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   14176篇
  免费   1078篇
  国内免费   188篇
耳鼻咽喉   69篇
儿科学   55篇
妇产科学   96篇
基础医学   639篇
口腔科学   138篇
临床医学   1233篇
内科学   583篇
皮肤病学   42篇
神经病学   303篇
特种医学   261篇
外科学   549篇
综合类   1968篇
预防医学   519篇
眼科学   103篇
药学   693篇
  10篇
中国医学   8014篇
肿瘤学   167篇
  2024年   37篇
  2023年   187篇
  2022年   427篇
  2021年   597篇
  2020年   626篇
  2019年   363篇
  2018年   318篇
  2017年   413篇
  2016年   497篇
  2015年   451篇
  2014年   1414篇
  2013年   867篇
  2012年   1307篇
  2011年   1278篇
  2010年   1021篇
  2009年   749篇
  2008年   587篇
  2007年   560篇
  2006年   548篇
  2005年   526篇
  2004年   466篇
  2003年   482篇
  2002年   311篇
  2001年   277篇
  2000年   167篇
  1999年   138篇
  1998年   119篇
  1997年   105篇
  1996年   99篇
  1995年   83篇
  1994年   74篇
  1993年   61篇
  1992年   54篇
  1991年   37篇
  1990年   34篇
  1989年   19篇
  1988年   23篇
  1987年   19篇
  1986年   14篇
  1985年   22篇
  1984年   15篇
  1983年   11篇
  1982年   5篇
  1981年   7篇
  1980年   10篇
  1979年   3篇
  1978年   5篇
  1977年   4篇
  1976年   3篇
  1975年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
建设符合自身特点的品牌医院特色文化   总被引:1,自引:0,他引:1  
张琳菲 《医学信息》2004,17(3):144-145
本文简述了医院文化自身的特点,着重探讨打造符合自身特点的品牌医院特色文化的措施和途径。  相似文献   
72.
用封闭群大耳白家兔雌性24只,随机分为三组。对照组动物不加任何处理,发热组和电针组动物i.v.内毒素(ET)引起发热反应,发热组动物i.v.ET后80min体温上升了1.18℃,而电针组动物体温仅上升了0.35℃,比较两组动物的体温上升高度差异非常显著(P<0.001)。给ET后80min处死动物,观察动物丘脑下部腺苷酸环化酶(AC)及磷酸二酯酶(PDE)活性的变化。发热组动物AC活性增强和对照组比较差异非常显著(P<0.001);电针组动物AC活性减弱和对照组比较差异非常显著(P<0.01)。发热组和电针组动物PDE活性均增强与对照组比较差异均非常显著(P<0.001)。实验结果表明,发热组AC和PDE的活性均增强,而电针组AC活性明显减弱,PDE的活性增强。作者推论:家兔ET性发热时丘脑下部环一磷酸腺苷(cAMP)含量增加是由于AC活性增强使cAMP生成增加,电针组动物丘脑下部cAMP含量减少是由于AC活性减弱,PDE活性增强结果cAMP生成减少而分解增加所致。  相似文献   
73.
探讨铁蛋白ferrztin,Ft在鉴别胸腹液良、恶性质的临界值。用RIA法测定218份由不同病因引起的胸腹液标本铁蛋白(pleuraleffusionferritin,PFt)及其同期血清铁蛋白(SFt)。依据临床确诊资料,将标本进行良、恶性病例分组,比较两组PFt、SFt,计算PFt/SFt比值,用ROC曲线选择PFt用于良、恶性质鉴别的最佳临界值。结果表明,良性组PFt为142.4±38.6μg/L,SFt为89.7±43.5μg/L,PFt/SFt为1.46±0.55;恶性组PFt为576.5±239.1μg/L,SFt为189.6±81.7μg/L,PFt/SFt为3.67±1.48;PFt用于鉴别胸腹液良、恶性质的临界值为400μg/L。以恶性积液PFt≥400μg/L、PFt/SFt≥3,良性积液PFt<400μg/L、PFt/SFt<3为实验诊断标准鉴别胸腹腔积液的良、恶性质,灵敏度为84.5%、特异性为87.5%,准确性为92.8%。  相似文献   
74.
Summary The surface electromyogram (EMG) from active muscle and oxygen uptake ( ) were studied simultaneously to examine changes of motor unit (MU) activity during exercise tests with different ramp increments. Six male subjects performed four exhausting cycle exercises with different ramp slopes of 10, 20, 30 and 40 W · min–1 on different days. The EMG signals taken from the vastus lateralis muscle were stored on a digital data recorder and converted to obtain the integrated EMG (iEMG). The was measured, with 20-s intervals, by the mixing chamber method. A non-linear increase in iEMG against work load was observed for each exercise in all subjects. The break point of the linear relationship of iEMG was determined by the crossing point of the two regression lines (iEMGbp). Significant differences were obtained in the exercise intensities corresponding to maximal oxygen uptake ( ) and the iEMGbp between 10 and 30, and 10 and 40 W · min –1 ramp exercises (P < 0.05). However, no significant differences were obtained in and corresponding to the iEMGbp during the four ramp exercises. With respect to the relationship between and exercise intensity during the ramp increments, the -exercise intensity slope showed significant differences only for the upper half (i.e. above iEMGbp). These results demonstrated that the and at which a nonlinear increase in iEMG was observed were not varied by the change of ramp slopes but by the exercise intensity corresponding to and the iEMGbp was varied by the change of ramp slopes. In addition, the significant differences in the exercise intensity slopes for the upper half of the tests would suggest that the recruitment patterns of MU and/or muscle metabolic state might be considerably altered depending upon the ramp slope increments.  相似文献   
75.
缺血性脑血管疾病是一个非常复杂的病理生理过程 ,是多种机制共同作用的结果。本文从针刺对实验性脑缺血在脑组织形态学改变、血液流变学、脑微循环等方面的研究进展作一综述。  相似文献   
76.
The production and serologic, as well as immunochemical properties of a cytotoxic murine IgG monoclonal antibody (Tü109) that precipitates HLA-class I molecules, are described. In the microcytotoxicity assay Tü109 supernatant was demonstrated on a panel of 424 HLA-ABC, -DR, -DQ, -MT typed normal Caucasian blood donors to define an epitope on HLA-B locus molecules in great association with the supertypic specificity Bw4. Reactivity of supernatant showed MHC linked inheritance of the Tü109 determinant and discriminated the HLA-Bw4/Bw6 associated HLA-B locus split antigens. Weak or lack of binding on lymphocytes from some HLA-Bw4 heterozygous individuals, particularly typing for HLA-Bw44, appeared to be due to qualitative and/or quantitative variations of HLA-B locus molecules on the cell surface. With Tü109 ascites fluid, however, extra-reactivity on all HLA-Bw6+ cells was demonstrated. Preferential binding of supernatant to HLA-Bw4, but reactivity of ascites fluid with HLA-Bw6+ molecules in addition, was furthermore confirmed by IEF analysis of antigens immunoprecipitated with Tü109 from cell lysates. Thus the antibody may help to analyze the evolutionary relationship of the diallelic specificities Bw4 and Bw6.  相似文献   
77.
The classification of some of the extractable birch pollen antigens as allergens was established by crossed radioimmunoelectrophoresis (CRIE). In CRIE the major allergen (antigen 23) exhibited the strongest “radiostaining” and only a few other components of birch pollen extract were visibly radiostained. The major allergen and a preparation containing mainly the minor allergens, antigens 25 and 19, were isolated from a crude aqueous birch pollen extract by a combination of anion-exchange, size-exclusion, and chelate chromatography. Antigen 23 was purified to near homogeneity. The molecular weights and the pIs of antigens 23, 25, and 19 were determined to be 17,000 daltons, pI 5.25 (5.5, 5.0); 25,000 daltons, pI 5.0 (4.9, 5.4); and 29,000 daltons, pI 6.2 (5.4), respectively. The classification of antigen 23 as the major allergen in birch pollen was supported by results of RAST inhibition experiments, RAST screening, and skin prick testing.  相似文献   
78.
Of sera from 1,878 Japanese blood donors who carried hepatitis B surface antigen (HBsAg), 420 were subtyped as adw (22.4%) and 1,443 as adr (76.8%); only 15 (0.8%) contained HBsAg of subtype ayw or ayr. Sera with HBsAg/adr had higher HBsAg titres than those with HBsAg/adw (geometric mean of haemagglutination titre: 10.1 +/- 2.4 vs. 9.7 +/- 2.4, p less than 0.01), and a higher prevalence of hepatitis B e antigen (24% vs. 13%, p less than 0.001). Carriers of HBsAg/adr progressively predominated over those of HBsAg/adw with increasing age. Of sera from 1,863 carriers of HBsAg/adw or HBsAg/adr, 182 (9.8%) contained HBsAg particles with both subtypic determinants in the w/r allele. The presence of w and r determinants on the same particles was ascertained by sandwiching them between monoclonal antibody with the specificity for w and that with the specificity for r. HBsAg particles of compound subtype (adwr) were found more often in sera with hepatitis B e antigen than those without it (145/403 [36.0%] vs. 37/1,460 [2.5%], p less than 0.001). Sera with HBsAg/adwr particles had HBsAg titres higher than those without them (12.4 +/- 1.9 vs. 9.7 +/- 2.3, p less than 0.001). HBsAg/adwr particles arise from phenotypic mixing of the S-gene product of wild-type virus and that of mutants with point mutations for subtypic changes. The results obtained indicated that HBV strains of subtype adr have a higher replicative activity than those of adw, and suggested that mutations in the S gene for subtypic changes would be associated with an active replication of hepatitis B virus.  相似文献   
79.
耳穴电参数时变关系实验表明,在测量起始t<2τ时,因瞬变作用,电位E(t)和压降U(t)为瞬态响应,响应函数呈指数关系,特征参数为弛豫时间τ,τ≈RC;t>2τ时,为时变间期。电路分析给出数学描述,并与耳穴和模拟实验结果较相符。提示,时变特征应以t>2τ后提取,静态电测量时,采样应避开瞬变期,可提高准确性。该工作对正确鉴别时变性和特征提取,全面认识耳穴电特性具有重要意义。  相似文献   
80.
Several syndiotactic polystyrene (sPS) samples have been synthesized by using different catalytic systems. Their stereochemistry has been determined by 13C NMR spectra in both the aliphatic CH2 and aromatic C1 resonance regions. The observed peaks have been unambiguously assigned to specific hexads and heptads, respectively, and their intensities have been used to draw the percent of defects (meso dyads) in the polymer chains. On the hypothesis that chain defects are at the origin of chain folding and thus determine the thickness of crystalline lamellae, we performed differential scanning calorimetry (DSC) analysis on the same samples, and their thermal parameters were measured. A model was developed to determine the amount of steric defects from the DSC melting‐peak profiles, and the results obtained were compared with the NMR results. A satisfactory agreement was found (correlation factor 0.96) in the explored range of defect concentrations (up to 2.5% of meso dyads). The possible influence of the extraction procedure of the amorphous fraction was found to be negligible. Thus, information on stereochemistry can be obtained from DSC experiments starting from as‐prepared (not extracted) samples.

  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