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   4046篇
  免费   147篇
  国内免费   21篇
耳鼻咽喉   128篇
儿科学   126篇
妇产科学   157篇
基础医学   593篇
口腔科学   12篇
临床医学   229篇
内科学   994篇
皮肤病学   19篇
神经病学   496篇
特种医学   67篇
外科学   395篇
综合类   38篇
预防医学   203篇
眼科学   105篇
药学   428篇
中国医学   21篇
肿瘤学   203篇
  2023年   11篇
  2022年   55篇
  2021年   110篇
  2020年   43篇
  2019年   70篇
  2018年   78篇
  2017年   59篇
  2016年   59篇
  2015年   88篇
  2014年   115篇
  2013年   138篇
  2012年   262篇
  2011年   274篇
  2010年   152篇
  2009年   106篇
  2008年   246篇
  2007年   315篇
  2006年   314篇
  2005年   319篇
  2004年   341篇
  2003年   327篇
  2002年   244篇
  2001年   22篇
  2000年   14篇
  1999年   22篇
  1998年   23篇
  1997年   33篇
  1996年   22篇
  1995年   23篇
  1994年   16篇
  1993年   16篇
  1992年   14篇
  1991年   9篇
  1988年   11篇
  1986年   12篇
  1985年   9篇
  1984年   21篇
  1983年   19篇
  1982年   16篇
  1981年   11篇
  1980年   8篇
  1979年   10篇
  1978年   10篇
  1977年   10篇
  1975年   12篇
  1974年   11篇
  1973年   8篇
  1972年   7篇
  1965年   15篇
  1932年   9篇
排序方式: 共有4214条查询结果,搜索用时 15 毫秒
31.
The physicochemical properties of mitochondria in liver tissue obtained from rats given 32% ethanol, 32% propanol or 6.9% butanol in drinking water for up to 3 months were investigated using differential scanning calo-rimetry and fluorescence polarization measurements. The results obtained were as follows: 1) Phospholipids extracted from mitochondria showed increases in the relative amounts of phosphatidylcholine, phosphatidylinositol and phosphatidylserine, and a decrease in the relative amount of phosphatidylethanolamine. An increase in the unsatu-rated/saturated fatty acid ratio of phospholipids was also observed. 2) Elevation of the thermotropic lipid phase transition temperature with a decrease in the enthalpy value (δ H ) was revealed by differential scanning calo-rimetry. 3) The elevation of the lipid phase transition temperature was detected also by fluorescence polarization measurements using 1,6 diphenyl 1, 3, 5 hexatriene (DPH) as a probe. Elevation of mitochondrial membrane fluidity was found in some of the experimental animals, but most showed no changes in comparison with the control. A possible role of membrane fusion in the mechanism of formation of ethanol-, propanol- and butanol induced hepatic megamitochondria is discussed on the basis of these results. Acta Pathol Jpn 42: 549–557, 1992.  相似文献   
32.
Between 1984 and 2000 in the Thoracic Surgery Centre pneumonectomies were performed in 947 patients. Postpneumonectomy empyema (PE) occurred in 67 (7%) patients. The aim of this paper were: analysis the reasons of postpneumonectomy empyema appearance, defined bacterial flora, clinical course and optimal management. The causes of PE were: pleural cavity haematoma (20 patients-29.8%), wound suppuration (18 patients-26.8%), bronchial fistula (31 patients-46.2%). These complications appeared singly or together in 49 (73.1%) patients. In 2 (3.0%) patients a long treatment in the Intensive Care Unit because of postoperative shock was the cause of infection. In 3 (4.5%) cases the cause of empyema was associated with infection during the operation. In 13(19.4%) cases the cause of empyema was not established. In 55 patients infections of pleural cavities were diagnosed in the first 8 weeks after operations. In 12 patients empyemas were established later. 12 (17.9%) patients died during the analyzed 1 year period after operation. In 18 (26.9%) patients infections were caused by only one bacterial strain and in 49 (73.1%) by two or three bacterial strains. The different methods of treatment (thoracentesis, drainage, operation) depending on general condition of patient were done.  相似文献   
33.
34.
Zusammenfassung Das Vacciniavirus vermehrt sich schnell in den Organen von 1 tägigen Ratten, und die Tiere verenden am 2. oder 3. Tag nach der Infektion. In den Organen von 7 tägigen Ratten kann sich das Virus anfangs vermehren, später wird es aber eliminiert und die Tiere überleben. Bei 15tägigen Ratten wird das Virus eliminiert und die Tiere verenden nicht.Eintägige Ratten, die vor der Infektion Makrophagen erwachsener Tiere erhalten haben, kamen nicht ad exitum. Die Makrophagen von erwachsenen Ratten haben im Gegensatz zu Makrophagen von jungen Tieren die Fähigkeit, das phagozytierte Virus zu inaktivieren.Es wird daraus der Schluß gezogen, daß für die hohe Empfindlichkeit junger Ratten gegenüber Vacciniavirusinfektionen die funktionelle Unreife ihrer Makrophagen verantwortlich ist.
The role of macrophages in the pathogenicity of vaccinia virus for young rats
Summary Vaccinia viruses grew rapidly in organs of 1-day-old rats, and the animals died 2 or 3 days after infection. In the organs of 7-day-old rats the viruses replicated initially, but were later eliminated and the animals survived. The 15-day-old rats were capable of eliminating the viruses completely and did not die. When macrophages of adult animals were transferred to 1-day-old rats before infection the rats did not die. The macrophages of adult rats destroyed phagocytized viruses while those of young animals did not.The results suggest that this susceptibility of young rats to vaccinia virus infection is due to the functionally immature state of their macrophages.
  相似文献   
35.
36.
The paper investigates the conformational stability of bovine serum albumin (BSA) and fibrinogen during 24-h incubation in turn with a linear silicone polymer (polydimethylsiloxane (PDMS)), with linear silicone oligomers (hexamethyldisiloxane and octamethyltrisiloxane) and with cyclic silicone oligomers (octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5)). Ten-fold and 100-fold excesses of siloxanes with respect to the proteins were used. Using fluorescence spectroscopy of tryptophan located in the domain of proteins and fluorescence of 8-anilino-1-naphthalenesulfonic acid (1,8-ANS), which interacts with hydrophobic domains of proteins, changes in the tertiary structure of the protein were recorded. The results demonstrated that BSA does not change its native form during 24-h incubation with siloxanes. In contrast, the tertiary structure of fibrinogen was found to be altered by both short-chain linear siloxanes: (hexamethyldisiloxane and octamethyltrisiloxane) and long-chain PDMS. The changes can be observed only at a 100-fold excess of siloxanes with respect to the protein. No conformational changes in fibrinogen exposed to cyclic siloxanes were observed.  相似文献   
37.
The influence of acetylsalicylic acid (ASA) on skin response to intradermal injection of compound 48/80 and histamine was studied in order to determine whether ASA elicits any abnormalities also in the skin of asthmatics reacting with bronchoconstriction to ingestion of this drug.
The applied ASA dose (mean dose 150 mg) elicited bronchoconstriction in all 16 patients with asthma and ASA sensitivity (mean fall of FEV1 34%) and increased the weal response to compound 48/80 to about 51% (P>0.05) as compared with the response before the ASA-challenge, In asthmatic persons without ASA sensitivity a 150 mg ASA dose did not influence the skin response to any of the reagents. On the other hand, a 600 mg dose decreased skin response to histamine and compound 48/80 in persons without ASA intolerance, although the decrease was statistically significant only in the flare after compound 48/80 (P>0.05).
The authors believe that additional local defect is needed to reveal sensitivity to ASA in the skill of ASA-sensitive asthmatics, just as bronchial hyperreactivity is indispensible for revealing the action of ASA in the bronchi.  相似文献   
38.
Bronchoalveolar lavage (BAL) or induced sputum (IS) techniques may provide leukocytes for the evaluation of airway inflammatory response in bronchial asthma. The aim of the present study was to compare features of leukocyte populations obtained by the two different methods regarding the cell types and their activity in patients with bronchial asthma. The nitric oxide (NO) level released from the cells was measured as a marker of their activity. Pulmonary leukocytes were obtained from the BAL and IS of 11 asthmatic patients in stable condition at the time of the study. The BAL and IS leukocyte populations varied in cell count and NO production. Macrophages were the predominant leukocyte population in BAL (median (Me) = 83.0%, range 67.9-88.4%), whereas sputum sediments were found to consist mainly of neutrophils (Me = 55.7%, range 29.0-64.9%). The IS leukocytes released much more NO (p = 0.0022) than the BAL leukocytes. In spite of these quantitative differences, a similar pattern of NO production was observed in BAL and in IS cells. Both BAL and IS leukocyte populations produced almost the same amounts of NO before and after lipopolysaccharide stimulation (p = 0.9063, p = 0.4801, respectively). Furthermore, a slight positive correlation Spearman's rank (RS) = 0.5578, p = 0.0594) was noticed between the neutrophil percentages and NO levels produced by BAL cells, whereas in IS a statistically significant correlation between the percentage of neutrophils and the levels of NO (RS = 0.6643, p = 0.0184) was observed. In conclusion, the BAL and IS leukocyte populations are different in cell type, their size and activity. Depending on the asthma severity and the type of cells needed in a study, either BAL or IS specimens may be chosen as a source of pulmonary leukocytes. The use of IS as a noninvasive technique is supposed to be potential value particularly in the study of the airway inflammatory response mediated mainly by neutrophils, i.e. during and/or after exacerbation of the disease. Based on our results, a possible contribution of neutrophils in the production of NO in the airways of asthmatic patients can be proposed apart from other cells such as macrophages.  相似文献   
39.
Inflammatory myofibroblastic tumours (IMTs) were initially considered to be benign reactive processes, but cases with an unfavourable outcome have been reported. Moreover, clonal genetic alterations have recently been published in some cases, suggesting that IMT may represent a malignant neoplastic entity. This paper reports a case of IMT that developed in the mammary gland, an unusual site. The histological picture was characterized by a proliferation of spindle cells with little cellular atypia and rare mitoses, associated with a polymorphous inflammatory infiltrate. Their immunophenotype, characterized by the expression of vimentin, smooth muscle actin, and cytokeratins, corresponded to that of myofibroblasts. Cytogenetic analysis revealed the clonal nature of the lesion. The modal karyotype was 48, X, ins(2;X)(q34;p21.2p22.2), +7, del(9)(p23), +19. Including the present observation, a 9p deletion has now been found in three cases of IMT. These observations show that IMT may be a clonal neoplasm, even in sites different from deep soft tissues.  相似文献   
40.
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