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   675篇
  免费   49篇
  国内免费   64篇
耳鼻咽喉   1篇
儿科学   46篇
妇产科学   7篇
基础医学   106篇
口腔科学   16篇
临床医学   114篇
内科学   171篇
皮肤病学   15篇
神经病学   17篇
特种医学   87篇
外科学   57篇
综合类   19篇
预防医学   43篇
眼科学   5篇
药学   46篇
中国医学   2篇
肿瘤学   36篇
  2022年   4篇
  2021年   6篇
  2020年   4篇
  2019年   9篇
  2018年   11篇
  2017年   6篇
  2016年   13篇
  2015年   13篇
  2014年   24篇
  2013年   27篇
  2012年   12篇
  2011年   17篇
  2010年   29篇
  2009年   31篇
  2008年   30篇
  2007年   57篇
  2006年   22篇
  2005年   18篇
  2004年   18篇
  2003年   12篇
  2002年   14篇
  2001年   19篇
  2000年   11篇
  1999年   20篇
  1998年   40篇
  1997年   40篇
  1996年   26篇
  1995年   24篇
  1994年   30篇
  1993年   20篇
  1992年   8篇
  1991年   14篇
  1990年   4篇
  1989年   18篇
  1988年   21篇
  1987年   11篇
  1986年   6篇
  1985年   10篇
  1984年   7篇
  1983年   6篇
  1982年   10篇
  1981年   13篇
  1980年   8篇
  1979年   2篇
  1978年   7篇
  1977年   7篇
  1976年   10篇
  1975年   4篇
  1969年   3篇
  1968年   3篇
排序方式: 共有788条查询结果,搜索用时 15 毫秒
781.
SUMMARY The incidence of climacteric symptoms was determined in 247 healthy premenopausal women in a community setting. These volunteers had been recruited to a longitudinal study of bone density. Of these subjects, 46 ceased to menstruate during the study, and in this subgroup symptoms were compared before and after cessation of menstruation. Only hot flushes increased after cessation of menstruation in the longitudinal study and showed age correlation in the cross-sectional study. Hot flushes thus emerged as a true menopausal symptom. Although evidence for this is weaker, cold sweats and suffocation seem likely to be genuinely menopausal. Breast discomfort and the four mood symptoms of irritability, excitability, depression and poor concentration improved after cessation of menstruation, and this study gives no support for their being part of the menopausal syndrome; it suggests that these symptoms are more likely to be related to menstruation than to the menopause.  相似文献   
782.
Rowley  JD; Golomb  HM; Vardiman  JW 《Blood》1981,58(4):759-767
Cytogenetic studies were performed on 26 patients who developed acute nonlymphocytic leukemia (ANLL) or a dysmyelopoietic syndrome after treatment of a primary malignancy. Fifteen patients had radiotherapy and chemotherapy, seven had only chemotherapy, and four had only radiotherapy. The median times from diagnosis of the initial disease to the development of bone marrow dysfunction for these treatment groups were 50, 46, and 49 mo, respectively. Twenty-five patients had an abnormal karyotype in myeloid cells. Loss of part or all of no. 5 and/or no. 7 was noted in 23 of 25 patients with aneuploidy. Loss of no. 5 was noted only in patients who previously had malignant lymphoma, whereas loss of no. 7 was seen in these patients as well as in those who had other malignancies. Abnormalities of both nos. 5 and 7 occurred in 53% of the patients treated with combined therapy and in only 27% of patients treated with either modality alone. Although these changes are distinctly different from those noted in lymphomas, they are similar to those seen in 25% of aneuploid patients with ANLL de novo.  相似文献   
783.
<正>To the Editor: Hypoxic hepatitis(HH), also known as ischemic hepatitis or shock liver, is a liver injury characterized by necrosis of centrilobular hepatocytes with a rapid increase in serum aminotransferase levels. The incidence rate of HH among patients in the intensive care unit(ICU) was found to be 0.9%-11.9% [1]. Occurrence of HH appears to have a significant impact on the clinical outcome.  相似文献   
784.

INTRODUCTION

This study specifically examined right colonic cancer resection, a common operation for colorectal surgeons starting laparoscopic resection, to assess the impact of commencing laparoscopy.

PATIENTS AND METHODS

A total of 56 patients undergoing open (n = 34) and attempted laparoscopic (n = 22) elective right hemicolectomy for colorectal cancer between November 2003 and March 2007 were compared. Postoperative stay was the primary outcome. Secondary outcomes included analgesic requirements, bowel recovery, morbidity and mortality. Frequency of laparoscopic versus open surgery over time was also examined.

RESULTS

Resections attempted laparoscopically increased from 9.1% to 75% in the first and last quarters of the study period, respectively (P = 0.0002). Uptake of ‘enhanced recovery’ was mainly in the laparoscopic group. Conversion was required in two of 22 patients. Attempted laparoscopic cases had a shorter median postoperative stay (6 vs 10 days; P < 0.0001), duration of parenteral or epidural analgesia (48 vs 72 h; P < 0.0001) and time to first bowel action (3 vs 4 days; P = 0.001) compared with open cases. Demography, tumour characteristics, morbidity and mortality were comparable between groups. Multivariate analysis identified decreased age, attempted laparoscopic surgery, use of enhanced recovery and absence of complications as independently shortening postoperative stay.

CONCLUSIONS

Advantages of laparoscopic surgery and enhanced recovery, even early in a surgeon''s experience, suggest this is the preferred mode for elective right colon cancer resection.  相似文献   
785.
Subjects with chronic obstructive pulmonary disease (COPD) have an increased risk of vertebral fractures (VFs); however, VF incidence is largely unknown. Therefore, the aim of our study was to determine the incidence of new and/or worsening VF in subjects with COPD. Smokers and subjects with COPD (GOLD II–IV) from the ECLIPSE study with complete set of chest CT scans (baseline and 1‐ and 3‐year follow‐up) to evaluate vertebrae T1 down to L1 were included. If a VF was diagnosed on the last scan, detailed VF assessment of the previous scans was performed. VFs were scored according to the method of Genant as mild, moderate, or severe. Main outcome measure was the cumulative incidence of new and/or worsening VF at subject level, within 1 and 3 years. Of 1239 subjects (mean age 61 years, 757 males [61%], 999 subjects with COPD), 253 (20.5%) had ≥1 prevalent VF. The cumulative incidence of VFs was 10.1% within 1 year and 24.0% within 3 years. After adjustment for age, sex, body mass index (BMI), pack‐years, and smoking status, prevalence and incidence were similar between smokers and COPD GOLD stages. Within 1 year, 29.2% of the subjects with a prevalent VF had an incident VF, compared with 5.1% in absence of prevalent VF (hazard ratio [HR] = 5.1; 95% confidence interval [CI] 3.6–7.4) and 58.5% versus 15.0% within 3 years (HR = 3.6; 95% CI 2.9–4.6). The incidence of VF was higher with increasing number and severity of prevalent VFs. Among subjects having an incident VF within the first year, 57.3% had a subsequent VF within the next 2 years. In this study, more than half of the smokers and subjects with COPD with a prevalent VF or an incident VF within the first year sustained a subsequent VF within 3 years. The 3‐year risk was even higher in the presence of multiple or severe prevalent VFs. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.  相似文献   
786.
Lorenz  HM; Lagoo  AS; Hardy  KJ 《Blood》1994,83(7):1862-1870
We recently reported that cross-linking the leukocyte common antigen (CD45) can rapidly induce aggregation of human peripheral blood mononuclear cells via lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) interactions. Herein, we have examined both T-cell--monocyte cellular interactions and the molecular signaling that are involved in this phenomenon. Experiments using highly purified T lymphocytes showed that CD45-induced aggregation requires the presence of both T cells and monocytes. Cross- linking CD45 only on T lymphocytes, but not on monocytes, initiated cellular clustering after reconstituting to the respective untreated cell type. By several criteria, CD45-induced clustering of T cells to autologous monocytes was shown to be Fc-receptor--independent. When comparing intracellular signaling in leukocyte aggregation induced by CD45 cross-linking versus phorbol myristate-12-13-acetate (PMA) treatment, the former was found to be fivefold to 10-fold more sensitive to H-8, a reagent that effectively blocks cAMP- and cGMP- dependent protein kinases. On the other hand, reagents that increase intracellular cAMP levels (eg, dbcAMP, forskolin, and IBMX), protein kinase C (PKC) inhibitors (eg, staurosporine), and tyrosine kinase inhibitors (eg, herbimycin A and genistein) all readily inhibited PMA- induced, but not CD45 monoclonal antibody-induced, aggregation. We conclude that cross-linking the leukocyte common antigen on T cells induces LFA-1--/ICAM-1--dependent T-cell--monocyte aggregation through a unique signaling pathway independent of PKC, which involves instead cAMP-/cGMP-dependent protein kinases.  相似文献   
787.
Ewing sarcoma (EWS) is a tumour most commonly arising in bone, although on occasion in soft tissue, with a poor prognosis in patients with refractory or relapsed disease, despite multimodal therapy. Immunotherapeutic strategies based on tumour‐reactive T and/or natural killer cells may improve the treatment of advanced‐stage EWS. Since cellular immune recognition critically depends on human leukocyte antigen (HLA) expression, knowledge about HLA expression in EWS is crucial in the design of cellular immunotherapeutic strategies. Constitutive and IFNγ‐induced HLA class I expression was analysed in EWS cell lines (n = 6) by flow cytometry, using antibodies against both monomorphic and allele‐specific antigens. Expression of antigen processing pathway components and beta‐2 microglobulin (β2m) was assessed by western blot. Expression of class II transactivator (CIITA), and its contribution to HLA class II expression, was evaluated by qRT‐PCR, transduction assays, and flow cytometry. β2m/HLA class I and class II expression was validated in EWS tumours (n = 67) by immunofluorescence. Complete or partial absence of HLA class I expression was observed in 79% of EWS tumours. Lung metastases consistently lacked HLA class I and sequential tumours demonstrated a tendency towards decreased expression upon disease progression. Together with absent or low constitutive expression levels of specific HLA class I loci and alleles, and differential induction of identical alleles by IFNγ in different cell lines, these results may reflect the existence of an immune escape mechanism. Inducible expression of TAP‐1/‐2, tapasin, LMP‐2/‐7, and the β2m/HLA class I complex by IFNγ suggests that regulatory mechanisms are mainly responsible for heterogeneity in constitutive class I expression. EWSs lack IFNγ‐inducible HLA class II, due to lack of functional CIITA. The majority of EWS tumours, particularly if advanced‐stage, exhibit complete or partial absence of both classes of HLA. This knowledge will be instrumental in the design of cellular immunotherapeutic strategies for advanced‐stage EWS. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.  相似文献   
788.
目的:合成依西美坦并改进合成工艺。方法:以雄甾烯一酮为原料,经Mannich反应、溴化、脱溴等数步反应制得依西美坦。结果:所得产物经元素分析。柴外光谱,红外光谱,核磁共振谱及质谱等确证了结构。结论:此路线是可行的。  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