全文获取类型
收费全文 | 1004篇 |
免费 | 60篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 66篇 |
妇产科学 | 31篇 |
基础医学 | 140篇 |
口腔科学 | 22篇 |
临床医学 | 120篇 |
内科学 | 229篇 |
皮肤病学 | 27篇 |
神经病学 | 30篇 |
特种医学 | 114篇 |
外科学 | 78篇 |
综合类 | 11篇 |
预防医学 | 71篇 |
眼科学 | 13篇 |
药学 | 51篇 |
中国医学 | 3篇 |
肿瘤学 | 76篇 |
出版年
2022年 | 8篇 |
2021年 | 27篇 |
2020年 | 10篇 |
2019年 | 20篇 |
2018年 | 15篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 50篇 |
2012年 | 43篇 |
2011年 | 58篇 |
2010年 | 41篇 |
2009年 | 35篇 |
2008年 | 35篇 |
2007年 | 58篇 |
2006年 | 35篇 |
2005年 | 41篇 |
2004年 | 34篇 |
2003年 | 25篇 |
2002年 | 33篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 19篇 |
1998年 | 42篇 |
1997年 | 44篇 |
1996年 | 37篇 |
1995年 | 24篇 |
1994年 | 28篇 |
1993年 | 19篇 |
1992年 | 16篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 31篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1970年 | 4篇 |
排序方式: 共有1087条查询结果,搜索用时 15 毫秒
1.
2.
Factors influencing women to undergo screening mammography 总被引:2,自引:0,他引:2
3.
Braffman BH; Coleman BG; Ramchandani P; Arger PH; Nodine CF; Dinsmore BJ; Louie A; Betsch SE 《Radiology》1994,190(3):797
4.
5.
Rupture of the distal biceps tendon: evaluation with MR imaging 总被引:2,自引:0,他引:2
6.
7.
Federico E Turkheimer Paul Edison Nicola Pavese Federico Roncaroli Alexander N Anderson Alexander Hammers Alexander Gerhard Rainer Hinz Yan F Tai David J Brooks 《Journal of nuclear medicine》2007,48(1):158-167
PET with [(11)C]-(R)-PK11195 is currently the modality of choice for the in vivo imaging of microglial activation in the human brain. In this work we devised a supervised clustering procedure and a new quantification methodology capable of producing binding potential (BP) estimates quantitatively comparable with those derived from plasma input with robust quantitative implementation at the pixel level. METHODS: The new methodology uses predefined kinetic classes to extract a gray matter reference tissue without specific tracer binding and devoid of spurious signals (in particular, blood pool and muscle). Kinetic classes were derived from an historical database of 12 healthy control subjects and from 3 patients with Huntington's disease. BP estimates were obtained using rank-shaping exponential spectral analysis (RS-ESA) (both plasma and reference input) and the simplified reference tissue model (SRTM). Comparison between plasma- derived BPs and those produced with the new reference methodology was performed using 6 additional healthy control subjects. Reliability of the new methodology was performed on 4 test-retest studies of patients with Alzheimer's disease. RESULTS: The new algorithm selected reference voxels in gray matter tissue avoiding regions with specific binding located, in particular, in the venous and arterial circulation. Using the new reference, BP values obtained using a plasma input and a reference input were in excellent agreement and highly correlated (r = 0.811, P < 10(-5)) when calculated with RS-ESA and less so (r = 0.507, P < 0.005) when SRTM was used. In the production of parametric maps, SRTM was used with the new reference extraction, resulting in test-retest variability (10.6%; mean ICC = 0.878) that was superior to that obtained using the previous unsupervised clustering approach (mean ICC = 0.596). CONCLUSION: Reference region modeling combined with supervised reference tissue extraction produces a robust and reproducible quantitative assessment of [(11)C]-(R)-PK11195 studies in the human brain. 相似文献
8.
Comparison of the extracellular proteinase activity produced by a low-virulence mutant of Candida albicans and its wild-type parent. 总被引:2,自引:5,他引:2
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The production of extracellular proteinase by MY1049, a low-virulence mutant of Candida albicans, was compared with that of its wild-type parent, MY1044. Both strains were grown in a medium containing bovine serum albumin as a nitrogen source to induce proteinase production. Under these conditions, the proteinase activity per cell in the MY1049 cultures was the same as or higher than that of MY1044 cultures. However, MY1049 grew much more slowly than MY1044, and the total proteinase activity of the MY1049 culture remained well below that of the MY1044 culture. In a minimal medium with ammonium sulfate as the nitrogen source, MY1049 grew as rapidly as did MY1044. No significant differences were observed in the effects of inhibitors produced by MY1049 and MY1044. Our previous work indicated that MY1049 was able to grow and produce abundant mycelium in the renal calices of infected mice but that the strain was unable to invasively colonize the renal tissue. The decreased ability of MY1049 to grow in a protein-rich environment, despite its ability to produce extracellular proteinase, may enable the host to contain the mutant strain before the fungal cells invade the tissue. 相似文献
9.
Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability 总被引:1,自引:15,他引:1
La Spada AR; Peterson KR; Meadows SA; McClain ME; Jeng G; Chmelar RS; Haugen HA; Chen K; Singer MJ; Moore D; Trask BJ; Fischbeck KH; Clegg CH; McKnight GS 《Human molecular genetics》1998,7(6):959-967
X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG
repeat expansion in the first exon of the androgen receptor (AR) gene.
Disease-associated alleles (37-66 CAGs) change in length when transmitted
from parents to offspring, with a significantly greater tendency to shift
size when inherited paternally. As transgenic mice carrying human AR cDNAs
with 45 and 66 CAG repeats do not display repeat instability, we attempted
to model trinucleotide repeat instability by generating transgenic mice
with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions
in their genomic context. Studies of independent lines of AR YAC transgenic
mice with CAG 45 alleles reveal intergenerational instability at an overall
rate of approximately 10%. We also find that the 45 CAG repeat tracts are
significantly more unstable with maternal transmission and as the
transmitting mother ages. Of all the CAG/CTG repeat transgenic mice
produced to date the AR YAC CAG 45 mice are unstable with the smallest
trinucleotide repeat mutations, suggesting that the length threshold for
repeat instability in the mouse may be lowered by including the appropriate
flanking human DNA sequences. By sequence-tagged site content analysis and
long range mapping we determined that one unstable transgenic line has
integrated an approximately 70 kb segment of the AR locus due to
fragmentation of the AR YAC. Identification of the cis - acting elements
that permit CAG tract instability and the trans -acting factors that
modulate repeat instability in the AR YAC CAG 45 mice may provide insights
into the molecular basis of trinucleotide repeat instability in humans.
相似文献
10.