全文获取类型
收费全文 | 1025篇 |
免费 | 56篇 |
专业分类
电工技术 | 16篇 |
化学工业 | 372篇 |
金属工艺 | 24篇 |
机械仪表 | 30篇 |
建筑科学 | 36篇 |
能源动力 | 27篇 |
轻工业 | 45篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 67篇 |
一般工业技术 | 172篇 |
冶金工业 | 73篇 |
原子能技术 | 8篇 |
自动化技术 | 206篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 71篇 |
2021年 | 81篇 |
2020年 | 31篇 |
2019年 | 36篇 |
2018年 | 42篇 |
2017年 | 32篇 |
2016年 | 34篇 |
2015年 | 46篇 |
2014年 | 50篇 |
2013年 | 73篇 |
2012年 | 65篇 |
2011年 | 64篇 |
2010年 | 61篇 |
2009年 | 56篇 |
2008年 | 33篇 |
2007年 | 45篇 |
2006年 | 37篇 |
2005年 | 19篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 17篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 4篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有1081条查询结果,搜索用时 15 毫秒
41.
Andrzej Buller Michal Joachimczak Juan Liu Katsunori Shimohara 《Artificial Life and Robotics》2005,9(4):197-201
This article presents the key assumptions and current status of the ATR Artificial Brain Project being undertaken to create
Volitron, a device equipped with circuitry that enables the emergence of thought. Such thought would be recognized from Volitron's
specific communication behaviors. The project consists of three complementary themes: psychodynamic architecture, brain-specific
evolvable hardware, and the management of brain-building. The psychodynamic architecture is designed to develop automatically,
driven by “pleasure” coming from discharges of tension gathered in special tension-accumulating devices. Tension-discharging
patterns come first of all from the robot's interactions with its care giver/provider. For the dedicated hardware, we developed
qcellular-automata (qCA), in which groups of uniform logic primitives (q-cells) serve as spike-train-processing units, as well as pulsed para-neural networks (PPNN) that can be evolved, using fuzzified
signals and a genetic algorithm combined with hill climbing, and converted into qCA. The psychodynamic ideas were tested using three robots: Neko, equipped with a pleasure-driven associator, Miao, equipped with MemeStorms (a special working memory in which conflicting ideas fight for access to the long-term memory and
actuators), and Miao+, whose brain is equipped with a growing neural network.
This work was presented in part at the 9th International Symposium on Artificial Life and Robotics, Oita, Japan, January 28–30,
2004 相似文献
42.
The so-called permutation separability criteria are simple operational conditions that are necessary for separability of mixed
states of multipartite systems: (1) permute the indices of the density matrix and (2) check if the trace norm of at least
one of the resulting operators is greater than one. If it is greater than one then the state is necessarily entangled. A shortcoming
of the permutation separability criteria is that many permutations give rise to equivalent separability criteria. Therefore,
we introduce a necessary condition for two permutations to yield independent criteria called combinatorial independence. This
condition basically means that the map corresponding to one permutation cannot be obtained by concatenating the map corresponding
to the second permutation with a norm-preserving map. We characterize completely combina-torially independent criteria, and
determine simple permutations that represent all independent criteria. The representatives can be visualized by means of a
simple graphical notation. They are composed of three basic operations: partial transpose, and two types of so-called reshufflings.
In particular, for a four-partite system all criteria except one are composed of partial transpose and only one type of reshuffling;
the exceptional one requires the second type of reshuffling. Furthermore, we show how to obtain efficiently a simple representative
for every permutation. This method allows to check easily if two permutations are Combinatorially equivalent or not. 相似文献
43.
When a rigid scene is imaged by a moving camera, the set of all displacements of all points across multiple frames often resides in a low-dimensional linear subspace. Linear subspace constraints have been used successfully in the past for recovering 3D structure and 3D motion information from multiple frames (e.g., by using the factorization method of Tomasi and Kanade (1992, International Journal of Computer Vision, 9:137–154)). These methods assume that the 2D correspondences have been precomputed. However, correspondence estimation is a fundamental problem in motion analysis. In this paper we show how the multi-frame subspace constraints can be used for constraining the 2D correspondence estimation process itself.We show that the multi-frame subspace constraints are valid not only for affine cameras, but also for a variety of imaging models, scene models, and motion models. The multi-frame subspace constraints are first translated from constraints on correspondences to constraints directly on image measurements (e.g., image brightness quantities). These brightness-based subspace constraints are then used for estimating the correspondences, by requiring that all corresponding points across all video frames reside in the appropriate low-dimensional linear subspace.The multi-frame subspace constraints are geometrically meaningful, and are {not} violated at depth discontinuities, nor when the camera-motion changes abruptly. These constraints can therefore replace {heuristic} constraints commonly used in optical-flow estimation, such as spatial or temporal smoothness. 相似文献
44.
45.
Schulz M Fritze H Tuller HL Seh H 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2004,51(11):1381-1387
Oxygen and gallium diffusivities in langasite were experimentally determined by analysis of diffusion profiles of 18O and 71Ga tracers by SIMS analysis as functions of temperature and doping. Strontium-enhanced diffusivities and activation energies of approximately 1.2+/-0.2 eV confirm the predominant role of oxygen vacancies in controlling the electrical conductivity of langasite at elevated temperature and oxygen partial pressure. The potential impact of high levels of porosity and the use of an oxygen primary ion beam on the accuracy of some of the data is discussed. The gallium diffusivity, with activation energy of 3.13 eV, was found to be more than two orders of magnitude lower than that of oxygen. Surface exchange measurements enabled estimation of gallium loss at elevated temperatures and oxygen partial pressure; the level is not believed to be of major concern for resonator performance. 相似文献
46.
Toxicity increases in ice containing monochlorophenols upon photolysis: environmental consequences 总被引:4,自引:0,他引:4
Bláha L Klánová J Klán P Janosek J Skarek M Růzicka R 《Environmental science & technology》2004,38(10):2873-2878
The toxic effects of photoproducts formed upon the photolysis of 2- and 4-chlorophenol (CP) frozen solutions in polycrystalline ice phase were determined with a bacterial luminescence test (Vibrio fisheri), and in vitro biomarker assay for dioxin-like effects (inductions of AhR-dependent luciferase in H4IIE-luc cells) and compared to the toxic effects of products of the same photoreaction in aquatic phase. Coupling photoproducts formed in ice samples (3'-chlorobiphenyl-2,4'-diol and 3-chlorobiphenyl-2,2'-diol from 2-CP photolysis and 5-chlorobiphenyl-2,4'-diol from 4-CP photolysis) were found to be more toxic to V. fisheri than parent CPs and elicited significant inductions of dioxin-like effects (the effective concentrations EC50 approximately 3 x 10(-5) mol L(-1) corresponded to known weaker ligands of AhR, such as nonplanar polychlorinated biphenyls or polycyclic aromatic hydrocarbons). To complete the picture, a photoproduct formed from 4-CP (5-chlorobiphenyl-2,4'-diol) was synthesized, and a detailed toxicity assessment with purified compound confirmed the results obtained with irradiated samples. Our findings support a recently proposed model according to which solar radiation can trigger the formation of new types of organic pollutants in polar ice or tropospheric ice cloud particles, presenting possibly greater risk to the environment than the parent compounds. 相似文献
47.
Palecek E Masarík M Kizek R Kuhlmeier D Hassmann J Schülein J 《Analytical chemistry》2004,76(19):5930-5936
MutS protein plays an important role in the DNA repair system in prokaryotic and eukaryotic cells; it recognizes unpaired and mispaired bases in duplex DNA and can be used for detection of point mutations in vitro. We have shown that small amounts of this protein can be detected electrochemically at mercury and carbon electrodes without any labeling. Using constant current stripping analysis (CPSA) and mercury electrodes, tens of attomoles of this protein can be detected. The sensitivity of the determination at carbon electrodes is by more than 3 orders of magnitude lower. Using biotinylated DNA duplexes attached to magnetic beads, single-base mismatches and insertion/deletions were recognized by MutS. Picogram amounts of this protein were detected by CPSA after MutS releasing from the beads. 相似文献
48.
49.
Masarik M Kizek R Kramer KJ Billova S Brazdova M Vacek J Bailey M Jelen F Howard JA 《Analytical chemistry》2003,75(11):2663-2669
The proteins streptavidin and avidin were electrochemically detected in solution by adsorptive transfer stripping square wave voltammetry (AdTS SWV) at a carbon paste electrode (CPE). AdTS SWV was used to quantify biotinylated oligonucleotides, DNA hybridizations, and avidin in extracts of transgenic avidin maize. The detection limits of denatured and native streptavidin were 6 pM and 120 nM, respectively. The results demonstrated that streptavidin/avidin AdTS SWV is a sensitive and specific method for quantifying DNA and proteins in biological samples such as foods and tissue extracts, including genetically modified crops (avidin maize) and other plants in neighboring fields. 相似文献
50.
Michal Kunc 《Theory of Computing Systems》2007,40(4):521-551
We construct a finite language L such that the largest language commuting with L is not recursively enumerable. This gives
a negative answer to the question raised by Conway in 1971 and also strongly disproves Conway's conjecture on context-freeness
of maximal solutions of systems of semi-linear inequalities. 相似文献