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   179622篇
  免费   12959篇
  国内免费   4219篇
耳鼻咽喉   1357篇
儿科学   2537篇
妇产科学   3078篇
基础医学   23643篇
口腔科学   3362篇
临床医学   12243篇
内科学   23026篇
皮肤病学   2180篇
神经病学   11951篇
特种医学   6445篇
外国民族医学   1篇
外科学   14526篇
综合类   24071篇
现状与发展   21篇
一般理论   8篇
预防医学   14911篇
眼科学   2279篇
药学   25326篇
  53篇
中国医学   12565篇
肿瘤学   13217篇
  2024年   334篇
  2023年   2193篇
  2022年   4662篇
  2021年   7449篇
  2020年   6017篇
  2019年   6016篇
  2018年   6087篇
  2017年   6721篇
  2016年   6743篇
  2015年   6292篇
  2014年   7029篇
  2013年   10965篇
  2012年   8861篇
  2011年   10772篇
  2010年   6708篇
  2009年   6838篇
  2008年   8335篇
  2007年   9335篇
  2006年   8867篇
  2005年   8237篇
  2004年   7053篇
  2003年   6337篇
  2002年   5003篇
  2001年   4495篇
  2000年   3769篇
  1999年   3210篇
  1998年   2496篇
  1997年   2608篇
  1996年   2396篇
  1995年   2076篇
  1994年   2013篇
  1993年   1697篇
  1992年   1566篇
  1991年   1464篇
  1990年   1266篇
  1989年   1042篇
  1988年   1006篇
  1987年   905篇
  1986年   833篇
  1985年   1212篇
  1984年   969篇
  1983年   736篇
  1982年   758篇
  1981年   622篇
  1980年   607篇
  1979年   481篇
  1978年   298篇
  1977年   259篇
  1976年   245篇
  1975年   186篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
体外测定青蒿琥酯钠(SA)对大鼠红细胞膜Na~( )-K~( )-交换ATP酶活性的影响.方法:在反应系统中分别加入不同浓度的SA(0,0.5,1,5和10 μmol·L~(-1)),通过测定反应系统中释放的无机磷含量,计算酶活性.结果:随着SA浓度(O,0.5,1,5和10 μmol·L~(-1))的增高,对Na~( )-K~( )-交换ATP酶活性的抑制作用也随之增强,抑制率分别为15%,29%,46%和75%.将底物ATP浓度增加为125,250,375和500 μmol·L~(-1),进行了酶的动力学测定.用直线回归分析作Eadie-Hofstee动力学曲线,结果表明,SA对该酶的抑制作用为竞争性抑制.结论:提示SA可影响宿主红细胞膜的离子转运及膜的功能.  相似文献   
992.
A patient with neutropenia and life-threatening infections secondary to T-γ lymphoproliferative disease, who did not respond to treatment with recombinant human G-CSF (filgrastim), was treated with filgrastim plus cyclosporine A (CyA). The patient achieved a good response in the absolute neutrophil count and subsequently required a dose reduction in the filgrastim. The patient was eventually discontinued from the CyA but continues on filgrastim alone. While on therapy, the large granular lymphocytes disappeared from the circulation and the beta-TCR rearrangement, which was present prior to beginning therapy, became undetectable. The patient had no significant toxicity to the CyA or the filgrastim and he has not experienced any serious infections or required hospitalization. Filgrastim has proven to be relatively nontoxic and of some benefit to patients with this disease and should probably be utilized first when treatment is necessary. However, if improvement is not observed, these findings suggest that a trial of the combination of CyA plus filgrastim may be beneficial.  相似文献   
993.
33例肝占位性病变MRI误诊的分析   总被引:1,自引:0,他引:1  
我院1988年以来4000余例腹部MRI中,发现肝占位性病变误诊33例。所用机型为美国Disonics公司0.5T超导MRI,自旋回波序列(SE序列)、常规T1加权(T1WI)、质子加权(PDWI)、T2加权(T2WI),覆盖全肝。其中,PHC误诊为MHC5例、MHC误诊为PHC6例、PHC误为HHE5例、MHC误诊为HHE2例、HHE误诊为PHC6例、肝硬化结节误诊为PHC2例、炎性假瘤误诊为PHC3例、肝结核误诊为PHC1例、HCY误诊为HHE3例。本文从病变的影像学特征和扫描技术方面详细探讨了误诊的原因和鉴别诊断要点。  相似文献   
994.
995.
Purpose. To assess the accuracy of different MR sequences for the detection of articular cartilage abnormalities in rheumatoid arthritis. Design and patients. Ten metacarpophalangeal joints and 10 metatarsophalangeal joints (specimens from arthritis patients undergoing ablative joint surgery) were examined with a fat-suppressed (FS) 3D FLASH, a FS 3D FISP, a FS 2D fast spin-echo T2-weighted, and a 2D FS spin-echo T1-weighted sequence. Each cartilage lesion and each cortical lesion was graded from 0 to 4 (modified Outerbridge staging system). Subsequently, the results of each sequence were compared with the macroscopic findings and statistically tested against each other. Results. The study shows that 3D gradient-echo sequences with fat suppression were best for imaging and grading of cartilage lesions in arthritis of the small joints of the hands and feet. Using 3D techniques, all grade 2, grade 3, and grade 4 lesions of cartilage or cortical bone were detected. Conclusion. FS 3D gradient-echo techniques were best for the detection and grading of hyaline cartilage and subchondral bone lesions in rheumatoid arthritis. MRI has a great potential as an objective method of evaluating cartilage damage and bone erosions in rheumatoid arthritis.  相似文献   
996.
Mechanical waves in magnetic resonance imaging, which have been suggested for possible clinical applications, were analyzed with regard to imaging of the viscoelastic properties of large objects. The method is based on the Larmor frequency modulation caused by the application of mechanical waves. Possible clinical applications include all diseases that result in a change in the mechanical properties of biologic tissues (eg, atherosclerosis).  相似文献   
997.
For an adequate assessment of both the ophthalmological and the neurological consequences of carotid obstruction measurement of the blood pressure in the carotid flow area is essential.To this end there are two objective, registrating methods available at the moment: OPG-Gee and OODG-Ulrich. A comparative study was made into the basic principles, calibration curves and application methods of these systems. By both methods the systolic retinal - and ciliary - as well as the diastolic ocular blood pressure can be measured. OODG is more exact for the differentiation and measurement of the two systolic blood pressures. OPG-Gee, however, offers the unique additional possibility of a judgement on the systolic blood pressure in the carotid siphon without, however, taking into acount a (difference in) pre-existing intraocular pressure. Our own investigation shows that in order to obtain a correct assessment of the carotico-brachial relation both blood pressures should be measured simultaneously. The results of the graphic analysis of the curves are compared to those by Ulrich. For the diagnosis of carotid obstructions this analysis of the shape had no advantages over the determination of the pressure values.Finally, a survey is given of possible applications of OPG and OODG in various other syndromes.  相似文献   
998.
Ramipril blocks the conversion of angiotensin I to II. The literature indicates that diabetes is often associated with mild impairment of learning and memory. The study reports the effects of ramipril on memory retention in diabetic and non-diabetic mice. Mice were made diabetic by an injection of streptozocin. After overt signs of diabetes were present, diabetic or vehicle-treated mice were partially trained on a footshock active avoidance task. Immediately after training, ramipril (0.5–1.5 mg/kg s.c.) was administered and retention was tested by continuing training one week later until mice avoided footshock on five out of six trails. The results indicate that ramipril enhanced retention of both diabetic and control mice but it required about 5 times as much ramipril in diabetic as control mice to achieve the same effect on retention. Increased sensitivity to angiotensin II may play a role in cognitive impairment in diabetes.  相似文献   
999.
头低位模拟失重状态对前庭功能的影响   总被引:4,自引:1,他引:3  
为研究头低位模拟失重对运动病症状、垂直视动眼震(VOKN)及体液重新分配的影响,在头低位-10°的模拟失重状态下,采用大视野的垂直视动刺激,观察18名正常人的运动病症状、VOKN、激素(AVP、VIP、CORT、ALDO)的反应特点。结果表明,头低位-10°状态下的大视野垂直视动刺激可以诱发出明显的运动病症状,头低位-10°的垂直视动刺激比坐位更容易诱发运动病。坐位状态VOKN慢相速度有明显的方向性不对称,敏感组VOKN方向性不对称有显著差异(P<0.05)。头低位-10°时VOKN的不对称现象不明显,向下方向运动的VOKN慢相速度显著增加。分析指出,头低位-10°状态下垂直视动刺激比坐位和秋千刺激的贡献率大。尿中CORT(皮质醇)在秋千和头低位的垂直视动刺激前后有显著性增加。提示:大视野的垂直视动刺激与头低位-10°两种刺激的结合可能成为预测空间运动病的方法之一.  相似文献   
1000.
用毛细管区带电泳法同时测定复方马来酸依那普利片中两组分含量。以咖啡因为内标,20mmol/L硼砂—20mmol/L磷酸二氢钠(49∶51,pH86)为运行缓冲液,在7min内完成分离。马来酸依那普利和氢氯噻嗪的线性范围分别为80~640μg/mL(r=09999)和50~400μg/mL(r=09993)。平均回收率分别为1010%和1011%,RSD分别为10%和17%,n=5。  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