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   6937篇
  免费   335篇
  国内免费   31篇
耳鼻咽喉   78篇
儿科学   125篇
妇产科学   80篇
基础医学   948篇
口腔科学   115篇
临床医学   427篇
内科学   1691篇
皮肤病学   70篇
神经病学   610篇
特种医学   243篇
外科学   1145篇
综合类   21篇
预防医学   228篇
眼科学   99篇
药学   597篇
中国医学   32篇
肿瘤学   794篇
  2023年   14篇
  2022年   19篇
  2021年   79篇
  2020年   35篇
  2019年   59篇
  2018年   72篇
  2017年   77篇
  2016年   81篇
  2015年   83篇
  2014年   91篇
  2013年   162篇
  2012年   221篇
  2011年   252篇
  2010年   170篇
  2009年   146篇
  2008年   245篇
  2007年   312篇
  2006年   313篇
  2005年   324篇
  2004年   298篇
  2003年   334篇
  2002年   334篇
  2001年   312篇
  2000年   333篇
  1999年   332篇
  1998年   96篇
  1997年   85篇
  1996年   76篇
  1995年   79篇
  1994年   86篇
  1993年   81篇
  1992年   231篇
  1991年   243篇
  1990年   215篇
  1989年   200篇
  1988年   199篇
  1987年   171篇
  1986年   182篇
  1985年   144篇
  1984年   94篇
  1983年   76篇
  1982年   43篇
  1981年   29篇
  1980年   27篇
  1979年   77篇
  1978年   36篇
  1977年   25篇
  1976年   22篇
  1975年   11篇
  1969年   10篇
排序方式: 共有7303条查询结果,搜索用时 31 毫秒
71.
Intrahepatic biliary tree with either florid duct lesions or a moderate to severe degree of the duct loss in four livers with chronic hepatic diseases other than primary biliary cirrhosis were studied with histometric and serial section observations. Florid duct lesions, distributed segmentally in the liver, were found in one case with incomplete septal cirrhosis and one case with idiopathic portal hypertension. The florid duct lesions including marked plasma cell infiltration and occasional periductal granulomas, were not associated with any bile duct loss in the two cases. The duct lesions were reversible in one case during a long clinical course. On the other hand, a moderate to severe bile duct loss with biliary epithelial degeneration and necrosis was associated with no or little periductal inflammatory cell infiltration in one other case with chronic intrahepatic cholestasis, probably drug-induced, and in one case with idiopathic portal hypertension. Although florid duct lesions and bile duct loss were important diagnostic features of primary biliary cirrhosis, one of them was observed to develop independently in severely diseased livers, not consistent with a diagnosis of primary biliary cirrhosis, sclerosing cholangitis or intrahepatic bile duct paucity syndrome.  相似文献   
72.
Strains of 10 black-pigmented Bacteroides species were serologically characterized using absorbed and unabsorbed rabbit antisera. An agglutination test using intact cells or heated cells (100 degrees C for 60 min) from each species and unabsorbed antisera revealed only homologous reactions with little or no reactivity in heterologous assays. Immunodiffusion tests using sonicated antigen demonstrated that Bacteroides gingivalis, B. endodontalis, B. asaccharolyticus, B. macacae, and B. levii are antigenically distinct. Strains of B. gingivalis, B. endodontalis, and B. asaccharolyticus were also clearly identified by the indirect immunofluorescent antibody method. B. intermedius, B. corporis, B. loescheii, B. melaninogenicus, and B. denticola possessed common antigens; however, species-specific antigens detectable with immunoabsorbed antisera were also demonstrated. B. intermedius strains isolated from the human oral cavity included at least two serogroups. In each black-pigmented Bacteroides species, lipopolysaccharide constituted one of the species-specific antigens.  相似文献   
73.
We analyzed the relationships between levels of antibody specific for merozoite surface glycoprotein-1 (MSP1) of Plasmodium falciparum and clinical manifestations in humans. We prepared recombinant MSP1 proteins representing block 3 (M3), block 6 (M6), blocks 1–6 (M1/6), and block 17. When we divided the slide-positive individuals in Guadalcanal into symptomatic and asymptomatic groups, the former group showed lower IgG levels against M6 and block 17, but not against M3, than did the asymptomatic group (P < 0.01). The possibility of nonspecific suppression was unlikely, given that the levels of antibody against poliomyelitis virus observed in the two groups were almost the same. Among the IgG subclasses tested, production of cytophilic IgG3 seemed to be dominant. When we analyzed epitopes recognized by antibodies against block 17, a peptide (SSSNFLGIS) was preferentially recognized by sera from asymptomatic individuals. These results suggest that clinical symptoms occurring during falciparum malaria seem to be associated with the development of levels of antibody against particular epitopes on MSP1, which is under the control of an immunoregulatory mechanism. Received: 1 October 1999 / Accepted: 21 October 1999  相似文献   
74.
We report an autopsy case of mixed ductal-endocrine carcinoma of the pancreas presenting as gastrinoma with Zollinger-Ellison syndrome. A 38-year-old Japanese male was found to have Zollinger-Ellison syndrome and pancreatic gastrinoma, and gastrectomy and resection of the pancreatic tumor were performed. However, hypergastrinemia persisted, and the patient died of disseminated carcinomatosis at 62 years of age, 24 years after the onset of Zollinger-Ellison syndrome. At autopsy, the main tumor was present in the residual pancreas, and metastases were noted in many organs. In the pancreas and other organs, ductal and endocrine carcinoma areas were mixed and there was a gradual transition between the two. No acinar differentiation was noted. The ductal elements were positive for mucins and carcinoembryonic antigen but negative for neuroendocrine markers, while endocrine elements were positive for chromogranin A and synaptophysin and to a lesser extent for gastrin, but negative for mucins and carcinoembryonic antigen. The ductal elements comprised about 30% of the tumor cells, and endocrine elements 70%. According to the revised World Health Organization classification, our case was diagnosed as mixed ductal-endocrine carcinoma. Our case is rare because the tumor manifested as gastrinoma with Zollinger-Ellison syndrome and the patient survived for 24 years. To the best of our knowledge, no such case has been reported. Our case suggests that pancreatic endocrine tumors may evolve into mixed ductal-endocrine carcinomas. Received: 14 April 1999 / Accepted: 7 July 1999  相似文献   
75.
Tumor necrosis factor alpha (TNFα) in activated monocytes exerts cytotoxic activity and has a variety of other biological effects. We isolated a polymorphic dinucleotide (CA) repeat sequence from a genomic clone containing the gene located at 6p21.3. High heterozygosity (0.80) makes this polymorphism a useful marker in the genetic study of disorders affecting immunological response and cell differentiation. Received: June 2, 1998 / Accepted: June 24, 1998  相似文献   
76.
Two adolescent patients suffering from persistent sleep-wake schedule disorders appear to have responded to treatment with vitamin B12 (methylcobalamin). A 15-year-old girl with delayed sleep phase syndrome (DSPS) and a 17-year-old boy with hypernychthemeral syndrome complained of not being able to attend school despite many trials of medication. The improvement of the sleep-wake rhythm disorders appeared immediately after the administration of high doses (3,000 micrograms/day) of methylcobalamin. Neither patient showed any laboratory or clinical evidence of vitamin B12 deficiency or hypothyroidism (which can cause B12 deficiency). Serum concentrations of vitamin B12 during treatment were in the high range of normal or above normal. The duration of the sleep period of the DSPS patient decreased gradually from 10 hours to 7 hours, and the time of sleep onset advanced from 2 a.m. to midnight. The period of the sleep-wake cycle of the hypernychthemeral patient was 24.6 hours before treatment and 24.0 hours after treatment. The relationship between the circadian basis of these disorders and vitamin B12 and its metabolites is discussed.  相似文献   
77.
An autopsy case of malignant midline reticulosis (MMR) is reported. The patient, a 42-year-old Japanese male, died after a clinical course of 22 months. Autopsy revealed extensive infiltration of generalized organs by the tumor cells, suggesting that the disease was highly malignant in nature. Staining with monoclonal antibodies against T-cell surface antigens Leu 4 on frozen sections and UCHL1 on paraffin-embedded sections enabled us to examine the phenotype of the tumor cells with good morphological preservation and to verify the T cell nature of the tumor.  相似文献   
78.
BACKGROUND: In Asian countries, there is no epidemiological report on seasonal affective disorder (SAD) in different age groups and different geographic regions surveyed at the same time. The aim of this study was to estimate the prevalence rates of SAD and risk factors for SAD in adults and high-school students, with special reference to the difference of winter SAD between northern and southern regions in Japan. METHODS: A total of 3237 high-school students and 4858 workers living in Japan (31.3-43.5 degrees N) responded to this epidemiological survey using Japanese version of the Seasonal Pattern Assessment Questionnaire (SPAQ). RESULTS: The overall prevalence rates of winter SAD (subsyndromal winter SAD) and summer SAD (subsyndromal summer SAD) in high-school students were 0.91(2.21) and 0.81(2.57)%, respectively. In workers, these rates were 0.45(1.16) and 0.43(0.71)%, respectively. Although no regional difference was noted in high-school students with winter seasonal type, the estimated odds ratio of this type for northern workers was nearly 3-fold higher than the southern counterparts. The prevalence rates of each seasonal type were not significantly different between two sexes in both age groups. No clear dependence on latitude was seen with regard to summer SAD in both age groups. LIMITATIONS: The effect of climate on SAD could not be entirely excluded from geophysical factor as indexed by latitude. CONCLUSIONS: SAD was less common in adults than in high-school students. While latitude was a major determinant of winter type in adults, socio-cultural factors or other contributing factors might affect the development of this type in high-school students.  相似文献   
79.
80.
Although there are at least 13 interferon-alpha (IFN-alpha) subtypes in humans, interactions between the subtypes remain unknown. To understand IFN-alpha interactions, we examined the antiproliferative activities and the receptor binding affinities of different combinations of IFN-alpha2 and IFN-alpha8 using six renal cell carcinoma (RCC) cell lines. Although IFN-alpha8 was the more potent subtype, synergistic and antagonistic antiproliferative effects were also observed in certain combinations of IFN-alpha2 and IFN-alpha8. To analyze the interactions between IFN-alpha2 and IFN-alpha8, the receptor-binding kinetics of different combinations of IFN-alpha2 and IFN- alpha8 to the IFN-alpha receptors, IFNAR-1 or IFNAR-2, were measured using a surface plasmon resonance-based biosensor. Unexpectedly, the receptor binding kinetics to IFNAR-2 but not to IFNAR-1 were mutually related to antiproliferative activity and increase in the binding speed (K(a)) for IFNAR-2. Moreover, we observed the increased fluorescence intensity (FI) of biotin-labeled IFN-alpha8 to IFNAR-2 by receptor binding inhibition assay with unlabeled IFN-alpha2 but not the other combinations. These findings indicate that the binding manner of IFN-alpha8 for IFNAR-2 is different from that of IFN-alpha2, suggesting that binding of IFN-alpha8 rather than binding of IFN-alpha2 to IFNAR-2 leads to activation and subsequent antiproliferative activity despite the same antiviral activity in RCC.  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