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   3930篇
  免费   162篇
  国内免费   36篇
耳鼻咽喉   71篇
儿科学   109篇
妇产科学   218篇
基础医学   311篇
口腔科学   139篇
临床医学   317篇
内科学   885篇
皮肤病学   126篇
神经病学   222篇
特种医学   135篇
外科学   777篇
综合类   59篇
预防医学   127篇
眼科学   114篇
药学   193篇
中国医学   6篇
肿瘤学   319篇
  2024年   3篇
  2023年   27篇
  2022年   56篇
  2021年   70篇
  2020年   46篇
  2019年   72篇
  2018年   111篇
  2017年   70篇
  2016年   118篇
  2015年   126篇
  2014年   153篇
  2013年   206篇
  2012年   295篇
  2011年   321篇
  2010年   149篇
  2009年   129篇
  2008年   277篇
  2007年   338篇
  2006年   300篇
  2005年   311篇
  2004年   244篇
  2003年   195篇
  2002年   158篇
  2001年   89篇
  2000年   73篇
  1999年   62篇
  1998年   11篇
  1997年   13篇
  1996年   11篇
  1995年   13篇
  1993年   6篇
  1992年   17篇
  1991年   18篇
  1990年   13篇
  1989年   9篇
  1988年   7篇
  1987年   2篇
  1986年   2篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
排序方式: 共有4128条查询结果,搜索用时 0 毫秒
31.
32.
33.
We investigated the effects of the antioxidant alphae-tocopherol on early- and late-phase fracture healing in a rat model. Sixty male Sprague-Dawley rats were randomized into two groups. The right tibia of each rat was fractured manually under anaesthesia, and fracture sites fixed with intramedullary Kirschner wires. The alpha-tocopherol group received 20 mg/kg alpha-tocopherol intraperitoneally; the control group received intraperitoneal saline injections. Ten rats from each group were sacrificed on day 15, day 45 and day 60. In the alpha-tocopherol group, malondialdehyde concentrations, a measure of lipid peroxidation associated with oxygen free radicals, were significantly decreased on day 15 and day 45 compared with the control group, but had regained the 15-day value on day 60. On histopathological and radiological assessment, fracture healing on day 60 was significantly more advanced in the alpha-tocopherol group. We conclude that alpha-tocopherol has a positive effect on both early and late-phase fracture healing, and may be beneficial in clinical fracture  相似文献   
34.
CmeABC functions as a multidrug efflux pump contributing to the resistance of Campylobacter to a broad range of antimicrobials. In this study, we examined the role of CmeABC in bile resistance and its contribution to the adaptation of Campylobacter jejuni in the intestinal tract of the chicken, a natural host and a major reservoir for Campylobacter. Inactivation of cmeABC drastically decreased the resistance of Campylobacter to various bile salts. Addition of choleate (2 mM) in culture medium impaired the in vitro growth of the cmeABC mutants but had no effect on the growth of the wild-type strain. Bile concentration varied in the duodenum, jejunum, and cecum of chicken intestine, and the inhibitory effect of the intestinal extracts on the in vitro growth of Campylobacter was well correlated with the total bile concentration in the individual sections of chicken intestine. When inoculated into chickens, the wild-type strain colonized the birds as early as day 2 postinoculation with a density as high as 10(7) CFU/g of feces. In contrast, the cmeABC mutants failed to colonize any of the inoculated chickens throughout the study. The minimum infective dose for the cmeABC mutant was at least 2.6 x 10(4)-fold higher than that of the wild-type strain. Complementation of the cmeABC mutants with a wild-type cmeABC allele in trans fully restored the in vitro growth in bile-containing media and the in vivo colonization to the levels of the wild-type strain. Immunoblotting analysis indicated that CmeABC is expressed and immunogenic in chickens experimentally infected with C. jejuni. Together, these findings provide compelling evidence that CmeABC, by mediating resistance to bile salts in the intestinal tract, is required for successful colonization of C. jejuni in chickens. Inhibition of CmeABC function may not only control antibiotic resistance but also prevent the in vivo colonization of pathogenic Campylobacter.  相似文献   
35.
Purpose: We aimed to evaluate the effectiveness of the endourologic management of forgotten and/or encrusted ureteral stents together with our single-center experience.

Materials and methods: Fifty-four patients with forgotten double-J ureteral stents were treated in our center between January 2008 and March 2014. Encrustation and the related stone burdens were estimated by using computerized tomography and kidney–ureter–bladder radiography. The management method was chosen based on the stone burden or clinical and radiological findings.

Results: Fifty-four patients, 39 males and 15 females, were included in the study. The average age of the patients was 38.2?±?25.06 (2–86) years. The average indwelling time of the ureteral stents was 22.6?±?30.3 (6–144) months. Six of the patients with forgotten stents had solitary kidneys. The double-J stent (DJS) was fragmented in four (7.4%) patients. A urinary system infection was present in 15 (27.7%) of the patients. The ureteral stents and related stones were successfully removed without any complications by combined endourologic techniques to achieve a stone-free state in all patients except for patient with 110 months of forgotten stent time in whom nephrectomy was performed for a nonfunctioning kidney related to the forgotten stent.

Conclusions: Forgotten/encrusted DJS may lead to complications in a range of urinary system infections, up to a loss of renal function. They can be safely and successfully removed, and the renal function can be preserved by endourologic techniques, starting with the least invasive procedures in centers highly experienced.  相似文献   
36.
Methods:We retrospectively analyzed the patients who underwent RALRP for localized prostate cancer by a single surgeon in our clinic from January 1, 2009–February 1, 2016. Continence was defined as no leakage or use of a safety pad for minimal leakage. The main outcome measure was continence at postoperative week 1 and months 1, 6, and 12.Results:Between 2009 and 2016, 239 patients underwent RALRP for localized prostate disease. Seventy-four patients underwent a standard approach (group 1), 88 had posterior reconstruction (group 2), and 77 had posterior reconstruction with total anatomic restoration (group 3). After 1 week, 24.3% of the patients in group 1 (18/74), 31.8% in group 2 (28/88), and 45.8% in group 3 (33/72) were continent (P = .02). One month after the surgery, continence rates for groups 1, 2, and 3 were 56.7, 67, and 75%, respectively (0.065). After 6 and 12 months, continence rates for groups 1, 2, and 3 were 72.9 and 87.8%, 81.8 and 89.7%, and 84.7 and 91.6%, respectively (P = .178 and .7484).Conclusion:Anatomic restoration improves continence rates in the early period after RALRP. Even though other parameters were higher in the total restoration group, immediate continence (at 1 week) was significantly better.  相似文献   
37.
OBJECTIVE: It has been speculated that trace elements may play a role in the pathogenesis of heart failure. In the present study, we aimed to assess serum concentrations of selenium (Se), zinc (Zn) and copper (Cu) in patients with heart failure (HF) and to compare idiopathic dilated cardiomyopathy (IDCM) and ischemic cardiomyopathy (ICM) patients with healthy controls. METHODS: This study population included 54 HF patients (26 IDCM patients and 28 ICM patients) and 30 healthy subjects. Serum levels of selenium, zinc, and copper were assessed by atomic absorption spectrophotometry method. RESULTS: Serum concentrations of Se and Zn in HF patients were significantly lower than in healthy controls (p=0.000 and p<0.01, respectively). However, serum Cu concentrations in these patients were significantly higher than in controls (p=0.000). There were no significant difference in the trace elements status between IDCM and ICM patients (p>0.05 for all parameters). Relationships of the serum trace element concentrations studied with echocardiographic and hemodynamic parameters were not statistically significant. CONCLUSION: Our study showed that heart failure is associated with lower Se and Zn concentrations, and higher Cu concentration, and serum Se, Zn and Cu element profiles were similar in IDCM and ICM.  相似文献   
38.
39.
BACKGROUND: Previous studies have shown improvement in left ventricular function and development of the reverse remodeling in the left ventricle and left atrium after cardiac resynchronization therapy (CRT). The aim of this study was to investigate the effect of CRT on left atrial appendage (LAA) function and pulmonary venous flow pattern. METHODS: Eighteen patients with systolic heart failure and complete left bundle branch block underwent implantation of biventricular pacemaker devices. In order to follow changes in LAA, transthoracic and transesophageal echocardiographic examinations were performed 1 week before and repeated 1 and 6 months after pacemaker implantation. RESULTS: CRT resulted in significant clinical improvement and decrease in NYHA functional class in 17 patients (94%). Maximum and minimum areas of left atrial appendage (LAAAmax and LAAAmin) decreased, with a concomitant increase in LAA ejection fraction. [LAAAmax: from 4.6+/-2 to 4.2+/-1.8 cm2 at the first (P < 0.001) and to 4.0+/-1.8 cm2 at the sixth month (P < 0.001); LAAAmin: from 2.7+/-1.3 to 2.3+/-1.2 cm2 at the first (P < 0.001) and to 2.2+/-1.2 cm2 at the sixth month (P < 0.001) and LAA ejection fraction: from 41+/-12% to 46+/-10% at the first (P = 0.007) and to 47+/-8% at the sixth month (P = 0.003)]. LAA active emptying and filling flow and pulmonary venous systolic velocities also increased after CRT. The appendage active emptying velocity correlated significantly with left ventricular ejection fraction (r = 0.50, P = 0.002), LAA ejection fraction (r = 0.51, P = 0.002), left atrial maximal volume, LAVmax (r = -0.44, P = 0.007), left atrial minimal volume, LAVmin (r = -0.50, P = 0.002) and pulmonary vein systolic flow velocity (r = 0.33, P = 0.05). CONCLUSION: Treatment of heart failure by CRT results with marked improvements in LAA function and increases pulmonary venous systolic velocity.  相似文献   
40.
Platelets contribute to blood coagulation at sites of vascular injury and to the recruitment of leukocytes at sites of inflammation. Under pathological conditions, platelets are involved in numerous diseases and clinical complications, such as deep venous thrombosis, embolism and atherosclerosis. But so far, little is known about the mechanisms of inflammation in large veins and the role of platelets in inflamed large veins. For this purpose, we investigated primary and secondary interactions between platelets, leukocytes and endothelial cells in the femoral vein in vivo with special regard to the role of CD62P (P-selectin) and CD162 (PSGL-1). Mice were challenged with lipopolysaccharide (LPS)/D-galactosamine (D-gal) and either CD162 or CD62P was blocked by intravenous administration of a corresponding antibody at the time point of LPS/D-gal injection. Four hours after LPS/gal injection, intravital fluorescence microscopy of the femoral vein was performed and primary and secondary platelet-leukocyte-endothelial cell-interactions were visualized after in vivo platelet and leukocyte staining with rhodamine 6G. Analysis of intravital fluorescence microscopy revealed that LPS/D-gal caused a strong inflammatory reaction of the venous endothelium with significant induction of platelet and leukocyte tethering, rolling and adhesion. Secondary interactions of platelets to adherent or rolling platelets or leukocytes were also increased after LPS/D-gal-injection. Immunoneutralization of either CD162 or CD62P significantly decreased platelet primary and secondary capture as well as leukocyte rolling and adhesion. CD162 and CD62P play a central role in mediating inflammatory primary and secondary interactions of platelets and leukocytes to the endothelium in inflamed large veins in vivo. Thus, blocking CD162 or CD62P might be an attractive tool for preventing platelet and leukocyte-driven venous diseases.  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