全文获取类型
收费全文 | 158227篇 |
免费 | 15743篇 |
国内免费 | 5202篇 |
专业分类
耳鼻咽喉 | 1339篇 |
儿科学 | 1714篇 |
妇产科学 | 1664篇 |
基础医学 | 18201篇 |
口腔科学 | 5182篇 |
临床医学 | 15564篇 |
内科学 | 17091篇 |
皮肤病学 | 1798篇 |
神经病学 | 10189篇 |
特种医学 | 4899篇 |
外国民族医学 | 12篇 |
外科学 | 12709篇 |
综合类 | 23873篇 |
现状与发展 | 11篇 |
一般理论 | 3篇 |
预防医学 | 25567篇 |
眼科学 | 2102篇 |
药学 | 19339篇 |
188篇 | |
中国医学 | 8694篇 |
肿瘤学 | 9033篇 |
出版年
2024年 | 583篇 |
2023年 | 2931篇 |
2022年 | 5772篇 |
2021年 | 7913篇 |
2020年 | 7215篇 |
2019年 | 6184篇 |
2018年 | 5791篇 |
2017年 | 6165篇 |
2016年 | 6127篇 |
2015年 | 6234篇 |
2014年 | 10825篇 |
2013年 | 11730篇 |
2012年 | 10170篇 |
2011年 | 10933篇 |
2010年 | 8227篇 |
2009年 | 8018篇 |
2008年 | 7803篇 |
2007年 | 7742篇 |
2006年 | 6567篇 |
2005年 | 5756篇 |
2004年 | 4782篇 |
2003年 | 4196篇 |
2002年 | 3259篇 |
2001年 | 3061篇 |
2000年 | 2526篇 |
1999年 | 2230篇 |
1998年 | 1930篇 |
1997年 | 1760篇 |
1996年 | 1519篇 |
1995年 | 1377篇 |
1994年 | 1311篇 |
1993年 | 1036篇 |
1992年 | 1006篇 |
1991年 | 810篇 |
1990年 | 732篇 |
1989年 | 717篇 |
1988年 | 610篇 |
1987年 | 546篇 |
1986年 | 420篇 |
1985年 | 546篇 |
1984年 | 419篇 |
1983年 | 269篇 |
1982年 | 299篇 |
1981年 | 235篇 |
1980年 | 230篇 |
1979年 | 172篇 |
1978年 | 114篇 |
1977年 | 89篇 |
1976年 | 104篇 |
1974年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 33 毫秒
961.
Expression of human immunodeficiency virus type 1gag gene using genetically engineered herpes simplex virus type 1 recombinants 总被引:1,自引:0,他引:1
Angela Rösen-Wolff Karl Raab Lothar Zöller Gholamreza Darai Josef Eberle Friedrich Deinhardt 《Virus genes》1990,4(4):325-337
Infectious herpes simplex virus type 1 (HSV-1) recombinants were constructed by inserting the cDNA sequence of the human immunodeficiency virus type 1 (HIV-1)gag gene (from nucleotide position 675 [SacI] to 3859 [Asp 718] of the cDNA sequences of HIV-1 strain BH-10) within the DNA sequences of theBamHI DNA fragment B of the genome of an apathogenic HSV-1 strain HFEM. This HSV-1 strain possesses a 4.1-kbp deletion within theBamHI DNA fragment B between 0.762 and 0.789 map units of the viral genome, which allows the insertion of at least 4 kbp of foreign genetic material into this particular region. The DNA sequences of the immediate early promoter (IE4) of HSV-1 that were inserted upstream from thegag gene were used as a promoter. The screening of 205 virus stocks derived from individual plaques revealed that 46 recombinant viruses harbor HIV-1gag-specific DNA sequences. However, it was found that only six of the recombinant viruses are able to express thegag gene product of HIV-1. This indicates that the ratio of the positive recombination events is about 2.9%. 相似文献
962.
963.
1519例胎儿心电图的临床价值和相关因素分析 总被引:1,自引:0,他引:1
目的对1519例胎儿全部实行常规胎儿心电图(FECG)监测工作,探讨胎儿心电图应用情况,并对异常FECG结合临床,进行临床原因分析.方法采用随机湘样方法,应用杭州产FECG-D型胎儿心电图分析仪进行监测.结果发现采用横导联方式进行监测检出率为53.5%:在孕22w进行监测检出率为45.8%;异常FECG检出率为7.64%.结论对1519例FECG的监测发现采用横导联方式并在孕22w~26w期间进行监测检出率最高、波形效果好.并对监测发现的导致FECG异常改变的临床原因与胎儿宫内窘迫的关系进行浅要分析. 相似文献
964.
Bartels MN Jelic S Ngai P Gates G Newandee D Reisman SS Basner RC De Meersman RE 《Respiratory physiology & neurobiology》2004,144(1):91-98
Heart rate variability (HRV) and systolic blood pressure variability (BPV) during incremental exercise at 50, 75, and 100% of previously determined ventilatory threshold (VT) were compared to that of resting controlled breathing (CB) in 12 healthy subjects. CB was matched with exercise-associated respiratory rate, tidal volume, and end-tidal CO(2) for all stages of exercise. Power in the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, >0.15-0.4 Hz) for HRV and BPV were calculated, using time-frequency domain analysis, from beat-to-beat ECG and non-invasive radial artery blood pressure, respectively. During CB absolute and normalized power in the LF and HF of HRV and BPV were not significantly changed from baseline to maximal breathing. Conversely, during exercise HRV, LF and HF power significantly decreased from baseline to 100% VT while BPV, LF and HF power significantly increased for the same period. These findings suggest that the increases in ventilation associated with incremental exercise do not significantly affect spectral analysis of cardiovascular autonomic modulation in healthy subjects. 相似文献
965.
Kubicek每搏心输出量计算公式的三维有限元仿真研究 总被引:1,自引:0,他引:1
我们从 Kubicek模型三维有限元仿真的角度对 Kubicek每搏心输出量计算公式的临床应用价值进行了研究。在计算机仿真研究中 ,我们对比了模型仿真结果、具体采用 Kubicek每搏心输出量计算公式所得结果以及所设模型的理论计算结果。仿真结果表明 :模型中阻抗改变与主动脉中血液容积改变之间存在着近似的线性关系 ,证明了 Kubicek每搏心输出量计算公式具有一定的临床应用价值 ,同时也为心阻抗血流图基础理论提供了新的研究途径。 相似文献
966.
Paramyxoviruses of type 1 (PMV-l) isolated from pigeons were genetically analyzed. A part of the fusion and the matrix protein genes were amplified and sequenced, Typical amino acid sequences associated with virulence were determined at the fusion protein cleavage site in all PMV-1 isolates. All Slovene pigeon PMV-1 strains share high amino acid sequence similarity with other pigeon strains. In the phylogenetic tree, they are clustered together with pigeon PMV-1 isolates with moderate pathogenicity. Phylogenetic analysis obtained from the fusion and the matrix protein gene alignments showed the same branching order. Viruses circulating among pigeons were found to form quite unique lineage of virulent NDV strains. 相似文献
967.
Peeters MW Thomis MA Maes HH Loos RJ Claessens AL Vlietinck R Beunen GP 《Behavior genetics》2005,35(5):551-563
Purpose: To determine whether the observed phenotypic stability in explosive strength during adolescence, as measured by inter-age
correlations in vertical jump (VTJ), is mainly caused by genetic and/or environmental factors. Methods: Subjects are from the Leuven Longitudinal Twin Study (LLTS) (n = 105 pairs, equally divided over five zygosity groups). VTJ data were aligned on age at peak height velocity (APHV) to attenuate
the temporal fluctuations in inter-age correlations caused by differences in timing of the adolescent growth spurt. Simplex
models were fitted using structural equation modelling. Results: After aligning the data on APHV, the annual inter-age correlations show a clear simplex structure over a 4 year interval.
The best fitting models included additive genetic and unique environmental sources of variation. Heritability estimates ranged
between 60.8% (CI 37.7%–77.2%) and 87.3% (CI 74.2%–94.0%) for boys and between 76.5% (CI 56.7%–89.0%) and 88.6% (CI 77.8%–94.1%)
for girls. Up to 56.4% and 62.8% of the total variation at the last measurement occasion is explained by additive genetic
factors that already explained a significant amount of variation at previous measurement occasions in boys and girls respectively.
It thus can be concluded that the observed stability of explosive strength during adolescence is mainly caused by a stable
genetic influence in boys and girls. Conclusions: Additive genetic factors seem to be the main cause of the observed phenotypic stability in VTJ performance in boys and girls
during adolescence. 相似文献
968.
The use of Fourier transforms based on orthogonal sinusoidal functions is well established in the analysis of spectral components in noisy medical signals. In this paper the use of Walsh transformations based on orthogonal discrete signals is described for the analysis of ‘slow-wave’ rhythms in the gastro-intestinal tract of mammals. The Walsh transform approach has the advantage that very fast algorithms can be developed since multiplications involving sinusoidal functions are replaced by additions and subtractions. These algorithms are very suitable for simple microprocessors and it is shown that, for determining the frequency of gut rhythms, simple filtering and signal conditioning preceding the microprocessor dispenses with the need for analogue to digital conversion. Hence a very simple digital microprocessing system for the continuous monitoring of gut rhythms has been produced. It has also been extended to provide filtering of signals via forward and inverse Walsh transforms. 相似文献
969.
本文对肠道运动进行分析,从结构上研究肠鸣音的产生机理和肠鸣音的时域、频域特点,从而得到其物理模型,并用等效电路来模拟肠鸣音的产生,为研究肠鸣音的数学模型,以及临床医学研究提供了方便。 相似文献
970.
Identification of a Thymidylate Synthase Gene within the Genome of Chilo Iridescent Virus 总被引:1,自引:0,他引:1
The thymidylate synthase (TS, EC 2.1.1.45) is essential for the de novo synthesis of dTMP in pro- and eucaryotic organisms. Consequently it plays a major role in the replication of the DNA genome of a cell or a DNA virus. The gene encoding the TS of Chilo iridescent virus (CIV) was identified by nucleotide sequence analysis of the viral genome and was mapped within the EcoRI CIV DNA fragments G and R. Computer assisted analysis of the DNA nucleotide sequence between the genome coordinates 0.482 and 0.489 revealed an open reading frame (ORF) of 885 nucleotides. This ORF was found to encode a polypeptide of 295 amino acid residues (33.9 kDa) that showed significant homologies to known TS of different species including mammals, plants, fungi, protozoa, bacteria, and DNA viruses. The highest amino acid homologies were found between the CIV-TS and the TS of herpesvirus ateles (54.0%), Saccharomyces cerevisiae (51.8%), herpesvirus saimiri (51.0%), rhesus monkey rhadinovirus (50.7%), mouse (50.5%), rat (50.2%), varicella-zoster virus (50.2%), equine herpesvirus 2 (50.0%), and the human TS (48.4%). The CIV-TS contains six amino acid domains that are highly conserved in the TS of other species. Within these domains the major amino acid residues are present for which a functional role has been reported. The CIV-TS was found to be more closely related to the TS of eucaryotes than to the TS of procaryotes indicating the phylogenetic origin of the CIV-TS gene. The identification of a TS gene in the genome of CIV is the first report of a viral TS that is not encoded by a herpesvirus or a bacteriophage. 相似文献