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   21852篇
  免费   1933篇
  国内免费   1488篇
耳鼻咽喉   126篇
儿科学   218篇
妇产科学   201篇
基础医学   2672篇
口腔科学   380篇
临床医学   3134篇
内科学   3131篇
皮肤病学   221篇
神经病学   1139篇
特种医学   740篇
外国民族医学   13篇
外科学   2128篇
综合类   4060篇
现状与发展   5篇
预防医学   1118篇
眼科学   574篇
药学   2340篇
  22篇
中国医学   1225篇
肿瘤学   1826篇
  2024年   78篇
  2023年   413篇
  2022年   983篇
  2021年   1177篇
  2020年   912篇
  2019年   723篇
  2018年   815篇
  2017年   702篇
  2016年   703篇
  2015年   1072篇
  2014年   1300篇
  2013年   1097篇
  2012年   1631篇
  2011年   1789篇
  2010年   1049篇
  2009年   823篇
  2008年   1086篇
  2007年   1062篇
  2006年   1101篇
  2005年   1074篇
  2004年   703篇
  2003年   646篇
  2002年   555篇
  2001年   496篇
  2000年   516篇
  1999年   526篇
  1998年   312篇
  1997年   314篇
  1996年   214篇
  1995年   212篇
  1994年   222篇
  1993年   120篇
  1992年   129篇
  1991年   128篇
  1990年   124篇
  1989年   89篇
  1988年   89篇
  1987年   77篇
  1986年   62篇
  1985年   57篇
  1984年   21篇
  1983年   12篇
  1982年   15篇
  1981年   14篇
  1980年   3篇
  1979年   15篇
  1978年   2篇
  1977年   2篇
  1976年   3篇
  1974年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
中老年人前列腺体积增长的城乡差异   总被引:27,自引:1,他引:26  
为了解国人中年以后前列腺的生长情况及其可能的影响因素,对北京、河北、湖北等地四个社区的城乡居民前列腺体积进行了经腹B超测量。结果表明城区居民的前列腺体积明显大于相应年龄段的农村居民,城区居民的前列腺增长速率比农村居民高二倍。生活环境和饮食习惯的不同可能为其原因之一。  相似文献   
2.
Twenty five cases, including 26 eyes with retinal vein occlusion (RVO) were examined by means of the electro-oculogram. The results showed that 23 of the 26 eyes suffering from RVO exhibited abnormalities of the electro-oculogram (EOG). The potential difference and Arden ratio in the RVO eyes were lower than those in the normal eyes (P<0.01). The more the visual acuity of ill eyes was decreased, the higher the abnormal rate of EOG in ill eyes was. 14 eyes had the visual acuity less than 0.1, whose EOGs were abnortmal. Six eyes had the visual acuity from 0. 2 to 0. 4, in which the EOGs of 5 eyes were abnormal. Six eyes had the visual acuity more than 0. 5, a-mong which the EOGs of 4 eyes were abnormal. Based on the above observations, it may be considered that the circulatory disturbance resulting from RVO damages not only the internal layer but also the external layer of the retina. We suggest that EOG is a useful method for distingquishing lesions caused by RVO and may reflect the functional condition  相似文献   
3.
本文采用去垢剂透析法成功制备出携载SOD的脂质体(L-SOD),其直径为102nm,对SOD的包裹率为21%,90%以上酶活性存在于脂质体内部。将L-SOD注射到大鼠静脉血中,其半衰期超过4h,明显长于天然SOD(8min)。表明L-SOD优于天然SOD,具有临床应用前景。  相似文献   
4.
5.
A genome-wide screen was conducted using a large white sample to identify QTLs for FNCS geometry. We found significant linkage of FNCS parameters to 20q12 and Xq25, plus significant epistatic interactions and sex-specific QTLs influencing FNCS geometry variation. INTRODUCTION: Bone geometry, a highly heritable trait, is a critical component of bone strength that significantly determines osteoporotic fracture risk. Specifically, femoral neck cross-sectional (FNCS) geometry is significantly associated with hip fracture risk as well as genetic factors. However, genetic research in this respect is still in its infancy. MATERIALS AND METHODS: To identify the underlying genomic regions influencing FNCS variables, we performed a remarkably large-scale whole genome linkage scan involving 3998 individuals from 434 pedigrees for four FNCS geometry parameters, namely buckling ratio (BR), cross-sectional area (CSA), cortical thickness (CT), and section modulus (Z). The major statistical approach adopted is the variance component method implemented in SOLAR. RESULTS: Significant linkage evidence (threshold LOD = 3.72 after correction for tests of multiple phenotypes) was found in the regions of 20q12 and Xq25 for CT (LOD = 4.28 and 3.90, respectively). We also identified eight suggestive linkage signals (threshold LOD = 2.31 after correction for multiple tests) for the respective geometry traits. The above findings were supported by principal component linkage analysis. Of them, 20q12 was of particular interest because it was linked to multiple FNCS geometry traits and significantly interacted with five other genomic loci to influence CSA variation. The effects of 20q12 on FNCS geometry were present in both male and female subgroups. Subgroup analysis also revealed the presence of sex-specific quantitative trait loci (QTLs) for FNCS traits in the regions such as 2p14, 3q26, 7q21 and 15q21. CONCLUSIONS: Our findings laid a foundation for further replication and fine-mapping studies as well as for positional and functional candidate gene studies, aiming at eventually finding the causal genetic variants and hidden mechanisms concerning FNCS geometry variation and the associated hip fractures.  相似文献   
6.
高血压病肠系膜动脉平滑肌细胞端粒酶活性表达的研究   总被引:1,自引:0,他引:1  
目的 :探讨高血压病动脉平滑肌组织端粒酶活性与高血压的发病关系。方法 :采用PCR -ELISA法检测 30例高血压病患者和 2 0例血压正常者肠系膜动脉平滑肌细胞 (SMC)端粒酶活性。结果 :高血压患者端粒酶阳性表达 2 8例 (93.3% )。血压正常者端粒酶阳性表达 3例 (15 % )。差异非常显著 (P <0 .0 5 )。结论 :高血压病动脉平滑肌细胞端粒酶活性的表达升高 ,可能与高血压发病有关。  相似文献   
7.
Summary It is difficult for conventional transthoracic echocardiography (TTE), by which precise and accurate images of interatrial septum (IAS) can not be acquired, to diagnose patent foramen ovale (PFO) clearly. To evaluate the diagnostic value of biplanar transesophageal echocardiography (TEE) for PFO, TTE and biplanar TEE were performed simultaneously in 270 patients. It was found that in 7 patients patent foramen ovale was detected only through longitudinal planes of biplanar TEE. IAS, which consists of primitive septum and membrane of fossa ovalis, can be directly visualized by two-dimensional images of TEE; in patients with PFO, a dull color flow, which shunts from the right atria to the left atria through the gap between primitive septum and fossa ovalis, can be detected by color Doppler flow images. Furthermore, some right-to-left shunting microbubbles through the valve of patent fossa ovalis can be discovered by cardiac acoustic contrast echocardiography. In conclusion, biplanar TEE combined with color Doppler image and cardiac acoustic contrast facilitates a definite diagnosis of patent foramen ovale as the excellent anatomic images of IAS can be obtained from multiple views under this kind of performance.  相似文献   
8.
9.
江油市粮食中霉菌污染调查   总被引:6,自引:0,他引:6  
邓明林  陈虹 《现代预防医学》1997,24(1):100-101,104
对江油市胡豆,黄豆,玉米,大米,麦子,碗豆共375件样品进行霉菌污染调查。调查表明:粮食中霉菌平均侵染率87.8%,其中黄豆,碗豆污染较轻,其侵浸率明显低于小麦,大米,胡豆。胡豆,碗豆,黄豆以曲霉菌属为主;小麦以交链孢霉为主,大米以青霉菌属为主;玉米以预  相似文献   
10.
自1990年以来收治直径在2-5.6cm的大、巨型垂体腺瘤33例。依肿瘤生长形态与扩展范围将其简略分为三种类型。A型:瘤体位于鞍内或侵入蝶窦;B型;瘤体呈椭圆形或哑铃向鞍上扩展,三脑室明显移位抬高;C型:瘤体巨大侵入三脑室阻塞室间孔或明显的鞍周扩展。  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