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   818篇
  免费   52篇
  国内免费   3篇
耳鼻咽喉   3篇
儿科学   14篇
妇产科学   8篇
基础医学   107篇
口腔科学   21篇
临床医学   65篇
内科学   152篇
皮肤病学   18篇
神经病学   68篇
特种医学   14篇
外科学   87篇
综合类   9篇
预防医学   74篇
眼科学   117篇
药学   72篇
中国医学   10篇
肿瘤学   34篇
  2023年   5篇
  2022年   21篇
  2021年   19篇
  2020年   11篇
  2019年   28篇
  2018年   25篇
  2017年   20篇
  2016年   37篇
  2015年   32篇
  2014年   39篇
  2013年   46篇
  2012年   56篇
  2011年   85篇
  2010年   31篇
  2009年   27篇
  2008年   59篇
  2007年   66篇
  2006年   40篇
  2005年   44篇
  2004年   39篇
  2003年   43篇
  2002年   33篇
  2001年   6篇
  2000年   5篇
  1999年   8篇
  1998年   2篇
  1997年   3篇
  1996年   2篇
  1995年   2篇
  1994年   3篇
  1993年   5篇
  1992年   5篇
  1991年   9篇
  1989年   2篇
  1988年   3篇
  1987年   1篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1977年   1篇
  1976年   1篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
排序方式: 共有873条查询结果,搜索用时 187 毫秒
11.
12.
The aim of this study is to evaluate the effects of low-level laser therapy (LLLT) on (1) the velocity of orthodontic tooth movement and (2) the nitric oxide levels in gingival crevicular fluid (GCF) during orthodontic treatment. The sample consisted of 20 patients (14 girls, six boys) whose maxillary first premolars were extracted and canines distalized. A gallium-aluminum-arsenide (Ga-Al-As) diode laser was applied on the day 0, and the 3rd, 7th, 14th, 21st, and 28th days when the retraction of the maxillary lateral incisors was initiated. The right maxillary lateral incisors composed the study group (the laser group), whereas the left maxillary lateral incisors served as the control. The teeth in the laser group received a total of ten doses of laser application: five doses from the buccal and five doses from the palatal side (two cervical, one middle, two apical) with an output power of 20 mW and a dose of 0.71 J /cm2. Gingival crevicular fluid samples were obtained on the above-mentioned days, and the nitric oxide levels were analyzed. Bonferroni and repeated measures variant analysis tests were used for statistical analysis with the significance level set at p ≤ 0.05. The application of low-level laser therapy accelerated orthodontic tooth movement significantly; there were no statistically significant changes in the nitric oxide levels of the gingival crevicular fluid during orthodontic treatment.  相似文献   
13.
Some degree rotation of the gravid uterus in the third trimester of pregnancy is not an abnormal finding. However, extreme uterine torsion of 180° around its cervical junction is a relatively rare event in obstetrical practice. We report here such a case that detected at laparotomy for an emergency cesarean section due to rapture of amniotic membrane.  相似文献   
14.
15.
This study was undertaken to investigate factors associated with stereotypic behavior in stabled horses in Iran. We evaluated sex, age, breed, color, frequency of feeding in the day, social contact with other horses during stabling, and the design of stable. We divided the stable design into two groups: indoor stables and those where the horses had contact with the outside environment. No statistical relationship could be found between the factors examined and stereotypic behavior. However, we found trends relating age group (1–7 and >7 years), color (white and dun were over-represented), breed (Thoroughbred and Arabian horses were over-represented), and daily feeding frequency (twice over-represented compared with three times). Horses with tactile contact with others showed less stereotypy than those that had no tactile contact with neighbors. This study suggested that the most important factors in the occurrence of stereotypic behavior are social interaction with other horses and frequency of feeding. Stereotypies appear to be related to management factors.  相似文献   
16.
Cyclic neutropenia is a rare immunodeficiency syndrome, characterized by regular periodic oscillations in the circulating neutrophil count from normal to neutropenic levels through 3 weeks period, and lasting for 3-6 days. In order to determine the clinical features of cyclic neutropenia, this study was performed. Seven patients with cyclic neutropenia (3 males and 4 females), who experienced neutropenic periods every 3 weeks (5 with severe and 2 with moderate neutropenia), were investigated in this study. They had been referred to Iranian Primary Immunodeficiency Registry during 23 years (1980-2003). The range of patients' ages was from 7 to 13 years (median 11 years). The median age at the onset of the disease was 12 months (1 month- 2 years) and the median age of diagnosis was 2 (1.5-5) years, with a median diagnosis delay of 1 year (2 months- 5 years). Neutropenia was associated with leukopenia (3 patients), anemia (3 patients), and thrombocytopenia (1 patient). Patients were asymptomatic in healthy phase, but during the episode of neutropenia suffered from aphthous ulcers, abscesses and overwhelming infections. The most commonly occurred manifestations were: otitis media (6 cases), oral ulcers (5 cases), abscesses (4 cases), pneumonia (3 cases), diarrhea (3 cases), oral candidiasis (3 cases), cutaneous infections (2 cases), and periodontitis (2 cases). One of these patients subsequently died because of recurrent infections. Unusual, persistent or severe infections should be the initiating factors to search for an immune deficiency syndrome such as cyclic neutropenia, because a delay in diagnosis may result in chronic infection, irretrievable end-organ damage or even death of the patient.  相似文献   
17.
Clinical Rheumatology - MiRSNPs may interfere with mRNA stability through effects on microRNAs (miRNAs)-mRNA interactions via direct changes in miRNA binding site or effect on the secondary...  相似文献   
18.
Currently, the methods available for preimplantation genetic diagnosis (PGD) of in vitro fertilized (IVF) embryos do not detect de novo single-nucleotide and short indel mutations, which have been shown to cause a large fraction of genetic diseases. Detection of all these types of mutations requires whole-genome sequencing (WGS). In this study, advanced massively parallel WGS was performed on three 5- to 10-cell biopsies from two blastocyst-stage embryos. Both parents and paternal grandparents were also analyzed to allow for accurate measurements of false-positive and false-negative error rates. Overall, >95% of each genome was called. In the embryos, experimentally derived haplotypes and barcoded read data were used to detect and phase up to 82% of de novo single base mutations with a false-positive rate of about one error per Gb, resulting in fewer than 10 such errors per embryo. This represents a ∼100-fold lower error rate than previously published from 10 cells, and it is the first demonstration that advanced WGS can be used to accurately identify these de novo mutations in spite of the thousands of false-positive errors introduced by the extensive DNA amplification required for deep sequencing. Using haplotype information, we also demonstrate how small de novo deletions could be detected. These results suggest that phased WGS using barcoded DNA could be used in the future as part of the PGD process to maximize comprehensiveness in detecting disease-causing mutations and to reduce the incidence of genetic diseases.Worldwide, more than 5 million babies (Ferraretti et al. 2013) have been born through in vitro fertilization (IVF) since the birth of the first in 1978 (Steptoe and Edwards 1978). Exact numbers are difficult to determine, but it has been estimated that currently 350,000 babies are born yearly through IVF (de Mouzon et al. 2009, 2012; Centers for Disease Control and Prevention 2011; Ferraretti et al. 2013). That number is expected to rise, as advanced maternal age is associated with decreased fertility rates and women in developed countries continue to delay childbirth to later ages. In 95% of IVF procedures, no diagnostic testing of the embryos is performed (https://www.sartcorsonline.com/rptCSR_PublicMultYear.aspx?ClinicPKID=0). Couples with prior difficulties conceiving or those wishing to avoid the transmission of highly penetrant heritable diseases often choose to perform preimplantation genetic diagnosis (PGD). PGD involves the biopsy of one cell from a 3-d embryo or the recently more preferred method, due to improved implantation success rates (Scott et al. 2013b), of up to 10 cells from a 5- to 6-d blastocyst-stage embryo. Following biopsy, genetic analysis is performed on the isolated cell(s). Currently this is an assay for translocations and the correct chromosome copy number (Hodes-Wertz et al. 2012; Munne 2012; Yang et al. 2012; Scott et al. 2013a; Yin et al. 2013), a unique test designed and validated for each specific heritable disease (Gutierrez-Mateo et al. 2009), or a combination of both (Treff et al. 2013). Importantly, none of these approaches can detect de novo mutations.Advanced maternal age has long been associated with an increased risk of producing aneuploid embryos (Munne et al. 1995; Crow 2000; Hassold and Hunt 2009) and giving birth to a child afflicted with Down syndrome or other diseases resulting from chromosomal copy number alterations. Conversely, children of older fathers have been shown to have an increase in single base and short multibase insertion/deletion (indels) de novo mutations (Kong et al. 2012). Many recent large-scale sequencing studies have found that de novo variations spread across many different genes are likely to be the cause of a large fraction of autism cases (Michaelson et al. 2012; O’Roak et al. 2012; Sanders et al. 2012; De Rubeis et al. 2014; Iossifov et al. 2014), severe intellectual disability (Gilissen et al. 2014), epileptic encephalopathies (Epi4K Consortium and Epilepsy Phenome/Genome Project 2013), and many other congenital disorders (de Ligt et al. 2012; Veltman and Brunner 2012; Yang et al. 2013; Al Turki et al. 2014). Additionally rare and de novo variations have been suggested to be prevalent in patients with schizophrenia (Fromer et al. 2014; Purcell et al. 2014), and Michaelson et al. (2012) found that single base de novo mutations affect conserved regions of the genome and essential genes more often than regions of unknown function. Current targeted approaches to PGD would miss many of these important functional changes within the embryonic DNA sequence, and even a whole-genome sequencing (WGS)–based carrier screen of both parents would not enable comprehensive preimplantation or prenatal diagnoses due to de novo mutations. As more parents delay childbirth into their mid-30s and later, these studies suggest we should try to provide better diagnostic tests for improving the health of newborns. In this study, we demonstrate the use of an advanced WGS process that provides an accurate and phased genome sequence from about 10 cells, allowing highly sensitive and specific detection of single base de novo mutations from IVF blastocyst biopsies.  相似文献   
19.

Objective

To evaluate the effectiveness of exercise, ergonomic modification, and a combination of training exercise and ergonomic modification on the scores of pain in office workers with neck, shoulders, and lower back pain.

Methods

Participants (N = 142) in this randomized controlled trial were office workers aged 20–50 years old with neck, shoulders, and lower back pain. They were randomly assigned to either the ergonomic modification group, the exercise group, the combined exercise and ergonomic modification group, or the control group (no-treatment). The exercise training group performed a series of stretching exercises, while the ergonomic group received some modification in the working place. Outcome measures were assessed by the Cornell Musculoskeletal Disorders Questionnaire at baseline, after 2, 4, and 6 months of intervention.

Results

There was significant differences in pain scores for neck (MD ?10.55; 95%CI ?14.36 to ?6.74), right shoulder (MD ?12.17; 95%CI ?16.87 to ?7.47), left shoulder (MD ?11.1; 95%CI ?15.1 to ?7.09) and lower back (MD ?7.8; 95%CI ?11.08 to ?4.53) between the exercise and control groups. Also, significant differences were seen in pain scores for neck (MD ?9.99; 95%CI ?13.63 to ?6.36), right shoulder (MD ?11.12; 95%CI ?15.59 to ?6.65), left shoulder (MD ?10.67; 95%CI ?14.49 to ?6.85) and lower back (MD ?6.87; 95%CI ?10 to ?3.74) between the combined exercise and ergonomic modification and control groups. The significant improvement from month 4 to 6, was only seen in exercise group (p < 0.05).

Conclusion

To have a long term effective on MSDs, physical therapists and occupational therapists should use stretching exercises in their treatment programs rather than solely rely on ergonomic modification.
20.
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