全文获取类型
收费全文 | 3639篇 |
免费 | 229篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 53篇 |
综合类 | 2篇 |
化学工业 | 746篇 |
金属工艺 | 140篇 |
机械仪表 | 189篇 |
建筑科学 | 67篇 |
矿业工程 | 2篇 |
能源动力 | 134篇 |
轻工业 | 304篇 |
水利工程 | 20篇 |
石油天然气 | 8篇 |
无线电 | 694篇 |
一般工业技术 | 741篇 |
冶金工业 | 367篇 |
原子能技术 | 28篇 |
自动化技术 | 385篇 |
出版年
2024年 | 9篇 |
2023年 | 25篇 |
2022年 | 59篇 |
2021年 | 119篇 |
2020年 | 88篇 |
2019年 | 67篇 |
2018年 | 115篇 |
2017年 | 115篇 |
2016年 | 123篇 |
2015年 | 101篇 |
2014年 | 144篇 |
2013年 | 232篇 |
2012年 | 215篇 |
2011年 | 253篇 |
2010年 | 188篇 |
2009年 | 194篇 |
2008年 | 188篇 |
2007年 | 155篇 |
2006年 | 132篇 |
2005年 | 95篇 |
2004年 | 93篇 |
2003年 | 90篇 |
2002年 | 57篇 |
2001年 | 93篇 |
2000年 | 72篇 |
1999年 | 59篇 |
1998年 | 151篇 |
1997年 | 114篇 |
1996年 | 78篇 |
1995年 | 61篇 |
1994年 | 62篇 |
1993年 | 51篇 |
1992年 | 33篇 |
1991年 | 40篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有3880条查询结果,搜索用时 15 毫秒
91.
Joonho Shin Atanu Naskar Dongjoon Ko Semi Kim Kwang-sun Kim 《International journal of molecular sciences》2022,23(12)
Owing to the rapid spread of antibiotic resistance among Staphylococcus species, effective and low-risk alternatives to antibiotics are being actively searched. Thymol (THO), the most abundant component of the oil extracted from thyme, can be considered as a natural antibacterial alternative. However, the low antibacterial activity and non-selectivity of THO limit its usage as a universal anti-Staphylococcus agent. Herein, we report the bioconjugation of THO with ZnO nanoparticle (ZO), which resulted in the TZ nanocomposite (NC), as a potent and selective antibacterial agent against Staphylococcus species, particularly S. epidermidis. The cell-free supernatant (CFS) of ATCC 25923 cultures was employed for the production of TZ NC. Successful production of TZ NC was confirmed via X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and ultraviolet–visible (UV–Vis) studies. TZ NC had selective efficacy against Staphylococcus species, with MIC values 2–32-fold lower than THO. The antibacterial mechanisms of TZ NC are proposed to involve membrane rupture, suppression of biofilm formation, and modulation of new cell wall and protein-synthesis-associated cellular pathways. Its biocompatibility against HCT116 cells was also checked. Our findings suggest that the TZ nanocomposite could improve the selectivity and bactericidal activity of THO against target species. 相似文献
92.
93.
In this work the method of response surfaces was used for the purpose of drawing up a mathematical model for the calculation
(forecasting) of the adhesion of a flame sprayed coating of powdered aluminum on S 235 JR steel. Experimental work was conducted
according to a fractional central-composite design at three levels. The adhesion of the coatings made with combinations of
input parameters of the procedure according to the experiment plan mentioned is measured in line with the EN 582 standard.
A mathematical model was derived describing the dependence of the experimentally obtained adhesion values on the input parameters
of the procedure. The possibility of analyzing the influence of the parameters on the adhesion for a certain combination of
input parameters has been presented with the use of perturbation plots. 相似文献
94.
A vehicle head-up display (HUD) has a semitransparent property that utilizes a method of projecting light onto the windshield. The semitransparent characteristic of the HUD generates continuous superimposition between the “HUD graphic” and “road environment events.” This study aims to determine the effects of HUD use on elderly driving. Two age groups (elderly, younger) performed tasks (speed monitoring, navigation) utilizing two types of display (HUD, head-down display) in two different circumstances (high superimposition level, low superimposition level). Subject performance was evaluated by having the subjects execute a secondary display task while performing a primary driving task with an eye-tracking task. In addition, the degree of driver visual distraction was verified through the measurement of display glance duration. The results showed that an increase in superimposition negatively affected driver glance duration independent of age. However, the use of HUD in low superimposition situations showed relative advantages with regard to display use independent of age. This study confirmed that the negative effects of HUD use need to be considered during the selection of HUD information and display location. In particular, this study verifies that special attention should be given to the negative effects of superimposition of text information for use by an elderly population. 相似文献
95.
The flash point is one of the most important properties of flammable liquids. This study proposes a support vector regression
(SVR) model to predict the flash points of 792 organic compounds from the DIPPR 801 database. The input variables of the model
consist of 65 different functional groups, logarithm of molecular weight and their boiling points in this study. Cross-validation
and particle swarm optimization were adopted to find three optimal parameters for the SVR model. Since the prediction largely
relies on the selection of training data, 100 training data sets were randomly generated and tested. Moreover, all of the
organic compounds used in this model were divided into three major classes, which are non-ring, aliphatic ring, and aromatic
ring, and a prediction model was built accordingly for each class. The prediction results from the three-class model were
much improved than those obtained from the previous works, with the average absolute error being 5.11–7.15 K for the whole
data set. The errors in calculation were comparable with the ones from experimental measurements. Therefore, the proposed
model can be implemented to determine the initial flash point for any new organic compounds. 相似文献
96.
Chia-Ling Ko Wen-Cheng Chen Jian-Chih Chen Ying- Hui Wang Chi-Jen Shih Yu-Chang Tyan Chun-Cheng Hung Jen-Chyan Wang 《Materials science & engineering. C, Materials for biological applications》2013,33(6):3537-3544
This study aims to evaluate further the performance of a platelet-rich plasma (PRP) additive incorporated with calcium phosphate bone cement (CPC) in vitro to prove its efficiency as bone graft substitutes and its compatibility to be incorporated into the CPC with other techniques in clinical restoration in vivo. The growth factor release ability and the osteogenic evaluation of PRP, CPC, and PRP/CPC testing groups with 5, 10, and 15 wt.% PRP were compared in vitro. Four groups were measured using non-decalcified staining methods in vivo, which include the testing group of 10 wt.% PRP/CPC selected from the evaluation in vitro, by using both the autograft with rabbit trabecular and CPC-only as comparison groups and the group without grafting material as the control sample. The results obtained through specimen immersion show that growth factor release and alkaline phosphatase activities after osteoprogenitor cell culture had a significantly better effect on 10 and 15 wt.% PRP/CPC than on the other groups in vitro. Analysis results suggest that PRP was still retained in the CPC matrix even after 32 days of immersion. The results in vivo show that the histology of the autograft bone and the control group without grafting material exhibited fibrous connective and adipose tissues, which obviously filled the created cavity even at nine weeks after the operation. Osteoregeneration was more successful in the PRP-additive group, which accumulated bone remodeling than in the other groups. In conclusion, CPC could be a potential carrier with adequate PRP additives that bear a therapeutic potential for enhanced bone tissue regeneration. 相似文献
97.
98.
Organic whey as a source of Lactobacillus strains with selected technological and antimicrobial properties 下载免费PDF全文
Anna Rzepkowska Dorota Zielińska Aleksandra Ołdak Danuta Kołożyn‐Krajewska 《International Journal of Food Science & Technology》2017,52(9):1983-1994
Twenty‐five strains, isolated from raw, non‐pasteurised, organic whey samples, were identified phenotypically and genotypically. Biochemical tests were performed, and enzyme profiles, antibiotic resistance and antimicrobial properties were investigated. Sixteen strains were identified as genus Lactobacillus. Based on 16S rDNA gene sequence, the strains were identified as Lb. plantarum and Lb. fermentum. All of the strains had β‐galactosidase activity, and some of them reduced nitrate content. All strains utilised carbohydrates. The tested strains were characterised by low or average lipolytic and esterolytic activity. Moreover, the strains showed low proteolytic activity which is advantageous for their use as starter cultures for foods with low protein content. Strains Lb. fermentum S20, SM1, SM3, S2R and Lb. plantarum SM5 produced harmful N‐acetyl‐β‐glucosaminidase; moreover, the strain S20 produced also β‐glucuronidase. None of the strains produced α‐chymotrypsin. In phenotypic studies, most of the test strains were susceptible to gentamicin, ampicillin, tetracycline, chloramphenicol, penicillin and erythromycin. Strains Lb. plantarum S1 and Lb. fermentum S4, S7, S8, S10, SM1 and SM3 did not possess any transfer resistance genes. Antagonistic activity of the culture LAB strains was assessed as high or moderate in relation to the indicator strains, with the greatest zones of inhibition for E.coli and the smallest for L. monocytogenes ATCC 15313. This study reveals that the LAB strains isolated from organic whey have high potential for food application. Some strains of species Lb. fermentum (S4, S7, S8, S10) have been identified as the best candidates. 相似文献
99.
Sónia Simões Filomena Viana Mustafa Koçak A. Sofia Ramos M. Teresa Vieira Manuel F. Vieira 《Journal of Materials Engineering and Performance》2012,21(5):678-682
In this article, the characterization of the interfacial structure of diffusion bonding a TiAl alloy is presented. The joining
surfaces were modified by Ni/Al reactive multilayer deposition as an alternative approach to conventional diffusion bonding.
TiAl substrates were coated with alternated Ni and Al nanolayers. The nanolayers were deposited by dc magnetron sputtering
with 14 nm of period (bilayer thickness). Joining experiments were performed at 900 °C for 30 and 60 min with a pressure of
5 MPa. Cross sections of the joints were prepared for characterization of their interfaces by scanning electron microscopy
(SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), high resolution TEM (HRTEM),
energy dispersive x-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Several intermetallic compounds form
at the interface, assuring the bonding of the TiAl. The interface can be divided into three distinct zones: zone 1 exhibits
elongated nanograins, very small equiaxed grains are observed in zone 2, while zone 3 has larger equiaxed grains. EBSD analysis
reveals that zone 1 corresponds to the intermetallic Al2NiTi and AlNiTi, and zones 2 and 3 to NiAl. 相似文献
100.
In this study, anion exchange membranes having various quaternary ammonium groups were prepared by using a radiation-induced graft polymerization method and followed by subsequent treatment of films with amines. FT-IR and SEM-EDX techniques were employed to monitor the reaction progress. The cross-sectional distribution of the anionic exchange functional groups through the membranes has also been investigated using SEM-EDX technique. The results reveal that the anion exchange groups were found to be evenly distributed throughout the membranes. It was also observed that the physico-chemical properties of the anion exchange membranes such as water uptake, ionic conductivity, thermal stability, chemical stability, mechanical properties, and dimensional stability are largely influenced by the chemical structure of the quaternary ammonium moiety which is attached to the graft chains. Among the prepared anion exchange membranes, the membrane having mono-quaternized 1,4-diazabicyclo[2,2,2]octane moiety was found to have both enhanced chemical and dimensional stabilities, while the others having quaternized trimethylamine or bis-quaternized 1,4-diazabicyclo[2,2,2]octane have the decreased dimensional and chemical stabilities. 相似文献