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   1792篇
  免费   84篇
  国内免费   10篇
耳鼻咽喉   8篇
儿科学   37篇
妇产科学   101篇
基础医学   210篇
口腔科学   3篇
临床医学   169篇
内科学   538篇
皮肤病学   56篇
神经病学   101篇
特种医学   41篇
外科学   161篇
综合类   19篇
一般理论   1篇
预防医学   56篇
眼科学   57篇
药学   173篇
中国医学   58篇
肿瘤学   97篇
  2023年   5篇
  2022年   5篇
  2021年   24篇
  2020年   14篇
  2019年   22篇
  2018年   33篇
  2017年   13篇
  2016年   20篇
  2015年   43篇
  2014年   51篇
  2013年   72篇
  2012年   124篇
  2011年   98篇
  2010年   91篇
  2009年   65篇
  2008年   101篇
  2007年   149篇
  2006年   135篇
  2005年   119篇
  2004年   88篇
  2003年   84篇
  2002年   86篇
  2001年   85篇
  2000年   55篇
  1999年   62篇
  1998年   27篇
  1997年   13篇
  1996年   15篇
  1995年   11篇
  1994年   16篇
  1993年   9篇
  1992年   28篇
  1991年   25篇
  1990年   24篇
  1989年   7篇
  1988年   14篇
  1987年   19篇
  1986年   7篇
  1985年   13篇
  1984年   6篇
  1983年   3篇
  1981年   1篇
  1977年   1篇
  1975年   2篇
  1974年   1篇
排序方式: 共有1886条查询结果,搜索用时 453 毫秒
21.
The occurrence of nephrosis in the first 3 months of life is rare and is termed ’congenital nephrotic syndrome.’ The congenital nephrotic syndrome is a group of heterogeneous diseases with a clinical course that differs markedly from the childhood nephrotic syndrome. The coexistence of a congenital nephrotic syndrome and gonadal dysgenesis in a 46,XY karyotype with normal female external genitalia is extremely rare. Frequent severe infections are often seen in the Finnish type, but sepsis leading to death is rare in the neonatal onset of gonadal dysgenesis. This report describes an unusual case of complete XY gonadal dysgenesis in a 46,XY female neonate with the congenital nephrotic syndrome and overwhelming sepsis. Received: 4 January 1999 / Revised: 24 May 1999 / Accepted: 25 May 1999  相似文献   
22.
Recent studies suggest that variants of the DLST gene alter the risk of AD. DLST encodes the core subunit of the mitochondrial alpha-ketoglutarate dehydrogenase complex, which is deficient in AD. The authors report that in 247 US white subjects, homozygosity for DLST A19,117, T19,183 was associated with a reduced risk of AD (odds ratio [OR] = 0.35, p = 0.018). The reduced risk was marked in subjects who did not carry the apolipoprotein (APOE)-4 allele (OR = 0.16, p = 0.014). Further study of DLST in AD appears warranted.  相似文献   
23.
PURPOSE: This study was conducted to determine whether relatives of gastric cancer patients (GCF) showed greater gastric cycloxygenase-2 (COX-2) expression or a greater incidence of precancerous lesions after Helicobacter pylori infection and whether H. pylori eradication could reduce COX-2 expression. EXPERIMENTAL DESIGN: Three hundred subjects were enrolled in this study: half were relatives of 50 H. pylori-infected gastric cancer patients, and half were relatives of 50 H. pylori-infected duodenal ulcer (DU) patients (controls). Each relative underwent endoscopy to detect H. pylori infection and related gastric histology. One hundred and twenty GCFs were found to have H. pylori infection. After H. pylori eradication, 90 of the 120 GCFs were followed up with annual endoscopy examinations over the next 2 years. Gastric COX-2 intensity in all of the specimens collected from these patients was immunochemically stained and graded from 0 to 4. RESULTS: H. pylori infection, gastric atrophy, and intestinal metaplasia (IM) were more prevalent in GCFs than in relatives of H. pylori-infected patients with DUs (P < 0.05). H. pylori-infected GCFs also showed a greater COX-2 intensity than H. pylori-infected relatives of patients with DUs (89.1% versus 62.7%, P < 0.001; relative risk: 4.9; 95% confidence interval: approximately 2.34-10.29). Among the H. pylori-infected GCFs, COX-2 intensity correlated with atrophy and IM (P < 0.001). After H. pylori eradication, gastric COX-2 expression disappeared only in those relatives without IM (P < 0.001). CONCLUSIONS: GCFs are more likely to show greater gastric COX-2 expression and a higher incidence of precancerous lesions after H. pylori infection than the relatives of H. pylori-infected patients with only DUs. H. pylori eradication can reverse gastric COX-2 expression in patients without IM but not in patients with IM.  相似文献   
24.
The aim of this study was to characterize the effects of hypotonicity on the activity of large-conductance Ca(2+)-activated K+ (BK(Ca)) channels in human retinal pigment epithelial (RPE R-50) cells. Effects of hypotonicity on ion currents were investigated with the aid of the patch-clamp technique. A regulatory volume decrease in response to a hypotonic solution (200 mOsm/L) was observed that could be blunted by paxilline. In whole-cell current recordings, a hypotonic solution (200 mOsm/L) reversibly increased the amplitude of K+ outward currents (I(K)). The increase of I(K) could be reversed by iberiotoxin (200 nM), paxilline (1 microM), or tetrandrine (5 microM), but not by glibenclamide (10 microM), disulphonic acid (DIDS) (100 microM), or dequalinium dichloride (10 microM). In RPE R-50 cells pretreated with thapsigargin, aristolochic acid, or pertussis toxin, the increased amplitude of I(K) in response to hypotonicity was unaltered. In cell-attached patches, an increase in BK(Ca)-channel activity was observed during hypotonicity-induced cell swelling. The enhanced channel activity elicited under this condition was mainly mediated by an increase in the number of long-lived openings. These findings support the evidence for the coupling of volume swelling to the functional activity of BK(Ca) channels.  相似文献   
25.
Current role of local ablative treatments for hepatocellular carcinoma.   总被引:3,自引:0,他引:3  
Due to modern diagnostic imaging and the sensitive alpha-fetoprotein test, small hepatocellular carcinoma can now be detected at an early stage. Studies have shown that surgical resection of the tumors is a valuable treatment. Local treatment under ultrasound guidance was initially considered as an alternative when patients' liver reserves were not good enough for surgical resection; however, this technique has been improved and the results indicate that its survival rate can compete with that of surgical resection. In follow-up studies of patients with small hepatocellular carcinoma, a 5-year survival of 60% has been achieved after percutaneous ethanol injection therapy. Percutaneous microwave coagulation therapy and percutaneous radiofrequency ablation therapy have been shown to have some advantages over percutaneous ethanol injection therapy, although the follow-up durations of these studies were not long enough. Percutaneous ethanol injection therapy, percutaneous microwave coagulation therapy and percutaneous radiofrequency ablation therapy have become the 3 most widely used techniques for the treatment of hepatocellular carcinomas that are less than 5 cm in diameter and have a tumor number less than 3. In general, a tumor size of 3 to 5 cm is a good candidate for radiofrequency ablation and a tumor size of 2 to 3 cm is suitable for radiofrequency ablation or microwave coagulation. If the tumor size is around 2 cm or less, microwave coagulation or ethanol injection is often chosen due to the relatively low cost and similar efficacy. Ethanol injection also has the advantage of needing only a fine needle for injection. Informed selection of the appropriate technique, or combining a technique with transcatheter hepatic arterial embolization according to the tumor size and number, might provide the most effective treatment and achieve better results for hepatocellular carcinoma, even if the liver reserve is not good. However, large-scale, randomized, controlled trials are required before a definitive conclusion can be reached.  相似文献   
26.
BACKGROUND AND PURPOSE: Percutaneous microwave coagulation therapy (PMCT) can effectively treat hepatocellular carcinomas (HCCs) smaller than 2 cm. However, for tumors 2 to 3 cm in size, combination of transarterial chemoembolization (TACE) or multiple insertions of electrodes may be more effective. This study investigated the treatment efficacy of PMCT for tumors 2 to 3 cm in size. METHODS: Nineteen HCCs smaller than 3 cm in diameter (< 2 cm in 11, and 2-3 cm in 8) in 18 patients (including 14 previously treated patients) were treated by PMCT under ultrasound guidance. One or 2 PMCT electrodes were consecutively inserted either into the left and right portion, or into the distal and proximal portion of the tumor, according to the size, shape, and margin of tumors and puncture direction. Liver function tests and contrast-enhanced computed tomography were used to examine preoperative status and response to PMCT. RESULTS: After an average of 1.6 emissions of PMCT, 18 tumors (95%) were completely ablated. The only case of treatment failure was due to a tumor location which made the approach of the electrode difficult. Bacteremia developed after the procedure in 1 patient (5%) and local inflammatory reaction of the puncture wound in another (5%). During follow-up ranging from 5 to 19 months, no recurrence was noted at the site of the original tumors. Tumor recurrence was detected at another site 2-9 months after PMCT in 9 of the 14 previously treated patients. CONCLUSION: PMCT can effectively and safely treat HCCs smaller than 3 cm in size without combination of TACE or multiple insertions of electrodes.  相似文献   
27.
28.

Background

For patients with hepatocellular carcinoma (HCC) not eligible for surgical resection, radiofrequency ablation (RFA) is a promising technique that reduces the risk of disease progression.

Objectives

To evaluate whether the trend of image guidance for RFA is moving toward the more expensive computed tomography (CT) technology and to determine the clinical benefits of CT guidance over the ultrasound (US) guidance.

Methods

A cohort of 463 patients was identified from the Surveillance, Epidemiology, and End Results and Medicare–linked database. The temporal trends in use of image guidance were assessed using the Cochrane–Armitage test. The associations between modality of image guidance and survival, complications, and costs were assessed using the Cox regression model, the logistic regression model, and the generalized linear model, respectively.

Results

The use of CT-guided RFA increased sharply, from 20.7% in 2002 to 75.9% in 2011. Compared with CT-guided RFA, those who received US-guided RFA had comparable risk of periprocedural and delayed postprocedural complications. Stratified analyses by tumor size also showed no statistically significant difference. In adjusted survival analysis, no statistically significant difference was observed in overall and cancer-specific survival. Nevertheless, the cost of CT-guided RFA ($2847) was higher than that of US-guided RFA ($1862).

Conclusions

Despite its rapid adoption over time, CT-guided RFA incurred higher procedural costs than US-guided RFA but did not significantly improve postprocedural complications and survival. Echoing the American Board of Internal Medicine’s Choosing Wisely campaign and the American Society of Clinical Oncology’s Value of Cancer Care initiative, findings from our study call for critical evaluation of whether CT-guided RFA provides high-value care for patients with HCC.  相似文献   
29.
30.
Nobiletin, a bioactive polymethoxylated flavone (5,6,7,8,3',4'‐hexamethoxyflavone), is abundant in citrus fruit peel. Although nobiletin exhibits antitumor activity against various cancer cells, the effect of nobiletin on glioma cells remains unclear. The aim of this study was to determine the effects of nobiletin on the human U87 and Hs683 glioma cell lines. Treating glioma cells with nobiletin (20–100 µm ) reduced cell viability and arrested the cell cycle in the G0/G1 phase, as detected using a 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay and propidium iodide (PI) staining, respectively; however, nobiletin did not induce cell apoptosis according to PI‐annexin V double staining. Data from western blotting showed that nobiletin significantly attenuated the expression of cyclin D1, cyclin‐dependent kinase 2, cyclin‐dependent kinase 4, and E2 promoter‐binding factor 1 (E2F1) and the phosphorylation of Akt/protein kinase B and mitogen‐activated protein kinases, including p38, extracellular signal‐regulated kinase, and c‐Jun N‐terminal kinase. Our data also showed that nobiletin inhibited glioma cell migration, as detected by both functional wound healing and transwell migration assays. Altogether, the present results suggest that nobiletin inhibits mitogen‐activated protein kinase and Akt/protein kinase B pathways and downregulates positive regulators of the cell cycle, leading to subsequent suppression of glioma cell proliferation and migration. Our findings evidence that nobiletin may have potential for treating glioblastoma multiforme. Copyright © 2015 John Wiley & Sons, Ltd.  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