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   9134篇
  免费   539篇
  国内免费   61篇
耳鼻咽喉   100篇
儿科学   253篇
妇产科学   154篇
基础医学   1496篇
口腔科学   704篇
临床医学   622篇
内科学   1986篇
皮肤病学   235篇
神经病学   844篇
特种医学   151篇
外科学   820篇
综合类   57篇
一般理论   2篇
预防医学   888篇
眼科学   173篇
药学   682篇
中国医学   86篇
肿瘤学   481篇
  2024年   10篇
  2023年   152篇
  2022年   285篇
  2021年   450篇
  2020年   265篇
  2019年   372篇
  2018年   379篇
  2017年   252篇
  2016年   342篇
  2015年   346篇
  2014年   421篇
  2013年   516篇
  2012年   745篇
  2011年   802篇
  2010年   432篇
  2009年   330篇
  2008年   568篇
  2007年   519篇
  2006年   454篇
  2005年   455篇
  2004年   338篇
  2003年   332篇
  2002年   310篇
  2001年   83篇
  2000年   70篇
  1999年   70篇
  1998年   69篇
  1997年   35篇
  1996年   29篇
  1995年   18篇
  1994年   27篇
  1993年   17篇
  1992年   35篇
  1991年   37篇
  1990年   19篇
  1989年   10篇
  1988年   15篇
  1987年   12篇
  1986年   7篇
  1985年   9篇
  1984年   12篇
  1983年   12篇
  1982年   8篇
  1981年   8篇
  1980年   5篇
  1979年   4篇
  1978年   8篇
  1977年   4篇
  1975年   6篇
  1970年   4篇
排序方式: 共有9734条查询结果,搜索用时 15 毫秒
81.
The aim of this study was to identify at species level and to investigate the antibiotic susceptibility of oral streptococcal strains isolated from 100 pus samples collected from Romanian patients with different odontogenic infections. The isolates were identified at species level using the Rapid ID 32 STREP system and their susceptibility was testing by the Etest, against: penicillin G, ampicillin, erythromycin, clindamycin and tetracycline. For the investigation of erythromycin resistance phenotype the disk diffusion test was used. The isolates belonged to several species, with Streptococcus anginosus and Streptococcus oralis predominating. Reduced susceptibility to beta-lactam antibiotics was found only among the isolates belonging to S. mitis and S. sanguinis groups. Resistance to erythromycin was detected among all species, except for: S. constellatus, S. intermedius and S. gordonii, and the M phenotype was established, while resistance to tetracycline was detected within all species but S. gordonii. In contrast, clindamycin was fully active. As most odontogenic infections are mixed infections, often involving strictly anaerobic bacteria, which are frequently beta-lactamase producers, the association of a penicillin and a beta-lactamase inhibitor, like Amoxiclav, is recommended when the antimicrobial treatment is necessary.  相似文献   
82.
Purpose  When gamma knife radiosurgery (GKS) does not achieve control of the growth of a tumour, the need to repeat treatment is considered. The results and risks of repeat treatment of patients with a vestibular schwannoma were reviewed to assess its efficacy and safety. Methods  Between 1992 and 2001, we treated 351 patients with a vestibular schwannoma by GKS, control of the growth of the tumour was not achieved in 32. 26 patients underwntrepeat GKS and five patients had an open microsurgical operation and one stereotactic aspiration of a tumour cyst. Results  Twenty-four of 26 patients were followed up after the repeat GKS for a median of 43 months. 15 tumours became smaller, seven remained unchanged and two enlarged. After the second GKS one patient’s hearing deteriorated, one developed facial weakness and three facial spasms. One patient required insertion of ventriculo-peritoneal drainage. An operation to radically resect the tumour was performed in five patients after the first GKS and for a subtotal removal in one after repeated GKS. Conclusions  In the small proportion of patients (9%) in whom initial GKS does not control the growth of a vestibular schwannoma, most can be controlled by further GKS with a very low risk of a complications.  相似文献   
83.
7-alpha-Methyl-19-Nortestosterone (MENT) is a synthetic androgen more potent than testosterone (T) and cannot be reduced at 5-alpha position. No important effects of MENT on prostate growth have been reported. However, little is known about the effect of MENT on benign prostatic hyperplasia (BPH) or prostate carcinoma (CaP). We evaluate the effect of MENT, T and dihydrotestosterone (DHT) on secretion, proliferation and gene expression of primary cell cultures from human BPH and CaP. Moreover, the effect of these androgens was examined in the presence of finasteride to determine the influence of the 5-alpha reductase (5-AR) activity on the androgenic potency. BPH and CaP primary cultures were treated with 0, 1, 10 and 100 n m of T, MENT or DHT during 24 and 48 h. Prostate-specific antigen (PSA) was measured by micro particles immunoassay and proliferation rate by spectrophotometric assay (MTT) and by the immunochemical detection of the proliferation marker Ki-67. Gene expression of FGF8b (androgen sensitive gene) was evaluated by semi-quantitative RT-PCR. Results showed that MENT treatments increased PSA secretion and proliferation rate with a potency ranged between T and DHT. Similar effects of MENT were observed in both BPH and CaP cultures. The studies with finasteride showed that in BPH and CaP cells, the conversion of T into DHT significantly contributes to its effect on the proliferation and PSA secretion, and corroborated the resistance of MENT to the 5-AR. The effect of MENT on the gene expression of FGF8b in CaP cells was similar to T and lower than DHT. It is concluded that MENT increases proliferative and secretory activities and gene expression on pathological prostate cells although in less extent than the active metabolite DHT. Furthermore, the fall of endogenous concentration of T during MENT treatment anticipates that this androgen will be of low impact for the prostate.  相似文献   
84.
Implant migration can be accurately quantified by model‐based Roentgen stereophotogrammetric analysis (RSA), using an implant surface model to locate the implant relative to the bone. In a clinical situation, a single reverse engineering (RE) model for each implant type and size is used. It is unclear to what extent the accuracy and precision of migration measurement is affected by implant manufacturing variability unaccounted for by a single representative model. Individual RE models were generated for five short‐stem hip implants of the same type and size. Two phantom analyses and one clinical analysis were performed: “Accuracy‐matched models”: one stem was assessed, and the results from the original RE model were compared with randomly selected models. “Accuracy‐random model”: each of the five stems was assessed and analyzed using one randomly selected RE model. “Precision‐clinical setting”: implant migration was calculated for eight patients, and all five available RE models were applied to each case. For the two phantom experiments, the 95%CI of the bias ranged from ?0.28 mm to 0.30 mm for translation and ?2.3° to 2.5° for rotation. In the clinical setting, precision is less than 0.5 mm and 1.2° for translation and rotation, respectively, except for rotations about the proximodistal axis (<4.1°). High accuracy and precision of model‐based RSA can be achieved and are not biased by using a single representative RE model. At least for implants similar in shape to the investigated short‐stem, individual models are not necessary. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:903–910, 2016.
  相似文献   
85.
Alcoholic liver disease (ALD) is the second most common indication for liver transplantation (LT). The utility of fixed intervals of abstinence prior to listing is still a matter of discussion. Furthermore, post‐LT long‐term observation is challenging, and biomarkers as carbohydrate‐deficient transferrin (CDT) may help to identify alcohol relapse. We retrospectively analyzed data from patients receiving LT for ALD from 1996 to 2012. A defined period of alcohol abstinence prior to listing was not a precondition, and abstinence was evaluated using structured psychological interviews. A total of 382 patients received LT for ALD as main (n = 290) or secondary (n = 92) indication; median follow‐up was 73 months (0–213). One‐ and five‐year patient survival and graft survival rates were 82% and 69%, and 80% and 67%, respectively. A total of 62 patients (16%) experienced alcohol relapse. Alcohol relapse did not have a statistically significant effect on patient survival (P = 0.10). Post‐transplant CDT measurements showed a sensitivity and specificity of 84% and 85%, respectively. In conclusion, this large single‐center analysis showed good post‐transplant long‐term results in patients with ALD when applying structured psychological interviews before listing. Relapse rates were lower than those reported in the literature despite using a strict definition of alcohol relapse. Furthermore, post‐LT CDT measurement proved to be a useful supplementary tool for detecting alcohol relapse.  相似文献   
86.
There is increasing evidence that a variety of neoplasms including breast cancer may result from transformation of normal stem and progenitor cells. In the past, isolation and characterization of mammary stem cells has been limited by the lack of suitable culture systems able to maintain these cells in an undifferentiated state in vitro. We have recently described a culture system in which human mammary stem and progenitor cells are able to survive in suspension and produce spherical colonies composed of both stem and progenitor cells. Recent observation that adult stem cells from other tissues may also retain the capacity for growth under anchorage independent conditions suggests a common underlying mechanism. We propose that this mechanism involves the interaction between the canonical Wnt signal pathway and E-cadherin. The Wnt pathway has been implicated in normal stem cell self-renewal in vivo. Furthermore, there is evidence that deregulation of this pathway in the mammary gland and other organs may play a key role in carcinogenesis. Thus, the development of in vitro suspension culture systems not only provides an important new tool for the study of mammary cell biology, but also may have important implications for understanding key molecular pathways in both normal and neoplastic stem cells.  相似文献   
87.
The HoBi‐like pestivirus (HoBiPeV), currently classified as Pestivirus H species, is a pathogen associated with a broad spectrum of clinical manifestations in ruminants, particularly in cattle. Since HoBiPeV complete genome sequencing data is scarce, in the present study we described five nearly complete new Brazilian HoBiPeV genomes and further perform a more complete genetic and evolutionary characterization with all additional genome sequences available in the GenBank database. Entropy and selection pressure analysis showed the E2 gene, a surface glycoprotein, is the most variable gene, which also displays the greatest number of sites under positive selection. Phylogenetic and Bayesian inference based on complete genome and Npro gene, respectively, from all HoBiPeV sequences available so far, confirms the existence of three main clades (a, b, and c). The abovementioned analysis suggests that this pestivirus species probably emerged in Asia and spread to different regions including Brazil, where only strains belonging to specific genetic group ‘a’ have been found. The hypothesis of the HoBiPeV introduction in Brazil (between 1,890 and 1,962), formulated based on Bayesian inference, coincides with a period of intensive importation of water buffalo (Bubalus arnee) and indicine cattle (Bos taurus indicus) from Asia to Brazil, suggesting that this could be the origin of the current Brazilian HoBiPeV genetic group ‘a’.  相似文献   
88.
Interleukin-10 gene polymorphism in Parkinson's disease patients   总被引:3,自引:0,他引:3  
BACKGROUND: The etiology of sporadic Parkinson's disease (PD) is not well established. Recent studies revealed that inflammatory processes might also play an important role in the pathogenesis of PD. We hypothesized that genetically determined differences in the immune response, especially in anti-inflammatory cytokines production, might influence the risk of sporadic PD development and/or onset. To prove this hypothesis, two DNA polymorphisms at IL-10 promoter (-1082 and -519) were examined in sporadic PD patients. METHODS: The study enrolled 341 patients with diagnosed idiopathic PD. All cases of secondary parkinsonism were excluded from the study. For the purpose of this study the patients were also divided into two subgroups: group 1: patients with onset of Parkinson's disease, i.e., <50 years of age (early onset) included 60 patients, as well as group 2: patients with onset of Parkinson's disease >50 years of age (late onset) comprising 281 subjects. Control samples were from 315 randomly selected healthy individuals from the same geographical region who were free from signs of parkinsonism as evaluated by consultant neurologists. PCR-RFLP methods were used for genotyping. RESULTS: No statistically significant differences between PD patients and controls were found in the frequency of a single locus (-1082, -519) of IL-10 promoter. Likewise, haplotype analysis did not demonstrate any significant differences between evaluated groups. The frequency of the evaluated IL-10 genotypes was also similar in EOPD and LOPD patients. CONCLUSIONS: Results from our study revealed that the IL-10 (-1082G>A, -592C>A) polymorphism is not a risk factor of sporadic Parkinson's disease in a Polish population.  相似文献   
89.
It has been demonstrated that the decoction of the aerial parts of Tagetes lucida Cav. produces an antidepressant effect during the forced swimming test (FST) in rats. The aim of this study was to evaluate the effect of different organic extracts and one aqueous extract of the aerial parts of T. lucida on the FST. In addition, the possible involvement of the serotonergic system in the antidepressant-like effect of T. lucida in the FST was evaluated, as was its potential toxicological effect. The different extracts of T. lucida (methanol, hexane, dichloromethane and aqueous, 10 and 50 mg/kg), as well as fluoxetine (FLX, 5 mg/kg), were administered per os (p.o.) to rats for 14 days. All animals were subjected to the FST. Only the aqueous extract of T. lucida at a dose of 50 mg/kg significantly reduced immobility behavior and increased swimming in the FST, similar to FLX. Later, the aqueous extract of T. lucida (50mg/kg) was administered for 1, 7 and 14 days. An antidepressant effect was observed after 7 days of treatment. To evaluate the participation of the serotoninergic system, the animals were pretreated with PCPA, an inhibitor of serotonin synthesis (100 mg/kg/day for 4 consecutive days). The animals were treated with the aqueous extract of T. lucida (50 mg/kg) and FLX (5 mg/kg) 24 h after the final injection and were then subjected to the FST. Pretreatment with PCPA inhibited the antidepressant effect of both T. lucida and FLX. Finally, T. lucida was administered p.o. and intraperitoneal route to evaluate its acute toxicological effect. The aqueous extract of T. lucida, administered p.o., did not produce lethality or any significant changes in behavior. In conclusion, the aqueous extract of T. lucida manifested an antidepressant-like effect in the FST mediated by the serotonergic system, with no adverse effects when administered p.o.  相似文献   
90.
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