全文获取类型
收费全文 | 104926篇 |
免费 | 10437篇 |
国内免费 | 3102篇 |
专业分类
耳鼻咽喉 | 826篇 |
儿科学 | 1204篇 |
妇产科学 | 990篇 |
基础医学 | 12039篇 |
口腔科学 | 4848篇 |
临床医学 | 10967篇 |
内科学 | 10281篇 |
皮肤病学 | 1309篇 |
神经病学 | 6557篇 |
特种医学 | 3240篇 |
外国民族医学 | 11篇 |
外科学 | 7124篇 |
综合类 | 15881篇 |
现状与发展 | 8篇 |
一般理论 | 3篇 |
预防医学 | 17115篇 |
眼科学 | 1231篇 |
药学 | 14070篇 |
113篇 | |
中国医学 | 6071篇 |
肿瘤学 | 4577篇 |
出版年
2024年 | 273篇 |
2023年 | 1848篇 |
2022年 | 2944篇 |
2021年 | 5113篇 |
2020年 | 4860篇 |
2019年 | 4253篇 |
2018年 | 3836篇 |
2017年 | 4171篇 |
2016年 | 4225篇 |
2015年 | 4127篇 |
2014年 | 7338篇 |
2013年 | 7859篇 |
2012年 | 7100篇 |
2011年 | 7460篇 |
2010年 | 5613篇 |
2009年 | 5223篇 |
2008年 | 4942篇 |
2007年 | 4973篇 |
2006年 | 4261篇 |
2005年 | 3700篇 |
2004年 | 3079篇 |
2003年 | 2799篇 |
2002年 | 2191篇 |
2001年 | 2073篇 |
2000年 | 1617篇 |
1999年 | 1400篇 |
1998年 | 1335篇 |
1997年 | 1207篇 |
1996年 | 1028篇 |
1995年 | 941篇 |
1994年 | 904篇 |
1993年 | 696篇 |
1992年 | 660篇 |
1991年 | 557篇 |
1990年 | 477篇 |
1989年 | 490篇 |
1988年 | 421篇 |
1987年 | 367篇 |
1986年 | 290篇 |
1985年 | 385篇 |
1984年 | 292篇 |
1983年 | 178篇 |
1982年 | 202篇 |
1981年 | 155篇 |
1980年 | 153篇 |
1979年 | 115篇 |
1978年 | 79篇 |
1977年 | 51篇 |
1976年 | 72篇 |
1974年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
991.
Salvatore Moricca Takao Kasuga Keith Mitchelson Alessandro Ragazzi Stephanos Diamandis 《Current genetics》1996,29(4):388-394
Mixed aeciospore isolates ofCronartium flaccidum andPeridermium pini were obtained from single-tree infections in Britain, Italy and Greece. The 5.8s ribosomal RNA gene and flanking intergenic transcribed spacer regions ITS 1 and ITS2 were found to be highly similar betweenC. flaccidum andP. pini. Within samples heterogeneity was detected at three nucleotide loci in the ITS1 and at four loci in the ITS2 suggesting that several fungal genotypes may occur at a single infection court. The heterogeneity was confirmed by heteroduplex polymorphism analysis of mixed aeciospore products. RFLP of the ribosomal intergenic spacer region 1 (IGSI) amplified from the same templates indicated limited sequence polymorphism in some copies of this repeated locus. Both the sexual and asexual forms ofC. flaccidum show evidence of sequence polymorphism in two independent, non-coding regions of the ribosomal gene array. Variation appears to be greater in the sexual formC. flaccidum, than in the monoaecious formP. pini. 相似文献
992.
本文对30年前首次住院经CCMD-2再诊断的203例精神分裂症采用通径分析方法,进行了遗传流行病学对照研究。结果显示精神分裂症的发病与产次、性格、家族史有关。 相似文献
993.
H1N2新亚型流感病毒神经氨酸酶基因来源的进一步研究 总被引:1,自引:0,他引:1
对流感病毒H1N2亚型重组株A/哈防/1/88、A/哈防/12/92以及H3N2亚型病毒株A/雅防/2/87、A/京防/57/898和A/粤防/1/92神经氨酸酶(NA)基因核苷酸全序列的测定,进一步弄清了A/哈防/1/88病毒株的NA基因确来自当时人群中流行的H3N2亚型病毒株,很可能是来自A/雅防/2/87类病毒株;而A/哈防/12/92病毒株的NA基因可能是与A/哈防/1/88病毒株的NA基 相似文献
994.
Frank Queisser Ralph Blüthner Dieter Bräuer Helmut Seidel 《European journal of applied physiology》1994,68(1):92-101
A group of 12 healthy men volunteered for the experiment. Electromyograms (EMG) were obtained from semispinalis capitis, splenius capitis, levator scapulae, and trapezius muscles. The flexion angle of the cervical spine was precisely adjusted to 0°, 10°, 20°, and 30° relative to the horizontal, with a constant angle of the atlanto-occipital joint. The subjects made eight short (about 2 s) vertical extension forces (6%, 12%,18%, 24%, 30%, 36%, 42%, and 48% of maximal voluntary peak contraction force). For each position, the centre of pressure under the head was determine as the basis for the calculation of the external lever arm. The presence of motor endplate regions was ascertained by multiple surface electrodes. The slopes of individual linear regression lines for the root mean square (rms)-values were dependent on the existence of endplates in the area of the electrodes — endplates caused smaller rms values per Newton metres of external torque. Significant intersubject differences between regression equations could not be eliminated by the normalization of EMG-parameters and/or torques. The elimination of gravity, the continuous monitoring of positions, and the consideration of localization of motor endplate regions were essential prerequisites for the acquisition of reliable relationships between EMG of different neck muscles and external torques. Two important conclusions were derived for the prediction of torques from EMG measurements: firstly, individual regression equations which take into account the position of the head and neck should be used; secondly, normalization procedures do not justify the application of average regressions to a group of subjects. 相似文献
995.
The homeotic mutationspineless-aristapedia (ss
a
) transforms the aristae into second tarsi. Flies with aSS
a
phenotype also show extremely positive geotaxis as measured in a Hirsch-type geotaxis maze. Other antennal mutants and flies with their aristae amputated do not show such extreme positive geotaxis. Deletion analysis has comapped the geotaxis effect withSS
a
in band 89C on the third chromosome. Finally, a biometrical analysis has detected additional genes on the X chromosome that also affects geotaxis.This work was supported by a Charles and Johanna Busch Memorial Award to T.R.M. and an Anne B. and James H. Leathem Scholarship Fund Award to P.A.M.Department of Biological Sciences and Bureau of Biological Research, Nelson Biological Laboratories 相似文献
996.
Germline mutations in breast cancer susceptibility genes, BRCA1 and BRCA2, are responsible for a substantial proportion of high‐risk breast and breast/ovarian cancer families. To characterize the spectrum of BRCA1 and BRCA2 mutations, we screened Czech families with breast/ovarian cancer using the non‐radioactive protein truncation test, heteroduplex analysis and direct sequencing. In a group of 100 high‐risk breast and breast/ovarian cancer families, four novel frame shift mutations were identified in BRCA1 and BRCA2 genes. In BRCA1, two novel frame shift mutations were identified as 3761‐3762delGA and 2616‐2617ins10; in BRCA2, two novel frame shift mutations were identified as 5073‐5074delCT and 6866delC. Furthermore, a novel missense substitution M18K in BRCA1 gene in a breast/ovarian cancer family was identified which lies adjacent just upstream of the most highly conserved C3HC4 RING zinc finger motif. To examine the tertiary structure of the RING zinc finger domain and possible effects of M18K substitution on its stability, we used threading techniques according to the crystal structure of RAG1 dimerization domain of the DNA‐binding protein. © 2000 Wiley‐Liss, Inc. 相似文献
997.
Etokebe GE Opsahl M Tveter AK Lie BA Thorsby E Vartdal F Spurkland A 《Tissue antigens》2003,61(6):443-450
Genomic typing of polymorphic loci may be hampered by ambiguous typing results. Moreover, robust methods for simultaneous sequencing of two alleles present in a given sample may be difficult to establish. We used denaturing high-performance liquid chromatography (DHPLC) for physical separation of HLA-A alleles before sequence-based genomic typing (SBT). Physical separation was achieved by resolution of heteroduplexes between the sample alleles and a modified reference probe by DHPLC followed by selective reamplification of the sample alleles present in heteroduplexes. Complementary strands of the reference probe and sample alleles for heteroduplex induction were obtained by lambda-exonuclease digestion. HLA-A genotyping of 101 individuals using DHPLC-SBT yielded better typing resolution compared with serological typing and genotyping by the sequence-specific primer-polymerase chain reaction (SSP-PCR) method. Physical separation of alleles using a modified reference probe allows for development of fully automated methods for genomic typing of highly polymorphic loci such as HLA. 相似文献
998.
John C. Loehlin 《Behavior genetics》1978,8(5):415-436
Three different published heredity-environment analyses of Jencks's summary correlations for IQ have yielded strikingly different results. It is shown empirically that differences in selection of data and in computational procedures and logical inconsistencies in specifying equations are not responsible for the differences in results. Rather, the differences trace to the underlying assumptions made by the various authors. The analyses suggest that the assumptions concerning genetic dominance, assortative mating, and special twin environments were especially critical, while those regarding selective placement and different modes of environmental transmission were not. 相似文献
999.
Publication Guidelines for Heart Rate Studies in Man 总被引:1,自引:0,他引:1
J. Richard Jennings W. Keith Bberg J. Stanford Hutcheson Paul Obrist Stephen Porges Graham Turpin 《Psychophysiology》1981,18(3):226-231
Publication guidelines are provided for the collection, quantification, and analysis of heart rate data. 相似文献
1000.
We report on clinical samples Stuttgart/97, Berlin/99 and Jasi/99 associated with aseptic meningitis. All three samples contained echovirus 4 (E4) but Stuttgart/97 was simultaneous infected with echovirus 30 (E30). The genetic relationship of the E4 strains was assessed using RT-PCR and direct sequencing of amplicons derived from the genomic region encoding the capsid protein VP1. The sequences have been compared with each other and with sequences of further E4 strains obtained from GenBank. The analysis confirms that sequences of recent isolates have drifted away from elderly strains over a longer period of time. Several amino acid changes in assumed antigenic sites of the VP1 gene may be sufficient to cause changes in antigenic specificity and therefore they may be a reason for failure of serological typing of some new antigenic E4 variants. 相似文献