全文获取类型
收费全文 | 129187篇 |
免费 | 11220篇 |
国内免费 | 8114篇 |
专业分类
耳鼻咽喉 | 1051篇 |
儿科学 | 1659篇 |
妇产科学 | 2485篇 |
基础医学 | 15382篇 |
口腔科学 | 2149篇 |
临床医学 | 16730篇 |
内科学 | 21171篇 |
皮肤病学 | 1510篇 |
神经病学 | 7126篇 |
特种医学 | 4448篇 |
外国民族医学 | 70篇 |
外科学 | 13541篇 |
综合类 | 18923篇 |
现状与发展 | 24篇 |
一般理论 | 7篇 |
预防医学 | 8119篇 |
眼科学 | 3723篇 |
药学 | 13036篇 |
114篇 | |
中国医学 | 6046篇 |
肿瘤学 | 11207篇 |
出版年
2024年 | 290篇 |
2023年 | 1663篇 |
2022年 | 4040篇 |
2021年 | 5972篇 |
2020年 | 4272篇 |
2019年 | 4158篇 |
2018年 | 4256篇 |
2017年 | 3794篇 |
2016年 | 3563篇 |
2015年 | 5340篇 |
2014年 | 6705篇 |
2013年 | 6324篇 |
2012年 | 9251篇 |
2011年 | 10114篇 |
2010年 | 6119篇 |
2009年 | 4886篇 |
2008年 | 6778篇 |
2007年 | 6771篇 |
2006年 | 6782篇 |
2005年 | 6732篇 |
2004年 | 4703篇 |
2003年 | 4423篇 |
2002年 | 3739篇 |
2001年 | 3261篇 |
2000年 | 3329篇 |
1999年 | 3465篇 |
1998年 | 2262篇 |
1997年 | 2184篇 |
1996年 | 1584篇 |
1995年 | 1481篇 |
1994年 | 1289篇 |
1993年 | 848篇 |
1992年 | 1247篇 |
1991年 | 1092篇 |
1990年 | 953篇 |
1989年 | 839篇 |
1988年 | 722篇 |
1987年 | 665篇 |
1986年 | 518篇 |
1985年 | 479篇 |
1984年 | 275篇 |
1983年 | 194篇 |
1982年 | 138篇 |
1981年 | 138篇 |
1980年 | 94篇 |
1979年 | 135篇 |
1978年 | 72篇 |
1976年 | 58篇 |
1975年 | 66篇 |
1974年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Chromosome 13q neocentromeres: molecular cytogenetic characterization of three additional cases and clinical spectrum 总被引:3,自引:0,他引:3
Li S Malafiej P Levy B Mahmood R Field M Hughes T Lockhart LH Wu Z Huang M Hirschhorn K Velagaleti GV Daniel A Warburton PE 《American journal of medical genetics》2002,110(3):258-267
We report three new cases of chromosome 13 derived marker chromosomes, found in unrelated patients with dysmorphisms and/or developmental delay. Molecular cytogenetic analysis was performed using fluorescence in situ hybridization (FISH) with chromosome-specific painting probes, alpha satellite probes, and physically mapped probes from chromosome 13q, as well as comparative genomic hybridization (CGH). This analysis demonstrated that these markers consisted of inversion duplications of distal portions of chromosome 13q that have separated from the endogenous chromosome 13 centromere and contain no detectable alpha satellite DNA. The presence of a functional neocentromere on these marker chromosomes was confirmed by immunofluorescence with antibodies to centromere protein-C (CENP-C). The cytogenetic location of a neocentromere in band 13q32 was confirmed by simultaneous FISH with physically mapped YACs from 13q32 and immunofluorescence with anti-CENP-C. The addition of these three new cases brings the total number of described inv dup 13q neocentic chromosomes to 11, representing 21% (11/52) of the current overall total of 52 described cases of human neocentric chromosomes. This higher than expected frequency suggests that chromosome 13q may have an increased propensity for neocentromere formation. The clinical spectrum of all 11 cases is presented, representing a unique collection of polysomy for different portions of chromosome 13q without aneuploidies for additional chromosomal regions. The complexity and variability of the phenotypes seen in these patients does not support a simple reductionist view of phenotype/genotype correlation with polysomy for certain chromosomal regions. 相似文献
992.
在自行研制的电子自旋共振成像(Electron spin resonance imaging, ESRI)系统上建立了活体皮肤电子自旋共振成像的实验模型.观测了氮氧自由基化合物2,2,6,6-四甲基哌啶-1-氧(2,2,6,6-tetramethyl-1-piperidinyloxy,TEMPO)穿透小鼠皮肤组织的动态过程和浓度分布情况.成像结果显示TEMPO化合物对不同方法处理后的皮肤组织的透皮特性有明显差别.TEMPO水溶液难以穿透皮肤,而溶解在二甲基亚枫(Dimethyl sulfoxide,DMSO)中的脂溶性TEMPO溶液可以渗入并穿透皮肤.皮肤表层的角质蛋白对TEMPO有明显的阻隔性, 而且化合物渗入或透过皮肤组织的量具有较强的时间依赖性.本研究结果提示ESRI技术为动态研究某些特殊结构化合物的透皮特性提供了科学有效的分析手段. 相似文献
993.
Chung-Chuan Chou Shengmei Zhou Hideki Hayashi Motoki Nihei Yen-Bin Liu Ming-Shien Wen San-Jou Yeh Michael C. Fishbein James N. Weiss Shien-Fong Lin Delon Wu Peng-Sheng Chen 《The Journal of physiology》2007,580(3):895-906
We hypothesize that remodelling of action potential and intracellular calcium (Cai ) dynamics in the peri-infarct zone contributes to ventricular arrhythmogenesis in the postmyocardial infarction setting. To test this hypothesis, we performed simultaneous optical mapping of Cai and membrane potential ( V m ) in the left ventricle in 15 rabbit hearts with myocardial infarction for 1 week. Ventricular premature beats frequently originated from the peri-infarct zone, and 37% showed elevation of Cai prior to V m depolarization, suggesting reverse excitation–contraction coupling as their aetiology. During electrically induced ventricular fibrillation, the highest dominant frequency was in the peri-infarct zone in 61 of 70 episodes. The site of highest dominant frequency had steeper action potential duration restitution and was more susceptible to pacing-induced Cai alternans than sites remote from infarct. Wavebreaks during ventricular fibrillation tended to occur at sites of persistently elevated Cai . Infusion of propranolol flattened action potential duration restitution, reduced wavebreaks and converted ventricular fibrillation to ventricular tachycardia. We conclude that in the subacute phase of myocardial infarction, the peri-infarct zone exhibits regions with steep action potential duration restitution slope and unstable Cai dynamics. These changes may promote ventricular extrasystoles and increase the incidence of wavebreaks during ventricular fibrillation. Whereas increased tissue heterogeneity after subacute myocardial infarction creates a highly arrhythmogenic substrate, dynamic action potential and Cai cycling remodelling also contribute to the initiation and maintenance of ventricular fibrillation in this setting. 相似文献
994.
人大肠癌中Ⅳ型胶原酶与基底膜免疫组织化学双重染色研究 总被引:1,自引:0,他引:1
目的观察Ⅳ型胶原酶和基底膜在大肠癌生长中的相互关系及Ⅳ型胶原酶的表达与p21的表达之间的关系。方法应用免疫组化双标记方法,对86例人大肠癌组织的Ⅳ型胶原酶表达及基底膜的改变作对照研究。结果大肠癌组织中Ⅳ型胶原酶的阳性率为83.72%(73/86),与对照组癌周正常肠粘膜的阳性率10%差异有非常显著意义(P<0.01)。同时,双染色显示Ⅳ型胶原酶阳性的癌组织基底膜表现为不连续,出现缺口、片段缺失或完全消失等形态。此外,肠癌中Ⅳ型胶原酶的分布与p21的表达呈正相关(r=0.974,p<0.01)。结论Ⅳ型胶原酶的分泌对肠癌基底膜破坏起重要作用,可以作为判断大肠癌生长特性的辅助指标。 相似文献
995.
Delivery of a hammerhead ribozyme specifically down-regulates the production of fibrillin-1 by cultured dermal fibroblasts 总被引:4,自引:1,他引:4
Kilpatrick MW; Phylactou LA; Godfrey M; Wu CH; Wu GY; Tsipouras P 《Human molecular genetics》1996,5(12):1939-1944
The hammerhead ribozyme is a small catalytic RNA molecule. Potential
hammerhead ribozymes that possess a catalytic domain and flanking sequence
complementary to a target mRNA can cleave in trans at a putative cleavage
site within the target molecule. We have investigated the potential of
hammerhead ribozymes to down-regulate the product of the fibrillin-1 gene
(FBN1). Fibrillin is a 347 kDa glycoprotein that is a major constituent of
the elastin-associated microfibrils. Mutations in the FBN1 gene are
responsible for Marfan syndrome (MFS), a common systemic disorder of the
connective tissue. Many FBN1 mutations responsible for MFS appear to act in
a dominant-negative fashion, raising the possibility that reduction of the
amount of product from the mutant FBN1 allele might be a valid therapeutic
approach for MFS. A trans-acting hammerhead ribozyme (FBN1-RZ1) targeted to
the 5' end of the human FBN1 mRNA has been designed and synthesized, and
shown to cleave its target efficiently in vitro. FBN1-RZ1 cleavage is
magnesium dependent and efficient at both 37 and 50 degrees C. Delivery of
the FBN1-RZ1 ribozyme into cultured dermal fibroblasts, by receptor-
mediated endocytosis of a ribozyme-transferrin-polylysine complex,
specifically reduces both cellular FBN1 mRNA and the deposition of
fibrillin in the extracellular matrix. These results suggest that the use
of hammerhead ribozymes is a valid approach to the study of fibrillin gene
expression and possibly to the development of a therapeutic approach to
MFS.
相似文献
996.
构建突变MyD88真核表达质粒(MyD88 DN),转染人呼吸道上皮细胞株A549,探讨其对绿脓杆菌及其分泌产物刺激IL-8表达的影响.结果显示突变MyD88成功构建入pcDNA3.1/zeo真核表达质粒,转染A549细胞后,可降低绿脓杆菌培养上清或活菌刺激诱导的IL-8分泌.提示突变MyD88可阻断绿脓杆菌感染引起的呼吸道上皮细胞IL-8释放,为呼吸道炎症的基因治疗提供了新的靶基因. 相似文献
997.
Diversity of rotavirus strains among children with acute diarrhea in China: 1998-2000 surveillance study 总被引:24,自引:0,他引:24
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fang ZY Yang H Qi J Zhang J Sun LW Tang JY Ma L Du ZQ He AH Xie JP Lu YY Ji ZZ Zhu BQ Wu HY Lin SE Xie HP Griffin DD Ivanoff B Glass RI Gentsch JR 《Journal of clinical microbiology》2002,40(5):1875-1878
As part of a national rotavirus surveillance activity, we collected fecal specimens from 3,177 children with acute diarrhea in 10 regions of China between April 1998 and April 2000 and screened them for rotavirus. Rotavirus was detected in 41% (n = 1,305) of specimens, and in these, G1 was the predominant serotype (72.6%), followed by G3 (14.2%), G2 (12.1%), G4 (2.5%), G9 (0.9%), and G untypeable (0.7%). Among 327 G-typed strains tested for P genotype, 14 different P-G combinations were identified, with the globally common strains P[8]G1, P[4]G2, P[8]G3, and P[8]G4 representing 75.6% of all typed rotavirus strains. Among the uncommon strains, 11 were P[6]G9, and others included P[6]G1, P[6]G3, and five novel P-G combinations (P[9]G1, P[4]G1, P[4]G3, P[4]G4, and P[8]G2). Our results indicate that while the common rotavirus strains remain predominant, the diversity of strains is much greater than was previously recognized. 相似文献
998.
Palmer SL Gajjar A Reddick WE Glass JO Kun LE Wu S Xiong X Mulhern RK 《Neuropsychology》2003,17(4):548-555
Fifty children diagnosed with medulloblastoma completed 188 psychological evaluations using the Wechsler Intelligence Scales for Children (D. Wechsler, 1974, 1991) over a 7-year study period following 35-40 Gy postoperative craniospinal irradiation. Random coefficient models were used to predict the trend in the children's intellectual performance as a function of time since diagnosis, with both patient and treatment variables as parameters of this function. A quadratic model demonstrated a delay prior to decline in performance for older patients, whereas the younger patients showed an immediate loss of performance with a plateau at approximately 6 years postdiagnosis. A steeper decline was found for those with higher baseline performance. Clinicians may use the proposed predictive model to identify those patients who are at risk of significant intellectual decline. 相似文献
999.
自发性高血压大鼠的微血管改变及其与血管内皮细胞损伤的关系 总被引:7,自引:1,他引:7
目的:探讨自发性高血压大鼠(SHR)的微血管改变与血管内皮细胞(VEC)损伤的关系。方法:以10只成年Wistar-Kyoto大鼠(WKY)为正常对照组(WKY组)。观察、计数10只成年SHR的肠壁微动脉管径和分支数,同时测定血浆亚硝酸根(NO2-)和内皮素(ET)并与WKY组对照。结果:SHR组的肠壁各级微动脉管径较WKY组变细(P<0.01~0.001)、各级微动脉总条数较WKY组减少(P<0.001~0.0001);SHR组的血浆NO2-水平和K值[10g(NO2-/ET)」较WKY组低(P<0.05~0.001),而ET较WKY组高(P<0.05)。血压和K值分别与肠壁微动脉管径和条数呈负相关和正相关(P<0.005~0.001)。结论:高血压的微血管结构异常与VEC损伤有密切的关系。 相似文献
1000.
Reading Julian P.; Huffman John L.; Wu Joy C.; Palmer Frances T.; Harton Gary L.; Sisson Michael E.; Keyvanfar Keyvan; Gresinger Thomas H.; Cochrane William J.; Fallon Lee A.; Menapace-Drew Gianna F.; Cummings Emilie A.; Jones Shirley L.; Black Susan H.; Schulman Joseph D.; Levinson Gene 《Molecular human reproduction》1995,1(7):362-367
The discovery of nucleated erythrocytes in maternal circulationprovides a potential source for non-invasive prenatal diagnosis.We have evaluated the use of a three-stage procedure to determinethe number of cells that are of fetal rather than maternal origin.First, monoclonal antibodies specific for CD45 and CD14 wereused in conjunction with a magnetic (MACS) column to depleteunwanted leukocytes from maternal blood. This was followed bya positive MACS enrichment for nucleated erythrocytes, usingan anti-CD71 (transferrin receptor) monoclonal antibody. Todiscriminate between fetal nucleated erythrocytes and thoseof maternal origin, enriched fractions were simultaneously stainedwith an anti-fetal haemoglobin (HbF) antibody and hybridizedwith probes specific for X and Y chromosomes. Samples were thensubjected to blind analysis along with negative control samplesfrom non-pregnant volunteers. Using this dual analysis, we wereable to determine that less than one nucleated erythrocyte perml of maternal blood was of fetal origin. Small numbers of thesefetal cells were found in 87.5% of pregnancies, ranging from6 to 35 weeks gestational age. Comparison of HbF and X/Y probedata also suggests that the fetal cells are less suitable forfluorescence in-situ hybridization (FISH) analysis than similarpreparations from other sources. cell separation methods/fluorescence in-situ hybridization/hereditary diseases/polymerase chain reaction/pregnancy 相似文献