全文获取类型
收费全文 | 17812篇 |
免费 | 1285篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 340篇 |
综合类 | 52篇 |
化学工业 | 4014篇 |
金属工艺 | 559篇 |
机械仪表 | 459篇 |
建筑科学 | 840篇 |
矿业工程 | 123篇 |
能源动力 | 301篇 |
轻工业 | 2599篇 |
水利工程 | 134篇 |
石油天然气 | 25篇 |
武器工业 | 1篇 |
无线电 | 1135篇 |
一般工业技术 | 4989篇 |
冶金工业 | 448篇 |
原子能技术 | 159篇 |
自动化技术 | 2932篇 |
出版年
2023年 | 245篇 |
2022年 | 154篇 |
2021年 | 400篇 |
2020年 | 350篇 |
2019年 | 324篇 |
2018年 | 658篇 |
2017年 | 671篇 |
2016年 | 732篇 |
2015年 | 608篇 |
2014年 | 746篇 |
2013年 | 1492篇 |
2012年 | 893篇 |
2011年 | 1077篇 |
2010年 | 930篇 |
2009年 | 830篇 |
2008年 | 944篇 |
2007年 | 936篇 |
2006年 | 650篇 |
2005年 | 505篇 |
2004年 | 417篇 |
2003年 | 423篇 |
2002年 | 438篇 |
2001年 | 361篇 |
2000年 | 307篇 |
1999年 | 231篇 |
1998年 | 190篇 |
1997年 | 196篇 |
1996年 | 173篇 |
1995年 | 170篇 |
1994年 | 140篇 |
1993年 | 120篇 |
1992年 | 114篇 |
1991年 | 93篇 |
1990年 | 85篇 |
1989年 | 72篇 |
1988年 | 75篇 |
1987年 | 72篇 |
1985年 | 149篇 |
1984年 | 163篇 |
1983年 | 103篇 |
1982年 | 106篇 |
1981年 | 130篇 |
1980年 | 101篇 |
1979年 | 83篇 |
1978年 | 88篇 |
1977年 | 71篇 |
1976年 | 73篇 |
1975年 | 83篇 |
1974年 | 63篇 |
1973年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Ute Förster Katharina Lommel Daniel Sauter Christian Grünewald Joachim W. Engels Prof. Dr. Josef Wachtveitl Prof. Dr. 《Chembiochem : a European journal of chemical biology》2010,11(5):664-672
A series of short RNA duplexes containing one or two 1‐ethynylpyrene‐modified adenine bases was synthesised. The melting behaviour of these duplexes was examined by monitoring temperature‐dependent pyrene fluorescence. In the singly modified RNA duplexes, the bases flanking the ethynylpyrene‐rA were varied to examine the sequence specificity of the fluorescence change of pyrene upon RNA hybridisation. Because an increase in pyrene fluorescence upon melting of the duplex can be correlated with intercalation of pyrene, and a decrease is usually associated with the position of pyrene outside the strand, a relationship between the flanking bases and the tendency of the dye to intercalate has been established. It was found that pyrene intercalation is less likely to take place if the modified base is flanked only by A–U base pairs. Flanking G–C base pairs, even only in the 5′‐direction of the modified base, will favour intercalation. In addition, we examined a doubly modified compound that had a pyrene located on each strand. The spectra indicated that the two pyrenes were close enough for interaction. Upon melting of the strand, a fluorescence blue shift corresponding to the dissociation of the pyrene–pyrene complex could be observed in addition to the intensity effect already known from the singly modified compounds. Two melting curves based on the different properties of the fluorophore could be extracted, leading to different melting points corresponding to the global duplex melting and to the change of local pyrene environment, respectively. 相似文献
932.
933.
Döne Demirgöz Rodrigo Navarro Mónica Pérez Helmut Reinecke Alberto Gallardo 《应用聚合物科学杂志》2010,115(2):896-900
2‐Hydroxyethylmethacrylate (HEMA) and acrylamide (AA) have been copolymerized via free radical mechanism, in the presence of 5 mol % of four different crosslinker systems, the symmetric ethylenglycoldimethacrylate (EGDMA), bisacrylamide (BIS), a mixture of EGDMA and BIS, and the asymmetric acrylamideethylenmethacrylate (METAA). The polymerizations have been monitored with a rheometer, exhibiting the gel obtained with the asymmetric METAA, an elastic modulus that is dramatically increased compared with those of the gels prepared with the other three crosslinker systems. A kinetic analysis using the terminal model has been used to build probabilistic surfaces that give information about how the crosslinker is incorporated into the network. This analysis shows a high dissimilarity between the reactions using the asymmetric and the mixture of symmetric crosslinkers, what has been correlated to the difference in modulus. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
934.
Loop closing in vision based SLAM applications is a difficult task. Comparing new image data with all previously acquired image data is practically impossible because of the high computational costs. Most approaches therefore compare new data with only a subset of the old data, for example by sampling the data over time or over space by using a position estimate. In this paper, we propose a more natural approach, which dynamically determines a subset of images that best describes the complete image data in the space of all previously seen images. The actual problem of finding such a subset is called the “Connected Dominating Set” (CDS) problem, which is well studied in the field of graph theory. Application on large indoor datasets results in approximately the same map using only 13% of the computational resources with respect to comparing with all previous images. Also, it outperforms other sampling approaches. The proposed method is particularly beneficial for realistic mapping scenarios including moving objects and persons, motion blur and changing light conditions.1 相似文献
935.
Zandra Arwidsson Kristin Elgh-Dalgren Thomas von Kronhelm Ragnar Sjöberg Bert Allard Patrick van Hees 《Journal of hazardous materials》2010,173(1-3):697-704
Removal of Cu, Pb, and Zn by the action of the two biodegradable chelating agents [S,S]-ethylenediaminedisuccinic acid (EDDS) and methylglycinediacetic acid (MGDA), as well as citric acid, was tested. Three soil samples, which had previously been treated by conventional soil washing (water), were utilized in the leaching tests. Experiments were performed in batches (0.3 kg-scale) and with a WTC-mixer system (Water Treatment Construction, 10 kg-scale). EDDS and MGDA were most often equally efficient in removing Cu, Pb, and Zn after 10–60 min. Nonetheless, after 10 d, there were occasionally significant differences in extraction efficiencies. Extraction with citric acid was generally less efficient, however equal for Zn (mainly) after 10 d. Metal removal was similar in batch and WTC-mixer systems, which indicates that a dynamic mixer system could be used in full-scale. Use of biodegradable amino polycarboxylic acids for metal removal, as a second step after soil washing, would release most remaining metals (Cu, Pb and Zn) from the present soils, however only after long leaching time. Thus, a full-scale procedure, based on enhanced metal leaching by amino polycarboxylic acids from soil of the present kind, would require a pre-leaching step lasting several days in order to be efficient. 相似文献
936.
Dermal uptake of phthalates from clothing: Comparison of model to human participant results
下载免费PDF全文
![点击此处可从《Indoor air》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this research, we extend a model of transdermal uptake of phthalates to include a layer of clothing. When compared with experimental results, this model better estimates dermal uptake of diethylphthalate and di‐n‐butylphthalate (DnBP) than a previous model. The model predictions are consistent with the observation that previously exposed clothing can increase dermal uptake over that observed in bare‐skin participants for the same exposure air concentrations. The model predicts that dermal uptake from clothing of DnBP is a substantial fraction of total uptake from all sources of exposure. For compounds that have high dermal permeability coefficients, dermal uptake is increased for (i) thinner clothing, (ii) a narrower gap between clothing and skin, and (iii) longer time intervals between laundering and wearing. Enhanced dermal uptake is most pronounced for compounds with clothing–air partition coefficients between 104 and 107. In the absence of direct measurements of cotton cloth–air partition coefficients, dermal exposure may be predicted using equilibrium data for compounds in equilibrium with cellulose and water, in combination with computational methods of predicting partition coefficients. 相似文献
937.
938.
Cornelia Wiegand Tanja Hansen Johanna Köhnlein Ines Exner Marlen Damisch-Pohl Peter Schott 《纺织学会志》2018,109(7):891-902
Biocompatibility of six different compression stockings and cytotoxic effects were determined using HaCaT keratinocytes, L929 mouse fibroblasts, primary adult and juvenile keratinocytes Cells were quantified using a luminometric ATP assay and the photometric BCA test. Cytotoxic effects were determined by LDH release. An area-based extraction ratio of 1.25 cm2:mL could be shown to be superior to the weight-based extraction of test material. Extraction medium should be an acidic sweat solution as this helps to recreate in vivo conditions. Monolayer cultures of HaCaT keratinocytes or L929 mouse fibroblasts should be used for testing. Primary adult keratinocytes or primary juvenile keratinocytes can also be used. For the latter, testing under DMEM with FCS is recommended to achieve comparable results. It was found that the compression stockings tested exhibited no negative influence on cell viability in vitro and no direct cytotoxic effects measured as release of LDH. Hence, good biocompatibility could be asserted. 相似文献
939.
P Gillard L Courty S De Persis J.F Lagrange C Boulnois I Gökalp 《Journal of Energetic Materials》2018,36(3):362-374
Ignition and combustion characteristics of a low-vulnerability propellant based on RDX are studied experimentally. Ignition is obtained using a laser diode. Experiments are performed in a cylindrical closed-volume reactor for different initial pressures and initial propellant masses under nitrogen and argon surrounding atmospheres. Ignition delays, maximal overpressures, and propagation rates are obtained for different initial pressures and laser powers. Thermodynamic predictions of overpressures are also compared with experimental ones. Finally, ignition probabilities for different laser powers and gaseous atmospheres are investigated using a revised Langlie method. 相似文献
940.
Samples of (Cu46Zr46Al8)100?xZx metallic glass forming alloys with diameters 2–6 mm were prepared by injection casting. The effect of minor amounts of elements Z = Gd, Co and Re with positive enthalpy of mixing within the Gd–Zr, Cu–Co and Cu–Re terminal systems was compared. The addition of Gd up to x = 2 slightly enhances the glass forming ability, Co reduces the critical diameter of bulk metallic glass formation, whereas even for small fractions of Re bulk samples were crystalline, but only amorphous splats can be prepared. Both Gd and Co diminish the crystallization temperature Tx with respect to the Cu46Zr46Al8 master alloy, but in Re-bearing splats Tx is increased. Alloying with optimum amounts of Gd and Co up to x = 2 leads to plastic deformability of rods, 2 and 3 mm in diameter, in comparison with the brittle Cu46Zr46Al8 bulk metallic glass. 相似文献