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   3797篇
  免费   409篇
  国内免费   82篇
耳鼻咽喉   184篇
儿科学   77篇
妇产科学   19篇
基础医学   835篇
口腔科学   1055篇
临床医学   300篇
内科学   258篇
皮肤病学   32篇
神经病学   51篇
特种医学   215篇
外国民族医学   2篇
外科学   480篇
综合类   311篇
预防医学   52篇
眼科学   23篇
药学   104篇
中国医学   23篇
肿瘤学   267篇
  2024年   7篇
  2023年   45篇
  2022年   58篇
  2021年   102篇
  2020年   127篇
  2019年   134篇
  2018年   136篇
  2017年   117篇
  2016年   130篇
  2015年   133篇
  2014年   188篇
  2013年   203篇
  2012年   180篇
  2011年   157篇
  2010年   184篇
  2009年   170篇
  2008年   169篇
  2007年   148篇
  2006年   159篇
  2005年   148篇
  2004年   114篇
  2003年   123篇
  2002年   132篇
  2001年   118篇
  2000年   84篇
  1999年   91篇
  1998年   94篇
  1997年   104篇
  1996年   77篇
  1995年   56篇
  1994年   75篇
  1993年   63篇
  1992年   49篇
  1991年   66篇
  1990年   52篇
  1989年   33篇
  1988年   31篇
  1987年   32篇
  1986年   25篇
  1985年   16篇
  1984年   28篇
  1983年   10篇
  1982年   21篇
  1981年   13篇
  1980年   16篇
  1979年   19篇
  1978年   16篇
  1976年   15篇
  1975年   7篇
  1974年   5篇
排序方式: 共有4288条查询结果,搜索用时 15 毫秒
31.
When the function of salivary glands was abolished by applying ligatures to their ducts and the function of one half of the diaphragm muscle was abolished by sectioning of its phrenic nerve, the choline acetyltransferase activity was found to be increased in not duct-ligated glands and in the intact hemidiaphragm 4 weeks later. The increase was not seen within the first week. The increase in activity appears to be particularly manifested in the nerve endings, since it was seen in the hemidiaphragm but not in the phrenic nerve. Increased stream of impulses in the efferent nerves is thought to be the cause of this increase in choline acetyltransferase activity.  相似文献   
32.
Department of Pathological Physiology, N. A. Semashko Moscow Medical Stomatologic Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR A. D. Ado.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 3, pp. 246–297, March, 1991.  相似文献   
33.
Summary MAM-3 and MAM-6 antigens of human milk fat globule membrane were detected immunohistochemically in 93 cases of salivary gland tumours as well as in normal glands. The antigens were visualized in 10% formalin-fixed paraffin sections. MAM-3 (MoAbs 115G3, 67D11) antigen was distributed in intercalated and striated duct cells of the normal salivary glands, and in luminal tumour cells and squamous metaplastic cells of pleomorphic adenomas. In pleomorphic adenomas the frequency of positive staining with MoAb 67D11 (54/67; 80.6%) was higher than that with MoAb 115G3 (36/67; 53.7%). MAM-6 (MoAbs 115D8, 115F5) antigen was expressed in luminal and lateral borders of serous acinar cells and ductal of the normal glands, and also in luminal borders of tubulo-ductal and glandular structures of salivary gland tumours. Ductal basal cells were characterized by existence of positive staining for MAM-6 antigen, in adenolymphomas MAM-6 antigen was restricted to the basal tumour cells. Some mucous cells of mucoepidermoid tumours were stained specifically with MoAb 115G3, and epidermoid cells of mucoepidermoid carcinomas manifested MAM-6 antigen staining. Immunohistochemical localization of MAM-6 antigen resembled that of epithelial membrane antigen (EMA) detected with MoAb.  相似文献   
34.
将类霍乱毒素B原结合的辣根过氧化物酶(CB-HRP)注入大鼠一侧颌、舌下腺,标记了脑干内支配该腺副交感节前神经元的胞体及其轴、树突。在光学显微镜下,对所标神经元的位置、胞体形态、大小、树突的分布以及轴突在脑干内的行程做了较为系统的观察和测量,并结合有关参数的相关分析,对泌涎神经元的某些生理学特性做了初步探讨。  相似文献   
35.
The specific cellular immune response to the partially purified pancreatic antigen was studied by the peripheral blood lymphocyte proliferation assay in patients with chronic pancreatitis, Sjögren's syndrome, and primary biliary cirrhosis. A significant positive result (stimulation index >2.0) was observed in 7 of 21 patients with idiopathic chronic pancreatitis (33%;P<0.05), 6 of 7 patients with Sjögren's syndrome-associated chronic pancreatitis (86%;P<0.0005), and 6 of 11 patients with Sjögren's syndrome (55%;P<0.01), compared to normal controls whose stimulation index was 0.94±0.28 (mean ± SD;n=14; range, 0.56–1.60). On the other hand, patients with alcoholic chronic pancreatitis (17%;n=12), stone-related chronic pancreatitis (0%;n=7), primary biliary cirrhosis-associated chronic pancreatitis (33%;n=3), primary biliary cirrhosis (0%;n=4), systemic lupus erythematosus (17%;n=6), and autoimmune thyroiditis (0%;n=6) showed no significant difference from normal controls. Furthermore, in patients with idiopathic chronic pancreatitis who had positive results, a lymphocyte proliferative response to the pancreatic antigen was observed in T cells, especially in the CD4+ T cell subpopulation. These results suggest that the pancreatic antigen plays a role in the pathogenesis of a part of idiopathic chronic pancreatitis and Sjögren's syndrome in association with T cell responses and, also, suggest that autoimmunity may be a possible etiological factor in chronic pancreatitis.  相似文献   
36.
涎腺癌肉瘤临床及病理分析   总被引:6,自引:0,他引:6  
目的:探讨涎腺癌肉瘤的临床病理学特点及其鉴别诊断。方法:对3例涎腺癌肉瘤患者的临床资料进行回顾性研究并复习相关文献,对全部病例的组织学标本重新进行镜下观察。结果:涎腺癌肉瘤临床表现常为迅速增大的颜面部肿物并伴疼豢。光匀下组织学观察常可见肉瘤和癌两种成分并存,癌多为鳞状细胞癌和腺癌,肉瘤以骨或软骨肉瘤为主。结论:涎腺癌肉瘤的临床特点与涎腺其他恶性肿瘤较难区别,但涎腺癌肉瘤的恶性程度极高。  相似文献   
37.
Regulation of intracellular free calcium ([Ca2+]i) in single epithelial duct cells of isolated rat and guinea pig pancreatic interlobular ducts by secretin, carbachol and cholecystokinin was studied by microspectrofluorometry using the Ca2+-sensitive, fluorescent probe Fura-2. Rat and guinea pig duct cells exhibited mean resting [Ca2+]i of 84 nM and 61 nM, respectively, which increased by 50%–100% in response to carbachol stimulation, thus demonstrating the presence of physiologically responsive cholinergic receptors in pancreatic ducts of both species. The carbachol-induced increase in [Ca2+]i involved both mobilization of Ca2+ from intracellular stores and stimulation of influx of extracellular Ca2+. In contrast, neither cholecystokinin nor secretin showed reproducible or sizeable increses in [Ca2+]i. Both rat and guinea pig duct cells showed considerable resting Ca2+ permeability. Lowering or raising the extracellular [Ca2+]i led, respectively, to a decrease or increase in the resting [Ca2+]i. Application of Mn2+ resulted in a quenching of the fluorescence signal indicating its entry into the cell. The resting Ca2+ and Mn2+ permeability could be blocked by La3+ suggesting that it is mediated by a Ca2+ channel.  相似文献   
38.
The enzyme aromatase Is Involved In the conversion of androgens to estrogens and in the modulation of various androgenlc and estrogenlc actions. Abnormalities of estrogen metabolism have been postulated to play roles in the development and/or pathophyslology of Sjdgren's syndrome. In the present study, aromatase was immunolocal-ized In 75 cases of Inflammatory disorders of human minor salivary glands of the lower lip. These included cases of primary Sjögren's syndrome (19 cases), of chronic slaladenitis (34 cases) and of mucous extravasation cysts (22 cases), in order to clarify the possible involvement of in situ estrogen production in primary Sjögren's syndrome. Aromatase Immunoreactlvlty was detected In myoepithelial cells of acini and in interstitial cells adjacent to acini and ducts In 13/19 (68%) cases of primary Sjögren's syndrome. In contrast, aromatase expression was detected In only six of 34 (18%) cases of chronic sialadenttis and in seven of 22 (32%) cases of mucous extravasation cyst. These results suggest that Increased aromatase expression in minor salivary glands with primary Sjogren's syndrome in premenopausal women may be involved in the biological features of primary Sjogren's syndrome through the production of estrogens in situ and possibly through the aggravation of the inflammatory reaction.  相似文献   
39.
Cystic duct and Heister's "valves"   总被引:2,自引:0,他引:2  
The anatomy and physiology of the cystic duct have been relatively neglected by anatomists and the function of the spiral mucosal folds or "valves" of Heister, first described in 1732, remains obscure. The gross and microscopic anatomy of the cystic duct is reviewed together with results from laboratory investigations into the function of the cystic duct and its spirally arranged folds. The duct and spiral folds contain muscle fibers responsive to pharmacologic, hormonal, and neural stimuli. There is, however, no convincing evidence of a discrete muscular sphincter within the duct. Although the cystic duct is unlikely to play a major role in gallbladder filling and emptying, it appears to function as more than a passive conduit. Coordinated, graded muscular activity in the cystic duct in response to hormonal and neural stimuli may facilitate gallbladder emptying. The principal function of the internal spiral folds that are found in man and other animals may be to preserve patency of this narrow, tortuous tube rather than to regulate bile flow.  相似文献   
40.
A variety of neoplastic and nonneoplastic lesions of the salivary glands have a predominantly cystic architecture. Fine-needle aspirates of these lesions yield watery or mucoid material, frequently of low cellularity. Such aspirates may be obtained from mucus retention cysts, lymphoepithelial cysts, cystadenomas, Warthin's tumors, cystic pleomorphic adenomas, low-grade mucoepidermoid carcinomas, cystadenocarcinomas, and examples of polycystic disease of the parotid gland. The cellular component within the fluid obtained from these lesions may be exceedingly scant or absent, making cytologic diagnosis difficult and, at times, impossible. We studied a series of 56 cystic lesions of the salivary glands, including 38 Warthin's tumors, 6 benign cysts, 2 lymphoepithelial cysts, 5 low-grade mucoepidermoid carcinomas, 1 cystic pleomorphic adenoma, 2 cystadenomas, and 2 cystadenocarcinomas. Careful attention to the cellular elements present often allowed definitive cytologic diagnosis, with an overall accuracy rate of 84%. The presence of atypical squamous metaplasia in oncocytic lesions was a significant cause of false-positive diagnoses of carcinoma (4 cases, 7%). Aspirates of low-grade mucoepidermoid carcinoma may contain no epithelial cells and result in false-negative diagnoses (1 case, 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