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81.
Anuradee Witthayapanyanon Tri Thanh Phan Todd C. Heitmann Jeffrey H. Harwell David A. Sabatini 《Journal of surfactants and detergents》2010,13(2):127-134
Extended surfactants containing an intermediate-polarity spacer, such as polypropylene oxide, in between the hydrophilic head and the hydrocarbon tail are known to result in superior solubilization and low interfacial tension, though they exhibit slow kinetics. The present work seeks to evaluate both equilibrium and kinetic aspects of extended-surfactant-based micro- and macroemulsions. The interfacial morphology of the extended surfactant membrane, i.e., characteristic length (ξ) and interfacial rigidity (E r) at optimum middle-phase microemulsion conditions, was characterized using the net-average curvature model. The results showed that extended surfactants resulted in a relatively rigid interfacial membrane compared with conventional surfactants having similar hydrocarbon chain length. In addition, both ξ and E r parameters increased with the length of the polypropylene oxide spacer. Increasing E r values correlated to the slow coalescence rates of extended surfactant emulsified systems. Two alternative approaches (the addition of combined linkers and co-surfactant) are shown to overcome the slow kinetics of coalescence while maintaining desirable high solubilization and low interfacial tension. 相似文献
82.
Anubhav Sarmah Raymond D. Mee Kailash Arole David Chi Ethan M. Harkin Smita Shivraj Dasari Aniela J. K. Wright Thang Q. Tran Ankush Rout Micah J. Green 《大分子材料与工程》2023,308(11):2300174
This work shows that radio-frequency (RF) fields can simultaneously align carbon nanotubes (CNTs) dispersed in a resin and induce Joule heating to cure the resin. The timescales of alignment and curing using RF heating are numerically computed and compared at different field strengths in order to determine a temperature where alignment happens before the matrix crosslinks. Composites are experimentally fabricated at the desired target temperature and are optically analyzed and quantified; the CNT network is successfully aligned in the direction of the applied electric field. This methodology can be used to create composites where the local alignment can be varied across the sample. Composites fabricated using RF fields have higher electrical conductivity in the direction of the aligned CNTs than an oven-cured, randomly aligned sample. Also, RF-cured nanocomposites exhibit higher tensile strength and modulus in the direction of alignment compared to an oven-cured sample. Finally, it is further demonstrated how this methodology can be coupled with a direct ink writing additive manufacturing process to induce alignment in any desired direction, even orthogonal to the shear forces in the extrusion direction. 相似文献
83.
形状记忆合金材料的一个重要特征就是在固体状时,在一定温度或载荷下会发生相变过程。因此在摩擦过程中,当法向载荷够大时,局部发生的相变将导致接触点材料力学性质改变,从而使摩擦性能改变。在单点接触的Hertz模型的基础上,建立以钢球接触Ni-Ti记忆合金平面的接触模型,通过分析法向载荷诱发塑性变形的过程,探讨法向载荷对Ni Ti形状记忆合金(Shape memory alloy,SMA)摩擦过程的影响,并与实验结果进行比较。理论分析和实验研究结果均表明:当法向载荷小时,摩擦因数与法向载荷成负相关;当法向载荷超过一定值后,摩擦因数几乎不变。所得出的结论可以用来预测形状记忆合金的摩擦性能,以控制和减少零件可能因磨损造成的损失。 相似文献
84.
Effect of Extended Surfactant Structure on Interfacial Tension and Microemulsion Formation with Triglycerides 总被引:1,自引:0,他引:1
T. T. Phan C. Attaphong D. A. Sabatini 《Journal of the American Oil Chemists' Society》2011,88(8):1223-1228
In this work, the impacts of extended surfactant structure (number of polypropylene oxide PO groups and branching nature of
the hydrocarbon chain) on microemulsion formation and IFT values were examined with triglyceride oils. The results show that
branching of the hydrocarbon tail of extended surfactants lowers optimum salinity and IFT values. The results also show that
for the surfactants studied ultralow IFTs and microemulsion formation with vegetable oils can be achieved using extended surfactants
with at least eight PO groups. 相似文献
85.
Raphael C.-W. Phan Jiang Wu Khaled Ouafi Douglas R. Stinson 《Wireless Personal Communications》2011,61(1):69-81
In this paper, we analyze the first known provably secure Radio Frequency Identification (RFID) authentication schemes that
are designed to provide forward untraceability and backward untraceability: the L-K and S-M schemes. We show how to trace
tags in the L-K scheme without needing to corrupt tags. We also show that if a standard cryptographic pseudorandom bit generator (PRBG) is used in the S-M scheme, then the scheme may fail to provide forward untraceability
and backward untraceability. To achieve the desired untraceability features, we show that the S-M scheme can use a robust PRBG which provides forward security and backward security. We also note that the backward security is stronger than necessary
for the backward untraceability of the S-M scheme. 相似文献
86.
87.
Finding a large set of single DNA strands that do not crosshybridize to themselves and/or to their complements is an important
problem in DNA computing, self-assembly, and DNA memories. We describe a theoretical framework to analyze this problem, gauge
its computational difficulty, and provide nearly optimal solutions. In this framework, codeword design is reduced to finding large sets of strands maximaly separated in a DNA space and the size of such sets depends on the geometry
of these metric spaces. We show that codeword design is NP-complete using any single reasonable measure that approximates the Gibbs energy, thus practically excluding the possibility
of finding any procedure to find maximal sets efficiently. Second, we extend a technique known as shuffling to provide a construction
that yields provably nearly-maximal codes. Third, we propose a filtering process that removes strands creating pairs with
low Gibbs energies, as approximated by the nearest-neighbor model. These two steps produce large codes of thermodynamic high
quality. The proposed framework can be used to gain an understanding of the Gibbs energy landscapes for DNA strands on which
much of DNA computing and self-assembly are based. 相似文献
88.
H Kino H Inaba N Van De L Van Chau DT Son HT Hao ND Toan LD Cong M Sano 《Canadian Metallurgical Quarterly》1998,29(2):250-254
We present the spatial structure of binase, a small extracellular ribonuclease, derived from 1H-NMR* data in aqueous solution. The total of 20 structures were obtained via torsion angle dynamics using DYANA program with experimental NOE and hydrogen bond distance constraints and phi and chi1 dihedral angle constraints. The final structures were energy minimised with ECEPP/2 potential in FANTOM program. Binase consists of three alpha-helices in N-terminal part (residues 6-16, 26-32 and 41-44), five-stranded antiparallel beta-sheet in C-terminal part (residues 51-55, 70-75, 86-90, 94-99 and 104-108) and two-stranded parallel beta-sheet (residues 22-24 and 49-51). Three loops (residues 36-39, 56-67 and 76-83), which play significant role in biological functioning of binase, are flexible in solution. The differences between binase and barnase spatial structures in solution explain the differences in thermostability of binase, barnase and their hybrids. 相似文献
89.
T. Masood S. Patterson N.V. Amarasinghe S. McWilliams D. Phan D. Lee Z.A. Hilali Xiong Zhang G.A. Evans J.K. Butler 《Photonics Technology Letters, IEEE》2004,16(3):726-728
Single-frequency 1310-nm grating-outcoupled surface-emitting (GSE) semiconductor lasers with output slope efficiencies exceeding 0.1 mW/mA into multimode fibers, threshold currents below 22 mA, and >30-dB sidemode suppression ratios are reported. These GSE lasers consist of 500-/spl mu/m-long active ridges that excite one end of surface-emitting second-order outcoupling gratings with 200-/spl mu/m-long first-order distributed Bragg reflector gratings terminating the laser cavities at both ends. The grating outcouplers range from 10 to 50 /spl mu/m in length. These lasers have an open eye pattern for nonreturn-to-zero signals at 2.5 Gb/s into single-mode fibers. The full-width half-maximum far-field beam divergences range from 1.5/spl deg/ /spl times/ 8/spl deg/ to 5/spl deg/ /spl times/ 8/spl deg/. 相似文献
90.
溶胀动力学方法测定高分子链结构 总被引:2,自引:0,他引:2
本文成功地用溶胀动力学方法测定了交联、线型及支化高分子的溶胀特征曲线,并认为可由这种溶动力学探针技术判别高分子链的结构类型及特征,是一个很有特色的研究方法。 相似文献