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   6462篇
  免费   568篇
  国内免费   46篇
耳鼻咽喉   150篇
儿科学   197篇
妇产科学   165篇
基础医学   786篇
口腔科学   119篇
临床医学   806篇
内科学   1084篇
皮肤病学   86篇
神经病学   379篇
特种医学   575篇
外科学   927篇
综合类   315篇
一般理论   2篇
预防医学   570篇
眼科学   130篇
药学   452篇
  2篇
中国医学   35篇
肿瘤学   296篇
  2023年   54篇
  2022年   66篇
  2021年   105篇
  2020年   99篇
  2019年   95篇
  2018年   131篇
  2017年   101篇
  2016年   106篇
  2015年   121篇
  2014年   161篇
  2013年   252篇
  2012年   327篇
  2011年   340篇
  2010年   210篇
  2009年   227篇
  2008年   273篇
  2007年   258篇
  2006年   273篇
  2005年   267篇
  2004年   250篇
  2003年   220篇
  2002年   229篇
  2001年   134篇
  2000年   142篇
  1999年   117篇
  1998年   125篇
  1997年   114篇
  1996年   120篇
  1995年   118篇
  1994年   81篇
  1993年   92篇
  1992年   128篇
  1991年   105篇
  1990年   91篇
  1989年   108篇
  1988年   103篇
  1987年   108篇
  1986年   86篇
  1985年   97篇
  1984年   72篇
  1983年   71篇
  1982年   38篇
  1980年   43篇
  1978年   48篇
  1977年   41篇
  1976年   42篇
  1974年   40篇
  1973年   37篇
  1955年   42篇
  1954年   35篇
排序方式: 共有7076条查询结果,搜索用时 15 毫秒
91.
In multiple spin-echo image sequences of blood flow, the "even-echo" phenomenon produces an absolute increase in signal magnitude from first- to second-echo images of normal vessels harboring slow flow. Distinguishing this from the apparent relatively high signal intensity seen on second-echo images in pathologic foci of stationary tissue is important to the diagnostician. Selected case material containing two tissue types was reviewed retrospectively: tissues known to harbor slow flow, such as normal veins and venous sinuses and vascular malformations, and tissues that have long transverse (T2) relaxation times and appear as intense structures on second-echo images, such as neoplasms, infarcts, and regions of demyelination. Calculations of T2 parameters were made by computer for defined regions of interest. T2 images were also generated. Visual inspection of the acquired images did not reliably distinguish increased intensity due to even-echo rephasing from the relative changes between adjacent tissues seen on second-echo images. More definitive differentiation of the even-echo phenomenon was provided by calculated values of T2 and computer-synthesized T2 images representing acquired intensity data of two-echo sequences. The synthesized images were especially useful when stationary tissue with lengthened T2 values was adjacent to or in proximity to vessels or vascular lesions. A five spin-echo image sequence was valuable for separating slow flow from stationary tissue by a technique of synthesizing T2-difference images using three consecutive echoes.  相似文献   
92.
Sixteen patients with suspected cerebral metastases were studied with magnetic resonance (MR) imaging before and after the intravenous administration of 0.1 mmol/kg of gadolinium diethylenetriaminepenta-acetic acid. The images were interpreted blindly by two neuroradiologists; all clinical, radiologic (computed tomographic and MR imaging), and pathologic data were reviewed to arrive at a final "best diagnosis," which was then compared with the prior blinded interpretations. Of seven patients found to have multiple metastases, six (86%) had at least one tumor nodule depicted by postinfusion MR imaging that was missed by one or both observers on review of preinfusion images alone. Lesions missed on preinfusion studies were usually small nodules hidden by or not detected next to regions of high-signal edema thought to be related to the adjacent tumor nodule. The authors believe that contrast enhancement improves detection of metastatic foci with MR imaging and that the findings indicate broader implications for the detection of multiple lesions from other causes.  相似文献   
93.
目的:通过对骨髓单个核细胞在体外与不同细胞因子培养,了解不同细胞因子对骨髓淋巴细胞的激活能力和对骨髓干祖细胞的损伤情况。方法:将IL-1、IL-2、γ-IFN、CD3单抗进行不同组合后,在体外与骨髓单个核细胞分成对照组、IL-2组、CD3-AK、CIK组进行培养。培养过程中观察细胞形态和数量的变化,并在培养后检测免疫活性细胞的细胞毒性和造血干细胞的保存情况。结果:培养过程中对照组细胞数量减少;IL-2组细胞数量变化不明显;CD3-AK组、CIK组细胞数量显著增多,并出现较多的集聚成簇的淋巴样细胞,培养后其细胞毒性明显强于对照组及IL-2组,但细胞数量增加和细胞毒性无明性差异,培养后各组造血干细胞保存情况约16%~87%。结论:IL-2、CD3单抗在体外与骨髓单个核细胞培养后,即能激活免疫细胞增殖,又能保留足够的造血干细胞。  相似文献   
94.
95.
Quality of Life Research - Adolescents and young adults (AYA) with Inflammatory Bowel Disease (IBD) report higher depressive symptoms and anxiety compared to healthy controls, with disease severity...  相似文献   
96.
We have compared the specific activities of Cu/Zn superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in a vinblastine sensitive human T-lymphoblastic cell line (CCRF-CEM) and its multiple drug resistant (MDR) counterpart cell line (CEM/VLB100), which over-expresses P-glycoprotein (PGP). We have found that the specific activity Cu/Zn SOD was consistently 38% increased in CEM/VLB100 cells compared with CCRF-CEM cells. In contrast, the activities of CAT and GSH-Px were similar in the two cell lines. These results suggest that MDR in CEM/VLB100 is a complicated phenotype which not only involves a PGP mechanism, but also a SOD protection mechanism against drug-mediated O2.- cytotoxicity.  相似文献   
97.
目的 探讨人胰弹力蛋白酶Ⅰ (Humanpancreaticelastase 1 ,HPE1 )放射免疫测定 (Radioimmunoassay ,RIA)和核糖核酸酶(Ribonuclease ,RNase)活性检测的临床价值。方法 参照Satake等建立的改良HPE1RIA和Thomas等的改良酸溶性产物法检测 82例正常成年人和 2 2 2例各类患者血清并分析结果。结果  82例健康成人HPE1值为 2 3.8( 3.4ng L) ,RNase活性为 5 7.0 3( 1 2 .1 6 μ ml) ;急性胰腺炎和胰腺癌HPE1 值明显高于其他疾病 (P <0 .0 1 )。联合检测HPE1 、RNase活性可提高胰腺癌的检出率 ( 92 .47% )。结论 HPE1 RIA对急性胰腺炎有诊断价值 ,联合检测HPE1 、RNase活性检测对胰腺癌诊断有一定的临床价值  相似文献   
98.
口服莫沙必利治疗功能性消化不良的随机对照试验   总被引:5,自引:0,他引:5  
目的 观察新型促胃肠动力药莫沙必利 (胃 5 HT4受体促进剂 )对功能性消化不良 (FD)的随机对照试验。方法 FD患者 42例 ,随机分为试验组 (2 1例 ,服枸橼酸莫沙必利片 )和对照组 (2 1例 ,服吗叮啉片 )。采用GCP标准 ,双盲法观察 ,在实验开始前、服药第 1 4、2 8天记录症状变化及副作用发生情况。随机抽取部分患者于实验开始前和结束时做99MTc胃排空试验。结果 莫沙必利对FD症状的疗效与吗叮啉组相当 (P >0 .0 5 )。99MTc胃排空测定发现莫沙必利组治疗后的半排时间 (45 .0 5± 1 2 .2 1 )min缩短 ,1 2 0min残留率 (2 9.73%± 8.5 1 % )减少 (P <0 .0 5 ) ,两组病例未发现毒副反应。结论 莫沙必利对于FD疗效良好 ,对胃排空延迟有良好疗效 ,安全度高。  相似文献   
99.
本文从医学人才培养的高度,论述高校与附属医院建立非隶属关系的附属医院的过程、体会和思考,指出目前存在的问题和解决途径.对进一步深化临床教育教学改革具有重要意义.  相似文献   
100.
The individual educational and intervention emphasis of clinical preventive medicine programs is successful in reducing an employee's risk for disease and injury. Although some studies note that decreased risk is found predominantly in those with low initial risk, a critical mass of healthful lifestyles may spread to non-participants in the organization, the halo effect. Thus, the more employees there are modeling a health lifestyle, the greater likelihood others will follow. Preventive medicine programs offer intangible advantages to the employer. Such programs demonstrate an attitude of caring for the employee which has an influence on the public. Happier employees tend to increase their level of socialization within a company. The ultimate effect is decreased employee risk, improved productivity, reduced absenteeism, and improved health at reduced cost.  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