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   106520篇
  免费   9729篇
  国内免费   7642篇
耳鼻咽喉   892篇
儿科学   1186篇
妇产科学   1286篇
基础医学   12818篇
口腔科学   2006篇
临床医学   14432篇
内科学   15905篇
皮肤病学   1046篇
神经病学   5697篇
特种医学   3835篇
外国民族医学   64篇
外科学   10542篇
综合类   18234篇
现状与发展   33篇
一般理论   9篇
预防医学   6711篇
眼科学   3026篇
药学   10831篇
  89篇
中国医学   6003篇
肿瘤学   9246篇
  2024年   394篇
  2023年   1918篇
  2022年   4578篇
  2021年   5592篇
  2020年   4161篇
  2019年   3592篇
  2018年   3750篇
  2017年   3395篇
  2016年   3111篇
  2015年   4841篇
  2014年   5732篇
  2013年   5104篇
  2012年   7639篇
  2011年   8535篇
  2010年   5292篇
  2009年   4153篇
  2008年   5314篇
  2007年   5588篇
  2006年   5497篇
  2005年   5454篇
  2004年   3518篇
  2003年   3277篇
  2002年   2845篇
  2001年   2390篇
  2000年   2638篇
  1999年   2897篇
  1998年   1897篇
  1997年   1780篇
  1996年   1371篇
  1995年   1232篇
  1994年   1023篇
  1993年   678篇
  1992年   844篇
  1991年   715篇
  1990年   635篇
  1989年   544篇
  1988年   464篇
  1987年   414篇
  1986年   299篇
  1985年   234篇
  1984年   128篇
  1983年   100篇
  1982年   59篇
  1981年   60篇
  1980年   47篇
  1979年   61篇
  1977年   16篇
  1973年   11篇
  1972年   10篇
  1971年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
根据呼气相胸片中肺部区域灰度较高的特点,通过边缘提取和边缘跟踪确定胸部区域,运用最大类间方差方法确定图像分割的阈值.再提取出肺部区域,然后求出肺部的灰度均值。但这样的结果并不理想。于是在此基础上提出修正方案,即以肺部灰度均值和骨骼灰度均值的比值作为特征值.即比例法。此方法可以较客观的识别呼气相胸片。最后用类间距离对这两种方法进行了量化比较。  相似文献   
102.
We review our studies on the role of polycyclic aromatic hydrocarbon (PAH)-DNA adducts in breast cancer. Additionally we report on analyses of the reliability of the scoring procedures used with immunohistochemical assay for PAH-DNA adducts and of potential bias arising from the use of benign breast disease (BBD) controls. We conducted a case-control study utilizing two control groups: BBD controls who donated tissue and blood samples, and healthy controls who donated blood samples. In comparisons of tumor tissue from cases and benign tissue from BBD controls, increasing adduct levels were significantly associated with case-control status [odds ratio (OR) = 2.40, 95% confidence interval (CI) 1.18-4.92], whereas in comparisons of nontumor tissue from cases and benign tissue from BBD controls the association was nonsignificant (OR = 1.97, 95% CI 0.94-4.17). We also show among cases, but not among BBD controls, that the GSTM1 null genotype is associated with increased adduct levels in breast tissue. Our reliability study found the scoring procedures used with the immunohistochemical assay to have high reliability, 0.93 in nontumor, 0.82 in tumor, and 0.74 in benign tissues. However, we found that the technician significantly contributed to the total variability of a series of data. Finally, we did not find a consistent bias to the null associated with the use of BBD controls; however, BBD controls may overestimate the prevalence of family history of breast cancer compared to that of healthy controls (18% vs.14%). We hypothesize that the higher prevalence results from a referral bias and discuss how this may influence our results.  相似文献   
103.
目的 探讨肝黏膜相关淋巴组织淋巴瘤的临床病理特征。方法 对1例罕见多脏器恶性肿瘤术后肝黏膜相关淋巴瘤病例结合文献进行临床、病理和免疫组化分析。结果 患者于8年和3年前先后发生胃恶性间质瘤、阴囊阴茎皮肤湿疹样癌,有长期化疗史。肿瘤组织学以单核样B细胞为主,并有淋巴滤泡和淋巴上皮病变形成。免疫表型示瘤细胞CD45、CD79α、CD20阳性,CD5、CD10、ALK、TdT阴性,bcl—2、Ki—67少数肿瘤细胞阳性。结论 肝黏膜相关淋巴瘤可以发生于多脏器恶性肿瘤术后,其发病可能与长期使用免疫抑制剂有关,诊断本病时需与肝继发性淋巴瘤及肝的炎性假瘤鉴别。  相似文献   
104.
A multi-channel hearing prosthesis for profound-to-total hearing loss   总被引:1,自引:0,他引:1  
A multi-channel cochlear implant hearing prosthesis providing 22 separate channels of stimulation has been developed. The electronics for the implantable receiver-stimulator have been incorporated on a single chip, using digital circuits and employing CMOS technology. The chip is enclosed in a titanium capsule with platinum/ceramic electrode feed-throughs. A pocket-sized speech processor and directional microphone extract the following speech parameters: signal amplitude, fundamental frequency and formant frequency. The fundamental frequency is coded as electric pulse rate, and formant frequency by electrode position. The speech processor has been realized using hybrid circuits and CMOS gate arrays. The multi-channel prosthesis has undergone a clinical trial on four postlingually deaf patients with profound-total hearing losses. The speech perception results indicate that they were able to obtain open-set speech recognition scores for phonetically balanced words, CID sentences and spondees. In all cases the tests showed significant improvements when using the cochlear prosthesis combined with lipreading compared to lipreading alone.  相似文献   
105.
LJM, a 41-year-old schizophrenic Chinese man with bilateral anterior cingulate gyrus (Brodmann's area 24) lesions and also a small lesion in right amygdala after an operation, was compared with normal as well as brain-damaged and schizophrenic controls in identification of morphed facial expressions of six basic emotions. In repeated administrations of the test for recognition of facial emotions, over a 1- year period, LJM performed significantly worse for expressions of fear compared with the three groups of controls. Recognition of other emotions was not significantly different from that of the controls, except that his recognition of disgust during the first session (but not in two subsequent sessions) was worse than normal and brain-damaged controls but not worse than schizophrenic controls. The dissociation between recognition of fear and other emotions supported the view that the brain has separable networks for processing different emotions, and that the right amygdala as well as the anterior part of bilateral cingulate gyrus are possible substrates involved in the special network for perception of fear. The results from the various groups of Chinese subjects indicate that they perceive emotions in a categorical manner, and that the six basic emotions are likely to be cross-cultural universals.  相似文献   
106.
Alport's syndrome is characterized clinically by a nonimmune glomerulopathy, often accompanied by sensorineural hearing loss and lens abnormalities, frequently due to mutations in the COL4A5 gene. The association of AS with diffuse leiomyomatosis, a benign proliferation of smooth muscle that occurs most often in the esophagus, trachea, and female genitalia, has been reported. Recently, a deletion involving both the COL4A5 and COL4A6 genes has been reported in four unrelated families. We report an additional case with Alport's syndrome associated with leiomyomatosis carrying a deletion of both COL4A5 and COL4A6 genes. A detailed characterization of the genomic region involved in the deletion event has been performed. Our results demonstrate that the deletion removed exon l of COL4A5 and exons l and 2 of COL4A6. © 1994 Wiley-Liss, Inc.  相似文献   
107.
108.
109.
卵巢宫内膜样腺癌的病理组织学及组织化学分析   总被引:1,自引:0,他引:1  
本文通过对24肺卵巢宫内膜样腺癌的巨检,镜及组织化学染色等结果分析,提出按该瘤所含组织成分,将其分为单纯型及混合型两大类。单纯型中分化程度不同又再分成Ⅰ,Ⅱ,ⅢⅣ级。混合型中根据所含成分又再分为腺棘癌,腺鳞癌,透明细胞腺癌型,含粘液腺癌型及含浆液腺癌型。讨论了该瘤的临床表现,发病率,组织来源,病理特征,诊断步骤及各类型与预后之间的关系。  相似文献   
110.
脐带血清对骨髓粒—巨噬细胞集落形成的影响   总被引:1,自引:0,他引:1  
在骨髓细胞半固体琼脂培养体系中,研究脐带血清(CBs)对骨髓粒—巨噬细胞集落形成单位(CFU-GM)的影响,单纯应用CBs培养可使骨髓CFU-GM(x±s为26.0375±10.2327)显著的高于正常成人外周血清(PBs)组(x±s为11.5917±3.6047;P<0.001)。CBs加粒-巨噬细胞刺激因子,GM-CSF组CFU-GM(x±s为119.0792±35.0991)是单纯CBs组的4.57倍;而PBs加GMC-SF组(x±s为97.125±26.7559)是单纯PBs组的8.38倍。有白细胞介素-6(IL-6)存在的CBs组,CFU-GM(x±s为31.9333±10.9144)明显的高于单纯CBs组(P<0.02)。提示CBs中含有较高水平的内源性GM-CSF。  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