首页 | 官方网站   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   10360篇
  免费   782篇
  国内免费   37篇
医药卫生   11179篇
  2023年   73篇
  2022年   97篇
  2021年   341篇
  2020年   200篇
  2019年   324篇
  2018年   397篇
  2017年   243篇
  2016年   285篇
  2015年   267篇
  2014年   370篇
  2013年   488篇
  2012年   675篇
  2011年   776篇
  2010年   433篇
  2009年   353篇
  2008年   584篇
  2007年   583篇
  2006年   580篇
  2005年   489篇
  2004年   468篇
  2003年   455篇
  2002年   363篇
  2001年   260篇
  2000年   288篇
  1999年   249篇
  1998年   80篇
  1997年   64篇
  1996年   58篇
  1995年   55篇
  1994年   44篇
  1993年   44篇
  1992年   133篇
  1991年   136篇
  1990年   119篇
  1989年   77篇
  1988年   76篇
  1987年   55篇
  1986年   68篇
  1985年   71篇
  1984年   55篇
  1983年   35篇
  1982年   29篇
  1978年   24篇
  1976年   19篇
  1974年   20篇
  1973年   23篇
  1972年   23篇
  1971年   23篇
  1970年   26篇
  1967年   19篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
Prevalence and severity of erectile dysfunction (ED) increase with aging and are often associated with illnesses, like diabetes mellitus, heart disease, and hypertension, pathologically characterized by endothelial dysfunction and whose prevalence increases with age. The assumption that ED is mainly a neurovascular disease is supported by the evidence that specific phosphodiesterase type 5 (PDE5) inhibition produces an efficient erection in a wide range of ages and conditions. The availability of specific PDE5 inhibitors has enabled the development of effective treatment strategies, in this contest, tadalafil may be considered as the least “typical” PDE5 inhibitor. In clinical trials, tadalafil significantly enhanced, in patients of different ages, all efficacy outcomes across disease etiologies and severities. With an effectiveness lasting up to 36h, tadalafil allows patients to choose when to have sexual activities without the need to time it, showing positive feedback in terms of quality of life related to the treatment. Headache and dyspepsia were the most frequent side-effects of tadalafil, followed by back pain, nasal congestion, myalgia, and flushing, but the impact that long time action could have on effectiveness and safety is not yet entirely defined. The aim of this article is to critically review the available evidence from the tadalafil clinical research program and give the physician a rational approach for intervention in the treatment of ED and related diseases.  相似文献   
33.
A new guiding technique, Metras catheter (MC), for blindly introducing a telescoping plugged catheter (TPC) was applied to 25 mechanically ventilated patients with suspected bacterial pneumonia (BPN). Results obtained with TPC-MC were compared with those obtained with TPC using a conventional fiberoptic bronchoscope (FB) in random order. The diagnosis of BPN was definitely confirmed in 18 patients. In 7 patients, all TPC samples (MC and FB) were sterile, and a diagnosis other than BPN was proved. In the former group, colony-forming units equal to or greater than 10(3)/ml of one or more microorganisms were obtained in 61% of TPC-MC and in 66% of TPC-FB samples. These percentages increased to 64 and 71%, respectively, when 4 patients with previous antibiotic treatment were excluded from the study group. Agreement was observed between microorganisms cultured from both TPC samples in 11 of 18 patients with proved BPN (61%). Complete disparity was seen only in 2 patients (11%). Two patients developed a self-limiting hemoptysis after the TPC procedure (MC and FB, respectively). We conclude that TPC-MC is both a sensitive and specific technique for the diagnosis of BPN in mechanically ventilated patients. Because the diagnostic value of TPC-MC is similar to that of TPC-FB, we propose that the MC be used in patients receiving mechanical ventilation when the FB is not available. The simplicity and lower cost of this new system are important advantages to be considered over the fiberoptic bronchoscope.  相似文献   
34.
We assayed prostatic specific antigen and prostatic acid phosphatase serum levels in 1,383 patients using a double antibody radioimmunoassay (RIA) 125I. Establishing the upper normal limit in 10 ng/ml for prostatic specific antigen and 2.5 ng/ml for prostatic acid phosphatase, the false positive results were only 1.9 and 5.1% in men with nonprostatic benign or malignant pathology and 0 and 2.2% in women, respectively. We detected false positive levels in 3.5 and 4.7% of the patients with noncomplicated benign prostatic hypertrophy, 64.8 and 19.2% in complicated benign prostatic hypertrophy, 24 and 16% in acute prostatitis and 3.3% in chronic prostatitis for both tumoral markers. The sensibility in patients with prostate cancer was 87.2 and 64.1%, respectively, and there was better correlation with prostatic specific antigen than prostatic acid phosphatase levels on tumoral spread and histologic grading. Finally, the clinical efficacy was higher with prostatic specific antigen and it did not increase with the quantification of both tumoral markers.  相似文献   
35.
The effects of HgCl2 on the epidermis of Trichomycterus brasiliensis were studied by histological, histochemical, and ultrastructural methods. First, the normal organization of the tissue was described in order to study the HgCl2 effects on the skin structure. The epithelial cells presented a typical structural organization found in many fishes. Basically five types of cells could be detailed: goblet cells, club cells, germinative stratum cells, intermediate layer cells, and epithelial cells in the superficial layer. The goblet cells in the superficial layer present evidence of secretory activity by positive histochemical reactions. In cells exposed to HgCl2, different morphological alterations were observed in the epithelium structure, such as an increase in the lymphocyte number, hypertrophied epithelial cells at the surface, modified taste buds, obstruction of the goblet cells pore, and high cellular proliferation. Moreover, the chemical nature of the goblet cells was not modified by the presence of the HgCl2 dissolved in water. All animals died within 24 hr after the contamination with inorganic mercury at concentrations of 0.2 and 0.1 mg HgCl2/liter.  相似文献   
36.
37.
38.
OBJECTIVE: A relationship between brain atrophy and delta rhythmicity (1.5-4 Hz) has been previously explored in Alzheimer's disease (AD) subjects [Fernandez A, Arrazola J, Maestu F, Amo C, Gil-Gregorio P, Wienbruch C, Ortiz T. Correlations of hippocampal atrophy and focal low-frequency magnetic activity in Alzheimer disease: volumetric MR imaging-magnetoencephalographic study. Am J Neuroradiol. 2003 24(3):481-487]. In this study, we tested the hypothesis that such a relationship does exist not only in AD patients but also across the continuum of subjects with mild cognitive impairment (MCI) and AD. METHODS: Resting, eyes-closed EEG data were recorded in 34 MCI and 65 AD subjects. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). EEG cortical sources were estimated by LORETA. Cortical EEG sources were correlated with MR-based measurements of lobar brain volume (white and gray matter). RESULTS: A negative correlation was observed between the frontal white matter and the amplitude of frontal delta sources (2-4 Hz) across MCI and AD subjects. CONCLUSIONS: These results confirmed for the first time the hypothesis that the sources of resting delta rhythms (2-4 Hz) are correlated with lobar brain volume across MCI and AD subjects. SIGNIFICANCE: The present findings support, at least at group level, the 'transition hypothesis' of brain structural and functional continuity between MCI and AD.  相似文献   
39.
The effect of administration of diazepam on successive negative contrast in one-way avoidance learning was examined in rats. Contrast was induced by shifting rats from a large reward, 30 s spent in the safe compartment, to a small reward, 1 s spent in the safe compartment. IP administration of 2 mg/kg diazepam eliminated this negative contrast. Moreover, this effect is dose dependent, with doses of 2 and 2.5 mg/kg, but not 0.5 mg/kg, effective in reliably reducing contrast. These results suggest the existence of similar or common underlying mechanisms in both aversive and appetitive contrast effects; they are discussed in light of the current theories of frustrative nonreward and as a mean of studying the behavioral and biological mechanisms of anxiety.  相似文献   
40.
Gongylonema neoplasticum was identified in the oesophagus of 14 wild rabbits (Oryctolagus cuniculus) from Portugal. This is the first record of Gongylonema neoplasticum in a naturally infected lagomorph species in Europe. This paper presents the most relevant measurements of adult worms and some of their surface features seen by scanning electron microscopy. Epidemiological aspects of G. neoplasticum such as geographical distribution, host spectrum and biological features are discussed.  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-23

京公网安备 11010802026262号