全文获取类型
收费全文 | 3400篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 28篇 |
金属工艺 | 5篇 |
机械仪表 | 2篇 |
建筑科学 | 13篇 |
能源动力 | 2篇 |
轻工业 | 10篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 17篇 |
一般工业技术 | 32篇 |
冶金工业 | 3273篇 |
自动化技术 | 17篇 |
出版年
2021年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 8篇 |
1999年 | 112篇 |
1998年 | 1095篇 |
1997年 | 604篇 |
1996年 | 418篇 |
1995年 | 214篇 |
1994年 | 163篇 |
1993年 | 203篇 |
1992年 | 15篇 |
1991年 | 40篇 |
1990年 | 45篇 |
1989年 | 39篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 19篇 |
1985年 | 21篇 |
1983年 | 3篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 27篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 68篇 |
1976年 | 126篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1956年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有3405条查询结果,搜索用时 500 毫秒
991.
Coles Angela R.; Pakenham Kenneth I.; Leech Christine 《Canadian Metallurgical Quarterly》2007,52(2):133
Objective: To evaluate an intervention for children of parents with multiple sclerosis (MS). It was hypothesized that the intervention would increase knowledge of MS, approach coping, and social support and decrease avoidant coping and stress appraisals. It was expected that these changes would reduce the adverse impacts of caregiving and produce better adjustment. Method: Twenty children (9-14 years) who had a parent with MS attended a 6-day camp intervention. These children completed questionnaires at pre- and postintervention and at 3-month follow-up; their parents with MS (N = 14) completed questionnaires at preintervention and at follow-up. Results: After the intervention, children reported significant decreases in distress, stress appraisals, caregiving compulsion, and activity restrictions and increases in social support and knowledge of MS. Parental data confirmed the increase in the children's knowledge of MS, and overall, qualitative data supported the quantitative findings. Qualitative data showed that the intervention had indirect effects on some parents and families. Conclusions: Findings offer preliminary support for the use of a stress- and coping-based intervention for supporting children and their families with parental MS. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
992.
CJ Cummings TR Martin CW Frevert JM Quan VA Wong SM Mongovin TR Hagen KP Steinberg RB Goodman 《Canadian Metallurgical Quarterly》1999,162(4):2341-2346
Neutrophils (polymorphonuclear neutrophils; PMN) and a redundant system of chemotactic cytokines (chemokines) have been implicated in the pathogenesis of the acute respiratory distress syndrome in patients with sepsis. PMN express two cell surface receptors for the CXC chemokines, CXCR1 and CXCR2. We investigated the expression and function of these receptors in patients with severe sepsis. Compared with normal donors, CXCR2 surface expression was down-regulated by 50% on PMN from septic patients (p < 0.005), while CXCR1 expression persisted. In vitro migratory responses to the CXCR1 ligand, IL-8, were similar in PMN from septic patients and normal donors. By contrast, the migratory response to the CXCR2 ligands, epithelial cell-derived neutrophil activator (ENA-78) and the growth-related oncogene proteins, was markedly suppressed in PMN from septic patients (p < 0.05). Ab specific for CXCR1 blocked in vitro migration of PMN from septic patients to IL-8 (p < 0.05), but not to FMLP. Thus, functionally significant down-regulation of CXCR2 occurs on PMN in septic patients. We conclude that in a complex milieu of multiple CXC chemokines, CXCR1 functions as the single dominant CXC chemokine receptor in patients with sepsis. These observations offer a potential strategy for attenuating adverse inflammation in sepsis while preserving host defenses mediated by bacteria-derived peptides such as FMLP. 相似文献
993.
CR Pullinger D Gaffney MM Gutierrez MJ Malloy VN Schumaker CJ Packard JP Kane 《Canadian Metallurgical Quarterly》1999,40(2):318-327
Familial ligand-defective apolipoprotein B (apoB) is a group of disorders caused by mutations in the apoB gene. In this report the R3531C mutation is characterized further using a monoclonal antibody MB19/dynamic laser light scattering technique to measure ratios of Cys(3531) to normal low density lipoprotein (LDL) particles. All six subjects studied showed a preferential accumulation of particles carrying the defective apoB allotype. We determined binding properties of LDL from R3531C heterozygotes by measurement of high-affinity binding to LDL receptors on fibroblasts and its ability promote growth of U937 cells. LDL from R3531C heterozygotes, compared to normal LDL, had 49.3% of the binding affinity and was 74% as effective in a U937 cell proliferation assay. To identify new probands, we screened 2570 subjects for the R3531C mutation. Nine probands were found with 15 affected relatives. Of the seven haplotypes we uncovered, two were novel, while five were identical to one initially reported as associated with Cys3531. Three silent mutations were detected also: T3540T, N3542N and T3552T. Analysis of lipid profiles of R3531C families showed, as with the R3500Q mutation, variable expression of the phenotype, modulated by environmental and other genetic factors. Both mutations tend to produce lower plasma levels of LDL in affected subjects than do defects of the LDL receptor (familial hypercholesterolemia, FH). This study shows that the Cys(3531) LDL particles are not only defective at binding to the LDL receptor, as determined by two separate methods, but that in all cases they accumulate preferentially compared to the normal allotype.-Pullinger, C. R., D. Gaffney, M. M. Gutierrez, M. J. Malloy, V. N. Schumaker, C. J. Packard, and J. P. Kane. Apolipoprotein B R3531C mutation: characteristics of 24 subjects from 9 kindreds. . 相似文献
994.
Cytogenetic analyses of 85 testicular germ cell tumors, of which 54 were karyotypically abnormal, showed recurrent breakpoints at chromosome bands 1p36, 1p13-1qh, 11q23, 19q13, and the pericentromeric regions of the acrocentric chromosomes. Postchemotherapy tumors had significantly more rearrangements of bands 3p25-p26, 6q16-q21, 8p22-p23 when compared with untreated tumors, while untreated tumors had more rearrangements of 9p22-p24 when compared with postchemotherapy tumors. Frequent breakpoints also were identified at 15q15 and 9qh in untreated tumors. Tumors of different histopathology, clinical stage, and treatment status showed no significant differences in the frequencies of i(12p)-positive and i(12p)-negative tumors. 相似文献
995.
SE Wolfe DE Howard JA Schetz CJ Cheng R Webber DM Beatty BM Chronwall SJ Morris 《Canadian Metallurgical Quarterly》1999,72(2):479-490
Dopamine D2 receptors both acutely and chronically inhibit high-voltage-activated Ca2+ channels (HVA-CCs). Two alternatively spliced isoforms, D2L (long) and D2S (short), are expressed at high levels in rat pituitary intermediate lobe melanotropes but are lacking in anterior lobe corticotropes. We stably transfected D2L and D2S into corticotrope-derived AtT20 cells. Both isoforms coupled to inhibition of Q-type calcium channels through pertussis toxin-sensitive G proteins. Thus, we have created a model system in which to study the kinetics of D2-receptor regulation of Ca2+ channels. Rapid inhibition of HVA-CCs was characterized using a novel fluorescence video imaging technique for the measurement of millisecond kinetic events. We measured the time elapsed (lag time) between the arrival of depolarizing isotonic 66 mM K+, sensed by fluorescence from included carboxy-X-rhodamine (CXR), and the beginning of increased intracellular Ca2+ levels (sensed by changes in indo 1 fluorescence ratio). The lag time averaged 350-550 ms, with no significant differences among cell types. Addition of the D2-agonist quinpirole (250 microM) to the K+/CXR solution significantly increased the lag times for D2-expressing cells but did not alter the lag time for AtT20 controls. The increased lag times for D2L- and D2S-transfected cells suggest that at least a fraction of the Ca2+ channels was inhibited within the initial 350-550 ms. As this inhibition time is too fast for a multistep second messenger pathway, we conclude that inhibition occurs via a membrane-delimited diffusion mechanism. 相似文献
996.
Tenascin is a large extracellular matrix glycoprotein expressed in neural and non-neural tissues. In the central nervous system, tenascin is synthesized by astrocytes during development and wound healing, forming barriers and affecting neurite outgrowth. In this study we examined tenascin expression in optic nerve heads of normal and glaucomatous eyes and found that there is upregulation of tenascin mRNA and protein in reactive astrocytes from human glaucomatous optic nerve heads compared to normal age-matched controls. In the prelaminar region there was a band of tenascin immunoreactivity around the blood vessels of glaucomatous, but not in normal eyes. However, tenascin mRNA was only localized to astrocytes, suggesting that astrocytes are the cellular source of tenascin. In the lamina cribrosa, tenascin immunoreactivity and gene expression were localized to astrocytes in the cribriform plates and inside the nerve bundles. In the post-lamina region, tenascin immunoreactivity and gene expression were localized to astrocytes lining the pial septum immediately adjacent to the lamina cribrosa. In normal optic nerve heads, tenascin expression at the mRNA and protein levels was confined to clusters of astrocytes at the level of Bruch's membrane in the prelaminar optic nerve head. In glaucoma, enhanced expression of tenascin may be protective to the axons of the retinal ganglion cells by providing a barrier for humoral and/or blood-borne factors that may cause further neural damage. However, the precise role of tenascin in glaucomatous optic neuropathy is not yet elucidated. 相似文献
997.
998.
999.
YJ Geng Y Ishikawa DE Vatner TE Wagner SP Bishop SF Vatner CJ Homcy 《Canadian Metallurgical Quarterly》1999,84(1):34-42
We examined the potential involvement of two CC chemokine receptors (CCRs), CCR-1 and CCR-3, in the functional activation of granulocyte-macrophage colony-stimulating factor (GM-CSF) plus interleukin-4 (IL-4)-generated human peripheral blood monocyte-derived immature dendritic cells (DCs). Flow cytometric analysis showed that CCR-1, CCR-3, CCR-5, and CXC chemokine receptor (CXCR)-4 were expressed on the cell surface of monocyte-derived DCs. Treatment with a monoclonal antibody (MoAb) to either CCR-1 or CCR-3 but not MoAbs to CCR-5 and CXCR-4 abolished chemotactic migration of monocyte-derived DCs. The DCs treated with either the anti-CCR-1 MoAb or anti-CCR-3 MoAb were less efficient than untreated DCs in proliferation of allogeneic T cells (TCs) and TC-derived secretion of interferon-gamma (IFN-gamma). The homotypic aggregation of DCs and heterotypic aggregation of DCs with TCs were suppressed by the anti-CCR-1 MoAb or anti-CCR-3 MoAb. These results indicate that CCR-1 and CCR-3 specifically regulate interaction of TCs and DCs in the process of antigen presentation. 相似文献
1000.
Alic N. Windmiller J.R. Coles J.B. Radic S. 《IEEE journal of selected topics in quantum electronics》2008,14(3):681-690
Continuously tunable optical delay lines based on parametric process in optical fibers are described theoretically and demonstrated experimentally. Performance limits are outlined and compared to alternative approaches capable of continually adjustable delay management. The current record of 105 ns tunable optical delay at 10 Gb/s is presented, with a delay-bandwidth product of 1055. 相似文献