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   17508篇
  免费   1065篇
  国内免费   110篇
耳鼻咽喉   95篇
儿科学   472篇
妇产科学   457篇
基础医学   2873篇
口腔科学   288篇
临床医学   1521篇
内科学   4254篇
皮肤病学   239篇
神经病学   2306篇
特种医学   376篇
外科学   1472篇
综合类   40篇
一般理论   4篇
预防医学   895篇
眼科学   147篇
药学   1357篇
中国医学   33篇
肿瘤学   1854篇
  2024年   16篇
  2023年   134篇
  2022年   318篇
  2021年   542篇
  2020年   334篇
  2019年   433篇
  2018年   484篇
  2017年   419篇
  2016年   447篇
  2015年   566篇
  2014年   703篇
  2013年   845篇
  2012年   1391篇
  2011年   1393篇
  2010年   803篇
  2009年   729篇
  2008年   1205篇
  2007年   1200篇
  2006年   1179篇
  2005年   1124篇
  2004年   1023篇
  2003年   982篇
  2002年   855篇
  2001年   110篇
  2000年   99篇
  1999年   141篇
  1998年   177篇
  1997年   129篇
  1996年   122篇
  1995年   120篇
  1994年   84篇
  1993年   82篇
  1992年   65篇
  1991年   50篇
  1990年   41篇
  1989年   53篇
  1988年   28篇
  1987年   23篇
  1986年   31篇
  1985年   23篇
  1984年   34篇
  1983年   27篇
  1982年   20篇
  1981年   19篇
  1980年   15篇
  1979年   8篇
  1978年   6篇
  1977年   9篇
  1976年   7篇
  1974年   5篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Prevalence of isolated left ventricular (LV) diastolic dysfunction has been reported to be as high as one-third of all heart failure (HF) cases, with an increasing prevalence in the elderly population. However, there is a paucity of prospective data about the prevalence and prognosis of isolated LV diastolic dysfunction in an unselected population of patients hospitalized with HF. Therefore, we prospectively evaluated 179 consecutive patients discharged from our hospital with HF to assess the prevalence of systolic versus diastolic LV dysfunction among patients hospitalized with HF and to compare their demographics, clinical features, self-perceived quality of life (QOL), and 6-month readmission rate and mortality. Among them, 133 (59% men, median age 74 years) showed in sinus rhythm and had no significant primary valvular disease. LV diastolic dysfunction was diagnosed on the basis of the European Study Group on Diastolic HF echocardiographic criteria. QOL was assessed at hospital discharge and 6-month follow-up visit using the Minnesota Living with HF questionnaire. Survival of patients with HF was compared with that of age- and sex-matched general population. In all, 29 patients (22%) had isolated LV diastolic dysfunction and 102 (78%) had prevalent LV systolic dysfunction (ie, LV ejection fraction 相似文献   
12.
Human immunodeficiency virus (HIV)-associated progressive multifocal leukoencephalopathy (PML) remains a relevant clinical problem even in the era of highly active antiretroviral therapy (HAART). Aims of the study were to analyze clinical and treatment-related features and the survival probability of PML patients observed within the Italian Registry Investigative Neuro AIDS (IRINA) during a 29-month period of HAART. Intravenous drug use, the presence of focal signs, and the involvement of white matter at neuroradiology increased the risk of having PML. A reduced probability of PML was observed when meningeal signs were reported. Patients starting HAART at PML diagnosis and previously naïve for antiretrovirals showed significantly higher 1-year probability of survival (.58), compared to those continuing HAART (.24), or never receiving HAART (.00). Higher CD4 cell count were associated with a higher survival probability (.45). At multivariate analysis, a younger age, higher CD4, starting HAART at PML diagnosis, the absence of previous acquired immunodeficiency syndrome (AIDS)-defining events, and the absence of a severe neurologic impairment were all associated with a reduced hazard of death. The use of cidofovir showed a trend towards a reduced risk of death.  相似文献   
13.
Insulin-like growth factor II (IGF-II) is a mitogen for manycell types and an important modulator of muscle growth and differentiation.IGF-II gene is prevalently expressed during prenatal developmentand its gene activity is regulated by genomic imprinting, inthat the allele inherited from the father is active and theallele inherited from the mother is inactive in most normaltissues. IGF-II expression is activated in several types ofhuman neoplasms and an alteration of IGF-II imprinting has beendescribed in Beckwith–Wiedemann syndrome and Wilms' tumour.Here we show that monoallelic expression of IGF-II gene is conservedin normal adult muscle tissue whereas two or more copies ofactive IGF-II alleles, arising by either relaxation of imprintingor duplication of the active allele, are found in 9 out of 11(82%) rhabdomyo-sarcomas retaining heterozygosity at 11p15,regardless of the histological subtype. Since IGF-II has beenindicated as an autocrine growth factor for rhabdomyosarcomacells, these findings strongly suggest that acquisition of adouble dosage of active IGF-II gene is an important step forthe initiation or progression of rhabdomyosarcoma tumorigenesis.Among different types of muscle tumors, relaxation of imprintingseems to arise prevalently in rhabdomyosarcomas, since we havedetected only one case of partial reactivation of the maternalIGF-II allele out of 7 lelomyosarcomas tested.  相似文献   
14.
There is a need for consistent definition of human immunodeficiency virus (HIV)-associated cases of progressive multifocal leukoencephalopathy (PML), especially following the profound disease changes that have resulted from the use of highly active antiretroviral therapy (HAART). According to the criteria used for diagnosis, PML cases should be either referred to as “histology-confirmed,” with evidence of JC virus (JCV) infection in brain, “laboratory-confirmed,” with detection of JCV DNA in cerebrospinal fluid (CSF), or “possible,” in the presence of typical clinical and radiological picture, but no demonstration of JCV infection. Disease outcome should be defined by the evidence or lack of evidence of disease activity, rather than using survival or other variables. Disease activity should be based on clinical (scored neurological examination), radiological (magnetic resonance imaging), and virological (JCV DNA levels in CSF) indicators, to be assessed regularly, e.g., every 3 months until evidence of disease arrest or death. Furthermore, parallel assessments of other HIV-associated manifestations, including CD4+ cell counts and viral load, are required. A standard patient classification would be helpful for clinical management of PML patients, for their inclusion in clinical studies, and also will increase our current knowledge of PML and its evolution in relation with HAART.  相似文献   
15.
The quality of health care systems and processes is becoming a prominent problem and more and more efforts are devoted to define methodologies and tools to measure and assure quality of care. New methods are required to optimize health care processes to guarantee high quality standards within (limited) available resources. Resource optimizations able to preserve the quality of treatments require good models of medical processes. This paper presents LEMMA, a new notation to model medical processes. LEMMA provides physicians with intuitive graphical elements to design their models. At the same time a high level timed Petri net corresponding to the designed model is built automatically. In this way, LEMMA models are ascribed formal semantics and can be executed and analyzed automatically. The dual language approach followed in this paper allows physicians to gain all the benefits of formal methods without being proficient in them. Medical users manage simple graphical elements, while Petri nets ensure formality and validation capabilities. In this way LEMMA mixes formal and informal notations, overcoming the problems of both the approaches. The definition of the notation has been supported by the development of an environment to design LEMMA models. The environment, besides letting us experiment with the notation, has been employed to define and analyze real case studies.  相似文献   
16.
17.
18.
The purpose of this study was to evaluate the outcome of tension-free vaginal tape (TVT) procedure in women with urodynamic stress incontinence diagnosed as having intrinsic sphincteric deficiency (ISD). The combination of a maximal urethral closure pressure <20 cm H2O and a Valsalva leak point pressure <60 cm H2O was considered as diagnostic of ISD. Subjects with detrusor overactivity on preoperative urodynamics were excluded. A total of 35 patients with both low closure pressure and leak point pressure were enrolled. Bladder perforation occurred in three (8.6%) cases. Postoperative urinary voiding difficulties occurred in nine (25.7%) women. Two patients underwent surgical detension of the tape, with complete resolution of urinary retention and no relapse of incontinence. Women with postoperative voiding dysfunction had a significantly lower detrusorial pressure at the peak flow on preoperative urodynamics compared to those who voided efficiently after TVT. The mean (range) follow-up time was 12.5 months (3–36). The objective cure rate for stress incontinence was 91.4%. Two of the three (66%) patients in whom the TVT procedure failed had a fixed urethra. De novo urge incontinence was found in five (14.3%) patients.  相似文献   
19.
AIM: A positive correlation between maternal and cord-blood IgE levels is well documented for total IgEs, but not for specific IgEs. The difficulty in detecting specific cord-blood IgEs is due to their low concentrations, which hinder their dosage by low-sensitivity methods. The study aimed to correlate maternal and foetal specific IgEs against individual cow's milk proteins, detected by highly sensitive and specific techniques. METHODS: Cow's milk specific IgE detection was performed by chemiluminescence on 52 specimens of maternal and cord blood after cow's milk protein separation by 1D and 2D gel electrophoresis. Cow's milk protein (CMP) antigens were identified by mass spectrometry techniques. RESULTS: Specific IgEs for CMPs were found in 25/52 (48.1%) of maternal sera and in 19/52 (37%) of cord-blood sera. In order of decreasing frequency, the proteins found were BSA, IgG heavy chain, caseins and, in a single case, b-lactoglobulin. Positive cord-blood sera in all cases corresponded to a positive maternal result, and maternal and foetal immunoreactivity patterns were closely correlated. Moreover, in no case was there a positive cord-blood response with a negative maternal response. CONCLUSION: The study demonstrates a close relationship between maternal and cord-blood specific IgE patterns. The phenomenon observed could provide a model to elucidate the general production method of foetal IgEs, which might only be produced in the presence of both the corresponding maternal IgE and the related allergen.  相似文献   
20.
The action of multiple liability genes is responsible for complex phenotypes at the same time, a single gene, could control several phenotypic features. This is the case of human period 3 gene (hper3), mainly involved in the setting of the biologic clock. Some variants of this gene, besides being associated with the Delayed Sleep Phase Syndrome, showed a key role in determining evening preference rather than morning one. According to this rationale, we hypothesized that this gene could influence circadian mood fluctuations, in mood disorders. Our study demonstrated that rare genetic variants of hper3 are significantly associated to a number of mood disorders features, such as age of onset, response to SSRIs treatment, circadian mood oscillations and characteristics of temperament. These preliminary results could shed further light on the involvement of circadian genes in various aspects of physiological and psychopathological mechanisms of the brain.  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