全文获取类型
收费全文 | 8795篇 |
免费 | 956篇 |
国内免费 | 19篇 |
专业分类
耳鼻咽喉 | 77篇 |
儿科学 | 298篇 |
妇产科学 | 187篇 |
基础医学 | 1220篇 |
口腔科学 | 280篇 |
临床医学 | 982篇 |
内科学 | 1670篇 |
皮肤病学 | 107篇 |
神经病学 | 889篇 |
特种医学 | 308篇 |
外科学 | 1190篇 |
综合类 | 323篇 |
一般理论 | 7篇 |
预防医学 | 993篇 |
眼科学 | 285篇 |
药学 | 531篇 |
中国医学 | 4篇 |
肿瘤学 | 419篇 |
出版年
2021年 | 136篇 |
2020年 | 111篇 |
2019年 | 152篇 |
2018年 | 157篇 |
2017年 | 136篇 |
2016年 | 115篇 |
2015年 | 137篇 |
2014年 | 194篇 |
2013年 | 339篇 |
2012年 | 393篇 |
2011年 | 418篇 |
2010年 | 241篇 |
2009年 | 221篇 |
2008年 | 364篇 |
2007年 | 381篇 |
2006年 | 390篇 |
2005年 | 365篇 |
2004年 | 356篇 |
2003年 | 281篇 |
2002年 | 309篇 |
2001年 | 283篇 |
2000年 | 279篇 |
1999年 | 260篇 |
1998年 | 111篇 |
1997年 | 100篇 |
1996年 | 100篇 |
1995年 | 95篇 |
1994年 | 83篇 |
1993年 | 84篇 |
1992年 | 210篇 |
1991年 | 186篇 |
1990年 | 208篇 |
1989年 | 214篇 |
1988年 | 195篇 |
1987年 | 160篇 |
1986年 | 158篇 |
1985年 | 169篇 |
1984年 | 117篇 |
1983年 | 110篇 |
1982年 | 79篇 |
1981年 | 64篇 |
1979年 | 118篇 |
1978年 | 96篇 |
1977年 | 80篇 |
1976年 | 66篇 |
1975年 | 61篇 |
1974年 | 72篇 |
1973年 | 96篇 |
1972年 | 88篇 |
1971年 | 76篇 |
排序方式: 共有9770条查询结果,搜索用时 0 毫秒
21.
E. B. Austin F. Thistlethwaite S. Neeson P. Stern L. McDonald M. Hulston D. Gilham E. Elkord R. Griffiths R. Guest J. D. M. Campbell R. E. Hawkins 《Transfusion medicine (Oxford, England)》2006,16(Z1):8-8
The CXCL12/CXCR4 chemokine axis is a well characterized and important chemotactic stimulus/receptor unit that orchestrates the homing and migration of cells to the bone marrow and to ischemic tissues following tissue damage. Here, we demonstrate that the sialomucin, CD164, a regulator of haemopoietic precursor cell adhesion to stroma and entry of primitive CD34+CD38lo/‐ precursor cells into cycle, modulates the migration of CD133+ cord blood cells to CXCL12 by associating with the CXCR4 receptor. This was demonstrated by a reduction in CD133+ cell migration on fibronectin to CXCL12 (i) by engaging the functional class II glycosylation‐dependent epitope on CD164 with the 103B2/9E10 class II but not the N6B6 class III antibody; and (ii) by RNAi knockdown of CD164 protein levels in CD133+ cells. The inhibition of migration was more pronounced in the more primitive CD34+CD38lo/‐ cell subset. Similar studies using the Jurkat cell line confirmed these findings and led to further analyses using alternative chemokines. A direct association between CXCR4 and CD164 was demonstrated by the co‐localisation of CD164 with CXCR4 and VLA‐4 and VLA‐5 at the leading edge of CD133+ cells when CXCL12 was presented on fibronectin. This was further supported by immunoprecipitation studies that demonstrate in the absence of CXCL12, CXCR4 is associated only with VLA‐4 and VLA‐5 but on exposure to CXCL12, CD164 is rapidly recruited to the CXCR4 complex. Knock‐down of CD164 using siRNA revealed that signalling through CXCR4 via PKC‐ζ was significantly dampened. Our findings therefore support a novel association between three distinct families of cell surface receptors that regulate both cell migratory and proliferative responses and identify a CD164 as a key regulator of the CXCL12/CXCR4 axis. 相似文献
22.
D. McDonald H. Deavall P. Moss† J. Steele† J. Thompson V. Turner 《Transfusion medicine (Oxford, England)》2006,16(S1):52-52
Over 20 years ago, the Birmingham Blood Centre established a facility for the cryopreservation of bone marrow (BM) for patients in the West Midlands suffering from haematopoietic disorders and for whom a bone marrow transplant was indicated. Today, the use of mobilised peripheral blood (PBSC) has overtaken bone marrow as the source of stem cells for transplantation and the numbers of patients benefitting and the diversity of conditions being treated has increased enormously. Allogeneic transplants, using stem cells from healthy donors, have become increasingly successful as a result of an improving understanding of the complexities of the HLA histocompatibility system. Additionally umbilical cord blood (HUC), which in the 1980s was recognised as a source of stem cells, can now be collected and used for transplantation. As scientific knowledge and the clinical management of patients has advanced, so too have laboratory methods for manipulating cell products to enrich or deplete certain cell populations (e.g. by CD34+cell selection) in order to minimise potentially fatal graft-versus-host disease (GVHD) or to eliminate tumour cells in the case of autologous patients. Donor lymphocytes (DLI) may also be collected and used to aid a graft-versus-leukaemia (GVL) effect. The laboratory is currently developing protocols for immunotherapy using virus-specific T cells which can be prepared and infused to combat potentially fatal CMV disease post-transplant. Clinical trials of vaccines employing tumour specific dendritic cells for treating patients with hepatocellular carcinoma (HCC) and metastatic melanoma (MM), which do not respond to conventional treatments, are also underway. The advances and expansion in the Stem Cell and Immunotherapy (SCI) service in Birmingham over the last 10 year period are reflected in the table below:
23.
J.M. Smith D. Stablein A. Singh W. Harmon R.A. McDonald 《American journal of transplantation》2006,6(3):585-588
Graft thrombosis is the most common cause of first year graft failure in pediatric renal transplantation. The North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) database was analyzed for cases of graft failure due to thrombosis among patients transplanted from 1998 to 2004. The impact of interleukin-2 (IL-2) receptor antagonists as induction therapy was determined. There were a total of 51 graft failures due to thrombosis among the 2750 reported renal transplants (1.85%) (95% CI (1.39%, 2.41%)). This represents the most common cause of graft loss during the first year post-transplant accounting for 35% of first year losses and 18% of all graft losses. The incidence of thrombosis among patients who received IL-2 receptor antibodies was 1.07% (12/1126) compared to 2.40% (39/1624) among patients who did not (OR 0.44, 95% CI 0.23, 0.84, p = 0.014). Use of IL-2 receptor blockade was the only significant prognostic factor in a multivariate model with previously identified risk factors. Analysis of NAPRTCS data found that the use of IL-2 receptor antibodies as induction therapy is associated with a significantly decreased risk of graft failure due to thrombosis. This provocative finding requires further investigation to determine whether thrombotic failure can be decreased by this therapeutic strategy. 相似文献
24.
Mark G Stokes Christopher D Chambers Ian C Gould Therese English Elizabeth McNaught Odette McDonald Jason B Mattingley 《Clinical neurophysiology》2007,118(7):1617-1625
OBJECTIVE: To examine the relationship between coil-cortex distance and effective cortical stimulation using transcranial magnetic stimulation (TMS) in the left and right motor cortex. We also compare the effect of coil-cortex distance using 50 and 70 mm figure-eight stimulating coils. METHODS: Coil-cortex distance was manipulated within each participant using 5 and 10 mm acrylic separators placed between the coil and scalp surface. The effect of cortical stimulation was indexed by resting motor threshold (MT). RESULTS: Increasing distance between the coil and underlying cortex was associated with a steep linear increase in MT. For each additional millimetre separating the stimulating coil from the scalp surface, an additional approximately 2.8% of absolute stimulator output (approximately 0.062 T) was required to reach MT. The gradient of the observed distance effect did not differ between hemispheres, and no differences were observed between the 50 and 70 mm TMS coils. CONCLUSIONS: Coil-cortex distance directly influences the magnitude of cortical stimulation in TMS. The relationship between TMS efficacy and coil-cortex distance is well characterised by a linear function, providing a simple and effective method for scaling stimulator output to a distance adjusted MT. SIGNIFICANCE: MT measured at the scalp-surface is dependent on the underlying scalp-cortex distance, and therefore does not provide an accurate index of cortical excitability. Distance-adjusted MT provides a more accurate index of cortical excitability, and improves the safety and efficacy of MT-calibrated TMS. 相似文献
25.
John W.D. McDonald 《Canadian Medical Association journal》2003,168(10):1237-1238
26.
27.
L H Anderson T L McDonald G M Thiele L W Klassen 《Journal of clinical laboratory analysis》1992,6(3):113-118
Different assay systems have been used to quantitate lymphokine-induced natural cytotoxic activity as a measure of immune status. This study compares the effects of inducing cytotoxicity in a bulk culture system, where effector cells are transferred to a micro culture well for assay, to a micro culture system where the effector cells are not transferred. The effector/target ratio for both the bulk and micro culture systems was calculated using the number of viable effector cells present at the time of target cell addition. After overnight incubation with interleukin-2 (IL-2), the lytic activity of murine spleen cells to targets using a micro culture system was increased two-fold over the bulk culture method. This increase was amplified further after 5 days of activation with IL-2, in that the micro culture system resulted in a four-fold increase in cytotoxic activity. The loss of some adherent cells in the bulk culture system did not explain the overall decrease in recovered cytotoxicity. The difference appeared to be related to cell loss during centrifugation. Therefore, the E/T ratios are different in the two systems if not corrected for the number of viable cells. 相似文献
28.
Meningeal hemangiopericytoma of the posterior fossa and thoracic spinal epidural space: case report.
The rare combination of spinal and intracranial meningeal hemangiopericytomas in the same patient is reported. The coexistence of cerebral and spinal meningiomas of all histological subtypes is distinctly uncommon with only nine cases found in the literature. 相似文献
29.
Sidestream versus mainstream carbon dioxide analyzers 总被引:1,自引:0,他引:1
30.
Helen McDonald 《BJOG : an international journal of obstetrics and gynaecology》1998,105(11):1240-1240