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   954篇
  免费   45篇
  国内免费   90篇
耳鼻咽喉   2篇
儿科学   52篇
妇产科学   11篇
基础医学   100篇
口腔科学   19篇
临床医学   215篇
内科学   206篇
皮肤病学   77篇
神经病学   24篇
特种医学   79篇
外科学   91篇
综合类   64篇
预防医学   32篇
眼科学   8篇
药学   73篇
中国医学   3篇
肿瘤学   33篇
  2017年   13篇
  2016年   9篇
  2015年   11篇
  2014年   24篇
  2013年   30篇
  2012年   11篇
  2011年   12篇
  2010年   33篇
  2009年   23篇
  2008年   11篇
  2007年   59篇
  2006年   19篇
  2005年   23篇
  2004年   15篇
  2003年   14篇
  2002年   14篇
  2001年   20篇
  2000年   15篇
  1999年   18篇
  1998年   35篇
  1997年   51篇
  1996年   35篇
  1995年   40篇
  1994年   36篇
  1993年   28篇
  1992年   17篇
  1991年   9篇
  1990年   24篇
  1989年   34篇
  1988年   22篇
  1987年   17篇
  1986年   15篇
  1985年   14篇
  1984年   9篇
  1983年   12篇
  1982年   11篇
  1981年   13篇
  1977年   11篇
  1976年   13篇
  1975年   8篇
  1968年   8篇
  1966年   9篇
  1965年   12篇
  1964年   7篇
  1963年   11篇
  1962年   7篇
  1959年   13篇
  1958年   7篇
  1956年   8篇
  1936年   7篇
排序方式: 共有1089条查询结果,搜索用时 15 毫秒
91.
OBJECTIVES: The goals of this literature review were to (1) update a prior review [Shiboski CH (1997) The epidemiology of HIV-related oral manifestations in women: a review. Oral Dis 3: S18–S27] of studies on the epidemiology of HIV-related oral manifestations in women prior to the availability of highly active antiretroviral therapy (HAART); (2) explore the effect of HAART on HIV-related oral disease among women; and (3) explore future research directions with respect to HIV-related oral disease epidemiology among African women.
METHODS: A computer-assisted search was conducted to identify studies on the prevalence of oral conditions in HIV-infected women in relation to immunological markers and HAART [excluding studies reviewed in Shiboski CH (1997) The epidemiology of HIV-related oral manifestations in women: a review. Oral Dis 3: S18–S27]. Results were summarized and discussed for (1) studies conducted in the developed world prior to and during the era of HAART; and (2) studies conducted in sub-Saharan Africa.
RESULTS: Candidiasis (OC) is the most common oral lesion among HIV-infected women, and has been found to be associated with a low CD4 count and a high plasma viral load. Preliminary findings suggest that HAART is associated with a decreasing OC incidence. The few studies identified on HIV-related oral disease in African women suggest that OC is also a common condition in this setting.
CONCLUSION: Future oral epidemiology research efforts in Africa should focus on the potential role of OC as sentinel marker of HIV infection and disease progression, to improve detection and prevention of selected opportunistic illnesses.  相似文献   
92.
用放射性同位素的方法研究了丁基苯肽(NBP)在大鼠体内代谢,并对代谢产物进行了鉴定。结果表明,大鼠ig3HNBP后24h,从尿和粪中排出的放射性分别为ig剂量的552%和185%,排除了药物蓄积在体内的可能性;用高效液相色谱法分离、纯化了丁基苯酞的两个主要的体外代谢产物代I和代I,根据代I和代II的波谱数据(UV,1HNMR,MS)确定了它们的化学结构;薄层色谱(TLC)证明丁基苯酞的体内代谢产物同样有代I和代I,并且也是两个主要的代谢产物;大鼠ig3HNBP后1h,脑中原型药与代谢物的比例为1∶1,而且只发现有代I,未发现有代I,推测代I很有可能是活性代谢产物。  相似文献   
93.
94.
Abstract: Labour and delivery involve severe pain for most women. The goal for pain treatment in obstetrics is to provide effective and safe analgesia during all phases of delivery. The ideal method for pain relief during delivery is not yet available. This thesis aims at studying some aspects of opioids in obstetric pain treatment with respect to analgesic efficacy and side-effects, and to analyse pain during delivery from a neurobiological perspective.  相似文献   
95.
The precision error of the bone densitometer is used to interpret significant change in bone mineral density (BMD) in serial studies. The precision error can be expressed as standard deviation (SD) or coefficient of variation (CV). The aims of this study are to determine the precision error over a range of BMD values and to demonstrate the application of the precision error in clinical practice. A bone phantom was used consisting of a perspex block with eight compartments containing varying amounts of hydroxyapatite powder to simulate a range of bone densities. The block was scanned 21 times and manual regions placed over each compartment to measure the BMD in each compartment. There were no significant differences in the variances or SD for all eight compartments, that is, over the range of BMD normally encountered in clinical practice. However, the calculated CV show a progressive fall in values as the BMD rises. Therefore, the SD should be used to calculate significant BMD change. In a practise with quality control procedures in place to detect calibration drift and with appropriately trained personnel, a change of approximately 0.05 g/cm2 is generally regarded as being a significant change at a 95% confidence level.  相似文献   
96.
测定了Gemini表面活性剂在pH值为10.86,NaBr浓度为1.0mol/L的溶液气/液界面上的表面压一分子面积的等温线。用自制的Brewster角显微镜(BAM)观察了由Gemini表面活性剂在界面上所形成单分子膜的微区形貌随表面压的变化。结果表明:当pH值为10.86时,Gemini表面活性剂在1.0mol/L NaBr溶液的气/液界面上生成了凝聚态的单分子膜;当表面压较低时,观察到在界面上形成了同心圆结构;随着表面压的增加,这些同心圆可发生聚并而形成多中心结构。  相似文献   
97.
A 36 year-old infertile female developed a stage IV (FIGO) ovarian carcinoma consisting of a poorly differentiated Sertoli-Leydig cell tumour after receiving one course of ovulation induction with follicle stimulating hormone (FSH), human menopausal gonadotrophin (HMG) and human chorionic gonadotrophin (HCG) followed by gonadotrophin-releasing hormone analogue (GnRHa). The patient died of liver metastasis and hepatic failure 4 1/2 months after first diagnosis, despite aggressive treatment consisting of debulking surgery and aggressive adjuvant chemotherapy.   相似文献   
98.
目的 探讨双探头SPECT心肌灌注显像时位移伪影的影像特征和识别方法。方法 将心脏模型置于检查床上,与受检患者的心脏方向一致。在图像采集过程中,模型依次沿相当于患者左右、头尾和前后方向分别在不同起始点、对不同帧数作一定距离的位移。结果位移伪影的共同特点是表现为室壁放射性分布不均匀,“热区”与“冷区”交替出现,在短轴上最早出现,且表现最为明显;伪影进一步发展会在水平长轴和垂直长轴上表现为心尖附近放射性稀疏或缺损,出现与相邻室壁伴行且形态相近的“伴影”。结论位移伪影主要表现为室壁放射性分布不均,“热区”与“冷区”交替出现,在短轴图像上易于早期发现。  相似文献   
99.
100.
Sham  RL; Packman  CH; Abboud  CN; Lichtman  MA 《Blood》1991,77(2):363-370
Maturation of human myeloid cells is associated with quantitative and qualitative changes in protein kinase C (PKC) and increases in N-formyl- L-methionyl-L-leucyl-L-phenylalanine (FMLP) receptors, actin, and actin regulatory proteins. We have studied the actin responses and cell shape changes caused by FMLP and its second messenger pathways in HL60 cells undergoing neutrophilic maturation. In uninduced cells, the PKC activators 12-O-tetradecanoyl phorbol-13-acetate (TPA), bryostatin, and 1-oleyl-2-acetylglycerol (OAG) resulted in 15% to 30% decreases in F- actin, whereas FMLP had no effect. Ionomycin had no effect on actin but did cause a 10-fold increase in intracellular calcium. Cells grown for 24 hours in 1% dimethyl sulfoxide (DMSO) acquired the ability to polymerize actin in response to FMLP and ionomycin. TPA continued to cause a decrease in F-actin at 24 hours, but caused an increase in F- actin at 48 to 72 hours of maturation. The PKC inhibitor 1-5- isoquinolinesulfonyl 2-methylpiperazine (H7) partially blocked the F- actin increase caused by TPA in induced cells, but had no effect on the decrease in F-actin caused by TPA in uninduced cells or the increase in F-actin seen in FMLP-treated neutrophils. F-actin rich pseudopods developed following TPA or FMLP stimulation of induced HL60 cells; in uninduced cells neither agent caused pseudopod formation but TPA caused a dramatic loss of surface ruffles. The ability of FMLP and ionomycin to elicit a neutrophil-like actin response in HL60 cells within 24 hours after DMSO treatment shows that the actin regulatory mechanism is mature by that time. The inability of ionomycin to increase F-actin in uninduced cells supports the view that calcium increases alone are insufficient for actin polymerization. The longer maturation time required for HL60 cells to develop an actin polymerization response to TPA compared with FMLP, coupled with the inability of H7 to block the FMLP-mediated F-actin increase in neutrophils, suggests that the F- actin increase caused by FMLP is not mediated solely by PKC. Lastly, the TPA-induced F-actin decrease and shape changes in uninduced HL60 cells, and the longer time required for a "mature" response to TPA, may reflect immaturity in the PKC isoenzyme pattern rather than immaturity of the actin regulatory mechanism.  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