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   26309篇
  免费   2611篇
  国内免费   1274篇
耳鼻咽喉   419篇
儿科学   163篇
妇产科学   518篇
基础医学   2421篇
口腔科学   440篇
临床医学   2143篇
内科学   2282篇
皮肤病学   292篇
神经病学   263篇
特种医学   1112篇
外国民族医学   37篇
外科学   5165篇
综合类   3860篇
现状与发展   8篇
预防医学   401篇
眼科学   173篇
药学   1147篇
  6篇
中国医学   386篇
肿瘤学   8958篇
  2024年   58篇
  2023年   423篇
  2022年   894篇
  2021年   1180篇
  2020年   968篇
  2019年   848篇
  2018年   827篇
  2017年   936篇
  2016年   1085篇
  2015年   1410篇
  2014年   1789篇
  2013年   1552篇
  2012年   1577篇
  2011年   1646篇
  2010年   1445篇
  2009年   1367篇
  2008年   1434篇
  2007年   1387篇
  2006年   1305篇
  2005年   1266篇
  2004年   1019篇
  2003年   897篇
  2002年   753篇
  2001年   645篇
  2000年   590篇
  1999年   506篇
  1998年   453篇
  1997年   343篇
  1996年   254篇
  1995年   233篇
  1994年   182篇
  1993年   143篇
  1992年   128篇
  1991年   90篇
  1990年   78篇
  1989年   79篇
  1988年   72篇
  1987年   61篇
  1986年   43篇
  1985年   45篇
  1984年   45篇
  1983年   29篇
  1982年   23篇
  1981年   30篇
  1980年   22篇
  1979年   15篇
  1978年   7篇
  1977年   4篇
  1975年   4篇
  1973年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
目的 探讨肺癌侵犯中央肺动脉继发肺低灌注的CT特征及其诊断价值。方法 对2 0例手术及病理证实的肺癌侵犯中央肺动脉 (cancerousinvasionofcentralpulmonaryarteriesinlungcancer,CICPA)患者术前肺血管DSA及增强螺旋CT(含高分辨率CT ,即HRCT)征象行前瞻性对照研究。根据DSA和CT胸膜下末梢肺动脉分布和数量变化 ,即肺血管征、肺毛细血管充盈度和肺实质强化后密度及时间 密度曲线变化 (即肺实质征 ) ,行两者间的盲法对照 ,统计学分析CT与DSA征象及其一致性 ,评估CT对CICPA继发肺低灌注的诊断价值。结果  2 0例手术病理证实的CICPA病例中 ,共3 0支肺叶动脉受累 ,DSA显示 90 % (2 7/3 0 )出现肺叶低灌注征象 ,CT诊断肺低灌注敏感度为 78%(2 1/2 7) ,特异度 10 0 % (3 /3 ) ,准确度 80 % (2 4/3 0 )。肺低灌注与CPA狭窄程度无明显相关性 (rs=0 40 ,P =0 0 73 )。CT与DSA的肺血管征一致性较好 (Kappa =0 69,P <0 0 0 1) ,而肺实质征一致性稍差 (Kappa =0 3 7,P =0 0 11)。结论 肺低灌注是肺癌侵犯中央肺动脉的常见表现 ,CT对其定性诊断具有重要价值 ,而定量判断有一定限度  相似文献   
32.
A lymph node metastasis in the neck or parotid region from an unknown primary melanoma is an uncommon occurrence. Out of a total of 300 patients with head and neck melanoma treated at the Netherlands Cancer Institute between 1976 and 1992, 17 (5.7%) presented in this way. The most common site for metastatic lymph nodes (18 nodes in 17 patients) was level V (n= 7), followed by the parotid region (n= 4), level II (n= 4), level III (n= 2), and level IV (n= 7). Two patients had local excision of the neck node metastasis only, while the remaining 15 patients underwent more extensive surgical treatment. The 5-year disease-specific survival rate in this group was 48%, with a median survival of 36 months, which is more or less similar to the prognosis of stage II melanoma of the head and neck with a known, surgically treated primary tumour. No relation was found between disease-free interval and sex, the number of positive lymph nodes or the duration of symptoms.  相似文献   
33.
总结94例脑转移瘤的CT诊断与临床资料。临床多以颅内压增高及脑组织损坏为主要征象。原发肿瘤部位按例数依次为肺癌、乳腺癌、鼻咽癌、甲状腺癌、胃癌和前列腺癌。原发肿瘤的症状常较隐匿,60%的病人首先发现脑转移瘤,然后才追查到原发肿瘤。当发现脑内多发或单发肿瘤时,应排除转移瘤。CT是诊断脑转移瘤的可靠方法,能准确地判断肿瘤的部位、大小、数目以及水肿范围与并发改变等情况。  相似文献   
34.
Metastatic carcinoma to the testis is very rare. Metastasis of prostate adenocarcinoma to testis was detected incidentally after bilateral orchiectomy for hormonal management of metastatic prostate carcinoma. The metastatic lesion was not identified in physical examination or in macroscopic dissection of the testis after surgery. Microscopy revealed an adenocarcinoma which, given the history of the patient and a positive immunohistochemical stain for PSA, was identified as metastatic prostatic adenocarcinoma.  相似文献   
35.
本研究应用层粘连蛋白(LN)抗体,对27例乳腺癌、5例乳腺良性病变进行了免疫组织化学研究。结果发现乳腺良性病变时,LN以均匀完整的线型阳性反应显示在乳腺导管及小叶基膜处。乳腺癌时,LN的染色表现为癌细胞胞浆内弥漫状阳性反应。27例乳腺癌中,癌细胞LN染色强度不同,伴有转移的乳腺癌LN染色多数较强,强度在++~的为7/12(58.3%);不伴有转移的病例,LN染色多数较浅或为阴性,强度在++~+++的病例为3/15(20%)。说明癌细胞内源性LN染色强弱与肿瘤转移密切相关,内源性LN的合成可能改变肿瘤细胞的浸润活性。  相似文献   
36.
恶性肿瘤的皮肤转移确与患者的病种、病理类型、术前后淋巴结转移情况、临床分期、手术类型、放疗及化疗的剂量、遗传因素有关。其出现于任何部位均提示预后不佳。  相似文献   
37.
BACKGROUND: We hypothesise that the density of proliferating cells at the invasive tumour front (ITF) has a positive relationship with prognostic and risk factors in human oral squamous cell carcinoma (SCC). METHODS: Tissues from 47 human oral SCC specimens were collected and stained with a monoclonal antibody directed against the Ki-67 antigen using a horseradish peroxidase based two-step immunostaining method. Counting was performed on two parallel sections at the ITF using an image analyser. The Ki-67 labelling index (LI) was determined by measuring the number of nuclei/mm(2) of epithelium. RESULTS: Our results show that the density of proliferating cells is related to clinical staging, with advanced stage of disease having a significantly higher Ki-67 LI compared with early stage of disease (2111 +/- 905 vs. 1908 +/- 913; P = 0.03). Importantly, this study shows that tumours that have metastasised have a significantly higher Ki-67 LI than tumours where distant metastasis was not detected (3257 +/- 650 vs. 1966 +/- 881; P < 0.0001). CONCLUSIONS: Cell proliferation, as measured by the Ki-67 LI at the ITF, has a positive relationship with clinical staging, tumour thickness, smoking status of the patient and alcohol consumption. Further, we suggest that a multicenter study with a large cohort of patients is indicated to fully elucidate whether cell proliferation at the ITF is directly related to patient survival.  相似文献   
38.
Lymph node (LN) metastases represent the most important negative prognostic factor in squamous cell carcinoma (SCC) of the oral cavity, even though controversies still exist regarding their management. The aim of this study was to retrospectively analyze our experience in surgical management of SCC of the oral cavity with particular focus on the prevalence and localization of lymph nodal metastases and recurrences. The clinical records of 89 consecutive patients treated from 1983 to 2002 by concomitant surgery on both the T and N sites, excluding those undergoing salvage surgery, were reviewed. A total of 119 neck dissections (ND) were performed. Survival outcomes were calculated by the Kaplan–Meier method, while univariate comparisons by the log-rank and non-parametric tests were performed between different groups of patients. Five-year overall and determinate survivals were 50 and 57%, respectively. LN metastases were observed in 52% (56% of these showing extracapsular spread) and their presence strongly correlated with determinate survival (p < 0.0001). The prevalence of clinical and occult nodal disease was not related to the pT status. Neck levels II (59%) and I (56%) were most frequently involved. Metastases to level IV accounted for 15% of positive LN, even though 28% of them turned out to be skip metastases. Five neck recurrences were observed, only one of which was salvaged by surgery. The high prevalence of clinical and occult LN metastases in this setting suggests that ND should be performed on a nearly routine basis, even for lesions with a low-T category and a cN0 neck. Moreover, ND should always encompass level IV due to the possibility of skip metastases, particularly in tumors involving the oral tongue. In patients with a cN+ neck, levels from I to V should be addressed, particularly in the presence of metastases at levels III and IV.  相似文献   
39.
①目的 探讨肺癌中血管内皮生长因子受体Flt1、KDR的表达与其转移及预后的关系。②方法 应用免疫组织化学PowerVisionTM PV90 0 0法 ,测定 75例肺癌标本中Flt1、KDR的表达。③结果 肺癌组织中Flt1、KDR的表达较为广泛 ,主要位于肿瘤细胞胞浆及胞膜上 ,纤维母细胞和血管内皮细胞胞浆中亦有表达。Flt1、KDR在肿瘤细胞中的阳性率均显著高于在间质纤维母细胞中的表达 (χ2 =6 .0 7、5 .88,P <0 .0 5 )。肿瘤细胞及纤维母细胞中该两种受体的阳性率在不同年龄、不同性别及不同病理类型、不同病理分级之间差异均无显著性 (χ2 =0 .0 1~4 .84 ,P >0 .0 5 ;P =0 .2 9~ 0 .79)。肿瘤细胞中Flt1、KDR的阳性表达率在 3组不同大小的肿瘤间差异均有显著性(χ2 =1 0 .35、7.2 9,P <0 .0 5 ) ,而纤维母细胞中差异均无显著性 (χ2 =2 .86、2 .5 6 ,P >0 .0 5 ) ;肿瘤细胞及纤维母细胞中Flt1、KDR的阳性率在淋巴结有、无转移两组间的差异均有显著性 (χ2 =4 .72~ 9.32 ,P <0 .0 5 ) ,在 3组不同术后生存时间病人间亦均有显著性差异 (χ2 =8.81~ 1 9.1 9,P <0 .0 5 )。肿瘤细胞中Flt1、KDR的表达呈极显著性正相关 (r =0 .4 4 ,P <0 .0 1 )。④结论 肺癌的生长主要依赖自分泌机制 ,联合检测Flt1、KDR可能对肺癌转移  相似文献   
40.
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