全文获取类型
收费全文 | 330篇 |
免费 | 12篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 13篇 |
综合类 | 15篇 |
化学工业 | 28篇 |
金属工艺 | 12篇 |
机械仪表 | 7篇 |
建筑科学 | 7篇 |
矿业工程 | 3篇 |
能源动力 | 7篇 |
轻工业 | 12篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
无线电 | 12篇 |
一般工业技术 | 18篇 |
冶金工业 | 157篇 |
原子能技术 | 4篇 |
自动化技术 | 51篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 9篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 19篇 |
2009年 | 19篇 |
2008年 | 17篇 |
2007年 | 13篇 |
2006年 | 13篇 |
2005年 | 18篇 |
2004年 | 12篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1998年 | 53篇 |
1997年 | 40篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 1篇 |
1990年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有359条查询结果,搜索用时 15 毫秒
31.
FcR gamma-deficient mice were used to examine the role of Fc gamma receptors in the induction of peripheral tolerance to human gamma-globulin (HGG). FcR gamma-deficient mice injected with HGG in adjuvant demonstrated a CD4+ T cell response to in vitro challenge with HGG, as assayed by proliferation, cytokine secretion, and Ag-specific help for B cell Ab production. In vitro kinetics of Ag-specific proliferation were similar in both conventional and knockout mice. Peripheral tolerance could be established in these mice with a single dose of deaggregated protein, despite the lack of functional Fc gammaRI, the high affinity receptor for monomeric IgG. Establishment of unresponsiveness was observed at both the T and B cell levels. T cell tolerance was manifested in the reduction of T cell helper function and Ag-induced release of Th1- and Th2-like cytokines, as well as decreased proliferation to Ag-specific stimulation. B cell tolerance was demonstrated in knockout and normal mice by failure to detect HGG-specific Ab production using an immunization protocol for Ab production that bypasses the need for Ag-specific T cells. These results demonstrate that induction of tolerance in CD4+ cells to HGG does not require transduction of a signal through Fc gammaRI. Furthermore, the ability to induce tolerance to HGG in B cells in Fc gammaRII-deficient mice suggests that down-regulation of Ag-specific B cells through Fc gammaRII is not the mechanism by which B cell tolerance is induced. However, Fc gammaRII plays a role in regulating the immune response since the Ab response to immunogenic HGG in Fc gammaRII-deficient mice is markedly enhanced. 相似文献
32.
33.
34.
Low-density lipoprotein (LDL) apheresis is a potent treatment for patients with coronary heart disease and severe hereditary forms of LDL hypercholesterolemia not adequately responsive to drug treatment. Until now, the beneficial effect of aggressive reduction of LDL cholesterol by LDL apheresis on the course of coronary heart disease has been demonstrated in one 3-year study and several studies lasting 2 years. We now report on the clinical course, lipoprotein concentrations, coronary angiograms, and side effects in patients undergoing LDL apheresis for as long as 8.6 years. Thirty-four patients (21 men and 13 women) with coronary heart disease and heterozygous familial hypercholesterolemia (FH) not adequately responsive to lipid-lowering drugs received weekly (four patients biweekly) LDL apheresis for 4.6 +/- 2.6 years under diet and lipid-lowering drug therapy; after 0.5 to 3 years, simvastatin in the maximal tolerable dose was added. The baseline LDL cholesterol concentration was 6.9 +/- 1.6 mmol/L. Combined treatment in the steady state yielded a pretreatment and posttreatment LDL cholesterol concentration of 4.8 +/- 0.9 and 1.8 +/- 0.4 mmol/L, respectively. The calculated interval mean LDL cholesterol was 3.3 +/- 0.6 mmol/L. Evaluation of the coronary angiographies revealed a definite regression of coronary lesions in four patients (11.8%); in 19 patients, there was a cessation of progression. Two patients developed atheromatous lesions in bypass grafts (L.H., 60% stenosis; S.M., occlusion). Of 23 patients eligible for the scoring of anginal symptoms, five (21.7%) reported a reduction of the frequency and severity of angina pectoris. The mean coronary symptom score in 23 patients changed from 1.65 +/- 0.83 at baseline to 1.39 +/- 0.66 at the end of the study. During the whole observation period, we observed three sudden deaths, one nonfatal myocardial infarction, and five patients requiring hospital admission because of unstable angina pectoris, one of which was followed by a transluminal coronary angioplasty. Aggressive reduction of LDL cholesterol with combined LDL apheresis and drugs induced regression of coronary lesions in four of 34 patients and prevented progression in 29 patients for as long as 8.6 years. The effect on LDL and high-density lipoprotein (HDL) cholesterol and lipoprotein(a) [Lp(a)] was comparable with all three apheresis techniques. Therefore, no obvious difference between the three techniques was found regarding changes in coronary lesions. 相似文献
35.
36.
37.
38.
沉梢坝是长江崩窝治理形式之一,它是由若干树枝梢体在崩窝口门叠加而成的透水坝,是在岸线崩塌形成崩窝以后采用的锁口促淤方法。施工中使用定点变向抛投工艺,形成了一座符合设计要求的透水坝体。经过几个汛期的检验,坝体内崩窝处淤积明显,沉梢坝起到了显著的促淤效果。 相似文献
39.
TJ Vogl EL H?nninen WO Bechstein P Neuhaus G Schumacher R Felix 《Canadian Metallurgical Quarterly》1998,33(3):136-140
Aseptic loosening of implant components is a common and important complication of both cemented and uncemented prosthetic joint replacements. Wear particles derived from organic polymer and metal implant biomaterials are commonly found within macrophages and macrophage polykaryons in the fibrous membrane between loose implant components and the host bone undergoing resorption. In order to determine whether biomaterial particle-containing, foreign-body macrophages may contribute to periprosthetic bone resorption, we cultured murine monocytes that had phagocytosed particles of biomaterials commonly employed in bone implant surgery [polymethylmethacrylate (PMMA), ultra-high molecular weight polyethylene (PE), titanium and chromium-cobalt] on bone slices and glass coverslips with UMR 106 osteoblast-like stromal cells in the presence of 1,25-dihydroxy-vitamin D3. Under these conditions, all biomaterial particle-containing, foreign-body macrophages differentiated into osteoclastic cells, i.e. tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells capable of extensive lacunar bone resorption. This study shows that particle phagocytosis by macrophages does not abrogate the ability of these cells to undergo osteoclast differentiation. These findings emphasise the importance of the foreign-body macrophage response to biomaterial wear particles in the pathogenesis of aseptic loosening. 相似文献
40.
LL Kiefer OR Ittoop K Bunce AT Truesdale DH Willard JS Nichols SG Blanchard K Mountjoy WJ Chen WO Wilkison 《Canadian Metallurgical Quarterly》1997,36(8):2084-2090
Several mutations that cause ectopic expression of the agouti gene result in obesity, hyperinsulinemia, and yellow coat color. A candidate pathway for agouti induced obesity and hyperinsulinemia is through altered signaling by melanocortin receptors, as agouti normally regulates coat coloration through antagonism of melanocortin receptor 1. Furthermore, melanocortin peptides mediate functions including steroidogenesis, lipolysis, and thermoregulation. We report apparent inhibition dissociation constants for mouse and human agouti protein inhibition of ligand binding to the melanocortin receptors, to determine which of these receptors might be involved in agouti induced diabetes. The similarity in the apparent K(I) values for agouti inhibition of ligand binding to the brain melanocortin receptors 3 and 4 (mouse: K(I) app = 190 +/- 74 and 54 +/- 18 nM; human: K(I) app = 140 +/- 56 and 70 +/- 18 nM, respectively) suggests that the MC3-R is a potential candidate for a receptor mediating the effects of agouti protein overexpression. Agouti residues important for melanocortin receptor inhibition were identified through the analysis of deletion constructs and site-specific variants. Val83 is important for inhibition of binding to MC1-R (K(I) app for Val83Ala agouti increased 13-fold relative to wild-type protein). Arg85, Pro86, and Pro89 are important for selective inhibition of binding between MC1-R and MC3-R and MC4-R as their apparent K(I) values are essentially unchanged at MC1-R, while they have increased 6-10-fold relative to wild-type protein at MC3-R and MC4-R. 相似文献