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   3684篇
  免费   278篇
  国内免费   81篇
耳鼻咽喉   49篇
儿科学   54篇
妇产科学   35篇
基础医学   633篇
口腔科学   95篇
临床医学   203篇
内科学   507篇
皮肤病学   33篇
神经病学   290篇
特种医学   112篇
外科学   181篇
综合类   286篇
一般理论   2篇
预防医学   639篇
眼科学   21篇
药学   587篇
  1篇
中国医学   257篇
肿瘤学   58篇
  2023年   43篇
  2022年   60篇
  2021年   125篇
  2020年   95篇
  2019年   125篇
  2018年   115篇
  2017年   121篇
  2016年   110篇
  2015年   105篇
  2014年   195篇
  2013年   320篇
  2012年   182篇
  2011年   172篇
  2010年   130篇
  2009年   184篇
  2008年   144篇
  2007年   133篇
  2006年   146篇
  2005年   113篇
  2004年   97篇
  2003年   107篇
  2002年   96篇
  2001年   68篇
  2000年   63篇
  1999年   45篇
  1998年   66篇
  1997年   59篇
  1996年   69篇
  1995年   73篇
  1994年   70篇
  1993年   54篇
  1992年   53篇
  1991年   60篇
  1990年   38篇
  1989年   31篇
  1988年   36篇
  1987年   34篇
  1986年   29篇
  1985年   38篇
  1984年   32篇
  1983年   25篇
  1982年   39篇
  1981年   18篇
  1980年   25篇
  1979年   23篇
  1978年   18篇
  1977年   10篇
  1976年   15篇
  1975年   11篇
  1973年   7篇
排序方式: 共有4043条查询结果,搜索用时 15 毫秒
21.
Semiconductor manufacturing: an introduction to processes and hazards   总被引:2,自引:0,他引:2  
Recent studies suggest that semiconductor workers have an increased incidence of work-related illness. Semiconductor manufacturing is a chemically intensive industry involving many potentially hazardous operations. As this industry moves into new geographic areas, health care professionals will be asked to evaluate medical or workplace conditions associated with unfamiliar and complex production processes. This paper provides an overview of semiconductor manufacturing processes for these health practitioners. Each step of device fabrication is detailed with its attendant chemical and physical hazards. Broader concepts of industrial control technology, clean room ventilation, and ergonomics are explained. The hazards are tabulated to allow rapid assessment of the risks inherent to each processing step. References have been chosen to guide the reader to more indepth information.  相似文献   
22.
AIMS: The rate of autologous urine production should not have a major disturbing influence on cystometric urodynamic parameters such as first filling sensation, normal desire to void, strong desire to void, and cystometric bladder capacity. Instructions to patients and drinking behavior can have considerable impact, especially if filling cystometry is preceded by free uroflowmetry. We studied the influence of autologous urine production during filling cystometry on total bladder volume. METHODS: Urodynamic investigations performed between September of 2000 and February of 2001 were analyzed. Only those urodynamic investigations for which total bladder capacity could be calculated were taken into account (i.e., catheterization before and after cystometry and no urine loss during the investigations). RESULTS: After screening, 186 investigations were used for further analysis. Mean filled volume (external infusion plus autologous urine production) was 346 +/- 152 mL, but mean real bladder capacity (i.e., voided volume + residual urine) was 391 +/- 170 mL. In all patients, 14% extra urine was produced due to autologous urine production (mean filling rate, 6.1 mL/min). In 42% of the investigations, the real bladder capacity was more than 110% of the infused volume. In 18% of the patients, the contribution of natural bladder filling was more than 25% of the infused volume. CONCLUSIONS: Natural bladder filling plays a substantial role during filling cystometry and has a disturbing influence on calculated urodynamic parameters. Attention should be paid to patient instructions before the urodynamic investigation. The combination of free uroflowmetry followed by filling cystometry should be avoided. This avoidance is especially important if interventional studies are performed. Careful interpretation of studies depending on bladder capacity parameters is mandatory, and such parameters should be corrected for autologous bladder filling.  相似文献   
23.
作者采用正文试验法,以水提醇沉法提取和分离酚戒类有效成分,并以苯乙醇成含量作为含量测定指标,考察了乙醇浓度、提取温度及煎煮时间三个因素对有效成分提取量的影响,从而筛选出芸杞补肾口服液的是佳生产工艺。  相似文献   
24.
选择体重、年龄、胎次、产乳量基本一致的荷斯坦泌乳奶牛10头,随机分为两组,分别为对照组(空白)和试验组;试验组每头奶牛每天一次补充10g添加剂。结果显示,添喂益绿素添加剂的试验组与对照组相比日产标准乳提高7.16%(P<0.01),奶料比提高7.31%(P<0.01),经济效益提高17.0%。表明添喂益绿素添加剂能有效提高奶牛产奶量,经济效益明显。  相似文献   
25.
We evaluated the effects of allogeneic bone marrow stromal cell treatment of stroke on functional outcome, glial–axonal architecture, and immune reaction. Female Wistar rats were subjected to 2 h of middle cerebral artery occlusion. Rats were injected intravenously with PBS, male allogeneic ACI – or syngeneic Wistar –bone marrow stromal cells at 24 h after ischemia and sacrificed at 28 days. Significant functional recovery was found in both cell-treated groups compared to stroke rats that did not receive BMSCs, but no difference was detected between allogeneic and syngeneic cell-treated rats. No evidence of T cell priming or humoral antibody production to marrow stromal cells was found in recipient rats after treatment with allogeneic cells. Similar numbers of Y-chromosome+ cells were detected in the female rat brains in both groups. Significantly increased thickness of individual axons and myelin, and areas of the corpus callosum and the numbers of white matter bundles in the striatum were detected in the ischemic boundary zone of cell-treated rats compared to stroked rats. The areas of the contralateral corpus callosum significantly increased after cell treatment compared to normal rats. Processes of astrocytes remodeled from hypertrophic star-like to tadpole-like shape and oriented parallel to the ischemic regions after cell treatment. Axonal projections emanating from individual parenchymal neurons exhibited an overall orientation parallel to elongated radial processes of reactive astrocytes of the cell-treated rats. Allogeneic and syngeneic bone marrow stromal cell treatment after stroke in rats improved neurological recovery and enhanced reactive oligodendrocyte and astrocyte related axonal remodeling with no indication of immunologic sensitization in adult rat brain.  相似文献   
26.
作者研究了高温流化α-化工艺中大米淀粉晶粒、水分、绝干淀粉含量、糊化率、脂肪含量、总氮和可降解氮的变化。研究表明:高温流化α-化后淀粉晶粒消失,成松散片状,比表面积增大,有利于酶的作用;水分含量低于10%,可有效防止淀粉老化和微生物污染;高温流化处理后淀粉糊化率与蒸饭法持平,而脂肪与可降解氮含量均明显下降,为酿造淡爽型酿造酒和提高酿造酒非生物性稳定性创造了机会。该工艺尤其适合在我国以糙米为原料的酿造酒生产中推广应用。  相似文献   
27.
28.
浆细胞病患者IL-4产生细胞数减少的意义及机制探讨   总被引:2,自引:0,他引:2  
侯健  王豫廉 《现代免疫学》1993,13(5):284-286
本文运用APAAP法检测了16名浆细胞患者外周血细胞在PHA刺激下产生IL-4的能力。发现浆细胞病组阳性细胞比率明显低于正常对照组(P<0.001),且阳性细胞比率与患者血清中多克隆IgM、IgA水平呈正相关(r=0.806和r=0.703)。在正常人外周血中加入CRP50mg/L,经PHA刺激后IL-4产生细胞也明显减少。作者假设,由于IL-6增高引起CRP等急性期相蛋白大量分泌,使IL-4产生受到明显抑制,从而使B细胞激活发生障碍是浆细胞病中多克隆免疫球蛋白合成抑制的主要原因。  相似文献   
29.
The importance of oxygen in maintaining the functional integrity of hepatocytes has been well established in a variety of experimental models, such as in vivo , perfused liver and isolated hepatocytes. However, one of the shortcomings of these systems is their short life span. Therefore, we have examined the effects of long-term hypoxia on cellular adenine nucleotide content and cellular functions, such as albumin production, urea production and DNA synthesis, in adult rat hepatocytes in primary culture. Hepatocytes were cultured at a density of 11 × 104 and 5 × 104 cells/0.18 mL per cm2 for the study of albumin and urea production and DNA synthesis, respectively, at various oxygen tensions (20, 12, 8 and 5%) for 24 h. Cellular ATP content in cultured hepatocytes in hypoxia gradually declined, corresponding to the decrease in oxygen tension, and the cellular ATP level at 5% oxygen was approximately 20% of that at 20% oxygen. Albumin production also decreased in parallel with the decrease in cellular ATP content in cultured hepatocytes in hypoxia. However, even when cellular ATP content gradually declined corresponding with the decrease in oxygen tension in cultured hepatocytes in hypoxia, such as at 8 or 5% oxygen, urea production remained at a high level; in contrast, DNA synthesis was completely suppressed. These results suggest that the cellular ATP content decreases in cultured hepatocytes during long-term hypoxia in relation to oxygen tension and that the relationship between decreased ATP levels and liver function in cultured hepatocytes during hypoxia differs for albumin production, urea production and DNA synthesis.  相似文献   
30.
A method for producing carrier free 66Ga (T1/2:9.4h; +) by 4He bombardment of natural copper targets is presented. 66Ga is formed by means of the 63Cu (4He, n) 66Ga reaction. Production yields are given in the 17.5 to 8 MeV 4He energy range. Chemical purification of 66Ga from the copper target is described. The only radionuclidic impurity found in the final product was 67Ga. Albumin colloids from commercially available kits designed for use with 99mTc could easily be labeled with 66Ga and employed for studies of the lymphatic system by positron emission tomography.  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