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   14182篇
  免费   670篇
  国内免费   154篇
耳鼻咽喉   64篇
儿科学   241篇
妇产科学   380篇
基础医学   234篇
口腔科学   49篇
临床医学   7928篇
内科学   818篇
皮肤病学   25篇
神经病学   182篇
特种医学   1188篇
外科学   1422篇
综合类   1248篇
预防医学   395篇
眼科学   81篇
药学   455篇
  1篇
中国医学   57篇
肿瘤学   238篇
  2024年   5篇
  2023年   54篇
  2022年   233篇
  2021年   372篇
  2020年   315篇
  2019年   256篇
  2018年   477篇
  2017年   386篇
  2016年   436篇
  2015年   560篇
  2014年   983篇
  2013年   859篇
  2012年   1123篇
  2011年   1133篇
  2010年   1121篇
  2009年   925篇
  2008年   911篇
  2007年   770篇
  2006年   782篇
  2005年   657篇
  2004年   539篇
  2003年   332篇
  2002年   329篇
  2001年   336篇
  2000年   281篇
  1999年   194篇
  1998年   117篇
  1997年   87篇
  1996年   82篇
  1995年   63篇
  1994年   40篇
  1993年   36篇
  1992年   25篇
  1991年   32篇
  1990年   19篇
  1989年   19篇
  1988年   21篇
  1987年   15篇
  1986年   9篇
  1985年   17篇
  1984年   6篇
  1983年   7篇
  1982年   4篇
  1981年   5篇
  1980年   6篇
  1979年   7篇
  1978年   6篇
  1977年   5篇
  1976年   6篇
  1973年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
This study investigated the age-related changes in muscle quantity and quality in the trunk and limbs of women. A total of 128 females were divided into four age groups: young, middle-aged, young-old and old-old. Muscle thickness (MT) and echo intensity (EI) of the biceps brachii, quadriceps femoris, rectus abdominis, external oblique, internal oblique and transversus abdominis were measured using B-mode ultrasonography. The EIs of the biceps brachii, quadriceps femoris and transversus abdominis were significantly higher in the middle-aged group than in the young group; however, there were no significant differences in MT. Compared with the young group, all other groups had significant changes in both MT and EI of the rectus abdominis, external oblique and internal oblique muscles. Thus, qualitative changes in muscle may occur earlier than quantitative changes, and loss of muscle mass may occur earlier in the superficial abdominal muscles than in the other muscles.  相似文献   
42.
Thyroid imaging is indicated to evaluate congenital hypothyroidism during newborn screening or in cases of a palpable thyroid mass in children and adolescents. This pictorial essay reviews the ultrasonography (US) of thyroid diseases in children and adolescents, including normal thyroid gland development, imaging features of congenital thyroid disorders (dysgenesis, [aplasia, ectopy, hypoplasia], dyshormonogenesis, transient hypothyroidism, thyroglossal duct cyst), diffuse thyroid disease (Grave''s disease, Hashimoto''s thyroiditis, and suppurative thyroiditis), and thyroid nodules. The primary imaging modalities for evaluating thyroid diseases are US and radionuclide scintigraphy. Additionally, US can be used to guide aspiration of detected nodules.  相似文献   
43.
Ultrasonography of the bones and joints has gained considerable ground in the field of rheumatology over the past decade and is now used in everyday practice both for diagnostic purposes and to guide local injections. However, the use of ultrasonography is virtually confined to the peripheral joints, whereas spinal diseases make a major contribution to rheumatology practice. Studies have established that ultrasonography of the lumbar spine is feasible. Adequate equipment and familiarity with spinal sonoanatomy are required. In this update, we suggest starting with a systematic examination of the lumbar spine to assess the various anatomic structures, from the thoracolumbar fascia superficially to the posterior part of the vertebras at the deepest level. The ligaments, erector spinae muscles, facet joints, and transverse processes can be visualized. Ultrasonography can serve to guide injections into the facet joints, about the nerve roots, and into the iliolumbar ligaments; as well as to identify relevant landmarks before epidural injection. Although diagnostic applications are more limited at present, systematic studies of abnormal ultrasonography findings will allow evaluations of the potential usefulness of ultrasonography for diagnosing spinal disorders. The depth of the spinal structures limits the ability to obtain high-resolution images. However, future technical improvements in ultrasound transducers and machines, together with the growing number of physicians trained in ultrasonography, can be expected to benefit the development of spinal ultrasonography in the near future.  相似文献   
44.
PurposeTo prospectively assess how to address requests for ultrasonographic examinations when setting up an on-call teleradiology service.Materials and methodsAn analytical prospective study was performed from January 2012 to December 2012 inclusively. All requests received for after-hours ultrasonographic examinations during this period were analyzed. Ultrasound requests were classified as being postponable until working hours, replaceable by an alternate cross-sectional imaging modality, or urgent and needing to be performed after hours.ResultsA total of 176 requests for ultrasonographic examinations were analyzed. They predominantly included requests for abdominal and pelvic ultrasonographic examinations (63%). Thirty-nine requests (22.2%) were considered as postponable, 49 (27.8%) as replaceable and 64 (36.4%) as both postponable and replaceable. Twenty-four requests (13.6%) were considered as urgent; they consisted of 10 requests for venous duplex Doppler ultrasonographic examinations of the lower limbs, eight requests for testicular ultrasonographic examinations, five for pelvic ultrasonographic examinations and one for soft-tissue ultrasonographic examination. In these urgent cases, realistic options were either to transfer the patient to another institution or to train emergency department physicians in ultrasonography for local handling.ConclusionAlthough the need for addressing requests for ultrasonographic examinations should be taken into account when setting up an on-call teleradiology service, it should not impede such plans.  相似文献   
45.
PurposeTo investigate the correlation and concordance between the ellipsoid volume calculated by ultrasonography measurements (Vol3DUS) and the reference kidney volume measured by CT (VolTDM) in early autosomal dominant polycystic kidney disease (ADPKD).Materials and methodsProspective study of the correlation and concordance of renal volumes in 24 patients with early ADPKD (48 kidneys analysed separately), with calculation of Vol3DUS using the formula for an ellipsoid in three different manners and VolTDM measurement by manual contouring. Calculations of correlation coefficients (r) and coefficients of intra-class correlation (ICC) with confidence intervals at 95%.ResultsThe US volume was strongly correlated with the CT volume by using the maximum width in a transverse section (r = 0.83) with a mean Vol3DUS = 692 ± 348 ml [180; 2069]. The most reproducible ultrasonography measurement was the height. When the kidney volume exceeded 800 ml, US underestimated the volume. However, the median error was −57.5 ml [−1090; 183] and 85% of the Vol3DUS calculated differed by more than 5% from the reference measurement.ConclusionThe correlation between the US calculated volumes and the CT volumes was strong. However, the median error with ellipsoid US volume was too high to detect a small renal variation in early ADPKD.  相似文献   
46.
评价超声在甲状旁腺疾病诊断中的价值及多种影像学检查技术在甲状旁腺疾病诊断中的对比分析。方法回顾性分析于我院行甲状旁腺手术切除患者94例,共104个病灶。观察病变的声像图特征,对比分析多种影像学检查结果。结果不同甲状旁腺病变的超声声像图特征具有差异性,超声诊断甲状旁腺病变的敏感度为82.69%(86/104),对于直径1cm的病变,超声诊断的敏感度明显高于其他检查单独使用,而对于合并甲状腺结节的病变超声的敏感度低于核素显像及超声联合核素检查(P均0.05)。结论超声可作为甲状旁腺病变诊断的首选检查方法,联合运用各种影像学检查,可更好地进行病变的术前定位及诊断。  相似文献   
47.
目的应用CEUS技术观察兔肝VX2肿瘤坏死过程,探讨VX2肿瘤生长坏死规律及其对实验产生的影响。方法应用超声引导下经皮穿刺种植法成功建立24只兔VX2肝肿瘤模型,并通过CEUS技术分别在肿瘤种植后10、14、21、28天动态观察肝肿瘤演变过程,测量肿瘤体积及坏死体积,计算瘤内坏死率。结果在肿瘤种植后10、14、21、28天兔肝VX2肿瘤体积、坏死灶体积和坏死率比较,差异均有统计学意义(P均0.05);肿瘤种植后10、14、21、28天的CEUS表现能反映出肿瘤的病理学特征。实验依据CEUS和病理特点将肿瘤生长过程细分为5个时期,0~10天为肿瘤实质前期;11~14天为肿瘤实质后期;15~21天为肿瘤坏死初期;22~28天为加速坏死期;28天后为肿瘤囊变期。结论 CEUS可准确判断肝肿瘤实质及坏死范围;VX2肿瘤的生长演变及肿瘤坏死具有规律性,可根据不同实验要求选择适宜的研究时间段。  相似文献   
48.
子宫肌瘤和子宫腺肌瘤均为女性常见的良性疾病,对二者正确的鉴别诊断对治疗方案的建立以及手术方式的选择具有重要意义。本文就各种超声检查技术在子宫肌瘤和子宫腺肌瘤的鉴别诊断中的研究进展进行综述。  相似文献   
49.
目的探讨彩色多普勒超声在子宫动脉栓塞术(UAE)治疗子宫瘢痕妊娠(CSP)疗效监测与评价中的应用价值。方法回顾性分析96例CSP患者UAE治疗前及治疗后的超声表现及相关临床资料,并进行统计学分析。结果 96例CSP患者中,孕囊型58例,团块型38例。孕囊型CSP患者UAE并清宫后孕囊均被清除。团块型CSP患者UAE并清宫后24~48h团块直径较UAE术前及UAE术后24~48h减小(P均0.001)。孕囊型与团块型CSP患者间,UAE术前、UAE术后24~48h及UAE并清宫后24~48h病灶周边血流信号分级差异均无统计学意义(P均0.05)。两种类型CSP患者UAE术后24~48h、UAE并清宫后24~48h病灶周边血流信号分级均较UAE术前明显减低(P均0.001)。孕囊型与团块型CSP患者间,UAE术前及UAE术后24~48h子宫瘢痕厚度差异均无统计学意义(P均0.05)。UAE并清宫后24~48h孕囊型CSP患者子宫瘢痕厚度高于团块型(P0.001)。孕囊型CSP患者UAE并清宫后24~48h子宫瘢痕厚度高于UAE术前及UAE术后24~48h(P均0.001)。团块型CSP患者UAE并清宫后24~48h子宫瘢痕厚度高于UAE术前(P=0.037),与UAE术后24~48h差异无统计学意义(P=0.112)。孕囊型CSP患者术中出血量、住院时间、血清人绒毛膜促性腺激素(β-HCG)降至正常的时间及术后阴道流血时间均少于团块型(P均0.001)。结论通过彩色多普勒超声可有效监测UAE治疗CSP的疗效,UAE对不同类型CSP的疗效有所不同,孕囊型CSP患者疗效优于团块型。  相似文献   
50.
目的探讨经直肠超声引导下前列腺穿刺活检术前列腺癌检出率与血清前列腺特异性抗原(PSA)及血清前列腺特异性抗原密度(PSAD)的关系。方法对134例患者行经直肠超声引导下前列腺5区13针系统穿刺活检。根据PSA水平分为PSA≤4ng/ml组(7例)、4ng/mlPSA15ng/ml组(48例)及PSA≥15ng/ml组(79例)。测量并计算前列腺体积(PV)及PSAD,分析前列腺癌检出率及不同PSA、PSAD水平下对前列腺癌的诊断效能。比较前列腺癌与非前列腺癌患者PSA、PV及PSAD的差异。结果前列腺癌总检出率为50.75%(68/134),前列腺患者共68例(前列腺癌组),非前列腺癌患者共66例(非前列腺啊组)。PSA≤4ng/ml、4ng/mlPSA≤15ng/ml及PSA15ng/ml组前列腺癌检出率分别为14.29%(1/7)、20.83%(10/48)及72.15%(57/79),差异有统计学意义(P0.05)。PSA≥4ng/ml时前列腺癌检出率随着PSA值的增高而上升。134例患者PSAD值为(1.09±1.72)ng/(ml·cm3),以PSAD≥0.19ng/(ml·cm3)为截点诊断前列腺癌的敏感度为95.59%(65/68),特异度为51.52%(34/66),阳性预测值67.01%(65/97),阴性预测值为32.99%(32/97)。4ng/mlPSA≤15ng/ml组中,以PSAD≥0.19ng/(ml.cm3)为截点诊断前列腺癌的敏感度为80.00%(8/10),特异度为71.05%(27/38),阳性预测值为42.11%(8/19),阴性预测值为57.89%(11/19)。前列腺癌组PSA及PSAD值均高于非前列腺癌组(P均0.05),PV小于非前列腺癌组(P0.05)。4ng/mlPSA≤15ng/ml组中,前列腺癌与非前列腺癌患者PSA及PV差异均无统计学意义(P均0.05),前列腺癌患者PSAD高于非前列腺癌患者(P0.05)。结论血清PSA及PSAD均与前列腺穿刺活检前列腺癌检出率有关,PSA15ng/ml应行穿刺活检,PSAD对4ng/mlPSA≤15ng/ml的患者是否应行穿刺活检具有指导意义。  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