全文获取类型
收费全文 | 2113篇 |
免费 | 113篇 |
国内免费 | 76篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 172篇 |
妇产科学 | 26篇 |
基础医学 | 229篇 |
口腔科学 | 58篇 |
临床医学 | 255篇 |
内科学 | 504篇 |
皮肤病学 | 105篇 |
神经病学 | 63篇 |
特种医学 | 392篇 |
外科学 | 136篇 |
综合类 | 45篇 |
预防医学 | 87篇 |
眼科学 | 19篇 |
药学 | 86篇 |
2篇 | |
肿瘤学 | 108篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 33篇 |
2017年 | 26篇 |
2016年 | 24篇 |
2015年 | 39篇 |
2014年 | 50篇 |
2013年 | 59篇 |
2012年 | 41篇 |
2011年 | 47篇 |
2010年 | 92篇 |
2009年 | 86篇 |
2008年 | 56篇 |
2007年 | 97篇 |
2006年 | 64篇 |
2005年 | 65篇 |
2004年 | 33篇 |
2003年 | 23篇 |
2002年 | 32篇 |
2001年 | 36篇 |
2000年 | 28篇 |
1999年 | 32篇 |
1998年 | 129篇 |
1997年 | 156篇 |
1996年 | 135篇 |
1995年 | 109篇 |
1994年 | 114篇 |
1993年 | 98篇 |
1992年 | 28篇 |
1991年 | 36篇 |
1990年 | 36篇 |
1989年 | 55篇 |
1988年 | 47篇 |
1987年 | 42篇 |
1986年 | 49篇 |
1985年 | 45篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 24篇 |
1981年 | 31篇 |
1980年 | 26篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 20篇 |
1976年 | 26篇 |
1975年 | 14篇 |
1964年 | 1篇 |
排序方式: 共有2302条查询结果,搜索用时 15 毫秒
991.
First trimester maternal serum concentrations of fetal antigen 2 in normal pregnancies and those affected by trisomy 21 总被引:1,自引:0,他引:1
Price KM; Van Lith JM; Silman R; Mantingh A; Grudzinskas JG 《Human reproduction (Oxford, England)》1998,13(6):1706-1708
Serum concentrations of fetal antigen 2 (FA-2), the amino-propeptide of the
alpha1 chain of collagen type I, were measured in peripheral blood from
women with normal (n = 234) and trisomy 21 affected (n = 14) pregnancies
between 9 and 11 weeks gestation. Serum FA-2 concentrations were seen to be
stable throughout this period, and though raised FA-2 concentrations were
seen at the 10th week of gestation, a statistically significant difference
between normal and trisomy 21 affected pregnancies was not found overall.
Therefore it seems unlikely that FA- 2 has a role in first trimester
screening for trisomy 21, despite the fact that significantly higher FA-2
concentrations in trisomy 21 and significantly lower concentrations in
trisomy 18 had been previously demonstrated in amniotic fluid in the second
trimester.
相似文献
992.
Skeletal muscle is an attractive target for somatic gene transfer of both
acquired and inherited disorders. Direct injection of adenoviral vectors in
the skeletal muscle leads to recombinant gene expression in a large number
of muscle fibers. Transgene expression has been transient in most organs
and associated with substantial inflammation when experiments are performed
in adult immune competent mice. In this report, we utilize a variety of in
vivo and in vitro models of T and B cell function to characterize the
nature of the immune response to adenoviral vectors injected into murine
skeletal muscle. Cellular immunity dependent on CD4+ and CD8+ T cells
contributes to the loss of recombinant gene expression and the development
of localized inflammation. Antigen specific activation of T cells occurs to
both viral proteins and the reporter gene beta-galactosidase. Systemic
levels of neutralizing antibody to the capsid proteins of the vector are
also generated. Destructive immune responses responsible for loss of
transgene expression are largely directed against beta-galactosidase in
that transgene expression was stable when beta-galactosidase was eliminated
as a neoantigen in mice transgenic for lacZ. A strategy to prevent the
cellular and humoral immunity to this therapy was developed based on
transiently ablating CD4+ T cell activation at the time of vector delivery.
Encouraging results were obtained when vector was administered with one of
several immune modulating agents including cyclophosphamide, mAb to CD4+
cells, and mAb to CD40 ligand. These studies indicate that cellular and
humoral immune responses are elicited in the context of gene therapy
directed to skeletal muscle with adenoviral vectors. Transient ablation of
CD4+ T cell activation prevents the effects responses of the CD8+ T and B
cells.
相似文献
993.
Non-disjunction of chromosome 18 总被引:3,自引:2,他引:3
Bugge M; Collins A; Petersen MB; Fisher J; Brandt C; Hertz JM; Tranebjaerg L; de Lozier-Blanchet C; Nicolaides P; Brondum-Nielsen K; Morton N; Mikkelsen M 《Human molecular genetics》1998,7(4):661-669
A sample of 100 trisomy 18 conceptuses analysed separately and together
with a published sample of 61 conceptuses confirms that an error in
maternal meiosis II (MII) is the most frequent cause of non-disjunction for
chromosome 18. This is unlike all other human trisomies that have been
studied, which show a higher frequency in maternal meiosis I (MI). Maternal
MI trisomy 18 shows a low frequency of recombination in proximal p and
medial q, but not the reduction in proximal q observed in chromosome 21 MI
non-disjunction. Maternal MII non-disjunction does not fit the entanglement
model that predicts increased recombination, especially near the
centromere. Whereas recent data on MII trisomy 21 show the predicted
increase in recombination proximally, maternal MII trisomy 18 has
non-significantly reduced recombination. Therefore, chromosome-specific
factors must complicate the simple model of susceptible chiasma
distributions interacting with age-dependent deterioration of the meiotic
mechanism. For chromosome 18, 30% of tetrads are nullichiasmate in maternal
MI non-disjunction, but nullichiasmates are not observed in maternal MII
non-disjunction. Chiasma distributions from normal chromosome 18 meioses
provide no evidence for normal disjunction from nullichiasmate tetrads. We
extend this study to examine the remaining autosomes and find no evidence
for normal disjunction from nullichiasmate tetrads generally.
相似文献
994.
Andresen BS; Bross P; Udvari S; Kirk J; Gray G; Kmoch S; Chamoles N; Knudsen I; Winter V; Wilcken B; Yokota I; Hart K; Packman S; Harpey JP; Saudubray JM; Hale DE; Bolund L; Kolvraa S; Gregersen N 《Human molecular genetics》1997,6(5):695-707
Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most commonly
recognized defect of mitochondrial beta-oxidation. It is potentially fatal,
but shows a wide clinical spectrum. The aim of the present study was to
investigate whether any correlation exists between MCAD genotype and
disease phenotype. We determined the prevalence of the 14 known and seven
previously unknown non-G985 mutations in 52 families with MCAD deficiency
not caused by homozygosity for the prevalent G985 mutation. This showed
that none of the non-G985 mutations are prevalent, and led to the
identification of both disease- causing mutations in 14 families in whom
both mutations had not previously been reported. We then evaluated the
severity of the mutations identified in these 14 families. Using expression
of mutant MCAD in Escherichia coli with or without co-overexpression of the
molecular chaperonins GroESL we showed that five of the missense mutations
affect the folding and/or stability of the protein, and that the residual
enzyme activity of some of them could be modulated to a different extent
depending on the amounts of available chaperonins. Thus, some of the
missense mutations may result in relatively high levels of residual enzyme
activity, whereas the mutations leading to premature stop codons will
result in no residual enzyme activity. By correlating the observed types of
mutations identified to the clinical/biochemical data in the 14 patients in
whom we identified both disease-causing mutations, we show that a
genotype/phenotype correlation in MCAD deficiency is not straightforward.
Different mutations may contribute with different susceptibilities for
disease precipitation, when the patient is subjected to metabolic stress,
but other genetic and environmental factors may play an equally important
role.
相似文献
995.
Sonohysterographic evaluation of uterine abnormalities noted on hysterosalpingography 总被引:2,自引:2,他引:2
Transvaginal sonohysterography was performed on 40 consecutive patients
with infertility or recurrent pregnancy loss and uterine abnormalities on
hysterosalpingography. The findings were correlated with the
hysterosalpingogram and subsequent diagnostic and/or operative
hysteroscopy. Hysterosalpingography was incorrect in nine cases.
Sonohysterography was more accurate than hysterosalpingography and provided
more information about uterine abnormalities. Sonohysterography was in
complete agreement with hysteroscopy. Diagnostic hysteroscopy can therefore
be avoided if the sonohysterogram is normal. Sonohysterography also
provides additional information on the relative proportion of the
intracavitary and intramyometrial components of submucus myomas, as well as
extracavitary myomas and the adnexae. This may help in planning the
surgical procedure.
相似文献
996.
997.
Huug J van Duijn Marijke M Kuyvenhoven Franois G Schellevis Theo JM Verheij 《The British journal of general practice》2007,57(540):561-568
BACKGROUND: Although the vast majority of respiratory tract symptoms are self-limiting, many patients visit their GP for these symptoms and antibiotics are over-prescribed. AIM: To explore determinants of patients visiting GPs for recent cough, sore throat, or earache; for being prescribed antibiotics; and for patients' satisfaction with visiting the GP. Design of the study: Second Dutch National Survey of General Practice (DNSGP-2) with a health interview and an additional questionnaire. SETTING: A total of 7057 adult patients of 163 GPs in the Netherlands. METHOD: Characteristics of patients and GPs as well as morbidity data were derived from the DNSGP-2 and a health interview. Characteristics of the symptoms, GPs' management and patients' satisfaction were measured by an additional written questionnaire. Data were analysed by means of multivariate logistic regression. RESULTS: About 40% of the responders (n = 1083) reported cough, sore throat, or earache in the 2 weeks preceding the interview and, of them, 250 visited their GP. Of this latter group, 97 patients were prescribed antibiotics. Apart from non-medical reasons, relevant medical factors played an important role in deciding to visit the GP. Smokers and patients with cardiac disease or diabetes mellitus were not especially inclined to see their GP. Smoking behaviour, fever, and views on respiratory tract symptoms and antibiotics of patients and GPs were associated with being prescribed antibiotics. Patients' perception of having been carefully examined was associated with their satisfaction, while receiving antibiotics was not. CONCLUSION: GPs should inform patients with clear elevated risk when to visit their GP in cases of cough, sore throat, or earache. There is still a need for GPs and patients to be better informed about the limited significance of single inflammation signs (for example, fever and green phlegm) as an indication for antibiotics. Careful examination of the patient contributes to patient satisfaction. 相似文献
998.
G Birou JM Garcier M Guillot G Vanneuville J Chazal 《Surgical and radiologic anatomy : SRA》1991,13(4):307-311
Summary The authors have studied the relationship between anatomic and CT sections of the lateral pterygoid muscle in 39 anatomic specimens. Good superimposition of the images was found, which seems important in neoplastic invasion of the infratemporal fossa and which may lead to a pathogenic interpretation of the algo-dysfunctional syndrome of the masticatory apparatus.
Etude anatomo-radiologique (TDM) du muscle ptérygoïdien latéral
Résumé Les auteurs ont étudié, sur 39 pièces anatomiques, la corrélation entre coupes anatomiques et tomodensitométriques (TDM) du muscle ptérygoïdien latéral. Il apparaît une bonne superposition des images ce qui semble intéressant dans les envahissements de la fosse infratemporale en carcinologie et qui pourrait déboucher sur une interprétation pathogénique du syndrome algo dysfonctionnel de l'appareil manducateur.相似文献
999.
X-Q Mao T. Shirakawa M. Kawai T. Enomoto S. Sasaki Y. Dake H. Kitano A. Hagihara JM Hopkin K. Morimoto 《Clinical genetics》1998,53(1):54-56
The β subunit of high affinity immunoglobulin E (IgE) receptor (FcɛRIβ) and the Clara cell derived inflammatory molecule, CC16 have been cited as candidate genes for atopic asthma on chromosome 11q13. A genetic association study was performed with an intragenic microsatellite repeat of CC16 gene on chromosome 11q12–13 in relation to atopic and non-atopic asthma. Whereas variants of FcɛRIβ at chromosome 11q13 show association with atopy and asthma, no significant association was found between asthma and CC16 genotypes irrespective of atopic status. These data support the candidacy of FcɛRIβ rather than CC16 for the atopic asthma locus on chromosome 11q. 相似文献
1000.
Microsatellite instability and mutation analysis of hMSH2 and hMLH1 in patients with sporadic, familial and hereditary colorectal cancer 总被引:17,自引:0,他引:17
Moslein G; Tester DJ; Lindor NM; Honchel R; Cunningham JM; French AJ; Halling KC; Schwab M; Goretzki P; Thibodeau SN 《Human molecular genetics》1996,5(9):1245-1252
To date, at least four genes involved in DNA mismatch repair, hMSH2, hMLH1,
hPMS1 and hPMS2, have been demonstrated to be altered in the germline of
patients with hereditary nonpolyposis colorectal cancer (HNPCC).
Additionally, defective mismatch repair is thought to account for the
observation of microsatellite instability (MIN) in tumors from these
patients. The genetic defect responsible for the MIN+ phenotype in sporadic
colorectal cancer, however, has yet to be clearly delineated. In order to
better understand the role of somatic and germline alterations within hMSH2
and hMLH1 in the process of colorectal tumorigenesis, we examined the
entire coding regions of both of these genes in seven patients with MIN+
sporadic colorectal cancer, 19 patients with familial colorectal cancer,
and 20 patients meeting the strict Amsterdam criteria for HNPCC. Thirteen
germline, two somatic, and four neutral alterations were identified. The
two somatic mutations occurred in patients having familial cancer, while
the germline mutations were distributed among one sporadic (14%), three
familial (16%), and nine HNPCC (45%) cases. All patients with identified
mutations in the mismatch repair genes, whose tumors were available for
analysis, demonstrated MIN. On the other hand, we could not identify
mutations in the subset of clinically defined HNPCC patients with MIN
negative tumors nor in the majority (6/7) of MIN+ sporadic tumors.
相似文献