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   19771篇
  免费   1075篇
  国内免费   68篇
耳鼻咽喉   239篇
儿科学   505篇
妇产科学   365篇
基础医学   2832篇
口腔科学   415篇
临床医学   1756篇
内科学   3662篇
皮肤病学   812篇
神经病学   2287篇
特种医学   1144篇
外国民族医学   11篇
外科学   2993篇
综合类   156篇
一般理论   5篇
预防医学   980篇
眼科学   314篇
药学   1061篇
中国医学   64篇
肿瘤学   1313篇
  2023年   158篇
  2022年   252篇
  2021年   476篇
  2020年   314篇
  2019年   448篇
  2018年   485篇
  2017年   441篇
  2016年   539篇
  2015年   566篇
  2014年   748篇
  2013年   910篇
  2012年   1442篇
  2011年   1503篇
  2010年   889篇
  2009年   765篇
  2008年   1274篇
  2007年   1260篇
  2006年   1205篇
  2005年   1196篇
  2004年   1021篇
  2003年   951篇
  2002年   890篇
  2001年   215篇
  2000年   205篇
  1999年   240篇
  1998年   211篇
  1997年   150篇
  1996年   156篇
  1995年   104篇
  1994年   105篇
  1993年   82篇
  1992年   100篇
  1991年   111篇
  1990年   73篇
  1989年   73篇
  1988年   71篇
  1987年   79篇
  1986年   70篇
  1985年   68篇
  1984年   60篇
  1983年   48篇
  1982年   47篇
  1981年   45篇
  1980年   48篇
  1979年   58篇
  1978年   47篇
  1977年   40篇
  1976年   32篇
  1973年   27篇
  1972年   26篇
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
11.
Flow cytometry is a quantitative cytologic technique with demonstrated utility in the assessment of prostate cancer as well as other tumors. The authors summarize current data on its use in disease detection and diagnosis, prognostic evaluation, and monitoring of response to therapy. They also project future developments.  相似文献   
12.
13.
Pneumonia is one of the leading causes of morbidity, hospitalization, and mortality in both industrialized and developing countries. In particular, pulmonary infections acquired in the community, and pneumonias arising in the hospital setting, represent a major medical and economic problem and thus a continuous challenge to health care. For the radiologist, it is important to understand that community-acquired pneumonia (CAP) and nosocomial pneumonia (NP) share a number of characteristics, but should, in many respects be regarded as separate entities. CAP and NP arise in different populations, host different spectra of causative pathogens, and pose different challenges to both the clinician and the radiologist. CAP is generally seen in outpatients, is most frequently caused by Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, and Chlamydia, and its radiologic diagnosis is relatively straightforward. NP, in contrast, develops in the hospital setting, is commonly caused by gram-negative bacteria, and may generate substantial problems for the radiologist. Overall, both for CAP and NP, imaging is an integral component of the diagnosis, important for classification and differential diagnosis, and helpful for follow-up.  相似文献   
14.
Corticotropin-releasing hormone receptor type 1 (CRH-R1)-deficient mice display reduced anxiety-like behavior, a chronic corticosterone deficit, and an impaired neuroendocrine stress response caused by disruption of the hypothalamic-pituitary-adrenocortical (HPA) axis. The molecular substrates and pathways of CRH/CRH-R1-dependent signaling mechanisms underlying the behavioral phenotype as well as the consequences of lifelong glucocorticoid deficit remain largely obscure. To dissect involved neuronal circuitries, we performed comparative expression profiling of brains of CRH-R1 mutant and wild-type mice using our custom made MPIP (Max Planck Institute of Psychiatry) 17k cDNA microarray. Microarray analysis yielded 107 genes showing altered expression levels when comparing CRH-R1 knockout mice with wild-type littermates. A significant proportion of differentially expressed genes was related to control of HPA and hypothalamic-pituitary-thyroid (HPT) axes reflecting not only the disturbance of the HPA axis in CRH-R1 mutant mice but also the interplay of both neuroendocrine systems. The spatial analysis of regulated genes revealed a prevalence for genes expressed in the cerebral microvasculature. This phenotype was confirmed by the successful cross-validation of regulated genes in CRH overexpressing mice. Analysis of the cerebral vasculature of CRH-R1 mutant and CRH overexpressing mice revealed alterations of functional rather than structural properties. A direct role of the CRH/CRH-R1 system was supported by demonstrating Crhr1 expression in the adult murine cerebral vasculature. In conclusion, these data suggest a novel, previously unknown role of the CRH/CRH-R1 system in modulating neurovascular gene expression and function.  相似文献   
15.
Preoperative cytologic examinations were performed on bronchial material from 92 patients with postsurgical (pathologic) stage I (American Joint Committee) adenocarcinoma of the lung. All patients were followed up for at least 5 years or until death; thus, cases of adenocarcinoma metastatic to the lungs were virtually excluded. Only 22 patients (24%) had abnormal preoperative cytologic findings. This low cytologic sensitivity is ascribed to the small size and peripheral location of the tumors. Large lesions of high histologic grades were more likely to have positive preoperative cytologic findings than small, well-differentiated ones.  相似文献   
16.
17.
18.
Depressive symptoms are common in patients with neurodegenerative disorders. Imaging studies suggest that a disruption of frontal-subcortical pathways may underlie depression associated with basal ganglia disease. This pilot study tested the hypothesis that frontal dysfunction contributes to depression associated with multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). Depressed patients with MSA (n = 11), PSP (n = 9), and age-matched controls (n = 25) underwent measures of cerebral glucose metabolism applying positron emission tomography with (18)F-fluorodeoxyglucose. Regional metabolism in the patient groups was compared to the normal subjects using the voxel-based statistical parametric mapping. Depressive symptom severity (Hamilton Depression Rating) and degree of locomotor disability (Hoehn & Yahr) were assessed in the patient groups. The association between prefrontal metabolism and the occurrence of depressive symptoms and the degree of locomotor disability was investigated. When compared to controls, MSA patients revealed significant metabolic decreases in bilateral frontal, parietal, and cerebellar cortex and in the left putamen. In PSP patients, significant hypometabolism was demonstrated in bilateral frontal cortex, right thalamus, and midbrain. Depression severity but not the patients' functional condition was significantly associated with dorsolateral prefrontal glucose metabolism in both patient groups. The findings of this pilot study support the hypothesis that depressive symptoms in MSA and PSP are associated with prefrontal dysfunction.  相似文献   
19.
Abstract  – The dental records made on presentation of 1367 consecutive patients (731 females and 636 males) for orthodontic treatment at a private orthodontic practice between 1998 and 2002 were examined for data relating to trauma to the permanent incisors. The results showed that 10.3% of these patients had suffered from dental trauma before the onset of orthodontic treatment. The highest prevalence of dental trauma was determined in the 11–15 years age group, corresponding to the dental developmental stage of the late mixed dentition. The most frequently affected teeth were the maxillary central incisors (79.6%), and the most common types of trauma were fracture of enamel–dentin without pulpal involvement (42.7%) and fracture of enamel (33.8%). Compared to patients with normal overjet and adequate lip coverage, the frequency of dental trauma was significantly higher in patients with increased overjet and adequate lip coverage ( P  = 0.028) or with increased overjet and inadequate lip coverage ( P  = 0.003). The results of the present study indicate that a significant percentage of candidates for orthodontic treatment, and especially those with increased overjet and inadequate lip coverage, suffer trauma to their permanent incisors before the onset of orthodontic treatment. It might also be concluded that preventive orthodontic treatment of such patients should be initiated and completed before the age of 11, i.e. in the early to middle mixed dentition.  相似文献   
20.
Background/aim: Mid-infrared spectroscopy is a versatile method for in vivo investigation of skin after topical treatment with skin care products.
Methods: FTIR-spectrometer (Bruker Optics) with a flexible silver halide fibre probe (Infrared Fiber Sensors).
Results: Absorbance spectra from 700 to 3000 cm−1 have been recorded to gain information about proteins (amide-I and amide-II vibrations at 1650 and 1550 cm−1), esters (1740 cm−1), carboxylic acid (1710 cm−1), polyalcohols (1050 cm−1) and hydrocarbons (CH n vibrations at 2800–3000 cm−1).
Conclusions: Using the particular light guide, we were able to measure for the first time the effects of lip care products on lips directly. Furthermore, water binding and glycerol content of the skin could be determined simultaneously, as well as the replenishment of lipids by lipid-enriched bath oil.  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