全文获取类型
收费全文 | 45053篇 |
免费 | 5337篇 |
国内免费 | 3020篇 |
专业分类
电工技术 | 6405篇 |
技术理论 | 2篇 |
综合类 | 5062篇 |
化学工业 | 3414篇 |
金属工艺 | 852篇 |
机械仪表 | 2486篇 |
建筑科学 | 2622篇 |
矿业工程 | 945篇 |
能源动力 | 1014篇 |
轻工业 | 2194篇 |
水利工程 | 1210篇 |
石油天然气 | 765篇 |
武器工业 | 466篇 |
无线电 | 5461篇 |
一般工业技术 | 4358篇 |
冶金工业 | 1321篇 |
原子能技术 | 226篇 |
自动化技术 | 14607篇 |
出版年
2024年 | 189篇 |
2023年 | 560篇 |
2022年 | 1019篇 |
2021年 | 1290篇 |
2020年 | 1336篇 |
2019年 | 1331篇 |
2018年 | 1220篇 |
2017年 | 1606篇 |
2016年 | 1822篇 |
2015年 | 2031篇 |
2014年 | 3001篇 |
2013年 | 2885篇 |
2012年 | 3666篇 |
2011年 | 3948篇 |
2010年 | 3076篇 |
2009年 | 3156篇 |
2008年 | 2952篇 |
2007年 | 3369篇 |
2006年 | 2740篇 |
2005年 | 2202篇 |
2004年 | 1718篇 |
2003年 | 1466篇 |
2002年 | 1191篇 |
2001年 | 881篇 |
2000年 | 777篇 |
1999年 | 593篇 |
1998年 | 499篇 |
1997年 | 418篇 |
1996年 | 330篇 |
1995年 | 317篇 |
1994年 | 240篇 |
1993年 | 199篇 |
1992年 | 160篇 |
1991年 | 117篇 |
1990年 | 137篇 |
1989年 | 130篇 |
1988年 | 113篇 |
1987年 | 64篇 |
1986年 | 65篇 |
1985年 | 76篇 |
1984年 | 86篇 |
1983年 | 99篇 |
1982年 | 103篇 |
1981年 | 32篇 |
1980年 | 39篇 |
1979年 | 28篇 |
1978年 | 22篇 |
1977年 | 19篇 |
1976年 | 10篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 812 毫秒
91.
B. G. Clarke 《Canadian Metallurgical Quarterly》2007,133(2):107-115
This paper describes a module that was introduced into a civil engineering degree program with the help of professional engineers. The aim was to develop a bridge between the world of learning and professional practice by putting students in the role of consulting engineers working with industry to produce a feasible solution to a real inquiry from a client. The module is placed in context by comparing the goals of accredited civil engineering programs in the United Kingdom and America, by describing how it is linked to the degree program and by explaining the matrix developed to identify the skills the students needed to demonstrate their ability to practice as professional engineers. Details of the module are given with examples of student work and feedback. 相似文献
92.
Jules Sadefo Kamdem 《Computing and Visualization in Science》2007,10(4):197-210
In this paper, we generalize the Linear VaR method from portfolios with normally distributed risk factors to portfolios with
mixture of elliptically distributed ones. We treat both the Expected Shortfall and the Value-at-Risk of such portfolios. Special
attention is given to the particular case of a mixture of multivariate t-distributions.
This is a part of J. SADEFO-KAMDEM PhD Thesis[12] of the Université de Reims, France . It has been presented at the workshop
on modelling and computation in Financial Engineering at Bad Herrenalb, Germany May 6-8, 2003. The author is an associate
professor at the Department of mathematics, université d’Evry Val d’Essonne. 相似文献
93.
Facility layout problems: A survey 总被引:3,自引:0,他引:3
Layout problems are found in several types of manufacturing systems. Typically, layout problems are related to the location of facilities (e.g., machines, departments) in a plant. They are known to greatly impact the system performance. Most of these problems are NP hard. Numerous research works related to facility layout have been published. A few literature reviews exist, but they are not recent or are restricted to certain specific aspects of these problems. The literature analysis given here is recent and not restricted to specific considerations about layout design.
We suggest a general framework to analyze the literature and present existing works using such criteria as: the manufacturing system features, static/dynamic considerations, continual/discrete representation, problem formulation, and resolution approach. Several research directions are pointed out and discussed in our conclusion. 相似文献
94.
Local Exact Particle Tracing on Unstructured Grids 总被引:1,自引:0,他引:1
For analyzing and interpreting results of flow simulations, particle tracing is a well established visualization method. In addition, it is a preliminary step for more advanced techniques such as line integral convolution. For interactive exploration of large data sets, a very efficient and reliable particle tracing method is needed. For wind channel experiments or flight simulations, large unstructured computational grids have become common practice. Traditional approachs, based on numerical integration methods of ordinary differential equations however fail to deliver sufficiently accurate path calculation at the speed required for interactive use. In this paper we extend the local exact approach of Nielson and Jung in such a way that it can be used for interactive particle tracing in large data sets of steady flow simulation experiments. This will be achieved by sophisticated preprocessing using additional memory. For further visual enhancement of the streamline we construct an implicitly defined smooth Bézier curve that is used for ray tracing. This allows us to visualize additional scalar values of the simulation as attributes to the trajectory and enables the display of high‐quality smooth curves without creating any visualization geometry and providing a good impression of the spatial situation at the same time. ACM CSS: I.3.3 Computer Graphics—Line and curve generation; I .3.7 Computer Graphics—Raytracing; G.1.2 Numerical Analysis—Spline and piecewise polynomial approximation 相似文献
95.
This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
96.
由于在机器人导航等领域新的图像装置不符合透视规则,无法运用传统的透视位置估计方法,采用吴氏零点分解方法,给出非透视3点问题的解析解.利用新图像装置的几何条件,建立了非透视3点方程系统. 相似文献
97.
梁昔明 《中南工业大学学报(英文版)》2005,12(1):93-96
An active set truncated-Newton algorithm (ASTNA) is proposed to solve the large-scale bound constrained sub-problems. The global convergence of the algorithm is obtained and two groups of numerical experiments are made for the various large-scale problems of varying size. The comparison results between ASTNA and the subspace limited memory quasi-Newton algorithm and between the modified augmented Lagrange multiplier methods combined with ASTNA and the modified barrier function method show the stability and effectiveness of ASTNA for simultaneous optimization of distillation column. 相似文献
98.
[NZP]陶瓷零膨胀性能的设计 总被引:1,自引:0,他引:1
研究了「NZP」材料的零膨胀性能,并尝试对零膨胀的「NZP」陶瓷作了设计,从晶体结构、原子复合、各向异性、显微结构和复合材料等方面提出了设计思路。 相似文献
99.
Laura M. Haas Michael J. Carey Miron Livny Amit Shukla 《The VLDB Journal The International Journal on Very Large Data Bases》1997,6(3):241-256
In this paper, we re-examine the results of prior work on methods for computing ad hoc joins. We develop a detailed cost model for predicting join algorithm performance, and we use the model to develop cost formulas
for the major ad hoc join methods found in the relational database literature. We show that various pieces of “common wisdom” about join algorithm
performance fail to hold up when analyzed carefully, and we use our detailed cost model to derive op
timal buffer allocation schemes for each of the join methods examined here. We show that optimizing their buffer allocations
can lead to large performance improvements, e.g., as much as a 400% improvement in some cases. We also validate our cost model's
predictions by measuring an actual implementation of each join algorithm considered. The results of this work should be directly
useful to implementors of relational query optimizers and query processing systems.
Edited by M. Adiba. Received May 1993 / Accepted April 1996 相似文献
100.
一个矢量形式的双圆弧插值算法 总被引:3,自引:1,他引:2
本文在分析数控插补最常用的双圆弧插值算法特点的基础上,将以局部坐标系中的三角运算为核心的传统双圆弧插值算法,改造成为以整体坐标系中的线性运算为核心的矢量形式的双圆弧插值算法,从而减少了计算的复杂性和程序的复杂性,提高了效率和可靠性。 相似文献