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71.
Michelle Feeney Maria Antonietta Casadei Pietro Matricardi 《Journal of materials science. Materials in medicine》2009,20(5):1081-1087
A carboxymethyl derivative of scleroglucan (Scl-CM) with a derivatization degree of 65 ± 5% was synthesized. The rheological
behaviour of this novel polymer was studied and compared with that of the starting polymer. We observed that the charged moieties
carried on the chains could prevent the triple helix formation of Scl. Scl-CM aqueous solutions behave like true polymer solutions
up to 1% w/v, whereas above this concentration a weak gel behaviour was observed. CaCl2 addition to aqueous Scl-CM solutions led to a physical gel formation; the hydrogel strength was related to polymer and CaCl2 concentrations. Temperature sweeps, registered at 1 Hz on hydrogels differing in CaCl2 concentration, evidenced a gel → sol transition in the range of 30–40°C, depending on the molar ratio between carboxylic
groups and Ca+2. In order to verify a possible use of these hydrogels as drug delivery systems, acyclovir was loaded into the network. Rheological
analysis evidenced that the loaded drug can affect the hydrogel elastic modulus. The release of acyclovir in phosphate buffer
was evaluated at different temperatures in order to assess the suitability of this novel drug delivery system in topical applications. 相似文献
72.
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74.
Contact conductivity detection in poly(methyl methacrylate)-based microfluidic devices for analysis of mono- and polyanionic molecules 总被引:1,自引:0,他引:1
Galloway M Stryjewski W Henry A Ford SM Llopis S McCarley RL Soper SA 《Analytical chemistry》2002,74(10):2407-2415
An on-column contact conductivity detector was developed for the analysis of various mono- and polyanionic compounds separated by electrophoresis chips fabricated in poly(methyl methacrylate) (PMMA) using hot embossing techniques from Ni electroforms. The detector consisted of a pair of Pt wires (127 microm diameter) with an end-to-end spacing of approximately 20 microm and situated within the fluidic channel. The waveform applied to the electrode pair was a bipolar pulse with a frequency of 5.0 kHz and was used to reduce the charging current from measurement so that the current recorded at the end of one pulse is more representative of the solution conductivity. Using the detector, separations of amino acids, peptides, proteins, and oligonucleotides were demonstrated. For the amino acids and peptides, free-solution zone electrophoresis was performed. A calibration plot for the amino acid alanine was found to be linear from approximately 10 to 100 nM in a carrier electrolyte consisting of 10 mM triethylamonium acetate. The concentration detection limit was found to be 8.0 nM, with the corresponding mass detection limit equal to 3.4 amol (injection volume = 425 pL). The protein separations with conductivity detection were performed using MEKC, in which the carrier electrolyte contained the anionic surfactant sodium dodecyl sulfate (SDS) above its cmc. Near baseline resolution was achieved in the PMMA microchip for a solution containing 8 different proteins. In the case of the DNA fragments, capillary electrochromatography was used with a C18-modified PMMA chip and a carrier electrolyte containing an ion-pairing agent. 相似文献
75.
Fals-Stewart William; Birchler Gary R.; Kelley Michelle L. 《Canadian Metallurgical Quarterly》2006,74(3):579
Married or cohabiting female alcoholic patients (n = 138) and their non-substance-abusing male partners were randomly assigned to 1 of 3 equally intensive interventions: (a) behavioral couples therapy plus individual-based treatment (BCT; n = 46), (b) individual-based treatment only (IBT; n = 46), or (c) psychoeducational attention control treatment (PACT; n = 46). During treatment, participants in BCT showed significantly greater improvement in dyadic adjustment than those in IBT or PACT; drinking frequency was not significantly different among participants in the different conditions. During the 1-year posttreatment follow-up, compared with participants who received IBT or PACT, participants who received BCT reported (a) fewer days of drinking, (b) fewer drinking-related negative consequences, (c) higher dyadic adjustment, and (d) reduced partner violence. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
The authors used a predictable, externally cued task-switching paradigm to investigate executive control in a severe closed-head injury (CHI) population. Eighteen individuals with severe CHI and 18 controls switched between classifying whether a digit was odd or even and whether a letter was a consonant or vowel on every 4th trial. The target stimuli appeared in a circle divided into 8 equivalent parts. Presentation of the stimuli rotated clockwise. Participants performed the switching task at both a short (200 ms) and a long (1,000 ms) preparatory interval. Although the participants with CHI exhibited slower response times and greater switch costs, similar to controls, additional preparatory time reduced the switch costs, and the switch costs were limited to the 1st trial in the run. These findings indicate that participants with severe CHI were able to take advantage of time to prepare for the task switch, and the executive control processes involved in the switch costs were completed before the 1st trial of the run ended. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
77.
Michelle Schatzman 《Journal of scientific computing》2002,17(1-4):99-116
We review some methods for high precision time integration: it is not easy to ensure stability, precision and numerical efficiency at the same time. Operator splitting—when it works—can be a good way to satisfy all these constraints; in some cases, the order of the splitting schemes can be enhanced by extrapolation; nevertheless, the applicability of splitting is limited due to non commutativity. As an alternative to splitting, we introduce preconditioned Runge–Kutta (PRK) schemes: the preconditioning is included in the scheme, instead of being put aside for implementation. Examples of PRK schemes are given including the extrapolation of the residual smoothing scheme, and sufficient conditions for stability are described. 相似文献
78.
We consider discrete mechanical systems subject to perfect unilateral constraints. Moreau's impact law uses the decomposition of the velocity on the normaland tangent cones to the set of admissible positions at the impact point, and it iswell-known that this gives the only possible rule in the case of a singleperfect unilateral constraint. In the multi-constraint case, there areother possible energetically and geometrically consistant impact laws. Weshow here that in a number of cases, the limiting behavior of impact asits rigidity tends to infinity is given by Moreau's rule, i.e., in a more mathematical language, we justify this impact law by a penalty approach.First we describe the penalty method, then we apply it to amulti-constraint model problem. We choose an overdamped approximationand we obtain Moreau's rule for inelastic shocks in the limit. Finally,we present the computational drawbacks of the penalty method. 相似文献
79.
The dietary intake of EFA and long-chain PUFA (LCPUFA) by women with (n=14) and without (n=31) gestational diabetes mellitus (GDM) was determined by repeated 24-h recalls. Women with GDM consumed significantly more
energy as fat compared with women who had uncomplicated pregnancies; absolute dietary fat did not differ. Dietary n−3 LCPUFA
was substantially lower than the current recommendation for pregnancy, whereas intake of saturated FA (SFA) exceeded it. We
conclude that replacing dietary sources of SFA with those of EFA and LCPUFA, especially n−3 LCPUFA, would benefit the dietary
fat profiles of all pregnant women. 相似文献
80.