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   1489篇
  免费   103篇
  国内免费   25篇
耳鼻咽喉   3篇
儿科学   145篇
妇产科学   14篇
基础医学   144篇
口腔科学   66篇
临床医学   144篇
内科学   343篇
皮肤病学   39篇
神经病学   28篇
特种医学   330篇
外科学   85篇
综合类   21篇
预防医学   61篇
眼科学   16篇
药学   87篇
  1篇
中国医学   1篇
肿瘤学   89篇
  2023年   2篇
  2022年   4篇
  2021年   13篇
  2020年   8篇
  2019年   13篇
  2018年   23篇
  2017年   17篇
  2016年   22篇
  2015年   31篇
  2014年   26篇
  2013年   49篇
  2012年   10篇
  2011年   12篇
  2010年   40篇
  2009年   79篇
  2008年   19篇
  2007年   40篇
  2006年   38篇
  2005年   33篇
  2004年   22篇
  2003年   26篇
  2002年   21篇
  2001年   25篇
  2000年   22篇
  1999年   32篇
  1998年   101篇
  1997年   118篇
  1996年   113篇
  1995年   77篇
  1994年   83篇
  1993年   98篇
  1992年   18篇
  1991年   19篇
  1990年   18篇
  1989年   44篇
  1988年   39篇
  1987年   27篇
  1986年   34篇
  1985年   31篇
  1984年   19篇
  1983年   15篇
  1982年   19篇
  1981年   34篇
  1980年   20篇
  1979年   8篇
  1978年   8篇
  1977年   21篇
  1976年   19篇
  1975年   6篇
  1970年   1篇
排序方式: 共有1617条查询结果,搜索用时 46 毫秒
81.
Decker  T; Flohr  T; Trautmann  P; Aman  MJ; Holter  W; Majdic  O; Huber  C; Peschel  C 《Blood》1995,86(3):1115-1123
We investigated the production of cytokines by highly purified T helper cells from B-cell chronic lymphocytic leukemia (B-CLL) patients stimulated by different activation pathways, and we studied the influence of various accessory cell populations on the pattern of the secretion of cytokines, including interleukin (IL)-2, IL-4, interferon- gamma (IFN-gamma), and IL-10. Neither a qualitative nor a quantitative difference in cytokine production and proliferative capacity was observed in CLL-derived purified T cells compared with normal individuals, when T cells were stimulated by different pathways, including CD3, CD2, and costimulation with CD28. Addition of autologous accessory cells (aAC), however, dramatically influenced the cytokine pattern of normal versus B-CLL-derived T cells. CLL cells as aAC caused a marked increase of IL-2, whereas IFN-gamma was only slightly induced and IL-4 was not influenced. In contrast, in normal individuals addition of aAC, which predominantly consisted of monocytes, resulted in a significant increase of IFN-gamma and a reduction of IL-4 secretion. IL-2 production was inhibited by higher concentrations of aAC. The increased stimulation of IL-2 production by CLL cells was not specific to the leukemic cell population, as purified B cells from normal individuals had the same effect. On the other hand, purified monocytes from CLL patients and controls both induced IFN-gamma production and inhibited IL-4 secretion. After antigen-specific stimulation with tetanus toxoid, cytokine secretion was influenced by the type of aAC in a similar pattern. We conclude that T helper cells derived from patients with B-CLL are intrinsically normal and that the predominance of B cells as accessory cells in CLL significantly alters the immune function of T helper cells in vitro.  相似文献   
82.
The purpose of this study was to define, in a phase I study in leukemia, the maximally tolerated dose (MTD), major toxicities, and possible antitumor activity of Topotecan, a new topoisomerase I (topo I) inhibitor. Topotecan was delivered by a 5-day continuous infusion every 3 to 4 weeks to patients with refractory or relapsed acute leukemia, at doses ranging from 3.5 mg/m2 to 18 mg/m2 per course. Twenty-seven patients were treated, including 17 patients with acute myelogenous or undifferentiated leukemia, 7 with acute lymphocytic leukemia, and 3 with chronic myelogenous leukemia in blastic phase. Severe mucositis was the dose-limiting toxicity occurring in two of five patients treated with Topotecan 11.8 mg/m2 per course; a third patient had prolonged myelosuppression. At the MTD of 10 mg/m2 per course, 1 of 12 patients had severe mucositis and 5 had mild-to- moderate mucositis. Nausea, vomiting, diarrhea, and prolonged myelosuppression were uncommon. Three patients (11%) achieved a complete response, two (7%) had a partial response, and one (4%) had a hematologic improvement. The overall complete plus partial response rate was 19%, and 24% in acute myelogenous or undifferentiated leukemia. A novel in vitro assay that quantifies Topotecan-stabilized topo I-DNA complexes in patient samples was used, which demonstrated heterogeneity in the ability of Topotecan to interact with topo I, the intracellular target of Topotecan. This phase I study defined the MTD of Topotecan to be 10 mg/m2 by continuous infusion over 5 days every 3 to 4 weeks in patients with refractory or relapsed acute leukemia. Severe mucositis was the dose-limiting toxicity. Future studies will define the precise activity of Topotecan in different leukemia subsets, its efficacy in combination with other antileukemic drugs, and correlations between Topotecan-induced topo I-DNA complex formation and individual patient response to Topotecan.  相似文献   
83.
In the present study, we investigated the effect of interferon-alpha (IFN-alpha) on the expression of interleukin-10 (IL-10) mRNA and protein synthesis in human monocytes and CD4+ T cells. In mononuclear cells, IFN-alpha induced expression of IL-10 mRNA and further enhanced lipopolysaccharide (LPS)-stimulated IL-10 expression. In purified monocytes, a strong expression of IL-10 mRNA induced by LPS was not further enhanced by IFN-alpha. In highly purified CD4+ T cells, IFN- alpha upregulated IL-10 mRNA upon activation with phytohemagglutinin and phorbol myristate acetate. In purified monocytes, an effect of IFN- alpha on IL-10 protein synthesis was dependent on costimulation with LPS. Maximal stimulation of IL-10 protein by IFN-alpha was seen after prolonged incubation periods of 48 to 96 hours, whereas IFN-gamma reduced IL-10 production in the early incubation period. Similar effects of IFN-alpha were observed in CD4+ T cells activated with CD3 and CD28 monoclonal antibodies. Addition of IFN-alpha caused an increase of IL-10 in culture supernatants of activated T-helper cells of more than 100% after 96 hours of incubation. In contrast, other cytokines, including IFN-gamma and IL-4, had no influence on IL-10 secretion stimulated by CD3 and CD28 in CD4+ T cells. In serum samples of IFN-alpha-treated individuals, we failed to detect an influence of cytokine treatment on IL-10 serum levels, confirming the requirement of additional activating signals for IFN-alpha-mediated effects on IL-10 synthesis. In conclusion, IFN-alpha enhances the late induction of IL- 10, which physiologically occurs upon stimulation of monocytes and T cells. Biologically, this effect might enhance the negative-feedback mechanism ascribed to IL-10, which limits inflammatory reactions.  相似文献   
84.
85.
86.
87.
AIMS: To clarify p21(waf1/cip1) expression in sinonasal lesions. METHODS: Archived surgical specimens from 38 patients were investigated by means of immunohistochemistry. p21(waf1/cip1) staining was evaluated in the different layers of the epithelium. In addition, human papillomavirus (HPV) infection and p53 protein overexpression were assessed and correlated with p21(waf1/cip1) expression. RESULTS: p21(waf1/cip1) staining was negative in non-papillomatous nasal mucosa. HPV infection and p53 protein overexpression were not seen. Sixteen of 20 inverted papillomas showed p21(waf1/cip1) expression. HPV infection was found in 16 cases and p53 protein overexpression was present in 13 specimens. Expression of p21(waf1/cip1) was restricted to surface cells in five cases, but involved basal/parabasal cells in 11 specimens. Immunoreactivity for p21(waf1/cip1) in basal/parabasal cells colocalised with p53 protein overexpression. Enhanced expression rates for p21(waf1/cip1) were seen in transitional and squamous epithelium compared with columnar epithelium. p21(waf1/cip1) expression involved only surface cells in cylindrical cell papillomas. HPV infection and p53 protein overexpression were detected in all specimens. One of five squamous cell carcinomas showed p21(waf1/cip1) expression. HPV infection was seen in two cases, and all carcinomas showed p53 protein overexpression. CONCLUSIONS: Expression of p21(waf1/cip1) is associated with terminal differentiation in surface cells in inverted papillomas and cylindrical cell papillomas, but not in non-papillomatous nasal mucosa. Overexpression of p53 protein colocalises with p21(waf1/cip1) expression in basal/parabasal cells in inverted papillomas but not in cylindrical cell papillomas. Expression of p21(waf1/cip1) in squamous cell carcinomas involves a subset of tumours with p53 protein overexpression.  相似文献   
88.
WHO生存质量评估简表的等价性评价   总被引:20,自引:0,他引:20  
目的评价WHO生存质量评估简表(WHOQOL-BREF)在13个国家的等价性。方法采用多组验证性因子分析方法,对世界卫生组织生存质量研究小组提供的13个国家的数据进行分析,评价WHOQOL-BREF不同国家的等价性。结果各个国家的各个领域的Cronbachα系数均大于0·7,分布在0·7至0·88之间。除了英国和挪威之外,其它国家的社会关系领域的Cronbachα系数均大于0·65。采用根据世界卫生组织生存质量研究小组研制量表时构建的四因子模型对数据分别进行拟合,拟合优度指数(CFI)均大于0·8,其中德国、西班牙和美国的拟合优度指数大于0·9。多组验证性因子分析发现模型拟合尚可,CFI等于0·88,各个国家的因子负荷不全相等,因子负荷的轮廓相似。结论WHOQOL-BREF在13个国家具有相同的因子结构,且有等价性。  相似文献   
89.
目的 与开腹胆囊切除术相比,腹腔镜胆囊切除术(LC)有减少术后不适和较少的创作,但仍有改进的余地。方法:为进一步减轻手术创伤,我们引进了针式腹间胆囊切除术,共29例。结果 平均手术时间为75分钟,19例当天出院,10例隔天出院,其中1例是胆总管探查。结论 针式航空 镜胆囊切除术是一种可靠的技术。  相似文献   
90.
Aim: This study investigates the effect of rapid weight gain in term children, adolescents and young adults born appropriate for gestational age. Methods: In all, 173 girls and 178 boys aged 6.1–19.9 (12.5 ± 3.1)years participated. Rapid weight gain (group 1) was defined as a change in weight‐SDS (standard deviation score) from birth till two years >0.67, ‘no change’ as ≥?0.67 and ≤0.67 (group 2) vs ‘slow weight gain’ as 90th age‐/sex‐specific BMI‐percentile was defined as overweight. Parental BMI, socio‐economic status and lifestyle were assessed as confounders. Results: A total of 22.8% gained weight rapidly, and 15.7% was overweight. Group 1 compared with group 2 and 3 subjects was taller, heavier and had a higher prevalence of overweight (girls/boys: 26.2%/28.9% vs 11.6%/19.0% vs 2.8%/5.0%; p < 0.01/p < 0.05). Concomitantly, a higher WC, %FM and FFM were observed. Rapid weight gain was positively associated with REE (adjusted for FFM) in boys (r = 0.26; p < 0.01), but not with cardio‐metabolic risk factors. Conclusion: Rapid weight gain was related to increases in height, weight, a higher prevalence of overweight and central fat distribution. In addition, rapid weight gain was related to a higher REE in boys, but not to cardio‐metabolic risk factors.  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