全文获取类型
收费全文 | 3893篇 |
免费 | 279篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 43篇 |
综合类 | 2篇 |
化学工业 | 1082篇 |
金属工艺 | 61篇 |
机械仪表 | 108篇 |
建筑科学 | 100篇 |
矿业工程 | 6篇 |
能源动力 | 194篇 |
轻工业 | 534篇 |
水利工程 | 35篇 |
石油天然气 | 14篇 |
无线电 | 270篇 |
一般工业技术 | 682篇 |
冶金工业 | 121篇 |
原子能技术 | 31篇 |
自动化技术 | 900篇 |
出版年
2024年 | 7篇 |
2023年 | 66篇 |
2022年 | 174篇 |
2021年 | 197篇 |
2020年 | 139篇 |
2019年 | 138篇 |
2018年 | 159篇 |
2017年 | 152篇 |
2016年 | 179篇 |
2015年 | 127篇 |
2014年 | 196篇 |
2013年 | 304篇 |
2012年 | 252篇 |
2011年 | 334篇 |
2010年 | 211篇 |
2009年 | 226篇 |
2008年 | 186篇 |
2007年 | 174篇 |
2006年 | 127篇 |
2005年 | 130篇 |
2004年 | 79篇 |
2003年 | 65篇 |
2002年 | 69篇 |
2001年 | 51篇 |
2000年 | 41篇 |
1999年 | 32篇 |
1998年 | 36篇 |
1997年 | 27篇 |
1996年 | 41篇 |
1995年 | 28篇 |
1994年 | 19篇 |
1993年 | 12篇 |
1992年 | 13篇 |
1991年 | 24篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1977年 | 6篇 |
1975年 | 5篇 |
1973年 | 6篇 |
1972年 | 3篇 |
排序方式: 共有4183条查询结果,搜索用时 15 毫秒
91.
Combining higher-order abstract syntax and (co)-induction in a logical framework is well known to be problematic. We describe
the theory and the practice of a tool called Hybrid, within Isabelle/HOL and Coq, which aims to address many of these difficulties.
It allows object logics to be represented using higher-order abstract syntax, and reasoned about using tactical theorem proving
and principles of (co)induction. Moreover, it is definitional, which guarantees consistency within a classical type theory.
The idea is to have a de Bruijn representation of λ-terms providing a definitional layer that allows the user to represent object languages using higher-order abstract syntax,
while offering tools for reasoning about them at the higher level. In this paper we describe how to use Hybrid in a multi-level
reasoning fashion, similar in spirit to other systems such as Twelf and Abella. By explicitly referencing provability in a middle layer called a specification logic, we solve the problem of reasoning
by (co)induction in the presence of non-stratifiable hypothetical judgments, which allow very elegant and succinct specifications
of object logic inference rules. We first demonstrate the method on a simple example, formally proving type soundness (subject
reduction) for a fragment of a pure functional language, using a minimal intuitionistic logic as the specification logic.
We then prove an analogous result for a continuation-machine presentation of the operational semantics of the same language,
encoded this time in an ordered linear logic that serves as the specification layer. This example demonstrates the ease with
which we can incorporate new specification logics, and also illustrates a significantly more complex object logic whose encoding
is elegantly expressed using features of the new specification logic. 相似文献
92.
In this paper we present the "R&W Simulator" (version 3.0), a Java simulator of Rescorla and Wagner's prediction error model of learning. It is able to run whole experimental designs, and compute and display the associative values of elemental and compound stimuli simultaneously, as well as use extra configural cues in generating compound values; it also permits change of the US parameters across phases. The simulator produces both numerical and graphical outputs, and includes a functionality to export the results to a data processor spreadsheet. It is user-friendly, and built with a graphical interface designed to allow neuroscience researchers to input the data in their own "language". It is a cross-platform simulator, so it does not require any special equipment, operative system or support program, and does not need installation. The "R&W Simulator" (version 3.0) is available free. 相似文献
93.
We propose a solution to the problem of semiglobal output regulation for nonlinear minimum-phase systems driven by uncertain exosystems that does not rely upon conventional adaptation schemes to estimate the frequency of the exogenous signals. Rather, the proposed approach relies upon regression-like arguments used to derive a nonlinear internal model able to offset the presence of an unknown number of harmonic exogenous inputs of uncertain amplitude, phase and frequency. The design methodology guarantees asymptotic regulation if the dimension of the regulator exceeds a lower bound determined by the actual number of harmonic components of the exogenous input. If this is not the case, a bounded steady-state regulation error is ensured whose amplitude, though, can be arbitrarily decreased by acting on a design parameter of the regulator. 相似文献
94.
Arranging office space into a single open room offers advantages in terms of easy exchange of information and interaction among coworkers, but reduces privacy and acoustic comfort. Thus, the purpose of this work was to evaluate the acoustic quality of a real open-plan office and to propose changes in the room to improve the acoustic conditioning of this office. The computational model of the office under study was calibrated based on RT and STI measurements. Predictions were made of the RT and STI, which generated the radius of distraction r(D), and the rate of spatial decay of sound pressure levels per distance doubling DL(2) in the real conditions of the office and after modifications of the room. The insertion of dividers between work stations and an increase in the ceiling's sound absorption improved the acoustic conditions in the office under study. 相似文献
95.
In this paper, an IMS LD engine based on a Petri net model that represents the operational semantics of units of learning based on this specification is presented. The Petri nets of this engine, which is called OPENET4LD, verify the structural properties that are desirable for a learning flow and also facilitate the adaptation of the engine if potential changes in the IMS LD specification were proposed. Furthermore, OPENET4LD has an open and flexible architecture based on a set of ontologies that describe both the semantics of the Petri nets execution and the semantics of each learning flow component of IMS LD. Furthermore, the implementation of this architecture has been exhaustively validated with a number of UoLs that are compliant with the levels A and B of IMS LD. 相似文献
96.
In microalloyed steels, static recrystallisation is temporarily inhibited by precipitation which is occurring at the same time. A high number of microalloyed steels containing various combinations of carbon, nitrogen and precipitate forming elements like V, Nb and Ti were recrystallised at different temperatures and strain rates. From these results recrystallisation‐precipitation–time‐temperature (RPTT) diagrams were established. The influence of grain size and strain rate on the RPTT diagrams was studied. The precipitation kinetics were mathematically described for isothermal conditions and converted to cooling conditions, which enables an application to hot rolling. Under cooling conditions, completion of recrystallisation is prevented, especially for Nb alloyed steels. 相似文献
97.
98.
A multistep iterative calibration methodology for the opto-mechanical system introduced in Part I is proposed. The methodology makes use of a monoview coplanar set of control points, whose number has been determined on the basis of both geometrical considerations and the results of a statistical analysis aiming at assessing the procedure stability in the case of noisy image data. The calibration procedure is carried out comparing the theoretical and observed images of the calibration pattern. Both synthetic and real data have been employed to test the calibration procedure, which proved to be accurate and efficient. The experimental results achieved by the calibrated system are satisfactory in terms of measurement precision. 相似文献
99.
The single-objective optimization of structures, whose parameters are assigned as fuzzy numbers or fuzzy relations, is presented in this paper as a particular case of the random set theory and evidence theory approach to uncertainty. Some basic concepts concerning these theories are reviewed and the relationships among interval analysis, convex modeling, possibility theory and probability theory are pointed out. In this context a frequentistic view of fuzzy sets makes sense and it is possible to calculate bounds on the probability that the solution satisfies the constraints. Some special but useful cases illustrate in detail the meaning of the approach proposed and its links with a recent formulation conceived within the context of convex modeling. Some theorems allow a very efficient computational procedure to be set up in many real design situations. Two numerical examples illustrate the model presented. 相似文献
100.
Surface subdivision for generating superquadrics 总被引:1,自引:0,他引:1