全文获取类型
收费全文 | 5783篇 |
免费 | 816篇 |
国内免费 | 112篇 |
专业分类
耳鼻咽喉 | 17篇 |
儿科学 | 184篇 |
妇产科学 | 195篇 |
基础医学 | 704篇 |
口腔科学 | 167篇 |
临床医学 | 639篇 |
内科学 | 1131篇 |
皮肤病学 | 27篇 |
神经病学 | 581篇 |
特种医学 | 177篇 |
外国民族医学 | 1篇 |
外科学 | 581篇 |
综合类 | 461篇 |
现状与发展 | 1篇 |
预防医学 | 647篇 |
眼科学 | 77篇 |
药学 | 546篇 |
1篇 | |
中国医学 | 102篇 |
肿瘤学 | 472篇 |
出版年
2024年 | 49篇 |
2023年 | 309篇 |
2022年 | 320篇 |
2021年 | 580篇 |
2020年 | 397篇 |
2019年 | 366篇 |
2018年 | 282篇 |
2017年 | 281篇 |
2016年 | 249篇 |
2015年 | 244篇 |
2014年 | 364篇 |
2013年 | 468篇 |
2012年 | 259篇 |
2011年 | 273篇 |
2010年 | 205篇 |
2009年 | 234篇 |
2008年 | 215篇 |
2007年 | 186篇 |
2006年 | 171篇 |
2005年 | 146篇 |
2004年 | 111篇 |
2003年 | 103篇 |
2002年 | 91篇 |
2001年 | 75篇 |
2000年 | 69篇 |
1999年 | 57篇 |
1998年 | 63篇 |
1997年 | 48篇 |
1996年 | 48篇 |
1995年 | 44篇 |
1994年 | 34篇 |
1993年 | 54篇 |
1992年 | 41篇 |
1991年 | 42篇 |
1990年 | 31篇 |
1989年 | 26篇 |
1988年 | 34篇 |
1987年 | 20篇 |
1986年 | 22篇 |
1985年 | 19篇 |
1984年 | 26篇 |
1983年 | 7篇 |
1982年 | 18篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有6711条查询结果,搜索用时 15 毫秒
31.
The universal algorithm of maturation for secretory and excretory protein precursors. 总被引:1,自引:0,他引:1
During maturation, most proteins undergo different posttranslational modifications. In most simple cases, signal peptidases remove the signal or leader peptide from the precursors of the secretory proteins during their translocation across the ER membrane. For biologically active proteins, such as enzymes, regulatory and defense proteins, toxins, etc., additional maturation-regulating mechanisms were shown to proceed with limited proteolysis of inactive precursors by specific enzymes. A number of specific enzymes from different cell types selectively cleave proproteins at specific processing sites. In this work, we analyzed the sequences of protein precursors synthesized in the excretory glands of different animals and identified new, non-traditional processing sites. They differ from the motifs previously identified in secreted proteins' precursors and enabled us to reconstruct the sequence of events leading to the conversion of protein precursors into the final products (mature proteins). We also found that in animals, the maturation mechanism of secretory and excretory proteins and the set of enzymes involved are species specific. The processing sites identified in protein precursors in this study are useful for a more detailed genome analysis and more accurate mature protein sequence prediction. 相似文献
32.
采用LabVIEW技术完成对心电、呼吸、无创血氧和无创血压信号的采集与处理,而后通过MATLAB模糊测量系统对采集的人体生理信号进行模糊预测分析。通过实验检验了人体生理信号检测、处理和模糊预测分析方法的可靠性。LabVIEW技术对人体生理信号的模糊预测分析是有效的,可用于检测阻塞性睡眠呼吸暂停患者的生理状态信号。 相似文献
33.
熵指数对异氟烷麻醉中切皮体动反应的预测作用 总被引:1,自引:0,他引:1
目的 研究熵指数(包括反应熵和状态熵)对异氟烷复合麻醉中切皮体动反应的预测作用并与双频谱指数(BIS)比较.方法 ASA Ⅱ级择期腹部手术患者20例,按切皮有无体动反应分为体动组(9例)和非体动组(11例).入室后常规监测,然后静注异丙酚、琥珀胆碱、芬太尼快诱导气管插管,持续吸入异氟烷,维持呼气末异氟烷浓度为1.3MAC,维持10min后开始手术,切皮前不用神经肌肉阻滞剂,如果发生体动,则按10%提高下一个患者异氟烷呼气末浓度,如果不动则按10%降低下一个患者异氟烷呼气末浓度.分别于入室、切皮前60s、30s、切皮后45s、120s对每例患者同时行熵指数和BIS监测.结果 两组患者的熵指数值有显著性差异(P<0.05),而BIS无显著性差异(P>0.05).反应熵和状态熵可以预测切皮体动,其预测概率(Pk)值分别为0.893 7和0.885 2,BIS不能预测切皮体动,Pk值是0.591 9,熵指数和BIS的Pk值之间有显著性差异(P<0.05),Pk与反应熵和状态熵的Logistic回归方程分别为ln [Pk/(1-Pk)]=32.517-0.481x和ln [Pk/(1-Pk)]=28.728-0.438x.结论 熵指数监测可以预测异氟烷麻醉中的切皮体动反应,值得临床推广应用. 相似文献
34.
The complexity of the RHD and RHCE genes, which is the greatest of all blood group systems, confounds analysis at the molecular level. RH DNA typing was introduced in 1993 and has been applied to prenatal testing. PCR-SSP analysis covering multiple polymorphisms was recently introduced for the screening and initial characterization of partial D. Our objective is to summarize the accrued knowledge relevant to the approaches to Rh phenotype prediction by DNA typing, their possible applications beyond research laboratories and their limitations. The procedures, results and problems encountered are highly detailed. It is recommended that DNA typing comprises an analysis of more than one polymorphism. We discuss future directions and propose a piecemeal approach to improve reliability and cost-efficiency of blood group genotyping that may eventually replace the prevalent serology-based techniques even for many routine tasks. Transfusion medicine is in the unique position of being able to utilize the most extensive phenotype databases available to check and develop genotyping strategies. 相似文献
35.
应用因特网对SARS病毒M蛋白B细胞抗原表位的预测 总被引:7,自引:1,他引:6
目的:预测SARS冠状病毒M蛋白的B细胞表位。方法:采用EMBOSS软件结合Hopp&woods亲水性参数、Janin可及性参数、极性参数、柔韧性参数及二级结构方案对SARS冠状病毒M蛋白的B细胞表位进行了预测,并用吴玉章等已建立的B细胞表位预测方法进行评述。结果:SARS冠状病毒M蛋白B细胞识别的表位可能位于第3~13和153~166位氮基酸等区域内或附近,这2个被预测的表位均含有β—转角和无规卷曲结构。结论:该研究对应用合成肽抗原进行SARS早期诊断研究及相关抗体的制备具有重要指导意义。 相似文献
36.
参考缓和加氢裂化(MHC)反应机理,开发了一种既能预测产品产率,又能预测产品性质的MHC动力学网络模型。以文献上发表的MHC实验数据为例,进行了参数估计,确定了动力学参数,给出了模型的标准差。本模型所预测的MHC结果,与文献数据吻合良好,具有良好的预测性能。 相似文献
37.
目的预测SARS病毒S蛋白(spike glycoprotein)部分片段(aa No.400~600 & aa No.1 100~1 195)的B-细胞表位.方法应用多种参数和方法进行综合分析,包括跨膜分析、保守区分析、同源性比较、Hopp & Woods亲水性参数、抗原性参数、可及性参数、β-转角、万氏法等综合预测方法.结果显示B-细胞识别的表位可能在436~456和1 136~1 146残基或其附近,这两个被预测的表位均含有β-转角和不规则卷曲结构.结论本研究为应用合成肽抗原制备抗SARS病毒S蛋白抗体、诊断非典型肺炎(severe acute respiratory syndrome, SARS)提供了依据. 相似文献
38.
G. Seghieri G. C. Bartolomei L. A. De Giorgio F. Innocenti A. Gironi M. Mian F. Franconi 《European journal of clinical pharmacology》1989,37(4):401-404
Summary Serum digoxin and beta-methyldigoxin (BMD) were measured in 165 elderly patients (age >60 years) admitted to hospital, of whom 109 had been treated at home with digoxin and 56 with BMD.The mean BMD level was significantly lower than that of digoxin (1.1 vs. 1.4 ng/ml). Creatinine clearance and daily dose were the variables most strongly associated with digoxin level, and the prescribed dose and serum albumin were the best predictors of the BMD concentration. Compliance was assessed by a compliance index (CI), namely the ratio of the measured glycoside concentration, corrected for creatinine clearance, over the expected steady-state dose, calculated from a hospitalized reference group. Compliant individuals in both treatment groups, i.e. those with a CI > the median value, were characterized by a lower daily dose and dosage frequency.Toxicity, whether clinical or electrocardiographic, was present in 9% of the patients and was associated only with a significantly higher mean serum level of the drug. 相似文献
39.
Measurements of IgE levels in the blood of neonates were investigated using filter paper for blood collection in mass screening of congenital metabolic disorders. Time-resolved fluoroimmunometric assay system for the measurement of filter paper blood IgE levels was also studied. In an analysis of the present results, IgE values of at least 0.015U/ml, the measurement limit, were considered as high. High IgE levels in filter paper blood were seen in 28 (7.2%) of the 389 cases. When the relation with serum IgE levels at 18 months of age was investigated in 134 of 389 subjects, high serum IgE levels were also found in about 86.7% of the subjects with high IgE levels in filter paper blood. In addition, when the relation between family history of atopic disease and presence of atopic disease in the first 18 months of age was investigated in 203 of the 389 subjects, about 90% of the subjects with a family history of atopic disease and high IgE levels in filter paper blood developed atopic disease. Since filter paper blood is routinely collected in Japan, IgE levels in this blood should be widely checked for the prediction of onset of atopic disease in infants. 相似文献
40.
The L RNA of three Lassa virus strains originating from Nigeria, Ghana/Ivory Coast, and Sierra Leone was sequenced and the data subjected to structure predictions and phylogenetic analyses. The L gene products had 2218-2221 residues, diverged by 18% at the amino acid level, and contained several conserved regions. Only one region of 504 residues (positions 1043-1546) could be assigned a function, namely that of an RNA polymerase. Secondary structure predictions suggest that this domain is very similar to RNA-dependent RNA polymerases of known structure encoded by plus-strand RNA viruses, permitting a model to be built. Outside the polymerase region, there is little structural data, except for regions of strong alpha-helical content and probably a coiled-coil domain at the N terminus. No evidence for reassortment or recombination during Lassa virus evolution was found. The secondary structure-assisted alignment of the RNA polymerase region permitted a reliable reconstruction of the phylogeny of all negative-strand RNA viruses, indicating that Arenaviridae are most closely related to Nairoviruses. In conclusion, the data provide a basis for structural and functional characterization of the Lassa virus L protein and reveal new insights into the phylogeny of negative-strand RNA viruses. 相似文献