全文获取类型
收费全文 | 1131篇 |
免费 | 58篇 |
专业分类
电工技术 | 47篇 |
综合类 | 4篇 |
化学工业 | 341篇 |
金属工艺 | 20篇 |
机械仪表 | 12篇 |
建筑科学 | 51篇 |
能源动力 | 50篇 |
轻工业 | 112篇 |
水利工程 | 12篇 |
无线电 | 65篇 |
一般工业技术 | 245篇 |
冶金工业 | 66篇 |
原子能技术 | 18篇 |
自动化技术 | 146篇 |
出版年
2023年 | 18篇 |
2022年 | 30篇 |
2021年 | 46篇 |
2020年 | 25篇 |
2019年 | 43篇 |
2018年 | 35篇 |
2017年 | 23篇 |
2016年 | 33篇 |
2015年 | 51篇 |
2014年 | 39篇 |
2013年 | 75篇 |
2012年 | 61篇 |
2011年 | 91篇 |
2010年 | 35篇 |
2009年 | 42篇 |
2008年 | 40篇 |
2007年 | 57篇 |
2006年 | 36篇 |
2005年 | 35篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 24篇 |
2001年 | 14篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 36篇 |
1997年 | 27篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1936年 | 2篇 |
1933年 | 6篇 |
1932年 | 5篇 |
1931年 | 11篇 |
1930年 | 3篇 |
1919年 | 2篇 |
1910年 | 2篇 |
排序方式: 共有1189条查询结果,搜索用时 15 毫秒
91.
In this paper we present a new method for the formal reduction of linear differential systems. We generalize classical results
and concepts and obtain new characterizations of existing notions. Our main result is a generalization of the classical Splitting
Lemma. This leads to an algorithm for computing formal invariants and solutions in a more efficient way.
Received: March 9, 1999; revised version: September 2, 1999 相似文献
92.
Bin Yang Craig R. Bradshaw Eckhard A. Groll 《International Journal of Refrigeration》2013,36(7):1925-1937
A comprehensive model for a semi-hermetic CO2 reciprocating compressor is presented. This comprehensive model is composed of three main sub-models simulating the geometry and kinematics, the compression process, and frictional power loss. Valve and leakage sub-models are included in the compression process model. The frictional power loss model includes the friction at the bearings and between the piston ring and cylinder wall. The predicted results of the comprehensive model are validated using external compressor performance measurements of compressor input power and mass flow rate. The mass flow rate and compressor input power are predicted to within 4.03% and 6.43% mean absolute error, respectively, compared to the experimental datum. Additionally, a parametric study is presented which investigates compressor performance as a function of the stroke-to-bore ratio. 相似文献
93.
Andreas Schmitz Christian Stiewe Eckhard Müller 《Journal of Electronic Materials》2013,42(7):1702-1706
Waste heat recovery—for example, in automotive applications—is a major field for thermoelectric research and future application. Commercially available thermoelectric modules are based on planar structures, whereas tubular modules may have advantages for integration and performance in the field of automotive waste heat recovery. One major drawback of tubular generator designs is the necessity for ring-shaped legs made from thermoelectric material. Cutting these geometries from sintered tablets leads to considerable loss of thermoelectric material and therefore high cost. Direct sintering of ring-shaped legs or tubes of thermoelectric material is a solution to this problem. However, sintering such rings with high homogeneity and density faces some difficulties related to the mechanical properties of typical thermoelectric materials such as lead telluride (PbTe)—particularly brittleness and high coefficient of thermal expansion. This work shows a process for production of thermoelectric rings made of p- and n-doped PbTe. Long tubes of PbTe have been sintered in a current-assisted sintering process with specially designed sintering molds, coated with a diffusion barrier, and finally cut into ring-shaped slices. To demonstrate the technology, a tubular thermoelectric module has been assembled using these PbTe rings. 相似文献
94.
95.
Pipilos S. Papananos Y. Naskas N. Zervakis M. Jakob Jongsma Gschier T. Wilson N. Gibbins J. Carter B. Dann G. 《Solid-State Circuits, IEEE Journal of》2005,40(3):707-718
A fully integrated linearized transmitter for the next generation TETRA systems for PMR and public safety applications in a CMOS-based SiGe technology is described. The presented single-chip transmitter employs a Cartesian feedback loop technique in order to improve the linearity of the externally connected power amplifier. The transmitter is usable in a frequency range from 300 MHz up to 800 MHz, providing a linearity improvement of more than 40 dB. 相似文献
96.
Key elements of present investment decision-making regarding energy efficiency of new buildings and the refurbishment of existing buildings are the marginal costs of energy efficiency measures and incomplete knowledge of investors and architects about pricing, co-benefits and new technologies. This paper reports on a recently completed empirical study for the Swiss residential sector. It empirically quantifies the marginal costs of energy efficiency investments (i.e. additional insulation, improved window systems, ventilation and heating systems and architectural concepts). For the private sector, first results on the economic valuation of co-benefits such as improved comfort of living, improved indoor air quality, better protection against external noise, etc. may amount to the same order of magnitude as the energy-related benefits are given. The cost–benefit analysis includes newly developed technologies that show large variations in prices due to pioneer market pricing, add-on of learning costs and risk components of the installers. Based on new empirical data on the present cost-situation and past techno-economic progress, the potential of future cost reduction was estimated applying the experience curve concept. The paper shows, for the first time, co-benefits and cost dynamics of energy efficiency investments, of which decision makers in the real estate sector, politics and administrations are scarcely aware. 相似文献
97.
Kathrin Eckhard 《Electrochimica acta》2007,53(3):1164-1169
Catalytic reduction of O2 at metal catalysts either follows a 2-electron transfer pathway to the formation of H2O2 or a 4-electron transfer pathway to the formation of H2O. The branching ratio of this reaction has a significant impact on the applicability of catalyst materials. The previously introduced oxygen competition mode of SECM, which allows high-resolution imaging of local O2 consumption, has been extended to a potential-pulse sequence enabling the sequential detection of O2 reduction followed by the detection of local H2O2 formation. Thus, not only the local catalytic activity of a catalyst can be visualised but, additionally, the degree of the branching can be estimated. The selectivity of a catalyst candidate can thereby be visualised sequentially to the elucidation of its activity. First results on the properties of electrodeposited Pt and Au test structures are shown demonstrating the feasibility to clearly distinguish catalyst activity and selectivity under variation of the polarisation potential. 相似文献
98.
99.
Thomas Bahners Uwe Schlosser Eckhard Schollmeyer 《Solar Energy Materials & Solar Cells》2008,92(12):1661-1667
Concepts of technical fibers following models for the polar bear hair to be used for textile solar collectors are discussed. The approach to coat fibers with a thin layer into which fluorescent dyestuff was dispersed was studied experimentally. Modified fibers made of different polymers were characterized with respect to optical properties relevant for the bionic model. In the case of poly(methylmethacrylate) fibers, the envisaged effect could be achieved to high efficiency. The optical performance could be enhanced by ultrasonic dispersion of the dyestuff in the coating matrix. The effect is less significant in semi-crystalline fibers such as poly(ethylene terephthalate), which is attributed to diffuse scattering. 相似文献
100.
A general approach for the fabrication of nanoporous Pt-based multimetallic alloy nanowires is reported, which involves electrodeposition of corresponding precursor alloys into porous anodic alumina templates, followed by a mild dealloying process. Nanoporous ternary PtCoNi and PtCoAu as well as quaternary PtRuCoNi nanowires were successfully fabricated, and their microstructure and composition were examined by transmission electron microscopy. Electrochemical tests showed that these porous nanowires exhibit higher electrochemically active surface area and much improved durability compared to commercially available Pt black, and may find potential applications in electrocatalysis and electrochemical sensing. 相似文献