全文获取类型
收费全文 | 1492篇 |
免费 | 1篇 |
专业分类
化学工业 | 4篇 |
机械仪表 | 1篇 |
轻工业 | 3篇 |
一般工业技术 | 4篇 |
冶金工业 | 1481篇 |
出版年
2015年 | 1篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2010年 | 1篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2003年 | 4篇 |
2000年 | 1篇 |
1999年 | 35篇 |
1998年 | 468篇 |
1997年 | 277篇 |
1996年 | 179篇 |
1995年 | 91篇 |
1994年 | 72篇 |
1993年 | 84篇 |
1992年 | 7篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 26篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 24篇 |
1976年 | 75篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1493条查询结果,搜索用时 15 毫秒
81.
SB Levery MS Toledo E Suzuki ME Salyan S Hakomori AH Straus HK Takahashi 《Canadian Metallurgical Quarterly》1996,222(2):639-645
An acidic glycolipid (Band 1), purified from P. brasiliensis by a combination of ion exchange chromatography, HPLC, and HPTLC, was found to be reactive with sera of all patients with paracoccidioidomycosis (PCM). Monosaccharide analysis of Band 1 yielded mannose and galactose in a 2:1 ratio, while mild acid hydrolysis and mild periodate oxidation/NaB3H4 reduction indicated the presence of a terminal galactofuranose. Preliminary analysis of 1H-NMR and MS data suggests that the structure of the glycan is Galf beta 1-->6(Manp alpha 1-->3)Manp beta 1-->2Ins (Ins = myo-inositol). Removal of the galacto-furanose decreased by 60-80% the reactivity of sera from PCM patients with Band 1, suggesting that this residue is immunodominant. With the presumed absence of galactofuranose in mammalian hosts, compounds containing this residue may be useful targets for therapy of several parasitic and fungal diseases. 相似文献
82.
Maria M Velencoso Agustin SB Gonzalez Joaquin C García‐Martínez Maria J Ramos Antonio De Lucas Juan F Rodriguez 《Polymer International》2013,62(5):783-790
A simple strategy for the synthesis and functionalization of polyurethanes is described. Anionic ring‐opening polymerization was combined with ‘click’ chemistry to synthesize polyols with fluorescent properties. This route allows the incorporation of a wide range of functionalities in the polyols with an easy, clean and highly selective process compatible with several types of functional groups. The proposed strategy opens the way to the production, in a cost‐effective way, of ‘smart’ polyurethanes with non‐conventional properties like fire retardancy, antimite properties, antibacterial properties, etc. Alkynyl groups were introduced into the polyol chains by the controlled addition of glycidyl propargyl ether as co‐monomer during a conventional anionic ring‐opening copolymerization with propylene oxide. Subsequently 4‐azidomethyl‐7‐methoxycoumarin molecules were introduced onto the alkynyl‐polyether polyols by copper‐catalysed cycloaddition reactions to produce end‐functionalized polyols. The chemical structure of the novel polyols was characterized using infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography with triple detection and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy. These characterization techniques confirmed the presence of a considerable amount of functional groups in the structure of the polyols. Finally, various fluorescent rigid foams, based on the functionalized polyols, were synthesized. Copyright © 2012 Society of Chemical Industry 相似文献
83.
84.
85.
86.
87.
M Diez J Koistinaho SJ Dearmond D Groth SB Prusiner T H?kfelt 《Canadian Metallurgical Quarterly》1997,94(24):13267-13272
Using autoradiographic binding methodology with monoiodinated peptide YY together with the agonists neuropeptide Y (NPY) and NPY (13-36), as well as in situ hybridization with oligonucleotide probes complementary to the NPY Y2 receptor (Y2-R) mRNA, we have studied whether or not intracerebral prion inoculation affects Y2-Rs in male CD-1 mice. Monoiodinated peptide YY binding, mainly representing Y2-Rs, was down-regulated by 85% in the CA1 strata oriens and radiatum and by 50-65% in the CA3 stratum oriens 110-140 days postinoculation. In the CA3 stratum radiatum, where the mossy fibers from the dentate granule cells project, there was a significant decrease in PYY binding at 110-120 days. Y2-R mRNA, moderately expressed both in the CA1 and CA3 pyramidal cell layers and the granule cell layer in the dentate gyrus, showed a slight, but not significant, decrease in CA3 neurons 130 days postinoculation. The results indicate that the accumulation of the scrapie prion protein in the CA1-3 region strongly inhibits NPY binding at the Y2-Rs, which, however, is only marginally due to reduced Y2-R mRNA expression. The loss of the ability of NPY to bind to inhibitory Y2-Rs may cause dysfunction of hippocampal circuits and may contribute to the clinical symptoms in mouse scrapie. 相似文献
88.
To evaluate the influence of aging on the increase in endogenous glucose production that follows injury, we studied 22 fully resuscitated, clinically stable, previously healthy patients aged < or = 30 yr or > or = 60 yr admitted to hospital following injury, and 11 healthy volunteers in the same age groups. Endogenous glucose production was determined using a primed constant infusion of D-glucose-6,6-2d2. Urine cortisol and C-peptide were markedly higher in patients than volunteers (both P < 0.01), and urine C-peptide was lower in older than in younger patients (P < 0.05). Urine cortisol increased as a function of the interaction of age and Injury Severity Score (ISS) (r2 = 0.40, P < 0.001). Intracellular water was markedly lower and extracellular water greater in patients compared with volunteers (both P < 0.001), reflecting the loss of body cell mass and expansion of the extracellular space following injury. Endogenous glucose production (milligrams per minute per liter intracellular water) was best described as a function of ISS and age-ISS interaction (r2 = 0.35, all P < 0.05), and was increased 56% and 78% in younger and older patients, respectively, in comparison with the respective volunteer groups. Endogenous glucose production following injury increases in relation to the severity of injury and patient age. Greater cortisol elaboration and diminished insulin secretion in older patients may contribute to this age effect. 相似文献
89.
HY Song SI Park HY Jung SB Kim JH Kim SJ Huh TH Kim YK Kim S Park HK Yoon KB Sung YI Min 《Canadian Metallurgical Quarterly》1997,203(3):747-752
PURPOSE: To evaluate the clinical effectiveness of a polyurethane-covered, retrievable, self-expandable metallic stent and hook catheter in the treatment of esophageal strictures. MATERIALS AND METHODS: Stents were constructed of 0.4-mm stainless steel wire in a cylindric zig-zag configuration of six to nine bends. Four to eight stents were connected in tandem by dipping in a polyurethane solution. A nylon loop was hooked inside to each bend of the proximal portion of the stent and strung with a thread. Under fluoroscopic guidance, 22 stents were placed in 16 patients with a malignant stricture and five patients with a benign stricture. The stent was removed with a hook catheter 2 months after placement in patients with a benign stricture and when complications occurred in patients with a malignant stricture. All patients had dysphagia with ingestion of soft foods or liquids. RESULTS: Stent placement was technically successful and well tolerated in 20 patients. In one patient, the stent was misplaced but relocated successfully. After stent placement, all patients were able to ingest solid and/or soft foods without dysphagia. After stent removal, strictures showed improvement but recurred in two patients. CONCLUSION: Use of polyurethane-covered, retrievable expandable stents seems to be a feasible and effective method of treatment of benign and malignant esophageal strictures. 相似文献
90.
Increasing the contrast of just one eye's image degrades stereothresholds; this phenomenon is referred to as the stereo contrast paradox. In experiment one, this paradox was found to be absent in dynamic random-element stereograms; thresholds were simply limited by the lower of the two eyes' contrasts. In experiment two, in which narrowband Gabor targets were used, the paradox was found to be strongest at relatively low spatial frequencies (1 cycle deg-1). As spatial frequency was increased, the paradox gradually disappeared. At relatively high spatial frequencies (5 cycles deg-1), thresholds were generally limited by the lower of the two eyes' contrasts, as was found for the dynamic noise targets. These results demonstrate the interactions of spatial frequency and contrast in binocular image combination and yield clues as to the different roles which high and low spatial frequencies may play in stereopsis. 相似文献