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61.
ABSTRACT A data acquisition system has been developed for the analysis of the performance of an experimental reactor unit for coal gasification. Pertinent data such as gas concentrations, temperatures, and pressures at several locations inside the reactor, and the flow rate of supply gases are collected. An automated calibration procedure of the gas analysis system is included. A minicomputer controls the time sequences of the individual events, allowing a high degree of flexibility. The intervals between two gas analyses can be made as short as 30 sec, the other data can be taken arbitrarily often. The system is suitable for expansion to monitor more physical quantities and to increase the number of observation points inside the reactor. 相似文献
62.
The working principle of an optical isolator made of two corrugated dielectric gratings is introduced. One grating acts as a polarizer, and the other acts as a quarter-wave plate used in conical incidence converting linearly polarized light into circularly polarized light. Global maxima of diffraction efficiency for surface-corrugated gratings with binary, sinusoidal, and pyramidal ridge shapes with dependence on the material index are identified. Regarding technological feasibility for use in the visible wavelength range, high-frequency gratings with a binary shape were realized. With these gratings, an extinction ratio of more than 40 dB for the polarizer is theoretically possible, and more than 20 dB was experimentally achieved. A good correlation between theoretically calculated efficiencies and birefringences based on rigorous methods and the experimental results is demonstrated. 相似文献
63.
This paper deals with the explicit analysis of infinite periodic structures under arbitrary loadings. In the context or structural
stiffness optimization, with its inherent problem of multiple reanalysis, the purpose is to obtain expressions for the stress
resultants anywhere in the infinite structure as an explicit function of the stiffnesses of the elements. Following the method
of the representative cell the analysis of an infinite structures is reduced to the analysis of single module under transformed
loading and boundary conditions by using the discrete Fourier transform. This produces the equilibrium, strain-displacements
and constitutive equations in terms of complex-valued displacements, generalized strains and generalized stresses transforms.
Next an existing formula is used to write the stress resultants transforms explicitly in terms of the stiffnesses. Finally
one computes the stress resultants wherever needed in the real structure by means of the inverse Fourier transform. The exact
formula for the stress resultants is usually impractical due to the large number of terms involved in the analytical expressions.
What makes the approach practical herein is the very reduced size of the repeating module that is to be analysed, which renders
the analytical formula more tractable in many cases. The technique is illustrated with the explicit analysis of an infinite
truss with 1D translational symmetry and of an infinite grid of orthogonal beams on elastic supports with 2D translational
symmetry.
Received December 4, 2000 相似文献
64.
S.-L. Drechsler H. Rosner S.V. Shulga G. Fuchs H. von Lips J. Freudenberger M.S. Golden M. Knupfer K.-H. Müller L. Schultz J. Fink G. Kaindl H. Eschrig K. Koepernik 《Journal of Low Temperature Physics》1999,117(5-6):1617-1621
The electronic structure of tetragonal (RC(N))m(TB)2, m=1–3, compounds, with R= Y,Lu,La, T=Ni,Pt is studied. Total and partial densities of states N(E) are calculated and compared with orbital resolved x-ray absorption data. Special attention is paid to the structure of N(E) near the Fermi-level and its consequences for thermodynamic properties in the superconducting and the normal states. A medium el-ph coupling constant 0.5 1.2 is found. There is no simple correlation between N(0) and T
c
. The analysis of the upper critical field reveals the presence of at least two groups of electrons with quite different Fermi velocities v
F
in accord with dHvA data, and with calculated distributions of v
F
around the Fermi surface 相似文献
65.
DA Hullett MT Cantorna C Redaelli J Humpal-Winter CE Hayes HW Sollinger HF Deluca 《Canadian Metallurgical Quarterly》1998,66(7):824-828
BACKGROUND: 1,25-Dihydroxyvitamin D3, the hormonal form of vitamin D, is now believed to play a significant role in the immune responses, both in vitro and in vivo, preventing the development of several autoimmune diseases. These studies suggest that 1,25-dihydroxyvitamin D3 may be effective in prolonging allograph survival. METHODS: To test the hypothesis that 1,25-dihydroxyvitamin D3 would prolong allograft survival, neonatal heart grafts were transplanted to allogeneic recipients receiving either 19-nor-1,25-dihydroxyvitamin D2 (200 ng/day) or 1,25-dihydroxyvitamin D3 (50 ng/mouse/day) orally through the diet. The efficacy of 1,25-dihydroxyvitamin D3 in prolonging graft survival in a vascularized model was determined by heterotopic ACI to Lewis heart transplants. RESULTS: The provision of exogenous 1,25-dihydroxyvitamin D3 or an analog, 19-nor-1,25-dihydroxyvitamin D2, to mice markedly prolonged the survival of neonatal mouse heart allografts. Similar results were obtained with a vascularized heterotopic heart transplant model in rats. Cyclosporine at a maximum 25 mg/kg dose for mice proved less effective than 1,25-dihydroxyvitamin D3. Graft survival in mice differing at class I and class II loci (B10.A(4R) --> C57BL/10) increased from 13.0+/-1.1 days to 51.0+/-5.6 days and was significantly better than cyclosporine monotherapy (33.2+/-3.6). Rat heart survival in a high responder strain combination (ACI --> Lewis) increased from 6.2+/-0.3 to 25.2+/-2.8 days. The increased survival of the transplants brought about with 1,25-dihydroxyvitamin D3 was not accompanied by hypercalcemia in rats. CONCLUSION: These results suggest that 1,25-dihydroxyvitamin D3 can be used as an effective agent in preventing graft rejection. 相似文献
66.
DJ Kereiakes AM Lincoff DP Miller JE Tcheng CF Cabot KM Anderson HF Weisman RM Califf EJ Topol 《Canadian Metallurgical Quarterly》1998,97(9):857-864
BACKGROUND: Recent studies indicate that eradication of Helicobacter pylori might prevent peptic ulcer formation in patients treated with non-steroidal anti-inflammatory drugs (NSAIDs). On the other hand, gastric adaptation after repeated exposures to aspirin (ASA) is well documented but the influence of H. pylori on this process remains to be elucidated. AIM: To compare gastric damage and adaptation following repeated exposures to ASA in a group of patients with H. pylori infection, before and after eradication of the bacterium, and in H. pylori-negative controls. METHODS: Eight healthy volunteers without H. pylori infection and eight patients with duodenal ulcer (DU) history and H. pylori infection before and after H. pylori eradication were given ASA 2 g/day for a period of 14 days. Mucosal damage was evaluated by endoscopy and histology of biopsy samples. Gastric microbleeding, DNA synthesis in the gastric mucosa and mucosal expression, as well as luminal content of transforming growth factor-alpha (TGFalpha) were determined on days 0, 3, 7 and 14 of the ASA course. RESULTS: In all patients aspirin-induced gastric damage reached a maximum on day 3. In H. pylori-positive patients, this damage was maintained at a similar level up to day 14, whereas in H. pylori-negative controls and H. pylori-eradicated patients this damage significantly lessened on day 14 and was accompanied by elevated DNA synthesis as well as increased mucosal expression and luminal release of TGFalpha. 相似文献
67.
Although myelin basic protein (MBP)-recognizing T cells are not readily obtained after immunization of BALB/c mice with MBP (reflecting the BALB/c resistance to actively induced experimental autoimmune encephalomyelitis (EAE)), they can be expanded and cloned after several rounds of in vitro culture. The majority of BALB/c-derived clones recognize an epitope defined by MBP peptide 59-76. When transferred to naive BALB/c recipients, these clones cause classical EAE, with characteristic inflammation and demyelination of the central nervous system (CNS). We previously showed that two related clones recognizing a minor epitope, defined by MBP peptide 151-168, cause inflammation and demyelination preferentially of the peripheral nervous system (PNS). Because MBP has alternatively spliced isoforms, residues 151-168 are not present contiguously in all MBP isoforms. In order to determine whether induction of PNS disease is idiosyncratic to these sister clones, or related to their properties of epitope recognition, an independent T-cell line with similar recognition properties was studied. Clone 116F, derived from a BALB/c shiverer mouse, expresses a different T-cell receptor (TCR), with distinct TCR contact residues, but like the previously described T cells, this clone requires residues from both exons 6 and 7 for optimal stimulation. When adoptively transferred to BALB/c recipients, this clone preferentially induces disease of the PNS. A control BALB/c shiverer-derived MBP 59-76-recognizing clone, in contrast, induces CNS disease. These data strongly suggest that the site of disease initiation may correlate with epitope recognition, particularly when alternative isoforms are involved. 相似文献
68.
Gauss-Markov processes excited by nonstationary noises are encountered in the modeling of vibrating systems. We prove that the classical instrumental variable method, as well as the Ho-Kalman realization algorithm, for identifying the pole part (modal characteristics) of the model, are consistent when used on a single sample of the (nonstationary) signal. 相似文献
69.
SM Haslam GC Coles EA Munn TS Smith HF Smith HR Morris A Dell 《Canadian Metallurgical Quarterly》1996,271(48):30561-30570
Structural studies on the N-linked oligosaccharides of Haemonchus contortus, an economically important nematode that parasitizes domestic ruminants, have revealed core fucosylation of a type not previously observed in any eukaryotic glycoprotein. Mass spectrometric analyses were performed on detergent extracts of homogenized adult H. contortus and on purified H11, a glycoprotein isolated from intestinal brush borders which has been previously shown to be an effective vaccine antigen. The major N-linked glycans identified in the present study have up to three fucose residues attached to their chitobiose cores. The fucoses are found at the 3- and/or 6-positions of the proximal GlcNAc and at the 3-position of the distal GlcNAc. The latter substitution is unique in N-glycans. Most anti-H11 monoclonal antibodies are known to recognize carbohydrate epitopes, and it is possible that the newly discovered multifucosylated core structures are highly immunogenic in this glycoprotein. 相似文献
70.
O. Fuchs C. Friedrich G. Berg E. Broszeit A. Leyland A. Matthews 《Materialwissenschaft und Werkstofftechnik》1998,29(3):141-152
In this work the behaviour of hard coated light-metal components was investigated when they are mechanically loaded. Three lightmetal alloys, Ti-6Al-4V, AlSi7Mg and AlMgSi0.5 and 100Cr6 steel (as a reference material) were coated by two different physical vapour deposition processes: radio frequency magnetron sputtering and electron beam evaporation. The coating materials utilised were CrN and TiN. Standard test methods with different loading conditions were used to evaluate the substrate/coating-combinations: the hardness test (applying a static normal load), the scratch test (applying a combination of a static normal and a static tangential force) and the impact test (applying a dynamic normal load). It was observed that the load support of coated materials depends on the loading conditions. The coated aluminium alloys showed poor load support under all loading test conditions but produced a higher surface hardness than uncoated steel. Coated Ti-6Al-4V showed very good load support properties, similar to coated steel. All coated light-metal substrates demonstrated significant improvement in load support behaviour with an increase in coating thickness. The results of the scratch test, which is commonly used to asses adhesion properties of thin coatings, showed an immediate indenter-breakthrough on the aluminium alloy substrates, but causing no coating delamination. Due to this behaviour, the scratch test is not suitable to evaluate adhesion properties on coated soft light-metals. Yet the impact test allowed assessment of coating delamination on the aluminium alloys, proving its usefulness for adhesion measurement even on soft substrates. The study indicates that substitution of steel with coated lightmetal alloys is a viable proposition for certain applications. 相似文献