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   2247篇
  免费   102篇
  国内免费   19篇
耳鼻咽喉   10篇
儿科学   106篇
妇产科学   25篇
基础医学   174篇
口腔科学   61篇
临床医学   226篇
内科学   398篇
皮肤病学   22篇
神经病学   75篇
特种医学   219篇
外科学   298篇
综合类   118篇
预防医学   80篇
眼科学   304篇
药学   147篇
中国医学   16篇
肿瘤学   89篇
  2023年   18篇
  2022年   64篇
  2021年   77篇
  2020年   41篇
  2019年   57篇
  2018年   76篇
  2017年   51篇
  2016年   73篇
  2015年   70篇
  2014年   97篇
  2013年   97篇
  2012年   155篇
  2011年   170篇
  2010年   119篇
  2009年   86篇
  2008年   150篇
  2007年   152篇
  2006年   125篇
  2005年   112篇
  2004年   99篇
  2003年   77篇
  2002年   60篇
  2001年   20篇
  2000年   25篇
  1999年   33篇
  1998年   28篇
  1997年   19篇
  1996年   21篇
  1995年   14篇
  1994年   17篇
  1993年   14篇
  1992年   11篇
  1991年   14篇
  1990年   16篇
  1989年   21篇
  1988年   23篇
  1987年   9篇
  1986年   8篇
  1985年   12篇
  1984年   8篇
  1983年   8篇
  1981年   2篇
  1980年   2篇
  1978年   3篇
  1977年   2篇
  1976年   2篇
  1973年   3篇
  1967年   1篇
  1965年   1篇
  1962年   1篇
排序方式: 共有2368条查询结果,搜索用时 15 毫秒
21.
22.
Infertility affects about 15-20% couples attempting pregnancy and in about half cases the problem lies in the male. Among the sperm parameters, linear progressive motility is one of the most important predictors of fertility potential. Though genetic and chromosomal abnormalities are important aetiological factors in the pathogenesis of male infertility, the mechanism involved in impaired sperm motility is poorly understood. Here we report mitochondrial DNA (mtDNA) mutations with increased seminal reactive oxygen species (ROS) levels and higher DNA fragmentation level in the sperm resulting in decreased ATP production which plays an important role in sperm motility defect. Thus it is important to understand the aetiology of asthenozoospermia and to distinguish if infertile men harbour nuclear or mtDNA mutation as they are very important prognostic markers. This case study also highlights that routine semen parameters are very modest predictors of fertility outcome but ROS estimation and DNA integrity analysis by Comet assay have better diagnostic and prognostic capabilities. Thus this study is a detailed and comprehensive workup of an infertile asthenozoospermic male.  相似文献   
23.
Fluids balanced to avoid acid-base disturbances may be preferable to saline, which causes metabolic acidosis in high volume. We evaluated acid-base and bio-energetic effects of haemodilution with a crystalloid balanced on physical chemical principles, versus crystalloids causing metabolic acidosis or metabolic alkalosis. Anaesthetised, mechanically ventilated Sprague-Dawley rats (n=32, allocated to four groups) underwent six exchanges of 9 ml crystalloid for 3 ml blood. Exchange was with one of three crystalloids with strong ion difference (SID) values of 0, 24 (balanced) and 40 mEq/l. Controls did not undergo haemodilution. Mean haemoglobin concentration fell to approximately 50 g/l after haemodilution. With SID 24 mEq/l fluid, metabolic acid-base remained unchanged. Dilution with SID 0 mEq/l and 40 mEq/l fluids caused a progressive metabolic acidosis and alkalosis respectively. Standard base excess (SBE) and haemoglobin concentration were directly correlated in the SID 0 mEq/l group (R2 = 0.61), indirectly correlated in the SBE 40 mEq/l group (R2 = 0.48) and showed no correlation in the SID 24 mEq/l group (R2 = 0.003). There were no significant differences between final ileal values of CO2 gap, nucleotides concentration, energy charge, or luminal lactate concentration. SID 40 mEq/l crystalloid dilution caused a significant rise in subcutaneous lactate. In this group mean kidney ATP concentration was significantly less than controls and renal energy charge significantly lower than SID 0 mEq/l and control groups. We conclude that a crystalloid SID of 24 mEq/l provides balanced haemodilution. Bio-energetic perturbations with higher SID haemodilution may be more severe and need further investigation.  相似文献   
24.

Purpose

To evaluate difference in accuracy of pedicle screw insertion in thoracic and lumbosacral spine using a straight pedicle probe vis-à-vis a curved one.

Methods

Prospective, comparative, non-randomized, single-blind study. Straight and curved pedicle probes used on opposite sides of same vertebra in patients undergoing thoracolumbar pedicle screw fixation for various indications. Postoperative blinded evaluation for pedicle breaches done with a CT scan. Pedicle breaches graded as grade 0: no breach, grade 1: <2 mm, grade 2: 2–4 mm and grade 3: >4 mm breach.

Results

After appropriate statistical power analysis, 300 screws inserted in 59 patients from T4–L5 levels. No significant differences noted between the two probes in terms of screw length [two-tailed p = 0.16]; grade 0 screws [two-tailed p = 0.49] or screws with grade 2/3 breaches [two-tailed  p = 0.68]. With the right-hand-dominant operating-surgeon standing to left of patient during surgery, no difference noted between the two probes for either the right or left-side pedicle screw insertion [two-tailed p = 1]. Repeating these tests in the subset of thoracic pedicle screws too, revealed no significant difference.

Conclusions

No significant difference in outcome of pedicle screw insertion with either a straight or a curved pedicle probe.  相似文献   
25.
Needle core biopsy guided with mammography: a study of cost- effectiveness   总被引:2,自引:0,他引:2  
Lindfors  KK; Rosenquist  CJ 《Radiology》1994,190(1):217
  相似文献   
26.
PURPOSE: We describe our technique and clinical experience with application of the ureteral access sheath for single access ablation of staghorn and partial staghorn calculi. MATERIALS AND METHODS: We retrospectively reviewed our experience with 9 patients who underwent percutaneous nephrolithotomy for staghorn (6) or partial staghorn (3) renal calculi using a combined antegrade and retrograde approach. Patient data, operative parameters, efficacy of stone ablation and convalescence parameters were reviewed. RESULTS: Mean operative time for the primary procedure was 3.1 hours with a mean estimated blood loss of 290 ml. Postoperatively, the mean analgesic requirement was 33.2 mg. MSO(4) equivalents. Hospital stay was 3.2 days. There were no major and 4 minor (44%) complications. No patient required transfusion. Complete stone clearance was achieved in 7 of the 9 cases (78%) using a single percutaneous nephrostomy tract. CONCLUSIONS: Our preliminary clinical experience using the ureteral access sheath during percutaneous nephrolithotomy for simultaneous antegrade and retrograde stone treatment has been favorable. A large renal stone burden can be successfully managed with a single percutaneous access and limited blood loss.  相似文献   
27.
We present a prospective study of patients with tuberculosis of the dorsal, dorsolumbar and lumbar spine after combined anterior (radical debridement and anterior fusion) and posterior (instrumentation and fusion) surgery. The object was to study the progress of interbody union, the extent of correction of the kyphosis and its maintenance with early mobilisation, and the incidence of graft and implant-related problems. The American Spinal Injury Association (ASIA) score was used to assess the neurological status. The mean preoperative vertebral loss was highest (0.96) in the dorsal spine. The maximum correction of the kyphosis in the dorsolumbar spine was 17.8 degrees. Loss of correction was maximal in the lumbosacral spine at 13.7 degrees. All patients had firm anterior fusion at a mean of five months. The incidence of infection was 3.9% and of graft-related problems 6.5%. We conclude that adjuvant posterior stabilisation allows early mobilisation and rehabilitation. Graft-related problems were fewer and the progression and maintenance of correction of the kyphosis were better than with anterior surgery alone. There is no additional risk relating to the use of an implant either posteriorly or anteriorly even when large quantities of pus are present.  相似文献   
28.
Intravascular ultrasound is a novel endovascular imaging technology that is useful as an imaging tool for diagnosis and treatment of arterial and venous pathologies. Intravascular ultrasound is particularly useful as a decision-making tool in the endovascular management of vascular pathologies. Recently the aorta has become increasingly amenable to endovascular technology, and with the advent of intravascular ultrasound detailed imaging, using intravascular ultrasound permits the diagnosis and endovascular management of various complex aortic pathologies affecting the abdominal and thoracic aorta. Various aortic pathologies including thoracic and abdominal aortic aneurysms, type B dissections, penetrating aortic ulcers, coarctation of the aorta, and many other aortic pathologies, which were once only amenable by open surgical repair are increasingly being managed with endoluminal technology. As experience develops with this technology, more complex aortic pathologies would become readily amenable to advanced endovascular interventions.  相似文献   
29.
异基因造血干细胞移植(hematopoieticcelltransplantation,HCT)后代谢综合征的发生主要由预处理导致的神经激素系统紊乱、血管内皮损伤、移植物的免疫和炎症作用以及继发的移植物抗宿主病及其治疗等引起。对代谢综合征及其组分(糖尿病、高血压、血脂紊乱等)的筛查可以尽早地调整治疗策略,控制危险因素的发生,进而降低远期的心血管疾病的发生率和致死率。为此,美国的研究人员回顾性分析了86例异基因HCT受者代谢综合征的发生情况,并与代谢综合征在普通人群中的流行情况进行比较。  相似文献   
30.
DNA amplification by Polymerase Chain Reaction (PCR) of a repetitive sequence specific for Mycobacterium tuberculosis, from clinical samples of extra pulmonary origin were evaluated. The 123 base pair fragment of the insertion element IS 6110 in Mycobacterium tuberculosis was amplified. A total of 50 samples were analysed by PCR and compared with culture on Lowenstein-Jensen medium (LJ) and the clinical findings of the patient. Out of the total 26 samples were positive by PCR, while only seven grew the bacilli in culture. 24 samples were negative by PCR and culture. All the seven samples that grew the bacilli on culture were positive by PCR. In remaining 19 cases that were positive by PCR but did not grow the bacilli clinical features, radiological findings and Mantoux test were strongly suggestive of M. tuberculosis. All the amplification negative cases had no positive evidence of tuberculosis but were being followed up. When correlated with culture and clinical history the sensitivity of PCR for the diagnosis of active tuberculosis was 100%. However, the specifity was only 55.8% as culture on LJ (Gold Standard) was positive in only 7 samples out of 26 samples that were positive by PCR.KEY WORDS: DNA Amplification, IS 6110, Mycobacterium tuberculosis.  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