全文获取类型
收费全文 | 5449篇 |
免费 | 395篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 38篇 |
综合类 | 1篇 |
化学工业 | 991篇 |
金属工艺 | 85篇 |
机械仪表 | 87篇 |
建筑科学 | 162篇 |
矿业工程 | 7篇 |
能源动力 | 91篇 |
轻工业 | 1014篇 |
水利工程 | 68篇 |
石油天然气 | 18篇 |
无线电 | 229篇 |
一般工业技术 | 828篇 |
冶金工业 | 1445篇 |
原子能技术 | 14篇 |
自动化技术 | 770篇 |
出版年
2024年 | 6篇 |
2023年 | 40篇 |
2022年 | 46篇 |
2021年 | 116篇 |
2020年 | 109篇 |
2019年 | 135篇 |
2018年 | 190篇 |
2017年 | 201篇 |
2016年 | 219篇 |
2015年 | 179篇 |
2014年 | 233篇 |
2013年 | 448篇 |
2012年 | 347篇 |
2011年 | 331篇 |
2010年 | 251篇 |
2009年 | 249篇 |
2008年 | 240篇 |
2007年 | 223篇 |
2006年 | 120篇 |
2005年 | 102篇 |
2004年 | 115篇 |
2003年 | 98篇 |
2002年 | 106篇 |
2001年 | 80篇 |
2000年 | 71篇 |
1999年 | 85篇 |
1998年 | 546篇 |
1997年 | 301篇 |
1996年 | 196篇 |
1995年 | 100篇 |
1994年 | 79篇 |
1993年 | 78篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 20篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 19篇 |
1976年 | 28篇 |
1970年 | 1篇 |
排序方式: 共有5848条查询结果,搜索用时 484 毫秒
111.
112.
Carlos A. García-Velásquez Valentina Aristizábal-Marulanda Carlos A. Cardona 《Clean Technologies and Environmental Policy》2018,20(7):1599-1613
In this paper, a techno-economic and environmental assessment is performed to compare the stand-alone process and biorefinery ways to produce biodiesel, ethanol and butanol as potential cases for bioenergy production using fresh fruit bunches as raw material. Different levels of integration are considered (e.g., mass and energy integration, non-conventional technologies) along with the analysis of the process scale to determine the economic profitability and environmental impacts of the proposed cases. The results demonstrated that the biodiesel production based on the biorefinery concept has a positive effect on the profitability of the stand-alone process at different scales. The economic results were compared with data reported in the literature. Furthermore, the life cycle analysis of the proposed cases suggested that the deployment of the biorefinery concept at different levels of integration in the oil palm supply chain reduced the environmental impact of the biodiesel production, which was selected as the hotspot of the evaluated cases. 相似文献
113.
A Camacho Ojeda E Llanes Montero C García Requena M Romero Corchero 《Canadian Metallurgical Quarterly》1998,21(235):17-20
The quality of care within our health care system depends upon an active and dynamic communication which bridges the different levels of care (primary and hospital) and will permit a continuity of services between the distinct parts. To insure this success, the authors propose an outpatient nursing record that will follow the patient upon his or her discharge. This record, to be called the "Discharged Patient Report", will be directed to other medical professionals so that they can be informed of previous treatments that the patient has received. Included in the report will be items such as; the previous nursing interactions that were used on the patient, how problems were resolved, possible other solutions, and health care information given to the patient. Using the report in this way will give us a great tool to know our patients and better understand how to serve them. 相似文献
114.
Analysis of interferograms with a spatial radial carrier or closed fringes and its holographic analogy 总被引:2,自引:0,他引:2
It is well known that an interferogram can be demodulated to find the wave-front shape if a linear carrier is introduced. We show that it can also be demodulated if it has many closed fringes or a circular carrier appears. A basic assumption is that the carrier fringes are of a bandwidth adequate to contain the wave-front distortion. This phase determination, called here demodulation, is made in the space domain, as opposed to demodulation in Fourier space, but the low-pass filter characteristics must be properly chosen. For academic purposes a holographic analogy of this demodulation process is also presented, which shows that the common technique of multiplying by a sine function and a cosine function is equivalent to holographically reconstructing with a tilted-flat wave front. Alternatively, a defocused (spherical) wave front can be used as a reference to perform the reconstruction or demodulation of some closed-fringe interferograms. 相似文献
115.
González-Fandos ME Sierra ML García-López ML Otero A Sanz J Moreno B 《Meat science》1996,43(3-4):255-263
The effect of meat cultures (non lactic acid bacteria) on the growth and production of enterotoxins and thermonuclease by Staphylococcus aureus was studied. Micrococcus varians did not affect growth nor the synthesis of metabolites. Levels of enterotoxins A, B and D produced by the respective S. aureus strains were reduced by S. xylosus, S. saprophyticus and S. carnosus. The two latter species prevented production of enterotoxin C1 and S. xylosus markedly reduced the amount produced. The three coagulase-negative staphylococci showed little inhibitory effect on the growth of S. aureus. Penicillium nalgiovense did not show inhibitory activity against the four S. aureus strains. Debaryomyces hansenii slightly inhibited growth of the enterotoxin A-producing strain, but reduced enterotoxin synthesis at 30 °C. Thermonuclease was detected whenever enterotoxins were detected though the influence of the effector organism was dependent on the test strain. 相似文献
116.
A method for the calculation of the fractional Fourier transform (FRT) by means of the fast Fourier transform (FFT) algorithm is presented. The process involves mainly two FFT's in cascade; thus the process has the same complexity as this algorithm. The method is valid for fractional orders varying from -1 to 1. Scaling factors for the FRT and Fresnel diffraction when calculated through the FFT are discussed. 相似文献
117.
JA Ortu?o-Cortés L Quintana-Tomás A García-García 《Canadian Metallurgical Quarterly》1996,19(2):47-51
1.5% Capsaicin (Cap) or Vehicle was respectively used to treat the right or left sciatic nerve in 20 Sprague-Dawley rats. On the seventh day, the 20 rats were at random divided into electroacupuncture (EA) group and non-EA group, the spinal cord corresponding to the afferent segments of sciatic nerve was taken out for observing the changes of acetylcholinesterase (AChE) activity and [3H]-quinuelidinylbenzylate (QNB) binding sites in the spinal dorsal horn (SDH). The results were as follows: (1) EA "Huantiao" could enhance AChE activity in the SDH and decrease [3H]-QNB binding sites; (2) Cap treating sciatice nerve could weaken AChE activity in the SDH and merease [3H]-QNB binding sites; (3) Cap treatment could inhibit or partially inhibit the actions of EA as above. The results indicated that ACh participated in the primary afferent of acupuncture information and might exist in Cap-sensitive neurons. 相似文献
118.
Cuenca Angel García Pedro Albertos Pedro Salt Julián 《International Journal of Control, Automation and Systems》2011,9(6):1194-1202
International Journal of Control, Automation and Systems - This paper presents a Non-Uniform Predictor-Observer (NUPO) based control approach in order to deal with two of the main problems related... 相似文献
119.
Sergio S��nchez Garc��a Ana G��mez Oliva Emilia P��rez Belleboni Iv��n Pau de la Cruz 《International Journal of Information Security》2011,10(6):351-372
At present, many countries allow citizens or entities to interact with the government outside the telematic environment through
a legal representative who is granted powers of representation. However, if the interaction takes place through the Internet,
only primitive mechanisms of representation are available, and these are mainly based on non-dynamic offline processes that
do not enable quick and easy identity delegation. This paper proposes a system of dynamic delegation of identity between two
generic entities that can solve the problem of delegated access to the telematic services provided by public authorities.
The solution herein is based on the generation of a delegation token created from a proxy certificate that allows the delegating
entity to delegate identity to another on the basis of a subset of its attributes as delegator, while also establishing in
the delegation token itself restrictions on the services accessible to the delegated entity and the validity period of delegation.
Further, the paper presents the mechanisms needed to either revoke a delegation token or to check whether a delegation token
has been revoked. Implications for theory and practice and suggestions for future research are discussed. 相似文献
120.
César García-Osorio Aida de Haro-García Nicolás García-Pedrajas 《Artificial Intelligence》2010,174(5-6):410-441
Instance selection is becoming increasingly relevant due to the huge amount of data that is constantly being produced in many fields of research. Although current algorithms are useful for fairly large datasets, scaling problems are found when the number of instances is in the hundreds of thousands or millions. When we face huge problems, scalability becomes an issue, and most algorithms are not applicable.Thus, paradoxically, instance selection algorithms are for the most part impracticable for the same problems that would benefit most from their use. This paper presents a way of avoiding this difficulty using several rounds of instance selection on subsets of the original dataset. These rounds are combined using a voting scheme to allow good performance in terms of testing error and storage reduction, while the execution time of the process is significantly reduced. The method is particularly efficient when we use instance selection algorithms that are high in computational cost. The proposed approach shares the philosophy underlying the construction of ensembles of classifiers. In an ensemble, several weak learners are combined to form a strong classifier; in our method several weak (in the sense that they are applied to subsets of the data) instance selection algorithms are combined to produce a strong and fast instance selection method.An extensive comparison of 30 medium and large datasets from the UCI Machine Learning Repository using 3 different classifiers shows the usefulness of our method. Additionally, the method is applied to 5 huge datasets (from three hundred thousand to more than a million instances) with good results and fast execution time. 相似文献