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   4607篇
  免费   398篇
  国内免费   9篇
耳鼻咽喉   57篇
儿科学   153篇
妇产科学   84篇
基础医学   693篇
口腔科学   108篇
临床医学   538篇
内科学   804篇
皮肤病学   80篇
神经病学   468篇
特种医学   94篇
外科学   716篇
综合类   42篇
一般理论   2篇
预防医学   542篇
眼科学   112篇
药学   271篇
中国医学   7篇
肿瘤学   243篇
  2023年   44篇
  2022年   72篇
  2021年   168篇
  2020年   113篇
  2019年   167篇
  2018年   168篇
  2017年   119篇
  2016年   116篇
  2015年   129篇
  2014年   191篇
  2013年   255篇
  2012年   352篇
  2011年   331篇
  2010年   173篇
  2009年   135篇
  2008年   218篇
  2007年   242篇
  2006年   214篇
  2005年   175篇
  2004年   173篇
  2003年   153篇
  2002年   152篇
  2001年   81篇
  2000年   111篇
  1999年   68篇
  1998年   39篇
  1997年   36篇
  1996年   26篇
  1995年   24篇
  1994年   16篇
  1992年   51篇
  1991年   40篇
  1990年   31篇
  1989年   40篇
  1988年   56篇
  1987年   46篇
  1986年   36篇
  1985年   46篇
  1984年   32篇
  1983年   31篇
  1982年   18篇
  1981年   20篇
  1979年   27篇
  1978年   27篇
  1977年   25篇
  1976年   22篇
  1975年   19篇
  1974年   24篇
  1973年   23篇
  1969年   16篇
排序方式: 共有5014条查询结果,搜索用时 31 毫秒
1.
We report a case of disseminated Trichosporon asahii in a patient on systemic antifungal therapy who presented with multiple cutaneous nodules suggestive of fungal infection. Histologic features resembled neutrophilic eccrine hidradenitis but staining with periodic acid‐Schiff and Gomori methenamine silver confirmed the clinical diagnosis. This case highlights the importance of maintaining suspicion for trichosporonosis and contextualizing histologic findings within the underlying clinical picture.  相似文献   
2.
3.
We provide further evidence for the two-factor structure of the 9-item Academic Expectations Stress Inventory (AESI) using confirmatory factor analysis on a sample of 289 Canadian adolescents and 310 Singaporean adolescents. Examination of measurement invariance tests the assumption that the model underlying a set of scores is directly comparable across groups. This study also examined the cross-cultural validity of the AESI using multigroup confirmatory factor analysis across both the Canadian and Singaporean adolescent samples. The results suggested cross-cultural invariance of form, factor loadings, and factor variances and covariances of the AESI across both samples. Evidence of AESI's convergent and discriminant validity was also reported. Findings from t-tests revealed that Singaporean adolescents reported a significantly higher level of academic stress arising from self expectations, other expectations, and overall academic stress, compared to Canadian adolescents. Also, a larger cross-cultural effect was associated with academic stress arising from other expectations compared with academic stress arising from self expectations.  相似文献   
4.
Background  Cardiac resynchronization therapy (CRT) is approved for the treatment of patients with advanced systolic heart failure and evidence of dyssynchrony on electrocardiograms. However, a significant percentage of patients do not demonstrate improvement with CRT. Echocardiographic techniques have been used for more accurate determination of dyssynchrony. Single photon emission computed tomography (SPECT) myocardial perfusion imaging has not previously been used to evaluate cardiac dyssynchrony. The objective of this study is to evaluate mechanical dyssynchrony as described by phase analysis of gated SPECT images in patients with left ventricular dysfunction, conduction delays, and ventricular paced rhythms. Methods and Results  A novel count-based method is used to extract regional systolic wall thickening amplitude and phase from gated SPECT images. Five indices describing the phase dispersion of the onset of mechanical contraction are determined: peak phase, phase SD, bandwidth, skewness, and kurtosis. These indices were determined in consecutive patients with left ventricular dysfunction (n=120), left bundle branch block (n=33), right bundle branch block (n=19), and ventricular paced rhythms (n=23) and were compared with normal control subjects (n=157). Phase SD, bandwidth, skewness, and kurtosis were significantly different between patients with left ventricular dysfunction, left bundle branch block, right bundle branch block, and ventricular paced rhythms and normal control subjects (all P<.001) Peak phase was significantly different between patients with right ventricular paced rhythms and normal control subjects (P=.001). Conclusions  A novel SPECT technique for describing left ventricular mechanical dyssyn-chrony has been developed and may prove useful in the evaluation of patients for CRT. This study was funded in part by a research grant from the Medtronic-Duke Strategic Alliance, of which Dr Borges-Neto is the primary investigator.  相似文献   
5.
To evaluate the utility of the polymerase chain reaction (PCR) for documenting herpes simplex virus (HSV) in persons with reactivated genital lesions viral isolation was compared with a recently developed PCR method. Three women experiencing four episodes of recurrent genital herpes were followed for 10 days per episode with daily examination and duplicate swabs of the lesions, one for HSV culture and one for PCR. HSV type 2 was cultured from three of four episodes and the mean duration of viral isolation from recurrent genital lesions was 2.6 days. PCR detected HSV DNA from lesion swabs during all four episodes, and HSV DNA was positive for an average of 6.8 days. HSV DNA was demonstrated in ulcerative lesions on 15 of 17 days versus 3 of 17 days by viral isolation (P less than .01). HSV PCR became negative when the lesions reepithelialized. These data suggest that PCR is a more sensitive measure of HSV infection than routine viral culture and that PCR detects the presence of HSV at times when culture is negative.  相似文献   
6.
Cleveland Clinic Lerner College of Medicine (CCLCM) is an innovative, five-year medical education track within Case Western Reserve University School of Medicine (Case) with a focused mission to attract and educate a limited number of highly qualified persons who seek to become physician investigators. CCLCM curriculum governance, faculty appointments and promotions, and admissions committees are integrated with respective Case committees. The CCLCM curriculum is based on faculty-defined professional attributes that graduates are expected to develop. These attributes were used to create curricular and assessment principles that guided the development of an integrated basic science, clinical science, and research curriculum, conducted in an active learning environment. An organ-system approach is used to solidify an understanding of basic science discipline threads in the context of relevant clinical problems presented in PBL and case-based discussion formats. Clinical skills are introduced in the first year as part of the two-year longitudinal experience with a family practice or internal medicine physician. The research program provides all students with opportunities to learn and experience basic and translational research and clinical research before selecting a research topic for their 12- to 15-month master-level thesis project. All Case students participate in required and elective clinical curriculum after the second year, but CCLCM students return to the Cleveland Clinic on selected Friday afternoons for program-specific research and professionalism-learning activities. A unique portfolio-based assessment system is used to assess student achievements in nine competency areas, seven of which reflect the Accreditation Council for Graduate Medical Education competencies.  相似文献   
7.
To examine the influence of diet and age on organochlorine contaminant (OC) concentrations in two closely related ringed seal (Phoca hispida) populations enantiomeric fractions (EFs) of chiral contaminants and stable isotopes of nitrogen (δ15N) and carbon (δ13C) were measured along with OCs in ringed seals collected from the east and west side of the Northwater Polynya. Seals from these two locations were feeding at the same trophic level based on δ15N values in muscle but had slightly different sources of carbon based on δ13C measurements in muscle. After removing the influence of age, sex, and blubber thickness, OC concentrations did not vary between ringed seals from the east and west side of the polynya. ΣPCB, ΣDDT, and Σchlordane were found to increase with age for both male and female seals. The inclusion of older (>20 years) female seals, which may have a reduced reproductive effort, may influence the relationships in females. Stable isotopes failed to describe OC concentrations in ringed seals suggesting that diet was not a major factor in variation of OC concentrations within this ringed seal population. Cis- and trans-chlordane, oxychlordane, and heptachlor epoxide were all nonracemic in the ringed seal blubber but did not vary with age, sex, or collection site. α-HCH appeared racemic (enantiomeric fraction = 0.50 ± 0.01) in the seals, although this EF is different than those previously observed in their prey species, and was found to vary significantly with age. EF values in the ringed seals varied considerably from other Arctic marine mammals and seabirds, providing addition evidence that the type(s) and characteristic(s) of the enzymes involved in biotransformation of chiral OCs vary between these organisms. Received: 11 April 2001/Accepted: 27 June 2001  相似文献   
8.
Median nerve somatosensory evoked potentials (SEPs) were monitored in patients with chronic pain before and after stellate ganglion blockade. A change caused by the syndrome or by the block would suggest that SEPs might be useful in the diagnosis and treatment of chronic pain. We observed 20 subjects. Group I (n = 10) had chronic pain not involving the upper extremity. Group II (n = 8) had reflex sympathetic dystrophy of the arm. All patients underwent unilateral stellate ganglion block using an anterior paratracheal approach. The SEPs were recorded by median nerve stimulation on the blocked (affected) side and unblocked (unaffected) side before and 30 min after the block. Recording sites were ipsilateral brachial plexus, the cervical spinal cord, and the contralateral sensory cortex. There were no between-group differences before or after the block. Paired analysis within each group showed that the SEPs were not different from baseline (unaffected side before block) at any time throughout the study. We conclude that since SEPs are not changed by the reflex sympathetic dystrophy or stellate ganglion block, they would not be useful in the evaluation of pain or in determining the effectiveness of sympathetic block. Both the pain and the block appear to involve alteration of conducting pathways separate from those monitored by median nerve SEPs.  相似文献   
9.
10.
A 54-year old man presented with multiple pulmonary emboli and an incidental finding of a huge left ventricular thrombus. Transthoracic echo images demonstrated a globally dilated heart with very poor left ventricular function. It was elected to manage the patient medically, and he was commenced on warfarin therapy, resulting in completed resolution of the thrombus over 10 weeks. No underlying cause was found and he did not experience any further embolic events. This illustrates a rare case of a large ventricular thrombus in a patient with no underlying risk factors.  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