全文获取类型
收费全文 | 2207篇 |
免费 | 133篇 |
国内免费 | 128篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 48篇 |
妇产科学 | 46篇 |
基础医学 | 292篇 |
口腔科学 | 20篇 |
临床医学 | 274篇 |
内科学 | 443篇 |
皮肤病学 | 52篇 |
神经病学 | 99篇 |
特种医学 | 187篇 |
外科学 | 413篇 |
综合类 | 86篇 |
预防医学 | 181篇 |
眼科学 | 78篇 |
药学 | 142篇 |
中国医学 | 11篇 |
肿瘤学 | 87篇 |
出版年
2023年 | 10篇 |
2022年 | 9篇 |
2021年 | 35篇 |
2020年 | 25篇 |
2019年 | 40篇 |
2018年 | 48篇 |
2017年 | 34篇 |
2016年 | 36篇 |
2015年 | 53篇 |
2014年 | 74篇 |
2013年 | 130篇 |
2012年 | 142篇 |
2011年 | 159篇 |
2010年 | 89篇 |
2009年 | 90篇 |
2008年 | 113篇 |
2007年 | 171篇 |
2006年 | 109篇 |
2005年 | 113篇 |
2004年 | 99篇 |
2003年 | 84篇 |
2002年 | 88篇 |
2001年 | 59篇 |
2000年 | 52篇 |
1999年 | 53篇 |
1998年 | 52篇 |
1997年 | 50篇 |
1996年 | 42篇 |
1995年 | 34篇 |
1994年 | 38篇 |
1993年 | 26篇 |
1992年 | 21篇 |
1991年 | 30篇 |
1990年 | 30篇 |
1989年 | 33篇 |
1988年 | 32篇 |
1987年 | 25篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1971年 | 8篇 |
1958年 | 14篇 |
排序方式: 共有2468条查询结果,搜索用时 31 毫秒
21.
22.
The shufflon of Salmonella enterica serovar Typhi regulates type IVB pilus-mediated bacterial self-association
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)
Previously, it was shown that type IVB pili encoded by the Salmonella enterica serovar Typhi pil operon are used to facilitate bacterial entry into human intestinal epithelial cells in vitro and that such entry is inhibited by purified prepilin (pre-PilS) protein (X.-L. Zhang, I. S. M. Tsui, C. M. C. Yip, A. W. Y. Fung, D. K.-H. Wong, X. Dai, Y. Yang, J. Hackett, and C. Morris, Infect. Immun. 68:3067-3073, 2000). The pil operon concludes with a simple shufflon, and a recombinase gene product (Rci) inverts DNA in the C-terminal region of the pilV gene to allow synthesis of two distinct PilV proteins, PilV1 and PilV2, which are presumptive minor pilus proteins. We show here that the type IVB pili mediate bacterial self-association, but only when the PilV1 and PilV2 proteins are not expressed. This may be achieved in wild-type serovar Typhi by rapid DNA inversion activity of the shufflon. We show that the inversion activity inhibits the expression of genes inserted between the 19-bp inverted repeats used for Rci-mediated recombination and that the activity of Rci increases when DNA is supercoiled. The data suggest that serovar Typhi self-associates under conditions (such as low oxygen tension in the gut) that favor DNA supercoiling. These results explain (i) the function of the serovar Typhi shufflon and (ii) why there are only two possible shufflon states, in contrast to the many possible states of other shufflon systems. The data further indicate that a very early step in serovar Typhi pathogenesis may be type IVB pilus-mediated self-association of bacteria in the anaerobic human small intestine prior to invasion of the human gut epithelium. The suggested type IVB pilus-dependent step in typhoid fever pathogenesis may partially explain the enhanced invasiveness of serovar Typhi for humans. 相似文献
23.
Fugger EF; Black SH; Keyvanfar K; Schulman JD 《Human reproduction (Oxford, England)》1998,13(9):2367-2370
The world's first deliveries of normal babies after use of flow cytometric
separated human sperm cells (MicroSort) for preconception gender selection
are reported. Offspring were of the desired female gender in 92.9% of the
pregnancies. Most of these pregnancies and births were achieved after
simple intrauterine insemination.
相似文献
24.
Human and mouse IgM can be polymerized as a hexamer in addition to a pentamer. Our previous work with mouse IgM measured activation of guinea pig complement by highly enriched preparations of hexamer and pentamer and showed that hexamer is >100-fold more active than pentamer. In this report pentamer and hexamer were compared for their capacity to activate complement in a homogeneic system, i.e. chimeric mouse V/human Cmu IgM pentamer and hexamer were assayed separately for their capacity to activate human (and guinea pig) complement. In both the homogeneic and the xenogeneic systems hexamer was more active than pentamer, but the magnitude of the difference between hexamer and pentamer depended on the complement source. Whereas chimeric hexamer activated guinea pig complement >100-fold more efficiently than did chimeric pentamer, this hexamer was only 4-13-fold more active than pentamer when assayed with human complement. Similarly, mouse hexamer, which was >100-fold more active than mouse pentamer with guinea pig complement, was only approximately 2-fold more active than mouse pentamer with human complement. Mouse hexameric and pentameric IgM were each approximately 20-fold more active with human complement than were the corresponding chimeric isoforms of IgM. 相似文献
25.
Chun Hsing Liao Yu Tsung Huang Fang Yeh Chu Tsui Hsien Lin Po Ren Hsueh 《Journal of microbiology, immunology, and infection》2008,41(4):355-357
Time to positivity is an available parameter in automated blood culture systems. We report a patient with persistent methicillin-resistant Staphylococcus aureus bacteremia who received various regimens for treatment of methicillin-resistant S. aureus, and demonstrate that monitoring of the time to positive blood culture might be helpful in the early recognition of treatment failure. 相似文献
26.
Incomplete rescue of cystic fibrosis transmembrane conductance regulator deficient mice by the human CFTR cDNA 总被引:2,自引:2,他引:2
Rozmahel R; Gyomorey K; Plyte S; Nguyen V; Wilschanski M; Durie P; Bear CE; Tsui LC 《Human molecular genetics》1997,6(7):1153-1162
We have used a mouse model to study the ability of human CFTR to correct
the defect in mice deficient of the endogenous protein. In this model,
expression of the endogenous Cftr gene was disrupted and replaced with a
human CFTR cDNA by a gene targeted 'knock-in' event. Animals homozygous for
the gene replacement failed to show neither improved intestinal pathology
nor survival when compared to mice completely lacking CFTR. RNA analyses
showed that the human CFTR sequence was transcribed from the targeted
allele in the respiratory and intestinal epithelial cells. Furthermore, in
vivo potential difference measurements showed that basal CFTR chloride
channel activity was present in the apical membranes of both nasal and
rectal epithelial cells in all homozygous knock-in animals examined. Ussing
chamber studies showed, however, that the cAMP-mediated chloride channel
function was impaired in the intestinal tract among the majority of
homozygous knock-in animals. Hence, failure to correct the intestinal
pathology associated with loss of endogenous CFTR was related to
inefficient functional expression of the human protein in mice. These
results emphasize the need to understand the tissue- specific expression
and regulation of CFTR function when animal models are used in gene therapy
studies.
相似文献
27.
Mahadevaiah SK; Odorisio T; Elliott DJ; Rattigan A; Szot M; Laval SH; Washburn LL; McCarrey JR; Cattanach BM; Lovell-Badge R; Burgoyne PS 《Human molecular genetics》1998,7(4):715-727
An RNA-binding motif (RBM) gene family has been identified on the human Y
chromosome that maps to the same deletion interval as the 'azoospermia
factor' (AZF). We have identified the homologous gene family (Rbm) on the
mouse Y with a view to investigating the proposal that this gene family
plays a role in spermatogenesis. At least 25 and probably >50 copies of
Rbm are present on the mouse Y chromosome short arm located between Sry and
the centromere. As in the human, a role in spermatogenesis is indicated by
a germ cell-specific pattern of expression in the testis, but there are
distinct differences in the pattern of expression between the two species.
Mice carrying the deletion Yd1, that maps to the proximal Y short arm, are
female due to a position effect resulting in non-expression of Sry ;
sex-reversing such mice with an Sry transgene produces males with a high
incidence of abnormal sperm, making this the third deletion interval on the
mouse Y that affects some aspect of spermatogenesis. Most of the copies of
Rbm map to this deletion interval, and the Yd1males have markedly reduced
Rbm expression, suggesting that RBM deficiency may be responsible for, or
contribute to, the abnormal sperm development. In man, deletion of the
functional copies of RBM is associated with meiotic arrest rather than
sperm anomalies; however, the different effects of deletion are consistent
with the differences in expression between the two species.
相似文献
28.
AIMS: Studies are disclosing that Epstein-Barr virus (EBV) is involved in the aetiology of various neoplasms including undifferentiated carcinomas of the aerodigestive tract. The aetiology of intrahepatic cholangiocarcinoma (ICC), a malignant neoplasm arising from intrahepatic biliary epithelia, has yet to be fully evaluated. To date, two cases of EBV-related ICC have been reported, and they presented foci of lymphoepitheliomatous undifferentiated carcinoma components. METHODS AND RESULTS: To determine whether EBV is commonly involved in the developments of ICC, we performed in-situ hybridization and immunohistochemistry for EBV in 215 cases of ICC in Japan, using a probe against EBV-coded nuclear RNA (EBER) and a specific antibody against latent membrane protein-1 (LMP-1), respectively. We did not detect EBV-infected carcinoma cells in any of the ICC cases examined. No lymphoepitheliomatous undifferentiated carcinoma components were found either. CONCLUSION: The results suggest that EBV infection is unlikely to be involved in the pathogenesis of ICC. 相似文献
29.
Serological, chemical, and structural analyses of the Escherichia coli cross-reactive capsular polysaccharides K13, K20, and K23. 总被引:2,自引:1,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)
W F Vann T Soderstrom W Egan F P Tsui R Schneerson I Orskov F Orskov 《Infection and immunity》1983,39(2):623-629
The Escherichia coli K13, K20, and K23 capsular polysaccharide antigens are serologically related. All of these polysaccharides contain ribose and 2-keto-3-deoxyoctonate in equimolar quantities. The K13 and K20 polysaccharides are partially O-acetylated. A comparison of these polysaccharides after O-deacetylation, by nuclear magnetic resonance and permethylation analysis, showed that these polysaccharides contained the disaccharide repeat unit leads to)-beta-ribofuranosyl-(1 leads to 7)-beta-2-keto-3-deoxyoctonate. They differed in the presence and location of an acetyl moiety. The K13 polysaccharide was O-acetylated at C-4 of the 2-keto-3-deoxyoctonate. The K20 antigen was O-acetylated at C-5 of the ribose moiety. The K23 polymer was nonacetylated. The cross-reactivity of these antigens was demonstrated by tandem-crossed immunoelectrophoresis. Antibodies to K23 could be completely absorbed from OK K23 serum by K13, K20, and K23 antigenic extracts. The K13 and K20 antibodies could be completely absorbed from their respective antisera only by homologous antigenic extracts. Monoclonal antibodies were prepared against a protein conjugate of the K13 polysaccharide. Analyses of the reactions of these antibodies with the three polysaccharides suggest that the K13 polysaccharide has at least three antigenic sites, one of which is common to the K13, K20, and K23 polysaccharides. 相似文献
30.
BACKGROUND: There has thus far been no empirical research on the occurrence of antenatal psychiatric morbidity in Chinese population. Epidemiological studies in western societies generally show that depressive episodes occur in 10-20% of pregnant women. Longitudinal studies have demonstrated that antenatal depression is one of the most powerful predictors of postnatal depression. There is also a growing literature that shows that antenatal psychological distress can adversely affect maternal and foetal well being. METHODS: At 38 weeks of pregnancy, 238 consecutive women were invited to return for psychiatric assessment. The participants were interviewed using the non-patient version of the Structured Clinical Interview for DSM-IV (SCID-NP). RESULTS: Seventy women (29%) declined to participate, and another 11 (5%) defaulted the SCID interview. Among the 157 women interviewed, the 1-month prevalence of antenatal depression was 4.4%. The 1-month prevalence of all psychiatric diagnoses was 6.4%. The prevalence of antenatal depression and all psychiatric diagnoses for the entire pregnancy was 6.4% and 8.3%, respectively. LIMITATIONS: About a third of eligible subjects did not participate in the study. CONCLUSIONS: A significant proportion of Chinese women suffer from psychiatric morbidity during pregnancy. Depressive disorders are by far the commonest morbidity in the study population. Given the scope of the morbidity and the potential impact on obstetric and neonatal outcomes, early screening and treatment are warranted. 相似文献