全文获取类型
收费全文 | 2431篇 |
免费 | 169篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 875篇 |
金属工艺 | 12篇 |
机械仪表 | 29篇 |
建筑科学 | 89篇 |
矿业工程 | 3篇 |
能源动力 | 45篇 |
轻工业 | 883篇 |
水利工程 | 12篇 |
石油天然气 | 23篇 |
无线电 | 89篇 |
一般工业技术 | 269篇 |
冶金工业 | 94篇 |
原子能技术 | 1篇 |
自动化技术 | 163篇 |
出版年
2024年 | 6篇 |
2023年 | 20篇 |
2022年 | 125篇 |
2021年 | 135篇 |
2020年 | 56篇 |
2019年 | 58篇 |
2018年 | 73篇 |
2017年 | 69篇 |
2016年 | 87篇 |
2015年 | 81篇 |
2014年 | 98篇 |
2013年 | 181篇 |
2012年 | 159篇 |
2011年 | 200篇 |
2010年 | 125篇 |
2009年 | 145篇 |
2008年 | 136篇 |
2007年 | 126篇 |
2006年 | 97篇 |
2005年 | 78篇 |
2004年 | 71篇 |
2003年 | 47篇 |
2002年 | 56篇 |
2001年 | 33篇 |
2000年 | 31篇 |
1999年 | 33篇 |
1998年 | 38篇 |
1997年 | 38篇 |
1996年 | 28篇 |
1995年 | 23篇 |
1994年 | 14篇 |
1993年 | 20篇 |
1992年 | 21篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 16篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有2600条查询结果,搜索用时 15 毫秒
1.
Juana Maria de Lourdes Medina-Contreras Patrick Mailloux-Salinas Juventino III Colado-Velazquez Norma Leticia Gomez Viquez Gómez-Viquez Rodrigo Velázquez-Espejel Ana del Carmen Susunaga-Notario David Julian Arias-Chávez Guadalupe Bravo 《Journal of the science of food and agriculture》2020,100(7):3212-3219
2.
Javier Roca-Pardiñas Carmen Cadarso-Suárez María J. Lado 《Computational statistics & data analysis》2008,52(4):1958-1970
In many applications, the joint effect of two continuous covariates on the target binary response may vary across groups defined by levels of a given factor. A testing procedure that would enable this type of surface-by-factor interactions to be detected has been designed. To accomplish this goal, a logistic generalized additive model (GAM) with bivariate continuous interactions varying across groups defined by levels of a factor is considered. A local scoring algorithm based on local linear kernel smoothers was implemented to estimate the proposed logistic GAM. Bootstrap resampling techniques were used for the purpose of testing for factor-by-surface interactions. Given the high computational cost involved, binning techniques were used to speed up computation in the estimation and testing processes. The adequacy of the bootstrap-based test was assessed by means of a simulation study. If a factor-by-surface interaction is detected in the model, it is then established that the use of the odds-ratio curves is very useful in obtaining a direct interpretation of the fitted model. The benefits of using this methodology when analyzing real data are illustrated by applying the technique to the outputs produced by a computerized system dedicated to the early detection of breast cancer. 相似文献
3.
This paper describe an approach for improving the data quality of corporate sources when databases are used for bibliometric
purposes. Research management relies on bibliographic databases and citation index systems as analytical tools, yet the raw
resources for bibliometric studies are plagued by a lack of consistency in fied formatting for institution data. The present
contribution puts forth a Natural Language Processing (NLP)-oriented method for the identification of the structures guiding
corporate data and their mapping into a standardized format. The proposed unification process is based on the definition of
address patterns and the ensuing application of Enhanced Finite-State Transducers (E-FST). Our procedure was tested on address
formats downloaded from the INSPEC, MEDLINE and CAB Abstracts. The results demonstrate the helpfulness of the method as long
as close control of errors is exercised as far as the formats to be unified. The computational efficacy of the model is noteworthy,
due to the fact that it is firmly guided by the definition of data in the application domain. 相似文献
4.
The effect of crude oil n-paraffin molecular weight distribution on wax crystallization risk was studied. Sixteen highly paraffinic crude oils from Eastern Venezuela were characterized, in terms of hydrocarbon family distribution, by High Temperature Simulate Distillation (HTSD), Gel Permeation Chromatography (GPC), and wax content. n-Paraffin chain length was correlated with crude oil cloud point and pour point. It was demonstrated that high molecular weight linear paraffins are responsible for crude oil wax precipitation. A quantitative correlation between molecular weight distribution and crude oil flowing properties was also obtained. It was found that the wider the molecular weight distribution, the lower is the wax crystallization risk. Blends of different paraffinic crude oils were prepared and their flowing properties were evaluated in comparison with the original crudes. Cloud points below the mean value were obtained. In some cases, a synergistic effect was observed (cloud points below the minimum of the two crude oils). Blends of some of these crudes with condensates afforded improvements on crude oil flow and a reduction of wax crystallization tendency (cloud point). This phenomenon can be attributed to a combination of two factors: I. increases in C24-n-paraffins, and II. a wider molecular weight distribution. 相似文献
5.
Phase separation during polymerization was studied in a model system consisting of a diepoxide based on diglycidyl ether of bisphenol A (DGEBA), variable amounts of ethylenediamine (EDA) and the mass of castor oil (CO) necessary to obtain a mass fraction equal to 0-15 in a final system where the stoichiometric ratio of amine to epoxy equivalents, r, was equal to 1. A two-step polymerization process was performed by curing first a system with r = 0-5, during variable times before phase separation, and then carrying the system to r = 1. Thermodynamic analysis of samples with different r values led to a linear relationship between the Flory-Huggins interaction parameter and r. The concentration (P) and average size (D?) of dispersed-phase particles followed opposite trends, i.e. P increased while D? decreased, when either r was increased or the time of curing in the first step of a two-step process was decreased. This was explained by assuming that the competition between nucleation and growth was determined by the viscosity at the cloud point, ηcp. Low values of ηcp favoured growth over nucleation and led to fewer but larger particles. 相似文献
6.
Ionomeric composites based on sepiolite and hydrogenated poly(styrene butadiene) block copolymer were obtained and characterized from a microstructural and electrical point of view. Before blending, because of the high silanol group concentration in the sepiolite, the latter could be organophilized with suitable coupling agents. The resulting materials were easily processed into thin films or membranes 0.2–0.4 mm thick, their conductivity in some cases approaching 10?1 S/cm. Their suitability for film formation and good electrical properties indicate potential applications as electrolytes in polymer fuel cells. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3512–3519, 2002 相似文献
7.
8.
Patrícia Carvalho de Souza André Salim Khayat Igor Chamon Seligmann Rommel Mario Rodríguez Burbano 《Biocell》2008,32(2):207-210
The collared peccary (Tayassu tajacu) is widely distributed over the American continent, being found from the south of the USA to the north of Argentina. In Brazil, it is spread all over the country, being one of the potential species to be raised in captivity. Therefore, the cytogenetic techniques could be a potential tool for reproductive monitoring of animals raised in captivity, mainly when destined for commercial purposes. This study had the objective of determining the chromosome number of two populations raised in captivity and characterizing them by GTG banding. For this purpose, an analysis was made of mitotic metaphases obtained from lymphocyte cultures made from blood samples of 11 animals, six of which from the Northeast and five from the North of Brazil. The results of this analysis showed the same karyotype pattern for the species (2n=30 chromosomes and NF=48), besides corresponding to the South American pattern of the species, i.e., without a translocation between autosomes 1 and 8, chromosome X acrocentric, and no differences were found between the two populations studied. However, chromosomal polymorphisms were observed compared to data from the literature on populations from North and South America. 相似文献
9.
F Javier Álvarez‐Hornos Carmen Gabaldón Vicente Martínez‐Soria Paula Marzal Josep‐Manuel Penya‐roja 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(5):643-653
BACKGROUND: Two peat biofilters were used for the removal of toluene from air for one year. One biofilter was fed with pure toluene and the other received 1:1 (by weight) ethyl acetate:toluene mixture. RESULTS: The biofilters were operated under continuous loading: the toluene inlet load (IL) at which 80% removal occurred was 116 g m?3 h?1 at 57 s gas residence time. Maximum elimination capacity of 360 g m?3 h?1 was obtained at an IL of 745 g m?3 h?1. The elimination of toluene was inhibited by the presence of ethyl acetate. Intermittent loading, with pollutants supplied for 16 h/day, 5 days/week, did not significantly affect the removal efficiency (RE). Biomass was fully activated in 2 h after night closures, but 6 h were required to recover RE after weekend closures. Live cell density remained relatively constant over the operational period, while the dead cell fraction increased. Finally, a 15 day starvation period was applied and operation then re‐started. Performance was restored with similar re‐acclimatization period to that after weekend closures, and a reduction in dead cell fraction was observed. CONCLUSION: This study demonstrates the capacity of the system to handle intermittent loading conditions that are common in industrial practices, including long‐term starvation. Copyright © 2008 Society of Chemical Industry 相似文献
10.
Baudilio Coto Carmen Martos Jos L. Pea Juan J. Espada María D. Robustillo 《Fuel》2008,87(10-11):2090-2094
Wax precipitation is one of the most important flow assurance problems. Unfortunately, experimental data are very scarce to confirm existing models for prediction of such precipitation problem. This work reports a new experimental method. Multistage fractional wax precipitation was carried out by decreasing the temperature of crude oil. No solvent dilution was used, so the effect of solvent on temperature wax precipitation was avoided. The reproducibility of the method was tested with comparable results. The precipitation curve and the wax appearance temperature were obtained for two crude oils with different chemical nature using the reported method. 相似文献