全文获取类型
收费全文 | 3489篇 |
免费 | 94篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 34篇 |
综合类 | 4篇 |
化学工业 | 448篇 |
金属工艺 | 52篇 |
机械仪表 | 105篇 |
建筑科学 | 235篇 |
矿业工程 | 4篇 |
能源动力 | 60篇 |
轻工业 | 320篇 |
水利工程 | 53篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 259篇 |
一般工业技术 | 576篇 |
冶金工业 | 893篇 |
原子能技术 | 35篇 |
自动化技术 | 497篇 |
出版年
2021年 | 51篇 |
2020年 | 37篇 |
2019年 | 54篇 |
2018年 | 45篇 |
2017年 | 54篇 |
2016年 | 68篇 |
2015年 | 55篇 |
2014年 | 78篇 |
2013年 | 198篇 |
2012年 | 152篇 |
2011年 | 168篇 |
2010年 | 145篇 |
2009年 | 139篇 |
2008年 | 186篇 |
2007年 | 162篇 |
2006年 | 127篇 |
2005年 | 123篇 |
2004年 | 80篇 |
2003年 | 96篇 |
2002年 | 84篇 |
2001年 | 52篇 |
2000年 | 56篇 |
1999年 | 63篇 |
1998年 | 166篇 |
1997年 | 117篇 |
1996年 | 90篇 |
1995年 | 62篇 |
1994年 | 80篇 |
1993年 | 52篇 |
1992年 | 36篇 |
1991年 | 23篇 |
1990年 | 41篇 |
1989年 | 42篇 |
1988年 | 37篇 |
1987年 | 30篇 |
1986年 | 39篇 |
1985年 | 36篇 |
1984年 | 49篇 |
1983年 | 35篇 |
1982年 | 34篇 |
1981年 | 26篇 |
1980年 | 34篇 |
1979年 | 23篇 |
1978年 | 27篇 |
1977年 | 27篇 |
1976年 | 49篇 |
1975年 | 24篇 |
1974年 | 31篇 |
1973年 | 21篇 |
1972年 | 14篇 |
排序方式: 共有3584条查询结果,搜索用时 31 毫秒
61.
Lewis R. Blackburn Shi-Kuan Sun Laura J. Gardner Ewan R. Maddrell Martin C. Stennett Claire L. Corkhill Neil C. Hyatt 《Journal of the American Ceramic Society》2021,104(7):2937-2951
A series of zirconolite ceramics with composition CaZr1-xThxTi2O7 (Δx = 0.10) were reactively sintered at 1350°C for 20 h, in air (0 ≤ x ≤ 0.60) and 5% H2/N2 (0 ≤ x ≤ 0.40). A sample with composition corresponding to x = 0.20 was also produced by hot isostatic pressing (HIP) at 1300°C and 100 MPa for 4 hours. Th4+ immobilization was most readily achieved under oxidizing conditions, with Th4+ preferentially incorporated within a pyrochlore-structured phase in the range 0.10 ≤ x ≤ 0.50, yet formation of the zirconolite-4M polytype was not observed. We report the novel synthesis of single-phase pyrochlore with nominal composition CaZr0.40Th0.60Ti2O7 when targeting x = 0.60. Th4+ incorporation under reducing conditions produced a secondary Th-bearing perovskite, comprising 24.2 ± 0.6 wt% of the phase assemblage when targeting x = 0.40, alongside 8.8 ± 0.3 wt% undigested ThO2. Under reducing conditions, powder XRD data were consistent with zirconolite adopting the 3T polytype structure. The sample produced by HIP presented a nonequilibrium phase assemblage, yielding a major phase of zirconolite-2M alongside accessory Th4+-bearing phases ThTi2O6, ThO2, and perovskite. These data highlight the efficacy of Th4+ as a Pu4+ surrogate, with implications for the formation of Zr-stabilized Th-pyrochlore phases as matrices for waste with elevated Th4+ content. 相似文献
62.
Anshu Dubey Klaus Weide Dongwook Lee John Bachan Christopher Daley Samuel Olofin Noel Taylor Paul M. Rich Lynn B. Reid 《Software》2015,45(2):233-244
When developing a complex, multi‐authored code, daily testing on multiple platforms and under a variety of conditions is essential. It is therefore necessary to have a regression test suite that is easily administered and configured, as well as a way to easily view and interpret the test suite results. We describe the methodology for verification of FLASH, a highly capable multiphysics scientific application code with a wide user base. The methodology uses a combination of unit and regression tests and an in‐house testing software that is optimized for operation under limited resources. Although our practical implementations do not always comply with theoretical regression‐testing research, our methodology provides a comprehensive verification of a large scientific code under resource constraints.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
63.
Taneli Rantaharju Neil J. Mansfield Jussi M. Ala-Hiiro Thomas P. Gunston 《Ergonomics》2015,58(7):1071-1087
In this paper, alternative assessment methods for whole-body vibration and shocks are compared by means of 70 vibration samples measured from 13 work vehicles, deliberately selected to represent periods containing shocks. Five methodologies (ISO 2631-1:1997, BS 6841:1987, ISO 2631-5:2004, DIN SPEC 45697:2012 and one specified by Gunston [2011], ‘G-method’) were applied to the vibration samples. In order to compare different evaluation metrics, limiting exposures were determined by calculating times to reach the upper limit thresholds given in the methods. Over 10-fold shorter times to exposure thresholds were obtained for the tri-axial VDV (BS 6841) than for the dominant r.m.s. (ISO 2631-1) when exposures were of high magnitude or contained substantial shocks. Under these exposure conditions, the sixth power approaches (ISO 2631-5, DIN SPEC, G-method) are more stringent than a fourth power VDV method. The r.m.s. method may lead to misleading outcomes especially if a lengthy measurement includes a small number of severe impacts. In conclusion, methodologies produce different evaluations of the vibration severity depending on the exposure characteristics, and the correct method must be selected. 相似文献
64.
65.
Project information management research enables the efficient exchange of information, but does not effectively communicate process. Design process management research effectively communicates processes, but with methods too inefficient to be adopted in practice. The lack of methods for effective and efficient design process communication manifests as a struggle for Architecture, Engineering, and Construction industry professionals to: (1) collaborate within projects, (2) share processes between projects, and (3) understand processes across projects to strategically invest in improvement. These struggles motivate the paper’s first contribution: a research method for evaluating a design management methodology’s ability to effectively and efficiently communicate design processes. As a second contribution, this paper validates the Design Process Communication Methodology (DPCM). DPCM specifies elements and methods for exchanging and organizing digital information to support knowledge-intensive design processes. Cloud computing enables the operationalization of DPCM as a tool that enables interaction with a project’s information. Results from this operationalization demonstrate that designers employing DPCM accurately capture processes with little effort. When collaborating, improved process clarity and information consistency result in less rework, and positive iteration enables increased consideration of multi-disciplinary design trends. Designers share processes between project teams with fewer process mistakes. DPCM enables the understanding of processes providing more insights into the relationships between design integration and project performance; and more opportunities for strategic investment in improved processes. 相似文献
66.
Friday Njaya Katherine A. Snyder Daniel Jamu John Wilson Clive Howard-Williams Edward H. Allison Neil L. Andrew 《Journal of Great Lakes research》2011
Lake Chilwa produces between zero and 24,000 metric tons of fish per year, making it one of the most productive but variable lakes in Africa. The size of the lake varies seasonally and among years, sometimes drying completely. Its surrounding wetland and floodplain provide habitat for a diversity of birds and economically valuable grasses and reeds. When the lake has water, there is considerable activity on its shores and temporary fishing villages spring up. People move in and out of the lake basin in concert with these seasonal and longer term changes. This paper examines the environmental dynamics of Lake Chilwa and its surrounding wetlands, presents an overview of the socio-economic context of the area and discusses threats to this resilient system that might occur as a result of climate change. We conclude that management of Lake Chilwa must place the lake in the wider economic and ecological system in which it is situated. Ultimately, land-use practices within the basin present more of a threat to the resilience of the fishery and people's livelihoods than overfishing or a strict focus on the lake's resources. These perspectives present significant challenges to conventional fisheries governance. 相似文献
67.
68.
Mohammad H. S. Amin Neil G. Dickson Peter Smith 《Quantum Information Processing》2013,12(4):1819-1829
Most realistic solid state devices considered as qubits are not true two-state systems. If the energy separation of the upper energy levels from the lowest two levels is not large, then these upper states may affect the evolution of the ground state over time and therefore cannot be neglected. In this work, we study the effect of energy levels beyond the lowest two energy levels on adiabatic quantum optimization in a device with a double-well potential as the basic logical element. We show that the extra levels can be modeled by adding additional ancilla qubits coupled to the original logical qubits, and that the presence of upper levels has no effect on the final ground state. We also study the influence of upper energy levels on the minimum gap for a set of 8-qubit spin glass instances. 相似文献
69.
Sven Lautenbach Neil Graf Ralf Seppelt Michael Matthies 《Environmental Modelling & Software》2009,24(1):26-43
We developed a decision support system (DSS) for sustainable river basin management in the German Elbe catchment (~100,000 km2), called Elbe-DSS. The system integrates georeferenced simulation models and related data sets with a user friendly interface and includes a library function. Design and content of the DSS have been developed in close cooperation with end users and stakeholders. The user can evaluate effectiveness of management actions like reforestation, improvement of treatment plant technology or the application of buffer strips under the influence of external constraints on climate, demographic and agro-economic changes to meet water management objectives such as water quality standards and discharge control. The paper (i) describes the conceptual design of the Elbe-DSS, (ii) demonstrates the applicability of the integrated catchment model by running three different management options for phosphate discharge reduction (reforestation, erosion control and ecological-farming) under the assumption of regional climate change based on IPCC scenarios, (iii) evaluates the effectiveness of the management options, and (iv) provides some lessons for the DSS-development in similar settings. The georeferenced approach allows the identification of local inputs in sub-catchments and their impact on the overall water quality, which helps the user to prioritize his management actions in terms of spatial distribution and effectiveness. 相似文献
70.
Initial algebra semantics is one of the cornerstones of the theory of modern functional programming languages. For each inductive
data type, it provides a Church encoding for that type, a build combinator which constructs data of that type, a fold combinator which encapsulates structured recursion over data of that type, and a fold/build rule which optimises modular programs by eliminating from them data constructed using the buildcombinator, and immediately consumed using the foldcombinator, for that type. It has long been thought that initial algebra semantics is not expressive enough to provide a similar
foundation for programming with nested types in Haskell. Specifically, the standard folds derived from initial algebra semantics have been considered too weak to capture commonly occurring patterns of recursion
over data of nested types in Haskell, and no build combinators or fold/build rules have until now been defined for nested types. This paper shows that standard folds are, in fact, sufficiently expressive for programming with nested types in Haskell. It also defines buildcombinators and fold/build fusion rules for nested types. It thus shows how initial algebra semantics provides a principled, expressive, and elegant
foundation for programming with nested types in Haskell. 相似文献