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   5474篇
  免费   287篇
  国内免费   39篇
耳鼻咽喉   108篇
儿科学   173篇
妇产科学   116篇
基础医学   868篇
口腔科学   559篇
临床医学   383篇
内科学   1100篇
皮肤病学   138篇
神经病学   441篇
特种医学   100篇
外科学   433篇
综合类   25篇
一般理论   3篇
预防医学   543篇
眼科学   70篇
药学   406篇
中国医学   25篇
肿瘤学   309篇
  2024年   5篇
  2023年   48篇
  2022年   139篇
  2021年   233篇
  2020年   164篇
  2019年   189篇
  2018年   205篇
  2017年   130篇
  2016年   184篇
  2015年   226篇
  2014年   261篇
  2013年   333篇
  2012年   448篇
  2011年   527篇
  2010年   288篇
  2009年   244篇
  2008年   336篇
  2007年   361篇
  2006年   335篇
  2005年   300篇
  2004年   261篇
  2003年   192篇
  2002年   165篇
  2001年   22篇
  2000年   14篇
  1999年   19篇
  1998年   17篇
  1997年   22篇
  1996年   17篇
  1995年   13篇
  1994年   5篇
  1993年   13篇
  1992年   7篇
  1991年   5篇
  1990年   3篇
  1988年   9篇
  1987年   4篇
  1986年   4篇
  1985年   6篇
  1983年   9篇
  1981年   3篇
  1980年   2篇
  1979年   2篇
  1977年   4篇
  1975年   4篇
  1974年   2篇
  1973年   2篇
  1972年   3篇
  1971年   2篇
  1955年   2篇
排序方式: 共有5800条查询结果,搜索用时 15 毫秒
31.
This study aimed to analyze the effects of light-emitting diode (LED) therapy on sternotomy pain and healing in patients who underwent coronary artery bypass grafting (CABG). The patients were followed for 6 months after the surgery to determine their dehiscence. This study was conducted with 90 volunteers who electively submitted to CABG. The volunteers were randomly allocated into three different groups of equal size: LED (λ of 640?±?20 nm and spatial average energy fluency of 1.2 J/cm2 during hospitalization), placebo, or control. The outcomes assessed were pain when coughing by a visual analog scale (VAS) and the McGill questionnaire and sternotomy healing by clinical assessment and photographical register end interpretation. The LED group had better pain reduction, as indicated by both the VAS and the McGill questionnaire (number of words chosen and pain index) (p?≤?0.05), on days 6 and 8 after hospital discharge compared to the placebo and control groups. One month after surgery, almost no individual mentioned pain when coughing. Three researchers blindly analyzed the incision photographs to determine hyperemia and wound closure, and they found that the LED group had both less hyperemia and less incision bleeding or dehiscence. The LED therapy (640 nm) had an analgesic effect on the sternotomies of patients who underwent CABG, increasing their incision healing and preventing dehiscence.  相似文献   
32.
Scientific advances have been made to optimize the healing process in spinal cord injury. Studies have been developed to obtain effective treatments in controlling the secondary injury that occurs after spinal cord injury, which substantially changes the prognosis. Low-intensity laser therapy (LILT) has been applied in neuroscience due to its anti-inflammatory effects on biological tissue in the repairing process. Few studies have been made associating LILT to the spinal cord injury. The objective of this study was to investigate the effect of the LILT (GaAlAs laser—780 nm) on the locomotor functional recovery, histomorphometric, and histopathological changes of the spinal cord after moderate traumatic injury in rats (spinal cord injury at T9 and T10). Thirty-one adult Wistar rats were used, which were divided into seven groups: control without surgery (n?=?3), control surgery (n?=?3), laser 6 h after surgery (n?=?5), laser 48 h after surgery (n?=?5), medullar lesion (n?=?5) without phototherapy, medullar lesion?+?laser 6 h after surgery (n?=?5), and medullar lesion?+?laser 48 h after surgery (n?=?5). The assessment of the motor function was performed using Basso, Beattie, and Bresnahan (BBB) scale and adapted Sciatic Functional Index (aSFI). The assessment of urinary dysfunction was clinically performed. After 21 days postoperative, the animals were euthanized for histological and histomorphometric analysis of the spinal cord. The results showed faster motor evolution in rats with spinal contusion treated with LILT, maintenance of the effectiveness of the urinary system, and preservation of nerve tissue in the lesion area, with a notorious inflammation control and increased number of nerve cells and connections. In conclusion, positive effects on spinal cord recovery after moderate traumatic spinal cord injury were shown after LILT.  相似文献   
33.

Purpose

To assess factors influencing the long-term survival of elderly dialysis patients.

Methods

The study group consisted of 51 prevalent dialysis patients aged over 70?years (32 F and 19?M, all caucasians), who had been on a chronic hemodialysis (27) or peritoneal dialysis program (24) for at least 2?months; median age was 77?years, median time on dialysis before inclusion was 16?months, and median residual diuresis was 600?ml. The patients were prospectively followed up to 4?years, and an analysis of factors affecting survival was performed.

Results

Thirteen patients from the initial cohort of 51 (25.5?%) survived the whole 48-month observation period: 10 HD patients (37?%) and 3 PD patients (12.5?%). Annual mortality rate was 28.2?%: 37.4?% on PD vs. 20.9?% on HD. The dialysis modality had a significant impact on patients?? survival (p?=?0.049; Cox F-test). The independent mortality risk factors in the Cox proportional hazard regression model were higher plasma pro-atrial natriuretic peptide (pro-ANP) (p?=?0.006), lower residual diuresis (p?=?0.048), and lower systolic blood pressure (BP) value (p?=?0.039).

Conclusions

Paramount for the survival of the elderly on dialysis is adequate extracellular volume control. Residual renal function is a protective factor for the survival of elderly HD patients. This observation is novel, not previously reported in an elderly dialysis population.  相似文献   
34.

Background

Vertebroplasty carries multiple complications due to the leakage of polymethylmethacrylate (PMMA) into the venous system through the iliolumbar or epidural veins. The rate of venous cement complications may vary from 1 to 10 %, with cement extravasation into the venous system in 24 % of patients. Emboli may further migrate into the right heart chambers and pulmonary arteries. Patients may vary in presentation from asymptomatic or symptoms such as syncope to life-threatening complications.

Case report

We present a case of a 57-year-old lady diagnosed with osteoporosis who underwent a staged antero–posterior fixation with PMMA vertebroplasty of progressive thoraco–lumbar kyphosis caused by osteoporotic fractures to T12, L1 and L2 vertebral bodies. Four weeks after the operation, the patient developed symptoms of left-sided chest pain, tachycardia and tachypnea. CT pulmonary angiogram (CTPA) found a high-density material within the right atrium, whilst ECHO demonstrated normal systolic function. The patient was commenced on enoxaparin at therapeutic dose of 1.5 mg/kg for 3 months and remained asymptomatic. Follow-up ECHO found no change to the heart function and no blood clot on the PMMA embolus.

Conclusions

Factors influencing the decision about conservative treatment included symptoms, localisation of the embolus, as well as time lapse between vertebroplasty and clinical manifestation. Patients that are commonly asymptomatic can be treated conservatively. The management of choice is anticoagulation with low-molecular-weight heparin or warfarin until the foreign body epithelialises and ceases in becoming potentially thrombogenic. Symptomatic patients with thrombi in the right atrium are commonly managed via percutaneous retrieval, whilst those with RV involvement or perforation are commonly managed with surgical retrieval. Management of individual patients should be based on individual clinical circumstances. Patients presenting with intracardiac bone cement embolism related to spinal procedures require thorough clinical assessment, cardiology input, and if required, surgical intervention.
  相似文献   
35.

Objective

The purpose of this study was to investigate the roles of the kallikrein-kinin system and matrix metalloproteinases (MMPs) in the development of arterial restenosis attributable to intimal hyperplasia in the femoropopliteal arteries.

Methods

This report describes a single-center prospective study of 27 patients with peripheral artery disease who required percutaneous transluminal angioplasty and stenting of the femoropopliteal segment using covered stent grafts. The blood concentrations of total and kininogen fractions were evaluated using immunoenzymatic methods. Plasma kallikrein was evaluated by the colorimetric method. Tissue kallikrein was evaluated by the spectrophotometric method. The activity of kininase II was measured by fluorometric analysis. Quantification of MMPs was performed by zymography, and tissue inhibitors of metalloproteinases were measured by enzyme-linked immunosorbent assay.

Results

Four (15%) of the treated patients developed restenosis at the 6-month follow-up evaluation. These patients had significantly lower levels of high-molecular-weight kininogens (24 hours; P < .05) and low-molecular-weight kininogens (before, P < .05; 24 hours, P < .01; 6 months, P < .05) and lower levels of tissue inhibitor of metalloproteinases-2 (6 months; P < .05) than the patients without restenosis. The activity levels of plasma and tissue kallikrein, kininase II, and MMPs did not differ significantly between the patients with and without restenosis.

Conclusions

This study demonstrates an involvement of the kallikrein-kinin system in in-stent restenosis, although we could not confirm the participation of metalloproteinases in the restenosis process.  相似文献   
36.
37.
Chronic renal, liver, and heart failure in children associates with multiple skeletal complications. Increased fracture incidence often persists after transplantation and could be related to alterations in bone material properties. In the present cohort study we evaluated bone mineralization density distribution (BMDD) by quantitative backscattered electron imaging (qBEI) in 23 pediatric solid organ allograft recipients with suspected osteoporosis. We measured BMDD in the entire cross‐sectional area of transiliac bone biopsies obtained from kidney (n = 9), liver (n = 9), and heart (n = 5) transplant recipients (aged 7.6 to 19.7 years; 6.0 ± 5.6 years posttransplantation, patients with a history of clinical fractures: n = 14). The BMDD findings were compared with age‐appropriate references and with a previously presented cohort of children with chronic kidney disease on dialysis (CKD5D, n = 18). Furthermore, we related the BMDD parameters with patients’ clinical and bone histomorphometric outcomes. Compared to healthy children, qBEI results for cancellous and cortical bone in transplant recipients revealed an increase in the most frequently occurring calcium concentration (+2.9%, p = 0.001; +3.5%, p = 0.014), in the portion of fully mineralized bone (fivefold; 10‐fold, both p < 0.0001) and in heterogeneity of mineralization (+26,5% and +27.8%, both p < 0.0001), respectively. Moreover, the BMDD parameters were nonsignificantly distinct from CKD5D cohort except that the heterogeneity in mineralization was higher posttransplantation. There was a strong inverse correlation between the average calcium content of the bone matrix and patients’ biochemical ALP levels, histomorphometric indices of bone formation and resorption. The abnormally high bone matrix mineralization in transplant recipients, consistent with serum and histomorphometric outcomes, suggests a history of low bone turnover with accumulation of fully mineralized bone packets. Additionally, the increased heterogeneity of mineralization suggests local alterations in mineralization kinetics, which may be linked to dysfunctional osteocytes that were recently shown to accumulate within the bone matrix during organ failure and concomitant glucocorticoid and immunosuppressive medication. © 2017 American Society for Bone and Mineral Research.  相似文献   
38.
The dose-response relationship between elevated plasma free fatty acid (FFA) levels and impaired insulin-mediated glucose disposal and insulin signaling was examined in 21 lean, healthy, normal glucose-tolerant subjects. Following a 4-h saline or Liposyn infusion at 30 (n = 9), 60 (n = 6), and 90 (n = 6) ml/h, subjects received a 2-h euglycemic insulin (40 mU . m(-2) . min(-1)) clamp. Basal plasma FFA concentration ( approximately 440 micromol/l) was increased to 695, 1,251, and 1,688 micromol/l after 4 h of Liposyn infusion and resulted in a dose-dependent reduction in insulin-stimulated glucose disposal (R(d)) by 22, 30, and 34%, respectively (all P < 0.05 vs. saline control). At the lowest lipid infusion rate (30 ml/h), insulin receptor and insulin receptor substrate (IRS)-1 tyrosine phosphorylation, phosphatidylinositol (PI) 3-kinase activity associated with IRS-1, and Akt serine phosphorylation were all significantly impaired (P < 0.05-0.01). The highest lipid infusion rate (90 ml/h) caused a further significant reduction in all insulin signaling events compared with the low-dose lipid infusion (P < 0.05-0.01) whereas the 60-ml/h lipid infusion caused an intermediate reduction in insulin signaling. However, about two-thirds of the maximal inhibition of insulin-stimulated glucose disposal already occurred at the rather modest increase in plasma FFA induced by the low-dose (30-ml/h) lipid infusion. Insulin-stimulated glucose disposal was inversely correlated with both the plasma FFA concentration after 4 h of lipid infusion (r = -0.50, P = 0.001) and the plasma FFA level during the last 30 min of the insulin clamp (r = -0.54, P < 0.001). PI 3-kinase activity associated with IRS-1 correlated with insulin-stimulated glucose disposal (r = 0.45, P < 0.01) and inversely with both the plasma FFA concentration after 4 h of lipid infusion (r = -0.39, P = 0.01) and during the last 30 min of the insulin clamp (r = -0.43, P < 0.01). In summary, in skeletal muscle of lean, healthy subjects, a progressive increase in plasma FFA causes a dose-dependent inhibition of insulin-stimulated glucose disposal and insulin signaling. The inhibitory effect of plasma FFA was already significant following a rather modest increase in plasma FFA and develops at concentrations that are well within the physiological range (i.e., at plasma FFA levels observed in obesity and type 2 diabetes).  相似文献   
39.
Background: The cardiotoxic mechanism of local anesthetics may include interruption of cardiac sympathetic reflexes. The authors undertook this investigation to determine if clinically relevant concentrations of bupivacaine and levobupivacaine interfere with exocytotic norepinephrine release from cardiac sympathetic nerve endings.

Methods: Rat atria were prepared for measurements of twitch contractile force and 3[H]-norepinephrine release. After nerve endings were loaded with 3[H]-norepinephrine, the tissue was electrically stimulated in 5-min episodes during 10 10-min sampling periods. After each period, a sample of bath fluid was analyzed for radioactivity and 3[H]-norepinephrine release was expressed as a fraction of tissue counts. Atria were exposed to buffer alone during sampling periods 1 and 2 (S1 and S2). Control atria received saline (100 [mu]l each, n = 6 atria) in S3-S10. Experimental groups (n = 6 per group) received either bupivacaine or levobupivacaine at concentrations (in [mu]M) of 5 (S3-S4), 10 (S5-S6), 30 (S7-S8), and 100 (S9-S10).

Results: Bupivacaine and levobupivacaine decreased stimulation-evoked fractional 3[H]-norepinephrine release with inhibitory concentration 50% values of 5.1 +/- 0.5 and 6.1 +/- 1.3 [mu]m. The inhibitory effect of both local anesthetics (~70%) approached that of tetrodotoxin. Local anesthetics abolished the twitch contractions of atria with inhibitory concentration 50% values of 12.6 +/- 5.0 [mu]m (bupivacaine) and 15.7 +/- 3.9 [mu]m (levobupivacaine). In separate experiments, tetrodotoxin inhibited twitch contractile force by only 30%.  相似文献   

40.
Osteoporosis affects the craniofacial and oral structures and has been associated with periodontal bone loss, tooth loss and reduced jaw bone mass.ObjectiveThis study aimed to test the therapeutic efficacy of synthetic bone mineral (SBM) in minimizing alveolar bone loss induced by mineral deficiency in a rat model. SBM consists of a calcium carbonate apatite (similar to bone apatite) matrix incorporating magnesium, zinc, and fluoride ions.DesignThirty female Sprague Dawley rats (2 months old) were randomly distributed into 3 groups (10 rats per group): GA (control), on basic diet; GB, on mineral deficient (MD) diet; and GC, on MD + SBM. The rats were sacrificed after 3 months, the jawbones were isolated and the soft tissues removed. Bone density was determined using X-ray radiography (Faxitron); mandibular cortical width, panoramic mandibular index, and alveolar resorption degree (M/M ratio) using BioquantOsteo; and bone micro-architecture micro-computed tomography and scanning electron microscopy.ResultsCompared to control (GA), the rats on MD diet (GB) experienced significant mandibular bone loss while the rats on MD + SBM diet (GC) experienced significantly less bone loss compared to the GB group.ConclusionSBM, administered orally, may have the potential as an osteoporosis therapeutic agent in minimizing or preventing alveolar bone loss induced by mineral deficiency.  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