全文获取类型
收费全文 | 178篇 |
免费 | 0篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 10篇 |
机械仪表 | 2篇 |
建筑科学 | 4篇 |
能源动力 | 5篇 |
轻工业 | 18篇 |
水利工程 | 1篇 |
无线电 | 26篇 |
一般工业技术 | 20篇 |
冶金工业 | 67篇 |
自动化技术 | 11篇 |
出版年
2022年 | 1篇 |
2018年 | 3篇 |
2013年 | 8篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 5篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 5篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有178条查询结果,搜索用时 10 毫秒
91.
Scott McCall G. Cao F. Freibert M. Shepard P. Henning J. E. Crow B. Andraka 《Journal of Superconductivity》1995,8(5):669-670
The electrical resistivity (T,x) and magnetic susceptibility (T,H), and specific heat C(T,x) have been measured on single crystals of Y1–x TbxBa2Cu3O7. The results strongly suggest the appearance of strong 4f electron hybridization. It becomes apparent that the Tb doped system possesses properties that largely deviate from the well-known behavior of the other high Tc and doped high Tc systems. 相似文献
92.
Shangtong Zhang Roya N Borazjani Joseph C Salamone Donald G Ahearn Sidney A Crow George E Pierce 《Contact lens & anterior eye》2005,28(3):113-119
PURPOSE: To compare lysozyme adsorption and absorption and bacterial adhesion interactions on conventional (etafilcon A) and silicone (balafilcon A) hydrogel contact lenses. METHOD: Lysozyme concentrations and activities associated with the lenses were determined after solvent extraction (trifluoroacetic acid/acetonitrile) and directly on the lenses without extraction with micrococcal- and micro-bicinchoninic acid (BCA) assays. Cells of bacteria with radiolabeled leucine and a cell recovery procedure were used in determinations of bacterial adhesion to lenses. RESULTS: Lysozyme was adsorbed and absorbed to the conventional etafilcon A lens at about a 10-fold greater concentration than to the balafilcon A silicone hydrogel lens. Enzyme activities on the surfaces of both lenses were similar but replenished after saline extraction only with the etafilcon A lens. Lysozyme on the lens surface showed significant lysis of Micrococcus luteus but had a negligible effect on the adhesion and survival of Staphylococcus aureus. Lysozyme did not appear to affect the survival of Pseudomonas aeruginosa on lenses. CONCLUSION: In vitro experiments show that concentrations of active lysozyme on the surface of the etafilcon A lens, unlike the balafilcon A lens which showed negligible absorption, may be sustained from the lens matrix. Lysozyme deposited on hydrogel lenses had marked activity against M. luteus but relatively minor effects on the primary adhesion of P. aeruginosa and S. aureus. 相似文献
93.
The relationship between measures (of size or function) on one side of the brain, in relation to the difference between the two sides on that measure, are important components of theories of hemispheric asymmetry. For example, it has been concluded that increasing lateralization (e.g., of hand skill or planum temporale area) occurs at the expense of the non-dominant hemisphere. Here it is demonstrated that such relationships could merely be a necessary consequence of relating components of a laterality index to the index (L - R)/(L + R) itself, or indeed to L - R. An alternative approach (using random data to exemplify the null hypothesis) is presented together with an application to data on hand skill from 12,782 11-year-olds in a cohort study. This demonstrates a symmetry hitherto undocumented of maximal hand skill in left and right hands in left- and right-hand writers respectively, the point of the maximum falling short of the population mean for relative hand skill in either case. If degrees of laterality are what is genetically determined, this suggests that selection is present for a function (perhaps language) associated with a greater magnitude of lateralization than is represented by hand skill. 相似文献
94.
Identified type A photoreceptors of Hermissenda express differential effects of classical conditioning. Lateral type A photoreceptors exhibit an increase in excitability to both the conditioned stimulus (CS; light) and extrinsic current. In contrast, medial type A photoreceptors do not express enhanced excitability, but do show enhancement of the medial B to medial A synaptic connection. Therefore, both enhanced excitability and changes in synaptic strength may contribute to long-term plasticity underlying classical conditioning. The activation of protein kinase C (PKC) is involved in the induction of enhanced excitability of identified type B photoreceptors produced by one-trial conditioning and the expression of enhanced excitability in B photoreceptors after multitrial classical conditioning. We have examined a possible role for persistent kinase activity in the expression of enhanced excitability in lateral type A photoreceptors and enhancement of the medial B to medial type A synaptic connection after classical conditioning. Injection of the PKC inhibitor peptide PKC(19-36) into medial type B photoreceptors of conditioned animals did not significantly change the amplitude of medial A IPSPs elicited by single spikes in the medial B photoreceptor. Injections of PKC(19-36) into medial B photoreceptors of pseudorandom controls also did not significantly change the amplitude of IPSPs recorded from the medial A photoreceptor. In contrast, spikes elicited by extrinsic current in lateral type A photoreceptors of conditioned animals were significantly reduced in frequency after intracellular injection of PKC(19-36) as compared with pseudorandom controls. Injection of the noninhibitory analog peptide [glu27]PKC(19-36) did not affect excitability. Thus, enhanced excitability in the lateral A photoreceptor of conditioned animals seems to be influenced, in part, by a constitutively active kinase or a persistent kinase activator, whereas synaptic enhancement of the connection between the medial B and medial A photoreceptors of conditioned animals may involve a different mechanism. 相似文献
95.
EJ Schattner J Mascarenhas I Reyfman M Koshy C Woo SM Friedman MK Crow 《Canadian Metallurgical Quarterly》1998,91(8):2689-2697
Chronic lymphocytic leukemia (CLL) is characterized by a clonal expansion of CD5(+) B cells in the peripheral blood. Associated immune aberrations include abnormal Th-cell function and pathogenic autoantibodies. Under most circumstances, CLL B cells do not proliferate in culture and express a limited repertoire of surface antigens, including CD19, CD20, CD23, CD27, CD40, and CD70. In this report, we demonstrate that freshly isolated B cells from a subset of CLL cases constitutively express CD40 ligand (CD40L, CD154), a member of the tumor necrosis factor family which is normally expressed by activated CD4(+) T cells and mediates T-cell-dependent B-cell proliferation and antibody production. The degree of CD40L expression varied considerably among the CLL cases examined. CD40L was detected in purified CLL B cells by immunofluorescence flow cytometry, by RT-PCR, and by immunoprecipitation. To demonstrate that CD40L in the CLL B cells is functional, we used irradiated CLL cells to stimulate IgG production by target, nonmalignant B cells in coculture. The CLL B cells induced IgG production by normal B cells to a similar degree as did purified T cells in a process which was partially inhibited by monoclonal antibody to CD40L. This is one of the first reports of CD40L expression in a B-cell tumor. The data suggest that CD40L in the tumor cells may be a factor in the generation of pathologic antibodies by normal B cells in some patients with CLL. 相似文献
96.
JP Crow 《Canadian Metallurgical Quarterly》1997,1(2):145-157
This article describes the use and prescribing of menopausal and postmenopausal hormone therapy (HT) in one example country, Finland, and the trends and levels of HT use in other western countries for comparison. Previously published studies were reviewed and reanalyzed, and some additional unpublished data from Finnish surveys were compiled. The use of HT increased in Finland up to 1994. In Finland the initiative for HT use came more often from physicians than women themselves, physicians valued HT more than women, women's period of use of HT was shorter than physicians' recommendations, women's reasons for using HT were usually to treat symptoms, but physicians considered HT also useful in the prevention of later diseases. Gynecologists were more favorable toward HT than other physicians. HT has become common in very different times in different countries, but with the exception of the US experience in the 1970s, the trend has been towards increasing use. One motivation to do surveys on physicians' prescribing or women's use of HT has been to facilitate HT use. The large variation in HT use may reflect the uncertainty concerning its true value. The reasons for the large-scale prevention with HT have not been systematically studied, but it is likely due to various social and commercial forces. 相似文献
97.
Previous studies from our laboratory have demonstrated that the mitochondrial protein manganese superoxide dismutase is inactivated, tyrosine nitrated, and present as higher molecular mass species during human renal allograft rejection. To elucidate mechanisms whereby tyrosine modifications might result in loss of enzymatic activity and altered structure, the effects of specific biological oxidants on recombinant human manganese superoxide dismutase in vitro have been evaluated. Hydrogen peroxide or nitric oxide had no effect on enzymatic activity, tyrosine modification, or electrophoretic mobility. Exposure to either hypochlorous acid or tetranitromethane (pH 6) inhibited (approximately 50%) enzymatic activity and induced the formation of dityrosine and higher mass species. Treatment with tetranitromethane (pH 8) inhibited enzymatic activity 67% and induced the formation of nitrotyrosine. In contrast, peroxynitrite completely inhibited enzymatic activity and induced formation of both nitrotyrosine and dityrosine along with higher molecular mass species. Combination of real-time spectral analysis and electrospray mass spectroscopy revealed that only three (Y34, Y45, and Y193) of the nine total tyrosine residues in manganese superoxide dismutase were nitrated by peroxynitrite. Inspection of X-ray crystallographic data suggested that neighboring glutamate residues associated with two of these tyrosines may promote targeted nitration by peroxynitrite. Tyr34, which is present in the active site, appeared to be the most susceptible residue to peroxynitrite-mediated nitration. Collectively, these observations are consistent with previous results using chronically rejecting human renal allografts and provide a compelling argument supporting the involvement of peroxynitrite during this pathophysiologic condition. 相似文献
98.
IM Ezeonu JA Noble RB Simmons DL Price SA Crow DG Ahearn 《Canadian Metallurgical Quarterly》1994,60(6):2149-2151
Fiberglass duct liners and fiberglass duct boards from eight buildings whose occupants complained of unacceptable or moldy odors in the air were found to be heavily colonized by fungi, particularly by Aspergillus versicolor. Unused fiberglass was found to be susceptible to fungal colonization in environmental chambers dependent upon relative humidity. No colonization was observed at relative humidities below 50%. 相似文献
99.
The National High Magnetic Field Laboratory (NHMFL) operates three facilities in support of magnet-related research. The main facilities are located at Florida State University, Tallahassee, Florida, the ultra-low-temperature high-magnetic-field facilities are located at the University of Florida, Gainesville, Florida, and the pulsed field facilities are located at the Los Alamos National Laboratory, Los Alamos, New Mexico. These facilities support a wide variety of magnet-related research capabilities that are open to all qualified users through a peer-reviewed proposal process. This paper summarizes the research capabilities at the DC facilities at the main facility of the NHMFL and the High B/T Facility at the University of Florida. A few select scientific achievements in the high field condensed matter sciences are presented to highlight the research capabilities available to all users. The NHMFL is supported by the United States National Science Foundation and the State of Florida. 相似文献
100.
Dual career couples are now the norm instead of the exception in the modern workplace. Many universities encounter couples who are seeking two tenure-track faculty positions, and the success of many academic searches hinges on finding suitable employment for each member of a dual career team. Couples in these situations are often unsure of the most effective strategy for finding two suitable academic positions and often rely on anecdotal information when searching for professorial positions. With these shortcomings in mind, we designed a survey to determine the common attributes of successful dual career searches where both members of the dual career team successfully found tenure-track positions in engineering. This paper reports the findings of this survey and provides some guidelines to dual career couples seeking academic positions and to administrators and faculty seeking to work out hires involving dual career couples. 相似文献