全文获取类型
收费全文 | 1527篇 |
免费 | 63篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 53篇 |
化学工业 | 303篇 |
金属工艺 | 33篇 |
机械仪表 | 29篇 |
建筑科学 | 34篇 |
矿业工程 | 6篇 |
能源动力 | 35篇 |
轻工业 | 101篇 |
水利工程 | 24篇 |
石油天然气 | 8篇 |
无线电 | 258篇 |
一般工业技术 | 205篇 |
冶金工业 | 261篇 |
原子能技术 | 12篇 |
自动化技术 | 229篇 |
出版年
2023年 | 10篇 |
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 20篇 |
2016年 | 21篇 |
2015年 | 27篇 |
2014年 | 33篇 |
2013年 | 116篇 |
2012年 | 25篇 |
2011年 | 38篇 |
2010年 | 50篇 |
2009年 | 57篇 |
2008年 | 40篇 |
2007年 | 34篇 |
2006年 | 60篇 |
2005年 | 40篇 |
2004年 | 40篇 |
2003年 | 40篇 |
2002年 | 44篇 |
2001年 | 58篇 |
2000年 | 45篇 |
1999年 | 47篇 |
1998年 | 38篇 |
1997年 | 41篇 |
1996年 | 53篇 |
1995年 | 45篇 |
1994年 | 42篇 |
1993年 | 36篇 |
1992年 | 19篇 |
1991年 | 29篇 |
1990年 | 40篇 |
1989年 | 35篇 |
1988年 | 44篇 |
1987年 | 32篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 17篇 |
1975年 | 18篇 |
1972年 | 8篇 |
排序方式: 共有1591条查询结果,搜索用时 15 毫秒
1.
Juana Maria de Lourdes Medina-Contreras Patrick Mailloux-Salinas Juventino III Colado-Velazquez Norma Leticia Gomez Viquez Gómez-Viquez Rodrigo Velázquez-Espejel Ana del Carmen Susunaga-Notario David Julian Arias-Chávez Guadalupe Bravo 《Journal of the science of food and agriculture》2020,100(7):3212-3219
2.
P. L. Sun E. K. Cerreta G. T. Gray III J. F. Bingert 《Metallurgical and Materials Transactions A》2006,37(10):2983-2994
Commercial purity aluminum AA1050 was subjected to equal channel angular extrusion (ECAE) that resulted in an ultrafine-grained
(UFG) microstructure with an as-received grain size of 0.35 μm. This UFG material was then annealed to obtain microstructures
with grain sizes ranging from 0.47 to 20 μm. Specimens were compressed at quasi-static, intermediate, and dynamic strain rates
at temperatures of 77 and 298 K. The mechanical properties were found to vary significantly with grain size, strain rate,
and temperature. Yield stress was found to increase with decreasing grain size, decreasing temperature, and increasing strain
rate. The work hardening rate was seen to increase with increasing grain size, decreasing temperature, and increasing strain
rate. The influence of strain rate and temperature is most significant in the smallest grain size specimens. The rate of work
hardening is also influenced by strain rate, temperature, and grain size with negative rates of work hardening observed at
298 K and quasi-static strain rates in the smallest grain sizes and increasing rates of work hardening with increasing loading
rate and grain size. Work hardening behavior is correlated with the substructural evolution of these specimens. 相似文献
3.
Jack J. Domet III T.M. Rajkumar Domet III David Yen 《Information Systems Management》1994,11(4):39-45
The realization of digital multimedia's full business potential requires networking. This article discusses the value-added benefits to the corporation of networked multimedia as well as the choice of architectures and technologies needed to deliver multimedia networking solutions. 相似文献
4.
This paper examines the long-term impact of structural features and physical amenities on the residential satisfaction of renters in multifamily housing. A cumulative logit analysis of 7,206 rented multifamily units in the 2005 American Housing Survey indicates that features creating separated space (additional room, bathroom, garage/carport, or balcony/patio) were associated with significantly higher satisfaction, even when holding total unit area constant. Conversely, violation of space separation by noise intrusion through walls, floors, or ceilings created dramatically negative effects. Other amenities such as a fireplace, disposal, or dishwasher had no statistically significant impact. Tracking a cohort of 5,170 rented multifamily units from 1997 to 2005 revealed somewhat similar effects on the satisfaction trajectory of residents during this period. More bathrooms, bedrooms, and other rooms, as well as the presence of a balcony/patio were associated with satisfaction improvements. Analyzing cohort units undergoing modifications during the tracking period revealed that the addition of a bathroom or central air conditioning had the clearest impact on satisfaction, followed by the addition of a balcony/patio, other room, dishwasher, or garage/carport. 相似文献
5.
6.
Robert Hieb R. Kent Dybvig Claude W. Anderson III 《Higher-Order and Symbolic Computation》1994,7(1):83-109
Continuations have proven to be useful for implementing a variety of control structures, including exception handling facilities and breadth-first searching algorithms. However, traditional continuations are not useful in the presence of concurrency, because the notion of the rest of the computation represented by a continuation does not in general make sense. Traditional continuations can also be difficult to use in nonconcurrent settings, since their global nature is sometimes problematic. This article presents a new type of continuation, called asubcontinuation. Just as a traditional continuation represents the rest of a computation ¿from a given point in the computation, a subcontinuation represents the rest of asubcomputation ¿from a given point in the subcomputation. Subcontinuations may be used to control tree-structured concurrency by allowing nonlocal exits to arbitrary points in a process tree and allowing the capture of a subtree of a computation as a composable continuation for later use. In the absence of concurrency the localized control achievable with subcontinuations makes them more useful than traditional continuations. 相似文献
7.
An improved accelerated cable life test is described. Through the use of programmable logic controllers (PLCs), very precise and consistent control of the accelerated aging process has been achieved. A computer has been utilized to make continuous real-time acquisition and storage of key operating parameters possible. This precise control and monitoring methodology has permitted the study of the synergistic effects of voltage and temperature on the accelerated aging of full-sized cables in the laboratory 相似文献
8.
Inertia-friction welding of SiC-reinforced 8009 aluminium 总被引:2,自引:0,他引:2
T. J. Lienert W. A. Baeslack III J. Ringnalda H. L. Fraser 《Journal of Materials Science》1996,31(8):2149-2157
Inertia-drive friction welding (IFRW) of an 8009 Al alloy (Al-8.5 Fe-1.7 Si-1.3 V, wt%) reinforced with 11 volume per cent SiC particles (8009/SiC/11p) has been investigated. Inertia-drive friction welds were made with constant energy at two levels of axial force. The microstructures of the base material and the welds were characterized using optical and scanning electron microscopy, while the mechanical properties were evaluated using microhardness and tensile testing. Examination of weld sections revealed that the hot deformation experienced during welding produced a homogenized microstructure with a uniform distribution of SiC particles along the bond line. No evidence of a chemical reaction between the SiC and the matrix was found in any of the welds, but cracking of some of the larger SiC particles was observed in the base material as well as in the IFR welds. The average microhardness of the various heat-and-deformation affected zones (HDZs) of the welds did not vary greatly from that of the base material, and no weld induced weak regions were discerned. The room-temperature (RT) tensile strength of the IFR welds exceeded 90 per cent of the base material. The weld tensile specimens failed at the outer edge of the HDZ for all of the welds tested. The fracture surface of the 8009 matrix of tensile samples for both the base material and the welds exhibited a dimpled appearance indicating a ductile failure, while fracture through the SiC appeared to occur in a brittle fashion. IFRW has proven effective in joining 8009/SiC/11p with little loss in RT hardness and tensile properties. 相似文献
9.
10.
Gupta R. Hero A.O. III 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(8):1951-1969
We investigate high-rate quantization for various detection and reconstruction loss criteria. A new distortion measure is introduced which accounts for global loss in best attainable binary hypothesis testing performance. The distortion criterion is related to the area under the receiver-operating-characteristic (ROC) curve. Specifically, motivated by Sanov's theorem, we define a performance curve as the trajectory of the pair of optimal asymptotic Type I and Type II error rates of the most powerful Neyman-Pearson test of the hypotheses. The distortion measure is then defined as the difference between the area-under-the-curve (AUC) of the optimal pre-encoded hypothesis test and the AUC of the optimal post-encoded hypothesis test. As compared to many previously introduced distortion measures for decision making, this distortion measure has the advantage of being independent of any detection thresholds or priors on the hypotheses, which are generally difficult to specify in the code design process. A high-resolution Zador-Gersho type of analysis is applied to characterize the point density and the inertial profile associated with the optimal high-rate vector quantizer. The analysis applies to a restricted class of high-rate quantizers that have bounded cells with vanishing volumes. The optimal point density is used to specify a Lloyd-type algorithm which allocates its finest resolution to regions where the gradient of the pre-encoded likelihood ratio has greatest magnitude. 相似文献