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   4078篇
  免费   141篇
  国内免费   21篇
耳鼻咽喉   128篇
儿科学   124篇
妇产科学   149篇
基础医学   592篇
口腔科学   12篇
临床医学   234篇
内科学   1011篇
皮肤病学   18篇
神经病学   501篇
特种医学   69篇
外科学   395篇
综合类   38篇
预防医学   205篇
眼科学   105篇
药学   435篇
中国医学   21篇
肿瘤学   203篇
  2023年   15篇
  2022年   76篇
  2021年   109篇
  2020年   43篇
  2019年   70篇
  2018年   78篇
  2017年   59篇
  2016年   59篇
  2015年   86篇
  2014年   115篇
  2013年   138篇
  2012年   261篇
  2011年   273篇
  2010年   152篇
  2009年   105篇
  2008年   246篇
  2007年   315篇
  2006年   314篇
  2005年   319篇
  2004年   340篇
  2003年   327篇
  2002年   245篇
  2001年   22篇
  2000年   13篇
  1999年   25篇
  1998年   23篇
  1997年   33篇
  1996年   22篇
  1995年   23篇
  1994年   17篇
  1993年   16篇
  1992年   14篇
  1991年   10篇
  1988年   11篇
  1986年   14篇
  1985年   9篇
  1984年   21篇
  1983年   19篇
  1982年   17篇
  1981年   11篇
  1980年   8篇
  1979年   9篇
  1978年   10篇
  1977年   11篇
  1976年   8篇
  1975年   12篇
  1974年   11篇
  1973年   8篇
  1965年   15篇
  1932年   9篇
排序方式: 共有4240条查询结果,搜索用时 15 毫秒
11.
12.
The results of brain MRI are presented in 22 patients with documented Nijmegen breakage syndrome (NBS), aged from 1 and 9/12 to 20 years. T1-, PD or FLAIR and T2-weighted SE/TSE images in three planes were obtained. Twenty-one patients showed microcephaly. Decreased size of frontal lobes and narrow frontal horns of the lateral ventricles was observed in all cases. In 6 patients agenesis of the posterior part of the corpus callosum was found as well as colpocephaly and temporal horn dilatation. In 2 patients callosal hypoplasia was accompanied by other anomalies: abnormal cerebrospinal fluid spaces. Sinusitis was present in all patients as a result of primary immunodeficiency. As in ataxia teleangiectasia and other breakage syndromes, NBS patients show inherited malignancy susceptibility and hypersensitivity to X and gamma radiation. Because of that computed tomography is contraindicated in these patients and MRI should be the method of choice in diagnostic imaging.  相似文献   
13.
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   
14.
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   
15.
16.
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   
17.
18.
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   
19.
Differential scanning calorimetry, dynamical mechanical, and spin probe measurements were conducted to study relaxation and soft-segment crystallization phenomena in block copoly(ether-ester) elastomers obtained through transesterification and melt polycondensation of dimethyl terephthalate, 1,4-butanediol and poly(ethylene oxide). The elastomers investigated differed both in molecular weight of the poly(ethylene oxide) used as well as in their ratio of hard to soft segments. It was found that a crystallization process of the soft-segment phase does not occur for oligoethers with a molecular weight lower than 1000. The spin probe method can be used to monitor the melting process and additionally it supplies information on the relaxation processes taking place in the amorphous part of the soft phase. Some data on the crystallization of the rigid phase are also given.  相似文献   
20.
The relationship between exposure duration, COHb, blood glucose, pyruvate and lactate and the severity of intoxication was investigated in a group of 39 cases of acute CO poisoning treated in the Clinical Toxicology Center in ód, Poland.On the basis of clinical criteria the patients were classified into cases of mild, moderate, severe and very severe CO poisoning. COHb and carbohydrate metabolites were estimated in venous blood taken immediately after admission of the patient to hospital prior to treatment.The severity of intoxication did not correlate with blood COHb; variation in exposure duration seems to be responsible for this phenomenon. Severe and very severe poisonings were associated with longer exposures and were accompanied by a markedly higher blood lactate level, compared to mild and moderate cases. Blood pyruvate depended less than lactate on the severity of intoxication. Blood glucose depended neither on exposure duration nor on the severity of intoxication.Among the carbohydrate metabolic parameters studied, blood lactate determination can be helpful in the evaluation of the severity of CO poisoning in man.  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