全文获取类型
收费全文 | 91212篇 |
免费 | 8117篇 |
国内免费 | 2017篇 |
专业分类
耳鼻咽喉 | 751篇 |
儿科学 | 1313篇 |
妇产科学 | 729篇 |
基础医学 | 7468篇 |
口腔科学 | 1504篇 |
临床医学 | 16866篇 |
内科学 | 10025篇 |
皮肤病学 | 543篇 |
神经病学 | 10201篇 |
特种医学 | 23457篇 |
外国民族医学 | 18篇 |
外科学 | 8879篇 |
综合类 | 8934篇 |
现状与发展 | 1篇 |
预防医学 | 1828篇 |
眼科学 | 1424篇 |
药学 | 2927篇 |
62篇 | |
中国医学 | 528篇 |
肿瘤学 | 3888篇 |
出版年
2024年 | 326篇 |
2023年 | 1533篇 |
2022年 | 2975篇 |
2021年 | 3861篇 |
2020年 | 3620篇 |
2019年 | 3381篇 |
2018年 | 3354篇 |
2017年 | 3595篇 |
2016年 | 4549篇 |
2015年 | 4038篇 |
2014年 | 6466篇 |
2013年 | 5650篇 |
2012年 | 5332篇 |
2011年 | 5884篇 |
2010年 | 4843篇 |
2009年 | 5093篇 |
2008年 | 5123篇 |
2007年 | 4801篇 |
2006年 | 4267篇 |
2005年 | 3741篇 |
2004年 | 3118篇 |
2003年 | 2456篇 |
2002年 | 1913篇 |
2001年 | 1788篇 |
2000年 | 1489篇 |
1999年 | 1152篇 |
1998年 | 1115篇 |
1997年 | 1008篇 |
1996年 | 867篇 |
1995年 | 760篇 |
1994年 | 616篇 |
1993年 | 502篇 |
1992年 | 405篇 |
1991年 | 317篇 |
1990年 | 247篇 |
1989年 | 175篇 |
1988年 | 158篇 |
1987年 | 152篇 |
1986年 | 101篇 |
1985年 | 87篇 |
1984年 | 81篇 |
1983年 | 50篇 |
1982年 | 46篇 |
1981年 | 44篇 |
1980年 | 45篇 |
1979年 | 35篇 |
1978年 | 27篇 |
1977年 | 27篇 |
1976年 | 27篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
乳腺影像学报告及数据系统:超声良恶性病变鉴别诊断初探 总被引:1,自引:0,他引:1
1992年美国放射学会制定了乳腺影像学报告及数据系统(breast imaging reporting and data system,BI-RADS),2003年第四版修订时包括了超声诊断(BI-RADS-US)。本文旨在初步探讨BI-RADS-US对于乳腺良恶性病变鉴别诊断的能力。我们收集了2006年1月至2007年3月期间、获得病理诊断的乳腺占位性病变共69例72灶。均为女性,年龄14-83岁,平均41.6岁。首先根据一般的非BI-RADS标准,做出良恶性鉴别。然后用BI-RADS-US标准进行鉴别和分级(0-6级),其中2级和3级为良性和良性可能性大,4级为性质待定,5级为恶性可能性大。计算并比较上述两种方法的准确性、敏感性、特异性。结果在72病灶中,根据非BI-RADS标准,诊断为良性者40灶,符合病理诊断者38灶(95.0%),诊断为恶性者23灶,符合病理者18灶(78.3%);诊断为性质待定者9灶。根据BI-RADS-US标准和分级,2级和3级共有37灶,与病理结果符合者为36灶(97.2%);5级有31灶,与病理符合者为22灶(71.0%);4级有4灶。非BI-RADS和BI-RADS-US的准确性各为83.3%和81.9%(P=1.000),敏感性各为91.7%和95.8%(P=1.000),特异性各为79.2%和75.0%(P=0.754)。总之,第一版BI-RADS-US在乳腺良恶性病变鉴别诊断方面的初步应用表现出较高的敏感性,而与非BI-RADS方法比较则尚无明显差别。 相似文献
32.
33.
F. Cotton O. Pellet F.-N. Gilly A. Granier L. Sournac O. Glehen 《European journal of surgical oncology》2006,32(10):1212-1216
AIM: Peritonectomy procedures with intraperitoneal chemohyperthermia are an effective but costly treatment for peritoneal carcinomatosis (PC). Consequently a proper selection of patients is necessary. We evaluated the benefit of MRI prior to surgery, in the detection of two of the main surgery contraindications: bulky mesenteric tumors and bladder implants. METHODS: Three experts retrospectively reviewed abdominal and pelvic MRI from 19 cases of surgically proved PC (ovary: 7; colorectal: 7; gastric: 2; pseudomyxoma peritonei: 2; appendix: 1). RESULTS: Mesenteric tumors were always identified as hypersignal masses on axial and coronal fat suppression gadolinium-enhanced T1 images (n=3). Three out of five bladder implants were detected. The two cases of bladder implants that were not detected on MRI were missed because the bladder was not filled. The best sequence for the detection of bladder involvement was axial T2-weighted images with bladder filling. CONCLUSIONS: Evaluating the preoperative resectability of PC is crucial for patient management. MRI seems to reliably detect bulky mesenteric tumors and bladder implants on condition the bladder is filled and appropriate sequences are used. 相似文献
34.
目的探索体外构建组织工程血管及细胞种植的方法。方法(1)制备管状支架模具,采用模具成形,冷冻干燥等技术,应用胶原和透明质酸复合体外预构管状支架;(2)分动态种植和静态培养两组进行细胞分层种植,每组12个,应用水溶性磺酸四唑(WST-1)测定,扫描电镜观察,5-溴2-脱氧嘧啶核苷(BrdU)细胞标记鉴定比较两种方法的细胞生长情况。结果(1)成功制备了管状支架,在培养液中约3周可保持管腔形态不变形,不塌陷;2.WST-1测定值在培养6、14、20 d分别为:动态组0.842±0.110、1.124±0.102、1.132±0.112,静态组0.386±0.121、0.489±0.245、0.499±0.265,两组比较差异有统计学意义,电镜和BrdU标记表明动态组细胞排列整齐有序。结论应用模具成形,冷冻干燥技术预构管状支架的方法切实可行,动态培养有助于细胞种植,本研究为组织工程血管的构建方法提供了思路。 相似文献
35.
Sonographic evaluation of gallbladder kinetics: in vitro and in vivo comparison of different methods to assess gallbladder emptying. 总被引:3,自引:0,他引:3
Bernd Wedmann Gabriele Schmidt Martin Wegener Christoph Coenen Dieter Ricken Cornelia Drge 《Journal of clinical ultrasound : JCU》1991,19(6):341-349
In an in vitro study, 10 gallbladders of adult pigs and 6 gallbladders of lambs, all removed immediately after slaughtering, were stimulated in a water bath by electric means to induce active contraction. Gallbladder emptying was followed by ultrasonography employing five measurement procedures: (1) gallbladder width, (2) longitudinal planimetry, (3) transverse planimetry, (4) ellipsoid method, and (5) sum of cylinders method. In an in vivo investigation, gallbladder emptying of 30 volunteers (12 healthy subjects, 18 diabetics) was evaluated in the same way after ingestion of a fatty meal. Gallbladder width was found to be unsuitable to estimate the decrease in gallbladder volume due to a nonlinear relation of the parameters. Longitudinal planimetry tended to be less valid than transverse planimetry in assessing gallbladder volume reduction. The most valid estimation of gallbladder volume decreases was obtained by the two three-dimensional procedures. However, in neither in vitro nor in vivo could a significant difference between the sum of cylinders method and the ellipsoid method in determining relative volume reduction be established. We conclude that a three-dimensional measurement procedure should be used for valid assessments of gallbladder motility. However, according to our data there is no advantage in using the time-consuming sum of cylinders method compared to the simple ellipsoid method. 相似文献
36.
目的:探讨眼眶病变的MRI诊断与鉴别诊断价值。方法:对29例经临床病理确诊的眼眶病变的病例进行回顾性分析,重点观察该类疾病的MRI表现。结果:眼眶病变29例,包括肿瘤10例。炎症10例,血管性病变3例,眼肌病变6例。其在MRI表现各具有影像学特征,眼眶肿瘤多表现为位于眼眶内、外的局限性软组织肿块,MR T1WI呈等或稍低信号,T2WI呈高或等信号多见;炎性假瘤则表现为眶内局限性软组织肿块或弥漫性异常信号.MR T1WI呈低信号,T2WI呈高信号,常伴有眼肌肥大或眼环增厚,泪腺肿大等。结论:MRI检查能显示眼眶病变的影像学特征,对其诊断及鉴别诊断具有重要价值。 相似文献
37.
38.
Further evidence of dopamine transporter dysregulation in ADHD: a controlled PET imaging study using altropane. 总被引:4,自引:0,他引:4
Thomas J Spencer Joseph Biederman Bertha K Madras Darin D Dougherty Ali A Bonab Elijahu Livni Peter C Meltzer Jessica Martin Scott Rauch Alan J Fischman 《Neuropsychopharmacology》2007,62(9):1059-1061
BACKGROUND: The dopamine transporter (DAT) is known to be a key regulator of dopamine, and recent studies of genetics, treatment, and imaging have highlighted the role of DAT in attention-deficit/hyperactivity disorder (ADHD). The findings of in vivo neuroimaging of DAT in ADHD have been somewhat discrepant, however. METHOD: Dopamine transporter binding was measured using a highly selective ligand (C-11 altropane) and positron emission tomography (PET). The sample consisted of 47 well-characterized, treatment-na?ve, nonsmoking, non-comorbid adults with and without ADHD. Additionally, control subjects had few symptoms of ADHD. RESULTS: Results showed significantly increased DAT binding in the right caudate in adults with ADHD compared with matched control subjects without this disorder. CONCLUSIONS: These results confirm abnormal DAT binding in the striatum of adults with ADHD and provide further support that dysregulation of DAT may be an important component of the pathophysiology of ADHD. 相似文献
39.
BACKGROUND: Studies have shown that alcoholics have smaller brain volumes than non-alcoholic cohorts, but an effect of family history (FH) of heavy drinking on brain volume has not been demonstrated. We examined the relationship between an FH of heavy drinking and both brain shrinkage as measured by the ratio of brain volumes to intracranial volume (ICV) as well as maximal brain growth as measured by ICV in early-onset and late-onset alcoholics. METHODS: With T1-weighted resonance imaging, we measured ICV, brain volume, and white and gray matter volume in adult treatment-seeking late-onset and early-onset alcoholics with either a positive or a negative FH of heavy alcohol use, and in healthy control subjects. We also calculated brain shrinkage using a ratio of soft tissue volumes to ICV. RESULTS: The FH positive alcoholic patients had significantly smaller ICVs than FH negative patients, suggesting smaller premorbid brain growth. Brain shrinkage did not correlate with FH. Late-onset alcoholics showed a greater difference in ICV between FH positive and FH negative patients than early-onset alcoholics. Late-onset FH positive patients also had significantly lower IQ scores than late-onset FH negative patients, and IQ scores were correlated with ICV. CONCLUSIONS: These data provide evidence that parental alcohol use might increase risk for alcoholism in offspring in part by a genetic and/or environmental effect that might be related to reduced brain growth. 相似文献
40.
Geir Håland Kai-Håkon Carlsen Chandra Sekhar Devulapalli Morten Pettersen Petter Mowinckel Karin C. Lødrup Carlsen 《Pediatric allergy and immunology》2007,18(6):528-534
The aim of the study was to assess if lung function at birth predicts lung function at 2 yr and secondly, if lung function development was influenced by the common phenotypes of recurrent bronchial obstruction (rBO) or atopic eczema (AE) by 2 yr. Lung function was assessed at birth (n = 802) and at 2 yr within the prospective birth cohort study 'the Environment and Childhood Asthma Study' in Oslo. The 135 children with lung function measured at birth by tidal flow volume (TFV) loops and passive respiratory mechanics, who were included in a nested case-control study were reinvestigated at 2 yr with clinical examination, TFV loops (n = 90) (mean age 26.6 (3.7 s.d.) months), skin prick test and parental interview. Children were categorized into quartiles (lower, middle two, upper) according to time to peak tidal expiratory flow/total expiratory time (t(PTEF)/t(E)) at birth as well as clinical phenotype based on the presence of rBO and/or AE (ever) by 2 yr. The observed reduction in mean t(PTEF)/t(E) from birth to 2 yr within the quartiles, were not significantly different after controlling for 'regression to the mean'. t(PTEF)/t(E) at birth correlated significantly with t(PTEF)/t(E) at 2 yr, (r = 0.475, p < 0.001). Children with both rBO and AE by 2 yr had significantly lower t(PTEF)/t(E) at 2 yr (p = 0.002) and at birth (p = 0.027), compared with children with no rBO or AE. Clinical phenotype at 2 yr did not influence the change in t(PTEF)/t(E) from birth to 2 yr. This study demonstrates a clear tracking of lung function from birth, not influenced by rBO or AE by 2 yr. 相似文献