全文获取类型
收费全文 | 974篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 33篇 |
金属工艺 | 4篇 |
机械仪表 | 4篇 |
建筑科学 | 17篇 |
矿业工程 | 2篇 |
能源动力 | 10篇 |
轻工业 | 34篇 |
水利工程 | 1篇 |
无线电 | 22篇 |
一般工业技术 | 22篇 |
冶金工业 | 789篇 |
自动化技术 | 37篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 8篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 34篇 |
2001年 | 34篇 |
2000年 | 12篇 |
1999年 | 26篇 |
1998年 | 217篇 |
1997年 | 109篇 |
1996年 | 77篇 |
1995年 | 48篇 |
1994年 | 29篇 |
1993年 | 38篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 10篇 |
1984年 | 3篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 22篇 |
1976年 | 56篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1968年 | 2篇 |
1955年 | 3篇 |
排序方式: 共有979条查询结果,搜索用时 265 毫秒
91.
92.
IM Zonneveld WK Bakker PF Dijkstra JD Bos RM van Soesbergen HJ Dinant 《Canadian Metallurgical Quarterly》1996,132(2):184-187
OBJECTIVES: Herein we describe an additional case of myelolipoma of the adrenal gland, an uncommon tumor of the adrenal cortex, that had been incidentally discovered during abdominal US evaluation of the biliary tree. The clinical features, diagnosis and treatment of the condition are discussed. METHODS: Surgical treatment of the biliary tree and myelolipoma was performed through a Chevron transversal incision during the same surgical session. RESULTS: Surgery achieved good results and the postoperative course was unremarkable. CONCLUSIONS: Myelolipoma is a benign nonfunctioning tumor of the adrenal cortex comprised of adipose and hematopoietic tissue. It is usually asymptomatic and incidentally discovered during diagnostic evaluation for other pathologies. The diagnosis is made by US, CT and MRI. There is no agreement on whether surgical treatment is warranted. 相似文献
93.
Voltage-dependent anion channels (VDACs) are pore-forming proteins found in the outer mitochondrial membrane of all eucaryotes. VDACs are the major pathway for metabolites through the outer mitochondrial membrane and, in mammals, bind several cytosolic carbohydrate kinases. Whereas yeast contain a single VDAC (YVDAC), to date three isoforms have been described in the mouse that constitute a gene family. We have observed an additional isoform of VDAC3 that appears to be generated via the tissue-specific alternative splicing of a 3-base exon (ATG). The exon is predicted to introduce a methionine 39 amino acids downstream of the amino terminus of the polypeptide. Between exons 3 and 4 is an intronic sequence that potentially encodes the exon, with flanking splice enhancer elements. Expression of this alternative form in the mouse is limited to brain, heart, and skeletal muscle. Complementation of YVDAC-deficient yeast by the two isoforms and with other sequence variants of VDAC3 suggests this residue is an important modulator of VDAC3 function. In transfected mammalian cells both isoforms localize to mitochondria. A similar variant is present in humans. 相似文献
94.
WK Wang T Dudek YJ Zhao HG Brumblay M Essex TH Lee 《Canadian Metallurgical Quarterly》1998,95(10):5740-5745
The seven-transmembrane CCR5 was recently found to double as a coreceptor for a genetically diverse family of human and nonhuman primate lentiviruses. Paradoxically, the main region of the envelope protein believed to be involved in CCR5 utilization was mapped to hypervariable region 3, or V3, of the envelope glycoprotein gp120. In this study, we addressed the question of whether functional convergence in CCR5 utilization is mediated by certain V3 residues that are highly conserved among HIV type 1 (HIV-1), HIV type 2, and simian immunodeficiency virus. Site-directed mutagenesis carried out on three such V3 residues revealed that the Arg-298 of HIV-1 gp120 has an important role in CCR5 utilization. In contrast, no effect was observed for the other residues we tested. The inability of Arg-298 mutants to use CCR5 was not attributed to global alteration of gp120 conformation. Neither the expression, processing, and incorporation of mutant envelope proteins into virions, nor CD4 binding were significantly affected by the mutations. This interpretation is further supported by the finding that alanine substitutions of five residues immediately adjacent to the arginine residue had no effect on CCR5 utilization. Taken together, our data strongly suggests that the highly conserved Arg-298 residue identified in the V3 of HIV-1 has a significant role in CCR5 utilization, and may represent an unusually conserved target for future anti-viral designs. 相似文献
95.
Sonography and quantitative measurements 总被引:1,自引:0,他引:1
Jorgensen C.S. Knauss D. Hager H. Briggs G.A.D. 《IEEE engineering in medicine and biology magazine》1996,15(1):35-41
A preliminary study of coronary artery wall topography and mechanical properties is presented. The aim of this study was to give a brief demonstration of scanning acoustic microscopy (SAM) as a sonographic technique, and to apply the time-resolved SAM (TR-SAM) technique for quantification of coronary artery wall mechanical properties under passive conditions ex-vivo, and compare the data for the tunica externa and tunica media of the wall. The authors chose the diagonal branches of the left anterior descending coronary artery (LADCA) of young healthy pigs for measurements. It is concluded that SAM is well suited for sonography at the micrometer level, and TR-SAM provides a refined tool for biorheological quantification ex-vivo, provided that a number of physical factors influencing measurements and tissue properties are considered and dealt with. With time and effort, SAM may also become a valuable tool for recognizing important relations of composition and structure to function. For future SAM studies of arteries, more detailed analyses of layer interfaces and better models of biorheology should be applied to describe the anisotropy and nonlinear viscoelasticity of the wall 相似文献
96.
OBJECTIVE: To study the hemorheological effects of Sini decoction on patients following percutaneous transluminal coronary angioplasty (PTCA). METHODS: Forty-six patients were randomly divided into Sini decoction and control groups. The hemorheologic variables were determined before and after Sini decoction treatment. RESULTS: No hemorheologic changes were observed in the patients (n = 23) only with PTCA, but the patients (n = 23) with Sini decoction were found to be significantly decreased in whole blood viscosity and red cell aggregation and dredging the blood of microcirculation as post-PTCA compared to pre-PTCA. CONCLUSION: Sini decoction could improve the patient's hemorheology. 相似文献
97.
DS Bansi M Bauducci A Bergqvist K Boberg U Broome R Chapman K Fleming R Jorgensen K Lindor F Rosina E Schrumpf 《Canadian Metallurgical Quarterly》1997,9(6):575-580
SSCP (single-strand conformational polymorphism) is used widely in the field of human biomedicine, but its potential as a population genetics tool for the recovery of nuclear gene genealogies remains to be realized. We describe and illustrate a use for SSCP in the physical isolation of nuclear haplotypes that circumvents several difficulties associated with more conventional cloning procedures. The DNA sequence can be determined directly from the isolated haplotypes and used for phylogenetic inference. SSCP provides a convenient first step toward generating nuclear genealogies for population studies. 相似文献
98.
This article presents seven guidelines for producing realistic software development effort estimates. The guidelines derive from industrial experience and empirical studies. While many other guidelines exist for software effort estimation, these guidelines differ from them in three ways: 1) They base estimates on expert judgments rather than models. 2) They are easy to implement. 3) They use the most recent findings regarding judgment-based effort estimation. Estimating effort on the basis of expert judgment is the most common approach today, and the decision to use such processes instead of formal estimation models shouldn't be surprising. Simple process changes such as reframing questions can lead to more realistic estimates of software development efforts. 相似文献
99.
Thomas Fend Bernhard Hoffschmidt Gary Jorgensen Harald Küster Dirk Krüger Robert Pitz-Paal Peter Rietbrock Klaus-Jürgen Riffelmann 《Solar Energy》2003,74(2):149-155
This paper reports results from long-term durability tests of reflector materials to be used for solar concentrating systems. The studies have been conducted under the auspices of an IEA–SolarPACES collaboration between the National Renewable Energy Laboratory (NREL, USA), the Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT, Spain) and Deutsches Zentrum für Luft- und Raumfahrt (DLR, Germany). In this co-operative effort, accelerated ageing tests as well as outdoor exposures at a number of test sites having various climatic conditions have been carried out since 1995. In addition to materials already in use at solar power stations, newer materials offering the chance of a significant cost reduction in solar electricity and process heat generation are being investigated. Comparative optical tests are carried out to assess the efficiency as a function of exposure/service time in a solar concentrator. Among the materials showing promise for long-term outdoor applications are various silvered glass mirrors, a silvered polymer film, and an anodized sheet aluminium having an additional protective polymer coating. In addition to durability tests of reflector material samples, practical results are also reported for experiences with field applications of silvered thin glass and anodized sheet aluminium mirrors. 相似文献
100.