全文获取类型
收费全文 | 22118篇 |
免费 | 1578篇 |
国内免费 | 927篇 |
专业分类
电工技术 | 360篇 |
技术理论 | 1篇 |
综合类 | 1483篇 |
化学工业 | 2759篇 |
金属工艺 | 765篇 |
机械仪表 | 2282篇 |
建筑科学 | 458篇 |
矿业工程 | 322篇 |
能源动力 | 201篇 |
轻工业 | 4851篇 |
水利工程 | 66篇 |
石油天然气 | 687篇 |
武器工业 | 97篇 |
无线电 | 1209篇 |
一般工业技术 | 5764篇 |
冶金工业 | 746篇 |
原子能技术 | 167篇 |
自动化技术 | 2405篇 |
出版年
2024年 | 128篇 |
2023年 | 433篇 |
2022年 | 556篇 |
2021年 | 779篇 |
2020年 | 758篇 |
2019年 | 736篇 |
2018年 | 727篇 |
2017年 | 822篇 |
2016年 | 774篇 |
2015年 | 660篇 |
2014年 | 1073篇 |
2013年 | 1345篇 |
2012年 | 1445篇 |
2011年 | 1407篇 |
2010年 | 1206篇 |
2009年 | 1345篇 |
2008年 | 1004篇 |
2007年 | 1383篇 |
2006年 | 1329篇 |
2005年 | 1080篇 |
2004年 | 1018篇 |
2003年 | 863篇 |
2002年 | 740篇 |
2001年 | 605篇 |
2000年 | 490篇 |
1999年 | 414篇 |
1998年 | 271篇 |
1997年 | 231篇 |
1996年 | 165篇 |
1995年 | 148篇 |
1994年 | 131篇 |
1993年 | 113篇 |
1992年 | 116篇 |
1991年 | 87篇 |
1990年 | 62篇 |
1989年 | 58篇 |
1988年 | 24篇 |
1987年 | 21篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 2篇 |
1962年 | 3篇 |
1961年 | 2篇 |
1959年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
12.
目的 以气调包装酱卤鸭肉制品为研究对象,在冷链温度范围内建立一套准确、高效的货架期预测模型。方法 利用选择性培养基测定不同温度下产品各微生物数量,确定4~25℃条件下产品优势腐败菌。对乳酸菌数量与感官评定值进行了回归分析确定最小腐败量Ns。分别采用修正的Gompertz方程和平方根方程建立一、二级模型,并通过预测值与实测值对比验证模型的可靠性。结果 确定了4~25℃条件下产品优势腐败菌为乳酸菌,最小腐败量Ns=6.14(lg(cfu /g))。一、二级模型拟合度均良好,三种温度下模型预测值与实际值间的差异均在30%左右,波动幅度在10%以内。结论 实现了对4~25℃内任何时间点产品剩余货架期的预测,为冷链条件下气调包装酱卤鸭肉制品品质的变化提供了理论指导。 相似文献
13.
The Chinese Remainder Theorem (CRT) explains how to estimate an integer-valued number from the knowledge of the remainders obtained by dividing such unknown integer by co-prime integers. As an algebraic theorem, CRT is the basis for several techniques concerning data processing. For instance, considering a single-tone signal whose frequency value is above the sampling rate, the respective peak in the DFT informs the impinging frequency value modulo the sampling rate. CRT is nevertheless sensitive to errors in the remainders, and many efforts have been developed in order to improve its robustness. In this paper, we propose a technique to estimate real-valued numbers by means of CRT, employing for this goal a Kroenecker based M-Estimation (ME), specially suitable for CRT systems with low number of remainders. Since ME schemes are in general computationally expensive, we propose a mapping vector obtained via Kroenecker products which considerably reduces the computational complexity. Furthermore, our proposed technique enhances the probability of estimating an unknown number accurately even when the errors in the remainders surpass 1/4 of the greatest common divisor of all moduli. We also provide a version of the mapping vectors based on tensorial n-mode products, delivering in the end the same information of the original method. Our approach outperforms the state-of-the-art CRT methods not only in terms of percentage of successful estimations but also in terms of smaller average error. 相似文献
14.
The aim of this study is to investigate the synergistic effects of modified TiO2/multifunctionalized graphene oxide nanosheets at different ratios on the interface compatibility between starch and poly(lactic acid) (PLA). To this end, silanylated nano-TiO2 (MTiO2, 1 and 2%) and alkylated maleic anhydride grafted graphene oxide (f-GO, 0.1, 0.2, and 0.4%) at different combinations are blended with the PLA-starch composites using solution blending technique. Then, the synergistic effects of MTiO2 and f-GO on PLA/starch matrix are investigated in terms of the morphology, crystallinity, structural characterization, thermal stability, dynamic mechanical, and antiaging properties, and the related mechanisms. The Raman and Fourier transform infrared spectroscopy spectra verify the successful synthesis of the two modified nanofillers (f-GO and MTiO2) and the formation of strong hydrogen bond within the PLA-starch nanocomposites. Due to the strong interfacial interaction and the synergistic effect from the combination of 1% MTiO2 and 0.2% f-GO, obvious improvement was observed in PLA-starch versus other nanocomposites in terms of morphology, thermal stability, surface hydrophobicity, storage modulus, ultraviolet-shielding capacity, and aging-resistance. Furthermore, differential scanning calorimeter (DSC), isothermal crystallization kinetic, and X-ray diffraction analysis demonstrate that f-GO and the M-TiO2 significantly synergize in enhancing the crystallization rate and crystallinity of PLA/starch matrix. These results provide novel insights for constructing high-performance nanocomposites and facilitate their applications in food packaging. 相似文献
15.
Katharina M. A. Kaiser 《应用聚合物科学杂志》2020,137(40):49230
Plastic-based multilayer packaging has an important function on the packaging market, but is currently not recyclable as the polymer layers used are usually thermodynamically immiscible. This work therefore follows the approach to prepare separable multilayer packaging using a packaging adhesive modified with thermally unstable adducts, and proposes a corresponding recycling process. For this purpose, typical multilayer structures (polyethylene (PE)// polyethylene terephtalate (PET), PET//aluminum, and PE//aluminum) were prepared by curing furan-/maleimide-functionalized polyurethane (PU)-prepolymers with a three-functional cross-linking agent. Adhesions of up to over 3N per 15 mm test specimen were measured or substrate failures of PET films were observed. However, heating in dimethylsulfoxide, the retro-Diels–Alder reaction takes place and the cross-linked adhesive turns thermoplastic and dissolves in the solvent. Thus, the laminate separates and the pure PE, PET, and aluminum foils can be recovered without any PU residue. 相似文献
16.
Evaluation of the effect of processing on cocoa polyphenols: antiradical activity,anthocyanins and procyanidins profiling from raw beans to chocolate 下载免费PDF全文
Matteo Bordiga Monica Locatelli Fabiano Travaglia Jean Daniel Coïsson Giuseppe Mazza Marco Arlorio 《International Journal of Food Science & Technology》2015,50(3):840-848
The content and composition of anthocyanins and procyanidins in fermented cocoa beans (from different geographic origins: Ecuador, Cameroon, Ivory Coast, Ghana and Nigeria), roasted nibs, cocoa mass and chocolate were determined, beside the determination of the total antiradical capacity. Concerning geographic origin, cocoa beans and processed products from Ecuador showed the highest levels of anthocyanins, followed by Nigeria and Cameroon. Generally, as cocoa beans were further processed, the levels of anthocyanins and flavan‐3‐ols decreased. The largest observed losses of phenolics occurred during roasting. A progressive decreasing trend in polyphenol concentration was observed in the other processed samples as well. Despite the original content of polyphenols in raw cocoa beans, technological processes imply a significant impact on cocoa quality, confirming the need of specific optimisation to obtain high value chocolate. 相似文献
17.
18.
纳米纤维素作为一种性能优越的可再生纳米材料,应用前景极为广阔。然而,由于纳米纤维素结构上富含羟基,使其具有极强的亲水性,严重影响了纳米纤维素的疏水性能,并且在一定程度上限制了其在复合材料领域的应用。综述了纳米纤维素疏水改性的研究进展,从物理吸附、表面化学修饰(甲硅烷化、烷酰化、酯化等)、聚合物接枝共聚3个方面简述了目前应用较为广泛的疏水化改性方法,并对疏水纳米纤维素在包装材料、造纸、水净化等方面的应用现状进行了总结。最后对疏水改性纳米纤维素的未来发展进行了展望,旨在为疏水纳米纤维素的研究和应用提供参考。 相似文献
19.
20.