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   475828篇
  免费   33035篇
  国内免费   8619篇
耳鼻咽喉   6223篇
儿科学   9651篇
妇产科学   12136篇
基础医学   64500篇
口腔科学   13530篇
临床医学   43433篇
内科学   93333篇
皮肤病学   9331篇
神经病学   32483篇
特种医学   17166篇
外国民族医学   124篇
外科学   70865篇
综合类   24216篇
现状与发展   24篇
一般理论   83篇
预防医学   23117篇
眼科学   12208篇
药学   41082篇
  57篇
中国医学   6940篇
肿瘤学   36980篇
  2022年   4254篇
  2021年   7410篇
  2020年   5076篇
  2019年   5846篇
  2018年   7888篇
  2017年   6247篇
  2016年   6251篇
  2015年   8235篇
  2014年   11090篇
  2013年   12147篇
  2012年   17272篇
  2011年   18213篇
  2010年   10993篇
  2009年   9512篇
  2008年   14511篇
  2007年   15552篇
  2006年   15374篇
  2005年   14780篇
  2004年   12471篇
  2003年   11779篇
  2002年   11074篇
  2001年   30106篇
  2000年   30844篇
  1999年   25921篇
  1998年   6610篇
  1997年   5641篇
  1996年   5087篇
  1995年   4598篇
  1994年   4047篇
  1993年   3447篇
  1992年   16823篇
  1991年   15446篇
  1990年   14705篇
  1989年   14433篇
  1988年   13023篇
  1987年   12422篇
  1986年   11403篇
  1985年   10549篇
  1984年   7062篇
  1983年   5718篇
  1982年   2783篇
  1979年   5571篇
  1978年   3388篇
  1977年   3015篇
  1975年   2678篇
  1974年   3102篇
  1973年   2892篇
  1972年   2859篇
  1971年   2803篇
  1969年   2566篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
861.
Liver fibrosis was induced in rats by repeated peritoneal injections of carbon tetrachloride (CCl4) over a period of 2-11 weeks. Serum procollagen III peptide (SPIIINP), prolidase (SP) and alanine aminotransferase (SALT) levels were monitored during the period of induction. The extent of fibrosis was semi-quantitatively estimated after collagen staining, and the anti-fibrotic effects of 16,16-dimethyl prostaglandin E2 (DMPGE2), colchicine, and zinc sulphate were studied. SPIIINP and SP were increased the first 2 weeks after CCl4 administration and peaked at 6 weeks. Alterations in SPIIINP and SP correlated well to the semi-quantitative histological score of liver sections during the first 6 weeks, and SP was positively related to SPIIINP throughout the whole induction period. DMPGE2 decreased SPIIINP, SP and SALT significantly in addition to a markedly decreased formation of liver collagens. Colchicine had a similar but less dramatic effect, whereas zinc sulphate only reduced SPIIINP without influencing liver damage. In conclusion SPIIINP seems to be a valuable indicator of liver fibrogenesis, and SP may play a limited role in indicating accelerated collagen metabolism in the liver. DMPGE2 obviously inhibited the production of collagens induced by CCl4. Colchicine also had an apparent effect on liver fibrosis, whereas zinc sulphate merely seemed to postpone it.  相似文献   
862.
本文分析了36例原发性甲状旁腺功能亢进的骨骼X线改变,认为主要的骨病征象可概括为指骨的骨膜下骨吸收、颅骨的磨玻璃样及颗粒状改变、骨皮质下的囊肿样改变和棕色瘤,骨的突起或肌腱韧带附着处的骨吸收,以及软骨下骨吸收。骨皮质下囊变的征象对鉴别诊断很有帮助。作者认为骨质疏松和反复泌尿系结石可提示甲状旁腺功能亢进的早期表现,应及时检查血钙磷以确诊。  相似文献   
863.
We describe a case of aortopulmonary fistula in which the correct diagnosis was made by transthoracic echocardiography. The transesophageal approach, because of severe aortic dilatation, failed to provide the correct diagnosis, underlining the importance of complete transthoracic and transesophageal studies in the evaluation of aortic aneurysms.  相似文献   
864.
The pulmonary lesions were studied in 24 autopsy cases of Japanese patients with AIDS. The major pathological findings were opportunistic infections, which were the major clinical symptoms in some patients. The pathogens identified were as follows; Pneumocystis carinii (PC) in 10, cytomegalovirus (CMV) in 14, atypical mycobacterium in 5, cryptococcus in 2, candida in 2, and nocardia in 1. PC pneumonia was prominent in 8 cases and was the cause of death. In such patients, the lung were heavy and appeared parenchymatous. Histological examination revealed numerous protozoa in the foamy material in the alveolar spaces, associated with swelling of the alveolar lining cells and edematous thickening of the alveolar septa. In some cases, only hyaline membrane formation was prominent without foamy material in the alveolar spaces. Immunostaining with anti-PC monoclonal antibody or in-situ hybridization with oligopeptide demonstrated pathogens in the hyaline membranes. Many cases with PC pneumonia had concomitant opportunistic infections such as CMV, Herpes simplex virus, and atypical mycobacterium. Extrapulmonary infection of PC was seen in only one case. CMV infection was found in 14 cases; 7 had innumerable inclusion bodies, and in some cases the lesions were most prominent around the bronchioles. Of the 5 cases of atypical mycobacterial infection, 2 were caused by M. kansaii (MK) and 3 by M. avium intracellulare (MAI). Both lesions of MK infection showed necrosis and cavitation. One of three cases of MAI infection showed cavitation. Around the cavitary lesions, numerous cytomegalic inclusion bodies were identified in the mesenchymal cells, which may have been the cause of necrosis and cavitation of the lesions. MAI infection was systemic and pronounced in the lymph nodes, spleen, and intestinal mucosa. Neoplastic lesions comprised 2 cases of Kaposi's sarcoma and 4 of extranodal non-Hodgkin lymphoma in other organs. Lung involvement was seen in only one case of Kaposi's sarcoma although very small in size. The lesion was situated along the pulmonary vein and appeared hemorrhagic macroscopically. Pulmonary lesions in AIDS are complicated, and many of opportunistic pathogens were identified in single patients.  相似文献   
865.
Bone marrow (BM) cells from two transgenic mice carrying the human c-myc oncogene were separately harvested, and each sample was injected into 25 lethally irradiated mice. We observed the contribution of the myc gene to the occurrence of hemopoietic neoplasms in the BM-repopulated mice, establishing a new experimental system for analyzing oncogene expression in the hemopoietic system in vivo. The hybrid gene that was transferred into the original transgenic mice was a combination of the human c-myc gene with a regulatory unit consisting of a murine immunoglobulin-heavy chain with an SV40 early-T promoter gene (Ig/Tp-myc). Among the transgenic lines, the tested BM cells were chosen from two lines that had been low-prone in leukemia; in these lines hemopoietic neoplasms did not appear for greater than or equal 200 days after birth. Lethally irradiated controls received BM cells from litters of transgenic mice that did not carry c-myc. The lifetime incidence of hemopoietic neoplasms was 94% and 91% in the two groups of mice repopulated with myc+ BM. By contrast, only 15% of control mice with myc- BM developed hemopoietic lesions. The incidence of hemopoietic malignancies combined with nonthymic lymphomas and myeloma cases (88% and 65%) was higher in the repopulated mice than the incidence of pre-B cell lymphomas in the original transgenic lines (56%). Thirty-two of the 40 myc+ mice that were examined showed the presence of the transferred gene in either the normal hemopoietic tissue or in the hemopoietic neoplasm. Furthermore, 18 of 22 hemopoietic neoplasms studied by Northern hybridization expressed mRNA from the transgenic gene; in other four neoplasms, expression was weak or absent.  相似文献   
866.
We encountered a rare case of hypersensitivity pneumonitis associated with bilateral hilar lymphadenopathy (BHL). The patient was a 53-year-old male, who developed dry cough and shortness of breath when using a humidifier since 1982. He was admitted to our hospital for further evaluation in 1987. Chest X-ray films showed BHL and ground glass appearance in the bilateral lung fields. Pulmonary function test indicated disturbance of diffusing capacity. Transbronchial lung biopsy revealed interstitial pneumonitis, and lymph node biopsy by mediastinoscopy showed lymphoid sinus histiocytosis without noncaseating granuloma. Provocation test using the humidifier was positive, and the diagnosis of humidifier lung with BHL was made.  相似文献   
867.
Eosinophilic activation in cystic fibrosis.   总被引:1,自引:1,他引:0       下载免费PDF全文
D Y Koller  M Gtz  I Eichler    R Urbanek 《Thorax》1994,49(5):496-499
BACKGROUND--The neutrophil is a potent contributor to pulmonary destruction in cystic fibrosis. Since eosinophils also possess destructive potential the involvement of eosinophils in cystic fibrosis has been investigated. METHODS--Eosinophil numbers and levels of eosinophil cationic protein (ECP), a marker of eosinophil activation, were determined in the serum of 42 patients with cystic fibrosis and in the sputum of 10 of them. To determine neutrophil activation levels of myeloperoxidase (MPO) were also measured. RESULTS--In cystic fibrosis increased serum levels of ECP were detected compared with healthy non-atopic subjects. Serum ECP levels were not related to the peripheral blood eosinophil count. A strong correlation with ECP concentrations in sputum indicated that the level of ECP in serum was representative of its pulmonary level. Levels of MPO were also increased in cystic fibrosis. A strong correlation was found between MPO and pulmonary function. In addition, ECP was related to arterial oxygen and carbon dioxide tensions. Antibiotic treatment reduced neutrophil activation without effect on ECP levels. CONCLUSIONS--Until now Pseudomonas aeruginosa and neutrophils were held to be primarily responsible for progressive tissue damage in cystic fibrosis. The results of this study suggest that eosinophils might also participate in such pulmonary destruction.  相似文献   
868.
Marijuana, and specifically its psychoactive component, THC, can up or down regulate lymphocyte proliferation in murine spleen cells depending in part on the method used to stimulate the cells. This study identifies a difference in THC induced disregulation using cells derived from two different secondary lymphoid organs, the spleen and the lymph node. It was found that THC treatment of mitogen (concanavalin A or phytohemagglutinin) stimulated cells derived from either organ resulted in suppression of the proliferative response. In contrast, spleen cells stimulated with anti-CD3 antibody and treated with low doses of THC displayed an enhanced proliferation whereas the response in lymph nodes did not change. The cell type involved with this THC immunoenhancement in spleen cells was found to be the Ly2 cell. Further differences in the THC modulation of Ly2 spleen cells as compared to lymph node cells were noted following stimulation with PHA. Proliferation of Ly2 cells of splenic origin was inhibited with low doses of THC whereas the Ly2 cells of lymph node origin were more resistant to this drug induced suppression. This study, therefore, demonstrates differences in the immunomodulatory capability of THC dependent upon the organ source of the lymphocytes.  相似文献   
869.
A 40-year-old man who lived in a wooden house built 30 years ago presented with complaints of fever, dry cough and dyspnea. Chest X-ray findings showed interstitial shadows throughout bilateral lung fields. After admission, high-dose administration of 3000 mg of methylprednisolone was performed because of deterioration of chest X-ray shadows and symptoms. In a week, clinical data and symptoms improved. Findings of BAL fluid on admission revealed a relative increase of lymphocytes, neutrophils and mast cells, and pathological findings of transbronchial lung biopsy revealed non-caseous granulation and alveolitis. Precipitating antibodies and indirect fluorescent antibodies against Trichosporon cutaneum and Cryptococcus neoformans had positive reactions and T. cutaneum was isolated and identified from the patient's house. A diagnosis of summer-type hypersensitivity pneumonitis was made according to the criteria advocated by Ando et al. This seemed to be a rare case of summer-type hypersensitivity pneumonitis prolonged after isolation from his normal living environment, successfully treated by high-dose administration of steroid.  相似文献   
870.
The classical from of Wegener's granulomatosis (WG) is a necrotizing granulomatous angiitis that involves the upper and lower airways, and kidneys. A limited form of WG is characterized by pulmonary lesions identical to those of classical form WG without renal involvement. The authors report a case of limited form WG. A 58-year-old Japanese woman was admitted because of an abnormal pulmonary shadow. Pathological examination revealed granulomatous angiitis consistent with WG. No other organ involvement was found. The pulmonary shadow improved with cyclophosphamide therapy. The patient is now well and without evidence of exacerbation of the disease 18 month after the discharge.  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