全文获取类型
收费全文 | 5938篇 |
免费 | 243篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 65篇 |
综合类 | 4篇 |
化学工业 | 1158篇 |
金属工艺 | 111篇 |
机械仪表 | 132篇 |
建筑科学 | 196篇 |
矿业工程 | 29篇 |
能源动力 | 131篇 |
轻工业 | 572篇 |
水利工程 | 85篇 |
石油天然气 | 10篇 |
无线电 | 402篇 |
一般工业技术 | 1015篇 |
冶金工业 | 1517篇 |
原子能技术 | 42篇 |
自动化技术 | 717篇 |
出版年
2023年 | 32篇 |
2022年 | 52篇 |
2021年 | 91篇 |
2020年 | 70篇 |
2019年 | 104篇 |
2018年 | 105篇 |
2017年 | 96篇 |
2016年 | 123篇 |
2015年 | 95篇 |
2014年 | 138篇 |
2013年 | 311篇 |
2012年 | 249篇 |
2011年 | 350篇 |
2010年 | 260篇 |
2009年 | 239篇 |
2008年 | 310篇 |
2007年 | 300篇 |
2006年 | 249篇 |
2005年 | 223篇 |
2004年 | 185篇 |
2003年 | 167篇 |
2002年 | 164篇 |
2001年 | 131篇 |
2000年 | 115篇 |
1999年 | 105篇 |
1998年 | 208篇 |
1997年 | 158篇 |
1996年 | 147篇 |
1995年 | 121篇 |
1994年 | 88篇 |
1993年 | 105篇 |
1992年 | 106篇 |
1991年 | 49篇 |
1990年 | 76篇 |
1989年 | 80篇 |
1988年 | 62篇 |
1987年 | 72篇 |
1986年 | 49篇 |
1985年 | 50篇 |
1984年 | 59篇 |
1983年 | 49篇 |
1982年 | 47篇 |
1981年 | 55篇 |
1980年 | 49篇 |
1979年 | 32篇 |
1978年 | 29篇 |
1977年 | 29篇 |
1976年 | 49篇 |
1974年 | 23篇 |
1973年 | 21篇 |
排序方式: 共有6186条查询结果,搜索用时 687 毫秒
31.
32.
Robert G. Whirley Gregory A. Henshall 《International journal for numerical methods in engineering》1992,35(7):1427-1442
This paper presents a fast numerical algorithm for the implementation of material models for creep into finite element codes. First, an overview of existing algorithms for transient and steady-state creep is given. Next, a new formulation is presented which reduces the constitutive integration to the solution of a scalar non-linear algebraic equation. A solution is shown to exist without the need for subincrementation. Details of the numerical algorithm are then discussed. The paper closes with several numerical examples which illustrate the speed, robustness and accuracy of the proposed procedure as implemented in the Lawrence Livermore National Laboratory finite element codes NIKE2D and NIKE3D. 相似文献
33.
34.
Multitrait restricted maximum likelihood methods were used for estimation of heritabilities and genetic and phenotypic correlations between calving ease and calf survival. These analyses examined both direct and maternal effects. Genetic correlation for direct effects between calving ease and calf survival was approximately -.8 in both heifers and cows, indicating favorable associations, whereas phenotypic correlations were -.32 and -.22. 相似文献
35.
Ming-Ching Lee Chan-Ji Lai Jan-Mou Leu William J. Plant William C. Keller Ken Hayes 《Flow Measurement and Instrumentation》2002,13(5-6):265-270
This article describes a non-contact method for measuring surface velocity and discharge in a natural channel. The X-band pulse (9.36 GHz) radar, developed by the Applied Physics Laboratory of the University of Washington, was used to scan instantaneously the lateral distribution of surface velocity across a river section, according to Bragg scattering from short waves produced by turbulent boils on the surface of the river. Based on the assumption that the vertical velocity distribution follows a universal power or logarithmic law, the discharges were estimated. 相似文献
36.
A new online streaming video and multi‐media application called eTEACH, http:eTEACH.engr.wisc.edu was used to reform a large, lecture‐based computer science course for engineering majors. In‐class lectures were replaced with videotaped lectures and other materials that students viewed on the Internet on their own schedule, making it possible to use the live class periods for small, team problem‐solving sessions facilitated by the professors and a teaching assistant. By using the eTEACH application to transform course lectures into “homework” and free up the face‐to‐face class time for working on problems that were similar to homework assignments, the professors effectively reversed the lecture and homework paradigm of a typical large lecture course. A thorough course evaluation over two semesters showed that students who took the online lecture version of the course gave significantly higher ratings to all aspects of the course, including lecture usefulness, professor responsiveness, the course overall, and the instructor. Although a few students missed having the opportunity to ask questions during lectures, about two‐thirds of the 531 students surveyed felt it was easier to take notes and understand the lectures presented via eTEACH than it would have been while attending the same lecture live, and 78% of students appreciated the ability to view and review course lectures on their own schedule. 相似文献
37.
38.
Experimental studies on phase equilibria in the multicomponent system PbO-ZnO-CaO-SiO2-FeO-Fe2O3 in air have been conducted to characterize the phase relations of a complex slag system used in commercial lead oxidation
smelting. The liquidus in the pseudo-ternary section ZnO-“Fe2O3”-(PbO + CaO + SiO2) with the CaO/SiO2 weight ratio of 0.35 and the PbO/(CaO + SiO2) weight ratio of 5.0 has been constructed using results of over 100 high-temperature equilibration and quenching experiments
followed by electron probe X-ray microanalysis. The liquidus in this pseudoternary section contains primary phase fields of
spinel (zinc ferrite) Zn
x
Fe3−x
O4+y
, zincite Zn
u
Fe1−u
O, melilite Pb
v
Ca2−v
Zn
w
Fe1−w
Si2O7, hematite Fe2O3, magneto-plumbite PbFe10O16, and dicalcium silicate Ca2−t
Pb
t
SiO4. The laboratory results are compared with the slags obtained from an industrial reactor. 相似文献
39.
Boeing has been working on the development and implementation of STEP AP 210 since its inception. Using a combination of internally funded activities, external government contracts and multi-company pilots, Boeing has developed prototype tools to utilize AP 210 and is poised to move these tools into production. This paper begins with a brief overview of STEP and AP 210. The status of available AP 210 vendor translators (data generators), along with viewers and analysis programs (data consumers) is covered. Discussion continues with present and planned usage of AP 210 in several companies with the primary emphasis on implementation at The Boeing Company. The document concludes with a summary of key points. 相似文献
40.
The processing of images obtained from satellites often involves highly repetitive calculations on very large amounts of data. This processing is extremely time consuming when these calculations are performed on sequential machines. Parallel computers are well suited to handling computationally expensive operations such as higher order interpolations on large data sets. This paper decribes work undertaken to develop parallel implementations of a set of resampling procedures on an Alliant VFX/4. Each resampling procedure implemented has been optimised in three stages. First, the algorithm has been restructured, where two-dimensional resampling is performed by two one-dimensional resampling operations. Second, each procedure has been reprogrammed in such a way that the autoparallelisation provided by the FX/Fortran compiler has been exploited. Thirdly, data dependent analysis of each procedure has been performed in order to achieve full optimization of each procedure; each procedure has been restructured where appropriate to circumvent vectorisation and concurrency inhibiting data dependencies. The nature and extent of the code optimization achieved for each procedure is presented in this paper. The original code for the most computationally expensive procedure, as targeted at a sequential machine, was found to have an execution time of 4900 seconds on the Alliant VFX/4 when compiled with regular compiler optimization options. Following algorithmic redesigning and reprogramming of the code, as indicated in stage 1 and stage 2, the execution time was reduced to 248 seconds. Restructuring of the code following data dependency analysis indicated in stage 3 in order to avoid data dependencies and allow concurrency and vectorisation, further reduced execution time to 162 seconds. The consequence of this work is that higher-order resampling methods which had not previous been practical are now routinely performed on the Alliant VFX/4 at the University of Dundee. 相似文献