全文获取类型
收费全文 | 10566篇 |
免费 | 462篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 104篇 |
综合类 | 4篇 |
化学工业 | 2062篇 |
金属工艺 | 153篇 |
机械仪表 | 200篇 |
建筑科学 | 628篇 |
矿业工程 | 29篇 |
能源动力 | 342篇 |
轻工业 | 970篇 |
水利工程 | 111篇 |
石油天然气 | 29篇 |
无线电 | 770篇 |
一般工业技术 | 2041篇 |
冶金工业 | 1685篇 |
原子能技术 | 44篇 |
自动化技术 | 1876篇 |
出版年
2023年 | 71篇 |
2022年 | 138篇 |
2021年 | 233篇 |
2020年 | 185篇 |
2019年 | 224篇 |
2018年 | 237篇 |
2017年 | 236篇 |
2016年 | 263篇 |
2015年 | 230篇 |
2014年 | 342篇 |
2013年 | 702篇 |
2012年 | 566篇 |
2011年 | 814篇 |
2010年 | 521篇 |
2009年 | 490篇 |
2008年 | 603篇 |
2007年 | 537篇 |
2006年 | 457篇 |
2005年 | 409篇 |
2004年 | 354篇 |
2003年 | 331篇 |
2002年 | 291篇 |
2001年 | 176篇 |
2000年 | 175篇 |
1999年 | 164篇 |
1998年 | 247篇 |
1997年 | 209篇 |
1996年 | 178篇 |
1995年 | 141篇 |
1994年 | 119篇 |
1993年 | 125篇 |
1992年 | 101篇 |
1991年 | 91篇 |
1990年 | 90篇 |
1989年 | 75篇 |
1988年 | 59篇 |
1987年 | 74篇 |
1986年 | 63篇 |
1985年 | 64篇 |
1984年 | 66篇 |
1983年 | 78篇 |
1982年 | 60篇 |
1981年 | 54篇 |
1980年 | 52篇 |
1979年 | 47篇 |
1978年 | 36篇 |
1977年 | 34篇 |
1976年 | 45篇 |
1975年 | 29篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Garbage collection can be done in vector mode on supercomputers like the CRAY-2 and the Cyber 205. Both copying collection and mark-and-sweep can be expressed as breadth-first searches in which the queue can be processed in parallel. We have designed a copying garbage collector whose inner loop works entirely in vector mode. We give performance measurements of the algorithm as implemented for Lisp CONS cells on the Cyber 205. Vector-mode garbage collection performs up to nine times faster than scalar-mode collection-a worthwhile improvement.Supported in part by NSF Grants DCR-8603543 and CCR-8806121, and by a Digital Equipment Corp. Faculty Incentive Grant.Supported by the NSF Research Experiences for Undergraduates program. 相似文献
62.
LetR be a unidirectional asynchronous ring ofn identical processors each with a single input bit. Letf be any cyclic nonconstant function ofn boolean variables. Moran and Warmuth (1986) prove that anydeterministic algorithm that evaluatesf onR has communication complexity (n logn) bits. They also construct a family of cyclic nonconstant boolean functions that can be evaluated inO(n logn) bits by a deterministic algorithm.This contrasts with the following new results:
相似文献
1. | There exists a family of cyclic nonconstant boolean functions which can be evaluated with expected complexity bits by arandomized algorithm forR. |
2. | Anynondeterministic algorithm forR which evaluates any cyclic nonconstant function has communication complexity bits. |
63.
An investigation was carried out in a commercial abattoir on the influence of processing and refrigeration on a variety of beef and sheep offals. The influences of the different processes and the operations, to the bacterial load before refrigeration of the product, were determined. In general all the operations in the plant had an effect on the final bacterial load. The effect of inadequate refrigeration was noteworthy in all cases and this factor alone made the most significant contribution to the products having a poor shelf-life. 相似文献
64.
James F. Lynch 《Computational Complexity》1992,2(1):40-66
For every nondeterministic Turing machineM of time complexityT(n), there is a second-order sentence of a very restricted form, whose set of finite models encodes the set of strings recognized byM. Specifically, has a relational symbol which is interpreted as addition restricted to finite segments of the natural numbers, and a prefix consisting of existentially quantified unary second-order variables followed by a universal-existential first-order part. Here, every input stringx is encoded by a model of sizeT(|x|). Using a closely related encoding of strings as models where the size of the model is the length of the string, a consequence is that ifT(n)=n
d, then there is a sentence with a similar prefix but whose second-order variables ared-ary and whose finite models encode the strings accepted byM. Potential applications to low-level complexity are discussed. 相似文献
65.
Measurements are reported of the dielectric properties of two semiconducting glasses of composition SiO2 · Na2O with admixtures of Sb2O
5 and SnO2, covering a wide range of temperatures and a range of six decades of frequency 10–2 to 104 Hz. Both glasses show a gradual evolution of growing low frequency dispersion (LFD) with increasing temperature, with both the real and imaginary components of the complex susceptibility following a power law of the type
n–1, with n 1 at the lowest frequencies. There are also clear indications of reversible phase transitions taking place which manifest themselves by changes in the spectral shape of the dielectric response. 相似文献
66.
Several related algorithms are presented for computing logarithms in fieldsGF(p),p a prime. Heuristic arguments predict a running time of exp((1+o(1))
) for the initial precomputation phase that is needed for eachp, and much shorter running times for computing individual logarithms once the precomputation is done. The running time of the precomputation is roughly the same as that of the fastest known algorithms for factoring integers of size aboutp. The algorithms use the well known basic scheme of obtaining linear equations for logarithms of small primes and then solving them to obtain a database to be used for the computation of individual logarithms. The novel ingredients are new ways of obtaining linear equations and new methods of solving these linear equations by adaptations of sparse matrix methods from numerical analysis to the case of finite rings. While some of the new logarithm algorithms are adaptations of known integer factorization algorithms, others are new and can be adapted to yield integer factorization algorithms. 相似文献
67.
The adaptive Generalized Predictive Controller (Clarke et al., 1987a, b) is capable of controlling plants with variable dead-time, unknown model orders and unstable poles and zeros. This paper shows how the GPC control law can be written in an equivalent general linear transfer function form which simplifies closed-loop (eg. root locus) analysis. Three recommended strategies for selecting the design parameters during the commissioning stage allow the user to adjust the closed-loop speed of response on-line using only a single active tuning parameter. Experimental runs confirm the ability of adaptive GPC to provide a consistent closed-loop response in spite of large process changes. 相似文献
68.
69.
Andrew J. Allen 《Journal of the American Ceramic Society》2005,88(6):1367-1381
This paper reviews some recent advances in small-angle X-ray and neutron scattering methods and their application to address complex issues in ceramic systems of technological importance. It is shown how small-angle scattering (SAS) can be applied to ceramic systems in order to extract statistically representative microstructure information (e.g., void volume fraction size distributions, internal surface areas, pore morphologies) that complements the information obtained from diffraction methods, X-ray microtomography, or electron microscopy. It is demonstrated how SAS studies provide insights, not obtainable by other means, on the processing–microstructure–property relationships that frequently govern technological performance. 相似文献
70.
James Charles Tomas Pfister Mark Everingham Andrew Zisserman 《International Journal of Computer Vision》2014,110(1):70-90
We present a fully automatic arm and hand tracker that detects joint positions over continuous sign language video sequences of more than an hour in length. To achieve this, we make contributions in four areas: (i) we show that the overlaid signer can be separated from the background TV broadcast using co-segmentation over all frames with a layered model; (ii) we show that joint positions (shoulders, elbows, wrists) can be predicted per-frame using a random forest regressor given only this segmentation and a colour model; (iii) we show that the random forest can be trained from an existing semi-automatic, but computationally expensive, tracker; and, (iv) introduce an evaluator to assess whether the predicted joint positions are correct for each frame. The method is applied to 20 signing footage videos with changing background, challenging imaging conditions, and for different signers. Our framework outperforms the state-of-the-art long term tracker by Buehler et al. (International Journal of Computer Vision 95:180–197, 2011), does not require the manual annotation of that work, and, after automatic initialisation, performs tracking in real-time. We also achieve superior joint localisation results to those obtained using the pose estimation method of Yang and Ramanan (Proceedings of the IEEE conference on computer vision and pattern recognition, 2011). 相似文献