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   1403篇
  免费   131篇
  国内免费   15篇
耳鼻咽喉   49篇
儿科学   62篇
妇产科学   74篇
基础医学   121篇
口腔科学   41篇
临床医学   188篇
内科学   203篇
皮肤病学   12篇
神经病学   40篇
特种医学   149篇
外科学   144篇
综合类   20篇
一般理论   13篇
预防医学   293篇
眼科学   21篇
药学   38篇
肿瘤学   81篇
  2023年   9篇
  2022年   11篇
  2021年   21篇
  2020年   13篇
  2019年   16篇
  2018年   23篇
  2017年   36篇
  2016年   23篇
  2015年   25篇
  2014年   40篇
  2013年   67篇
  2012年   72篇
  2011年   71篇
  2010年   53篇
  2009年   46篇
  2008年   61篇
  2007年   81篇
  2006年   65篇
  2005年   65篇
  2004年   54篇
  2003年   38篇
  2002年   46篇
  2001年   41篇
  2000年   40篇
  1999年   40篇
  1998年   18篇
  1997年   21篇
  1996年   18篇
  1995年   17篇
  1994年   21篇
  1993年   13篇
  1992年   13篇
  1991年   14篇
  1990年   9篇
  1989年   16篇
  1988年   14篇
  1987年   12篇
  1986年   9篇
  1985年   12篇
  1984年   18篇
  1983年   10篇
  1981年   7篇
  1980年   10篇
  1979年   10篇
  1977年   9篇
  1975年   7篇
  1967年   7篇
  1947年   7篇
  1922年   14篇
  1921年   13篇
排序方式: 共有1549条查询结果,搜索用时 15 毫秒
1.
The ability of three Porphyromonas spp., seven Prevotella spp., seven Fusobacterium spp. and two related Bacteroides spp. (B. levii and B. macacae) to degrade an extensive range of synthetic endo-, amino- and diamino peptidase substrates linked to the fluorescent leaving group 7-amido-4-methylcoumarin (NHMec) was investigated. Many more species than was previously recognized exhibited peptidase activities, albeit at lower levels than those already described for Porphyromonas gingivalis. Detection of chymotrypsin-like activity was dependent on which of three NHMec-linked substrates was used, but all species exhibited degradative activity with at least one of these substrates. Elastase-like activity was detected in all species though not all species reacted with each of the elastase substrates. Glycylprolyl peptidase activity was detected in all of the species tested with the exception of F. mortiferum, F. gonidiaformans, F. naviforme and F. necrophorum. While the detection of peptidase activities does not appear to be useful for the differentiation of species within the genera Bacteroides and Prevotella, its ability to differentiate species of the genus Porphyromonas or Fosobacterium further investigation.  相似文献   
2.
3.
4.
T lymphocyte function was analyzed in patients hemodialyzed with 'high-flux' polysulfone membranes, which have been reported to improve the patients' overall clinical condition and well-being. For comparison purposes, patients treated by the use of 'low-flux' cuprophane membranes were also studied. Peripheral blood white cell counts, numbers of lymphocytes as well as the numbers of T cells and their CD4 and CD8 subsets were within normal range in both patient groups. The absolute number of B cells was slightly decreased in cuprophane-membrane- but not polysulfone-membrane-treated patients. The proliferative response of T lymphocytes after stimulation with optimal concentration of phytohemagglutinin (PHA) was normal in patients treated with 'high-flux' membrane dialysis but significantly reduced in those treated with cuprophane membranes. The generation of interleukin-2 (IL-2) receptor on T lymphocytes after PHA stimulation was normal in the polysulfone-membrane-treated group and slightly impaired in the cuprophane-membrane-dialyzed patients. Production of both IL-2 and interleukin-1, as well as the natural killer cell activity, in patients treated by 'high-flux' membrane dialysis were also comparable to controls. The levels of serum beta 2-microglobulin were significantly elevated in patients-maintained on 'high-flux' dialysis membranes but did not reach the levels seen in patients dialyzed by cuprophane membranes. The beta 2-microglobulin at levels seen in patients on cuprophane dialysis had no effects on activation and proliferation of control lymphocytes in vitro. These results suggest that impaired functional responses of T lymphocytes seen in end-stage disease patients on prolonged hemodialysis with cuprophane membranes are not seen in similar patients hemodialyzed with polysulfone membranes.  相似文献   
5.
6.
7.
STUDY OBJECTIVE: To determine whether buffered lidocaine must be prepared just before use. DESIGN: Randomized, double-blind, prospective trial. SETTING: University hospital. PARTICIPANTS: Twenty-four adult volunteers. INTERVENTIONS: Three buffered lidocaine solutions prepared seven days, one day, and just before use were compared with a control solution. Subjects received 0.5 mL intradermal injections of each solution. Pain of infiltration and extent and duration of anesthesia were measured. MEASUREMENTS AND MAIN RESULTS: Pain of infiltration was less with all buffered solutions than control (P less than .0001). Mean maximum diameter of anesthesia ranged from 29 to 33 mm for the buffered solutions compared with 31 mm for control. Mean duration of anesthesia was 33 minutes for control and 30 minutes for all of the buffered solutions. There was no statistically significant difference in extent or duration of anesthesia for any of the solutions (P greater than .5, beta = .15 for delta = 10%). CONCLUSION: Buffered lidocaine stays effective for up to one week after preparation. It is therefore convenient to use in emergency settings.  相似文献   
8.
Subgingival plaque samples from three discrete sites in each of eight patients with adult chronic periodontitis were used to determine the ability of 0.001, 0.01, 0.1 and 1.0 mM chlorhexidine to inhibit bacterial proteolytic activity. This activity was measured by monitoring the increase in relative fluorescence (excitation and emission wavelengths of 495 and 525 nm, respectively) accompanying the degradation of fluorescein isothiocyanate (FITC)-labelled bovine serum albumin or FITC-labelled transferrin. Chlorhexidine at concentrations of as low as 0.01 mM inhibited the proteolytic degradation of both substrates by more than 50%. As the growth of dental plaque bacteria is dependent upon the liberation of nutrients (amino acids, peptides and carbohydrates) from host-derived macromolecules, similar effects in vivo might explain the ability of chlorhexidine to inhibit plaque formation at subminimal inhibitory concentrations.  相似文献   
9.
10.
Contact skin immunization of mice with reactive hapten antigen and subsequent airway challenge with the same hapten induces immediate airflow obstruction and subsequent airway hyper‐reactivity (AHR) to methacholine challenge, which is dependent on B cells but not on T cells. This responsiveness to airway challenge with antigen is elicited as early as 1 day postimmunization and can be adoptively transferred to naïve recipients via 1‐day immune cells. Responses are absent in 1‐day immune B‐cell‐deficient JH?/? mice and B‐1 B‐cell‐deficient xid male mice, as well as in recipients of 1‐day immune cells depleted of cells with the B‐1 cell phenotype (CD19+ B220+ CD5+). As B‐1 cells produce immunoglobulin M (IgM), we sought and found significantly increased numbers of anti‐hapten IgM‐producing cells in the spleen and lymph nodes of 1‐day immune wild‐type mice, but not in xid mice. Then, we passively immunized naive mice with anti‐hapten IgM monoclonal antibody and, following airway hapten challenge of the recipients, we showed both immediate airflow obstruction and AHR. In addition, AHR was absent in complement C5 and C5a receptor‐deficient mice. In summary, this study of the very early elicited phase of a hapten asthma model suggests, for the first time, a role of B‐1 cells in producing IgM to activate complement to rapidly mediate asthma airway reactivity only 1 day after immunization.  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