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   17005篇
  免费   1507篇
  国内免费   263篇
耳鼻咽喉   741篇
儿科学   1145篇
妇产科学   1003篇
基础医学   1699篇
口腔科学   346篇
临床医学   1388篇
内科学   1864篇
皮肤病学   197篇
神经病学   1701篇
特种医学   478篇
外国民族医学   2篇
外科学   1245篇
综合类   1858篇
现状与发展   2篇
一般理论   2篇
预防医学   2556篇
眼科学   654篇
药学   823篇
  11篇
中国医学   313篇
肿瘤学   747篇
  2024年   38篇
  2023年   255篇
  2022年   532篇
  2021年   733篇
  2020年   686篇
  2019年   643篇
  2018年   596篇
  2017年   684篇
  2016年   746篇
  2015年   644篇
  2014年   1095篇
  2013年   1262篇
  2012年   957篇
  2011年   1016篇
  2010年   871篇
  2009年   795篇
  2008年   782篇
  2007年   793篇
  2006年   721篇
  2005年   620篇
  2004年   470篇
  2003年   398篇
  2002年   364篇
  2001年   342篇
  2000年   268篇
  1999年   229篇
  1998年   203篇
  1997年   198篇
  1996年   182篇
  1995年   149篇
  1994年   166篇
  1993年   140篇
  1992年   136篇
  1991年   118篇
  1990年   111篇
  1989年   100篇
  1988年   88篇
  1987年   70篇
  1986年   70篇
  1985年   94篇
  1984年   56篇
  1983年   40篇
  1982年   50篇
  1981年   38篇
  1980年   53篇
  1979年   32篇
  1978年   28篇
  1977年   25篇
  1976年   22篇
  1975年   23篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
目的探讨鼻内镜下经鼻腔直接入路行蝶窦及中颅窝手术的方法. 方法鼻内镜下经较宽大一侧鼻腔将中鼻甲向外推移,鼻腔扩张器扩大视野,直达并开放蝶窦前壁, 鼻内镜与显微镜联合切除病变. 结果 10例孤立性蝶窦炎术后症状消失.6例蝶窦囊肿、脑膜瘤均一次手术切除.32例垂体腺瘤17例全切除,12例次全切除,3例大部分切除,术后补充X刀治疗.48例术后随访6个月~3.5年,平均2.5年,蝶窦囊肿、蝶窦炎、脑膜瘤无复发,3例垂体腺瘤复发,无颅内感染并发症,无鼻腔粘连、鼻出血等鼻腔并发症. 结论鼻内镜联合显微镜经鼻腔蝶窦及中颅窝手术损伤小、出血少、手术时间短、效果好.  相似文献   
12.
Summary High-resolution computed tomography (HRCT) provides excellent contrast between osseous structures, air and soft tissue in conjunction with high spatial resolution. Therefore, thin-section HRCT with bone window setting is the method of choice for the examination of the middle ear structures. The indications are acute and chronic inflammatory changes, cholesteatoma and tumor, the “postoperative middle ear”, and malformations. In most cases, HRCT enables differentiation between inflammatory changes, cholesteatoma, and tumor. The excellent depiction of subtle osseous details enables the identification of erosions of the ossicles or of the bony walls of the mastoid cells, of osseous defects of the tegmen, of the bony labyrinth, and of the tympanic course of the facial canal. In addition, HRCT enables excellent depiction of reconstructions of the ossicles or prosthesis of the ossicles. Although HRCT is the first method of choice, magnetic resonance imaging (MRI) may provide additional information and lead to a more accurate diagnosis in some cases. This is explained by the excellent soft tissue contrast provided by MRI. In addition, MRI offers the possibility of using various pulse sequences and the administration of IV contrast material. Therefore, MRI may allow the differentiation between inflammatory changes, cholesteatoma, and tumor in those cases in which accurate diagnosis cannot be made by HRCT. The differentiation between a meningocele or meningoencephalocele and other entities such as tumors or cholesteatoma can be established by MRI. Furthermore, MRI can accurately depict cases of labyrinthitis or of neuritis of the facial nerve or of intracranial disease caused by middle ear processes, while this is not always possible by HRCT. In summary, HRCT of the middle ear is the method of choice, but MRI may provide supplementary information in those cases in which accurate diagnosis cannot be established by HRCT.   相似文献   
13.
A comparison of 121 mature-age and 270 normal-age entrants who graduated from the University of Queensland Medical School between 1972 and 1987 shows that mature-age entrants are some 7 years older, are more likely to come from public (state) schools and less likely to have parents in professional/technical occupations. Otherwise, the two groups were similar in terms of gender, marital status, number of children, ethnic background and current practice location. The educational background of mature-age entrants prior to admission includes 44.6% with degrees in health-science areas and 31.4% with degrees in non-health areas. Reasons for delayed entry of mature-age entrants include late consideration of medicine as a career (34.7%), financial problems (31.4%), dissatisfaction with previous career (30.6%), poor academic results (19.8%), or a combination of the above factors. Motivations to study medicine include family influences (more so in normal-age entrants), altruistic reasons (more so in mature-age entrants) and a variety of personal/social factors such as intellectual satisfaction, prestige and financial security (similar for both groups) and parental expectations (more so in normal-age entrants). Mature-age entrants experienced greater stress throughout the medical course, especially with regard to financial difficulties, loneliness/isolation from the students and family problems (a greater proportion were married with children). While whole-course grades were similar in both groups, normal-age entrants tended to win more undergraduate honours/prizes and postgraduate diplomas/degrees, including specialist qualifications. Practice settings were similar in terms of group private practice, hospital/clinic practice or medical administration, but there was a greater proportion of mature-age entrants in solo private practice, and a smaller proportion in teaching/research. If given the time over, some two-thirds of both groups would choose medicine as a career. Reasons for job satisfaction include helping patients, intellectual stimulation and financial rewards. Reasons for dissatisfaction include pressure of work, red-tape/paperwork, 'doctor-bashing', long working hours, emotional strain, financial pressure, unfulfilled career expectations and irritation with trivial medical complaints.  相似文献   
14.
本文测量了180例干燥颅骨的总面角、鼻面角和齿槽面角三项角度项目;分析了颅骨在性别和年龄上的颌型差异;探讨了颅骨发育中的某些变化趋势。本文的部分数据同其它文献作了比较  相似文献   
15.
Abstract: It seems clear that the pineal hormone, melatonin (N-acetyl-5-methoxytryptamine), is involved in the reproductive behavior of several animal species including humans. Moreover, several data also support a role for 5-methoxytryptophol (ML), another pineal hormone, in the control of sexual processes. To test the role of ML in human reproductive axis, 128 healthy children, 68 boys and 60 girls, were studied. Each of these groups was divided in three age subgroups of 6, 11, and 14 years. A single blood sample (0900 hours) was obtained from each subject to determine melatonin, ML, FSH, LH, estradiol (girls), and testoterone (boys) by RIA. Statistical analysis of the data included ANOVA-II (factor I: age, factor II: sex) and an analysis of covariance with age as covariate. A similar plasma melatonin concentration, with a significant decrease between 6 and 11 years, was found in boys and girls. Melatonin concentrations correlate well with initiation of the pubertal development in these children, although no sex differences were found. Concentrations of ML are approximately 50% of those of melatonin. In contrast to melatonin, ML levels show significant age and sex differences. Plasma ML concentration significantly increased in boys ( P < 0.001) and decreased in girls (P < 0.001) after 8 years of age. These results support the hypothesis that, besides melatonin, other pineal compounds such as ML may be involved in the maturation process in humans. The pineal indole ML may also be used as a marker of the different chronobiology in the pubertal development in boys and girls.  相似文献   
16.
Before meaningful conclusions can be drawn from clinical measures of cerebral blood perfusion, the precision of the measurement must be determined and set in the context of inter- and intrasubject sources of variability. This work establishes the reproducibility of perfusion measurements using the noninvasive MRI technique of continuous arterial spin labeling (CASL). Perfusion was measured in 34 healthy normal subjects. Intersubject variability was assessed, and age and gender contributions were estimated. Intersubject variation was found to be large, with up to 100% perfusion difference for subjects of the same age and gender. Repeated measurements in one subject showed that perfusion remains remarkably stable in the short term when compared with intersubject variation and the large capacity for perfusion change in the brain. A significant decrease in the ratio of gray-matter to white-matter perfusion was found with increasing age (0.79% per year (P < 0.0005)). This appears to be due mainly to a reduction in gray-matter perfusion, which was found to decrease by 0.45% per year (P = 0.04). Regional analysis suggested that the gray-matter age-related changes were predominantly localized in the frontal cortex. Whole-brain perfusion was 13% higher (P = 0.02) in females compared to males.  相似文献   
17.
Imaging is an essential diagnostic tool in reconstructive middle ear surgery, especially in pre-operative planning. Due to ongoing improvement of imaging quality and development of new imaging techniques like e.g. rotational tomography (RT) post-operative follow-up and immediate evaluation of surgical results may become more important. The aim of this experimental study was to evaluate RT as a new tool for postoperative determination of middle ear anatomy and implant position in temporal bones. RT was performed in ten temporal bone specimen after insertion of different middle ear prostheses concerning material, shape and length (PORP; TORP; Stapes piston). An implantable hearing device (Symphonix Soundbridge®) was also implanted and visualized. For comparison some specimen additionally underwent conventional computed tomography (CT), including the newest technology. Characterization of anatomical structures of the temporal bone using RT was of comparable quality to conventional CT-scans in all investigated specimen while requiring approximately 30% of the CT’s irradiation exposure. Unlike CT the RT showed almost no problems due to metallic artefacts of the implanted prostheses. Furthermore RT enabled a 3-dimensional view of the temporal bone and angle determination of inserted prostheses towards the tympanic membrane and/or the malleus handle. Detailed imaging of the prostheses allowed determination of shape, material and localization within the specimen’s reconstructed middle ear. The new imaging technique of RT allows precise presentation of anatomical structures and middle ear implants in temporal bones. Following these experimental results it will be our future work to evaluate this method in clinical practise.  相似文献   
18.
Digital volume tomography (DVT) is an extension of panoramic tomography. With this diagnostic technique, characterized by high resolution, a narrow section width (0.125 mm) and three-dimensional display, small pathological processes can be well visualized. Twenty-five patients with the history of a progressive hearing loss were examined with DVT (Accu-I-tomo, Morita, Japan). The results were compared with pre- and intraoperative findings to evaluate the diagnostic value of DVT in cases of erosion of the ossicular chain. With high resolution and artifact-free demonstration of the middle ear and the ossicular chain, it was possible to define its continuity preoperatively by DVT in all 25 cases. An intact ossicular chain was found by DVT in 13 cases and was later confirmed by surgery. The predicted erosion of the ossicles was verified in 12 patients, and a tympanoplasty type III was performed. Digital volume tomography is an excellent technique to examine the middle ear cleft and inner ear, and expands the application of diagnostic possibilities in the lateral skull base. Therefore, improvement in preoperative diagnosis is achieved along with more accurate planning of the surgical procedure. Digital volume tomography delivers a small radiation dose with a high resolution and a low purchase price for the equipment.  相似文献   
19.
大脑中动脉动脉瘤的血管内治疗   总被引:3,自引:3,他引:0  
目的探讨血管内治疗大脑中动脉动脉瘤的可行性、安全性和有效性。方法回顾性分析采用血管内治疗的24例大脑中动脉动脉瘤患者的临床资料,包括患者年龄、临床分级、动脉瘤出血量、部位、形态、瘤颈宽度、血管痉挛程度及术中应用技术等。结果100%栓塞17例,95%栓塞4例,90%栓塞3例。1例患者术中血管痉挛加重致不完全失语。随访无动脉瘤再破裂出血病例,1例患者出现迟发性血管痉挛。结论血管内治疗大脑中动脉动脉瘤是一种安全、有效的方法。  相似文献   
20.
AIMS: To examine the association between maternal glycated haemoglobin in the second half of diabetic pregnancies and the relative risk of delivering large-for-gestational-age (LGA) babies, controlling for maternal body mass index (BMI) before pregnancy, weight gain, age, White class and smoking habits. METHODS: We identified all pregnant diabetic women in North Jutland County, Denmark from 1985 to 2003. Data on HbA(1c) values from the 20th gestational week to term were collected from medical records and the babies were classified as large, normal or small for gestational age. The association between glycated haemoglobin (HbA(1c)) and relative risk of delivering an LGA baby was quantified based on logistic regression models and stratified analysis controlling for the five covariates. RESULTS: We included 209 singleton pregnancies with assessable HbA(1c) values of which 59%[95% confidence interval (CI) 52-65%] terminated with an LGA baby. Increasing levels of HbA(1c), BMI and weight gain were all associated with increasing risk of delivering an LGA baby. Analyses stratified according to maternal BMI showed that the association between HbA(1c) and risk of delivering an LGA baby was restricted to pregnancies with pre-pregnancy BMI > 23 kg/m(2). We found no association between HbA(1c) and risk of delivering an LGA baby in pregnancies with lower BMI. CONCLUSION: The positive association between glycated haemoglobin and birth of an LGA baby seems to be restricted to women with BMI > 23 kg/m(2).  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