全文获取类型
收费全文 | 5865篇 |
免费 | 517篇 |
国内免费 | 48篇 |
专业分类
耳鼻咽喉 | 48篇 |
儿科学 | 196篇 |
妇产科学 | 110篇 |
基础医学 | 794篇 |
口腔科学 | 111篇 |
临床医学 | 689篇 |
内科学 | 972篇 |
皮肤病学 | 132篇 |
神经病学 | 339篇 |
特种医学 | 504篇 |
外科学 | 828篇 |
综合类 | 313篇 |
一般理论 | 3篇 |
预防医学 | 467篇 |
眼科学 | 145篇 |
药学 | 485篇 |
2篇 | |
中国医学 | 35篇 |
肿瘤学 | 257篇 |
出版年
2022年 | 52篇 |
2021年 | 87篇 |
2020年 | 59篇 |
2019年 | 65篇 |
2018年 | 94篇 |
2017年 | 74篇 |
2016年 | 66篇 |
2015年 | 108篇 |
2014年 | 141篇 |
2013年 | 197篇 |
2012年 | 270篇 |
2011年 | 277篇 |
2010年 | 207篇 |
2009年 | 206篇 |
2008年 | 231篇 |
2007年 | 257篇 |
2006年 | 228篇 |
2005年 | 195篇 |
2004年 | 209篇 |
2003年 | 184篇 |
2002年 | 173篇 |
2001年 | 166篇 |
2000年 | 143篇 |
1999年 | 138篇 |
1998年 | 153篇 |
1997年 | 114篇 |
1996年 | 104篇 |
1995年 | 108篇 |
1994年 | 76篇 |
1993年 | 80篇 |
1992年 | 108篇 |
1991年 | 107篇 |
1990年 | 100篇 |
1989年 | 103篇 |
1988年 | 127篇 |
1987年 | 127篇 |
1986年 | 105篇 |
1985年 | 85篇 |
1984年 | 74篇 |
1983年 | 74篇 |
1982年 | 45篇 |
1981年 | 41篇 |
1979年 | 59篇 |
1978年 | 51篇 |
1977年 | 43篇 |
1975年 | 36篇 |
1972年 | 54篇 |
1971年 | 42篇 |
1955年 | 42篇 |
1954年 | 35篇 |
排序方式: 共有6430条查询结果,搜索用时 0 毫秒
71.
72.
B lymphocytes secreting IgG linked to latent transforming growth factor- beta prevent primary cytolytic T lymphocyte responses 总被引:3,自引:0,他引:3
B lymphocytes secreting IgG linked to latent transforming growth factor
(TGF)-beta (IgG-TGF-beta) prevent cytolytic T lymphocyte (CTL) responses to
unrelated antigens in mixed lymphocyte cultures (MLC) so long as resting
resident macrophages and functional Fc receptors are present. This was
shown using IgG-secreting plaque-forming cells (PFC) to sheep erythrocytes
(SRBC) obtained from popliteal lymph nodes of mice injected repeatedly in
foot pads with SRBC. Remarkably, as few as approximately 300 PFC prevented
CTL responses of 5 x 10(5) normal syngeneic spleen cells in MLC.
Supranatants of short-term cultures of PFC also prevented CTL responses,
and suppression was prevented by eliminating or dissociating IgG and
TGF-beta present in supranatants or by antibody against active TGF-beta.
Furthermore, the latency- associated peptide of latent TGF-beta was
detected in approximately 10% of foci of IgG captured from single PFC,
indicating that at least some B lymphocytes secrete IgG-TGF-beta as a
complex. Resting resident macrophages (which do not produce latent
TGF-beta) and functional Fc receptors were required for suppression,
consistent with idea that IgG- TGF-beta is taken up through Fc receptors
for IgG and that active TGF- beta, cleaved from latent TGF-beta of the
complex, is delivered directly to potentially responding CTL. If CTL
responses in man are similarly regulated by B lymphocytes, then an ongoing
B cell response in patients with chronic viral infections or bearing
immunogenic cancers may prevent effective therapeutic vaccination.
相似文献
73.
74.
Sequence variation and size ranges of CAG repeats in the Machado-Joseph disease, spinocerebellar ataxia type 1 and androgen receptor genes 总被引:6,自引:0,他引:6
Rubinsztein David C.; Leggo Jayne; Coetzee Gerhard A.; Irvine Ryan A.; Buckley Michael; Ferguson-Smith Malcolm A. 《Human molecular genetics》1995,4(9):1585-1590
A subgroup of trinucleotide repeat diseases result from abnormalexpansions of CAG repeats which are translated into polyglutaminestretches. As yet there is little understanding of how the polyglutaminesfunction either normally, or when expanded. We have investigatedthese sequences in the Machado-Joseph disease, androgen receptorand spinocerebellar ataxia type 1 genes in humans and otherprimates. None of the 748 normal chromosomes that were examinedhad more than 34 uninterrupted gluta-mine codons in the Machado-Josephdisease gene. Similarly, no normal alleles with more than 39uninterrupted glutamine codons have been reported for the otherdisease genes associated with polyglutamine expansions. Sequenceanalyses of the repeats in primates revealed shorter polyglutaminestretches in some of the non-human primates at all three lociand marked diversions from the expected polyglutamines in theorang-utan Machado-Joseph gene and in the marmoset spinocerebellarataxia type 1 gene. These data suggest that conservation ofthese polyglutamine stretches may not always be necessary fornormal gene function. 相似文献
75.
Murphy M Mabruk MJ Lenane P Liew A McCann P Buckley A O Flatharta C Hevey D Billet P Robertson W Javed S Leader M Kay E Murphy GM 《Journal of clinical pathology》2002,55(11):829-833
AIM: Ultraviolet light (UV) is known to cause DNA damage in the epidermis. The damaged DNA is repaired or deleted by apoptosis to prevent the generation of cancer. It has been suggested that a deficient apoptotic mechanism may predispose individuals to skin cancer. Therefore, the response of normal controls and patients with basal cell carcinoma (BCC) to UV irradiation was investigated. METHODS: The buttock skin from normal volunteers and patients with BCC was irradiated using solar simulated radiation (SSR). SSR mimics the effect of natural sunlight. Skin biopsies were excised and examined for p53, p21, and Bax protein expression and for the induction of apoptosis. RESULTS: At 33 hours after UV irradiation, the induction of apoptosis was significantly higher (p = 0.04) in patients with BCC than in normal volunteers (Mann Whitney test). A trend towards higher p21 expression was found at 33 hours in patients with BCC (mean, 18.69 positive cells/field) than in normal volunteers (mean, 9.89), although this difference was not significant (p = 0.05 positive cells/field). CONCLUSION: These results may imply that patients with BCC have enhanced sensitivity to UV irradiation or that there is some defect in the cell arrest or repair pathways, which results in damaged cells been pushed into apoptosis rather than repair. 相似文献
76.
An oral killed polyvalent bacterial vaccine was assessed in a double-blind trial involving healthy volunteers. Three courses of oral vaccine were given over a 2-month period; each course contained 10(10) Haemophilus influenzae and 7 X 10(9) Staphylococcus aureus organisms. Immunity was assessed by monitoring antibody in saliva and serum over a 3-month period. No evidence of a nonspecific effect on immune parameters (immunoglobulin levels and Escherichia coli antibody) was detected in saliva or serum. An increase in H. influenzae antibody in saliva was detected in 55% of subjects receiving the vaccine compared with 6.7% of the placebo group. Antibody was associated with immunoglobulin A (IgA), IgG, and IgM, but the greatest increases over preimmunization levels were detected in the IgA class. No increase in serum antibody levels was detected. Subjects with higher preimmunization levels of salivary antibody to H. influenzae were less likely to respond to the oral bacterial vaccine. No increase in S. aureus antibody was detected in saliva or serum. 相似文献
77.
Purification of actin from Candida albicans and comparison with the Candida 48,000-Mr protein.
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)
Actin was purified from Candida albicans cells by affinity chromatography by DNase-Sepharose and was recognized by immunoblotting with monoclonal antibody directed against chick muscle actin. The C. albicans 48-kilodalton protein recognized by sera from patients with invasive candidiasis was shown by DEAE chromatography and immunoblotting not to be identical with the purified C. albicans actin. 相似文献
78.
Studies of the serum level of IgD in patients with tuberculosis and sarcoidosis reveal evidence of a difference in humoral immunity. Radial diffusion measurements were done of IgD in serums from fifty patients with active tuberculosis, fifty-three patients with sarcoidosis and 103 age, race and sex matched healthy controls. IgD was detected in serums from 20% more tuberculosis patients (P<0·0250) and 20·7% fewer sarcoidosis patients than respective controls (P<0·0005). Multivariate statistical analysis of loge transformed IgD serum levels revealed significantly lower geometric mean IgD levels in sarcoidosis patients (P=0·0018). The age dependence of serum IgD was highly significant (P<0·0001). Age dependent disease effects were detected. High levels of IgD occurred predominantly in older tuberculosis patients while depression of IgD occurred in middle-aged sarcoidosis patients. It is suggested that the elevated levels of serum IgM in patients with sarcoidosis may represent a compensatory change associated with low levels of serum IgD. 相似文献
79.
AIMS: To study the regulation of type 1 insulin like growth factor receptor (IGF-1R) tyrosine kinase activity using the fission yeast Schizosaccharomyces pombe and a green fluorescent protein (GFP) tagged, full length IGF-1R. METHODS: The beta chain of the IGF-1R (betawt) was expressed under inducible conditions in the fission yeast S. pombe. Western blot analysis with antiphosphotyrosine antibodies was used to assess the kinase activity of betawt. A GFP tagged IGF-1R (GFP-IGF-1R) was constructed to study the tyrosine kinase activity of the full length IGF-1R. The signalling capabilities of GFP-IGF-1R in response to IGF-1 stimulation were investigated in transiently transfected fibroblasts. Immunofluorescent staining for cellular phosphotyrosine content was used to assess the localisation and tyrosine kinase activity of GFP-IGF-1R. RESULTS: The betawt protein displayed functional tyrosine kinase activity in S pombe and phosphorylated endogenous yeast proteins. In response to IGF-1 stimulation, the GFP-IGF-1R became autophosphorylated and also activated the phosphatidylinositol 3-kinase and mitogen activated protein kinase pathways. Tyrosine phosphorylation and kinase activity of the GFP-IGF-1R could be visualised by immunofluorescence with antiphosphotyrosine antibodies. Coexpression of a mammalian tyrosine phosphatase PTP1B with betawt completely inhibited this tyrosine kinase activity in yeast and also reduced the tyrosine phosphorylation in COS cells transfected with the GFP-IGF-1R. CONCLUSIONS: Schizosaccharomyces pombe can be used to analyse the tyrosine kinase activity of the IGF-1R beta chain and its regulation by tyrosine phosphatases. In addition, the regulation of IGF-1R tyrosine kinase activity can be studied using a GFP tagged IGF-1R. Using both of these methods, IGF-1R kinase activity was shown to be inhibited by the protein tyrosine phosphatase, PTP1B. 相似文献
80.