全文获取类型
收费全文 | 25239篇 |
免费 | 1439篇 |
国内免费 | 719篇 |
专业分类
电工技术 | 821篇 |
技术理论 | 1篇 |
综合类 | 2234篇 |
化学工业 | 4509篇 |
金属工艺 | 591篇 |
机械仪表 | 1059篇 |
建筑科学 | 2034篇 |
矿业工程 | 671篇 |
能源动力 | 426篇 |
轻工业 | 3678篇 |
水利工程 | 343篇 |
石油天然气 | 601篇 |
武器工业 | 129篇 |
无线电 | 958篇 |
一般工业技术 | 3138篇 |
冶金工业 | 1477篇 |
原子能技术 | 240篇 |
自动化技术 | 4487篇 |
出版年
2024年 | 61篇 |
2023年 | 217篇 |
2022年 | 363篇 |
2021年 | 490篇 |
2020年 | 548篇 |
2019年 | 538篇 |
2018年 | 480篇 |
2017年 | 639篇 |
2016年 | 720篇 |
2015年 | 763篇 |
2014年 | 1468篇 |
2013年 | 1429篇 |
2012年 | 1807篇 |
2011年 | 2076篇 |
2010年 | 1485篇 |
2009年 | 1475篇 |
2008年 | 1236篇 |
2007年 | 1603篇 |
2006年 | 1429篇 |
2005年 | 1168篇 |
2004年 | 1059篇 |
2003年 | 944篇 |
2002年 | 798篇 |
2001年 | 643篇 |
2000年 | 547篇 |
1999年 | 512篇 |
1998年 | 419篇 |
1997年 | 330篇 |
1996年 | 284篇 |
1995年 | 284篇 |
1994年 | 189篇 |
1993年 | 182篇 |
1992年 | 128篇 |
1991年 | 95篇 |
1990年 | 93篇 |
1989年 | 110篇 |
1988年 | 96篇 |
1987年 | 61篇 |
1986年 | 60篇 |
1985年 | 76篇 |
1984年 | 92篇 |
1983年 | 102篇 |
1982年 | 96篇 |
1981年 | 32篇 |
1980年 | 34篇 |
1979年 | 25篇 |
1978年 | 21篇 |
1977年 | 17篇 |
1959年 | 5篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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
62.
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
63.
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
64.
An efficient, convenient and quantitative method for characterising polyester end-groups is described. We have found that trichloroacetyl isocyanate (TAI) reacts rapidly and quantitatively with both carboxyl [C(O)OH] and hydroxyl (OH) chain ends to form derivatives that can be readily determined by 1H NMR spectroscopy. The TAI capped end-groups give rise to characteristic imidic NH resonances in a normally clear region of the 1H NMR spectrum [δ∼10-11.5 for C(O)-O-C(O)-NH-C(O)CCl3 from C(O)OH, δ∼8-9 for O-C(O)-NH-C(O)CCl3 from OH]. The method has been successfully applied to quantitative determination of the end-groups of a wide variety of oligomeric polyesters. It has also been applied to higher molecular weight polyesters including commercial, bottle grade, poly(ethylene terephthalate) (PET) and PET based copolyesters (e.g. PETG). 相似文献
65.
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
66.
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
67.
68.
69.
寻找非构造油气藏的新思路 总被引:3,自引:0,他引:3
目前,一种新的理论体系和研究方法已经形成,并正在发展和逐步完善。那就是层序地层学和油气成藏系统理论的诞生和发展;以及由计算机的快速发展带动起来的地震测井资料的采集、处理、显示和各种地质问题的计算机模拟技术,使得地质学和石油地质学都在朝着从定性到定量,从推测到更科学的预测方向发展。在今后的5~10年中,中国的石油地质家们不仅要注意方法和技术方面的进步,还应当重视在陆相层序地层学和陆相层序中油气成藏机制等基本理论方面的研究。 相似文献
70.
The MSMIE protocol [SBC89] allows processors in a distributed system to communicate via shared memory. It was designed to meet the reliability and efficiency needs of applications such as nuclear safety systems. We present a formal model of the MSMIE protocol expressed in the notation CCS. Desirable properties of the protocol are expressed in the modal mu-calculus, an expressive modal logic. We show that the protocol lacks an important liveness property. In actual operation, additional operating constraints are checked to avoid potential problems. We present a modified protocol and show that it possesses the liveness property even without checking operating constraints. We also show how parts of the analysis were automated with the Concurrency Workbench. 相似文献