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   1395篇
  免费   48篇
  国内免费   19篇
耳鼻咽喉   4篇
儿科学   43篇
妇产科学   16篇
基础医学   210篇
口腔科学   34篇
临床医学   109篇
内科学   234篇
皮肤病学   10篇
神经病学   97篇
特种医学   173篇
外科学   215篇
综合类   16篇
一般理论   1篇
预防医学   75篇
眼科学   13篇
药学   124篇
中国医学   5篇
肿瘤学   83篇
  2023年   7篇
  2022年   32篇
  2021年   36篇
  2020年   16篇
  2019年   24篇
  2018年   26篇
  2017年   24篇
  2016年   27篇
  2015年   33篇
  2014年   42篇
  2013年   71篇
  2012年   127篇
  2011年   161篇
  2010年   56篇
  2009年   45篇
  2008年   98篇
  2007年   129篇
  2006年   89篇
  2005年   81篇
  2004年   74篇
  2003年   71篇
  2002年   47篇
  2001年   17篇
  2000年   10篇
  1999年   11篇
  1998年   16篇
  1997年   8篇
  1996年   6篇
  1995年   7篇
  1994年   8篇
  1993年   9篇
  1992年   5篇
  1991年   4篇
  1990年   5篇
  1987年   4篇
  1986年   4篇
  1985年   3篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1977年   1篇
  1976年   3篇
  1974年   5篇
  1973年   4篇
  1972年   2篇
  1971年   2篇
  1969年   2篇
  1968年   1篇
排序方式: 共有1462条查询结果,搜索用时 31 毫秒
1.
Objective: To analyse the incidence, clinical presentation, and outcome of heart insufficiency in patients with chronic arteriovenous fistulas (AVF). Methodology: From 1991 to 2000 we treated 49 patients with traumatic AVF. The present study included 19 patients with AVF present for 6 months or longer, as it was presumed that these AVF will have an impact on cardiac overload. There were 16 male and three female patients with a mean age of 36 years (17–59). The time from injury to admission varied from 6 months to 33 years. Cardiological examination checked for dyspnoea and palpitation. ECG, chest X‐ray and ECHO‐cardiography were also performed. All AVF were deleted, magistral vessels reconstructed, non‐magistral obliterated, either surgically or by percutaneous embolization. Results: Mean follow up was 44.2 months (3–93). Serious heart insufficiency was seen in two patients only, with AVF in the subclavial vessels. Both suffered from serious heart disease prior to the therapeutic procedures that resulted in iatrogenic AVF, so it was difficult to connect heart insufficiency to the AVF alone. Despite surgical closure of AVF and intensive medical treatment, signs of heart insufficiency remained in both patients. Signs of cardiac overload were seen in six patients with long‐standing AVF in major vessels. Except for one patient who refused surgical closure of femoral AVF, the remaining five were symptom free for cardiac overload during the follow‐up period. Conclusion: In our series, heart insufficiency was an infrequent complication in long‐standing AVF, even when major vessels were involved.  相似文献   
2.
AIM: To review the clinical experience of children and teens diagnosed with Type 2 diabetes (T2DM) at a paediatric hospital serving a large urban multi-ethnic population. METHODS: Retrospective chart review of patients with T2DM followed in the diabetes clinic at the Hospital for Sick Children (HSC) over an 8-year period. Patients who were included were younger than 18, referred at the onset of diabetes, and where presentation and/or clinical course was 'typical' of T2DM. RESULTS: Of 1020 children with diabetes followed at HSC, 4% were identified as having T2DM in 2002. There was a sixfold increase in new cases from 1994 to 2002. The mean age at diagnosis was 13.5 +/- 2.2 years (range 8.8-17.5) with a female-to-male ratio of 1.7. Most had a first- or second-degree relative with T2DM. There was an overrepresentation of children with T2DM from Asian and African Canadian ethnic groups relative to the regional population. The majority of teens were asymptomatic at presentation, with a smaller number in diabetic ketoacidosis (DKA) at diagnosis. Mean HbA1c at diagnosis was 10 +/- 3.4%. Approximately one half of patients were initially treated by diet and exercise with many requiring intensification of therapy over a short period of time. CONCLUSIONS: We report a similar increase in T2DM incidence and clinical presentation at HSC to other clinic reports in large North American urban centres. Of note is the high prevalence of children of South/South-East Asian descent.  相似文献   
3.
Several recent studies have suggested that thought leaders in radical prostatectomy have decreased their own positive margin rates by switching from open to robot-assisted radical prostatectomy. Theoretically, this improvement is largely attributed to enhanced visualization of the deep pelvis and precision of dissection afforded by the instrumentation. To date, it has not been determined if this phenomenon exists amongst non-fellowship-trained urologists in private practice. Herein, we describe the positive margin rates of two non-fellowship-trained private-practice urologists who converted from open radical retropubic prostatectomy to robot-assisted radical prostatectomy. The margin positivity data from two non-fellowship-trained private-practice urologists (surgeon 1 and surgeon 2) were reviewed retrospectively. The last 50 cases of open radical retropubic prostatectomy from each surgeon were compared with the first 50 robotic prostatectomy cases of surgeons 1 and 2, respectively. A positive surgical margin was defined as tumor present at the inked margin of the prostate. There was a significant decrease in the overall and pT2 positive margin rates for both surgeons. The overall positive margin rate and pT2 positive margin rate for surgeon 1 dropped from 44 to 20% and from 37 to 5.7%, respectively, after changing from open to robotic prostatectomy. For surgeon 2, the overall positive margin rate changed from 26 to 18% and the pT2 positive margin rate changed from 27.5 to 7% after converting. Changing from open to robotic-assisted radical prostatectomy may improve the ability of urologists to obtain negative surgical margins. With proper training this phenomenon does seem to apply to non-fellowship-trained urologists in private practice and can be realized within the first 50 cases performed.  相似文献   
4.
Reducing the workload of the beta cell by inhibiting insulin secretion may provide beneficial effects for patients with type 2 diabetes. The aim of this study was to investigate the effect of NN414, a beta cell selective potassium channel opener in patients with type 2 diabetes. 24 patients were treated for seven days (placebo, 1.5, 4.5, and 10 mg/kg). In accordance with the pharmacological profile a significant and selective inhibition of insulin secretion was observed (1 h post dose). There were no statistically significant effects on overall glycaemic control. Based on OGTT derived parameters a borderline significant improvement in beta-cell function (1st and 2nd phase insulin secretion) was observed from Day 1 to Day 7.  相似文献   
5.
We report a case of mucous gland adenoma arising in the left main bronchus which was initially misdiagnosed as asthma and review the previous reported cases of this rare tumor published in the available literature.  相似文献   
6.
In a recent study we described an increase of elastic tissue fibres in blood vessel walls of placental stem villi during pre-eclampsia when compared to uncomplicated pregnancies. Furthermore, the thickness of these blood vessel walls was enhanced in pre-eclampsia. Since it is known that elastic tissue fibres increase in systemic hypertension, it may be assumed that the enhancement of elastic tissue fibres in placental stem villi during pre-eclampsia may be induced by the hypertension. To get further insight into this assumption, we examined the amount of elastic tissue fibres in stem villus blood vessels of placentae of pregnancies complicated by intrauterine growth retardation (isolated IUGR, fourteen cases), a disease without hypertension of the mother and such with pre-eclampsia and concomitant IUGR (IUGR+PE, nine cases). Each study group was compared with uncomplicated pregnancies (twenty-six cases). Unfixed cryostat serial sections were processed for conventional orcein staining and for the demonstration of alpha-actin-immunoreactivity. The intensity of orcein staining of stem villus blood vessel walls was evaluated by a semiquantitative score method. Significant lower intensities of orcein staining were calculated for blood vessel walls of placentae of isolated IUGR (P=0.0007) and IUGR+PE (P=0.0039) when compared to uncomplicated pregnancies each. Additionally, the blood vessel wall thickness of stem villi of isolated IUGR (P=0.0081) and IUGR+PE (P=0.0007) was significantly reduced. In comparison to the above mentioned investigation, our results show that, in contrast to isolated pre-eclampsia, elastic tissue fibres are decreased during pregnancies complicated by IUGR, independently of the occurrence of concomitant pre-eclampsia when compared to uncomplicated pregnancies. From our studies it may be considered that the increase of elastic tissue fibres in placentae of patients with isolated pre-eclampsia may be induced by systemic hypertension. Furthermore, our study underline arguments that IUGR may be an independent disease of the fetus.  相似文献   
7.
The complex-formation reactions of the platinum(II) complexes, [Pt(dien)H2O]2+, [PtCl(dien)]+ and [PtBr(dien)]+ (dien is diethylenetriamine) with some biologically relevant ligands such as inosine (INO), inosine-5'-monophosphate (5'-IMP), guanosine-5'-monophosphate (5'-GMP), glutathione (GSH) and L-methionine (S-meth), were studied by UV-Vis (UV-Visible) spectrophotometry and 1H NMR spectroscopy. Reactions of the [PtCl(dien)]+ with L-methionine were studied in the presence and absence of 5'-GMP. The rate constants clearly showed a kinetic preference toward L-methionine. However, competitive reactions of [PtCl(dien)]+ with L-methionine and 5'-GMP demonstrated initially rapid formation of [Pt(dien)(S-meth)]2+ followed by displacement of L-methionine by 5'-GMP. In the later stages the concentration of [Pt(dien)(N7-GMP )]2+ is predominant. The results are analyzed in reference to the anti-tumour activity of Pt(II) complexes.  相似文献   
8.
9.
The human cytotrophoblasts are the first fetal cells to arise during embryogenesis and are the progenitor cells to villous (noninvasive), syncytiotrophoblast (noninvasive), "intermediate" extravillous (invasive), and "anchoring" extravillous (invasive) trophoblast subpopulations. These trophoblast subpopulations were isolated from first- and third-trimester placentae and were stimulated with Sendai virus, granulocyte-macrophage colony-stimulating factors (GM-CSF), and platelet-derived growth factor (PDGF) to produce interferons (IFNs). GM-CSF and PDGF induced very low levels of IFN in first-trimester extravillous and villous trophoblast subpopulations. Highly proliferating and invasive intermediate extravillous trophoblast cultures produced five- to eightfold more IFNs than villous trophoblast cultures and two- to fivefold more IFN than the syncytiotrophoblast cultures when stimulated with Sendai virus. Syncytiotrophoblast cultures produced higher levels of IFNs (up to twofold) than villous trophoblast cultures when stimulated with the same virus. Pretreatment of first-trimester extravillous and villous trophoblast cultures with GM-CSF and PDGF followed by infection with Sendai virus resulted in greater IFN production than when the cultures were stimulated with virus alone. The levels of IFN produced were dependent on the type of trophoblast, the type of inducer, and the stage of differentiation of the trophoblasts. The purified trophoblast IFNs have potent antiviral activities when assayed on human amniotic WISH cells, and they inhibited proliferation of normal trophoblasts and trophoblast-derived malignant cells in vitro without any toxicity. Furthermore, the trophoblast IFNs activated NK cell activity and suppressed mitogen-stimulated lymphocyte proliferation at concentrations of between 10 and 1,000 IU/ml. The possible functions of the trophoblast IFNs during pregnancy are discussed with respect to human placental and fetal protection and development.  相似文献   
10.
The main biologically active components of plants belonging to the genus Allium, responsible for their biological activities, including anti-inflammatory, antioxidant and immunomodulatory, are organosulfur compounds. The aim of this study was to synthetize the mixture of dipropyl polysulfides (DPPS) and to test their biological activity in acute hepatitis. C57BL/6 mice were administered orally with DPPS 6 h before intravenous injection of Concanavalin A (ConA). Liver inflammation, necrosis and hepatocytes apoptosis were determined by histological analyses. Cytokines in liver tissue were determined by ELISA, expression of adhesive molecules and enzymes by RT PCR, while liver mononuclear cells were analyzed by flow cytometry. DPPS pretreatment significantly attenuated liver inflammation and injury, as evidenced by biochemical and histopathological observations. In DPPS-pretreated mice, messenger RNA levels of adhesion molecules and NADPH oxidase complex were significantly reduced, while the expression of SOD enzymes was enhanced. DPPS pretreatment decreased protein level of inflammatory cytokines and increased percentage of T regulatory cells in the livers of ConA mice. DPPS showed hepatoprotective effects in ConA-induced hepatitis, characterized by attenuation of inflammation and affection of Th17/Treg balance in favor of T regulatory cells and implicating potential therapeutic usage of DPPS mixture in inflammatory liver diseases.  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