全文获取类型
收费全文 | 3961篇 |
免费 | 232篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 48篇 |
综合类 | 3篇 |
化学工业 | 1195篇 |
金属工艺 | 52篇 |
机械仪表 | 86篇 |
建筑科学 | 132篇 |
矿业工程 | 3篇 |
能源动力 | 130篇 |
轻工业 | 443篇 |
水利工程 | 19篇 |
无线电 | 359篇 |
一般工业技术 | 741篇 |
冶金工业 | 233篇 |
原子能技术 | 45篇 |
自动化技术 | 707篇 |
出版年
2024年 | 8篇 |
2023年 | 47篇 |
2022年 | 253篇 |
2021年 | 287篇 |
2020年 | 121篇 |
2019年 | 106篇 |
2018年 | 141篇 |
2017年 | 135篇 |
2016年 | 170篇 |
2015年 | 145篇 |
2014年 | 154篇 |
2013年 | 255篇 |
2012年 | 230篇 |
2011年 | 292篇 |
2010年 | 211篇 |
2009年 | 211篇 |
2008年 | 181篇 |
2007年 | 163篇 |
2006年 | 161篇 |
2005年 | 113篇 |
2004年 | 95篇 |
2003年 | 78篇 |
2002年 | 59篇 |
2001年 | 47篇 |
2000年 | 33篇 |
1999年 | 43篇 |
1998年 | 85篇 |
1997年 | 54篇 |
1996年 | 46篇 |
1995年 | 23篇 |
1994年 | 36篇 |
1993年 | 17篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 13篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 20篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有4196条查询结果,搜索用时 15 毫秒
41.
Giordano Maria C. Longhi Stefano Barelli Matteo Mazzanti Andrea Buatier de Mongeot Francesco Della Valle Giuseppe 《Nano Research》2018,11(7):3943-3956
Nano Research - The engineering of self-organized plasmonic metasurfaces is demonstrated using a maskless technique with defocused ion-beam sputtering and kinetically controlled deposition. The... 相似文献
42.
43.
M Nicotra M Paci M Sette AJ Oakley MW Parker M Lo Bello AM Caccuri G Federici G Ricci 《Canadian Metallurgical Quarterly》1998,37(9):3020-3027
The conformation of the bound glutathione (GSH) in the active site of the human glutathione transferase P1-1 (EC 2.5.1.18) has been studied by transferred NOE measurements and compared with those obtained by X-ray diffraction data. Two-dimensional TRNOESY and TRROESY experiments have been performed under fast-exchange conditions. The family of GSH conformers, compatible with TRNOE distance constraints, shows a backbone structure very similar to the crystal model. Interesting differences have been found in the side chain regions. After restrained energy minimization of a representative NMR conformer in the active site, the sulfur atom is not found in hydrogen-bonding distance of the hydroxyl group of Tyr 7. This situation is similar to the one observed in an "atypical" crystal complex grown at low pH and low temperature. The NMR conformers display also a poorly defined structure of the glutamyl moiety, and the presence of an unexpected intermolecular NOE could indicate a different interaction of this substrate portion with the G-site. The NMR data seem to provide a snapshot of GSH in a precomplex where the GSH glutamyl end is bound in a different fashion. The existence of this precomplex is supported by pre-steady-state kinetic experiments [Caccuri, A. M., Lo Bello, M., Nuccetelli, M., Nicotra, M., Rossi, P., Antonini, G., Federici, G., and Ricci, G. (1998) Biochemistry 37, 3028-3034] and preliminary time-resolved fluorescence data. 相似文献
44.
Francesco Delli Priscoli 《Wireless Networks》1996,2(3):239-247
Third generation of mobile systems is now entering the operational phase; European Community ACTS (RACE follow-on) programme just aims at finalizing the plenty of solutions resulting from the European Community RACE programme as well as from several other studies and researches. European manufactures, also deeply involved in the ACTS programme, seem to show a preference for solutions which gradually upgrade the present pan-European GSM successful standard. The underlying concept is the one of asmooth migration from the GSM network to the third generation system, in order to reuse, at least in the first phases of the transition, most of the existing technologies and infrastructures already implemented for the GSM network. In this respect, this paper, by referring to radio interface aspects, proposes a two step evolution: in the first step, a Dynamic Channel Allocation (DCA) strategy with distributed control should be implemented for coping with the high variance of traffic entailed by the reduction of cell dimensions; in the second step, a gradual upgrading of the GSM Base Stations should allow a smooth transition towards the third generation Packet Reservation Multiple Access (PRMA) technique and the provision of broadband services. The paper is partly based upon the work performed by the author in the framework of the RACE project Satellite Integration in the Future Mobile Network (SAINT) and of the European Community ACTS Projects MEDIAN. The opinions herewith reported are not necessarily those of the European Community. 相似文献
45.
Giuseppe DeToffol Francesco Ancilotto Flavio Toigo 《Journal of Low Temperature Physics》1996,102(5-6):381-410
Calculations are presented, based on a Density Functional approach, of the first excited states (l=1) of alkali metal atoms (Cs and Na) in liquid
4He. We find large departures from the spherical bubble in the liquid4He structure when the alkali atom is excited. The shifts from the free atom values of the excitation and emission transition lines are calculated and compared with the experimental results. According to our calculations, the so far unseen radiative deexcitation transition for light alkalis in4He may lie in an unexplored infrared region of the spectrum. 相似文献
46.
Enabling energy-efficient and lossy-aware data compression in wireless sensor networks by multi-objective evolutionary optimization 总被引:1,自引:0,他引:1
Nodes of wireless sensor networks (WSNs) are typically powered by batteries with a limited capacity. Thus, energy is a primary constraint in the design and deployment of WSNs. Since radio communication is in general the main cause of power consumption, the different techniques proposed in the literature to improve energy efficiency have mainly focused on limiting transmission/reception of data, for instance, by adopting data compression and/or aggregation. The limited resources available in a sensor node demand, however, the development of specifically designed algorithms. To this aim, we propose an approach to perform lossy compression on single node based on a differential pulse code modulation scheme with quantization of the differences between consecutive samples. Since different combinations of the quantization process parameters determine different trade-offs between compression performance and information loss, we exploit a multi-objective evolutionary algorithm to generate a set of combinations of these parameters corresponding to different optimal trade-offs. The user can therefore choose the combination with the most suitable trade-off for the specific application. We tested our lossy compression approach on three datasets collected by real WSNs. We show that our approach can achieve significant compression ratios despite negligible reconstruction errors. Further, we discuss how our approach outperforms LTC, a lossy compression algorithm purposely designed to be embedded in sensor nodes, in terms of compression rate and complexity. 相似文献
47.
48.
Some applications require autonomous robots to search an initially unknown environment for static targets, without any a priori information about environment structure and target locations. Targets can be human victims in search and rescue or materials
in foraging. In these scenarios, the environment is incrementally discovered by the robots exploiting exploration strategies
to move around in an autonomous and effective way. Most of the strategies proposed in literature are based on the idea of
evaluating a number of candidate locations on the frontier between the known and the unknown portions of the environment according
to ad hoc utility functions that combine different criteria. In this paper, we show some of the advantages of using a more theoretically-grounded
approach, based on Multi-Criteria Decision Making (MCDM), to define exploration strategies for robots employed in search and
rescue applications. We implemented some MCDM-based exploration strategies within an existing robot controller and we evaluated
their performance in a simulated environment. 相似文献
49.
50.
Given a graph G where a label is associated with each edge, we address the problem of looking for a maximum matching of G using the minimum number of different labels, namely the labeled maximum matching problem. It is a relatively new problem whose application is related to the timetabling problem. We prove it is NP-complete and present four different mathematical formulations. Moreover, we propose an exact algorithm based on a branch-and-bound approach to solve it. We evaluate the performance of our algorithm on a wide set of instances and compare our computational times with the ones required by CPLEX to solve the proposed mathematical formulations. Test results show the effectiveness of our procedure, that hugely outperforms the solver. 相似文献