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   2215篇
  免费   128篇
  国内免费   23篇
耳鼻咽喉   9篇
儿科学   53篇
妇产科学   23篇
基础医学   161篇
口腔科学   75篇
临床医学   180篇
内科学   456篇
皮肤病学   232篇
神经病学   78篇
特种医学   224篇
外科学   158篇
综合类   20篇
一般理论   1篇
预防医学   150篇
眼科学   422篇
药学   74篇
肿瘤学   50篇
  2021年   19篇
  2019年   14篇
  2018年   15篇
  2017年   21篇
  2016年   54篇
  2015年   47篇
  2014年   58篇
  2013年   99篇
  2012年   60篇
  2011年   68篇
  2010年   58篇
  2009年   84篇
  2008年   76篇
  2007年   86篇
  2006年   66篇
  2005年   49篇
  2004年   50篇
  2003年   43篇
  2002年   51篇
  2001年   44篇
  2000年   53篇
  1999年   62篇
  1998年   75篇
  1997年   64篇
  1996年   68篇
  1995年   58篇
  1994年   65篇
  1993年   42篇
  1992年   69篇
  1991年   40篇
  1990年   62篇
  1989年   59篇
  1988年   71篇
  1987年   46篇
  1986年   58篇
  1985年   34篇
  1984年   46篇
  1983年   27篇
  1982年   22篇
  1981年   24篇
  1980年   19篇
  1978年   14篇
  1977年   11篇
  1976年   17篇
  1975年   10篇
  1973年   11篇
  1972年   10篇
  1971年   12篇
  1966年   9篇
  1964年   14篇
排序方式: 共有2366条查询结果,搜索用时 15 毫秒
91.
Adenosquamous carcinomas of the head and neck (ADSCs) are rare locally aggressive malignancies characterized by the presence of two distinctive components, a squamous cell carcinoma and an adenocarcinoma. The immunophenotype of the glandular component of ADSCs has only been rarely studied but has been reported as being positive for keratin 7 (CK7) and carcinoembryonic antigen (CEA) and negative for keratin 20 (CK20). Herein, we report a case of an ADSCs of the hypopharynx composed of a superficial squamous cell carcinoma and an adenocarcinoma with an intestinal phenotype. The patient was a 62 year-old male with a T2 N0 M0 squamous cell carcinoma (SCC) of uvula and palate and a T1 N0 M0 of right hypopharynx. The ADSCs of the hypopharynx was composed of a minimally invasive SCC and an adenocarcinoma with tubulo-glandular and cribriform architecture. The neoplastic glands were positive for CK7, CK20, CDX2, CEA and Villin. The patient underwent radiotherapy to both tumors and remains well with no evidence of recurrent disease 19 months after treatment. To the best of our knowledge, this is the first report of an ADSCs of the head and neck with an intestinal phenotype in its glandular component.  相似文献   
92.
93.
A large-scale review of the literature concerning the effects of noise on hearing, published primarily during the 1970s, was initiated by the National Institute of Neurological and Communicative Disorders and Stroke in 1981. This review demonstrated a continuing search for medicinal treatment for the adverse effects of noise on hearing. The present article focuses on the results of investigations of human subjects. The literature in this area is primarily European and deals principally with treatment of acoustic trauma, although a few reports have described attempts to render the ear less susceptible to the hazards of chronic noise exposure. Much of the published information is of questionable value because of inadequate experimental design and control. To date, the search for effective medicinal treatment for hearing loss caused by noise has been unsuccessful. Results reported from studies of the effects of carbogen are encouraging and suggest that continued rigorous investigation of this agent is warranted.  相似文献   
94.
Laryngeal aerodynamics associated with selected voice disorders   总被引:1,自引:0,他引:1  
Measures of estimated subglottal air pressure and laryngeal air flow during speech production are compared for adults with normal laryngeal function and those with laryngeal abnormalities. The most traditional measure, air flow during sustained vowel production, is not a strong predictor of laryngeal function during speech production. Subglottal air pressure and laryngeal air flow offer insight into voice disorders and provide directions for therapy as well as a method for the quantitative assessment of treatment outcomes.  相似文献   
95.
96.
PURPOSE: Corneal polarization axis (CPA) has been reported to affect retardation measurements obtained with scanning laser polarimetry (SLP). The purpose of this investigation was to prospectively determine whether correction for CPA improves the discriminating power of SLP for detection of mild-to-moderate glaucoma. DESIGN: Cross-sectional analysis of normal and glaucomatous eyes. METHODS: We constructed a noninvasive slit-lamp-mounted device incorporating two crossed linear polarizers and an optical retarder to measure the slow axis of corneal polarization. Complete ocular examination, standard automated perimetry, SLP imaging, and CPA measurements were performed on normal and glaucomatous eyes. One eye/subject was enrolled; if both eyes of a patient were eligible for the study, the right eye was selected. For each of the 13 SLP parameters, logistic regression was used to determine if including CPA in the model influenced the ability to discriminate between normal and glaucomatous eyes. RESULTS: Forty-three normal eyes (average visual field mean defect, -0.53 +/- 1.4 dB) and 33 glaucomatous eyes (average visual field mean defect, -5.93 +/- 6.5 dB) were enrolled. CPA was significantly correlated with summary retardation parameters (average thickness and integral values) in normal (r = 0.72-0.83, P <.001 for all values) and glaucomatous eyes (r = 0.43-0.62, P =.013 to <.001). Including CPA in the model improved the ability to discriminate between normal and glaucomatous eyes for five retardation parameters quantifying retinal nerve fiber layer (RNFL) thickness (range of P values: 0.045-0.001). For inferior average thickness, area under the receiver operating characteristic (ROC) curve increased significantly (P =.002) from 0.70 to 0.78 after accounting for CPA; with a sensitivity set at 80% specificity improved from 33% to 72%. Correlations between visual field corrected pattern standard deviation and average thickness, ellipse average, superior average, and inferior average significantly increased (range of P values,.018-.001) after adjustment for CPA (r = -0.35 and -0.45, -0.38 and -0.47, -0.46 and -0.57, and -0.42 and -0.49, respectively). CONCLUSIONS: Correction for CPA significantly increases the correlation between retinal nerve fiber layer structural damage and visual function and significantly improves the discriminating power of SLP for detection of mild-to-moderate glaucoma.  相似文献   
97.
98.
PURPOSE: To compare the ability of several machine learning classifiers to predict development of abnormal fields at follow-up in ocular hypertensive (OHT) eyes that had normal visual fields in baseline examination. METHODS: The visual fields of 114 eyes of 114 patients with OHT with four or more visual field tests with standard automated perimetry over three or more years and for whom stereophotographs were available were assessed. The mean (+/-SD) number of visual field tests was 7.89 +/- 3.04. The mean number of years covered (+/-SD) was 5.92 +/- 2.34 (range, 2.81-11.77). Fields were classified as normal or abnormal based on Statpac-like methods (Humphrey Instruments, Dublin, CA) and by several machine learning classifiers. The machine learning classifiers were two types of support vector machine (SVM), a mixture of Gaussian (MoG) classifier, a constrained MoG, and a mixture of generalized Gaussian (MGG). Specificity was set to 96% for all classifiers, using data from 94 normal eyes evaluated longitudinally. Specificity cutoffs required confirmation of abnormality. RESULTS: Thirty-two percent (36/114) of the eyes converted to abnormal fields during follow-up based on the Statpac-like methods. All 36 were identified by at least one machine classifier. In nearly all cases, the machine learning classifiers predicted the confirmed abnormality, on average, 3.92 +/- 0.55 years earlier than traditional Statpac-like methods. CONCLUSIONS: Machine learning classifiers can learn complex patterns and trends in data and adapt to create a decision surface without the constraints imposed by statistical classifiers. This adaptation allowed the machine learning classifiers to identify abnormality in visual field converts much earlier than the traditional methods.  相似文献   
99.
The objectives of this study were to quantitate lip symmetry/asymmetry from clinical photographs; to demonstrate that asymmetry due to functional side shifts (functional asymmetry) leading to unilateral crossbites including the canines, results from measurable thinning of the upper lip and thickening of the lower lip on the side of the crossbite when viewed in the intercuspal contact position; and to show that orthodontic treatment aimed at eliminating the functional shift and crossbite would achieve lip symmetry, both visually and quantitatively. The study consisted of 26 patients, who were divided into two groups: a study group of 13 patients (eight females, five males, aged 8-17 years) with a functional asymmetry, and a control group of 13 age- and gender-matched subjects with other forms of malocclusion without functional asymmetry. All patients in the study group exhibited unilateral crossbites including the canines in intercuspal contact position. Digitized images of frontal facial photographs were analysed for upper and lower lip symmetry pre- and post-orthodontic treatment. The upper and lower lips were subdivided into four quadrants and the surface area and length of each quadrant were measured and expressed as a percentage of the total surface area/length of the relevant lip. The degree of asymmetry was obtained by calculating the difference in percentage area or length between the two quadrants of each lip. In the study group, the lower lip quadrant on the shift side was enlarged while the contralateral side was reduced (mean area ratio 59.9 to 40.1 per cent, mean length ratio 53.0 to 47.0 per cent). The upper lip demonstrated differences that were smaller and inverse. The controls showed a small difference between the right and left sides (less than 1 per cent). After treatment, both groups displayed visual and quantitative lower and upper lip symmetry, i.e. an area or length of approximately 50 per cent of each quadrant. In absolute values, the control patients had up to 3 per cent asymmetry in area regardless of treatment. The patients in the study group exhibited mean absolute asymmetry of 9.2 per cent in the upper lip and 19.8 per cent in the lower lip. Asymmetry values in the study group were reduced to approximately 3 per cent post-treatment. The absolute values of asymmetry in length of all patients were up to 2 per cent in the control group regardless of treatment. The subjects in the study group exhibited mean absolute asymmetry of 6.3 per cent in the upper lip and 8.6 per cent in the lower lip. Asymmetry values in the study group were reduced post-treatment to approximately 2 per cent. Although asymmetry in the study group could be quantitated using both parameters (lip surface area and lip length), the surface area parameter proved to be a more sensitive tool for measuring lip asymmetry.  相似文献   
100.
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