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   167006篇
  免费   11472篇
  国内免费   646篇
耳鼻咽喉   1860篇
儿科学   4077篇
妇产科学   2810篇
基础医学   22971篇
口腔科学   3521篇
临床医学   16102篇
内科学   34900篇
皮肤病学   3417篇
神经病学   15637篇
特种医学   7385篇
外国民族医学   14篇
外科学   26208篇
综合类   1987篇
一般理论   110篇
预防医学   12239篇
眼科学   3527篇
药学   10880篇
  2篇
中国医学   247篇
肿瘤学   11230篇
  2023年   916篇
  2022年   1528篇
  2021年   3470篇
  2020年   2158篇
  2019年   3209篇
  2018年   3689篇
  2017年   2881篇
  2016年   3249篇
  2015年   3733篇
  2014年   5271篇
  2013年   7064篇
  2012年   10679篇
  2011年   11385篇
  2010年   6525篇
  2009年   6243篇
  2008年   10105篇
  2007年   10561篇
  2006年   10444篇
  2005年   10516篇
  2004年   9705篇
  2003年   8986篇
  2002年   8642篇
  2001年   2287篇
  2000年   1965篇
  1999年   2244篇
  1998年   2011篇
  1997年   1633篇
  1996年   1397篇
  1995年   1302篇
  1994年   1186篇
  1993年   1059篇
  1992年   1366篇
  1991年   1255篇
  1990年   1092篇
  1989年   1039篇
  1988年   975篇
  1987年   927篇
  1986年   929篇
  1985年   926篇
  1984年   971篇
  1983年   834篇
  1982年   1014篇
  1981年   904篇
  1980年   760篇
  1979年   690篇
  1978年   684篇
  1977年   563篇
  1976年   539篇
  1974年   549篇
  1973年   482篇
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
221.
BACKGROUND: Studies suggest that patients who undergo off-pump coronary artery bypass grafting (OPCABG) have fewer short-term complications and use fewer inpatient resources than do patients who undergo standard coronary artery bypass grafting (CABG) with extracorporeal circulation. However, dissimilarity between groups in risk factors for complications has hindered interpretation of results. OBJECTIVES: To compare the prevalence of selected complications (atrial fibrillation, stroke, reoperation, and bleeding) and inpatient resource utilization (length of stay, discharge disposition, total charges) between subjects undergoing primary isolated CABG or OPCABG who were matched with respect to key risk factors. METHODS: Retrospective, causal-comparative survey conducted in 1 center for 18 months. Patients who underwent primary isolated CABG or OPCABG were matched for sex, age (within 2 years), left ventricular ejection fraction (within 0.05), and graft-patient ratio (exact match) and compared for prevalence of new-onset atrial fibrillation, stroke, reoperation within 24 hours, and bleeding. Statistical analysis included Wilcoxon and t tests for paired comparisons. RESULTS: The sample (107 matched pairs) was 63% male, with a mean age of 66 (SD 9.5) years, a mean left ventricular ejection fraction of 0.51 (SD 0.13), and a mean graft-patient ratio of 3.41 (SD 0.74). The 2 groups did not differ significantly in New York Heart Association class (P = .43), Acute Physiology and Chronic Health Evaluation III score (P = .22), postoperative beta-blocker use (P = .73), or comorbid conditions. None of the complications examined differed significantly between pairs. CONCLUSION: Patients with comparable risk profiles have similar prevalences of selected complications after CABG and OPCABG.  相似文献   
222.
Teeth with white spot lesions (WSL) might be more prone to enamel loss during bracket debonding. This in vitro study compared enamel loss from teeth with (n = 14) and without (n = 14) WSL after polishing with low-speed finishing burs or disks (Sof-Lex, 3M ESPE, St Paul, Minn). Debonded surfaces were analyzed with a contact stylus profilometer, and digitized data were compared with baseline readings by using AnSur NT software (Regents, University of Minnesota, Minneapolis, Minn). Specimen surfaces were also examined with a scanning electron microscope. Two-way analysis of variance was performed to analyze the data. In teeth without WSL, the volume losses were 0.16 mm(3) for the bur group and 0.10 mm(3) for the disk group; the mean maximum depths were 47.7 microm for the bur group and 54.3 microm for the disk group. In teeth with WSL, the volume losses were 0.06 and 0.17 mm(3), and the mean maximum depths were 35.1 and 48.7 microm for the bur and disk groups, respectively. There were no significant differences in enamel loss between the 2 groups of teeth without WSL (P =.12). However, in teeth with WSL, the burs removed less enamel than the disks (P = 0.006). Scanning electron microscope examination showed that any damage on the enamel surface was usually located in the cervical third of the teeth. On most specimens, even though tooth surfaces appeared resin-free to the naked eye, there were remnants of it. The differences between groups were so small that they might be clinically insignificant.  相似文献   
223.
224.
225.
Sudden hearing loss and acquired immunodeficiency syndrome   总被引:1,自引:0,他引:1  
We have presented a case of a male homosexual with documented acquired immune deficiency syndrome in whom sudden sensorineural hearing loss developed after a series of opportunistic infections and before a massive intracerebral hemorrhage. Two major possible causes of his hearing loss are (1) actual involvement of spiral ganglion or acoustic division of the eighth cranial nerve by HTLV III virus, or (2) cryptococcal meningitis. He ultimately died after a series of neurological complications developed. These complications, which are common in patients with AIDS, include progressive dementia, obtundation, and coma. As the number of patients with AIDS in our society increases over the next 5 years, it will become more important for the otolaryngologist to recognize the complications of this disease that involve the ear, nose, throat, head, and neck. Sudden sensorineural hearing loss is one of these complications. The acquired immune deficiency syndrome, at this point, might best be treated by an approach of preventive medicine. However, such an approach would have far-reaching social and political implications--perhaps more so than in other venereally spread diseases. In the interim, the otolaryngologist-head and neck specialist is required to recognize AIDS as it manifests itself in the head and neck. In this case, sudden-onset sensorineural hearing loss was the otolaryngologic presentation of the AIDS.  相似文献   
226.
Paul L. Booth  W. Eric Thomas   《Brain research》1991,548(1-2):163-171
Ramified microglial cells were investigated in primary cultures of dissociated cerebral cortical tissue from rats. The identification of these cells was confirmed through immunohistochemical staining with 7 monoclonal antibodies selective for microglia. While there was significant variation in staining intensity with different antibodies, all stained the identified ramified cells; the antibodies OX-42 and ED1 yielded the most intense immunoreactivity. Based on distinctive morphological features, the microglia could be identified in living cultures where they were monitored using time-lapse video recording. This technique revealed extremely dynamic features of cellular plasticity and motility. Ramified microglia exhibited constant and rapid alterations in the size and shape of their cell body with an associated extension and retraction of processes; concomitantly, the cells moved about in a circumscribed area. These features of plasticity and motility were unique to this cell type, and correlated with OX-42 immunostaining. The microglia also possessed a differentially high level of pinocytotic activity; this too was correlated with OX-42 staining. From the nature of their morphological plasticity and motility, high pinocytosis, and cellular distribution, it is hypothesized that the ramified microglia specifically function as a system of fluid cleansing in normal brain tissue.  相似文献   
227.
228.
Tuberculosis involving the soft tissue from adjacent bone or joint is well recognized. However, primary tuberculous pyomyositis, tuberculous bursitis, and tuberculous tenosynovitis are rare entities constituting 1% of skeletal tuberculosis. Tuberculous tenosynovitis involves most commonly the tendon sheaths of the hand and wrist, and tuberculous bursitis occurs most commonly around the hip. The greater trochanteric bursa and the greater trochanter are the most frequent sites of tuberculous bursitis. Cases of primary tuberculous pyomyositis and tenosynovitis of the tendons of the ankle and foot are seldom reported in the radiology literature. All imaging modalities-plain radiography, bone scan, computed tomography, and magnetic resonance imaging (MRI)--provide information that is helpful in determining therapy. MRI in particular, with its multiplanar capabilities and superb contrast of soft tissue, can demonstrate the extent of the soft tissue mass and access the adjacent bones and joints. However, MRI has no diagnostic specificity in regard to tuberculosis, and in nonendemic areas, biopsy is strongly recommended. All patients in this review were permanent residents of North America or Western Europe and were immunocompetent. Examples of atypical presentations of the above entities are demonstrated.  相似文献   
229.
230.
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