全文获取类型
收费全文 | 471篇 |
免费 | 37篇 |
国内免费 | 12篇 |
专业分类
儿科学 | 41篇 |
妇产科学 | 7篇 |
基础医学 | 49篇 |
口腔科学 | 12篇 |
临床医学 | 46篇 |
内科学 | 131篇 |
皮肤病学 | 7篇 |
神经病学 | 9篇 |
特种医学 | 74篇 |
外科学 | 50篇 |
综合类 | 17篇 |
预防医学 | 16篇 |
眼科学 | 1篇 |
药学 | 39篇 |
肿瘤学 | 21篇 |
出版年
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 16篇 |
2012年 | 21篇 |
2011年 | 9篇 |
2010年 | 22篇 |
2009年 | 17篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 16篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 15篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 20篇 |
1998年 | 30篇 |
1997年 | 21篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有520条查询结果,搜索用时 140 毫秒
1.
2.
3.
4.
5.
Evaluation of three substitutes for Percoll in sperm isolation by density gradient centrifugation 总被引:9,自引:4,他引:9
Silane-coated silica particle solutions (ISolate(TM) and PureSperm)TM)) and
iodixanol (OptiPrep(TM)) were compared to polyvinylpyrrolidone (PVP)-coated
silica particles (Percoll(TM)) in their efficacy to recover spermatozoa by
gradient centrifugation for use in assisted reproductive procedures.
Efficacy was assessed in terms of percentages of sperm recovery, sperm
vitality and motility, normal sperm morphology and normal sperm chromatin
condensation. No significant difference was found in the recovery of
spermatozoa for men with both normal sperm counts and oligozoospermia,
between PVP-coated and silane-coated particle solutions. Iodixanol had
significantly lower sperm recovery compared to the other products. Sperm
vitality, progressive motility, normal morphology and normal chromatin
condensation did not differ significantly between any of the sperm
isolation products.
相似文献
6.
Mutation spectrum and genotype-phenotype analyses in Cowden disease and Bannayan-Zonana syndrome, two hamartoma syndromes with germline PTEN mutation 总被引:22,自引:1,他引:22
Marsh DJ; Coulon V; Lunetta KL; Rocca-Serra P; Dahia PL; Zheng Z; Liaw D; Caron S; Duboue B; Lin AY; Richardson AL; Bonnetblanc JM; Bressieux JM; Cabarrot-Moreau A; Chompret A; Demange L; Eeles RA; Yahanda AM; Fearon ER; Fricker JP; Gorlin RJ; Hodgson SV; Huson S; Lacombe D; Eng C 《Human molecular genetics》1998,7(3):507-515
The tumour suppressor gene PTEN , which maps to 10q23.3 and encodes a 403
amino acid dual specificity phosphatase (protein tyrosine phosphatase;
PTPase), was shown recently to play a broad role in human malignancy.
Somatic PTEN deletions and mutations were observed in sporadic breast,
brain, prostate and kidney cancer cell lines and in several primary tumours
such as endometrial carcinomas, malignant melanoma and thyroid tumours. In
addition, PTEN was identified as the susceptibility gene for two hamartoma
syndromes: Cowden disease (CD; MIM 158350) and Bannayan-Zonana (BZS) or
Ruvalcaba-Riley-Smith syndrome (MIM 153480). Constitutive DNA from 37 CD
families and seven BZS families was screened for germline PTEN mutations.
PTEN mutations were identified in 30 of 37 (81%) CD families, including
missense and nonsense point mutations, deletions, insertions, a
deletion/insertion and splice site mutations. These mutations were
scattered over the entire length of PTEN , with the exception of the first,
fourth and last exons. A 'hot spot' for PTEN mutation in CD was identified
in exon 5 that contains the PTPase core motif, with 13 of 30 (43%) CD
mutations identified in this exon. Seven of 30 (23%) were within the core
motif, the majority (five of seven) of which were missense mutations,
possibly pointing to the functional significance of this region. Germline
PTEN mutations were identified in four of seven (57%) BZS families studied.
Interestingly, none of these mutations was observed in the PTPase core
motif. It is also worthy of note that a single nonsense point mutation,
R233X, was observed in the germline DNA from two unrelated CD families and
one BZS family. Genotype-phenotype studies were not performed on this small
group of BZS families. However, genotype-phenotype analysis inthe group of
CD families revealed two possible associations worthy of follow-up in
independent analyses. The first was an association noted in the group of CD
families with breast disease. A correlation was observed between the
presence/absence of a PTEN mutation and the type of breast involvement
(unaffected versus benign versus malignant). Specifically and more
directly, an association was also observed between the presence of a PTEN
mutation and malignant breast disease. Secondly, there appeared to be an
interdependent association between mutations upstream and within the PTPase
core motif, the core motif containing the majority of missense mutations,
and the involvement of all major organ systems (central nervous system,
thyroid, breast, skin and gastrointestinal tract). However, these
observations would need to be confirmed by studying a larger number of CD
families.
相似文献
7.
One unambiguous message that comes from the data obtained relates to the central role played by the hinge region, and its constituent disulfide bonds, in the functioning of the IgG molecule. Segmental flexibility allows variation in the distance between the antibody combining sites, located at the distal ends of the Fab regions, and serves the important function of allowing bivalent attachment of antibodies to antigenic determinants even if the latter form a fixed array, for example, on a cell surface (monogomous bivalency). Too much flexibility, however, seen as a consequence of cleaving the hinge-region disulfides appears to be inimicable to the expression of effector functions. The hinge region and its disulfides control the degree of flexibility, thus allowing the IgG molecule to perform its varied functions. 相似文献
8.
Balanos GM Talbot NP Robbins PA Dorrington KL 《Pflügers Archiv : European journal of physiology》2005,450(6):372-380
In healthy humans, changes in cardiac output are commonly accommodated with minimal change in pulmonary artery pressure. Conversely, exposure to hypoxia is associated with substantial increases in pulmonary artery pressure. In this study we used non-invasive measurement of an index of pulmonary artery pressure, the maximum systolic pressure difference across the tricuspid valve (Pmax), to examine the pulmonary vascular response to changes in blood flow during both air breathing and hypoxia. We used Doppler echocardiography in 33 resting healthy humans breathing air over 6–24 h to measure spontaneous diurnal variations in Pmax and cardiac output. Cardiac output varied by up to ~2.5 l/min; Pmax varied little with cardiac output [0.61±0.74 (SD) mmHg min l–1]. Eight of the volunteers were also exposed to eucapnic hypoxia (end-tidal
) for 8 h. In this group Pmax rose progressively from 21 mmHg to 37 mmHg over 8 h. By comparing diurnal variations in Pmax during air breathing with changes in Pmax during hypoxia in the same eight individuals, we concluded that only approximately 5% of the changes in Pmax during hypoxia could be attributed to concurrent changes in cardiac output. The low sensitivity of Pmax to changes in cardiac output makes it a useful index of hypoxic pulmonary vasoconstriction in healthy humans. 相似文献
9.
We report our clinical experience with phototherapy in 3802 infants; 3629 were exposed to "standard" daylight phototherapy and 173 to "high-intensity" blue-light phototherapy. High-intensity blue-light phototherapy was twice as effective as standard daylight phototherapy in decreasing bilirubin concentrations. No failures occurred with high-intensity phototherapy compared with an overall failure rate of 1.84/1000 with daylight lamps; these cases were transferred to high-intensity phototherapy with prompt response. Rebound after cessation of phototherapy was greater in those exposed to high-intensity blue light with a significantly greater number requiring a second exposure. However, the incidence was still low. No third exposure was required in any infant. Nursing of infants under high-intensity blue light was more difficult and inconvenient as was clinical monitoring. The light also caused more stress on the nursing and medical personnel. However, the infants tolerated both types of phototherapy equally well. High-intensity blue-light phototherapy would seem to be the treatment of choice for infants with rapidly increasing or very high bilirubin levels, as well as in those not responding adequately to daylight phototherapy. 相似文献
10.
Abstract: We report the first case of fatal anthrax meningoencephalitis in Hong Kong over the past 60 years. A 13 year-old boy presented with right lower quadrant pain, diarrhoea and progressive headache. Lumbar puncture yielded gram positive bacilli initially thought to be Bacillus cereus, a contaminant. He was treated with ampicillin and cefotaxime, but died 3 days after hospitalization. The organism isolated from blood and cerebrospinal fluid was later identified as Bacillus anthracis. 相似文献