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   9010篇
  免费   559篇
  国内免费   58篇
耳鼻咽喉   71篇
儿科学   201篇
妇产科学   126篇
基础医学   857篇
口腔科学   185篇
临床医学   799篇
内科学   2337篇
皮肤病学   84篇
神经病学   1194篇
特种医学   293篇
外科学   1597篇
综合类   21篇
一般理论   1篇
预防医学   376篇
眼科学   217篇
药学   476篇
中国医学   14篇
肿瘤学   778篇
  2024年   9篇
  2023年   125篇
  2022年   210篇
  2021年   400篇
  2020年   233篇
  2019年   307篇
  2018年   315篇
  2017年   242篇
  2016年   279篇
  2015年   294篇
  2014年   420篇
  2013年   515篇
  2012年   792篇
  2011年   722篇
  2010年   375篇
  2009年   373篇
  2008年   559篇
  2007年   538篇
  2006年   560篇
  2005年   459篇
  2004年   412篇
  2003年   371篇
  2002年   325篇
  2001年   71篇
  2000年   59篇
  1999年   69篇
  1998年   46篇
  1997年   39篇
  1996年   48篇
  1995年   30篇
  1994年   34篇
  1993年   28篇
  1992年   42篇
  1991年   37篇
  1990年   23篇
  1989年   35篇
  1988年   21篇
  1987年   15篇
  1986年   21篇
  1985年   20篇
  1984年   28篇
  1983年   19篇
  1982年   14篇
  1981年   17篇
  1980年   8篇
  1979年   14篇
  1977年   5篇
  1975年   6篇
  1974年   10篇
  1973年   5篇
排序方式: 共有9627条查询结果,搜索用时 15 毫秒
61.

Purpose  

This article aims to provide an overview of how spinal deformities can alter normal spine and thoracic cage growth.  相似文献   
62.
63.
The authors report on two gonadotropic carcinomas of the adenohypophysis that occurred in a55-year-old man (Case 1) and a 53-year-old woman (Case 2), with signs of mass effect and amenorrhea, respectively. Both lesions were macroadenomas. The tumor in Case 1 metastasized to dura mater, skull, nasal sinus, and larynx 2 years after patient presentation, whereas that in Case 2 spread to vertebral bodies and ribs after a 19-year latency. Histologically, the primary, recurrent, and metastatic lesions in Case 1 featured brisk mitotic activity and high MIB-1 levels as well as p53 labeling indices. Immunoreactivity for HER-2/neu was assessable only in rare neoplastic cells of the second recurrence and in 80% of cells of the dural metastasis. Low-level HER-2/neu gene amplification was evident in the recurrent tumors and metastasis. The sellar and metastatic tumors in Case 2 resembled benign gonadotropic adenoma with oncocytic change; p53 accumulation, HER-2/neu overexpression, and HER-2/neu gene amplification were not present. The results indicate that low-level amplification of the HER-2/neu gene might be associated with pituitary carcinomas in which more aggressive behavior is seen. Further studies are needed to determine whether HER-2/neu plays a role in the pathogenesis of pituitary carcinoma.  相似文献   
64.
Chappell ET  Moure FC  Good MC 《Neurosurgery》2003,52(3):624-31; discussion 630-1
OBJECTIVE: To compare a novel diagnostic radiological technique, computed tomographic angiography (CTA), with the standard method, namely digital subtraction angiography (DSA), in the diagnosis of cerebral aneurysms. METHODS: A comprehensive search of the world literature on CTA was performed. Articles that reported on prospective comparisons of CTA and DSA in the evaluation of patients suspected of harboring cerebral aneurysms were selected for data extraction. Suitable statistical methods were applied to the extracted data for meta-analysis. RESULTS: Twenty-one references met the criteria for use in the meta-analysis. Unweighted calculations based on data for 1251 patients resulted in a sensitivity of 0.933 (93.3%; range, 75.4-100%) and a specificity of 0.878 (87.8%; range, 0-100%). When the studies were weighted for the number of patients in each study, the sensitivity decreased slightly, to 0.927 (92.7%), and the specificity decreased more substantially, to 0.772 (77.2%). CONCLUSION: On the basis of this meta-analysis, DSA remains the standard method. However, many who use CTA have reported it to be as good as or better than DSA in the diagnosis and treatment of cerebral aneurysms, as well as being of less risk and discomfort to their patients and easier and less expensive to perform.  相似文献   
65.
We describe five primary tumors of the adenohypophysis featuring mitochondrion-rich spindle cells. The patient ages ranged from 53 to 71 years (mean 61.6 years); two were female. All presented with panhypopituitarism. Two also had visual field defect. On neuroimaging all tumors showed suprasellar extension and were indistinguishable from pituitary adenoma. None showed imaging or operative evidence of dural involvement. All were gross totally removed: four by transsphenoidal surgery and one by frontal craniotomy. Follow-up ranged from 2 to 68 months (mean 35.4 months). No recurrences were noted. The clinical workup was noncontributory in all but two patients: one (case no. 4) with an oncocytic thyroid adenoma and another (case no. 5) with squamous carcinoma of both the uterine cervix and of vocal cord. Histologically, the five tumors were composed mainly of fascicles of spindle cells with eosinophilic, granular cytoplasm. Mitoses were rare and necrosis was absent. Neoplastic cells were immunoreactive for vimentin, epithelial membrane antigen, S-100 protein, and galectin-3. Stains for pituitary hormones, synaptophysin, chromogranin, glial fibrillary acidic protein, cytokeratin CAM5.2, smooth muscle actin, CD34, and CD68 were negative. No thyroglobulin immunoreactivity was noted in the tumor of case no. 4. Ultrastructurally, the neoplastic cells contained numerous mitochondria with lamellar cristae. The neoplastic cells were linked by intermediate junctions and desmosomes. No secretory granules were noted. The histologic, immunohistochemical, and fine structural features of these tumors were unlike those of pituitary adenoma or any other primary sellar tumor. A derivation from adenohypophyseal folliculostellate cells is suggested.  相似文献   
66.

Objective

The aim of the present study was to compare the outcomes of conservative versus surgical treatment for acute appendicitis.

Background

Although acute appendicitis is a common disease, great debate exists regarding the appropriate management of patients. Conservative treatment has shown positive results in several RCTs, eliciting questions about indications to surgery, therapeutic appropriateness and ethical conduct.

Methods

Data were prospectively collected; a Propensity Score-based matching method was implemented in order to reduce bias arising from characteristics of the patients; a proportion of patients (69 in total) were excluded to obtain two comparable groups of study (1a). Main outcomes of the study were: failure rate, in-hospital length of stay (at first admission and cumulative), post-discharge absence from work. Within the medical group, failure was defined as the necessity for appendectomy after conservative treatment, while it was identified with complications and negative appendectomy within the surgical group (Failure 1). In parallel, an additional definition of failure was proposed (Failure 2) and excluded negative appendectomy from the reasons for failure within the surgical group (5b).

Results

The failure rate for the conservative treatment resulted to be inferior, as compared to the surgical treatment (16.5 vs. 28.4%, OR 0.523 p = 0.019), considering negative appendectomy as a reason for failure. When excluding negative appendectomy from the definition of failure, medical and surgical treatment appeared to perform equally (failure rate: 16.5 vs. 18.3%, OR 1.014 p = 0.965). Patients managed conservatively showed to have a shorter length of stay at first admission than the patients who underwent appendectomy (3.11 vs. 4.11 days, β = ?0.628 days, p < 0.0001). A lower number of lost work days after discharge resulted from a conservative approach (6 vs. 14.64 days, β = ?8.7 days, p < 0.0001).

Conclusions

Considering each outcome as part of a wide-angle analysis, the conservative management of acute appendicitis resulted to be safe and effective in the selected group of patients. In terms of failure rate, the medical treatment resulted to perform as effectively as surgical treatment, if negative appendectomy was excluded from failure, or better, when negative appendectomy was included in the definition of failure. A diminished length of stay during the first admission and a reduced number of lost work days were evident with a conservative approach. The comparison between medical and surgical treatment for acute appendicitis requires a change in perspective, from a spare ‘effectiveness analysis’ to a more thorough ‘appropriateness analysis’: in the present study, the conservative treatment showed to address the clinical requirements in terms of therapeutic appropriateness. Although acute appendicitis is considered a ‘surgical disease’, increasing evidence supports the effectiveness and safety of a conservative approach for selected groups of patients.
  相似文献   
67.

Introduction and hypothesis

Uterine-sparing procedures could be attractive in patients concerned about fertility preservation and corporeal image changes. Transvaginal uterosacral ligaments (USLs) hysteropexy can provide a mesh-free technique for uterine suspension. This video is intended to serve as a tutorial for surgical steps.

Methods

A 38-year-old woman with symptomatic stage III POP desired preserving fertility. After proper counseling, the patient was admitted for vaginal hysteropexy through bilateral high USL suspension according to the featured technique.

Results

Prolapse repair was successfully achieved without complications. We had already published a series of 20 cases that confirmed that transvaginal USLs hysteropexy is a promising technique for correcting genital prolapse with uterus preservation.

Conclusion

Transvaginal USLs hysteropexy provides a feasible technique for apical support without the use of prosthetic material. This procedure could be attractive to women who desire a uterine-sparing surgical option.
  相似文献   
68.
Multicomponent models based on the Lattice Boltzmann Method (LBM) have clear advantages with respect to other approaches, such as good parallel performances and scalability and the automatic resolution of breakup and coalescence events. Multicomponent flow simulations are useful for a wide range of applications, yet many multicomponent models for LBM are limited in their numerical stability and therefore do not allow exploration of physically relevant low viscosity regimes. Here we perform a quantitative study and validations, varying parameters such as viscosity, droplet radius, domain size and acceleration for stationary and translating droplet simulations for the color-gradient method with central moments (CG-CM) formulation, as this method promises increased numerical stability with respect to the non-CM formulation. We focus on numerical stability and on the effect of decreasing grid-spacing, i.e. increasing resolution, in the extremely low viscosity regime for stationary droplet simulations. The effects of small- and large-scale anisotropy, due to grid-spacing and domain-size, respectively, are investigated for a stationary droplet. The effects on numerical stability of applying a uniform acceleration in one direction on the domain, i.e. on both the droplet and the ambient, is explored into the low viscosity regime, to probe the numerical stability of the method under dynamical conditions.  相似文献   
69.

Introduction

In renal cell carcinoma (RCC), lymph node status at preoperative imaging is affected by a non-negligible false-positive rate. We aimed to investigate which factors are related to a concordance between clinical suspicion and pathological confirmation of lymph node invasion (LNI).

Methods

At a single tertiary care institution, 2954 RCC patients underwent either partial or radical nephrectomy. For the aim of the study, only clinically positive lymph node cases were included (cN1). Statistical analyses assessed the concordance between preoperative and pathological nodal status.

Results

Preoperative axial CT scans revealed 424 (14.4 %) patients showing at least one enlarged lymph node suspected for LNI (cN1). All lymphadenopathies were removed at surgery, and LNI was pathologically confirmed (pN1) in 122 patients (28.8 %). When focusing the analyses on clinical characteristics (variables known before surgery), metastases at diagnosis [OR 3.0 (95 %1.9–4.8), p < 0.001] and tumor size [OR 1.1 (95 % 1.1–1.2), p < 0.001] were the two most informative predictors of concordance between clinical and pathological nodal status. Concordance was also more likely in patients with papillary type II tumors (55.6 %) relative to papillary type I (38.1 %), clear cell (27.7 %) and chromophobe (8.3 %) tumors. At multivariable analyses, none of the considered blood markers resulted to be independently associated with LNI.

Conclusions

Roughly 70 % of patients showing a suspected lymph node preoperatively do not show LNI at the final pathological report. Among patients with clinically positive nodes, clinical tumor size and metastases at diagnosis represent the most informative and independent predictors of confirmed LNI at final pathology.
  相似文献   
70.
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