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   8028篇
  免费   568篇
  国内免费   32篇
耳鼻咽喉   136篇
儿科学   304篇
妇产科学   189篇
基础医学   1109篇
口腔科学   124篇
临床医学   722篇
内科学   1465篇
皮肤病学   97篇
神经病学   902篇
特种医学   222篇
外科学   1133篇
综合类   106篇
一般理论   15篇
预防医学   578篇
眼科学   206篇
药学   569篇
中国医学   11篇
肿瘤学   740篇
  2023年   88篇
  2022年   183篇
  2021年   267篇
  2020年   189篇
  2019年   213篇
  2018年   263篇
  2017年   221篇
  2016年   241篇
  2015年   254篇
  2014年   330篇
  2013年   422篇
  2012年   628篇
  2011年   539篇
  2010年   352篇
  2009年   264篇
  2008年   400篇
  2007年   439篇
  2006年   381篇
  2005年   351篇
  2004年   340篇
  2003年   322篇
  2002年   324篇
  2001年   131篇
  2000年   110篇
  1999年   133篇
  1998年   63篇
  1997年   58篇
  1996年   44篇
  1995年   38篇
  1994年   29篇
  1993年   29篇
  1992年   71篇
  1991年   63篇
  1990年   55篇
  1989年   68篇
  1988年   51篇
  1987年   52篇
  1986年   50篇
  1985年   58篇
  1984年   42篇
  1983年   35篇
  1982年   34篇
  1981年   28篇
  1979年   48篇
  1978年   26篇
  1977年   25篇
  1976年   25篇
  1975年   22篇
  1973年   26篇
  1972年   26篇
排序方式: 共有8628条查询结果,搜索用时 15 毫秒
71.
Background Transnasal endoscopic resection (TER) has become the treatment of choice for many skull base tumors. A major limitation of TER is the management of large dural defects and the need for repair of cerebrospinal fluid (CSF) leaks, particularly among patients who are treated with chemotherapy (CTX) or radiotherapy (RT). The objective of this study is to determine the impact of CTX and RT on the success of CSF leak repair after TER. Methods We performed a retrospective chart review of a single-institution experience of TER from 1992 to 2011. Results We identified 28 patients who had endoscopic CSF leak repair after resection of malignant skull base tumors. Preoperative RT was utilized in 18 patients, and 9 had undergone CTX. All patients required CSF leak repair with rotational flaps after cribriform and/or dural resection. CSF leak repair failed in three patients (11%). A history of RT or CTX was not associated with failed CSF leak repair. Conclusion Adjuvant or neoadjuvant CTX or RT is not associated with failed CSF leak repair. Successful CSF leak repair can be performed in patients with malignant skull base tumors with an acceptable risk profile.  相似文献   
72.

Background

Epithelial ovarian cancer (EOC) remains the main cause of mortality due to gynecological malignancies. Optimal tumor debulking and platinum response are the most important prognostic factors for overall survival (OS) in primary EOC. In the setting of recurrence, the role of cytoreduction is not clear. A critical point is to predict preoperatively the subgroup of patients with optimal surgical outcome. The aim of the study was to analyze the predictive role of HE4 for surgical outcome and platinum response in EOC patients experiencing a first relapse. Secondary aims were the prognostic role of HE4 for OS and progression-free survival (PFS).

Methods

Plasma was obtained before secondary cytoreduction from 73 EOC patients. A total of 66.7 % underwent a total macroscopic tumor clearance; 86.3 % of the patients had disease that responded to platinum therapy. HE4 was detected by enzyme-linked immunosorbent assay. For statistical analysis, the chi-square test, Fisher’s exact test, Kendall’s tau b, and Mann-Whitney U test were used. OS, PFS rates, and respective 95 % confidence intervals (CI) were estimated according to the Kaplan–Meier method.

Results

At a HE4 cutoff value of 250 pMk, a sensitivity of 52 % and a specificity of 93.8 % (p = 0.001, 95 % CI 0.601–0.861) were reached in predicting total macroscopic tumor clearance. Plasma HE4 concentrations together with platinum response were the only independent prognostic factors for OS (p < 0.001, hazard ratio [HR] 18.77, 95 % CI 4.68–75.25; and p = 0.044, HR 3.33, 95 % CI 1.03–10.7, respectively). Together with ascites, HE4 was the only independent predictive factor for surgical outcome (p = 0.029, odds ratio [OR] 7.2, 95 % CI 1.22–42.19 and p = 0.036, OR 10.18, 95 % CI 1.16–88.69, respectively).

Conclusions

HE4 is an independent predictive marker for surgical outcome and OS in patients with recurrent EOC. Larger population studies are needed to validate these results.  相似文献   
73.
74.
The incidence of amikacin resistance among gram-negative bacilli isolated at the New York V.A. Medical Center increased from 2.0% to greater than 7% during an 18-month period from January 1980 to July 1981. This increase coincided with a threefold increase in amikacin use at this institution. The amikacin-resistant (AKR) isolates most frequently recovered in 1981 were species of Klebsiella, Serratia, and Pseudomonas. These organisms were recovered from multiple sites, including urine, sputum, wounds, blood, peritoneal fluid, and pleural fluid. The amikacin-modifying enzyme 6'-N-acetyltransferase was detected in 27 (67.5%) of 40 randomly selected AKR isolates. These data indicate that resistance to amikacin in this hospital is enzymatically mediated in most strains of AKR Klebsiella and Serratia and in about one-third of AKR strains of P. aeruginosa. This finding supports the conclusion that amikacin resistance is enhanced by the pressure of increased amikacin use.  相似文献   
75.
A subpopulation of olivary pretectal nucleus (OPN) neurons discharges action potentials in an oscillatory manner, with a period of approximately two minutes. This ‘infra‐slow’ oscillatory activity depends on synaptic excitation originating in the retina. Signals from rod‐cone photoreceptors reach the OPN via the axons of either classic retinal ganglion cells or intrinsically photosensitive retinal ganglion cells (ipRGCs), which use melanopsin for photon capturing. Although both cell types convey light information, their physiological functions differ considerably. The aim of the present study was to disentangle how rod‐cone and melanopsin photoresponses contribute to generation of oscillatory activity. Pharmacological manipulations of specific phototransduction cascades were used whilst recording extracellular single‐unit activity in the OPN of anaesthetized rats. The results show that under photopic conditions (bright light), ipRGCs play a major role in driving infra‐slow oscillations, as blocking melanopsin phototransmission abolishes or transiently disturbs oscillatory firing of the OPN neurons. On the other hand, blocking rod‐cone phototransmission does not change firing patterns in photopic conditions. However, under mesopic conditions (moderate light), when melanopsin phototransmission is absent, blocking rod‐cone signalling causes disturbances or even the disappearance of oscillations implying that classic photoreceptors are of greater importance under moderate light. Evidence is provided that all photoreceptors are required for the generation of oscillations in the OPN, although their roles in driving the rhythm are determined by the lighting conditions, consistent with their relative sensitivities. The results further suggest that maintained retinal activity is crucial to observe infra‐slow oscillatory activity in the OPN.  相似文献   
76.

Background and purpose

Extracellular matrix remodeling is altered in rotator cuff tears, partly due to altered expression of matrix metalloproteinases (MMPs) and their inhibitors. It is unclear whether this altered expression can be traced as changes in plasma protein levels. We measured the plasma levels of MMPs and their tissue inhibitors (TIMPs) in patients with rotator cuff tears and related changes in the pattern of MMP and TIMP levels to the extent of the rotator cuff tear.

Methods

Blood samples were collected from 17 patients, median age 61 (39–77) years, with sonographically verified rotator cuff tears (partial- or full-thickness). These were compared with 16 age- and sex-matched control individuals with sonographically intact rotator cuffs. Plasma levels of MMPs and TIMPs were measured simultaneously using Luminex technology and ELISA.

Results

The plasma levels of TIMP-1 were elevated in patients with rotator cuff tears, especially in those with full-thickness tears. The levels of TIMP-1, TIMP-3, and MMP-9 were higher in patients with full-thickness tears than in those with partial-thickness tears, but only the TIMP-1 levels were significantly different from those in the controls.

Interpretation

The observed elevation of TIMP-1 in plasma might reflect local pathological processes in or around the rotator cuff, or a genetic predisposition in these patients. That the levels of TIMP-1 and of certain MMPs were found to differ significantly between partial and full-thickness tears may reflect the extent of the lesion or different etiology and pathomechanisms.The subacromial pain syndrome includes a range of disorders from reversible inflammation to massive rotator cuff tearing (Shindle et al. 2011). The etiology appears to be multifactorial, and several anatomic structures may be involved. Repetitive damage of the supraspinatus tendon by mechanical wear from the coraco-acromial ligament and the anterior acromion was described by Neer 1972, and for a long time it was considered the major cause of cuff tearing (Neer 1983). Others have reported age-related tendon degeneration, associated with alterations in extracellular matrix remodeling as a contributing factor (Lo et al. 2004, Millar et al. 2009, Pasternak and Aspenberg 2009, Shindle et al. 2011). Histopathological changes associated with rotator cuff tendinosis have been documented, but it is unclear whether they are a result of a subacromial impingement or an endogenous process, and whether tendinosis might predispose to tendon tears (Lo et al. 2004).Regardless of whether mechanical or degenerative factors initiates tearing, there are alterations in the cellular and extracellular matrix (Gwilym et al. 2009). It has been suggested that genetic factors may influence apoptosis or regeneration (Gwilym et al. 2009, Shindle et al. 2011). Still, the molecular changes associated with rotator cuff tearing are largely unknown (Lo et al. 2004, Garofalo et al. 2011). Turnover of the extracellular matrix (ECM) is mediated by matrix metalloproteinases (MMPs), a family of at least 24 zinc-dependent endopeptidases. The MMPs are classified according to their main degradative activity, into for example collagenases, gelatinases, and stromelysins (Pasternak and Aspenberg 2009). Their activity is regulated by endogenous inhibitors: tissue inhibitors of metalloproteinases (TIMPs). There are 4 known TIMPs, which reversibly inhibit all MMPs by 1:1 interaction with the zinc-binding site (Lo et al. 2004, Pasternak and Aspenberg 2009). MMP production is induced by factors such as cytokines and tumor necrosis factor-α. MMPs are secreted by connective tissue and inflammatory cells and then activated in the extracellular space (Garofalo et al. 2011). The composition of the ECM is dependent on the balance between MMPs and TIMPs (Lo et al. 2004, Pasternak and Aspenberg 2009, Garofalo et al. 2011). Levels of MMP mRNA and TIMP mRNA were found to be altered in biopsies from torn rotator cuff tendon (Lo et al. 2004). It is not known, however, whether these changes are causative or whether they are secondary to tendon tearing.Studies on MMP and TIMP levels in patients with rotator cuff syndrome and cuff tears have used samples collected at surgery from the subacromial bursa, synovial fluid, or the tendons (Lo et al. 2004, Lakemeier et al. 2010, Shindle et al. 2011). To date, there have been no data on systemic levels. Alterations in MMP and TIMP levels in systemic blood samples have been identified in other musculoskeletal diseases such as Dupuytren’s disease, ankylosing spondylitis, and fracture non-union, suggesting that alterations associated with rotator cuff disease may also be measurable systemically (Ulrich et al. 2003, Henle et al. 2005, Pasternak and Aspenberg 2009). In osteoarthritis, circulating MMP-3 has been suggested to be a marker of disease severity and has been used as a prognostic tool (Lohmander et al. 2005).We measured plasma levels of MMPs and TIMPs in patients with rotator cuff tears and compared partial- and full-thickness tears, in order to find disease-associated changes in the expression patterns of MMP and TIMP.  相似文献   
77.
Suture technique for valve replacement surgery has often focused on decreasing the soft tissue injury that leads to pseudoaneurysm formation and associated latent infection. There is universal recognition that precise suture placement is essential for avoiding adverse sequelae while allowing flexibility during the implantation of the prosthesis. The use of a continuous chain of linked horizontal mattress sutures (NextStitch) has allowed maximal precision in the approximation of sutures within the valve annulus. The product was used in a series of consecutive mitral and aortic valve replacements, and typical echocardiographic images from each type of implantation are presented. Postoperative echocardiography images revealed that no perivalvular leaks occurred and that NextStitch did not obscure detailed interrogation or assessment of the valve prosthesis.  相似文献   
78.
The purpose of this study was to describe the toxicity of concurrent standard dose adjuvant radiation therapy (RT) and paclitaxel in a series of patients receiving primary breast cancer therapy. From June 1998 to April 1999, 20 patients with breast cancer received concurrent adjuvant radiation and paclitaxel. There were 16 patients (80%) with American Joint Committee on Cancer (AJCC) stage II disease and 4 with stage III disease. Eighteen patients, 12 postmastectomy and 6 breast conservation, were treated with definitive surgery followed by concurrent RT and paclitaxel. Two received concurrent neoadjuvant radiation and paclitaxel. All patients received a doxorubicin-containing combination prior to radiation and paclitaxel. RT was delivered concurrently with paclitaxel after the completion of all doxorubicin therapy, with all patients receiving at least two cycles of paclitaxel (175 mg/m 2) every 3 weeks during RT. Toxicity was graded weekly according to Radiation Therapy Oncology Group criteria. Thirteen patients (65%) developed grade 2 or higher cutaneous toxicity. In the postmastectomy group, 6 of 12 patients (50%) developed grade 2 cutaneous toxicity, and 4 of 12 patients (33%) developed grade 3. RT was discontinued in 1 and placed on hold in 3 of these patients. In the breast-conservation group, 2 of 6 patients (33%) developed grade 3 toxicity. In the neoadjuvant group, 1 of 2 patients (50%) developed grade 3 toxicity. Four patients (20%) developed radiation pneumonitis, 2 of 12 (17%) in the postmastectomy group and 2 of 6 (33%) in the breast conservation group, with 2 requiring hospitalization and 1 a diagnostic open-lung biopsy. In this group of patients, standard dose concurrent radiation and paclitaxel resulted in a high incidence of cutaneous and pulmonary toxicity. Concurrent radiation and paclitaxel with these doses and schedule should be approached cautiously until further studies documenting its safety are completed.  相似文献   
79.
Objectives. New onset postoperative atrial fibrillation (POAF) after cardiac surgery is associated with increased risk for thromboembolic complications. Compliance with anticoagulation treatment is prerequisite for successful outcome after POAF. We hypothesized that a disciplined anticoagulation protocol initiated instantly after POAF secures a long-term outcome. Design. A total of 519 consecutive patients undergoing cardiac surgery were retrospectively analyzed. Patients received anticoagulation using warfarin whenever POAF lasted longer than five min. Postoperative outcome including mortality, myocardial infarction and stroke were compared with patients on sinus rhythm (non-POAF). Results. Mean age of the study cohort was 64.3?±?9.0 years and median follow-up time was 76 months. There were 177 (34%) POAF and 342 (66%) non-POAF patients. At discharge, 144 (81%) POAF patients complied with warfarin, while 82 (24%) non-POAF patients received warfarin for non-rhythm causes (p?p?=?.03). After adjustment for comorbidities, major adverse clinical events (MACE)- including a combination of late cardiovascular mortality, myocardial infarction, stroke and late atrial fibrillation- was independently associated with POAF (OR 2.73, 95%CI 1.69-4.45, p?Conclusions. POAF after cardiac surgery was associated with high risk of MACE. Early anticoagulation may be justified in POAF patients to secure a long-term outcome after cardiac surgery.  相似文献   
80.
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