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   23443篇
  免费   2451篇
  国内免费   1583篇
耳鼻咽喉   157篇
儿科学   359篇
妇产科学   253篇
基础医学   2918篇
口腔科学   356篇
临床医学   3172篇
内科学   3612篇
皮肤病学   214篇
神经病学   1541篇
特种医学   1014篇
外国民族医学   20篇
外科学   2206篇
综合类   3660篇
现状与发展   5篇
一般理论   5篇
预防医学   1433篇
眼科学   810篇
药学   2522篇
  33篇
中国医学   1409篇
肿瘤学   1778篇
  2024年   96篇
  2023年   400篇
  2022年   1072篇
  2021年   1321篇
  2020年   997篇
  2019年   867篇
  2018年   910篇
  2017年   741篇
  2016年   734篇
  2015年   1018篇
  2014年   1399篇
  2013年   1152篇
  2012年   1695篇
  2011年   1779篇
  2010年   1111篇
  2009年   951篇
  2008年   1159篇
  2007年   1126篇
  2006年   1193篇
  2005年   1079篇
  2004年   686篇
  2003年   728篇
  2002年   603篇
  2001年   466篇
  2000年   585篇
  1999年   559篇
  1998年   366篇
  1997年   372篇
  1996年   266篇
  1995年   250篇
  1994年   210篇
  1993年   126篇
  1992年   201篇
  1991年   142篇
  1990年   130篇
  1989年   101篇
  1988年   109篇
  1987年   98篇
  1986年   97篇
  1985年   76篇
  1984年   33篇
  1983年   29篇
  1979年   35篇
  1974年   35篇
  1973年   27篇
  1970年   23篇
  1969年   31篇
  1968年   23篇
  1967年   29篇
  1966年   30篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
在调查云南少数民族G6PD缺乏症时,采用G6PD硝基四氮唑蓝纸片法筛查,按WHO标准化方法进行生化变异型鉴定,再用错配碱基PCR引入酶切位点法进行DNA突变型研究,首次在傣族中发现G6PDcDNA突变型:1388G→A。  相似文献   
113.
A novel active L1 retrotransposon subfamily in the mouse   总被引:8,自引:1,他引:8  
Unlike human L1 retrotransposons, the 5' UTR of mouse L1 elements contains tandem repeats of approximately 200 bp in length called monomers. Multiple L1 subfamilies exist in the mouse which are distinguished by their monomer sequences. We previously described a young subfamily, called the T(F) subfamily, which contains approximately 1800 active elements among its 3000 full-length members. Here we characterize a novel subfamily of mouse L1 elements, G(F), which has unique monomer sequence and unusual patterns of monomer organization. A majority of these G(F) elements also have a unique length polymorphism in ORF1. Polymorphism analysis of G(F) elements in various mouse subspecies and laboratory strains revealed that, like T(F), the G(F) subfamily is young and expanding. About 1500 full-length G(F) elements exist in the diploid mouse genome and, based on the results of a cell culture assay, approximately 400 G(F) elements are potentially capable of retrotransposition. We also tested 14 A-type subfamily elements in the assay and estimate that about 900 active A elements may be present in the mouse genome. Thus, it is now known that there are three large active subfamilies of mouse L1s; T(F), A, and G(F), and that in total approximately 3000 full-length elements are potentially capable of active retrotransposition. This number is in great excess to the number of L1 elements thought to be active in the human genome.  相似文献   
114.
目的探讨全髋关节置换术均衡双下肢长度的临床意义和手术设计。方法回顾分析2000-2004年获得随访的单侧全髋关节置换手术病例48例,采用骨水泥型假体12髋,混合型假体36髋,术前双下肢等长30例(含股骨颈骨折患者),10例患肢长度短缩1.0-2.0cm,6例短缩2.0-4.0cm,2例短缩4.0-6.0cm。通过术前肢体长度测量及X片测量制定手术方案,选择假体、预估颈长和截骨平面;术中正确磨削髋臼,寻找最佳旋转中心,结合透视及特殊试验修正截骨平面,调节假体颈长,达到均衡双下肢长度的目的。结果全部病例采用Harris评分,优30例,良12例,中4例,差2例。术前等长30例巾术后出现5例手术侧延长1.0-2.0cm,1例延长2.5cm。术前不等长的18例中,术后恢复等长10例,6例手术侧延长1.0-2.0cm,2例术前重度短缩的先天性髋关节发育不良病人术后仍然短缩2.0-3.0cm。术后肢体等长35例Harris评分平均92.3分,术后肢体不等长13例Harris评分平均88.6分。结论全髋关节置换术的手术设计。手术技巧以及假体设计等诸多因素影响下肢长度,术后肢体不等长降低了患者的满意度。应重视术前测量及术中综合评价方法的运用,重视软组织平衡技术和肢长调节,掌握全髋置换术中均衡下肢长度的手术技术,进一步改善手术效果。  相似文献   
115.
The DMT1(Nramp2/DCT1) is a newly discovered proton-coupled metal-ion transport protein. The cellular localization and functional characterization of DMT1 suggest that it might play a role in physiological iron transport in the brain. In the study, we evaluated effects of dietary iron and age on iron content and DMT1 expression in four brain regions: cortex, hippocampus, striatum, substantia nigra. Total iron content in all regions was significantly lower in the low-iron diet rats and higher in the high-iron diet rats than that in the control animals, showing that dietary iron treatment for 6-weeks can alter brain iron levels. Contrary to our expectation, there was no significant alternation in DMT1(+IRE) and (-IRE) mRNA expression and protein content in all brain regions examined in spite of the existence of the altered iron levels in these regions after 6-weeks' diet treatment although TfR mRNA expression and protein level were affected significantly, as was expected. The data demonstrates that expression of DMT1(+IRE) and (-IRE) was not regulated by iron in these regions of adult rats. The lack of response of DMT1 to iron status in the brain suggests that the IRE of brain DMT1 mRNA might be not really iron-responsive and that DMT1-mediated iron transport might be not the rate-limiting step in brain iron uptake in adult rats. Our findings also showed that development can significantly affect brain iron and DMT1(+IRE) and (-IRE) expression but the effect varies in different brain regions, indicating a regionally specific regulation in the brain.  相似文献   
116.
Li L  Zou WZ  Wang SX  Wang SL  Wang W  Han ZH  Du J  Bo L 《中华病理学杂志》2005,34(7):385-388
目的了解Ⅲ型胶原肾小球病的形态学改变,并对Ⅲ型胶原可能的细胞来源进行初步探讨。方法对3例肾活检组织进行光镜、免疫荧光、电镜和Ⅰ、Ⅲ、Ⅳ型胶原及d平滑肌肌动蛋白(α-SMA)的免疫组织化学染色(SP法)观察。结果2例患者临床表现为肾病综合征,其中1例伴高血压,第3例表现为肾功能不全和肾性高血压。3例均无肾病家族史。光镜检查可见肾小球基膜内和系膜区弥漫性过碘酸-希夫反应阳性物质沉积,系膜细胞无明显增生。电镜检查在基膜内疏松层和系膜区可见大量胶原纤维沉积,系膜细胞胞膜下平行排列的束状微丝明显增加。免疫组织化学显示这些胶原纤维为Ⅲ型胶原,Ⅰ型和Ⅳ型胶原阴性,同时系膜区多数系膜细胞α-SMA阳性。结论Ⅲ型胶原肾小球病光镜、电镜及免疫组织化学上都有其特殊的病理改变。肾小球内激活的系膜细胞可能是Ⅲ型胶原的来源。  相似文献   
117.
非小细胞肺癌中p16 INK4/CDKN2基因的缺失和点突变   总被引:5,自引:0,他引:5  
目的为了探讨周期素依赖性激酶4抑制因子基因(p16INK4)与肺癌发生的关系。方法采用双重PCR-SSCP和序列分析方法,对31例原发性非小细胞肺癌中p16INK4基因的存在状况进行了研究。结果3例存在p16基因缺失(3/31),其中1例整个p16基因发生缺失,另两例则分别为外显子1和外显子2缺失;p16基因点突变2例(2/31),外显子1和外显子2各一例;并发现在这五例基因异常样品中,4例(2例缺失和2例点突变)样品均为淋巴转移的非小细胞肺癌(4/20)。结论提示p16基因失活和某些非小细胞肺癌(5/31)的发生有关,并且可能发生在癌症的晚期。  相似文献   
118.
119.
NAG微量酶反应比色法在IL-2活性检测中的应用   总被引:1,自引:0,他引:1  
本文研究了NAG微量酶反应比色法在IL-2活性检测中的应用,结果表明IL-2活性测定所用的CTLL-2细胞浓度与OD值呈直线关系(r=0.964715)。本文还探讨了NAG法在IL-2活性测定中CTLL-2细胞浓度,培养时间对检测效果的影响。本法与~3H—TdR掺入法和MTT法相比有较好的一致性。  相似文献   
120.
The thermo‐adjustable hydrophilic/hydrophobic properties of AB, ABA and BAB block copolymers in which A is poly(methyl vinyl ether) (PMVE) and B is poly(isobutyl vinyl ether) (PIBVE) have been investigated. The block copolymers were prepared by “living” cationic polymerization using sequential addition of monomers. The polymerizations were carried out with the system acetal/trimethylsilyl iodide as initiator and ZnI2 as activator. The initiating system based on diethoxyethane leads to AB block copolymers whereas the initiating system based on tetramethoxypropane leads to ABA or BAB triblock copolymers. Well‐defined block copolymers of different composition with controlled molecular weights up to approx. 10 000 have been prepared. When IBVE is added to living PMVE, PIBVE‐blocks form only in the presence of an additional amount of ZnI2, which is attributed to the fact that part of the ZnI2 is inactive because of complex formation with PMVE. At room temperature, the combination of hydrophilic (PMVE) and hydrophobic (PIBVE) segments provides the copolymers with surfactant properties. Above the lower critical solution temperature (LCST) of PMVE, situated around 36 °C, the PMVE‐blocks become hydrophobic and the amphiphilic nature of the block copolymers is lost. The corresponding changes in hydrophilic/hydrophobic balance have been evaluated by investigation of the emulsifying properties of the block copolymers for water/decane mixtures as a function of the temperature. Below the LCST, the block copolymers have emulsifying properties similar to or better than those of the commercial PEO‐PPO block copolymers (Pluronic®). Either oil‐in‐water or water‐in‐oil emulsions can be obtained, depending on the polymer architecture and the water/decane volume ratio. The emulsifying properties are strongly reduced or completely lost above 40 °C. Emulsions obtained with a PMVE36b‐PIBVE54 block copolymer for a water/decane (v/v) ratio of 85/15 remained stable for more than six months.

50/50 and a 85/15 water/decane w/o emulsion (15 g/l) with the PMVE36b‐PIBVE54 block copolymer at 20 °C.  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