefficient (0.98) with a standard deviation of 1.42 was obtained in the range between 73 and 100 per cent between the arterial oxygen saturation measured with the present instrument and that with the Co-Oximeter. The result strongly suggests the usefulness of this oximeter in monitoring patients with hypoxaemia.  相似文献   
76.
Molecular size and charge distribution of IgA of sera and glomerular eluates were investigated in ddY mice, spontaneously developing mesangial proliferative glomerulonephritis (GN) with IgA deposition after 40 weeks of age. Serum IgA levels were increased in aged ddY mice more than 40 weeks old with a significant increase (P less than 0.01) at the age of 60 weeks, comparing with those of BALB/c mice. The isoelectric focusing (IEF) spectrotype of pooled serum IgA in 60-week-old mice ranged from 4.2 to 5.5, being similar to those in younger ddY (16 weeks old) and control BALB/c mice (12 weeks old) without enhanced expression of specific IgA peaks. However, IgA in the glomerular eluate from the 60-week-old mice showed limited anionic spectrotypes from pH 4.2 to 4.8. HPLC of IgA in pooled sera and glomerular eluates of 16-, 40- and 60-week-old ddY mice, revealed markedly increased ratios of the dimeric IgA (dIgA) and polymeric IgA (pIgA) in the total IgA with age. In the contrast to serum profiles, monomeric IgA (mIgA) was always detected as the smallest peak of the IgA fractions in glomerular eluates. Furthermore, aged mice with severe GN showed a higher percentage of dIgA and pIgA in total IgA (80%) in the sera than that of the mice with mild GN (64%). HPLC analysis under acid condition of glomerular IgA from 40-week-old ddY mice showed a similar pattern of dIgA and pIgA peaks in neutral buffer without the appearance of mIgA. These findings suggest that there is a selective mechanism for glomerular accumulation of more acid IgA among the polyclonally expanded IgA in old ddY mice, and that the polymeric form of IgA plays a pathogenic role in the development of mesangial proliferative GN in these mice.  相似文献   
77.
To clarify the effect of secretory IgA (sIgA) deficiency on gut homeostasis, we examined intraepithelial lymphocytes (IELs) in the small intestine (SI) of polymeric immunoglobulin receptor-deficient (pIgR−/−) mice. The pIgR−/− mice exhibited the accumulation of CD8αβ+ T-cell receptor (TCR)-αβ+ IELs (CD8αβ+αβ-IELs) after weaning, but no increase of CD8αβ+γδ-IELs was detected in pIgR−/− TCR-β−/− mice compared with pIgR+/+ TCR-β−/− mice. When 5-bromo-2′-deoxyuridine (BrdU) was given for 14 days, the proportion of BrdU-labelled cells in SI-IELs was not different between pIgR+/+ mice and pIgR−/− mice. However, the proportion of BrdU-labelled CD8αβ+-IELs became higher in pIgR−/− mice than pIgR+/+ mice 10 days after discontinuing BrdU-labelling. Intravenously transferred splenic T cells migrated into the intraepithelial compartments of pIgR+/+ TCR-β−/− mice and pIgR−/− TCR-β−/− mice to a similar extent. In contrast, in the case of injection of immature bone marrow cells, CD8αβ+αβ-IELs increased much more in the SI of pIgR−/− TCR-β−/− mice than pIgR+/+ TCR-β−/− mice 8 weeks after the transfer. αβ-IELs from pIgR−/− mice could produce more interferon-γ and interleukin-17 than those of pIgR+/+ mice, and intestinal permeability tended to increase in the SI of pIgR−/− mice with aging. Taken together, these results indicate that activated CD8αβ+αβ-IELs preferentially accumulate in pIgR−/− mice through the enhanced differentiation of immature haematopoietic precursor cells, which may subsequently result in the disruption of epithelial integrity.  相似文献   
78.

Background

Maspin is known to be a tumor suppressor protein and its prognostic significance in patients with several types of cancer has been reported. To date, however, no study has focused on the association between maspin expression and the prognosis of patients with adenocarcinoma of the uterine cervix. We explored the prognostic value of maspin expression with particular reference to its subcellular localization in patients with adenocarcinoma of the uterine cervix.

Methods

Paraffin-embedded tissue samples from 46 patients diagnosed as adenocarcinoma of the uterine cervix were immunohistochemically analyzed using an antibody for maspin. The patients were followed up for 3 to 165 months (median: 64.2 months) and the prognostic value was evaluated by the log-rank test and the Cox regression hazard model.

Results

A sample was considered maspin-positive if maspin was expressed in only the cytoplasm; 69.6% (32 cases) of the specimens were maspin-positive, and there was significant correlation between positivity and recurrence (P = 0.022). Maspin-positive patients had both shorter disease free survival and shorter overall survival by the log-rank test (P = 0.023, P = 0.043, respectively). By Cox’s multivariate analysis, the International Federation of Obstetrics and Gynecology (FIGO) status was the only independent prognostic factor for disease free survival and overall survival in patients with adenocarcinoma of the uterine cervix.

Conclusion

This is the first report to reveal an association between cytoplasmic maspin expression and the prognosis of patients with adenocarcinoma of the uterine cervix. Although further studies with a larger series of patients and a longer follow up period are necessary, the present results suggest that cytoplasmic maspin expression could be an indicator of unfavorable prognosis in patients with adenocarcinoma of the uterine cervix.  相似文献   
79.
80.
To elucidate the pathogenesis of amyloid deposition associated with familial amyloidotic polyneuropathy (FAP), we developed several transgenic mouse lines carrying the human mutant transthyretin (TTR) gene. We found that human TTR and mouse serum amyloid P component (SAP) are deposited as amyloid in tissues of these mouse lines. Because SAP is a major acute-phase reactant in mice, we asked whether repeated injections of Escherichia coli lipopolysaccharide (LPS) would enhance the amyloid deposition in one of these transgenic mouse lines. During the course of repeated LPS injections, serum levels of SAP in the transgenic mice remained between severalfold to about 50-fold higher than seen in the absence of stimulation. As no significant difference was detected in the onset, progression, and tissue distribution of TTR-derived amyloid (ATTR) deposition between the LPS-stimulated and unstimulated transgenic mice, the induction of SAP synthesis by acute inflammation probably does not affect the onset and extent of ATTR deposition.  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