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   7574篇
  免费   297篇
  国内免费   56篇
耳鼻咽喉   43篇
儿科学   154篇
妇产科学   35篇
基础医学   979篇
口腔科学   147篇
临床医学   376篇
内科学   2398篇
皮肤病学   50篇
神经病学   465篇
特种医学   286篇
外科学   1110篇
综合类   35篇
预防医学   202篇
眼科学   43篇
药学   526篇
中国医学   62篇
肿瘤学   1016篇
  2023年   30篇
  2022年   56篇
  2021年   113篇
  2020年   54篇
  2019年   76篇
  2018年   101篇
  2017年   70篇
  2016年   111篇
  2015年   119篇
  2014年   164篇
  2013年   229篇
  2012年   386篇
  2011年   438篇
  2010年   238篇
  2009年   246篇
  2008年   440篇
  2007年   479篇
  2006年   489篇
  2005年   534篇
  2004年   529篇
  2003年   524篇
  2002年   575篇
  2001年   113篇
  2000年   114篇
  1999年   112篇
  1998年   190篇
  1997年   143篇
  1996年   114篇
  1995年   104篇
  1994年   102篇
  1993年   112篇
  1992年   79篇
  1991年   67篇
  1990年   82篇
  1989年   66篇
  1988年   45篇
  1987年   49篇
  1986年   39篇
  1985年   37篇
  1984年   31篇
  1983年   26篇
  1982年   38篇
  1981年   39篇
  1980年   38篇
  1979年   20篇
  1978年   24篇
  1977年   17篇
  1976年   19篇
  1974年   15篇
  1973年   11篇
排序方式: 共有7927条查询结果,搜索用时 15 毫秒
91.
A 1-year-old boy with a bronchopulmonary foregut malformation presented with a large mediastinal bronchogenic cyst associated with pulmonary sequestration, a cervical esophageal duplication cyst, a bronchial communication between these cysts, and 2 small bronchogenic cysts around the communication. These lesions were resected followed by an uneventful recovery. J Pediatr Surg 38:E2.  相似文献   
92.
93.
The aim of the present study was to ascertain the role of social support and individual styles of coping on employee well‐being. The subjects were intermediate managers working for a zipper and sash manufacturing company in Japan. Measurements were made of the following: depression using the Self‐rating Depression Scale (SDS), job demand, job control, social support using Karasek's Job Content Questionnaire, and of three coping styles: emotion‐oriented coping, task‐oriented coping and avoidance‐oriented coping using the Coping Inventory for Stressful Situations (CISS). Data was analysed by structural equation modeling. Each coping style had a direct effect on depression. Emotion‐oriented coping had a negative effect. On the other hand, task‐oriented coping and avoidance‐oriented coping had a positive effect. Moreover, there was an indirect effect that coping styles precede and determine the perception of social support as well as job demand and control. Social support showed a direct positive effect on depression. However, the overall impact on employee well‐being was greater for individual coping styles as compared to social support from either supervisors or co‐workers. The present study showed the effectiveness of coping strategies in the workplace. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
94.
BACKGROUND: Cytokeratin immunostaining is the most common method used to identify micrometastatic cancer cells from the lymph nodes. However, contamination with hyalinized cytokeratin particles, frequently observed in the lymph nodes of esophageal cancer patients, can lead to misinterpretation of cytokeratin immunostaining. MATERIALS AND METHODS: Cytokeratin immunostaining (AE1/AE3) of surgically removed lymph nodes was performed for 41 cases of node-negative, but locally advanced (T3, T4), esophageal cancer patients. Cytokeratin immunoreactivity (CK) was classified as micrometastasis (MM) or cytokeratin deposit (CD) by the presence or absence of tumor nuclei in serial sections given hematoxylin-eosin staining. RESULTS: CK (+) was observed in 18 patients (44%), including 11 with MM (+) (27%) and 10 with CD (+) (24%). There was no correlation between MM and CD, and neither was associated with clinicopathological factors, except for a high incidence of preoperative chemotherapy in CD (+) patients. The presence of CK did not affect postoperative survival of esophageal cancer patients at this limited stage, showing a 5-year survival rate of 57% for CK (+) and 64% for CK (-) (P = 0.6064). Interestingly, patients with MM (+) showed poorer prognosis than MM (-) (5-year survival: 28% vs 79%, P = 0.0188), while CD (+) patients tended to display better prognosis than CD (-) ones (5-year survival: 78% vs 56%, P = 0.1860). CONCLUSIONS: Evaluation by cytokeratin immunostaining of lymph nodes requires careful discrimination of CD from MM, in order to allow MM to be used as a prognostic factor for esophageal cancer patients.  相似文献   
95.
Purpose

The pathology of dropped head syndrome (DHS) is diverse, and reports of surgery for DHS are scarce. We aimed to describe surgery for DHS and to investigate the surgical outcomes thereof.

Methods

We enrolled 40 consecutive patients (six males and 34 females; average age at surgery, 72.0 years) with DHS who underwent correction surgeries at a single institute. Short fusion (SF), with the extent of fixation mainly at the cervical region, was performed for 27 patients; long fusion (LF), involving the cervical and thoracic spine, for 13. Clinical and radiological outcomes were investigated, and factors analyzed using the Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ).

Results

All patients were able to gaze horizontally at the follow-up. Instances of five transient C5 palsy results, and five distal junctional kyphosis results were found, but no revisions were reported due to recurrence. Patients whose T1 slope-20° was smaller than the C2–7 angle postoperatively exhibited better clinical outcomes in the three domains of the JOACMEQ, regardless of the extent of fixation.

Conclusion

For cases where the T1 slope is relatively small, and approximately 10° of cervical lordosis is predicted to be obtained postoperatively, SF is appropriate. Alternatively, for cases with higher T1 slope, obtaining a cervical lordosis over 20° has a risk of postoperative complications. For such cases, it is an option to perform an LF involving the cervical and thoracic spine.

  相似文献   
96.
OBJECTIVE: The aim of this study was to evaluate the efficacy of the objective radiologic analysis of high-resolution computed tomographic images of small peripheral non-small cell lung cancer and to select the candidates for curative limited resection. METHODS: High-resolution computed tomographic images of 146 surgically resected T1 N0 M0 peripheral non-small cell lung cancers were analyzed by using National Institutes of Health image software and classified on the basis of the percentage of ground-glass opacity within the tumor. RESULTS: Eighty-seven percent of tumors with ground-glass opacity ratios of 90% to 100% (type I) were diagnosed as noninvasive bronchioloalveolar carcinoma, whereas 55.6% of tumors with ground-glass opacity ratios of 50% to 89% (type II) consisted of adenocarcinoma. Tumors with ground-glass opacity ratios of 50% or more (type I/II) had no nodal involvement, whereas nodal metastases were identified in 20.0% of tumors with ground-glass opacity ratios of 10% to 49% (type III) and 24.4% of tumors with ground-glass opacity ratios of less than 10% (type IV). No tumors with ground-glass opacity ratios of 50% or more showed vessel infiltration, except for one lesion with a ground-glass opacity ratio of 50%. The 3-year disease-free survival was 97.7% for type I/II, 86.1% for type III, and 78.5% for type IV tumors. CONCLUSIONS: The objective quantitative radiologic analysis with National Institutes of Health image software exhibited a good correlation with the histologic classification, pathologic invasiveness, and postoperative outcome of small peripheral lung cancer. Patients with tumors that have ground-glass opacity ratios of greater than 50% are considered to be possible candidates for limited pulmonary resection.  相似文献   
97.
The Carpentier-Edwards pericardial bioprosthesis has been markedly improved in the long-term results and valve-related complications including valve dysfunction, compared to the previous generation bioprosthesis. We report a patient in whom transient prosthetic valve regurgitation and hemolysis occurred early after mitral valve replacement using a Carpentier-Edwards pericardial bioprosthesis and were resolved by preservative therapy. The patient was a 77-year-old female diagnosed with severe mitral valve stenosis and insufficiency. She underwent mitral valve replacement with a Carpentier-Edwards pericardial bioprosthesis. Opening and closing of the three leaflets looked good on intraoperative transesophageal echocardiography (TEE). The only prosthetic valve regurgitation was evident at the central region where the leaflets form coaptation, and no abnormal findings were seen. Serum lactate dehydrogenase (LDH) was decreased to 405 U/l after surgery. However, LDH again began to increase on the 3rd day after surgery and it increased to 1,830 U/l on the 14th day after surgery. Hemolytic urine was detected on 10th day after surgery. PVL was not detected, but moderate abnormal regurgitation from the outside of the stent pocket was detected on TEE. Revision of valve replacement was considered, but LDH thereafter to 393 U/l on 41st day after surgery. The TEE was repeated, and only a trace of central jet was detected without abnormal regurgitation, unlike the previous examination. The patient did not develop any complications thereafter and was discharged on 47th day after surgery. LDH was nearly normal at the time of discharge.  相似文献   
98.
AIM: To clarify whether hepatocellular carcinoma (HCC) originates from hepatic progenitor cells and whether there is any correlation with the clinicopathologic factors of HCC, we reviewed 217 resected HCC specimens. METHODS: Immunohistochemical examination of cytokeratin (CK) 7, CK19, CD34, and CD117 (c-KIT) was performed. Overexpression of CK7 and CK19 indicates differentiation from cholangiocellular and hepatic progenitor cells, while overexpression of CD34 and CD117 indicates hepatic stem cells. Fresh specimens were obtained from 20 HCC patients for mutation of the c-KIT gene. RESULTS: CK7, CK19, and CD117 were positive in 41, 9.7, and 0.9% of the HCC specimens, respectively, and CD34 was never positive. None of the fresh HCC specimens demonstrated a c-KIT mutation. CK19 positivity was significantly correlated with a positive hepatitis B core antibody, and with poor survival outcome, and tended to correlate with poor histologic differentiation. CONCLUSION: These results suggest that: (i) about 10% of HCCs with typical histologic features originate from an intermediate hepatic progenitor cell, such as the canal of Hering and oval cells in the rat, or acquire the characteristics of cholangiocellular epithelium by metaplasia; (ii) HCC with typical histologic features rarely originates from hepatic stem cells, and (iii) patients with CK19-positive HCC have a poor prognosis.  相似文献   
99.

Background

To date, several training and evaluation systems for endoscopic surgery have been developed, such as virtual-reality simulators and box trainers. However, despite current advances in these objective assessments, no functional brain studies during learning of endoscopic surgical skills have been carried out. In the present study, we investigated cortical activation using near-infrared spectroscopy (NIRS) during endoscopic surgical tasks.

Study design

A total of 21 right-handed subjects, comprising 4 surgical experts, 4 trainees, and 13 novices, participated in the study. Suturing and knot-tying tasks were performed in a box trainer. Cortical activation was assessed in all subjects by task-related changes in hemoglobin (Hb) oxygenation using NIRS.

Results

In surgical experts and novices with no experience of endoscopic surgical training, we found no changes in oxy-Hb, deoxy-Hb or total-Hb levels in any of the frontal channels. In surgical trainees and one novice with experience of endoscopic surgical training, we found significant increases in oxy-Hb and total-Hb levels in most of the frontal channels. There were significant differences in oxy-Hb and total-Hb levels in CH-19 between surgical experts and trainees (p = 0.02 for both), and between surgical trainees and novices with no experience of endoscopic surgical training (p = 0.008 for both). Furthermore, additional training increased oxy-Hb levels in the frontal cortex of novices with no experience of endoscopic surgical training but had no such effect on surgical experts.

Conclusions

The present data suggest that NIRS is a feasible tool for assessing brain activation during endoscopic surgical tasks, and may have a large impact on the future development of teaching, training, and assessment methods for endoscopic surgical skills.  相似文献   
100.
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