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   9620篇
  免费   739篇
  国内免费   226篇
耳鼻咽喉   47篇
儿科学   171篇
妇产科学   154篇
基础医学   1269篇
口腔科学   115篇
临床医学   838篇
内科学   1106篇
皮肤病学   121篇
神经病学   566篇
特种医学   1046篇
外国民族医学   6篇
外科学   1654篇
综合类   1006篇
现状与发展   1篇
预防医学   456篇
眼科学   65篇
药学   898篇
中国医学   155篇
肿瘤学   911篇
  2023年   103篇
  2022年   175篇
  2021年   265篇
  2020年   245篇
  2019年   319篇
  2018年   249篇
  2017年   247篇
  2016年   290篇
  2015年   347篇
  2014年   630篇
  2013年   587篇
  2012年   546篇
  2011年   739篇
  2010年   636篇
  2009年   682篇
  2008年   636篇
  2007年   667篇
  2006年   591篇
  2005年   427篇
  2004年   446篇
  2003年   345篇
  2002年   226篇
  2001年   174篇
  2000年   131篇
  1999年   101篇
  1998年   61篇
  1997年   88篇
  1996年   77篇
  1995年   53篇
  1994年   47篇
  1993年   40篇
  1992年   36篇
  1991年   27篇
  1990年   23篇
  1989年   18篇
  1988年   22篇
  1987年   18篇
  1986年   21篇
  1985年   32篇
  1984年   36篇
  1983年   38篇
  1982年   30篇
  1981年   23篇
  1980年   18篇
  1979年   23篇
  1978年   10篇
  1977年   6篇
  1976年   5篇
  1975年   5篇
  1973年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (Kryptofix® 2.2.2) is used in the routine preparation of [18F]-labeled tracers employed in positron emission tomography (PET) imaging. Confirming the absence of Kryptofix® in radiopharmaceuticals is a quality control criterion required before they can be released for human use. Analysis of Kryptofix® levels using the iodoplatinate spot-test can be complicated by false-positive results due to nitrogen containing tracers and/or false-negative results caused by added stabilizers. To overcome this issue, we have developed a universal TLC method for the rapid and reliable determination of Kryptofix® levels in the wide range of fluorine-18 radiopharmaceuticals we prepare, including complex multi-component formulations.  相似文献   
32.
Objective  The objective of this study was to follow up and evaluate the statewide first-trimester combined screening programme for Down syndrome and trisomy 18 at Genetic Health Services Victoria, Australia.
Design  Retrospective population cohort.
Setting  Maternal Serum Screening Laboratory records.
Sample  All women screened between February 2000 and June 2002 (16 153 pregnancies).
Methods  Screening results were matched to Victorian perinatal and birth defect data via record linkage, with an ascertainment of 96.8% of pregnancy outcomes. Manual follow up with health professionals increased ascertainment to more than 99%.
Main outcome measures  Fetal Down syndrome or trisomy 18, and combined screen results, to calculate test characteristics.
Results  Using a risk threshold of 1 in 300 at time of ultrasound, the sensitivities for standard first-trimester combined screening and augmented 13-week combined screening for Down syndrome were 87.3 and 90.5% and the false-positive rates (FPR) were 4.1 and 3.9%, respectively. The sensitivity for trisomy 18 was 66.7% (10/15, 95% CI 42.8–90.5%) with a 0.4% FPR and 15.2% positive predictive value (1 in 250 risk threshold).
Conclusions  The combined use of record linkage and manual follow-up techniques was effective in ascertaining more than 99% of pregnancy outcomes for calculations of accurate test characteristics of the combined screen. The sensitivity for Down syndrome at Genetic Health is comparable to similar populations. However, the sensitivity for trisomy 18 is lower than that elsewhere, which may reflect the overall low birth prevalence of trisomy 18 and associated small numbers in this particular cohort.  相似文献   
33.
详细分析了参数记录数据在Tracerlab FX-FDG上的合成过程,以及造成合成故障的确切原因,从而得出正确的结论,即:对液体的添加过程是否正常,数据记录可提供准确信息,是解决问题可依赖的分析手段。  相似文献   
34.
目的 对甘利欣辅助治疗皮肌炎、系统性红斑狼疮的临床疗效及安全性进行临床评价。方法 采用非盲法半随机对照法,试验组10例,对照组11例,均据病情需要使用激素,试验组辅以静滴甘利欣250~300mg/d,观察2~3周。结果 皮肌炎、系统性红斑狼疮对照组的总有效率为72.7%,试验组为80%;但两组间差异无统计学意义(P〉0.5)。皮损好转及生化酶学改变亦无统计学意义。不良反应轻微。结论 甘利欣辅助治疗皮肌炎、系统性红斑狼疮的临床疗效尚需进一步研究。  相似文献   
35.
目的 探讨实质器官移植术后血浆中白介素18(IL-18)、白介素10(IL-10)、白介素4(IL-4)水平的检测在人巨细胞病毒(HCMV)感染中的意义。方法 对24例实质器官移植受者,用免疫组化法监测HCMV抗原血症。然后采用ELISA法测定血浆中IL-18、IL-10及IL-4的水平。结果 HCMV抗原阳性组IL-18的水平高于阴性组(P<0.01),IL-10及IL-4的水平低于阴性组(均P<0.05)。结论 血浆IL-18的水平可作为预测移植患者HCMV感染的一个有效指标,IL-10及IL-4的水平则可作为患者HCMV感染后体内免疫抑制程度的监测指标之一。  相似文献   
36.
从中间体(4)出发,经醛(5),与鏻叶立德(3)或2-酮-4-苯丁烷磷酸酯(11)钠缩合成(6),再钠硼氢还原得3′α-醇(7A)及其差向异构体(7B),经硅胶柱色谱分开,分别经二异丁基铝氢还原,与溴化5-三苯鏻戊酸之Wittig试剂缩合,得17-苯-18,19,20-失三碳前列腺素F(9A)及其15-差向异构体(9B),再用重氮甲烷甲酯化,分别得相应的17-苯-18,19,20-失三碳前列腺素F甲酯(10A)及其15-差向异构体(10B)。  相似文献   
37.
Metastases of differentiated thyroid cancer may show different uptake patterns for fluorine-18 fluorodeoxyglucose and [131I]NaI. FDG positron emission tomography (PET), iodine-131 whole-body scintigraphy (131I WBS) and magnetic resonance imaging were performed in 58 unselected patients, and spiral computed tomography (CT) of the lung in 25 patients. Thirty-eight patients presented with papillary carcinomas, 15 patients with follicular carcinomas and five patients with variants of follicular carcinoma. Primary tumour stage (pT) was pT1 in 3, pT2 in 19, pT3 in 11 and pT4 in 25 cases. For the detection of metastases, FDG PET was found to have a sensitivity of 50%, 131I WBS a sensitivity of 61%, and the two methods combined a sensitivity of 86%. When FDG PET was limited to patients with elevated thyroglobulin (Tg) levels and negative 131I WBS, the sensitivity of this algorithm was 82%. Of the 21 patients with lymph node metastases, seven presented with FDG uptake but no iodine uptake. In four of them, a second FDG hot spot appeared in a lymph node metastasis of normal size. Five of the seven patients underwent surgery. None of the eight patients with pulmonary metastases smaller than 1 cm exhibited FDG uptake, while five of them had iodine uptake. All had positive results on spiral CT. In conclusion, FDG PET cannot be substituted for 131I WBS. If the Tg level is elevated and 131I WBS is negative, FDG PET can be used to detect lymph node metastases and complements anatomical imaging. A spiral CT of the lung is useful to exclude pulmonary metastases before planning a dissection of iodine-negative lymph node metastases. Received 2 May and in revised form 8 July 1997  相似文献   
38.
Evidence from the literature is reviewed to suggest that when fingertip dermal ridge patterns in chromosomal deletion syndromes are characteristic of the opposite spectrum of the developmental scale from patterns found in cases trisomic for the same chromosomal region, the association may be a consequence of loci with growth regulatory functions. Evidence is presented that DNA markers at 18q21 should be the first candidate sequences to be used to test this hypothesis in families with fingertip arches segregating in an apparent autosomal dominant fashion.  相似文献   
39.
18F-FDG PET鉴别肾上腺良恶性肿瘤的临床价值   总被引:3,自引:0,他引:3  
目的:评价^18F-氟代脱氧葡萄糖正电子发射计算机断层显像(^18F-FDG PET)在肾上腺病变定性诊断中的应用价值。方法:回顾性分析22例28个肾上腺肿瘤患者的临床资料,均采用^18F-FDG PET显像,以鉴别肾上腺肿瘤为原发性抑或继发性,同期均行CT检查。结果:CT检查28个肿瘤中22个为恶性肿瘤(其中6个经手术或活检证实,16个随访证实),6个通过活检或随访证实为良性病变。CT发现的19个肾上腺肿瘤中。17个为恶性肿瘤,^18F—FDG PET显像均为阳性。^18F—FDG PET对肾上腺肿瘤的定性判断的灵敏度、特异度和准确度分别为100%、66.7%和92.9%。结论:^18F—FDG PET通过肿瘤的葡萄糖代谢程度来判定病变的性质,对肾上腺恶性病变的标准摄取率(SUV)相对较高,在肾上腺肿瘤良恶性鉴别中可以提供重要的依据。  相似文献   
40.
对中国药典附子中乌头硷限量检查的商榷   总被引:8,自引:0,他引:8  
用高效液相色谱法测定生附子。炮制附片中的乌头硷、中乌头硷和次乌头硷含量,以及3种生物硷的水解速度,发现炮制附片中主要含次乌头硷,而药典只限定乌头硷含量,显得不够完善。故在此基础上探讨了药典中增加次乌头硷含量限定内容的可能性。  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