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   2575篇
  免费   156篇
  国内免费   4篇
耳鼻咽喉   17篇
儿科学   77篇
妇产科学   63篇
基础医学   364篇
口腔科学   37篇
临床医学   231篇
内科学   550篇
皮肤病学   58篇
神经病学   321篇
特种医学   73篇
外科学   335篇
综合类   14篇
预防医学   140篇
眼科学   42篇
药学   224篇
中国医学   10篇
肿瘤学   179篇
  2023年   12篇
  2022年   38篇
  2021年   82篇
  2020年   40篇
  2019年   48篇
  2018年   60篇
  2017年   60篇
  2016年   53篇
  2015年   85篇
  2014年   91篇
  2013年   115篇
  2012年   179篇
  2011年   180篇
  2010年   87篇
  2009年   103篇
  2008年   156篇
  2007年   144篇
  2006年   128篇
  2005年   124篇
  2004年   116篇
  2003年   108篇
  2002年   116篇
  2001年   52篇
  2000年   30篇
  1999年   29篇
  1998年   21篇
  1996年   22篇
  1995年   13篇
  1994年   9篇
  1992年   19篇
  1991年   22篇
  1990年   19篇
  1989年   26篇
  1988年   25篇
  1987年   18篇
  1986年   21篇
  1985年   23篇
  1984年   17篇
  1983年   18篇
  1982年   12篇
  1981年   16篇
  1980年   11篇
  1979年   8篇
  1978年   14篇
  1977年   14篇
  1975年   10篇
  1974年   10篇
  1973年   10篇
  1968年   13篇
  1957年   10篇
排序方式: 共有2735条查询结果,搜索用时 46 毫秒
81.

Background

Using array techniques, it was recently shown that about 10% of patients with mental retardation of unknown origin harbour cryptic chromosomal aneusomies. However, data analysis is currently not standardised and little is known about its sensitivity and specificity.

Methods

We have developed an electronic data analysis tool for gene‐mapping SNP arrays, a software tool that we call Copy Number Variation Finder (CNVF). Using CNVF, we analysed 104 unselected patients with mental retardation of unknown origin with a genechip mapping 100K SNP array and established an optimised set of analysis parameters.

Results

We detected deletions as small as 20 kb when covered by at least three single‐nucleotide polymorphisms (SNPs) and duplications as small as 150 kb when covered by at least six SNPs, with only one false‐positive signal in six patients. In 9.1% of patients, we detected apparently disease‐causing or de novo aberrations ranging in size from 0.4 to 14 Mb. Morphological anomalies in patients with de novo aberrations were equal to that of unselected patients when measured with de Vries score.

Conclusion

Our standardised CNVF data analysis tool is easy to use and has high sensitivity and specificity. As some genomic regions are covered more densely than others, the genome‐wide resolution of the 100K array is about 400–500 kb for deletions and 900–1000 kb for duplications. The detection rate of about 10% of de novo aberrations is independent of selection of patients for particular features. The incidental finding in two patients of heterozygosity for the 250 kb recurrent deletion at the NPH1 locus, associated with autosomal recessive juvenile nephronophthisis, which was inherited from a healthy parent, highlights the fact that inherited aberrations might be disease‐related even though not causal for mental retardation.  相似文献   
82.

Objectives

To evaluate college-age women’s knowledge of appropriate doses and potential toxicities of acetaminophen, competency in interpreting Drug Facts label dosing information, and ability to recognize products containing acetaminophen.

Methods

In this cross-sectional prospective study, a 20-item written survey was provided to female college students at a University of Michigan fundraising event in March 2015.

Results

A total of 203 female college students, 18-24 years of age, participated in the study. Pain was experienced on a daily or weekly basis by 22% of the subjects over the previous 6 months, and 83% reported taking acetaminophen. The maximum 3-gram daily dose of extra-strength acetaminophen was correctly identified by 64 participants; an additional 51 subjects indicated the generally accepted 4 grams daily as the maximum dose. When provided with the Tylenol Drug Facts label, 68.5% correctly identified the maximum amount of regular-strength acetaminophen recommended for a healthy adult. Hepatotoxicity was associated with high acetaminophen doses by 63.6% of participants, significantly more than those who selected distracter responses (P < 0.001). Knowledge of liver damage as a potential toxicity was correlated with age 20 years and older (P < 0.001) but was independent from race and ethnicity and level of alcohol consumption. Although more than one-half of the subjects (58.6%) recognized that Tylenol contained acetaminophen, fewer than one-fourth correctly identified other acetaminophen-containing products.

Conclusion

Despite ongoing educational campaigns, a large proportion of the college-age women who participated in our study did not know and could not interpret the maximum recommended daily dose from Drug Facts labeling, did not know that liver damage was a potential toxicity of acetaminophen, and could not recognize acetaminophen-containing products. These data suggest a continued role for pharmacists in educational efforts targeted to college-age women.  相似文献   
83.
International Urology and Nephrology - The association between end-stage renal disease and cardiovascular mortality may be influenced through vascular alterations, in particular atherosclerosis and...  相似文献   
84.
Neurosurgical Review - Indications for surgery of pineal cysts without ventriculomegaly are still under debate. In view of the limited data for pineal cyst resection in the absence of...  相似文献   
85.
Realheart total artificial heart (TAH) is a novel, pulsatile, four-chamber total artificial heart which had been successfully tested acutely in a porcine animal model. However, the bovine model is better suited for long-term testing and thus an evaluation of how the design would fit the bovine anatomy was required. Virtual implantation is a method that enables a computer simulated implantation based on anatomical 3D-models created from computer tomography images. This method is used clinically, but not yet adopted for animal studies. Herein, we evaluated its suitability in the redesign of the outer dimensions and vessel connections of Realheart TAH to transition from the porcine to the bovine animal model. Virtual implantations in combination with bovine cadaver studies enabled a series of successful acute bovine implantations. Virtual implantations are a useful tool to replace the use of animals in early device development and refine subsequent necessary in vivo experiments. The next steps are to carry out human virtual implantations and cadaver studies to ensure the design is optimized for all stages of testing as well as the final recipient.  相似文献   
86.
87.
88.
89.
The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.  相似文献   
90.
Background & Aims: Interleukin (IL)-15 has been found to share many immunoregulatory activities in lymphocytes with IL-2. The aim of this study was to investigate IL-15 activity in organ cultures, localization of IL-15 messenger RNA (mRNA), and proliferation of lamina propria mononuclear cells (LPMCs) in response to recombinant IL-15 using the mucosal tissues obtained from patients with inflammatory bowel disease (IBD). Methods: The contents of IL-15, tumor necrosis factor α, and IL-2 in the culture supernatant of the rectal mucosal tissues were determined by an enzyme-linked immunosorbent assay. Expression of IL-15 mRNA was analyzed by in situ hybridization, and proliferative response of LPMCs to recombinant IL-15 was determined by [3H]thymidine incorporation into DNA. Results: Significantly greater IL-15 activity was detected in active IBD, and this elevation was also observed in inactive ulcerative colitis. In contrast, greater tumor necrosis factor α activity was observed only in active IBD, and IL-2 was not detected in organ cultures. In situ hybridization showed IL-15 mRNA in macrophages and epithelial cells in active IBD specimens, and recombinant IL-15 induced a dose-dependent proliferative response in LPMCs. Conclusions: Mucosal IL-15 may be involved in the pathogenesis of IBD as one of the important mediators in activation of mucosal immune cells.GASTROENTEROLOGY 1998;114:1237-1243  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