全文获取类型
收费全文 | 702篇 |
免费 | 39篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 164篇 |
金属工艺 | 5篇 |
机械仪表 | 17篇 |
建筑科学 | 24篇 |
矿业工程 | 2篇 |
能源动力 | 51篇 |
轻工业 | 45篇 |
水利工程 | 15篇 |
无线电 | 69篇 |
一般工业技术 | 171篇 |
冶金工业 | 62篇 |
原子能技术 | 5篇 |
自动化技术 | 97篇 |
出版年
2023年 | 16篇 |
2022年 | 14篇 |
2021年 | 34篇 |
2020年 | 24篇 |
2019年 | 19篇 |
2018年 | 31篇 |
2017年 | 33篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 23篇 |
2013年 | 45篇 |
2012年 | 32篇 |
2011年 | 39篇 |
2010年 | 32篇 |
2009年 | 35篇 |
2008年 | 33篇 |
2007年 | 27篇 |
2006年 | 31篇 |
2005年 | 32篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 5篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有744条查询结果,搜索用时 203 毫秒
51.
T. Karthikeyan Arup Dasgupta S. Saroja M. Vijayalakshmi 《Journal of Materials Engineering and Performance》2005,14(2):241-248
The successful replacement of the present generation of corrosion-resistant materials (nitric acid-grade stainless steel and
Ti) by Ti-5Ta-1.8Nb, which has better corrosion resistance, depends on its weldability characteristics. This article presents
the results of a study on the fabrication, qualification, and microstructural characterization of the welds. Welding was carried
out using the direct current electrode negative (DCEN) polarity tungsten inert gas (TIG) (manual) welding method with high-purity
Ar shielding. Testing was carried out as per the ASME standard (section IX, welding and brazing). Qualification tests found
that the weldment met the required properties. The weldment showed heterogeneous microstructures, which are rationalized based
on differences in phase transformation mechanisms that are dictated by the thermal cycles experienced by various microscopic
regions. The results, described in this article, confirm that the weldability of the developmental Ti-Ta-Nb alloy is excellent.
A preliminary evaluation of the corrosion behavior of the welds showed rates comparable to that of the base metal, establishing
that this alloy could be considered as an alternative material for use in highly corrosive environments. 相似文献
52.
Nucleate boiling from a vertical glass capillary in a pool of water is investigated here. Electrical heating is provided with a wire passing concentrically through the center of the capillary, and a fast-response thermocouple at the lip of the capillary records the instants of bubble departure. Different lengths and diameters of capillaries are used in the experiments. The average frequency of bubbling is seen to increase with applied heat flux, the relation being linear in the initial stages. With the heat flux used as a bifurcation parameter, one-dimensional return maps of the time interval between successive bubble emission events are used to study the transitions from the periodic state. The first bifurcation from the periodic to a two-period state is observed to be due to lateral instability of the liquid film adhering to the capillary wall. Further bifurcations to period two and then to period three bubbling are also observed. Simplified analysis of the different phases of the boiling process yields solutions which show close agreement with the experimental data. 相似文献
53.
Human placental RNase inhibitor (hRI), a leucine-rich repeat protein, binds the blood vessel-inducing protein human angiogenin (Ang) with extraordinary affinity (Ki <1 fM). Here we report a 2.0 A resolution crystal structure for the hRI-Ang complex that, together with extensive mutagenesis data from earlier studies, reveals the molecular features of this tight interaction. The hRI-Ang binding interface is large and encompasses 26 residues from hRI and 24 from Ang, recruited from multiple domains of both proteins. However, a substantial fraction of the energetically important contacts involve only a single region of each: the C-terminal segment 434-460 of hRI and the ribonucleolytic active centre of Ang, most notably the catalytic residue Lys40. Although the overall docking of Ang resembles that observed for RNase A in the crystal structure of its complex with the porcine RNase inhibitor, the vast majority of the interactions in the two complexes are distinctive, indicating that the broad specificity of the inhibitor for pancreatic RNase superfamily proteins is based largely on its capacity to recognize features unique to each of them. The implications of these findings for the development of small, hRI-based inhibitors of Ang for therapeutic use are discussed. 相似文献
54.
Compound parabolic concentrators (CPC) achieve highest possible concentration for any acceptance angle. One of the simplest methods of utilizing the energy of the sun to generate electric power is to use a CPC collector system. A truncated CPC can be used without much loss in concentration. Compared with a full CPC the cost of construction of a truncated CPC is much less. A CPC requires only seasonal adjustments. This further reduces the cost of tracking which is required for other types of concentrators. In this paper it has been shown that the refrigerants R11, R12, R113 and R114 can be satisfactorily used as working fluids in CPC collector systems. By using these working fluids, overall conversion efficiency of 9% can be achieved. Other refrigerants R12, B1, R22, R500, R502, R115 and C318 are found not to be suitable as they produce very low overall conversion efficiencies. In order to produce 20 kW of electricity at 1000 W/m2 insolation about 920 truncated CPC collectors (2 m length, 0.15 m aperture) with a concentration ratio of 8 are required. This minimum number of collectors would be required at an overall conversion efficiency of 9%. 相似文献
55.
This paper presents a model to allocate the repair efforts optimally between the individual unit and the subsystem contributing to the common cause failure of the system with a view to improving the overall system availability. It describes a general model to solve repair-effort decision problem for a redundant system with common-cause failures and three types of repair. The application of this model to a pulverizer system is also presented in this paper. 相似文献
56.
Mukherjee A. Ranganathan N. Flieder J. Acharya T. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1993,1(2):203-214
Describes the architecture and design of a CMOS VLSI chip for data compression and decompression using tree-based codes. The chip, called MARVLE, implements a memory-based architecture for variable length encoding and decoding based on tree-based codes. The architecture is based on an efficient scheme of mapping the tree representing any binary code onto a memory device. A prototype 2-mm CMOS VLSI chip has been designed, verified, and fabricated by the MOSIS facility. The chip has a 512×12 static RAM with an access time of 4 ns and logic circuitry for compression as well as decompression. The chip occupies a silicon area of 6.8 mm×6.9 mm and consists of 49695 transistors. The prototype chip yields a compression rate of 95.2 Mb/s and a decompression rate of 60.6 Mb/s with a clock rate of 83.3 MHz. The VLSI hardware can be used to implement the JPEG baseline compression scheme 相似文献
57.
DD Leonidas EH Vatzaki H Vorum JE Celis P Madsen KR Acharya 《Canadian Metallurgical Quarterly》1998,37(40):13930-13940
Knowledge about carbohydrate recognition domains of galectins, formerly known as S-type animal lectins, is important in understanding their role(s) in cell-cell interactions. Here we report the crystal structure of human galectin-7 (hGal-7), in free form and in the presence of galactose, galactosamine, lactose, and N-acetyl-lactosamine at high resolution. This is the first structure of a galectin determined in both free and carbohydrate-bound forms. The structure shows a fold similar to that of the prototype galectins -1 and -2, but has greater similarity to a related galectin molecule, Gal-10. Even though the carbohydrate-binding residues are conserved, there are significant changes in this pocket due to shortening of a loop structure. The monomeric hGal-7 molecule exists as a dimer in the crystals, but adopts a packing arrangement considerably different from that of Gal-1 and Gal-2, which has implications for carbohydrate recognition. 相似文献
58.
A set of 30 concrete beams reinforced with carbon/epoxy FRP (fiber-reinforced plastic) and four reinforced with comparable size steel rebars were subjected to static bending tests. Adequate bond between the FRP and the concrete was obtained, due to the use of carbon fiber overwrap on the smooth pultruded FRP rods. With adequate bond, the large strain to failure (>2%) of the FRP determines the ductility and failure mode of the FRP reinforced beams. An analytical evaluation of the fracture energy in these experiments shows that there is ductility due to the large fraction of the total strain energy that is absorbed in the concrete, because of the formation of distributed cracking. Variations in overwrap configuration, addition of steel stirrups, addition of polypropylene fibers, and comparison with four beams reinforced with equivalent steel reinforcement were also analyzed. 相似文献
59.
60.
A wireless ATM system consists of a core network infrastructure that provides mobility support to end terminals and a wireless access link. This article outlines two schemes for supporting mobility of IP terminals in this network. In the first scheme, location management and handoff support is integrated within the ATM signaling and control framework (“mobile ATM”), and mobility is transparently supported at the IP layer by mobile ATM underneath. In the second approach, the IP protocol stack is directly executed on ATM switches (without an intermediate ATM signaling stack) using an IP switching technique called IPSOFACTO (IP Switching Over Fast ATM Cell Transport), and terminal mobility is supported via mobile IP 相似文献