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   941篇
  免费   60篇
  国内免费   4篇
耳鼻咽喉   7篇
儿科学   20篇
妇产科学   29篇
基础医学   147篇
口腔科学   32篇
临床医学   49篇
内科学   275篇
皮肤病学   35篇
神经病学   60篇
特种医学   57篇
外科学   103篇
综合类   15篇
预防医学   68篇
眼科学   7篇
药学   58篇
中国医学   1篇
肿瘤学   42篇
  2023年   4篇
  2022年   6篇
  2021年   10篇
  2020年   14篇
  2019年   16篇
  2018年   17篇
  2017年   13篇
  2016年   21篇
  2015年   26篇
  2014年   32篇
  2013年   34篇
  2012年   38篇
  2011年   39篇
  2010年   43篇
  2009年   37篇
  2008年   46篇
  2007年   42篇
  2006年   50篇
  2005年   49篇
  2004年   57篇
  2003年   51篇
  2002年   37篇
  2001年   36篇
  2000年   29篇
  1999年   25篇
  1998年   31篇
  1997年   22篇
  1996年   16篇
  1995年   10篇
  1994年   10篇
  1993年   12篇
  1992年   8篇
  1991年   9篇
  1990年   15篇
  1989年   15篇
  1988年   16篇
  1987年   6篇
  1986年   10篇
  1985年   4篇
  1984年   5篇
  1983年   5篇
  1982年   3篇
  1981年   5篇
  1979年   5篇
  1976年   5篇
  1975年   4篇
  1974年   3篇
  1973年   2篇
  1971年   2篇
  1969年   2篇
排序方式: 共有1005条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
5.
The objective of this study was the in vitro differentiation of isolates of Salmonella enteritidis whose virulences differed in a chick model. A total of 14 strains of S. enteritidis were isolated from either the environment, dairy products, or infected patients. The isolates could be divided into two groups on the basis of their virulence (50% lethal dose) in chickens infected intraperitoneally. When the strains were incubated in adherence test medium (Spanish patent 9700408), only the virulent strains produced aggregates and formed visible filaments attached to the glass tube. These results suggest, although for a limited number of strains, that aggregation in such a medium could be used as a diagnostic tool to discriminate virulent strains of S. enteritidis.  相似文献   
6.

Background  

Painless, rapid, controlled, minimally invasive molecular transport across human skin for drug delivery and analyte acquisition is of widespread interest. Creation of microconduits through the stratum corneum and epidermis is achieved by stochastic scissioning events localized to typically 250 μm diameter areas of human skin in vivo.  相似文献   
7.
In order to evaluate nutritional status by anthropometry, a group of elderly (60 to 83 years old) was studied: 63 institutionalized and 37 non-institutionalized elderly from Valencia city, Venezuela. Weight, height, triceps skinfold and mid-arm circumference were measured and the body mass index (weight/height2) was calculated. The average age for the institutionalized group was 77.3 +/- 7.5 years old and 69.5 +/- 7.6 years old for the free-living elderly group. Tricipital skinfold (TSF) and mid-arm circumference (MAC) means were within the normal reference range for both groups, without significant differences by sex. Body mass index (BMI) was higher in the institutionalized group. Lower BMI and MAC were found in older elderly (> or =80 y). According to the nutritional classification by BMI, 16% of nutritional deficit, 45% of normal status and 39.7% with of excess weight were found in institutionalized elderly; while in free-living elderly, prevalences were 8%, 62% and 29.7% respectively. Even though normal nutritional status was highly prevalent, institutionalized elderly showed higher prevalences of nutritional alterations (underweight and overweight).  相似文献   
8.
An automatic colour image segmentation and cell counting software system has been developed for immunocytochemical analysis of stained tissue samples. The system was designed to count the total number of positive and negative cells in tissue samples treated with cytokine DNA probes from pigs naturally parasitised with Taenia solium metacestodes, using in situ hybridisation. A reaction index was calculated as the ratio of the number of cells with a positive reaction to the total number of cells (positives plus negatives) for each of five different probes. The objectives of automatic counting were to improve the reproducibility of the analysis and reduce the processing time of large image batches. A fast KNN classifier was used for colour segmentation. Watershed segmentation combined with edge detection was used to isolate individual cells that were then automatically labelled, using the results of the corresponding colour segmented image. Validation was performed on 122 non-training digital images with a total of 1069 positive cells and 1459 negative cells, with the following results: a mean true positive rate of 90.2% for positive cells and a mean true positive rate of 85.4% for negative cells. The corresponding mean false positive rates were 9.6% and 6.6%. The mean reaction index error of the automatic analysis was 5.35%. The processing of each digital image took 10 s on a Pentium IV PC.  相似文献   
9.

Background  

Assessment of cerebral blood flow (CBF) by SPECT could be important in the management of patients with severe traumatic brain injury (TBI) because changes in regional CBF can affect outcome by promoting edema formation and intracranial pressure elevation (with cerebral hyperemia), or by causing secondary ischemic injury including post-traumatic stroke. The purpose of this study was to establish an improved method for evaluating regional CBF changes after TBI in piglets.  相似文献   
10.
The net impact of cytomegalovirus (CMV) DNAemia on overall mortality (OM) and nonrelapse mortality (NRM) following allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a matter of debate. This was a retrospective, multicenter, noninterventional study finally including 749 patients. CMV DNA monitoring was conducted by real-time polymerase chain reaction (PCR) assays. Clinical outcomes of interest were OM and NRM through day 365 after allo-HSCT. The cumulative incidence of CMV DNAemia in this cohort was 52.6%. A total of 306 out of 382 patients with CMV DNAemia received preemptive antiviral therapy (PET). PET use for CMV DNAemia, but not the occurrence of CMV DNAemia, taken as a qualitative variable, was associated with increased OM and NRM in univariate but not in adjusted models. A subcohort analysis including patients monitored by the COBAS Ampliprep/COBAS Taqman CMV Test showed that OM and NRM were comparable in patients in whom either low or high plasma CMV DNA threshold (<500 vs ≥500 IU/mL) was used for PET initiation. In conclusion, CMV DNAemia was not associated with increased OM and NRM in allo-HSCT recipients. The potential impact of PET use on mortality was not proven but merits further research.  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