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   9283篇
  免费   520篇
  国内免费   70篇
耳鼻咽喉   40篇
儿科学   144篇
妇产科学   133篇
基础医学   1142篇
口腔科学   117篇
临床医学   840篇
内科学   2265篇
皮肤病学   159篇
神经病学   753篇
特种医学   428篇
外科学   1729篇
综合类   29篇
一般理论   5篇
预防医学   718篇
眼科学   184篇
药学   596篇
中国医学   15篇
肿瘤学   576篇
  2023年   55篇
  2022年   108篇
  2021年   268篇
  2020年   151篇
  2019年   246篇
  2018年   303篇
  2017年   188篇
  2016年   188篇
  2015年   253篇
  2014年   321篇
  2013年   444篇
  2012年   757篇
  2011年   716篇
  2010年   468篇
  2009年   422篇
  2008年   634篇
  2007年   686篇
  2006年   559篇
  2005年   622篇
  2004年   533篇
  2003年   470篇
  2002年   496篇
  2001年   74篇
  2000年   68篇
  1999年   84篇
  1998年   81篇
  1997年   61篇
  1996年   65篇
  1995年   62篇
  1994年   50篇
  1993年   30篇
  1992年   36篇
  1991年   43篇
  1990年   23篇
  1989年   32篇
  1988年   21篇
  1987年   22篇
  1986年   14篇
  1985年   26篇
  1984年   21篇
  1983年   9篇
  1982年   17篇
  1981年   8篇
  1980年   9篇
  1979年   9篇
  1973年   10篇
  1971年   7篇
  1970年   7篇
  1968年   11篇
  1947年   8篇
排序方式: 共有9873条查询结果,搜索用时 15 毫秒
71.
72.
We report on a 7 year-old-girl with mandibulo-acral dysplasia. When she was 3 years of age it mimicked scleroderma because of skin atrophy and later on a Hutchinson-Gilford progeria syndrome (HGP). Acro-mandibular dysplasia was diagnosed because of facial hypoplasia and mandibular hypoplasia. The bilateral proximal mid-humeral notch seen in this case is unusual. Received: 22 June 2000 Revision requested: 10 July 2000 Revision received: 7 August 2000 Accepted: 10 August 2000  相似文献   
73.

Background

Stromal mesenchyme cells play an important role in epithelial differentiation and likely in cancer as well. Induction of epithelial differentiation is organ-specific, and the genes responsible could be identified through a comparative genomic analysis of the stromal cells from two different organs. These genes might be aberrantly expressed in cancer since cancer could be viewed as due to a defect in stromal signaling. We propose to identify the prostate stromal genes by analysis of differentially expressed genes between prostate and bladder stromal cells, and to examine their expression in prostate cancer.

Methods

Immunohistochemistry using antibodies to cluster designation (CD) cell surface antigens was first used to characterize the stromas of the prostate and bladder. Stromal cells were prepared from either prostate or bladder tissue for cell culture. RNA was isolated from the cultured cells and analyzed by DNA microarrays. Expression of candidate genes in normal prostate and prostate cancer was examined by RT-PCR.

Results

The bladder stroma was phenotypically different from that of the prostate. Most notable was the presence of a layer of CD13+ cells adjacent to the urothelium. This structural feature was also seen in the mouse bladder. The prostate stroma was uniformly CD13-. A number of differentially expressed genes between prostate and bladder stromal cells were identified. One prostate gene, proenkephalin (PENK), was of interest because it encodes a hormone. Secreted proteins such as hormones and bioactive peptides are known to mediate cell-cell signaling. Prostate stromal expression of PENK was verified by an antibody raised against a PENK peptide, by RT-PCR analysis of laser-capture microdissected stromal cells, and by database analysis. Gene expression analysis showed that PENK expression was down-regulated in prostate cancer.

Conclusion

Our findings show that the histologically similar stromas of the prostate and bladder are phenotypically different, and express organ-specific genes. The importance of these genes in epithelial development is suggested by their abnormal expression in cancer. Among the candidates is the hormone PENK and the down-regulation of PENK expression in cancer suggests a possible association with cancer development.  相似文献   
74.

OBJECTIVES

To determine the technical feasibility and reproducibility of pure natural orifice transluminal endoscopic surgery (NOTES) transvaginal nephrectomy using NOTES‐specific instrumentation, with no transabdominal assistance.

MATERIALS AND METHODS

Five female farm pigs (mean weight 45 kg) had a right NOTES nephrectomy, using a single‐channel gastroscope in the first three pigs and a dual‐channel gastroscope in the remaining two. The peritoneal cavity was accessed through the posterior fornix of the vagina. Dissection was started at the lower pole of the kidney, and the ureter was retracted laterally and followed towards the hilum. An XL articulated 60 cm endo‐GIA stapler (US Surgical, Norwalk, CO, USA), inserted transvaginally via a separate vaginal incision, was used for tissue retraction and renal hilar transection. The kidney was freed, entrapped in an impermeable sac, and extracted intact transvaginally.

RESULTS

All five procedures were successful with no addition of a transabdominal laparoscopic port or open conversion. The total operative duration decreased from 200 min in the first pig to 60 min in the last (mean 113 min); the mean blood loss was <50 mL, the mean kidney length was 13.9 cm and the weight was 142 g. There were no intraoperative complications; at autopsy, there was no pelvic or bowel injury.

CONCLUSIONS

Pure NOTES transvaginal nephrectomy is feasible in the porcine model. It has the potential of a less morbid approach, providing truly scar‐less surgery. Further development of instrumentation is necessary.  相似文献   
75.
76.

Objective

To evaluate the accuracy of abdominal radiography (AXR) for the detection of residual cocaine packets by comparison with computed tomography (CT).

Methods

Over a 1-year period unenhanced CT was systematically performed in addition to AXR for pre-discharge evaluation of cocaine body packers. AXR and CT were interpreted independently by two radiologists blinded to clinical outcome. Patient and packet characteristics were compared between the groups with residual portage and complete decontamination.

Results

Among 138 body packers studied, 14 (10 %) had one residual packet identified on pre-discharge CT. On AXR, at least one reader failed to detect the residual packet in 10 (70 %) of these 14 body packers. The sensitivity and specificity of AXR were 28.6 % (95 % CI: 8.4–58.1) and 100.0 % (95 % CI: 97.0–100.0) for reader 1 and 35.7 % (95 % CI: 12.8–64.9) and 97.6 % (95 % CI: 93.1–99.5) for reader 2. There were no significant patient or packet characteristics predictive of residual portage or AXR false negativity. All positive CT results were confirmed by delayed expulsion or surgical findings, while negative results were confirmed by further surveillance.

Conclusion

Given the poor performance of AXR, CT should be systematically performed to ensure safe hospital discharge of cocaine body packers.

Key Points

? Both abdominal radiography and computed tomography can identify gastrointestinal cocaine packets. ? Ten per cent of body packers had residual packets despite two packet-free stools. ? Seventy per cent of these residual packets were missed on AXR. ? No patient or packet characteristics predicted residual packets or AXR false negativity. ? CT is necessary to ensure safe medical discharge of body packers.  相似文献   
77.
PURPOSE: To compare the performance of the conventional diaphragm navigator (DNAV) and the recently developed cardiac fat navigator (FatNAV) in suppressing respiration-induced cardiac motion in free-breathing 3D balanced steady-state free precession coronary MRA (SSFP CMRA). MATERIALS AND METHODS: In 16 healthy volunteers the right coronary artery (RCA) was imaged at 1.5T using a navigator-gated 3D SSFP CMRA sequence. DNAV and FatNAV gating were performed in random order. Image quality difference was scored by three experienced readers blinded to the gating technique. Blood signal-to-noise ratio (SNR), blood-to-myocardium contrast-to-noise ratio (CNR), and navigator efficiency were calculated. RESULTS: Diagnostically interpretable CMRA was obtained successfully in all 16 subjects with FatNAV gating (0% failure rate) and only 14 subjects with DNAV gating (12% failure rate). Compared to DNAV gating, FatNAV gating provided similar SNR and CNR, better image quality (P < 0.01), and 28% improvement in navigator efficiency (P = 0.002). CONCLUSION: FatNAV gating provides more effective motion suppression and better image quality than DNAV gating for free-breathing 3D SSFP CMRA of the RCA in healthy subjects.  相似文献   
78.
Many palliative interventions have been proposed for patients in whom rotator cuff repair is not feasible as a result of advanced fatty infiltration, definitive loss of tendons, and proximal humeral migration. The long head of the biceps tendon has been proposed as a source of pain in patients with rotator cuff tears. This article presents a review of current concepts on the rationale for arthroscopic biceps tenotomy or tenodesis, and evaluates the objective, subjective, and radiographic results of these palliative procedures. On the basis of different studies, it seems that isolated arthroscopic biceps tenotomy or tenodesis is a valuable option for the treatment of rotator cuff tears in selected patients. Although it does not improve shoulder strength, tenotomy or tenodesis reduces pain and improves the functional range of motion with a high degree of patient satisfaction. However, the progressive radiographic changes that occur with long standing rotator cuff tears are not altered.  相似文献   
79.
Purpose  Respiratory motion causes uptake in positron emission tomography (PET) images of chest structures to spread out and misregister with the CT images. This misregistration can alter the attenuation correction and thus the quantisation of PET images. In this paper, we present the first clinical results for a respiratory-gated PET (RG-PET) processing method based on a single breath-hold CT (BH-CT) acquisition, which seeks to improve diagnostic accuracy via better PET-to-CT co-registration. We refer to this method as “CT-based” RG-PET processing. Methods  Thirteen lesions were studied. Patients underwent a standard clinical PET protocol and then the CT-based protocol, which consists of a 10-min List Mode RG-PET acquisition, followed by a shallow end-expiration BH-CT. The respective performances of the CT-based and clinical PET methods were evaluated by comparing the distances between the lesions’ centroids on PET and CT images. SUVMAX and volume variations were also investigated. Results  The CT-based method showed significantly lower (p = 0.027) centroid distances (mean change relative to the clinical method = −49%; range = −100% to 0%). This led to higher SUVMAX (mean change = +33%; range = −4% to 69%). Lesion volumes were significantly lower (p = 0.022) in CT-based PET volumes (mean change = −39%: range = −74% to −1%) compared with clinical ones. Conclusions  A CT-based RG-PET processing method can be implemented in clinical practice with a small increase in radiation exposure. It improves PET-CT co-registration of lung lesions and should lead to more accurate attenuation correction and thus SUV measurement.  相似文献   
80.
OBJECTIVE: To assess the viability of a strategy of primary resection with secondary liver transplantation (LT) for hepatocellular carcinoma (HCC) on cirrhosis. SUMMARY BACKGROUND DATA: LT is the optimal treatment of HCC with cirrhosis. Owing to organ shortage, liver resection is considered as a reasonable first-line treatment of patients with small HCC and good liver function, with secondary LT as a perspective in case of recurrence. The viability of such strategy, positively explored in theoretical models, is not documented in clinical practice. METHODS: Among 358 consecutive patients with HCC on cirrhosis treated by liver resection (n = 163; 98 of whom were transplantable) or transplantation (n = 195), the feasibility and outcome of secondary transplantation was evaluated in a 2-step fashion. First, secondary LT for tumor recurrence after resection (n = 17) was compared with primary LT (n = 195), to assess the risk and the outcome of secondary LT in patients who effectively succeeded to be treated by this approach. Second, primary resection in transplantable patients (n = 98) was compared with that of primary LT (n = 195) on an intention-to-treat basis, to assess the outcome of each treatment strategy and to determine the proportion of resected patients likely to be switched for secondary LT. Transplantability of resected patients was retrospectively determined according to selection criteria of LT for HCC. RESULTS: Operative mortality (< or =2 months) of secondary LT was significantly higher than that of primary LT (28.6% versus 2.1%; P = 0.0008) as was intraoperative bleeding (mean transfused blood units, 20.7 versus 10.5; P = 0.0001). Tumor recurrence occurred more frequently after secondary than after primary LT (54% versus 18%; P = 0.001). Posttransplant 5-year overall survival was 41% versus 61% (P = 0.03), and disease-free survival was 29% versus 58% (P = 0.003) for secondary and primary LT, respectively.Of 98 patients treated by resection while initially eligible for transplantation, only 20 (20%) were secondarily transplanted, 17 of whom (17%) for tumor recurrence and 3 (3%) for hepatic decompensation. Transplantability of tumoral recurrence was 25% (17 of 69 recurrences). Compared with primarily transplanted patients, transplantable resected patients had a decreased 5-year overall survival (50% versus 61%; P = 0.05) and disease-free survival (18% versus 58%; P < 0.0001), despite the use of secondary LT.On a multivariate analysis including 271 patients eligible for transplantation and treated by either liver resection or primary LT, liver resection alone (P < 0.0001; risk ratio [RR] = 3.27) or liver resection with secondary LT (P < 0.05; RR= 1.87) emerged as negative independent factors of disease-free survival as compared with primary LT. A number of nodules > 3 (P = 0.002; RR= 2.02) and a maximum tumor size exceeding 30 mm (P < 0.0001; RR=1.93) were also predictive of lower disease-free survival. CONCLUSIONS: LT after liver resection is associated with a higher operative mortality, an increased risk of recurrence, and a poorer outcome than primary LT. In addition, liver resection as a bridge to LT impairs the patient transplantability and the chance of long-term survival of cirrhotic patients with HCC. Primary LT should therefore remain the ideal choice of treatment of a cirrhotic patient with HCC, even when the tumor is resectable.  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