全文获取类型
收费全文 | 293653篇 |
免费 | 4825篇 |
国内免费 | 2149篇 |
专业分类
电工技术 | 5617篇 |
技术理论 | 1篇 |
综合类 | 1401篇 |
化学工业 | 42730篇 |
金属工艺 | 12107篇 |
机械仪表 | 9271篇 |
建筑科学 | 7444篇 |
矿业工程 | 1871篇 |
能源动力 | 7452篇 |
轻工业 | 24029篇 |
水利工程 | 3368篇 |
石油天然气 | 6353篇 |
武器工业 | 149篇 |
无线电 | 35098篇 |
一般工业技术 | 58522篇 |
冶金工业 | 52435篇 |
原子能技术 | 7636篇 |
自动化技术 | 25143篇 |
出版年
2022年 | 2075篇 |
2021年 | 3082篇 |
2020年 | 2269篇 |
2019年 | 2541篇 |
2018年 | 4093篇 |
2017年 | 4297篇 |
2016年 | 4435篇 |
2015年 | 3189篇 |
2014年 | 5253篇 |
2013年 | 12962篇 |
2012年 | 8170篇 |
2011年 | 10885篇 |
2010年 | 8520篇 |
2009年 | 9678篇 |
2008年 | 9963篇 |
2007年 | 9910篇 |
2006年 | 8515篇 |
2005年 | 7824篇 |
2004年 | 7593篇 |
2003年 | 7296篇 |
2002年 | 7025篇 |
2001年 | 7135篇 |
2000年 | 6706篇 |
1999年 | 6985篇 |
1998年 | 16683篇 |
1997年 | 11882篇 |
1996年 | 9127篇 |
1995年 | 6989篇 |
1994年 | 6130篇 |
1993年 | 6147篇 |
1992年 | 4450篇 |
1991年 | 4217篇 |
1990年 | 4117篇 |
1989年 | 4086篇 |
1988年 | 3774篇 |
1987年 | 3411篇 |
1986年 | 3410篇 |
1985年 | 3765篇 |
1984年 | 3483篇 |
1983年 | 3235篇 |
1982年 | 3041篇 |
1981年 | 3070篇 |
1980年 | 3048篇 |
1979年 | 2840篇 |
1978年 | 2880篇 |
1977年 | 3167篇 |
1976年 | 4121篇 |
1975年 | 2425篇 |
1974年 | 2379篇 |
1973年 | 2398篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
911.
I. V. Gervas’eva D. P. Rodionov Yu. V. Khlebnikova N. F. Vil’danova A. S. Shtyrlov G. A. Dosovitskii A. R. Kaul’ 《The Physics of Metals and Metallography》2007,103(6):600-608
The texture, structure, and magnetic and mechanical properties of thin ribbons of nickel-palladium alloys have been studied. It has been demonstrated that in Ni94Pd6 and Ni92.5Pd5W2.5 alloys, a sharp cube texture can be formed that is stable up to rather high annealing temperatures. Segregation of palladium atoms to surface layers of ribbons has been found, which gives additional advantages for using these ribbons as substrates for epitaxial deposition of high-temperature superconductors. 相似文献
912.
V. H. Novyts’kyi V. P. Havrylyuk D. D. Panasenko M. O. Kal’chuk V. Ya. Khoruzhyi 《Materials Science》2006,42(6):799-807
The positive influence of lead (2.5%) on the original structure of a cast composite of the Fe-Cr-Cu-C-Ti system, its wear
rate, friction coefficient, and the formation of secondary structures is established under the conditions of dry friction
and friction with boundary lubrication.
__________
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 6, pp. 73–80, November–December, 2006. 相似文献
913.
914.
S. Medhekar P.P. Paltani 《Photonics Technology Letters, IEEE》2006,18(15):1579-1581
We propose that using the phenomenon of refraction of two coaxially copropagating beams at the interface of two nonlinear media, a passive all-optical switch could be constructed for future integrated photonic circuits. 相似文献
915.
Verma M. Marwedel P. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2006,14(8):802-815
Energy consumption is one of the important parameters to be optimized during the design of portable embedded systems. Thus, most of the contemporary portable devices feature low-power processors coupled with on-chip memories (e.g., caches, scratchpads). Scratchpads are better than traditional caches in terms of power, performance, area, and predictability. However, unlike caches they depend upon software allocation techniques for their utilization. In this paper, we present scratchpad overlay techniques which analyze the application and insert instructions to dynamically copy both variables and code segments onto the scratchpad at runtime. We demonstrate that the problem of overlaying scratchpad is an extension of the Global Register Allocation problem. We present optimal and near-optimal approaches for solving the scratchpad overlay problem. The near-optimal scratchpad overlay approach achieves close to the optimal results and is significantly faster than the optimal approach. Our approaches improve upon the previously known static allocation technique for assigning both variables and code segments onto the scratchpad. The evaluation of the approaches for ARM7 processor reports, average energy, and execution time reductions of 26% and 14% over the static approach, respectively. Additional experiments comparing the overlayed scratchpads against unified caches of the same size, report average energy, and execution time savings of 20% and 10%, respectively. We also report data memory energy reductions of 45%-57% due to the insertion of a 1024-bytes scratchpad memory in the memory hierarchy of a digital signal processor (DSP). 相似文献
916.
This paper addresses the state estimation of systems with perspective outputs. We derive a minimum-energy estimator which produces an estimate of the state that is "most compatible" with the dynamics, in the sense that it requires the least amount of noise energy to explain the measured outputs. Under suitable observability assumptions, the estimate converges globally asymptotically to the true value of the state in the absence of noise and disturbance. In the presence of noise, the estimate converges to a neighborhood of the true value of the state. These results are also extended to solve the estimation problem when the measured outputs are transmitted through a network. In that case, we assume that the measurements arrive at discrete-time instants, are time-delayed, noisy, and may not be complete. We show that the redesigned minimum-energy estimator preserves the same convergence properties. We apply these results to the estimation of position and orientation for a mobile robot that uses a monocular charged-coupled device (CCD) camera mounted on-board to observe the apparent motion of stationary points. In the context of our application, the estimator can deal directly with the usual problems associated with vision systems such as noise, latency and intermittency of observations. Experimental results are presented and discussed. 相似文献
917.
The safe operation of VVéR reactors has been discussed throughout the entire design process, taking account of the normative
documentation, including the international requirements (IAEA, EUR). After the first domestic normative document “Basic principles
for securing the safety of nuclear power plants” was approved in 1973, work began on the reconstruction of the first-generation
VVéR-440 power-generating units. The measures taken to increase safety concerned all types of reactors VVéR-440 and-1000.
Information on implementing these measures is presented.
__________
Translated from Atomnaya énergiya, Vol. 101, No. 2, pp. 87–93, August, 2006. 相似文献
918.
V. P. Vasilevskii M. N. Mikhailov A. A. Petrov M. I. Rozhdestvenskii Yu. M. Cherkashov 《Atomic Energy》2006,100(4):295-301
The basic stages and directions of upgrading and reconstruction of the power-generating units of nuclear power plants with
RBMK reactors over a period of 20 yr since the Chernobyl accident are reflected in this paper. The greatest amount of work
was done in 1986–1990 on all units with RBMK-1000 and-1500 reactors which were operating at that time in the USSR. The purpose
of the upgrade was to improve the neutron-physical characteristics of the reactor cores, increase the response speed of the
safety and control system and decrease the positive effect of water outflow from the cooling loop of this system, increase
the flow capacity of the systems performing emergency discharge of the steam-gas mixture from the reactor, and improve the
basic operating documentation.
The subsequent stages of the upgrading and reconstruction concerned mainly the first-generation power-generating units (Nos.
1 and 2 units of the Leningrad and Kursk nuclear power plants). These works were performed to make the power-generating units
conform to the requirements of the modern normative documents on safety and allow for the possibility of these units to remain
in operation after the nominal 30-yr service life has been exhausted.
__________
Translated from Atomnaya énergiya, Vol. 100, No. 4, pp. 312–320, April, 2006. 相似文献
919.
P Sarkar D Ghosh D Bhattacharya R Kataky SJ Setford SF White APF Turner 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(12):1389-1394
Allergen levels in indoor environments, leading to many diseases, eg asthma, rhinitis and conjunctivitis, affect a large and increasing fraction of the population. A quite effective and inexpensive method of a rough but very rapid overall assessment of total allergen level in the environment has been developed. The method involved estimation of protein in allergen extracts by screen‐printed electrodes using two different techniques. The biosensor comprised a rhodinised carbon working electrode, a silver/silver chloride reference electrode and a carbon counter electrode. In the first method the enzyme protease reacted with allergen protein to release amino acid, which produced hydrogen peroxide in the presence of amino acid oxidase. This was detected amperometrically. The second method used potassium bromide as electrolyte and the electrode was subjected to dual potential. Bromine, released due to electrolysis at higher potential, was consumed by the allergen protein at lower potential. In the first method, a unique technique was used to microencapsulate the enzyme protease and immobilise it on the surface of the electrode by in‐situ polymerisation to avoid contact with the amino acid oxidase. A total of seven allergens were tested and the results gave a good correlation with the standard protein measurement method. Environmental specimens from indoors, schools and workplaces can be evaluated for the aeroallergens produced by dust mites, animal hairs, cockroach debris, pollens, etc as a means of determining the exposure risk. Copyright © 2005 Society of Chemical Industry 相似文献
920.
Nitrification kinetics are important for process design, optimization, and capacity rating of activated sludge wastewater treatment plants. A Water Environment Research Foundation (WERF) project on Methods for Wastewater Characterization in Activated Sludge Modeling (WERF, 2003) focused significantly on the development of procedures for measuring the nitrifier maximum specific growth rate, micro(AUT). In addition, the importance of (and lack of data for) the nitrifier decay rate, b(AUT), was identified. This paper describes three bench-scale methods for measuring micro(AUT): the Low F/M SBR, Washout and High F/M methods. During the WERF project, the importance of pH and temperature control was investigated briefly; this paper summarizes further experimental work performed to address these issues. A summary of micro(AUT) measurements in a number of locations and using the different measurement techniques is provided. 相似文献