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   5423篇
  免费   324篇
  国内免费   30篇
耳鼻咽喉   49篇
儿科学   113篇
妇产科学   142篇
基础医学   749篇
口腔科学   92篇
临床医学   424篇
内科学   1191篇
皮肤病学   119篇
神经病学   636篇
特种医学   99篇
外科学   498篇
综合类   9篇
一般理论   1篇
预防医学   409篇
眼科学   68篇
药学   453篇
中国医学   17篇
肿瘤学   708篇
  2024年   7篇
  2023年   40篇
  2022年   50篇
  2021年   183篇
  2020年   122篇
  2019年   144篇
  2018年   153篇
  2017年   132篇
  2016年   139篇
  2015年   172篇
  2014年   209篇
  2013年   263篇
  2012年   468篇
  2011年   391篇
  2010年   222篇
  2009年   199篇
  2008年   337篇
  2007年   357篇
  2006年   365篇
  2005年   365篇
  2004年   338篇
  2003年   305篇
  2002年   261篇
  2001年   39篇
  2000年   32篇
  1999年   42篇
  1998年   53篇
  1997年   35篇
  1996年   48篇
  1995年   40篇
  1994年   27篇
  1993年   26篇
  1992年   20篇
  1991年   23篇
  1990年   9篇
  1989年   15篇
  1988年   15篇
  1987年   12篇
  1986年   12篇
  1985年   13篇
  1984年   11篇
  1983年   14篇
  1982年   6篇
  1981年   10篇
  1980年   6篇
  1979年   9篇
  1978年   11篇
  1976年   5篇
  1974年   5篇
  1965年   3篇
排序方式: 共有5777条查询结果,搜索用时 15 毫秒
11.
Summary:  Purpose: Psychogenic nonepileptic seizures (PNES) are episodes that may resemble epileptic seizures (ES) but are not associated with abnormal electrical discharges in the brain. Video-EEG recording of a typical episode is considered the best diagnostic tool available. PNES are, however, also documented in patients with epilepsy (PNES/ES). The purpose of this study was to assess this comorbid population, focusing on the differences between patients with PNES/ES and patients with PNES alone.
Methods: We reviewed 110 PNES episodes, occurring spontaneously or induced by means of suggestion techniques, recorded in our video-EEG laboratory over a period of eight years. We identified two subgroups of patients, consisting of 85 PNES cases and 25 PNES/ES cases, and assessed any differences in their characteristics by reviewing a number of variables (age, sex, clinical features, antiepileptic therapy, age of onset, time to diagnosis, pathological history, and length of follow-up).
Results: The comparison between the two subgroups revealed that PNES/ES patients displayed some statistically significant differences when compared with PNES alone patients, i.e., younger age, a higher percentage of spontaneously activated events, a shorter disease duration, a longer time to PNES diagnosis, and a lower percentage lost at follow-up.
Conclusions: This study confirms that PNES is a common, though probably underestimated, occurrence in epilepsy services. Our results shed light on some different characteristics between PNES and PNES/ES patients.  相似文献   
12.
13.
Objective: Severe atherosclerosis of the ascending aorta and arch frequently causes difficulties during heart operations, hindering surgical manoeuvres and potentially leading to systemic embolism. The aim of our study was to assess the safety and effectiveness of replacing the atherosclerotic ascending aorta in this setting. Methods: Aortic atherosclerosis was characterized by epiaortic ultrasonographic scanning in 90.1% of 1927 consecutive adult patients undergoing cardiac operations, and by computed tomographic chest scanning in selected cases. Thirty-six of the 152 patients requiring major derangements from our standard practice due to aortic atherosclerosis underwent replacement of the ascending aorta and constitute the study group. Replacement of the aorta was extended to the arch in 13 cases (36.1%). It was associated with single or multiple valve surgery in 34 patients (94.4%) and with coronary revascularization in 30 (83.3%). Two patients (5.6%) underwent coronary bypass grafting without valve surgery. A cryoablation procedure was associated in three patients with permanent atrial fibrillation. Deep hypothermic circulatory arrest was employed in 34 patients (94.4%), while proximal aortic disease allowed conventional distal crossclamping in 2 cases. The risk of operative mortality was estimated by the logistic EuroSCORE both with and withholding the variable ‘surgery of the thoracic aorta’. All survivors were followed-up for 1–41 months (16 ± 12). Results: Two patients died in the hospital (5.6%) and two during follow-up, for a cumulative survival of 91.3% and 85.6% at 1 and 3 years, respectively (hospital deaths included). The hospital death rate compared favourably with the expected estimates of 25.5% (p < 0.05) and 10.3% (p = 0.67) obtained by the EuroSCORE full model and without ‘aortic surgery’, respectively. In-hospital adverse neurologic events occurred in six patients (16.7%), including stroke in one patient (2.8%) and neurocognitive disturbances in five (13.9%), although they were all transient and cleared before discharge. Excess bleeding required re-exploration in four patients (11.1%), and one more patient underwent emergency grafting for acute postoperative coronary occlusion. Ten patients (38.5%) were intubated for longer than 24 h. Conclusion: Despite significant perioperative morbidity, replacement of the severely atherosclerotic aorta is worth consideration to avert expectedly higher death and stroke rates.  相似文献   
14.
15.
OBJECTIVE: Our purpose was to investigate immunosuppressive acidic protein in the prognostic characterization of advanced ovarian cancer. STUDY DESIGN: Serum levels of immunosuppressive protein were prospectively measured in 80 patients with untreated ovarian carcinoma. To evaluate the prognostic significance of immunosuppressive acidic protein levels, cutoff points were studied every 50 μg/ml between 450 and 1350 μg/ml. RESULTS: Pretreatment immunosuppressive acidic protein levels were not significantly associated with stage, histotype, grade of differentiation, postoperative residual tumor, and response to chemotherapy. The most significant association with survival was observed at a cutoff value of 1100 μg/ml (p = 0.0089). In the univariate analysis for overall survival, International Federation of Gynecology and Obstetrics stage and immunosuppressive acidic protein status were found to have a role in predicting ovarian cancer prognosis. In the multivariate analysis only immunosuppressive acidic protein status was significantly associated with survival. A statistical correlation was found between serum levels and overall survival (p = 0.0104, χ2 6.56), including immunosuppressive acidic protein as a continuous variable. CONCLUSION: Our data suggest that immunosuppressive acidic protein assay is a potentially useful tool in the prognostic characterization of advanced ovarian cancer. (Am J Obstet Gynecol 1996;175:1606-10.)  相似文献   
16.
Molecular cytogenetic characterization of proximal-type epithelioid sarcoma   总被引:2,自引:0,他引:2  
Proximal-type epithelioid sarcoma is a recently described soft-tissue tumor that is distinguished from conventional-type epithelioid sarcoma by a far more aggressive clinical course, frequent location in the proximal anatomic regions, and variable rhabdoid morphology. Because of their rarity and peculiar morphology, proximal-type epithelioid sarcomas frequently pose serious diagnostic dilemmas, being easily misdiagnosed as a variety of other malignant neoplasms. To date, the information available on the genetic alterations associated with this tumor entity has been confined to single conventional cytogenetic reports. In this article, we present the results of a conventional and molecular cytogenetic analysis of six proximal-type epithelioid sarcomas. Spectral karyotyping analysis of these cases deciphered the characteristics of several marker chromosomes and complex translocations, leading to the recognition of recurrent rearrangements. The most frequently involved chromosome arm was 22q, and the identification of two cases with a similar translocation, t(10;22), suggests a role for one or more genes on chromosome 22 in the pathogenesis of this tumor and provides an opportunity for finely mapping the translocation-associated breakpoints. Chromosome arm 8q gain was also a frequent event and correlated with gain of MYC gene copy number, as demonstrated by fluorescence in situ hybridization. A review of both cases reported in the literature and those presented in this study reinforced the involvement of chromosomes 8 and 22 and also indicated frequent rearrangements of chromosomes 7, 14, 18, and 20.  相似文献   
17.
18.
A properly engineered biomaterial for dental/orthopaedic applications must induce specific responses from the osteoblasts at the implant site. A most desirable response is an efficient adhesion, as it represents the first phase in the cell/material interaction and the quality of this phase will influence the cell's capacity to organize into a new functional tissue. The four osteoblast-adhesive peptides discussed in this paper are mapped on the 339-364 sequence (339MAPRPSLAKKQRFRHRNRKGYRSQRG364) located in the primary heparin-binding site of human vitronectin (HVP). Adsorbed on a polystyrene scaffold, these peptides display different adhesive activities towards osteoblasts. In this paper we report on the structural analysis in solution of the peptides through NMR and computational techniques. We find that the peptides with the highest adhesive activities display a hydrophobic patch opposite to the charged surface candidate to interact with heparin. These findings suggest that the peptides might adsorb on the polystyrene support in a favourable orientation for their activity. Furthermore, molecular models obtained for the four peptides in solution were used in rigid docking simulations with a heparin model. Assuming that the peptide solution conformations are not very different from the polystyrene-adsorbed structures, the simulations reveal that peptide adhesive activity is also affected by the number of ionic interactions and spacing between charged residues.  相似文献   
19.
Hereditary hearing loss (HHL) is one of the most common congenital disorders and is highly heterogeneous. Mutations in the connexin 26 (CX26) gene (GJB2) account for about 20% of all cases of childhood deafness, and approach 50% in documented recessive cases of non-syndromic hearing loss. In addition, a single mitochondrial DNA mutation, mt1555A>G, in the 12S rRNA gene (MTRNR1), is associated with familial cases of progressive deafness. Effective screening of populations for HHL necessitates rapid assessment of several of these potential mutation sites. Pyrosequencing links a DNA synthesis protocol for determining sequence to an enzyme cascade that generates light whenever pyrophosphate is released during primer strand elongation. We assessed the ability of Pyrosequencing to detect common mutations causing HHL. Detection of the most common CX26 mutations in individuals of Caucasian (35delG), Ashkenazi (167delT), and Asian (235delC, V37I) descent was confirmed by Pyrosequencing. A total of 41 different mutations in the CX26 gene and the mitochondrial mt1555A>G mutation were confirmed. Genotyping of up to six different adjacent mutations was achieved, including simultaneous detection of 35delG and 167delT. Accurate and reproducible results were achieved taking advantage of assay flexibility and experimental conditions easily optimized for a high degree of standardization and cost-effectiveness. The standardized sample preparation steps, including target amplification by PCR and preparation of single-stranded template combined with automated sequence reaction and automated genotype scoring, positions this approach as a potentially high throughput platform for SNP/mutation genotyping in a clinical laboratory setting. .  相似文献   
20.
It is well known that migraine has a strong genetic component, although the type and number of genes involved is not yet clear. There is evidence to suggest that serotonin-related genes participate in the pathogenesis of migraine. Previous studies have shown that gender differences influence the serotonergic neurotransmission and, in addition, the migraine prevalence is higher in females than males. Therefore, we investigated the functional polymorphism in the upstream regulatory region of the serotonin transporter gene (5-HTTLPR) and the 102T/C polymorphism of the 5-HT2A receptor gene in the Hungarian female population. These genes were analysed in 126 migraine sufferers (with or without aura)and 101 unrelated healthy controls using case control design. A borderline association (chi2 = 3.84, df = 1, p = 0.049; OR = 1.45, 95% CI = 1.00-2.12) between 5-HTTLPR short (S) allele and migraine was found. No significant difference between migraine sufferers and controls was observed for the 102T/C polymorphism of 5-HT2A receptor gene. Furthermore, there was no significant interaction between5-HTTLPR and 102T/C polymorphisms in our study population. In conclusion, our results support that the genetic susceptibility of migraine may be associated with a locus at or near the 5-HT transporter gene.  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