全文获取类型
收费全文 | 11090篇 |
免费 | 924篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 85篇 |
综合类 | 6篇 |
化学工业 | 2719篇 |
金属工艺 | 136篇 |
机械仪表 | 344篇 |
建筑科学 | 502篇 |
矿业工程 | 26篇 |
能源动力 | 239篇 |
轻工业 | 2243篇 |
水利工程 | 86篇 |
石油天然气 | 20篇 |
无线电 | 806篇 |
一般工业技术 | 2158篇 |
冶金工业 | 711篇 |
原子能技术 | 26篇 |
自动化技术 | 1920篇 |
出版年
2024年 | 39篇 |
2023年 | 161篇 |
2022年 | 137篇 |
2021年 | 371篇 |
2020年 | 319篇 |
2019年 | 311篇 |
2018年 | 443篇 |
2017年 | 456篇 |
2016年 | 560篇 |
2015年 | 478篇 |
2014年 | 613篇 |
2013年 | 1129篇 |
2012年 | 987篇 |
2011年 | 776篇 |
2010年 | 573篇 |
2009年 | 550篇 |
2008年 | 588篇 |
2007年 | 512篇 |
2006年 | 458篇 |
2005年 | 309篇 |
2004年 | 276篇 |
2003年 | 247篇 |
2002年 | 237篇 |
2001年 | 147篇 |
2000年 | 126篇 |
1999年 | 111篇 |
1998年 | 149篇 |
1997年 | 127篇 |
1996年 | 91篇 |
1995年 | 90篇 |
1994年 | 80篇 |
1993年 | 72篇 |
1992年 | 45篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 27篇 |
1987年 | 19篇 |
1986年 | 26篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 18篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 17篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
In June 2003, a large scale injection experiment started at the Continental Deep Drilling site (KTB) in Germany. A tiltmeter array was installed which consisted of five high resolution borehole tiltmeters of the ASKANIA type, also equipped with three dimensional seismometers. For the next 11 months, 86 000 m(3) were injected into the KTB pilot borehole 4000 m deep. The average injection rate was approximately 200 l/min. The research objective was to observe and to analyze deformation caused by the injection into the upper crust at the kilometer range. A new data acquisition system was developed by Geo-Research Center Potsdam (GFZ) to master the expected huge amount of seismic and tilt data. Furthermore, it was necessary to develop a new preprocessing software called PREANALYSE for long-period time series. This software includes different useful functions, such as step and spike correction, interpolation, filtering, and spectral analysis. This worldwide unique installation offers the excellent opportunity of the separation of signals due to injection and due to environment by correlation of the data of the five stations with the ground water table and meteorological data. 相似文献
22.
Boulahya K Ruiz-González L Parras M González-Calbet JM Nickolsky MS Nicolopoulos S 《Ultramicroscopy》2007,107(6-7):445-452
Two complex perovskite-related structures were solved by ab initio from precession electron diffraction intensities. Structure models were firstly derived from HREM images and than have been confirmed independently using two and three-dimensional sets of precession intensities. Patterson techniques prove to be effective for ab initio structure resolution, specially in case of projections with no overlapping atoms. Quality of precession intensity data may be suitable enough to resolve unknown heavy oxide structures. 相似文献
23.
The purpose of this work was to study the impact of starter cultures on the production of flavour compounds in dry sausages. The effect of six starter cultures corresponding to different combinations of lactic acid bacteria (Lactobacillus sake L110, Pediococcus acidilactici 725, P. pentosaceus 716) and different Staphylococcus species (S. carnosus 833, S. warneri 863, S. saprophyticus M31) strains were tested in a total of 30 dry sausages without spices. The analysis of flavour compounds using a dynamic headspace apparatus coupled to a gas chromatograph and a mass spectrometer enabled us to identify about 80 volatile compounds. They were of various origins—lipids oxidation, fermentations, amino acid catabolism and animal feedstuffs. The influence of the starters and especially the flavouring strains proved to have a major effect on the level of volatile compounds in dry sausages. The flavour tests led to more accurate determination of the sensory characteristics of important molecules in the flavour of dry sausages. The sensory analyses showed that the butter odour of dry sausages largely depends on the catabolism of carbohydrates and that curing and rancid odours were correlated with some typical compounds of lipid oxidation. 相似文献
24.
José Maurício S. Bento Terezinha M. C. Della Lucia Rosa T. S. Frighetto 《Journal of chemical ecology》1993,19(10):2347-2351
Males of the sugarcane borer,Migdolus fryanus (Coleoptera: Cerambycidae), are attracted to females by means of a sex pheromone. Mating usually occurs during a few days from October to March under field conditions in São Paulo State, Brazil. This work reports on mating of this species as affected by daily climatic factors, during a single nuptial flight. Maximum male capture by the natural sex pheromone occurred from 1000 to 1100 AM at air and soil temperatures of 30.0°C and relative humidity of 57.0%. As these temperatures increased, females burrowed into the soil, as they are more sensitive to heat than males. Thus, it was concluded that sex pheromone-mediated mating in this cerambycid is directly affected by temperatures of air and soil. 相似文献
25.
Diego Perez-Palacin Raffaela Mirandola José Merseguer 《Journal of Systems and Software》2012,85(12):2796-2811
Energy use is becoming a key design consideration in computing infrastructures and services. In this paper we focus on service-based applications and we propose an adaptation framework that can be used to reduce power consumption according to the observed workload. The adaptation guarantees a trade-off between energy consumption and system performance. The approach is based on the principle of proportional energy consumption obtained by scaling down energy for unused resources, considering both the number of servers switched on and their operating frequencies. Stochastic Petri nets are proposed for the modeling of the framework concerns, their analyses give results about the trade-offs. The application of the approach to a simple case study shows its usefulness and practical applicability. Finally, different types of workloads are analyzed with validation purposes. 相似文献
26.
Bugané F Benedetti MG Casadio G Attala S Biagi F Manca M Leardini A 《Computer methods and programs in biomedicine》2012,108(1):129-137
This paper investigates the ability of a single wireless inertial sensing device stuck on the lower trunk to provide spatial-temporal parameters during level walking. The 3-axial acceleration signals were filtered and the timing of the main gait events identified. Twenty-two healthy subjects were analyzed with this system for validation, and the estimated parameters were compared with those obtained with state-of-the-art gait analysis, i.e. stereophotogrammetry and dynamometry. For each side, from four to six gait cycles were measured with the device, of which two were validated by gait analysis. The new acquisition system is easy to use and does not interfere with regular walking. No statistically significant differences were found between the acceleration-based measurements and the corresponding ones from gait analysis for most of the spatial-temporal parameters, i.e. stride length, stride duration, cadence and speed, etc.; significant differences were found for the gait cycle phases, i.e. single and double support duration, etc. The system therefore shows promise also for a future routine clinical use. 相似文献
27.
Verónica Venturini Javier Carbo José Manuel Molina 《Expert systems with applications》2012,39(12):10656-10673
Researches on Ambient Intelligent and Ubiquitous Computing using wireless technologies have increased in the last years. In this work, we review several scenarios to define a multi-agent architecture that support the information needs of these new technologies, for heterogeneous domain. Our contribution consists of designing in a methodological way a Context Aware System (involving location services) using agents that can be used in very different domains. We describe all the steps followed in the design of the agent system. We apply a hybridizing methodology between GAIA and AUML. Additionally we propose a way to compare different agent architectures for Context Aware System using agent interactions. So, in this paper, we describe the assignment of weight values to agents interaction in two different MAS architectures for Context Aware problems solving different scenarios inspired in FIPA standard negotiation protocols. 相似文献
28.
This study examined the mediating role of service climate in the prediction of employee performance and customer loyalty. Contact employees (N=342) from 114 service units (58 hotel front desks and 56 restaurants) provided information about organizational resources, engagement, and service climate. Furthermore, customers (N=1,140) from these units provided information on employee performance and customer loyalty. Structural equation modeling analyses were consistent with a full mediation model in which organizational resources and work engagement predict service climate, which in turn predicts employee performance and then customer loyalty. Further analyses revealed a potential reciprocal effect between service climate and customer loyalty. Implications of the study are discussed, together with limitations and suggestions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
Microstereophotolithography using a liquid crystal display as dynamic mask-generator 总被引:2,自引:0,他引:2
A new laser microstereophotolithography process has been developed in our laboratory to manufacture three-dimensional parts
with a high accuracy. As usual in laser stereophotolithography or laser microstereophotolithography, the part is manufactured
layer by layer by a light-induced space-resolved polymerization. Until now, in all the already existing microstereophotolithography
devices a layer is manufactured vector by vector, by moving the part beneath the initiating light source which remains motionless.
We developed a simpler and easier process, in which we can manufacture an entire layer by irradiating its whole surface only
once: we used a liquid crystal display as a dynamic generator of masks. In the device we set up, we need only one mobile element,
the z translator, all the others are fixed. We manufactured several different 3D microparts, in particular a piece of bevel
microgearing with helicoidal cogs, the volume of which is less than half a cubic millimetre.
Received: 14 December 1995 / Accepted: 16 September 1996 相似文献
30.
Most of donor-supported information technology (IT)–based projects developed or implemented in less-developed economies (LDEs) end up as complete or partial failures or unsustainable. Notably, a number of intra-organizational and external factors are associated with this problem, including inadequate infrastructure and human resource capacity, fragmented donor policy, and lack of policies to manage the sustainability problem. Accordingly, IT initiatives are often donor-driven, top-down, and hijacked by top managers who (normally) do not have adequate skills, but have enormous power to enforce such initiatives across organizational hierarchies. In analyzing the concepts from sustainability and institutionalization, key insights towards a better understanding of the problem of unsustainability are developed. It is argued that health information systems (HISs) become sustainable if they are institutionalized in the sense of being integrated into the everyday routine of the user organization. However, a sustainable HIS should also be flexible enough to allow changes as the user needs change. Moreover, introduction of a new HIS is not only a technical change, but requires the cultivation and institutionalization of a new kind of culture. Through a comparative case analysis of the HIS development and implementation processes in Tanzania and Mozambique, we have identified two sets of relationships, between the Ministry of Health (MoH) and donor agencies and between the MoH and software development agencies as critical and contributing factors to the unsustainability of a HIS. Given this setting, we highlight three key strategies for dealing with the problem of unsustainability in LDEs: (a) integration of a HIS, (b) local shaping of new cultures, and (c) cultivation approach to systems development. © 2005 Wiley Periodicals, Inc. 相似文献