全文获取类型
收费全文 | 5496篇 |
免费 | 498篇 |
国内免费 | 45篇 |
学科分类
医药卫生 | 6039篇 |
出版年
2021年 | 71篇 |
2020年 | 42篇 |
2019年 | 82篇 |
2018年 | 89篇 |
2017年 | 70篇 |
2016年 | 62篇 |
2015年 | 99篇 |
2014年 | 116篇 |
2013年 | 190篇 |
2012年 | 250篇 |
2011年 | 234篇 |
2010年 | 154篇 |
2009年 | 128篇 |
2008年 | 227篇 |
2007年 | 231篇 |
2006年 | 221篇 |
2005年 | 201篇 |
2004年 | 219篇 |
2003年 | 176篇 |
2002年 | 181篇 |
2001年 | 199篇 |
2000年 | 166篇 |
1999年 | 167篇 |
1998年 | 78篇 |
1997年 | 68篇 |
1996年 | 42篇 |
1995年 | 56篇 |
1994年 | 63篇 |
1993年 | 56篇 |
1992年 | 122篇 |
1991年 | 128篇 |
1990年 | 120篇 |
1989年 | 125篇 |
1988年 | 123篇 |
1987年 | 113篇 |
1986年 | 85篇 |
1985年 | 101篇 |
1984年 | 69篇 |
1983年 | 71篇 |
1982年 | 48篇 |
1980年 | 47篇 |
1979年 | 91篇 |
1978年 | 73篇 |
1977年 | 50篇 |
1976年 | 61篇 |
1975年 | 68篇 |
1974年 | 57篇 |
1973年 | 53篇 |
1972年 | 63篇 |
1971年 | 44篇 |
排序方式: 共有6039条查询结果,搜索用时 781 毫秒
61.
N E Morton D Chiu C Holland P A Jacobs D Pettay 《American journal of medical genetics》1987,28(2):353-360
Reproductive histories and chromosomes of spontaneous abortions were studied by segregation analysis in 1890 sibships ascertained through a cytogenetically studied abortion. Normal karyotypes are associated with recurrent abortion. Among abnormal karyotypes, trisomy has an elevated recurrence risk even after adjustment through a liability indicator for maternal age. Possible mechanisms and conflicting evidence in the literature on trisomy are discussed. None of these differences in recurrence risk is large enough to play a significant numerical role in genetic counseling. 相似文献
62.
63.
p190RhoGAP can act to inhibit PDGF-induced gliomas in mice: a putative tumor suppressor encoded on human chromosome 19q13.3 下载免费PDF全文
Wolf RM Draghi N Liang X Dai C Uhrbom L Eklöf C Westermark B Holland EC Resh MD 《Genes & development》2003,17(4):476-487
p190RhoGAP and Rho are key regulators of oligodendrocyte differentiation. The gene encoding p190RhoGAP is located at 19q13.3 of the human chromosome, a locus that is deleted in 50%-80% of oligodendrogliomas. Here we provide evidence that p190RhoGAP may suppress gliomagenesis by inducing a differentiated glial phenotype. Using a cell culture model of autocrine loop PDGF stimulation, we show that reduced Rho activity via p190RhoGAP overexpression or Rho kinase inhibition induced cellular process extension, a block in proliferation, and reduced expression of the neural precursor marker nestin. In vivo infection of mice with retrovirus expressing PDGF and the p190 GAP domain caused a decreased incidence of oligodendrogliomas compared with that observed with PDGF alone. Independent experiments revealed that the retroviral vector insertion site in 3 of 50 PDGF-induced gliomas was within the p190RhoGAP gene. This evidence strongly suggests that p190 regulates critical components of PDGF oncogenesis and can act as a tumor suppressor in PDGF-induced gliomas by down-regulating Rho activity. 相似文献
64.
65.
A comparison of murine and human immunoproteomes of Helicobacter pylori validates the preclinical murine infection model for antigen screening 下载免费PDF全文
Bumann D Holland P Siejak F Koesling J Sabarth N Lamer S Zimny-Arndt U Jungblut PR Meyer TF 《Infection and immunity》2002,70(11):6494-6498
Preclinical mouse infection models are widely used for Helicobacter vaccine development, but how well such models mimic important aspects of human infections is unknown. A comparison of Helicobacter pylori immunoproteomes of infected mice with previously reported patient data reveals a high agreement in the antigens recognized, suggesting that H. pylori in vivo protein composition and recognition by the host immune system are comparable in mice and humans. Murine Helicobacter models may thus be valid to screen antigens for human vaccination. 相似文献
66.
A novel and versatile instrument for producing high quality monochrome and colour hard-copy of medical images from an array of digital information is described. Images are produced on standard photographic print paper mounted on the bed of a conventional X-Y plotter by scanning a time-modulated light source over the paper using a computer driven raster. A matrix board gives control of both greyscale and colour attribution. Examples of NMR images produced by the system are presented. A refinement of the technique which allows two variables to be displayed on one image is also described. 相似文献
67.
Effects of tampon materials on the in-vitro physiology of a toxic shock syndrome strain of Staphylococcus aureus 总被引:2,自引:0,他引:2
Seven materials used in the manufacture of tampons-four rayon, one modified rayon, one cotton and one carboxy-methyl cellulose (a modified cotton)-were compared for their effects in vitro on the physiology of a strain of Staphylococcus aureus isolated from a patient with Toxic Shock Syndrome. Experiments were performed in broth culture and, with the exception of two rayon samples, all of the materials tested reduced growth rate and cell yield compared with control values. Exocellular acid phosphatase, lipase, proteinase, hyaluronate lyase and haemolysin in culture filtrates were measured and the lethality of filtrates was determined in mice. The tampon materials had different effects on the levels of exocellular products. Cotton and carboxy-methyl cellulose cotton materials reduced the levels of all of the activities tested. The activities of the other enzymes were reduced or increased, depending on which material was present. All materials reduced both haemolytic activity and lethality of the culture filtrates. The in-vitro data suggest an extremely complex interaction between tampon materials and S. aureus. 相似文献
68.
Liu XH Kirschenbaum A Yao S Stearns ME Holland JF Claffey K Levine AC 《Clinical & experimental metastasis》1999,17(8):687-694
Upregulation of vascular endothelial growth factor (VEGF) expression induced by hypoxia is crucial event leading to neovascularization.
Cyclooxygenase-2, an inducible enzyme that catalyzes the formation of prostaglandins (PGs) from arachidonic acid, has been
demonstrated to be induced by hypoxia and play role in angiogenesis and metastasis. To investigate the potential effect of
COX-2 on hypoxia-induced VEGF expression in prostate cancer. We examined the relationship between COX-2 expression and VEGF
induction in response to cobalt chloride (CoCl2)-simulated hypoxia in three human prostate cancer cell lines with differing biological phenotypes. Northern blotting and
ELISA revealed that all three tested cell lines constitutively expressed VEGF mRNA, and secreted VEGF protein to different
degrees (LNCaP > PC-3 > PC3ML). However, these cell lines differed in the ability to produce VEGF in the presence of CoCl2-simulated hypoxia. CoCl2 treatment resulted in 40% and 75% increases in VEGF mRNA, and 50% and 95% in protein secretion by LNCaP and PC-3 cell lines,
respectively. In contrast, PC-3ML cell line, a PC-3 subline with highly invasive, metastatic phenotype, exhibits a dramatic
upregulation of VEGF, 5.6-fold in mRNA and 6.3-fold in protein secretion after treatment with CoCl2. The upregulation of VEGF in PC-3ML cells is accompanied by a persistent induction of COX-2 mRNA (6.5-fold) and protein (5-fold).
Whereas COX-2 expression is only transiently induced in PC-3 cells and not affected by CoCl2 in LNCaP cells. Moreover, the increases in VEGF mRNA and protein secretion induced by CoCl2 in PC-3ML cells were significantly suppressed following exposure to NS398, a selective COX-2 inhibitor. Finally, the effect
of COX-2 inhibition on CoCl2-induced VEGF production was reversed by the treatment with exogenous PGE2. Our data demonstrate that VEGF induction by cobalt chloride-simulated hypoxia is maintained by a concomitant, persistent
induction of COX-2 expression and sustained elevation of PGE2 synthesis in a human metastatic prostate cancer cell line, and suggest that COX-2 activity, reflected by PGE2 production, is involved in hypoxia-induced VEGF expression, and thus, modulates prostatic tumor angiogenesis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
69.
Lymphocyte proliferative responses to chlamydial antigens in human chlamydial eye infections. 总被引:3,自引:0,他引:3 下载免费PDF全文
D C Mabey M J Holland N D Viswalingam B T Goh S Estreich A Macfarlane H M Dockrell J D Treharne 《Clinical and experimental immunology》1991,86(1):37-42
In order to study the relationship between cell-mediated immune responses to Chlamydia trachomatis and the pathogenesis of human chlamydial eye disease, we have measured the peripheral blood lymphocyte proliferative responses to whole chlamydial elementary bodies in 40 subjects with oculogenital chlamydial infection of varying severity, 13 subjects with genital chlamydial infections and 12 healthy seronegative controls. The mean stimulation index was significantly higher in those with oculogenital infections than in controls. There was a strong correlation between the response to C. trachomatis serotypes B and L1. We studied the relationship between proliferative responses and four clinical parameters: follicular conjunctivitis, papillary hypertrophy, corneal pannus and epithelial punctate keratitis, but were unable to show a significant association with any of these. Nor was there any association between proliferative response and serum antibody titre to C. trachomatis (pooled serotypes D-K), duration of disease or quantitative isolation of chlamydia from the conjunctiva. The depletion of CD8+ cells had no consistent effect on proliferative responses to serotype L1 in 13 subjects. 相似文献
70.
Rats with a neurotoxic lesion of the amygdala central nucleus (CN) in one hemisphere and a 192 immunoglobulin G (192IgG)-saporin lesion of cholinergic neurons in the contralateral substantia innominata/nucleus basalis (SI/nBM) failed to show the enhanced attentional processing of a conditioned stimulus (CS) observed in sham-operated rats when that CS's predictive value was altered. Performance of these asymmetrically lesioned rats was poorer than that of rats with a unilateral lesion of either structure or with a symmetrical lesion of both structures in the same hemisphere. These results implicate connections between the CN and SI/nBM in the incremental attentional processing of CSs, extending previous research that has shown similar effects of bilateral lesions of either the CN or the SI/nBM. 相似文献