首页 | 官方网站   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   499篇
  免费   66篇
  国内免费   4篇
医药卫生   569篇
  2023年   2篇
  2021年   6篇
  2020年   9篇
  2019年   11篇
  2018年   14篇
  2017年   15篇
  2016年   13篇
  2015年   5篇
  2014年   12篇
  2013年   11篇
  2012年   14篇
  2011年   19篇
  2010年   11篇
  2009年   8篇
  2008年   24篇
  2007年   21篇
  2006年   23篇
  2005年   19篇
  2004年   26篇
  2003年   20篇
  2002年   24篇
  2001年   33篇
  2000年   29篇
  1999年   25篇
  1998年   5篇
  1997年   9篇
  1996年   8篇
  1995年   6篇
  1994年   5篇
  1993年   6篇
  1992年   20篇
  1991年   17篇
  1990年   18篇
  1989年   15篇
  1988年   7篇
  1987年   10篇
  1986年   11篇
  1985年   8篇
  1984年   4篇
  1981年   3篇
  1980年   2篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   3篇
  1971年   2篇
  1970年   4篇
  1967年   1篇
  1966年   1篇
  1930年   1篇
排序方式: 共有569条查询结果,搜索用时 15 毫秒
1.
OBJECTIVE: The objective of this study was to radiographically quantify bone density and bone height preservation in tooth extraction alveolus filled with xenograft. STUDY DESIGN: The maxillary and mandibular fourth deciduous molars and fourth premolars of 6 minipigs were removed. Randomly, in 3 animals the right side was used as the test side and in the other 3 animals the left side was the test side. Intraoral radiographs were performed to compare the condition at the initial time and 3 months later. Measurements of bone height and bone density were performed using KS300 (Zeiss) software. RESULTS: After 3 months, there was a statistically significant smaller bone height loss for the test group. The test group presented a statistically greater bone density immediately after tooth extraction. However, after 3 months there was no statistically significant difference between the groups. CONCLUSIONS: The results suggest that treatment of postextraction alveolus with xenograft can preserve bone height initially but differences in bone density compared to when no xenograft is used are not sustained.  相似文献   
2.
We studied the effect of UFT (a mixture of Tegafur and uracil at a ratio of 1:4) on hepatocarcinogenesis and alpha-fetoprotein (AFP) production induced by 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB) in rats. By feeding rats with 3'-MeDAB diet, serum AFP started to appear from week 2-3 and increased until week 5-7, then declined until week 10-11. This phenomenon of a transient appearance of serum AFP is called "primary reaction". After week 11 hepatoma started to develop accompanied with an enormous elevation of serum AFP level until animals die, generally before week 25. Male Donryu strain rats fed a diet containing 0.06% 3'-MeDAB for 10 weeks, and then fed the normal diet. UFT was given by a stomach tube once a day for five days a week. Blood was collected from the tail vein every other week and serum AFP was measured by Rocket electrophoresis technique. When the administration of UFT (10 mg or 20 mg/kg/day) was started simultaneously with feeding 3'-MeDAB diet, the primary reaction was somewhat suppressed, and after week 11 development of hepatoma and elevation of AFP were markedly inhibited. The administration of UFT of a high dose (40 mg/kg/day) caused the death of animals in 7 weeks probably because of its toxicity. When the administration of UFT (10 mg or 20 mg/kg/day) was started after finish of feeding 3'-MeDAB diet for 10 weeks, the drug was not effective. These results show that if the administration of UFT was commenced at the same time with feeding 3'-MeDAB diet, the hepatocarcinogenesis and AFP production are strongly inhibited.  相似文献   
3.
Mammalian cells that have been committed to a certain cell lineage cannot be directed to other lineages. However, some astrocytes in the mammalian brains have been reported to represent plasticity to redirect to other cell lineages. We found that mouse hippocampal astrocytes cultured in aggregate forms of "astrosphere", redirected to MAP2-positive immature neurons. In astrospheres, basic HLH factors positively regulating neuronal differentiation were up-regulated and Id3 inhibiting basic HLH factors was down-regulated. Ectopic Id3 induction repressed redirection of astrocytes to a neuronal lineage, suggesting that astrosphere formation induced plasticity of astrocytes by changing the gene expression patterns.  相似文献   
4.
Of 14 asymptomatic hemophilia A patients receiving factor VIII concentrates, 11 severe hemophilia patients had an inverted T-helper/suppressor ratio but 3 moderate patients had a normal ratio. Most hemophilia patients showed poor lymphocyte proliferative responses to mitogens and diminished in vitro immunoglobulin-producing ability of lymphocytes. One important finding was that most patients were found to have increased numbers of Ia-like antigen-positive suppressor T cells, suggesting that circulation activated suppressor T cells. In addition, OKT8+ suppressor T cells from severe hemophilia patients showed strong suppressor activity on B-cell differentiation in a Nocardia delipidated cell mitogen-driven system, whereas those from normal age-matched controls showed no suppressor function. These results suggested that suppressor T cells in hemophilia patients treated with factors might be already activated in vivo by undetermined mechanisms, implying the presence of a peculiar immunoregulatory status in this disease.  相似文献   
5.
Soluble human interleukin-6 receptor (sIL-6R) was measured in the serum of 30 healthy individuals, 32 individuals with monoclonal gammopathy of undetermined significance (MGUS), 20 patients with early multiple myeloma (MM) and 54 patients with overt MM. The serum activity recognized by an immunoradiometric assay was determined to be sIL-6R, because of its binding capacity to IL-6 and its molecular mass of 55 kDa. All sera of healthy individuals contained sIL-6R (mean value: 89 ng/ml, range 17-300 ng/ml). Serum sIL-6R levels were increased by 51% in patients with MGUS (mean value: 135 ng/ml, p<0.005), by 44% in patients with early myeloma (mean value: 128 ng/ml, p<0.001) and by 116 % in patients with overt MM (mean value: 193 ng/ml, p<0.001). In patients with MM, a complete lack of correlation (p>0.7) was found between serum sIL-6R levels and other previously recognized prognostic factors in this disease, particularly serum IL-6 levels and those factors related to tumor cell mass. The independence of serum sIL-6R levels on tumor cell mass was directly demonstrated by studying four patients with MM treated with autologous bone marrow transplantation for periods of between 320 and 760 days. These levels were found to be remarkably stable and constant, independent of whether patients relapsed or achieved complete remission. Finally, physiological concentrations of sIL-6R were found to increase by tenfold the sensitivity of human myeloma cell lines to IL-6. These observations suggest a high control of the sIL-6R level in vivo, and, possibly, an important functional role of this circulating protein in patients with monoclonal gammopathies.  相似文献   
6.
Purpose: Our aim was to examine the changes in spatiotemporal tenascin (TN) expression in mouse uterus during early pregnancy, when the uterine tissue undergoes a tremendous restructuring. Methods: Using immunohistochemistry and in situ hybridization, the changes in distribution of TN protein in mouse uterine tissues in pregnancy Day 0 through Day 5 were analyzed. Results: Immunoreactive TN and TN mRNA were expressed in the basement membrane of the epithelium as well as in the smooth muscle layer, and their distribution shifted from the subbasement region on Day 0–3 to the smooth muscle layer on Days 4 and 5. Conclusions: These results indicate that TN expression in the uterus during early pregnancy is spatiotemporally different and may be regulated by a different mechanism.  相似文献   
7.
BACKGROUND AND OBJECTIVES: We have retrospectively analyzed the postoperative prognostic factors for 116 patients with stage I adenocarcinoma, with special reference to pleural retraction and intra-tumoral air-bronchogram imaged by computed tomography, which may represent the biological features of pulmonary adenocarcinoma for the retraction of surrounding tissues due to central necrosis and air space-lining growth, respectively. METHODS: The subgroups divided according to the presence of pleural retraction and/or intra-tumoral air-bronchogram on pre-operative CT were compared with respect to the postoperative disease-free survival (DFS) and other clinico-pathological factors. RESULTS: The rates of DFS at 5 years associated with 61 patients with pleural retraction and with 55 patients without pleural retraction were 64.4% and 91.3%, respectively (P = 0.0052), and those associated with 83 patients with air-bronchogram-positive tumors and with 33 patients with air-bronchogram-negative tumors were 81.8% and 64.8%, respectively (P = 0.0040). The DFS at 5 years associated with T1 (73 patients) and T2 (43 patients) were 83.6% and 64.3%, respectively (P = 0.0153). The Cox proportional hazards model analysis revealed that the presence of pleural retraction and the absence of air-bronchogram were independent factors for poor prognosis with relative risks of 7.8 and 5.1, respectively. Pathological T factor was also a significant prognostic factor with a relative risk of 3.2. Seventeen patients with pleural retraction-positive and air-bronchogram-negative tumors showed the high recurrence rate of 47.5% and a poor prognosis with DFS at 5 years of 35.1%. CONCLUSION: These results suggested that, in stage I adenocarcinoma, the degree of malignant potential may be well figured by radiological imaging, with a significant affect on susceptibility of recurrence following complete resection.  相似文献   
8.
Archival tissue specimens are valuable resources of materials for molecular biological analyses in retrospective studies, especially for rare diseases or those associated with exposure to uncommon environmental events. Although successful amplification with PCR is essential for analysis of DNA extracted from archival formalin-fixed, paraffin-embedded (FFPE) tissue specimens, we have often encountered problems with poor PCR amplification of target fragments. To overcome this, we examined whether heat treatment in alkaline solution could efficiently restore the PCR template activity of DNA that had already been extracted from FFPE lung cancer tissue specimens. The effect of the heat treatment was assessed by PCR for the TP53 gene and other lung cancer-related gene loci. The heat treatment of DNA samples in borate buffer resulted in successful PCR amplification of DNA fragments ranging from 91 to 152 bp. This technique for restoration of template activity of DNA for PCR amplification is very simple and economical, and requires no special apparatus, so it may be applicable for molecular analysis of DNA samples from FFPE tissue specimens at various laboratories.  相似文献   
9.
10.
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-23

京公网安备 11010802026262号