全文获取类型
收费全文 | 969篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 130篇 |
金属工艺 | 22篇 |
机械仪表 | 16篇 |
建筑科学 | 34篇 |
矿业工程 | 2篇 |
能源动力 | 76篇 |
轻工业 | 87篇 |
水利工程 | 3篇 |
无线电 | 116篇 |
一般工业技术 | 155篇 |
冶金工业 | 245篇 |
原子能技术 | 10篇 |
自动化技术 | 70篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 17篇 |
2013年 | 27篇 |
2012年 | 23篇 |
2011年 | 43篇 |
2010年 | 19篇 |
2009年 | 41篇 |
2008年 | 33篇 |
2007年 | 44篇 |
2006年 | 39篇 |
2005年 | 40篇 |
2004年 | 44篇 |
2003年 | 40篇 |
2002年 | 35篇 |
2001年 | 31篇 |
2000年 | 25篇 |
1999年 | 19篇 |
1998年 | 93篇 |
1997年 | 53篇 |
1996年 | 58篇 |
1995年 | 20篇 |
1994年 | 32篇 |
1993年 | 14篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1970年 | 3篇 |
1968年 | 1篇 |
排序方式: 共有978条查询结果,搜索用时 15 毫秒
41.
Technical solutions for the 3G long-term evolution 总被引:7,自引:0,他引:7
Ekstrom H. Furuskar A. Karlsson J. Meyer M. Parkvall S. Torsner J. Wahlqvist M. 《Communications Magazine, IEEE》2006,44(3):38-45
Work has started in the 3GPP to define a long-term evolution for 3G, sometimes referred to as super-3G, which will stretch the performance of 3G technology, thereby meeting user expectations in a 10-year perspective and beyond. The fundamental targets of this evolution - to further reduce user and operator costs and to improve service provisioning - will be met through improved coverage and system capacity as well as increased data rates and reduced latency. This article presents promising technologies to fulfil these targets, including OFDM, multi-antenna solutions, evolved QoS and link layer concepts, and an evolved architecture. Furthermore, the results of a performance evaluation are presented, indicating that the requirements can indeed be reached using the proposed technologies. 相似文献
42.
A Karlsson S Mesnildrey Y Xu S Moréra J Janin M Véron 《Canadian Metallurgical Quarterly》1996,271(33):19928-19934
NDP kinase from Dictyostelium was mutated by site-directed mutagenesis at positions indicated by structural data to be involved in the trimer interface. The mutants were substitutions at residue Pro-100 (P100S and P100G) and deletions of 1-5 residues at the C terminus. Single mutants yielded proteins that kept both activity and hexameric structure. However, they were severely affected in their stability toward temperature and urea denaturation. When the P100S mutation was combined with any of the C-terminal deletions, the enzyme lost most of its activity and dissociated into dimers. Crystallographic analysis of the P100S protein was performed at 2.6 A resolution. The x-ray structure showed no direct alteration of intersubunits contacts at residue 100, but an induced disruption of the interaction between Asp-115 and the C terminus of another subunit. The substitution of proline 100 to serine corresponds to the Killer-of-prune mutation in Drosophila. Consequences of the mutation are discussed in view of the structural and biochemical properties observed in the mutant Dictyostelium protein. 相似文献
43.
GB Karlsson M Halloran D Schenten J Lee P Racz K Tenner-Racz J Manola R Gelman B Etemad-Moghadam E Desjardins R Wyatt NP Gerard L Marcon D Margolin J Fanton MK Axthelm NL Letvin J Sodroski 《Canadian Metallurgical Quarterly》1998,188(6):1159-1171
CD4+ T lymphocyte depletion in human immunodeficiency virus type 1 (HIV-1)-infected humans underlies the development of acquired immune deficiency syndrome. Using a model in which rhesus macaques were infected with chimeric simian-human immunodeficiency viruses (SHIVs), we show that both the level of viremia and the structure of the HIV-1 envelope glycoprotein ectodomains individually contributed to the efficiency with which CD4(+) T lymphocytes were depleted. The envelope glycoproteins of recombinant SHIVs that efficiently caused loss of CD4(+) T lymphocytes exhibited increased chemokine receptor binding and membrane-fusing capacity compared with those of less pathogenic viruses. These studies identify the HIV-1 envelope glycoprotein ectodomains as determinants of CD4(+) T lymphocyte loss in vivo and provide a foundation for studying pathogenic mechanisms. 相似文献
44.
Dimensional analysis is applied to one form of fire growth in a compartment to derive two indices for the classification of linings, an ignitability index and a rate of heat release index, that can be combined into a fire growth parameter, which here is made proportional to the time to flashover in the internationally standardized Room/Corner Test. The ignitability index is the inverse of the time to ignition. The rate of heat release index is obtained by integrating the rate of heat release in time, weighted in such a way that the values of rate of heat release immediately after ignition are of higher importance than those at later times. Both indices are determined from test results of the Cone Calorimeter. 相似文献
45.
KA Thomsson I Carlstedt NG Karlsson H Karlsson GC Hansson 《Canadian Metallurgical Quarterly》1998,15(8):823-833
The O-linked oligosaccharides from three fractions of highly glycosylated mucin glycopeptides obtained from sputum of a patient with cystic fibrosis were characterized and compared regarding size, composition, sequence and when possible linkage positions. Neutral and sialic acid-containing glycans were permethylated and analyzed by high-temperature GC-MS and MALDI-MS, showing more than 60 different oligosaccharides with a size of up to 15 monosaccharide units. Some of the observed oligosaccharides are novel for respiratory secretions, one being a trifucosylated heptasaccharide with the proposed structure: Fuc-Gal-4(Fuc-3)GlcNAc-(Fuc-)Gal-3GalNAcol. The glycosylation of two of the glycopeptide fractions was similar with regard to the neutral and sialylated oligosaccharides despite their different origins from the sol or gel phase. Analysis of the sulfated oligosaccharides by FAB-MS/MS indicated that the gel fraction contained C-6 linked sulfate groups while the two sol fractions also contained C-3 linked sulfate. The results suggest the presence of different glycosylated mucin domains, probably originating from different mucin glycoforms and/or apoproteins in the airway of cystic fibrosis patients. 相似文献
46.
47.
Consumer and sensory investigations in relation to physical/chemical aspects of cooked pork in Scandinavia 总被引:1,自引:0,他引:1
Bryhni EA Byrne DV Rødbotten M Møller S Claudi-Magnussen C Karlsson A Agerhem H Johansson M Martens M 《Meat science》2003,65(2):737-748
The present study addresses sensory quality and liking for pork (eight samples) varying in quality due to adrenaline injection resulting in elevated ultimate pH post-slaughter (24h), meat ageing, cooking temperature and warmed-over flavour (WOF) among consumers (n=288) in Scandinavia. The consumers preferred meat with higher pH (pH(24h)=6.0), cooked to the lowest temperature (65?°C versus 80?°C). Consumers least preferred samples with WOF described as metallic, acidic and off-flavour by a trained panel. "Elevated pH(24h) meat" cooked to 65?°C resulted in a more sweet and tender meat. Juiciness, tenderness and the absence of off-flavour were the most important characteristics for consumers' liking of pork. Consumption frequency and liking of pork were positively related. The consumers that were most satisfied with pork quality reported highest consumption frequency. Elderly people and males expressed the highest liking score and consumption frequency, respectively. 相似文献
48.
49.
Nolkrantz K Farre C Brederlau A Karlsson RI Brennan C Eriksson PS Weber SG Sandberg M Orwar O 《Analytical chemistry》2001,73(18):4469-4477
We show how an electrolyte-filled capillary (EFC) coupled to a high-voltage power supply can be used as a versatile electroporation tool for the delivery of dyes, drugs, and biomolecules to the cytoplasm of single cells and cells in tissues. A large-voltage pulse applied across the EFC (fused silica, 30 cm long, 375-microm o.d., 30-microm i.d.) gives rise to a small electric field outside the terminus of the EFC, which causes pore formation in cell membranes and induces an electroosmotic flow of electrolyte. When the EFC contains cell-loading agents, then the electroosmotic flow delivers the agents at the site of pore formation. The combination of pore formation and delivery enables loading of materials into the cytoplasm. By patch-clamp and fluorescence microscopy, formation of pores was observed at estimated transmembrane voltages of <85 mV with half-maximum values around 206 mV. The electroporation protocol was demonstrated by introduction of fluorogenic dyes into single NG108-15 cells, cellular processes, and small populations of cells in organotypic hippocampal cultures. Preliminary results are shown in which this protocol was employed for in vivo electroporation of ventral mesencephalon in rat brains. The technique was also used to access organelle-based detection systems inside cells. As a demonstration, 1,4,5-inositoltriphosphate was added to the electrolyte and detected by intracellular organelles in electroporated cells. 相似文献
50.
This paper analyzes the role of knowledge in regional economic growth by focusing on knowledge accessibility. The research question is the following: can the variation in knowledge accessibility between regions in a given period explain the variation in growth performance of regions in subsequent periods? A main assumption in the paper is that knowledge accessibility transforms into potential knowledge flows. Our results show that differences in growth of value-added per employee across regions can be explained by differences in knowledge accessibility. Intra-municipal and intra-regional knowledge accessibilities are significant and capable of explaining a significant share of the variation in growth of value-added per employee between Swedish municipalities. However, inter-regional knowledge accessibility turned out to be insignificant. This is interpreted as a clear indication of spatial dependence in the sense that the knowledge resources in a given municipality tend to have a positive effect on the growth of other municipalities, conditional on that the municipalities belong to the same functional region. Thus, the results of the analysis indicate that knowledge flows transcend municipal borders, but that they tend to be bound within functional regions. 相似文献