全文获取类型
收费全文 | 608篇 |
免费 | 38篇 |
国内免费 | 15篇 |
专业分类
儿科学 | 19篇 |
妇产科学 | 2篇 |
基础医学 | 103篇 |
口腔科学 | 5篇 |
临床医学 | 35篇 |
内科学 | 60篇 |
皮肤病学 | 222篇 |
神经病学 | 15篇 |
特种医学 | 107篇 |
外科学 | 19篇 |
综合类 | 15篇 |
预防医学 | 18篇 |
眼科学 | 6篇 |
药学 | 22篇 |
肿瘤学 | 13篇 |
出版年
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 18篇 |
2012年 | 12篇 |
2011年 | 18篇 |
2010年 | 22篇 |
2009年 | 23篇 |
2008年 | 17篇 |
2007年 | 26篇 |
2006年 | 26篇 |
2005年 | 28篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 16篇 |
2001年 | 15篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 28篇 |
1997年 | 20篇 |
1996年 | 26篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 23篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1940年 | 4篇 |
1937年 | 7篇 |
1935年 | 5篇 |
1934年 | 6篇 |
1932年 | 5篇 |
1931年 | 8篇 |
1928年 | 7篇 |
1927年 | 4篇 |
排序方式: 共有661条查询结果,搜索用时 15 毫秒
1.
2.
A new range of stand magnifiers has been released by the COIL company in the United Kingdom. Examination of these magnifiers reveals that they fail to deliver the rated magnifications labelled prominently on the appliances, as a result of the manufacturer's conformance with the requirements of the German DIN standard and the use of back vertex power (F'v) rather than equivalent dioptric power (Fm) of the magnifier. In this study we provide information on the optometric parameters of these new stand magnifiers that will assist the more accurate specification of improvements in vision expected from their use. 相似文献
3.
Pheochromocytoma and paraganglioma: comparison of MR imaging with CT and I-131 MIBG scintigraphy 总被引:6,自引:0,他引:6
To ascertain the magnetic resonance (MR) imaging characteristics of pheochromocytomas and paragangliomas and to compare MR with computed tomography (CT) and iodine-131 metaiodobenzylguanidine (I-131 MIBG), 19 patients (18 with pheochromocytomas, one with a paraganglioma) were studied. The 18 patients with pheochromocytomas had had positive findings with I-131 MIBG scintigraphy. Abdominal pheochromocytomas were generally hypointense compared with normal liver on T1-weighted MR images and extremely hyperintense on T2-weighted MR images. MR imaging was preferable to CT in the evaluation of primary pheochromocytomas due to superior tissue characterization, particularly in the patient with hypertension and borderline catecholamine levels. For patients with recurrent or metastatic disease, the data suggest that I-131 MIBG scintigraphy is the examination of choice. 相似文献
4.
5.
6.
7.
Chaperonin-mediated assembly of wild-type and mutant subunits of human propionyl-CoA carboxylase expressed in Escherichia coli 总被引:1,自引:0,他引:1
We developed a bacterial expression system for the human alpha and beta
cDNAs of propionyl-CoA carboxylase (PCC). These cDNAs (less the putative
mitochondrial matrix targeting presequences) were co-expressed in
Escherichia coli on one plasmid vector with each cDNA having its own
IPTG-inducible promoter. Only negligible amounts of active PCC were
measured despite the presence of both alpha and beta subunits as indicated
by Western blot analysis and the almost complete biotinylation of the alpha
subunit. Co-expression of this plasmid with a second plasmid vector
over-expressing the E. coli chaperonin proteins, groES and groEL, resulted
in a several hundred-fold increase in PCC specific activity, to a level
comparable with that found in crude human liver extracts. PCC was partially
purified on monomeric avidin affinity resin and the presence of both alpha
and beta subunits was demonstrated, thereby confirming the assembly of both
subunits into an active enzyme. Deficiency of either alpha PCC or beta PCC
results in propionic acidemia, an autosomal recessive disorder. We used
this expression system to characterize one missense mutation previously
described in five Japanese alleles, namely C1283T (Thr428lle) in beta PCC.
This mutation, when expressed in E.coli under the same conditions as that
of wild-type PCC, had null activity, despite the presence of assembled
alpha PCC and beta PCC subunits. This bacterial expression system can be
useful for analysis of either alpha PCC or beta PCC mutations. Our findings
indicated that the groES and groEL chaperonin proteins were essential for
folding and assembly of the human PCC heteromeric subunits.
相似文献
8.
Pal L; Leykin L; Schifren JL; Isaacson KB; Chang YC; Nikruil N; Chen Z; Toth TL 《Human reproduction (Oxford, England)》1998,13(7):1837-1840
A case series of eight cycles of in-vitro fertilization (IVF) in five women
diagnosed with malignant disorders is presented. These patients chose to
defer definitive treatment for a chance for preservation of potential
fertility. The response of these patients to ovarian stimulation, and the
outcome, was compared with 17 IVF cycles in 12 age- matched patients with
isolated tubal infertility. An apparent adverse influence of malignant
disease on the quality and behaviour of oocytes was observed. Despite a
comparable total number of oocytes per cycle in the two groups, a
significantly reduced percentage of mature oocytes was retrieved per cycle
from patients with malignant diseases. The oocytes from patients with
malignant disorders were of a poorer quality and exhibited a significantly
impaired fertilization rate compared to the controls. We propose that
neoplastic processes, irrespective of the site or cell of origin, may have
a detrimental impact on the biology of oocytes, an effect akin to that seen
on spermatozoa in men with certain malignancies.
相似文献
9.
10.
Confirmation of the association between high levels of immunoglobulin E food sensitization and eczema in infancy: an international study 总被引:1,自引:0,他引:1
D. J. Hill C. S. Hosking F. M. de Benedictis A. P. Oranje T. L. Diepgen V. Bauchau the EPAAC Study Group 《Clinical and experimental allergy》2008,38(1):161-168
Background Studies of Australian infants have reported that more than 80% of those with moderate atopic eczema (AE) have high levels of IgE food sensitization (IgE‐FS) that are commonly associated with IgE food allergy. Objectives To explore the relationship between high levels of IgE‐FS and AE in a large cohort of young children with eczema participating in a multi‐centre, international study. Methods Two thousand one hundred and eighty‐four subjects (mean age 17.6 months, range 11.8–25.4; 1246 males) with active eczema from atopic families from 94 centres in 12 countries were studied. Clinical history, Scoring Atopic Dermatitis index as a measure of eczema severity and CAP‐FEIA measurements for total IgE and IgE antibody levels to cow milk, egg and peanut were entered into a database. If CAP‐FEIA levels exceeded previously reported age‐specific cut‐off levels for 95% positive predictive values (PPVs) for food allergy, subjects were defined as having high‐risk IgE‐FS (HR‐IgE‐FS). Results Serum was available from 2048 patients; 55.5% were atopic. The frequency of HR‐IgE‐FS to milk, egg and/or peanut was the greatest in patients whose eczema developed in the first 3 months of life and the least in those whose eczema developed after 12 months (P<0.0001). In a regression analysis to allow for potential confounding factors, children with HR‐IgE‐FS had the most severe eczema and the youngest age of onset (P<0.001); 64% of infants with severe eczema of onset‐age <3 months had HR‐IgE‐FS. Conclusion Early‐onset severe eczema in infancy was associated with HR‐IgE‐FS. Clinical implications Food allergies should be routinely assessed in infants with moderate or severe eczema. Capsule summary In eczematous infants, the earlier the age of onset, and the greater the severity of eczema, the greater the frequency of associated high levels of IgE‐FS. 相似文献