全文获取类型
收费全文 | 1430篇 |
免费 | 31篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 15篇 |
综合类 | 1篇 |
化学工业 | 358篇 |
金属工艺 | 50篇 |
机械仪表 | 62篇 |
建筑科学 | 16篇 |
能源动力 | 80篇 |
轻工业 | 121篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 141篇 |
一般工业技术 | 341篇 |
冶金工业 | 105篇 |
原子能技术 | 11篇 |
自动化技术 | 150篇 |
出版年
2023年 | 23篇 |
2022年 | 24篇 |
2021年 | 45篇 |
2020年 | 29篇 |
2019年 | 29篇 |
2018年 | 38篇 |
2017年 | 37篇 |
2016年 | 46篇 |
2015年 | 20篇 |
2014年 | 49篇 |
2013年 | 88篇 |
2012年 | 55篇 |
2011年 | 91篇 |
2010年 | 70篇 |
2009年 | 70篇 |
2008年 | 77篇 |
2007年 | 58篇 |
2006年 | 39篇 |
2005年 | 35篇 |
2004年 | 43篇 |
2003年 | 27篇 |
2002年 | 43篇 |
2001年 | 32篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 37篇 |
1997年 | 38篇 |
1996年 | 36篇 |
1995年 | 24篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 20篇 |
1991年 | 15篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 3篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1971年 | 4篇 |
排序方式: 共有1465条查询结果,搜索用时 15 毫秒
1.
Ramesh Shruthy Stephen Jancy Radhakrishnan Preetha 《International Journal of Food Science & Technology》2021,56(8):3991-3999
In this study, the cellulose nanoparticles (CNP) isolated from potato peel were used for reinforcement of polyvinyl alcohol (PVA)-based active packaging film. The above film was used to pack the raw prawns (Penaeus monodon) at −20 °C, and the colour change, protein content, TVB-N, TMA and microbial analysis were done at regular interval for prawns stored in CNP-PVA active packaging film. A significant difference was observed in the quality of prawns stored in potato CNP-PVA film compared with prawns packed and stored in polyethylene film. The newly designed active packaging with CNP and fennel seed oil enhanced the shelf life of prawns up to two months for both HOSO (head on shell on) prawn and PD (peeled and deveined) prawn. Hence, the study recommends the potato peel CNP-PVA film with fennel seed oil as better choice to extend the shelf life of the prawns during storage compared with polyethylene packaging. 相似文献
2.
Ponnusamy Nandha Kumar Shangavi Subramanian Uthirapathy Vijayalakshmi Sanjeevi Kannan 《Journal of the American Ceramic Society》2020,103(6):3528-3540
Structurally stable β-Ca3(PO4)2/t-ZrO2 composite mixtures with the aid of Dy3+ stabilizer were accomplished at 1500°C. The precursors comprising Ca2+, P5+, Zr4+, and Dy3+ have been varied to obtain five different combinations. The results revealed the fact that complete phase transformation of calcium-deficient apatite to β-Ca3(PO4)2 occurred only at 1300°C, whereas the evidence of t-ZrO2 crystallization is obvious at 900°C. The dual occupancy of Dy3+ at β-Ca3(PO4)2 and t-ZrO2 structures was evident; however, Dy3+ initially prefers to occupy β-Ca3(PO4)2 lattice until its saturation limit and thereafter accommodates at the lattice site of ZrO2. The typical absorption and emission behavior of Dy3+ were noticed in all the systems and, moreover, the surrounding symmetry of Dy3+ domains has been determined from the luminescence study. All the systems ensured paramagnetic response that is generally contributed by the presence of Dy3+. A gradual increment in the phase content of t-ZrO2 in the composite mixtures ensured a significant improvement in the hardness and Young's modulus of the investigated compositions. 相似文献
3.
Locke Davenport Huyer Serena Mandla Yufeng Wang Scott B. Campbell Bess Yee Christian Euler Benjamin F. Lai A. Dawn Bannerman Dawn S. Y. Lin Miles Montgomery Kayla Nemr Timothy Bender Slava Epelman Radhakrishnan Mahadevan Milica Radisic 《Advanced functional materials》2021,31(6):2003341
Itaconate (ITA) is an emerging powerhouse of innate immunity with therapeutic potential that is limited in its ability to be administered in a soluble form. A library of polyester materials that incorporate ITA into polymer backbones resulting in materials with inherent immunoregulatory behavior is developed. Harnessing hydrolytic degradation release from polyester backbones, ITA polymers result in the mechanism specific immunoregulatory properties on macrophage polarization in vitro. In a functional assay, the polymer-released ITA inhibits bacterial growth on acetate. Translation to an in vivo model of biomaterial associated inflammation, intraperitoneal injection of ITA polymers demonstrate a rapid resolution of inflammation in comparison to a control polymer silicone, demonstrating the value of sustained biomimetic presentation of ITA. 相似文献
4.
Summary Novel PUs containing pyridinium moieties were synthesized by chain extending isocyanate endcapped prepolymers with N, N’-bis (2-hydroxyethyl) isonicotinamide. The pyridinium moieties in the PUs were chemically crosslinked using short-chain divalent quaternising agents. The polyurethane cationomers were characterized by spectral, thermal and mechanical analysis. Spectral results confirmed the quaternisation of tertiary nitrogen leading to crosslinking. Compared to conventional PUs, the crosslinked PU networks exhibited improved thermal stability. The damping value (i.e.) tan δ for cationomers were improved over a broad temperature range when compared to conventional PU. 相似文献
5.
In this paper, we present a method for blind separation of co-channel BPSK signals arriving at an antenna array. This method consists of two parts: the maximum likelihood constellation estimation and assignment. We show that at high SNR, the maximum likelihood constellation estimation is well approximated by the smallest distance clustering algorithm, which we proposed earlier on heuristic grounds. We observe that both these methods for estimating the constellation vectors perform very well at high SNR and nearly attain Cramer-Rao bounds. Using this fact and noting that the assignment algorithm causes negligible error at high SNR, we derive upper bounds on the probability of bit error for the above method at high SNR. These upper bounds fall very rapidly with increasing SNR, showing that our constellation estimation-assignment approach is very efficient. Simulation results are given to demonstrate the usefulness of the bounds 相似文献
6.
M. D. Kannan Sa. K. Narayandass C. Balasubramanian D. Mangalaraj 《Journal of Materials Science》1992,27(18):5040-5044
Aluminium-neodymium oxide-aluminium thin film capacitors have been prepared by thermal evaporation and the d.c. conduction properties of these films have been studied. The thicknesses of the films have been determined by a multiple beam interferometer. The current-voltage power-law dependence showed that the conduction in these films is space-charge limited. The linear dependence of the current density on the square root of the applied field confirmed the exponential trap distribution. The trap density has been found to be of the order of 1026 m–3. It has also been observed that the Schottky type of conduction is predominant in the high-field region and the height of the Schottky barrier has been determined. It is seen that the conduction mechanism is an activated process with the activation energy decreasing with increasing field. 相似文献
7.
T. S. Radhakrishnan 《应用聚合物科学杂志》2006,99(5):2679-2686
Thermal degradation of poly(dimethylsilylene) homopolymer (PDMS) and poly(tetramethyldisilylene‐co‐styrene) copolymer (PTMDSS) was investigated by pyrolysis‐gas chromatography and thermogravimetry (TG). PDMS decomposes by depolymerization, producing linear and cyclic oligomeric products, whereas PTMDSS decomposes by random degradation along the chain resulting in each monomeric product and various other combination products. The homopolymer was found to be much less stable than the copolymer. The decomposition mechanisms leading to the formation of various products are shown. The kinetic parameters of thermal degradation were evaluated by different integral methods using TG data. The activation energies of decomposition (E) for the homopolymer and the copolymer are found to be 122 and 181 kJ/mol, respectively, and the corresponding values of order of reaction are 1 and 1.5. The observed difference in the thermal stability and the values of the kinetic parameters for decomposition of these polymers are explained in relation with the mechanism of decomposition. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006 相似文献
8.
A family of energy/economic/environmental (E3) models is presented as a mechanism for analysing national policy issues. The family consists of discrete models which are designed to be run in an integrated manner. The outputs of certain models provide the inputs to the next. This structure allows the analyst to readily incorporate an understanding of regional factors such as local energy prices, concerns over air quality, water availability, or attitudes towards construction of new energy facilities, into national assessments of energy policies. This paper reviews the analytic framework within which energy policy issues are currently addressed. The initial family of E3 models is described with the emphasis on the data linkages and feedback which are provided when these models are run sequentially. The ongoing MITRE research programme with the E3 family of models is presented and plans and opportunities for future work are outlined. 相似文献
9.
A new finite element crack growth algorithm has been developed to simulate dynamic fracture. In this algorithm, pseudo elements with very high initial density are placed below the crack plane and the density is reduced to zero in a gradual manner as the crack passes the element. A number of linear elastic and elasto-viscoplastic problems have been carried out to test the new algorithm. The results are compared with some of the existing crack growth models. 相似文献
10.
A nonlinear SOR-type algorithm is established to find the intersection of a finite number of closed convex sets in a Hilbert space. 相似文献