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   837篇
  免费   131篇
  国内免费   16篇
耳鼻咽喉   19篇
儿科学   34篇
妇产科学   21篇
基础医学   110篇
口腔科学   13篇
临床医学   103篇
内科学   222篇
皮肤病学   13篇
神经病学   49篇
特种医学   99篇
外科学   80篇
综合类   21篇
预防医学   39篇
眼科学   6篇
药学   77篇
中国医学   2篇
肿瘤学   76篇
  2021年   11篇
  2020年   16篇
  2019年   16篇
  2018年   22篇
  2017年   22篇
  2016年   22篇
  2015年   32篇
  2014年   31篇
  2013年   44篇
  2012年   32篇
  2011年   33篇
  2010年   27篇
  2009年   38篇
  2008年   26篇
  2007年   41篇
  2006年   41篇
  2005年   34篇
  2004年   27篇
  2003年   27篇
  2002年   23篇
  2001年   11篇
  2000年   18篇
  1999年   19篇
  1998年   26篇
  1997年   24篇
  1996年   25篇
  1995年   26篇
  1994年   18篇
  1993年   11篇
  1992年   13篇
  1991年   6篇
  1990年   10篇
  1989年   23篇
  1988年   15篇
  1987年   24篇
  1986年   17篇
  1985年   15篇
  1984年   12篇
  1983年   14篇
  1982年   9篇
  1981年   6篇
  1980年   11篇
  1979年   6篇
  1978年   6篇
  1976年   8篇
  1975年   8篇
  1974年   4篇
  1973年   5篇
  1971年   4篇
  1970年   4篇
排序方式: 共有984条查询结果,搜索用时 15 毫秒
1.
T lymphocytes play a fundamental role in the initiation and regulation of chronic inflammatory responses in patients with asthma. CD69 is an early marker of T‐cell activation. The levels of intercellular adhesion molecule‐1 (ICAM‐1, CD54) and L ‐selectin have been reported to increase in patients with allergic diseases and asthma. The present study was therefore undertaken to investigate the expression of CD69, CD54, and L ‐selectin by T lymphocytes of children with asthma, before and after immunotherapy. Eighteen children newly diagnosed with asthma, 11 good and nine poor responders to immunotherapy, and 16 normal subjects, were enrolled in this study. The percentages of CD69+, CD54+, and CD62L+ cells in T lymphocytes were measured by using flow cytometry. The levels of CD69, CD54, and CD62L in serum and culture supernatants were determined by using enzyme‐linked immunosorbent assay (ELISA). The expression of CD69 and CD54 on CD3+ T lymphocytes was significantly higher in children with asthma than in control patients. All the patient groups expressed (spontaneously and following stimulation with phorbol myristate acetate and ionomycin together with mite‐extract proteins) greater amounts of CD69 and CD54 than did control subjects. With long‐term immunotherapy, the percentages of CD69+ and CD54+ T lymphocytes were significantly lower in patients with a good response to immunotherapy. Our results also showed significantly lower serum L ‐selectin levels following immunotherapy. In conclusion, successful immunotherapy resulted in decreased expression and production of CD69 and CD54. These results may explain, in part, the clinical efficacy of immunotherapy.  相似文献   
2.
硫酸多糖对体外人脐静脉内皮细胞损伤的保护作用   总被引:8,自引:1,他引:7  
研究表明,硫酸多糖体外对多聚阳离子和氧自由基损伤的人脐静脉内皮细胞有保护作用。肝素、硫酸软骨素A抗多聚阳离子损伤作用比同浓度低分子肝素和甘糖酯强。肝素、硫酸软骨素A、甘糖酯抗氧自由基损伤作用优于同浓度低分子肝素。结果显示硫酸多糖有保护血管内皮的作用,其作用可能与所带阴离子基团有关。  相似文献   
3.
4.
采自贵州省猪尾鼠的吸虱具有特殊的形态。李氏欣奇虱独自成为一科。双叶盲鼠虱隶拟血虱科。拟血虱科中的拟血虱属和钩板虱属均寄生于鼹科,裂虱属和盲鼠虱属则寄生于睡鼠科和刺山鼠科。后者曾被置于睡鼠科。研究食虫目动物的吸虱将可能对吸虱与其宿主动物的偕同进化提供更多的证据。  相似文献   
5.
BACKGROUND: Studies of outpatient clinical training in AIDS care have shown positive effects on residents' knowledge, attitudes and intentions. In this study, residents' knowledge, attitudes and intentions regarding the care of HIV-infected patients were used as outcome measures to evaluate the effectiveness of a 1-month residency training in an AIDS inpatient unit. METHODS: From April 2000 through April 2001, 33 internal medicine residents completed pretest-posttest questionnaires evaluating changes in their knowledge, attitudes and intention to care for HIV-infected patients. Of these 33 residents, 25 participated in a posttest interview, reflecting on their learning experience during the 1-month clinical rotation. RESULTS: At the posttest, residents were significantly more accurate in assessing HIV-associated risk (p < 0.001), and were significantly more knowledgeable about the necessary protective equipment to prevent HIV transmission (p < 0.01). Residents were significantly less concerned about the risk of infection (p < 0.01) and interpersonal concerns (p < 0.05). Residents' reluctance to care for HIV-infected patients was significantly lower (p < 0.05), as was their tendency to avoid invasive procedures or treatment of HIV-infected patients (p < 0.001). Residents designated after their training were more likely to practice universal precautions and less likely to be afraid and to stereotype HIV-infected patients. They also reported gaining insight into HIV diseases and patients' multifaceted needs, and appreciating the importance of teamwork in AIDS care. CONCLUSION: A 1-month AIDS residency training can effectively enhance residents' HIV-related knowledge, attitudes and intention to care for patients infected with HIV.  相似文献   
6.
(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine, HPMPC, and two HPMPC-related nucleoside analogs, (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine, HPMPA, and (2-phosphonylmethoxyethyl)guanine, PMEG, were evaluated for their antiviral activities against guinea pig cytomegalovirus (GPCMV) infection in guinea pig embryo (GPE) cells and human cytomegalovirus (HCMV) infection in human diploid fibroblast (MRC-5) cells. DHPG, 9-(1,3-dihydroxy-2-propoxymethyl)guanine, was used for comparison. The antiviral activity of HPMPC against GPCMV infection in vivo and its toxicity to Hartley guinea pigs were also evaluated. The 50% antiviral effective doses (ED50) of HPMPC, HPMPA, PMEG and DHPG against GPCMV infection in GPE cells were 0.22, 1.4, 0.07 and 62 microM, respectively; and against HCMV infection in MRC-5 cells, the ED50s were 0.51, 0.72, 0.01 and 17.5 microM, respectively. Their cytotoxic doses (CyD50) in GPE replicating cells were 84, 35, 1.4 and 700 microM, respectively and in MRC-5 cells were approximately 114, 31, 0.86 and 750 microM, respectively. Based on their calculated therapeutic indexes, HPMPC was the most potent and selective of the four compounds tested. In vivo, during acute infection, the spleen indexes of all infected animals that were treated with 1.25 to 5.0 mg/kg/day of HPMPC for 5 days were significantly reduced as compared with sham-treated animals. Virus infectivity titers in blood and various tissues of infected animals treated with HPMPC, 2.5 or 1.25 mg/kg/day were not significantly lower than those of the infected, sham-treated animals; with 5 mg/kg/day, infectivity titers in the blood, spleen, and salivary gland were significantly lower in HPMPC-treated than in sham-treated animals. However, HPMPC was toxic to guinea pigs especially at doses of 5 to 10 mg/kg/day. These data showed that HPMPC was highly active and selective in cultured guinea pig cells and human fibroblast cells against CMV infection but did not effectively inhibit GPCMV infection in guinea pigs at minimum toxic concentrations.  相似文献   
7.
Alcoholic patients often have impaired immune function, yet little is known about the precise mechanism(s) of this impairment. We have previously shown that ethanol consumption by mice alters copolymer-specific humoral and cellular immune responses. In this study, we asked whether alcohol consumption by mice would phenotypically alter lymphocyte populations. Female C57BL/6 mice were fed a nutritionally complete liquid diet containing 35% ethanol-derived calories for up to 8 days. As controls, mice either were fed a liquid control diet that isocalorically substitutes sucrose for ethanol or remained on a standard solid diet and water ad libitum. Although mice fed ethanol-containing liquid or pair-fed control liquid diets have decreased numbers of spleen cells compared with solid diet controls, only the ethanol-containing diet allowed normally nonresponder C57BL/6 spleen cells to make antibody responses to the poly(Glu50Tyr50) synthetic copolymer antigen. Flow cytometric analysis of splenic lymphocyte populations of mice on the ethanol-containing diet shows an increase in the relative proportion of T-lymphocytes as compared with mice on either solid or liquid control diets. No such change is seen for either B-cell or natural killer cell populations in these same mice. Both liquid control and liquid ethanol diets caused a slight decrease in the CD4:CD8 ratios of splenic T-lymphocytes. We see the relative percentage of T-cells bearing the αβ-cell receptor (TcR) increases in the spleens of liquid ethanol diet mice; a smaller increase TcRαβ usage is seen in the spleens of liquid control mice, compared with solid diet mice. Flow cytometric analysis shows that little, if any, difference exists in TcRγδ expression between the liquid ethanol and either the liquid control or solid diet groups. Preliminary analysis of TcRαβ subsets suggest that ethanol increases the percentage of T-cells expressing Vβ5 and Vβ8, and decreases the percentage of Vβ11 expressing cells. These findings suggest that, in addition to modifying the immune response, ethanol alters the phenotypic expression of lymphocyte subsets.  相似文献   
8.
Summary Guinea pig embryo (GPE) cells showed different degrees of susceptibility to human adenovirus types as determined by virus infectivity assay and electron microscopic examination. Adenovirus 2 and 5 induced extensive cellular changes and produced high titers of infectious virus in GPE cells as in human cells. Mature progeny virus and protein crystals were observed in both cell types. Adenovirus 7 induced some cellular changes in GPE cells but only a small number of cells yielded progeny virus as determined by electron microscopy. Adenovirus 3, 8 and 31 induced some cellular changes but no progeny virus was found under electron microscopic examination. Characteristic fibers were observed in nuclei of adenovirus 31 infected cells. The ability of human adenovirus 2 and 5 to replicate in GPE cells is an example of an unusual cross-species biological property of certain adenovirus types. This property may be useful as a biological marker for these virus types.With 8 Figures  相似文献   
9.
A laboratory-based surveillance network of 11 clinical virological laboratories for influenza viruses was established in Taiwan under the coordination of the Center for Disease Control and Prevention (CDC), Taiwan. From October 2000 to March 2004, 3,244 influenza viruses were isolated, including 1,969 influenza A and 1,275 influenza B viruses. The influenza infections usually occurred frequently in winter in the northern hemisphere. However, the influenza seasonality in Taiwan was not clear during the four seasons under investigation. For example, the influenza A viruses peaked during the winters of 2001, 2002, and 2003. However, some isolated peaks were also found in the summer and fall (June to November) of 2001 and 2002. An unusual peak of influenza B also occurred in the summer of 2002 (June to August). Phylogenetic analysis shows that influenza A isolates from the same year were often grouped together. However, influenza B isolates from the year 2002 clustered into different groups, and the data indicate that both B/Victoria/2/87-like and B/Yamagata/16/88-like lineages of influenza B viruses were cocirculating. Sequence comparison of epidemic strains versus vaccine strains shows that many vaccine-like Taiwanese strains were circulating at least 2 years before the vaccine strains were introduced. No clear seasonality of influenza reports in Taiwan occurred in contrast to other more continental regions.  相似文献   
10.
The study investigates the correlation between oocyte maturity and fertilization and a variety of hormonal parameters in follicular fluid and ovarian granulosa cells. A methodology for purification of granulosa cells from contaminating blood cells is also established. A total of 63 follicular aspirates were collected at oocyte retrieval from 30 women superovulated using the long luteinizing hormone- releasing hormone (LHRH analogue)/human menopausal gonadotrophin regimen. Oestradiol, progesterone, testosterone and human chorionic gonadotrophin (HCG) were quantified in follicular fluid and granulosa cells were immunostained for human chorionic gonadotrophin. Immunopurification of granulosa cells from contaminating blood cells was performed. HCG in follicular fluid was significantly high in follicles yielding immature (grade 3) oocytes (P=0.002); there was no correlation with fertilization. Aspirates from follicles containing mature (grade 1) oocytes and oocytes that subsequently fertilized had significantly more granulosa cells immunobound to HCG (P < 0.001, P=0.02). Moreover, the immunomagnetic purification technique provided >98% pure population of granulosa cells. The data demonstrate that HCG in follicular fluid and on granulosa cells may help to predict oocyte maturity and fertilization. Furthermore, immunomagnetic beads provide a reliable procedure for the purification of ovarian granulosa cells.   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