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   60091篇
  免费   5571篇
  国内免费   4280篇
耳鼻咽喉   640篇
儿科学   550篇
妇产科学   576篇
基础医学   6892篇
口腔科学   1205篇
临床医学   7864篇
内科学   8610篇
皮肤病学   674篇
神经病学   2641篇
特种医学   1936篇
外国民族医学   41篇
外科学   6055篇
综合类   10765篇
现状与发展   19篇
一般理论   14篇
预防医学   4565篇
眼科学   1679篇
药学   6411篇
  67篇
中国医学   3513篇
肿瘤学   5225篇
  2024年   240篇
  2023年   941篇
  2022年   2372篇
  2021年   3193篇
  2020年   2362篇
  2019年   1948篇
  2018年   2081篇
  2017年   1843篇
  2016年   1702篇
  2015年   2849篇
  2014年   3420篇
  2013年   2975篇
  2012年   4294篇
  2011年   4763篇
  2010年   3301篇
  2009年   2683篇
  2008年   3195篇
  2007年   3192篇
  2006年   3180篇
  2005年   3064篇
  2004年   2261篇
  2003年   2102篇
  2002年   1716篇
  2001年   1466篇
  2000年   1353篇
  1999年   1374篇
  1998年   920篇
  1997年   870篇
  1996年   638篇
  1995年   676篇
  1994年   561篇
  1993年   330篇
  1992年   371篇
  1991年   335篇
  1990年   291篇
  1989年   248篇
  1988年   203篇
  1987年   199篇
  1986年   133篇
  1985年   114篇
  1984年   65篇
  1983年   37篇
  1982年   22篇
  1981年   27篇
  1980年   8篇
  1979年   22篇
  1977年   1篇
  1976年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Entamoeba invadens, a parasite of reptiles, is a model for the study of encystation by the human enteric pathogen Entamoeba histolytica, because E. invadens form cysts in axenic culture. With approximately 0.5-fold sequence coverage of the genome, we were able to get insights into E. invadens gene and genome features. Overall, the E. invadens genome displays many of the features that are emerging from ongoing genome sequencing efforts in E. histolytica. At the nucleotide level the E. invadens genome has on average 60% sequence identity with that of E. histolytica. The presence of introns in E. invadens was predicted with similar consensus (GTTTGT em leader A/TAG) sequences to those identified in E. histolytica and Entamoeba dispar. Sequences highly repeated in the genome of E. histolytica (rRNAs, tRNAs, CXXC-rich proteins, and Leu-rich repeat proteins) were found to be highly repeated in the E. invadens genome. Numerous proteins homologous to those implicated in amoebic virulence, (Gal/GalNAc lectins, amoebapores, and cysteine proteinases) and drug resistance (p-glycoproteins) were identified. Homologs of proteins involved in cell cycle, vesicular trafficking and signal transduction were identified, which may be involved in en/excystation and cell growth of E. invadens. Finally, multiple copies of a number of E. invadens genes coding for predicted enzymes involved in core metabolism and the targets of anti-amoebic drugs were identified.  相似文献   
92.
Studies by comparative genome hybridization have suggested that 5p amplification is related to tumor progression in urinary bladder cancer. In this study seven genes (TAS2R, ADCY2, DNAH5, CTNND2, TRIO, ANKH, and MYO10) located to 5p15.31-5p15.1 were analyzed by fluorescence in situ hybridization using a tissue microarray containing samples from tumors and cell lines with known 5p amplification by comparative genome hybridization. Amplification frequency was highest for TRIO, which maps to 5p15.2 and encodes a protein with a putative role in cell-cycle regulation. To further investigate the role of TRIO amplification in bladder cancer, a tissue microarray containing samples from 2317 bladder tumors was used for fluorescence in situ hybridization analysis. TRIO amplification was strongly associated with invasive tumor phenotype, high tumor grade, and rapid tumor cell proliferation (Ki67 LI) (P < 0.0001 each). Only 7 of 456 pTaG1/G2 tumors (1.5%) but 62 of 485 pT1-4 carcinomas (12.8%) had TRIO amplification. TRIO amplification was not associated with poor prognosis. Using a frozen bladder tumor tissue microarray RNA in situ hybridization confirmed that TRIO is up-regulated in amplified tumors. It is concluded that TRIO up-regulation through amplification has a potential role in bladder cancer progression.  相似文献   
93.
血糖感应型胰岛素给药智能载体的研究进展   总被引:1,自引:0,他引:1  
胰岛素控制释放高分子载体系统一直是国内外科技工作者的研究热点 ,迄今已经研究报道了多种具有不同工作原理的血糖感应型胰岛素给药智能载体。本文基于国内外大量研究文献 ,综述了血糖感应型胰岛素控制释放智能化高分子载体的研究进展。  相似文献   
94.
The biologic characteristics of the two human giant-cell lung carcinoma strains with high (strain D) and low metastatic potential (strain C) were studied, including karyotype of chromosome, intracellular free calcium ([Ca2+]i), morphologic changes of cell surface and the expression of nm23-H1, p53, ras, c-myc, c-erbB2, bcl-2 genes and PCNA. The correlation between different biologic features and the metastatic potential of the two strains was analyzed. We found: 1) Both strains had the karyotypic abnormality of -13, -14, -15, +20, +21 with seven same marker chromosomes. Only strain D had the karyotypic abnormality of +7, -17, -18, +X, 7p+; 2) [Ca2+]i of the strain C (984.7 +/- 573.8) and D (517.6 +/- 216.6) was significantly different (p < 0.05). The amplitude of intracellular calcium oscillations of strain C was lower than the one of strain D; 3) strain C had more villous-like protrusions on the cell surface, whereas strain D had more bubble-like protrusions; 4) The expression of nm23-H1 and p53 protein of strain C was all higher than that of strain D. The expression of PCNA of strain C was lower than strain D; 5) nm23-H1 mRNA levels of strain C was lower than that of strain D. We consider that the karyotype of chromosomes, intracellular free calcium, the structure of cell membrane and the expression of nm23-H1 gene, p53 gene, PCNA could be closely related to the metastatic potential of human giant-cell lung carcinoma. They could be used as the sign for judging whether the tumor will metastasize in clinical practice as well as in judging the prognoses of patients.  相似文献   
95.
Brain images produced on the EMI 7070 scanner exhibit a "cupping" artefact due to a combination of beam hardening and scatter effects. The magnitude of the artefact is assessed by statistically analysing a series of concentric regions of interest in the final image. Once the magnitude has been determined it can be subtracted from the image. While the result of the technique does not modify the clinical analysis of images it does increase the observer's appreciation of the image. Both the technique and clinical results are presented, and the implications of this type of reconstruction artefact removal discussed.  相似文献   
96.
催经止孕药Ru-486的临床药代动力学   总被引:4,自引:1,他引:3  
应用高效液相色谱法(HPLC)研究了抗孕激素药,Ru-486的临床药代动力学。六名志愿受试者,一次口服Ru-486 50毫克后测得该药的药代动力学各项参数,血药半寿期t 1/2 33.0小时,一级消除速率常数Kel 0.021 hr~(-1),血药表观容积Vd 120.1 Liter,体内血药总廓清率Cl2.5 Liter/hr,药-时曲线下面积Auc 19825.1 ng/ml/hr。实验表明,服药后一小时血药浓度迅即达高峰,随后转入消除期,血浆药物浓度在消除相的头4~8小时消除较快,而后逐渐减慢,持续24小时,到48小时血药浓度已较低(0.15±0.07μg/ml)。  相似文献   
97.
lve cirrhotic patients underwent subtotal splenectomy. The operative technique involved pre- servation of anatomic segments and suture of an omental patch to the residual spleen. With knowledge on segmental vascular anatomy in splenomegaly, sub- total splenic resection can be readily accomplished with ease and safety. Follow-up of the 12 patients showed that the preserved spleen had normal uptake of 51Cr denatured erythrocyte isotope, high grade serum IgM, and effect of alleviating fever after splenectomy. Splenic scan and clinical immunologic survey revealed the functional capacity of splenic remnant, and the lower percentage of "pocked" RBCs, an important clue to eusplenia. Thus, the normal function and size retained of the residual spleen were saved. If long-term follow-up confirms the value of segmental splenectomy, it may become an adjuvant treatment in lowering portal hyperten sion in cirrhotic patients.  相似文献   
98.
周围神经炎系指由于中毒、感染、感染后或变态反应等所引起的多数周围神经同时发病。临床表现为多发性或单一性的周围神经麻痹,对称性或非对称性肢体远端感觉障碍,弛缓性瘫痪及自主神经功能障碍的疾病。胶鞋中的聚氯乙烯经皮肤中毒致周围神经炎临床未见报道,需引起人们高度警惕,现将1997~2000年我院收治12例经皮肤中毒致周围神经炎患者报道如下。  相似文献   
99.
建立了蠕变局部损伤法模型,并给出单元进入损伤态的判据和失效的临界拉伸应变条件,局部蠕变损伤理论的实质就是试样是多种不同蠕变性能材料的统一,并由蠕变应力再分布得到证实,应用有限元对双缺口圆试样作了蠕变局部损伤分析,启裂时间和断裂蠕变应变值均与实验结果相吻合。  相似文献   
100.
From July 1 994to June 1 999,5 4 5 onychomyco-sis patients were treated with Itraconazole and com-pleted their treatment courses with complete follow-up in out- patientdepartment.The recovery rate was83.1 4% and 79.2 3% in fingernail and toenail dis-eases respectively.But following phenomena werefound:( 1 ) Some new nails stopped growing in cer-tain length,even if the treatment continued;( 2 )Some damaged nails reappeared soon after the treat-ment ceased;( 3) Some damaged nails with deep- co…  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