全文获取类型
收费全文 | 769篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 3篇 |
妇产科学 | 4篇 |
基础医学 | 96篇 |
口腔科学 | 17篇 |
临床医学 | 31篇 |
内科学 | 79篇 |
皮肤病学 | 1篇 |
神经病学 | 22篇 |
特种医学 | 26篇 |
外国民族医学 | 1篇 |
外科学 | 131篇 |
综合类 | 2篇 |
预防医学 | 21篇 |
眼科学 | 323篇 |
药学 | 19篇 |
肿瘤学 | 10篇 |
出版年
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 5篇 |
2016年 | 19篇 |
2015年 | 14篇 |
2014年 | 20篇 |
2013年 | 21篇 |
2012年 | 29篇 |
2011年 | 50篇 |
2010年 | 32篇 |
2009年 | 19篇 |
2008年 | 50篇 |
2007年 | 44篇 |
2006年 | 47篇 |
2005年 | 41篇 |
2004年 | 20篇 |
2003年 | 34篇 |
2002年 | 25篇 |
2001年 | 25篇 |
2000年 | 29篇 |
1999年 | 24篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 4篇 |
1981年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1975年 | 6篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1968年 | 5篇 |
1966年 | 5篇 |
1965年 | 4篇 |
1954年 | 5篇 |
排序方式: 共有799条查询结果,搜索用时 0 毫秒
11.
Ganglioneuromas are rare, benign, well-differentiated, slowgrowing tumors of the sympathetic nervous system, composed of large, mature neurons in a stroma composed of Schwann cells. Ganglioneuromas are derived from the neural crest cells and can arise anywhere from the base of the skull to the pelvis. The pre-sacral area is a very rare location for ganglioneuromas to develop. We describe the case of a 31 year old woman, who was incidentally found to have an abnormal pre-sacral mass. The following work-up, revealed the mass to be growing on imagery (computed tomography and magnetic resonance imagery) and fluorine-18 fluorodeoxiglucose avid. The mass was removed by assisted laparoscopy and was found to be a benign ganglioneuroma. This is the first described case of fluorine-18 fluorodeoxiglucose avid, pre-sacral, benign ganglioneuroma. 相似文献
12.
Holz F. Carrillo G. G. Núñez Peña E. G. Martinez Martinez A. A. Rivera de la Peña Jiménez I. G. Virgen Ramon Bonilla Verhoff M. A. Birngruber Christoph G. 《International journal of legal medicine》2022,136(4):1199-1199
International Journal of Legal Medicine - 相似文献
13.
14.
15.
This is a retrospective chart review of perinatal outcomes of all primiparas over the age of 24 delivering at Maternity Center Associates, an out-of-hospital birth center, from January 1985 through May 1988 (N = 228). Chi-square analysis was used to determine whether mature primiparas, aged 35 to 43 (n = 27), had significantly more adverse outcomes than younger primiparas, aged 25 to 34 (n = 201). There was a significant difference between the groups in rate of transfer to hospital; however, there were no significant differences in rate of cesarean section, infant birth weight, apgar scores, and length of second stage labor. Implications for practice and future study are examined. 相似文献
16.
The activity of ketoconazole and other azoles against Trypanosoma cruzi: biochemistry and chemotherapeutic action in vitro 总被引:4,自引:0,他引:4
L J Goad R L Berens J J Marr D H Beach G G Holz 《Molecular and biochemical parasitology》1989,32(2-3):179-189
Trypanosoma cruzi epimastigotes in culture medium, and amastigotes and trypomastigotes in cultured human diploid lung cells were exposed to the antimycotic agent ketoconazole and their growth and/or sterol biosynthesis observed. Propagation of epimastigotes and amastigotes was impaired by concentrations of ketoconazole achievable in human serum, and amastigotes were more sensitive than were epimastigotes. Epimastigotes and trypomastigotes (non-dividing stage) displayed changes in their membrane sterol content such that the amounts of normal, end-product sterols (ergosterol, ergosta-5,7-dien-3 beta-ol, 24-ethylcholesta-5,7,22-trien-3 beta-ol, 24-ethylcholesta-5,7-dien-3 beta-ol) were notably decreased and the amounts of 14 alpha-methyl sterol precursors of these sterols (24-methylenedihydrolanosterol, obtusifoliol, lanosterol) were increased. Other azole drugs, itraconazole and fluconazole, when tested on epimastigotes, evoked the same qualitative pattern of changes in free sterols. Itraconazole was nearly as potent as ketoconazole, but fluconazole was significantly less potent. The nature of the sterols found in T. cruzi and the actions of azole drugs on their biosynthesis were similar in many respects to those observed in fungi and in Leishmania species. By analogy, it would seem that the primary mechanism of action of azole drugs on T. cruzi life-cycle stages is the impairment of the cytochrome P-450 sterol 14 alpha-demethylase. The consequent loss of normal sterols and accumulation of 14 alpha-methyl sterols may be responsible for the coincident retardation or cessation of growth. 相似文献
17.
Neutral sphingomyelinase (SMPD3) deficiency causes a novel form of chondrodysplasia and dwarfism that is rescued by Col2A1-driven smpd3 transgene expression 下载免费PDF全文
Stoffel W Jenke B Holz B Binczek E Günter RH Knifka J Koebke J Niehoff A 《The American journal of pathology》2007,171(1):153-161
Neutral sphingomyelinase SMPD3 (nSMase2), a sphingomyelin phosphodiesterase, resides in the Golgi apparatus and is ubiquitously expressed. Gene ablation of smpd3 causes a generalized prolongation of the cell cycle that leads to late embryonic and juvenile hypoplasia because of the SMPD3 deficiency in hypothalamic neurosecretory neurons. We show here that this novel form of combined pituitary hormone deficiency is characterized by the perturbation of the hypothalamus-pituitary growth axis, associated with retarded chondrocyte development and enchondral ossification in the epiphyseal growth plate. To study the contribution by combined pituitary hormone deficiency and by the local SMPD3 deficiency in the epiphyseal growth plate to the skeletal phenotype, we introduced the full-length smpd3 cDNA transgene under the control of the chondrocyte-specific promoter Col2a1. A complete rescue of the smpd3(-/-) mouse from severe short-limbed skeletal dysplasia was achieved. The smpd3(-/-) mouse shares its dwarf and chondrodysplasia phenotype with the most common form of human achondrodysplasia, linked to the fibroblast-growth-factor receptor 3 locus, not linked to deficits in the hypothalamic-pituitary epiphyseal growth plate axis. The rescue of smpd3 in vivo has implications for future research into dwarfism and, particularly, growth and development of the skeletal system and for current screening and future treatment of combined dwarfism and chondrodysplasia. 相似文献
18.
Tissue engineered retinal pigment epithelial (RPE) transplantation is a promising cell-based therapy for age-related macular degeneration. The aim of this work is to develop a supportive scaffold with a favorable topography to aid functional RPE monolayer maintenance while being tolerated underneath the retina. To this end, films and electrospun substrates with fiber diameters ranging from 200 to 1000 nm were made of polyethylene terephthalate or poly(l-lactide-co-ε-caprolactone), and then tested using human fetal RPE cells in vitro and transplanted subretinally in rabbits. The results indicated that RPE on both 200 nm fiber variants showed the highest cell densities, adherent monolayers achieved deeper pigmentation, and more uniform hexagonal tight junctions. Facile subretinal implantation of flat 200 nm fiber membranes was achieved by electrospinning them onto a porous rigid-elastic carrier. Spectral-domain optical coherence tomography showed a reattached, slightly thinned retina overlying the implants over 2 weeks observation. Histology demonstrated native RPE variably migrated onto the nanofibers, and a reactive gliosis with some photoreceptor degeneration. In conclusion, scaffolds with 200 nm fiber topography enhanced RPE culture, showed subretinal biocompatibility, and should thus be considered for future cell-based therapies in blinding retinal diseases. 相似文献
19.
EEG Correlates of Action Observation in Humans 总被引:1,自引:0,他引:1
To investigate electrophysiological correlates of action observation electroencephalogram (EEG) was recorded while participants
observed repetitive biological (human) or non-biological movements (at a rate of 2 Hz). Steady-state evoked potentials were
analyzed and their neural sources were investigated using low resolution electromagnetic tomography analysis (LORETA). Results
revealed significantly higher activation in the primary motor and premotor cortex, supplementary motor area as well as the
posterior parietal cortices during observation of biological movements, supporting mirror properties of cortical motor neurons.
In addition interregional communication was analyzed. Increased coherence for distributed networks at delta (0.5–4 Hz) and
lower alpha (8–10 Hz) frequencies were obtained suggesting integration and functional coupling between the activated cortical
regions during human action observation. 相似文献
20.
Substitution of amino acids Asp-85, Asp-212, and Arg-82 in bacteriorhodopsin affects the proton release phase of the pump and the pK of the Schiff base. 总被引:17,自引:15,他引:17 下载免费PDF全文
H Otto T Marti M Holz T Mogi L J Stern F Engel H G Khorana M P Heyn 《Proceedings of the National Academy of Sciences of the United States of America》1990,87(3):1018-1022
Photocycle and flash-induced proton release and uptake were investigated for bacteriorhodopsin mutants in which Asp-85 was replaced by Ala, Asn, or Glu; Asp-212 was replaced by Asn or Glu; Asp-115 was replaced by Ala, Asn, or Glu; Asp-96 was replaced by Ala, Asn, or Glu; and Arg-82 was replaced by Ala or Gln in dimyristoylphosphatidylcholine/3-[(3-cholamidopropyl)dimethylammonio]-1- propanesulfonate micelles at pH 7.3. In the Asp-85----Ala and Asp-85----Asn mutants, the absence of the charged carboxyl group leads to a blue chromophore at 600 and 595 nm, respectively, and lowers the pK of the Schiff base deprotonation to 8.2 and 7, respectively, suggesting a role for Asp-85 as counterion to the Schiff base. The early part of the photocycles of the Asp-85----Ala and Asp-85----Asn mutants is strongly perturbed; the formation of a weak M-like intermediate is slowed down about 100-fold over wild type. In both mutants, proton release is also slower but clearly precedes the rise of M. The amplitude of the early (less than 0.2 microseconds) reversed photovoltage component in the Asp-85----Asn mutant is very large, and the net charge displacement is close to zero, indicating proton release and uptake on the cytoplasmic side of the membrane. The data suggest an obligatory role for Asp-85 in the efficient deprotonation of the Schiff base and in the proton release phase, probably as proton acceptor. In the Asp-212----Asn mutant, the rise of the absorbance change at 410 nm is slowed down to 220 microsecond, its amplitude is small, and the release of protons is delayed to 1.9 ms. The absorbance changes at 650 nm indicate perturbations in the early time range with a slow K intermediate. Thus Asp-212 also participates in the early events of charge translocation and deprotonation of the Schiff base. In the Arg-82----Gln mutant, no net transient proton release was observed, whereas, in the Arg-82----Ala mutant, uptake and release were reversed. The pK shift of the purple-to-blue transition in the Asp-85----Glu, Arg-82----Ala, and Arg-82----Gln mutants and the similarity in the photocycle and photoelectrical signals of the Asp-85----Ala, Asp-85----Asn, and Asp-212----Asn mutants suggest the interaction between Asp-85, Arg-82, Asp-212, and the Schiff base as essential for proton release. 相似文献