全文获取类型
收费全文 | 5735篇 |
免费 | 206篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 147篇 |
综合类 | 13篇 |
化学工业 | 1462篇 |
金属工艺 | 118篇 |
机械仪表 | 105篇 |
建筑科学 | 433篇 |
矿业工程 | 10篇 |
能源动力 | 124篇 |
轻工业 | 755篇 |
水利工程 | 66篇 |
石油天然气 | 14篇 |
无线电 | 302篇 |
一般工业技术 | 945篇 |
冶金工业 | 678篇 |
原子能技术 | 60篇 |
自动化技术 | 717篇 |
出版年
2022年 | 44篇 |
2021年 | 73篇 |
2020年 | 58篇 |
2019年 | 61篇 |
2018年 | 68篇 |
2017年 | 88篇 |
2016年 | 119篇 |
2015年 | 138篇 |
2014年 | 158篇 |
2013年 | 258篇 |
2012年 | 233篇 |
2011年 | 249篇 |
2010年 | 212篇 |
2009年 | 226篇 |
2008年 | 226篇 |
2007年 | 251篇 |
2006年 | 213篇 |
2005年 | 203篇 |
2004年 | 188篇 |
2003年 | 130篇 |
2002年 | 137篇 |
2001年 | 112篇 |
2000年 | 99篇 |
1999年 | 81篇 |
1998年 | 104篇 |
1997年 | 99篇 |
1996年 | 88篇 |
1995年 | 76篇 |
1994年 | 55篇 |
1993年 | 80篇 |
1992年 | 83篇 |
1991年 | 58篇 |
1990年 | 67篇 |
1989年 | 66篇 |
1987年 | 73篇 |
1986年 | 60篇 |
1985年 | 73篇 |
1984年 | 65篇 |
1983年 | 62篇 |
1982年 | 65篇 |
1981年 | 69篇 |
1980年 | 69篇 |
1979年 | 70篇 |
1978年 | 51篇 |
1977年 | 54篇 |
1976年 | 58篇 |
1975年 | 56篇 |
1974年 | 67篇 |
1973年 | 49篇 |
1970年 | 42篇 |
排序方式: 共有5949条查询结果,搜索用时 0 毫秒
41.
Daniele Di Gioacchino Nicola Poccia Martijn Lankhorst Claudio Gatti Bruno Buonomo Luca Foggetta Augusto Marcelli Hans Hilgenkamp 《Journal of Superconductivity and Novel Magnetism》2017,30(2):359-363
The current frontiers in the investigation of high-energy particles demand for new detection methods. Higher sensitivity to low-energy deposition, high-energy resolution to identify events and improve the background rejection, and large detector masses have to be developed to detect even an individual particle that weakly interacts with ordinary matter. Here, we will describe the concept and the layout of a novel superconducting proximity array which show dynamic vortex Mott insulator to metal transitions, as an ultra-sensitive compact radiation-particle detector. 相似文献
42.
Gian Luigi Angrisani Piriya Taptimthong Susanne Elisabeth Thürer Christian Klose Hans Jürgen Maier Marc Christopher Wurz Kai Möhwald 《Advanced Engineering Materials》2018,20(9)
43.
Single point incremental forming: state-of-the-art and prospects 总被引:1,自引:0,他引:1
Joost R. Duflou Anne-Marie Habraken Jian Cao Rajiv Malhotra Markus Bambach Dave Adams Hans Vanhove Amirahmad Mohammadi Jack Jeswiet 《International Journal of Material Forming》2018,11(6):743-773
Incremental sheet metal forming in general and Single Point Incremental Forming (SPIF) specifically have gone through a period of intensive development with growing attention from research institutes worldwide. The result of these efforts is significant progress in the understanding of the underlying forming mechanisms and opportunities as well as limitations associated with this category of flexible forming processes. Furthermore, creative process design efforts have enhanced the process capabilities and process planning methods. Also, simulation capabilities have evolved substantially. This review paper aims to provide an overview of the body of knowledge with respect to Single Point Incremental Forming. Without claiming to be exhaustive, each section aims for an up-to-date state-of-the-art review with corresponding conclusions on scientific progress and outlook on expected further developments. 相似文献
44.
Susanna Monti Giovanni Barcaro Luca Sementa Vincenzo Carravetta Hans Ågren 《Nano Research》2018,11(4):1757-1767
The self-assembling properties, stability, and dynamics of hybrid nanocarriers (gold nanoparticles (AuNPs) functionalized with cysteine-based peptides) in solution are studied through a series of classical molecular dynamics simulations based on a recently parametrized reactive force field. The results reveal, at the atomic level, all the details regarding the peptide adsorption mechanisms, nanoparticle stabilization, aggregation, and sintering. The data confirm and explain the experimental findings and disclose aspects that cannot be scrutinized by experiments. The biomolecules are both chemisorbed and physisorbed; self-interactions of the adsorbates and formation of stable networks of interconnected molecules on the AuNP surfaces limit substrate reconstructions, protect the AuNPs from the action of the solvent, and prevent direct interactions of the gold surfaces. The possibility of agglomeration of the functionalized nanoparticles, compared with the sintering of the bare supports in a water solution, is demonstrated through relatively long simulations and fast steered dynamics. The analysis of the trajectories reveals that the AuNPs were well stabilized by the peptides. This prevented particle sintering and kept the particles far apart; however, part of their chains could form interconnections (crosslinks) between neighboring gold vehicles. The excellent agreement of these results with the literature confirm the reliability of the method and its potential application to the modeling of more complex materials relevant to the biomedical sector. 相似文献
45.
We performed Raman measurements at 18 K and pressures up to 25 GPa in order to construct a tentative phase diagram of the (N
2)1–x
:(O
2)x
–system at low temperatures. We varied the composition of the mixed system over the whole concentration range. Here we focused on the systems with high nitrogen concentration and pressures above 2 GPa. It is known that at room temperature oxygen is highly solvable in the –phase of N
2. The experimental results show that oxygen suppresses the disorder–order transition –N
2. 相似文献
46.
Michael Buro Hans Kleine Büning 《Annals of Mathematics and Artificial Intelligence》1996,18(2):243-260
We investigate properties ofk-resolution, a restricted version of resolution in which one parent clause must have length at mostk. Starting from a unit-preference strategy, we compare minimal proof lengths of unit-resolution and unrestricted resolution. In particular, we show that the speed-up by using resolution is bound by
if the shortest unit-resolution refutation needst steps. Next we present an algorithm which decides whether the empty clause can be deduced by 2-resolution from a formula and has time complexity O(length()4). Finally we describe effects onk-resolution if a formula is transformed intot-CNF and show that extended 3-resolution is complete and sound. 相似文献
47.
This paper is the first attempt to successfully design efficient approximation algorithms for the single-machine weighted
flow-time minimization problem when jobs have different release dates and weights equal to their processing times under the
assumption that one job is fixed (i.e., the machine is unavailable during a fixed interval corresponding to the fixed job).
Our work is motivated by an interesting algorithmic application to the generation of valid inequalities in a branch-and-cut
method. Our analysis shows that the trivial FIFO sequence can lead to an arbitrary large worst-case performance bound. Hence,
we modify this sequence so that a new 2-approximation solution can be obtained for every instance and we prove the tightness
of this bound. Then, we propose a fully polynomial-time approximation algorithm with efficient running time for the considered
problem. Especially, the complexity of our algorithm is strongly polynomial. 相似文献
48.
Hans De Sterck Killian Miller Geoffrey Sanders 《Computing and Visualization in Science》2011,14(2):51-65
Recently, it was shown how the convergence of a class of multigrid methods for computing the stationary distribution of sparse,
irreducible Markov chains can be accelerated by the addition of an outer iteration based on iterant recombination. The acceleration
was performed by selecting a linear combination of previous fine-level iterates with probability constraints to minimize the
two-norm of the residual using a quadratic programming method. In this paper we investigate the alternative of minimizing
the one-norm of the residual. This gives rise to a nonlinear convex program which must be solved at each acceleration step.
To solve this minimization problem we propose to use a deep-cuts ellipsoid method for nonlinear convex programs. The main
purpose of this paper is to investigate whether an iterant recombination approach can be obtained in this way that is competitive
in terms of execution time and robustness. We derive formulas for subgradients of the one-norm objective function and the
constraint functions, and show how an initial ellipsoid can be constructed that is guaranteed to contain the exact solution
and give conditions for its existence. We also investigate using the ellipsoid method to minimize the two-norm. Numerical
tests show that the one-norm and two-norm acceleration procedures yield a similar reduction in the number of multigrid cycles.
The tests also indicate that one-norm ellipsoid acceleration is competitive with two-norm quadratic programming acceleration
in terms of running time with improved robustness. 相似文献
49.
50.
Making changes to software systems can prove costly and it remains a challenge to understand the factors that affect the costs
of software evolution. This study sought to identify such factors by investigating the effort expended by developers to perform
336 change tasks in two different software organizations. We quantitatively analyzed data from version control systems and
change trackers to identify factors that correlated with change effort. In-depth interviews with the developers about a subset
of the change tasks further refined the analysis. Two central quantitative results found that dispersion of changed code and
volatility of the requirements for the change task correlated with change effort. The analysis of the qualitative interviews
pointed to two important, underlying cost drivers: Difficulties in comprehending dispersed code and difficulties in anticipating
side effects of changes. This study demonstrates a novel method for combining qualitative and quantitative analysis to assess
cost drivers of software evolution. Given our findings, we propose improvements to practices and development tools to manage
and reduce the costs. 相似文献