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   3385篇
  免费   227篇
  国内免费   5篇
耳鼻咽喉   57篇
儿科学   134篇
妇产科学   93篇
基础医学   480篇
口腔科学   126篇
临床医学   323篇
内科学   638篇
皮肤病学   26篇
神经病学   264篇
特种医学   101篇
外科学   349篇
综合类   24篇
一般理论   4篇
预防医学   298篇
眼科学   61篇
药学   356篇
中国医学   1篇
肿瘤学   282篇
  2023年   16篇
  2022年   32篇
  2021年   44篇
  2020年   52篇
  2019年   72篇
  2018年   88篇
  2017年   67篇
  2016年   98篇
  2015年   99篇
  2014年   113篇
  2013年   183篇
  2012年   238篇
  2011年   220篇
  2010年   135篇
  2009年   137篇
  2008年   234篇
  2007年   238篇
  2006年   249篇
  2005年   193篇
  2004年   194篇
  2003年   160篇
  2002年   179篇
  2001年   24篇
  2000年   17篇
  1999年   24篇
  1998年   43篇
  1997年   40篇
  1996年   54篇
  1995年   27篇
  1994年   27篇
  1993年   26篇
  1992年   18篇
  1991年   19篇
  1990年   22篇
  1989年   19篇
  1988年   17篇
  1987年   13篇
  1986年   18篇
  1985年   19篇
  1984年   16篇
  1983年   9篇
  1982年   8篇
  1980年   7篇
  1979年   13篇
  1978年   15篇
  1977年   10篇
  1975年   10篇
  1972年   7篇
  1969年   5篇
  1966年   7篇
排序方式: 共有3617条查询结果,搜索用时 15 毫秒
41.

Objective

To examine how cardiorespiratory fitness and self-perceived stress are associated with burnout and depression. To determine if any relationship between stress and burnout/depression is mitigated among participants with high fitness levels.

Methods

197 participants (51% men, mean age = 39.2 years) took part in the study. The Åstrand bicycle test was used to assess cardorespiratory fitness. Burnout was measured with the Shirom–Melamed Burnout Questionnaire (SMBQ), depressive symptoms with the Hospital Anxiety and Depression Scale (HAD-D). A gender-matched stratified sample was used to ensure that participants with varying stress levels were equally represented.

Results

Participants with moderate and high fitness reported fewer symptoms of burnout and depression than participants with low fitness. Individuals with high stress who also had moderate or high fitness levels reported lower scores on the SMBQ Tension subscale and the HAD-D than individuals with high stress, but low fitness levels.

Conclusion

Better cardiovascular fitness seems to be associated with decreased symptoms of burnout and a better capacity to cope with stress.

Practical implications

Promoting and measuring cardiorespiratory fitness can motivate employees to adopt a more physically active lifestyle and thus strengthen their ability to cope with stress exposure and stress-related disorders.  相似文献   
42.
We investigated the epidermal growth factor receptor (EGFR) status in early stage lung cancer in Southern Sweden, a population for which there are no previous reports on the EGFR mutation frequency. Three hundred fifty small cell lung cancers, adenocarcinomas (AC), squamous cell carcinomas (SqCC), and large cell carcinomas were analyzed using a combination of techniques for the analysis of protein expression, gene copy numbers, and mutations. Immunohistochemical (IHC) staining with antibodies for the EGFR mutations L858R and del E746-A750 revealed intratumoral heterogeneity and several discrepant cases when compared to mutation-specific polymerase chain reaction (PCR)-based analysis. The frequencies of these two mutations, when considering IHC staining with mutation-specific antibodies in a cohort of 298 cases and subsequent confirmation by PCR, were 10 % in AC and <2 % in SqCC. Furthermore, screening by sequencing of EGFR in a cohort of 52 lung AC and squamous carcinomas demonstrated a more diverse mutation spectrum, not covered by the mutation-specific antibodies. High expression of total EGFR protein was correlated to high gene copy numbers but did not reflect the mutational status of the tumors. We believe that the mutation spectra in a Southern Swedish population is too diverse to be covered by the mutation-specific antibodies, and we also raise some other issues regarding the use of the mutation-specific antibodies, for example concerning heterogeneous expression of the mutated protein, optimal antibody dilution, and discrepancies between staining results and PCR.  相似文献   
43.
44.
45.
46.
In this single-center study, we retrospectively analyzed incidenceand risk factors for hepatic veno-occlusive disease (VOD) in 249 consecutive patients who underwent allogeneic hematopoietic stem celltransplantation between January 1990 and June 1995. Twenty-four of the249 transplanted patients developed VOD. The probabilities ofdeveloping VOD were 17% among women and 7% in men (P = .01). In women treated with norethisterone, the incidence was 27%compared with 3% in women without this treatment (P = .007).One-year survival rates were 17% and 73% in patients with (n = 24)or without VOD (n = 225), respectively. The use of heparin prophylaxis (100 IE/kg/24 hours for 1 month) did not alter the incidence or 1-year mortality of VOD. In multivariate analysis, thefollowing risk factors were significant: norethisterone treatment (P < .001), bilirubin >26 µmol/L before bone marrowtransplantation (BMT) (P = .002), one HLA-antigen mismatch(P = .003), previous abdominal irradiation (P = .02), and conditioning with busulphan (P = .02). Ourconclusion is that norethisterone treatment should not be used inpatients undergoing BMT and heparin prophylaxis did not affect theincidence or mortality of VOD.  相似文献   
47.

Background

Somatostatin acts through five receptor subtypes (SSTRs 1–5). We aimed to investigate SSTRs mRNA expression and protein distribution in whole rat embryos, with special emphasis on the pancreas.

Material and methods

Rat embryos were collected on embryonal days 10, 11, 12, 14, 15, 17, 19, 21, and at birth. Presence of SSTRs was investigated with RT-PCR techniques and immunohistochemistry.

Results

There was no SSTR5 mRNA expression in the whole rat embryos. All SSTR1–5 proteins were observed at embryonal day 10, but the localization varied between the different subtypes. From day 11 to birth SSTRs protein presence increased with time in major structures such as skin and cartilage. It remained similar over time in the heart and liver. In the fetal pancreas mRNA expression of SSTR2 and 4 was detected at day 14, and there was an increase up to birth. Only SSTR1 protein co-localized to a higher extent with the islet hormones studied. SSTR2 was present in all islet endocrine cells except for β-cells. In contrast, the immunostaining for SSTR3–4 was co-localized with insulin and PP, and, finally, SSTR5 with glucagon and pancreatic polypeptide. In mRNA isolated from whole rat embryos SSTR1-2 and SSTR4 expression showed a peak at day 14, while SSTR3 mRNA was not present until day 15.

Conclusion

The present data suggest a role for SSTRs during the development of the rat embryo. Subsequent functional studies may elucidate regulatory roles of specific SSTRs for the growth and differentiation of the pancreas as well as other organs.  相似文献   
48.
49.
50.

Background

Elevated IgG4 levels have been reported among patients with primary sclerosing cholangitis. Epidemiological data has only been provided from tertiary centres.

Aims

To investigate the prevalence of elevated IgG4 levels and to compare prognosis between patients with and without elevated IgG4 levels in serum in two European cohorts of patients with primary sclerosing cholangitis.

Methods

Serum IgG4-levels were measured in a consecutive series of patients from Berlin, and retrospectively collected in a population-based cohort from Sweden (total N = 345). Cox's proportional hazard analysis was used to calculate relative risks for liver-related death or liver transplantation and cholangiocarcinoma.

Results

Elevated IgG4 values were demonstrated in 10% of patients. A previous history of pancreatitis, combined intra- and extrahepatic biliary involvement and jaundice were independently associated with elevated IgG4 in multivariate analysis. IgG4 status was not associated with an increased risk for the combined endpoint liver-related death or liver transplantation or cholangiocarcinoma.

Conclusion

The prevalence of elevated IgG4 values among European patients with primary sclerosing cholangitis is similar to what previously has been reported from the United States. Elevated IgG4 was not associated with an increased risk of liver transplantation or liver-related death or cholangiocarcinoma.  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