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   598篇
  免费   32篇
  国内免费   7篇
耳鼻咽喉   2篇
儿科学   30篇
妇产科学   24篇
基础医学   50篇
口腔科学   33篇
临床医学   50篇
内科学   115篇
皮肤病学   17篇
神经病学   9篇
特种医学   99篇
外科学   79篇
综合类   24篇
预防医学   33篇
眼科学   7篇
药学   48篇
中国医学   1篇
肿瘤学   16篇
  2021年   16篇
  2020年   5篇
  2019年   2篇
  2018年   10篇
  2017年   6篇
  2016年   13篇
  2015年   12篇
  2014年   15篇
  2013年   28篇
  2012年   24篇
  2011年   17篇
  2010年   29篇
  2009年   29篇
  2008年   16篇
  2007年   16篇
  2006年   20篇
  2005年   15篇
  2004年   9篇
  2003年   13篇
  2002年   10篇
  2001年   13篇
  2000年   8篇
  1999年   22篇
  1998年   35篇
  1997年   25篇
  1996年   22篇
  1995年   13篇
  1994年   22篇
  1993年   23篇
  1992年   8篇
  1991年   6篇
  1990年   5篇
  1989年   13篇
  1988年   15篇
  1987年   9篇
  1986年   15篇
  1985年   7篇
  1984年   8篇
  1983年   6篇
  1982年   9篇
  1981年   12篇
  1980年   12篇
  1979年   1篇
  1978年   4篇
  1977年   5篇
  1976年   9篇
  1975年   2篇
  1974年   1篇
  1957年   1篇
  1955年   1篇
排序方式: 共有637条查询结果,搜索用时 15 毫秒
21.

Introduction

Magnetic resonance cholangiopancreatography (MRCP) is not a routine investigation to exclude choledocholithiasis unless there is clinical or biochemical suspicion of common bile duct (CBD) stones. This study attempted to determine which radiological or serological parameters best predicted CBD stones.

Methods

All patients undergoing MRCP from 2005 to 2011 were selected. Patients with pancreatitis were excluded. Liver function tests (LFTs) at admission and prior to MRCP were recorded, as was abdominal ultrasonography and MRCP results. Parameters measured routinely on LFTs included alkaline phosphatase (ALP), alanine transaminase (ALT) and bilirubin. Receiver operating characteristic curve area analysis (area under the curve [AUC]) and chi-squared analysis were undertaken.

Results

Overall, 195 patients were identified, 71 of whom had CBD stones on MRCP. Raised ALP levels on admission demonstrated a correlation with CBD stones (AUC: 0.619, odds ratio [OR]: 3.16, p=0.06). At ultrasonography, a dilated CBD (OR: 3.76, p<0.001) and intrahepatic duct dilation (OR: 5.56, p<0.001) were highly significant predictors. However, only 37% of patients had a dilated CBD on ultrasonography. Ongoing elevation of LFT parameters, particularly ALP (AUC: 0.707, OR: 4.64, p<0.001) and ALT (AUC: 0.646, OR: 5.40, p<0.001), displayed a significant correlation with CBD stones.

Conclusions

Ongoing (even if minor) elevations of liver function test parameters should prompt the need to exclude CBD stones even in the presence of a normal CBD diameter on ultrasonography.  相似文献   
22.
Thrombin causes subsecond changes in protein phosphorylation of platelets   总被引:1,自引:0,他引:1  
Carty  DJ; Spielberg  F; Gear  AR 《Blood》1986,67(6):1738-1743
We have developed a general quenched-flow approach to study platelet function as early as 0.3 seconds after stimulation. Phosphorylation of 20- and 40-kd proteins has been analyzed during the first five seconds of platelet response to thrombin from 0.1 to 5.0 U/mL and compared with the progress of aggregation and serotonin secretion. The onset time for aggregation and phosphorylation of both proteins was less than one second, although with lowest (less than 0.5 U/mL) thrombin levels, a lag of up to 0.6 seconds occurred before 40K phosphorylation increased. The thrombin sensitivity of aggregation and 20K phosphorylation was approximately twice that of 40K phosphorylation, with Ka values of 0.51 and 0.53 v 1.10 U/mL, respectively. External calcium was necessary for maximal 20K phosphorylation, since EDTA inhibited this by 30%. The 40K phosphorylation was not affected by EDTA. Platelet activation by thrombin thus induced biochemical changes well before one second. The quenched-flow approach may help to reveal relationships between phospholipase activation, calcium fluxes, and protein phosphorylation during these early periods of platelet function.  相似文献   
23.
Thompson  AR; Chen  SH; Smith  KJ 《Blood》1988,72(5):1633-1638
In hemophilia B, assays based on a monoclonal antifactor IX specific for the Thr-148 variant of an exonic polymorphism have diagnosed carriers in selected families by either establishing linkage or by indicating the presence or absence of a given normal factor IX. The sensitivity of the immunoassays for detecting heterozygous women was explored by comparing results from immunoassays with solid-phase polyclonal v the monoclonal antifactor IXs. Factor IX with the normal Ala-148 variant gave a flat dilution curve, qualitatively distinct from factor IX with the Thr-148 variant in the monoclonal assay. The two were indistinguishable in the polyclonal assay. Mixtures of equal amounts of the two types gave an intermediate result, about half as reactive in the monoclonal as compared with the polyclonal assay system. Whereas mixtures with 10% Ala-148 and 90% Thr-148 factor IXs could not readily be distinguished from Thr-148 factor IX plasma, as little as 1% of the Thr-148 protein was detected in Ala-148 factor IX plasma. The frequency of the Ala-148 variant varied in individuals with different ethnic backgrounds; it was found in 29% of white, 12% of black, and none of Asian blood donors' factor IX genes in Seattle. Only 4% of samples from South African black men were nonreactive (ie, Ala- 148). The Thr/Ala-148 dimorphism is in strong linkage disequilibrium with Taql restriction fragment length polymorphisms (RFLPs). Three recombinations were noted in normal white genes and one in a normal black factor IX gene (less than 2% of those examined). In 34 white families with at least one woman being a possible carrier, genetically, the immunoassay results were informative in 18. RFLP analyses were informative in eight of the 15 families tested. In five families each, assignment of carrier status was made to a woman by only DNA or only immunoassay results, whereas the other approach was noninformative. The immunoassays provide a rapid, inexpensive screening test and complement DNA analysis in white women who are potential carriers of hemophilia B.  相似文献   
24.

Introduction and hypothesis

Urethral diverticulum (UD) is a protrusion of the urethra through the periurethral fascia. We aimed to determine the population-based incidence of female UD.

Methods

Using the records-linkage system of the Rochester Epidemiology Project (REP), we identified women 18 years and older with a new diagnosis of UD in Olmsted County, Minnesota, USA, from 1 January 1980, through 31 December 2011. We also identified cases meeting the same criteria diagnosed at Mayo Clinic, regardless of county of residency. Incidence rates were calculated and trends for changes in incidence over time were tested. We conducted a systematic search of the MEDLINE, EMBASE, Cochrane Systematic Reviews, CENTRAL, Web of Science, and Scopus databases from inception through 30 March 2013, to identify published reports of UD incidence or prevalence.

Results

We identified 164 incidence cases, including 26 women residing in Olmsted County. Age-adjusted annual incidence of UD in Olmsted County was 17.9 per 1,000,000 women (<0.02 %) per year (95 % CI, 10.9–24.9). We observed a trend toward increased incidence during the past 3 decades (P?=?0.03). In our literature review, only 7 studies included an estimate of incidence or prevalence of UD; these estimates ranged from 6.4 per 1,000,000 per year (<0.01 %) having surgical intervention related to UD to a 4.7 % rate of UD diagnosed in asymptomatic women admitted for gynecological or obstetric issues.

Conclusions

In this population-based study, female UD was a rare disease, affecting fewer than 20 per 1,000,000 women (<0.02 %) per year.  相似文献   
25.
目的数值模拟抗血管生成因子Angiostatin和Endostatin对肿瘤血管生成的影响。方法建立肿瘤内外血管生成的二维离散数学模型。模型耦合两种抗血管生成因子Angiostatin和Endostatin的抑制效应,数值模拟在促血管生成因子诱导下肿瘤微血管网生成,讨论血管生成抑制因子的影响。结果抗血管生成因子Angiostatin对肿瘤内外血管网络生成的速度和成熟度有抑制作用。抗血管生成因子Angiostatin和Endostatin耦合作用时,在肿瘤血管生成的早期有明显的抑制效应;在肿瘤血管生成的中后期,它们可以降低肿瘤血管化程度。结论本文模型能够较好的模拟抗血管生成因子Angiostatin和Endostatin对内皮细胞迁移和增殖的抑制作用。  相似文献   
26.

Objective

To assess the safety and short-term efficacy of bilateral uterine artery ligation (UAL) via minilaparotomy for the management of heavy menstrual bleeding (HMB).

Methods

A prospective study of 30 women with HMB who underwent UAL. The primary outcome was cumulative treatment failure 12 months after the procedure. Treatment failure was defined as the need for hysterectomy during the follow-up period.

Results

At 12 months, 6 women had undergone hysterectomy for bleeding, for a cumulative failure rate of 20% (95% CI, 9%-38%). The number of bleeding days was significantly reduced by 11.9 ± 1.5 days (P < 0.001) and hemoglobin level significantly increased by 1.3 ± 0.15 g/dL (P < 0.001). Of the 30 women, 24 (80%) were satisfied with the results. No major complications were reported during the procedure or median follow-up period of 13.2 months.

Conclusion

Bilateral UAL is a safe and effective minimally invasive procedure that can provide an alternative treatment for HMB.  相似文献   
27.
28.
The aim of this study was to investigate the effect of pre-irradiation with microwaves on the induction of radioadaptive response. In the 1st phase of the study, 110 male mice were divided into 8 groups. The animals in these groups were exposed/sham-exposed to microwave, low dose rate gamma or both for 5 days. On day six, the animals were exposed to a lethal dose (LD). In the 2nd phase, 30 male rats were divided into 2 groups of 15 animals. The 1st group received microwave exposure. The 2nd group (controls) received the same LD but there was no treatment before the LD. On day 5, all animals were whole-body irradiated with the LD. Statistically significant differences between the survival rate of the mice only exposed to lethal dose of gamma radiation before irradiation with a lethal dose of gamma radiation with those of the animals pre-exposed to either microwave (p=0.02), low dose rate gamma (p=0.001) or both of these physical adapting doses (p=0.003) were observed. Likewise, a statistically significant difference between survival rates of the rats in control and test groups was observed. Altogether, these experiments showed that exposure to microwave radiation may induce a significant survival adaptive response.  相似文献   
29.
Background Pityriasis rubra pilaris (PRP) is a rare inflammatory dermatosis with frequent clinical presentation as erythroderma. Conventional systemic treatment is often unsatisfactory and limited by long‐term toxicity. The use of tumour necrosis factor (TNF) antagonists has been reported previously in single cases, but lacking long‐term follow‐up or comparison between different biological agents. Objectives To assess the long‐term efficacy and safety of TNF‐alpha antagonist, infliximab and etanercept, either in monotherapy or in combination therapy of severe, refractory adult‐onset PRP. Methods Seven patients of adult‐onset PRP, six newly diagnosed type‐I and 1 type‐II, which were resistant or ineligible to conventional systemic treatment, received a single course of infliximab or etanercept therapy, alone or in combination with low‐dose acitretin (>0.25 mg/kg/daily). After complete remission and treatment discontinuation, a follow‐up period of 12 months was evaluated for relapses. Results Six patients obtained complete remission after a single course of anti‐TNF‐alpha therapy: mean therapy duration was 19.3 weeks (range 6–48 weeks). All patients obtained significant clearing (>75% of body surface area) of skin lesions at week 12. Two patients with marked keratoderma developed localized disease recurrence during treatment. During follow‐up, only a single patient, affected by type II PRP, had disease relapse. Conclusions Both TNF‐alpha antagonists proved successful for the treatment of refractory, adult‐onset PRP, yielding complete and persistent clinical responses in type‐I PRP. Infliximab was associated with a more rapid onset of action, while treatment duration was comparable with etanercept. PRP type II warranted long‐term therapy and showed relapse after drug discontinuation.  相似文献   
30.
While tobacco smoke has been conclusively identified as a lung carcinogen, there is much debate over which smoke constituent(s) are primarily responsible for its carcinogenicity. Previous studies in our laboratory suggested that highly lipophilic carcinogens are slowly absorbed in the thicker epithelium of the conducting airways, potentially allowing for substantial local metabolism. The bioactivation of polycyclic aromatic hydrocarbons in airway epithelium may, hence, be important in tobacco smoke-induced carcinogenesis. In the present study, the hypothesis of slow absorption and substantial local metabolic activation of highly lipophilic carcinogen in airway epithelium was tested in dogs. A single dose of tritiated benzo[a]pyrene (BaP) dissolved in a saline/phospholipid suspension was instilled in the trachea, just anterior to the carina. At intervals of a few minutes up to 30 min over a 3-h period, blood samples were drawn from the azygous vein, which drains the area around the point of instillation, and from the systemic circulation. Tissue samples were taken at the end of the experiment. The concentration of BaP with depth into the tracheal mucosa was determined with autoradiography. BaP was slowly absorbed into the trachea with a half-time of approximately 73 min, which is consistent with diffusion-limited passage through the epithelium and lead to local doses in the tracheal epithelium that were more than a 1000-fold those of other tissues. The long retention of BaP in the epithelium provided the local metabolizing enzymes with high substrate levels over a long period, resulting in extensive metabolism. At 3 h after the exposure, 23% of the BaP-equivalent activity remained in the tracheal mucosa. Of this fraction, 13% was parent compound, 28% was organic extractable, 31% was water-soluble, and 28-7% of the instilled dose was bound to tracheal tissues. These results explain the tendency of highly lipophilic carcinogens, such as BaP, to induce tumors at the site of entry and, furthermore, indicate that the highly lipophilic components of tobacco smoke and polluted air may be the most important contributors to lung tumors of the conducting airways.   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