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   1628篇
  免费   71篇
  国内免费   11篇
耳鼻咽喉   12篇
儿科学   48篇
妇产科学   40篇
基础医学   253篇
口腔科学   16篇
临床医学   149篇
内科学   356篇
皮肤病学   16篇
神经病学   122篇
特种医学   110篇
外科学   226篇
综合类   21篇
预防医学   139篇
眼科学   54篇
药学   89篇
中国医学   1篇
肿瘤学   58篇
  2021年   20篇
  2019年   22篇
  2018年   21篇
  2016年   15篇
  2015年   28篇
  2014年   43篇
  2013年   45篇
  2012年   61篇
  2011年   59篇
  2010年   26篇
  2009年   34篇
  2008年   60篇
  2007年   68篇
  2006年   80篇
  2005年   65篇
  2004年   49篇
  2003年   63篇
  2002年   42篇
  2001年   46篇
  2000年   38篇
  1999年   40篇
  1998年   24篇
  1997年   24篇
  1996年   27篇
  1995年   14篇
  1994年   19篇
  1993年   22篇
  1992年   38篇
  1991年   35篇
  1990年   28篇
  1989年   29篇
  1988年   33篇
  1987年   26篇
  1986年   30篇
  1985年   38篇
  1984年   31篇
  1983年   25篇
  1982年   20篇
  1979年   34篇
  1978年   13篇
  1977年   14篇
  1976年   12篇
  1975年   15篇
  1974年   13篇
  1973年   20篇
  1972年   14篇
  1969年   20篇
  1968年   14篇
  1966年   19篇
  1965年   12篇
排序方式: 共有1710条查询结果,搜索用时 15 毫秒
81.
82.
83.
The PET tracer [11C]5-hydroxytryptophan ([11C]5-HTP), which is converted to [11C]5-hydroxytryptamine ([11C]5-HT) by aromatic amino acid decarboxylase (AADC), is thought to measure 5-HT synthesis rates. But can we measure these synthesis rates by kinetic modeling of [11C]5-HTP in rat? Male rats were scanned with [11C]5-HTP (60 minutes) after different treatments. Scans included arterial blood sampling and metabolite analysis. 5-HT synthesis rates were calculated by a two-tissue compartment model (2TCM) with irreversible tracer trapping or Patlak analysis. Carbidopa (inhibitor peripheral AADC) dose-dependently increased [11C]5-HTP brain uptake, but did not influence 2TCM parameters. Therefore, 10 mg/kg carbidopa was applied in all subsequent study groups. These groups included treatment with NSD 1015 (general AADC inhibitor) or p-chlorophenylalanine (PCPA, inhibitor of tryptophan hydroxylase, TPH). In addition, the effect of a low-tryptophan (Trp) diet was investigated. NSD 1015 or Trp depletion did not affect any model parameters, but PCPA reduced [11C]5-HTP uptake, and the k3. This was unexpected as NSD 1015 directly inhibits the enzyme converting [11C]5-HTP to [11C]5-HT, suggesting that trapping of radioactivity does not distinguish between parent tracer and its metabolites. As different results have been acquired in monkeys and humans, [11C]5-HTP-PET may be suitable for measuring 5-HT synthesis in primates, but not in rodents.  相似文献   
84.
This study compared 69 adult children of alcoholics (ACOAs) with 30 control college students on scales from the revised MMPI (MMPI-2). ACOA subjects could be differentialted from control subjects on several MMPI-2 scales and two-scale profiles, many of which differentiate alcoholic from nonalcoholic samples. However, the length of time the child had lived in the home with the alcoholic parent and the degree of impairment associated with alcohol abuse in the parent did not moderate these findings. In contrast, MMPI-2 scales that measure impulsive and antisocial behavior did differentiate ACOAs who drank at least once a week from ACOAs who did not report this level of drinking.  相似文献   
85.
INTRODUCTION Chemokines represent a family of small chemotactic cytokines, initially identified as mediators of leucocyte trafficking and homing. In the last few years, chemokines have been shown to participate also in tumor growth and the lymphatic and e…  相似文献   
86.
87.
Aim:  To determine if IgA is required for protection against Chlamydia infection in the male reproductive tract (MRT).
Materials and Methods:  Male polyimmunoglobulin receptor knockout mice (PIgR-/-) and wild-type C57BL/6 (WT) mice were immunised intranasally with chlamydial major outer membrane protein (MOMP) and cholera toxin (CT). MOMP-specific IgG and IgA in serum and prostatic fluids were measured by ELISA. Serum and PF were also assayed for inhibition of in vitro chlamydial infection. Immunized WT and PIgR-/- mice were challenged by direct inoculation of C. muridarum into the meatus urethra. Four weeks post challenge Chlamydia levels in the penile urethra, epididymis and testis were determined by PCR.
Results:  Equivalent levels of IgG were found in the serum of both WT and PIgR-/- mice however IgA in serum of PIgR-/- mice was 19- to 20-fold higher than in WT animals consistent with the lack of the PIgR IgA transport molecule. IgA levels were significantly lower in PIgR-/- PF compared to WT PF after both immunization and infection. Only PF from WT but not PIgR-/- animals was able to inhibit in vitro chlamydial infection. Following challenge significantly higher levels of Chlamydia were recovered from the MRT of PIgR-/- mice compared to WT animals.
Conclusions:  Male mice lacking a functional PIgR were unable to clear a genital tract Chlamydia infection despite high levels of serum IgA. These data show that mucosal IgA plays a major role in preventing chlamydial infection of the male genital tract and suggest that immunization strategies to protect males should target a strong mucosal IgA response.  相似文献   
88.
目的:目前有关骨髓间充质干细胞向内皮细胞诱导分化的研究较少。本实验分离和培养人骨髓间充质干细胞,用带有VEGF165的质粒转染人骨髓间充质干细胞,探讨血管内皮生长因子对其体外诱导分化的作用。 方法:实验于2005—04/2006—04在吉林大学人兽共患病教育部重点实验室完成。取成人的已排除血液系统肿瘤疾病的新鲜骨髓(自愿提供),采用Percoll梯度分离培养骨髓间充质干细胞,于倒置显微镜下观察细胞形态变化和生长情况。原代细胞培养至增殖接近融合状态时,单克隆培养法分离传代培养,扩增骨髓间充质干细胞。采用流式细胞术检测细胞免疫学表型。在原核细胞大肠杆菌DH5α中复制扩增和提取,纯化、克隆pcDNA3.0-VEGF165质粒。用脂质体转染法转染骨髓间充质干细胞:应用流式细胞术检测诱导后骨髓间充质干细胞免疫学表型变化j并采用免疫荧光染色鉴定转染情况,并设质粒空载和未转染的骨髓间充质干细胞为对照。 结果:人骨髓间充质干细胞原代培养1周后,造血细胞消失,贴壁细胞体积增大,呈现梭形外观,有粗大的细胞突起伸出。2周后细胞融合成单层,梭形突起变长,排列有明显的方向性,细胞排列成旋涡状、网状、辐射状。流式细胞术显示,人骨髓间充质干细胞免疫学表型CD44、CD29阳性,CD34、CD31、CD45阴性。VEGF165诱导骨髓间充质千细胞后CD44表达明显降低,CD31明显升高。免疫荧光染色显示,用FITC标记后的VEGF抗体使细胞显现绿色荧光,用cy3标记的CD31抗体使细胞显现了红色荧光。 结论:转染后的骨髓间充质干细胞细胞表型发生明显转变,CD31表达率明显增高,呈现典型的内皮细胞的表型特征,这说明骨髓间充质干细胞具有向内皮细胞分化的潜能。  相似文献   
89.
This article suggests the ways in which information may be collected and used to provide a basis for documenting the need for psychosocial services to children. Emphasis is placed upon the need to establish meaningful benefits of psychosocial programming within the context of current economic constraints in the health care system.  相似文献   
90.
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