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   3205篇
  免费   112篇
  国内免费   24篇
耳鼻咽喉   44篇
儿科学   94篇
妇产科学   89篇
基础医学   367篇
口腔科学   89篇
临床医学   261篇
内科学   631篇
皮肤病学   24篇
神经病学   172篇
特种医学   114篇
外科学   532篇
综合类   156篇
预防医学   207篇
眼科学   120篇
药学   212篇
  1篇
中国医学   35篇
肿瘤学   193篇
  2024年   4篇
  2023年   8篇
  2022年   8篇
  2021年   16篇
  2020年   14篇
  2019年   9篇
  2018年   4篇
  2017年   3篇
  2016年   4篇
  2015年   7篇
  2014年   12篇
  2013年   23篇
  2012年   312篇
  2011年   313篇
  2010年   74篇
  2009年   61篇
  2008年   274篇
  2007年   290篇
  2006年   288篇
  2005年   232篇
  2004年   239篇
  2003年   207篇
  2002年   206篇
  2001年   152篇
  2000年   176篇
  1999年   76篇
  1998年   18篇
  1997年   5篇
  1996年   8篇
  1995年   11篇
  1994年   8篇
  1993年   4篇
  1992年   3篇
  1990年   3篇
  1982年   5篇
  1981年   3篇
  1980年   4篇
  1963年   3篇
  1959年   20篇
  1958年   33篇
  1957年   43篇
  1956年   39篇
  1955年   34篇
  1954年   27篇
  1949年   7篇
  1948年   14篇
  1944年   2篇
  1943年   2篇
  1942年   2篇
  1938年   3篇
排序方式: 共有3341条查询结果,搜索用时 15 毫秒
21.
BACKGROUND: We investigated the effect of alpha-lipoic acid (LA) on reperfusion injury in a rat ovarian torsion-detorsion model. The changes in tissue and plasma levels of malondialdehyde (MDA), end-product of lipid peroxidation, superoxide dismutase (SOD), xanthine oxidase (XO) and nitric oxide (NO), were determined. Ovarian histopathological findings were scored and compared among groups. MATERIALS AND METHODS: Thirty-two female Sprague-Dawley rats were divided into four groups. Sham operation was performed in group I; in group II only ovarian torsion was performed. Group III received intraperitoneal injections of saline, and group IV received LA via intraperitoneal injections (LA group: aqueous solution at 36 mg/kg of body weight per day, saline group: equal volume of saline) 21, nine, and one hour before torsion of the ovary. Rats in the torsion group were killed after 360 degrees clockwise adnexial torsion for three hours, and ovaries were harvested. After three hours of adnexial detorsion, the rats in saline group and LA group were killed and adnexa were surgically removed. RESULTS: Ovarian tissue damage scores were significantly different among groups and were seen to correlate with tissue MDA levels. Ovarian tissue and serum MDA, NO and serum XO levels in the group III were significantly higher than those of the groups I and IV (P<0.05). The serum levels of SOD in the group III were significantly lower than those of the groups I and IV (P<0.05). CONCLUSION: These results suggest that LA pretreatment has beneficial effects in the prevention of ischaemia-reperfusion injury of the ovaries.  相似文献   
22.
BACKGROUND: Hyperphagic obese Zucker rats develop glomerular injury and die of renal disease, an outcome prevented by food restriction at an early age. We examined the effects of food restriction imposed at different ages on systemic, renal hemodynamic, and hormonal changes to gain insight into the mechanisms of obesity-linked glomerular injury. METHODS: At 6 weeks of age obese Zucker rats were either fed ad libitum or were restricted in food intake at various ages (6, 12, 26, or 50 weeks) to that consumed by lean Zucker rats (14 g/day). Every four weeks 24-hour urine collections, blood pressure, and venous blood samples were obtained until the end of study (60 weeks). RESULTS: Food restriction at 6 or 12 weeks of age prevented glomerular injury and hypertrophy and delayed the development of hypertension, hypercholesterolemia, and hyperinsulinemia. Food restriction at 26 weeks of age reduced proteinuria, while restriction at 50 weeks prevented further increases in proteinuria without altering pre-existing hypercholesterolemia, hypertension, or hyperinsulinemia. Hypertriglyceridemia and glomerular hyperfiltration in the obese animals were reversed at any age by food restriction. Plasma leptin levels were elevated in all obese groups. CONCLUSIONS: (1) Early food restriction provided the greatest metabolic and renal benefits; (2) glomerular injury correlated with hyperphagia-induced hyperfiltration and hypertriglyceridemia and both were prevented by food restriction; (3) hypercholesterolemia was due to an increase in LDL and/or VLDL cholesterol; and (4) leptin does not directly contribute to glomerular injury in the obese Zucker rat.  相似文献   
23.
Hon SS  Ng SS  Chiu PW  Chan FK  Ng EK  Li JC  Lee JF  Leung KL 《Surgical endoscopy》2011,25(12):3923-3927

Background  

Transanal local excision (LE) is a well-established treatment option for early rectal neoplasms not amenable to complete colonoscopic removal. Endoscopic submucosal dissection (ESD) has been introduced recently as a novel procedure that enables en bloc resection of large rectal neoplasms. To date, no report comparing the two approaches can be found in the literature. This study aimed to compare the short-term clinical outcomes between ESD and LE for early rectal neoplasms.  相似文献   
24.
Short- and long-term results of isolated selective proximal vagotomy (SPV) performed at non-complicated duodenal ulcer and SPV with duodenoplastic and drainage surgeries at ulcerous pyloroduodenal stenosis were analyzed. Principles of choice of duodenoplastic and drainage surgeries are discussed. Six variants of duodenoplasty is used depending on anatomic characteristics and localization of stenosis. Advantage of duodenoplasty over drainage surgeries is demonstrated. It is concluded that SPV with duodenoplasty should be regarded as surgical method of choice at the treatment of ulcerous duodenal stenosis because of low rate of stomach and duodenum functional disorders at long-term period after surgery.  相似文献   
25.
Urothelial carcinoma of the urinary bladder (UCB) is a highly heterogeneous malignancy that causes significant morbidity and mortality. Despite advances in surgical and medical treatment, there has been no change in mortality in UCB over the past decades. Standard pathological features (stage, grade, nodal status) provide only limited information regarding biological potential and clinical behavior. Molecular biomarkers may shed light on important mechanisms of pathogenesis, provide useful additional prognostic information, and serve as targets for therapy. This review summarizes recent advances and the most promising UCB tissue and blood biomarkers of the past few years. We discuss the predictive and prognostic value of biomarkers at different stages of UCB. There is no doubt that a panel of biomarkers will eventually improve our clinical decision-making with regard to treatment and follow-up.  相似文献   
26.
BackgroundAcute allograft rejection is dependent on adaptive immunity, but it is unclear whether the same is true for chronic rejection. Here we asked whether innate immunity alone is sufficient for causing chronic rejection of mouse cardiac allografts.MethodsWe transplanted primarily vascularized cardiac grafts to recombinase activating gene-knockout (RAG?/?) mice that lack T and B cells but have an intact innate immune system. Recipients were left unmanipulated, received adjuvants that stimulate innate immunity, or were reconstituted with B-1 lymphocytes to generate natural IgM antibodies. In a second model, we transplanted cardiac allografts to mice that lack secondary lymphoid tissues (splenectomized aly/aly recipients) and studied the effect of NK cell inactivation on T cell-mediated chronic rejection.ResultsAcute cardiac allograft rejection was not observed in any of the recipients. Histological analysis of allografts harvested 50 to 90 days after transplantation to RAG?/? mice failed to identify chronic vascular or parenchymal changes beyond those observed in control syngeneic grafts. Chronic rejection of cardiac allografts parked in splenectomized aly/aly mice was observed only after the transfer of exogenously activated T cells. NK inactivation throughout the experiment, or during the parking period alone, reduced the severity of T cell-dependent chronic rejection.ConclusionsThe innate immune system alone is not sufficient for causing chronic rejection. NK cells predispose healed allografts to T cell-dependent chronic rejection and may contribute to chronic allograft pathology.  相似文献   
27.
28.
The anaesthesiologist's competence in anaesthesia, intensive care medicine, pain therapy and emergency medicine is accepted throughout the medical society. Nevertheless, during the last decades patient surveys demonstrated a considerable lack of information of the responsibility of our work. By continuous education and information anaesthesiologists have aimed to improve the information and decision-making process for the patient. This multicentre trial was designed to investigate the current public view on our profession in seven German hospitals. In-hospital patients were asked to fill out a standardised questionnaire prior to the anaesthesia premedication visit and a total of 692 questionnaires (77%) were analysed. Results demonstrated an increased level of knowledge for anaesthesia (>95%), intensive care medicine (74%), and pain therapy (50% acute pain; 32% severe pain). In the case of emergency medicine (10%) the in-hospital and out-of-hospital responsibilities were not clear among patients. We conclude that the continuous distribution of information in recent years has contributed to improving patients' knowledge on interdisciplinary responsibilities. Future efforts should focus on the gaps in patient's knowledge to allow the patient to ask the right questions necessary for decision-making.  相似文献   
29.
Hemodialysis (HD) patients who are identified as belonging to racial or ethnic minority groups have longer survival than non-Hispanic white HD patients. This study sought to determine to what extent this survival difference is explained by comprehensive adjustment for measurable case-mix and treatment characteristics. A cohort analysis was conducted among 6677 patients between 1996 and 2001 in the American arm of the first phase of the Dialysis Outcomes and Practice Patterns Study, a prospective observational study. Using multivariable proportional hazards analysis, all-cause mortality by racial/ethnic category was compared before and after adjustment for other patient-level variables that are associated with mortality. Factors that influence the statistical associations of race/ethnicity with mortality were explored. The statistically significant (P < 0.001) associations of racial/ethnic minority categories with lower mortality in unadjusted analyses were attenuated or lost in the multivariable model. Compared with non-Hispanic white patients, the adjusted hazard ratio (HR) (95% confidence interval [CI]) for mortality was 0.86 (0.72 to 1.03) for Hispanic patients; among non-Hispanic patients, the HR (95% CI) were 0.97 (0.85 to 1.11) for black patients, 0.82 (0.56 to 1.20) for Asian patients, 0.95 (0.52 to 1.73) for Native American patients, and 0.95 (0.60 to 1.50) for patients of other races (overall P = 0.66). The survival advantages for racial/ethnic minority categories were explained most notably by the combined influence of unbalanced distributions of numerous demographic, morbidity, nutritional, and laboratory variables. The associations of race/ethnicity with survival varied little by duration of ESRD and were not influenced substantially by different rates of kidney transplantation among patients who were on HD. The survival advantages for racial and ethnic minority groups on HD are explained largely by measurable case-mix and treatment characteristics. Individual racial minority group or Hispanic patients should not be expected to survive longer on HD than non-Hispanic white patients with similar clinical attributes.  相似文献   
30.
Analysis of hypermutation of the 5’ noncoding region in the BC L-6 gene   总被引:3,自引:0,他引:3  
Objective To investigate BCL-6 gene mutations in Chinese populations with B-cell non- Hodgkin’s lymphoma.Methods Polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE) and direct DNA sequencing were used to identify mutations in the 5’ noncoding re gion of the BCL-6 gene in a total of 40 cases of diffuse large-cell lymphoma ( DLCL) and follicular lymphoma (FL).Results Nine cases were found to have base substitutions.The incidence of BCL-6 gene mutation and the frequency of single-base changes were approximately 25.7% an d (0.56-1.10)×10(-2)/bp, respectively.Conclusions The 5’ regulatory region of the BCL-6 gene undergoes frequent somatic hypermuta tion during lymphomagenesis and the identification of BCL-6 gene hypermutations provides a molecular marker for confirmatory diagnosis of B-NHL.  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