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   350975篇
  免费   23235篇
  国内免费   7821篇
耳鼻咽喉   4191篇
儿科学   11182篇
妇产科学   6886篇
基础医学   29123篇
口腔科学   8109篇
临床医学   38344篇
内科学   45013篇
皮肤病学   4865篇
神经病学   19790篇
特种医学   8173篇
外国民族医学   31篇
外科学   38107篇
综合类   51674篇
现状与发展   12篇
一般理论   29篇
预防医学   35449篇
眼科学   6079篇
药学   30279篇
  388篇
中国医学   30750篇
肿瘤学   13557篇
  2023年   5654篇
  2022年   9946篇
  2021年   13613篇
  2020年   12858篇
  2019年   18792篇
  2018年   16278篇
  2017年   13149篇
  2016年   10608篇
  2015年   9885篇
  2014年   20230篇
  2013年   21854篇
  2012年   18551篇
  2011年   20180篇
  2010年   16188篇
  2009年   14892篇
  2008年   14515篇
  2007年   14998篇
  2006年   13182篇
  2005年   11500篇
  2004年   9338篇
  2003年   8216篇
  2002年   6491篇
  2001年   5801篇
  2000年   4812篇
  1999年   4174篇
  1998年   3448篇
  1997年   3277篇
  1996年   2829篇
  1995年   2721篇
  1994年   2627篇
  1993年   2129篇
  1992年   2119篇
  1991年   1836篇
  1990年   1618篇
  1989年   1461篇
  1988年   1376篇
  1987年   1182篇
  1985年   3877篇
  1984年   4875篇
  1983年   3401篇
  1982年   3863篇
  1981年   3596篇
  1980年   3205篇
  1979年   2942篇
  1978年   2555篇
  1977年   1925篇
  1976年   2170篇
  1975年   1643篇
  1974年   1436篇
  1973年   1282篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
目的 探讨提高上尿路结石碎石成功率的微创治疗方法。方法 采用经皮肾穿微造瘘输尿管镜气压弹道碎石,术中放置双J管,术后配合体外冲击波碎石术(ESWL)治疗上尿路结石48例。结果 结石总排净率为89.1%,结石最小排净率79.2%,无严重并发症发生。结论 该方法结石排净率高,创伤较小,手术并发症少,是上尿路结石较为理想的微创治疗方法。  相似文献   
62.
After removal of intraductal stones, a 10‐Fr or 7‐Fr pancreatic stent was placed in 16 patients with upstream ductal dilation proximal to a stricture of the main pancreatic duct. Stents were removed after a mean duration of 52.5 days. Nine patients underwent repeated stenting. About one year after removal of the initial stent, when the remaining upstream ductal dilation was found on follow‐up pancreatograms, the next stent was replaced. Repeated stenting improved outflow of pancreatic juice more effectively than one‐time stenting. Correlation between long‐term pain relief without recurrence of intraductal stones and reduction of duct diameter was also shown. Stent occlusion was observed in 14 of 30 stents. Stent occlusion was frequently associated with recurrence of pancreatitis and intraductal stones, and was also associated with morphologic changes in the pancreatic ductal system. Although there were no significant differences between stent patency of the initial stents and that of the next stents, stent patency of 10‐Fr stents was superior to that of 7‐Fr stents. 10‐Fr stents should be removed within 8 weeks and 7‐Fr stents should be removed within 4 weeks for the prevention of stent occlusion. Repeated stenting with short‐term stenting is therefore considered a safe and effective protocol of endoscopic pancreatic stenting.  相似文献   
63.
The naevus of Ota (naevus fusculocoeruleus ophthalmomaxillaris) was first described by the Japanese dermatologist M. T. Ota in 1939. It has a reported incidence of 0.2% to 1% in the Japanese population. It usually occurs in the skin innervated by the first or second branch of the trigeminal nerve. The naevus comprises dermal melanocytes and is congenital or acquired during adolescence. Commonly associated lesions include scleral melanocytosis and other ocular manifestations as well as lesions of the tympanic membrane, oral and intranasal mucosa and leptomeninges. Diseases associated with Ota's naevus in rare cases are open-angle glaucomas and melanoma. The naevus of Ota in Europeans is a rare manifestation. We report the very rare case of a bilateral naevus of Ota associated with enoral melanocytosis in a white European person.  相似文献   
64.
目的:探讨股骨头缺血坏死的病理和影像学研究进展情况。方法:阅读并分析关于股骨头缺血坏死的文献。结果:影像学检查反映疾病的病理改变,在诊断中占有重要地位。结论:磁共振成像具有很高的敏感性和准确性,不仅能发现股骨头坏死的早期病变,且能反映病变的范围和程度,对早期诊断和治疗具有积极意义。  相似文献   
65.
Summary Quantitative aspects of the microanatomy of the pineal gland and other neuroendocrine and circumventricular structures were studied in a small, reproductively suppressed, female Naked Mole-rat from central Kenya, Africa. The atrophic pineal is the smallest in absolute size (0.002135 mm3) of any so far described in a species of rodent, and in size relative to body weight is second only to that of another tropical species. The subcommissural organ and posterior collicular recess are also relatively small and less well differentiated than those in most other examined rodent species. In contrast, the subfornical organ, OVLT and median eminence are large and well vascularized. It is concluded that the pineal in this species follows the previously described trend among rodents of relatively smaller size in species whose centers of distribution are in lower latitudes. Although the pineal is atrophic, the Naked Mole-rat still exhibits 24-hour and seasonally timed patterns of behavior and seasonal reproduction. However, in this species these events are probably cued by moisture, temperature and social factors rather than by photic information.  相似文献   
66.
While an exacerbation in allergic symptoms corresponding to seasons has long been reported, few studies have investigated the association between the season of birth and allergic disorders. The aim of this study was to investigate whether the climatologic data before and after birth affected the incidence of atopic dermatitis (AD) and the results of allergy-related blood tests in early infancy. From February 1995 to January 2000, 2136 infants were tested for AD and followed for 12 months. AD patients were tested by using allergy-related blood tests. Data were compared according to the month of birth and the climatologic data using a computed statistical software package. Six hundred and thirty infants had AD before 12 months old, and significant differences were found according to the season of birth (p < 0.0001). Infants born in spring showed the lowest (22.3%) incidence, while those born in autumn showed the highest (34.6%). In 369 patients, total serum IgE levels, and serum specific IgE levels with egg white at 3 months old were also different according to the season of birth. All of these levels were lower in patients born in spring and summer, and higher in patients born in autumn and winter. Furthermore, the cumulative sunshine amount during the 3 months before and after birth was inversely correlated, while the average temperature over the 3 months before birth was positively correlated to the incidence of AD according to the month of birth. The climatologic data around birth may play an important role in whether an infant develops allergies.  相似文献   
67.
Masumi Ichikawa   《Brain research》1987,420(2):253-258
The rearrangement of terminations from the bed nucleus of stria terminalis (BST) was examined in the medial amygdaloid nucleus (MAN) at 2 months following the lesion of the accessory olfactory bulb (AOB) using an electron microscopy and degeneration study. At 2 days following a BST lesion, the number of degenerating synapses was 0.7 ± 0.1 (mean±S.E.M.) per unit area (2500 μm2 in the molecular layer, and 3/0 ± 0.3 in the cellular part. At 2 months after an AOB lesion, the degenerating synapses from the AOB had completely disappeared from the MAN. The BST was then lesioned at 2 months after the AOB lesion and, 2 days following this BST lesion, the degenerating synapses were counted in MAN. The numbers observed were 3.3 ± 0.6 per unit area in the molecular layer and 4.5 ± 0.4 in the cellular part. Therefore, the number of these degenerating synapses increased significantly within the molecular layer, though, in the cellular part the number of synapses was not significantly elevated over control. No differences in postsynaptic profiles (ratio of synapses on dendritic spine to dendritic shaft) were observed after the AOB lesion. These results indicate that the BST fibers formed new synapses in the molecular layer following the denervation of AOB fibers. The possibility of new synapse formation by other afferent fibers in addition to the AOB fibers is discussed as is the relationship between lesion induced synaptic reorganization and functional recovery after injury.  相似文献   
68.
The spectral response curve (amplitude versus wavelength) of the R2 of the early receptor potential (ERP) was studied in normal, protan, and deutan subjects. The R2 amplitude peaked at 520nm in most normal subjects. The R2 at long wavelengths was smaller than normal in protans and larger than normal in deutans when the maximum amplitudes were normalized to 100% at the peak. The ratio of the R2 amplitude at 460 nm to that at 600 nm clearly differed between protans and deutans. The ERP and the rapid off-response, which is mainly due to the cessation of the late receptor potential, were recorded in the same subjects. The ratio of the sensitivity of the rapid off-response at 500 nm to that at 600 nm was correlated with the ratio of the R2 amplitude at 460 nm to that at 600nm (correlation coefficient, 0.823, p < 0.001). This study, in conjunction with our previous study, indicates that the abnormality is in the outer segments of the cones in protans and deutans.  相似文献   
69.
70.
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