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51.
BD Cohen JF Bowley PJ Sheridan 《Canadian Metallurgical Quarterly》1997,18(2):158, 160, 162-158, 160, 164
Three postgraduate prosthodontic students served as clinicians/evaluators in a study rating their preferences for three different diamond cutting instruments from three manufacturers. Each evaluator prepared the axial walls of complete veneer crowns on extracted molar teeth and then ranked their preference of the instruments. To prepare nine teeth, each of the three instruments was used in random order and without knowledge of the specific manufacturer. The methodology for analyzing the evaluators' preferences and the results are discussed. 相似文献
52.
Effects of TCDD on Ah receptor, ARNT, EGF, and TGF-alpha expression in embryonic mouse urinary tract
Lipoprotein(a) [Lp(a)] biogenesis was examined in primary cultures of hepatocytes isolated from mice transgenic for both human apolipoprotein(a) [apo(a)] and human apoB. Steady-state and pulse-chase labeling experiments demonstrated that newly synthesized human apo(a) had a prolonged residence time (approximately 60 min) in the endoplasmic reticulum (ER) before maturation and secretion. Apo(a) was inefficiently secreted by the hepatocytes and a large portion of the protein was retained and degraded intracellularly. Apo(a) exhibited a prolonged and complex folding pathway in the ER, which included incorporation of apo(a) into high molecular weight, disulfide-linked aggregates. These folding characteristics could account for long ER residence time and inefficient secretion of apo(a). Mature apo(a) bound via its kringle domains to the hepatocyte cell surface before appearing in the culture medium. Apo(a) could be released from the cell surface by apoB-containing lipoproteins. These studies are consistent with a model in which the efficiency of post-translational processing of apo(a) strongly influences human plasma Lp(a) levels, and suggest that cell surface assembly may be one pathway of human Lp(a) production in vivo. Transgenic mouse hepatocytes thus provide a valuable model system with which to study factors regulating human Lp(a) biogenesis. 相似文献
53.
Cultured Chinese hamster ovary cells were exposed to 2.25-MHz ultrasound in sterile 4.5-mL polyethylene chambers and tested for cell lysis, sonoporation and DNA transfection. Ten percent of Albunex, a gas-body-based ultrasound contrast agent, was added to ensure cavitation nucleation, and the chambers were rotated at 60 rpm to promote cavitation activity during the 1-min exposures. Uptake of large fluorescent dextran molecules by some cells was observed for spatial peak pressure amplitudes as low as 0.1 MPa, which indicates transient permeabilization and resealing, i.e., sonoporation, of these cells during exposure. Significant lysis occurred for 0.2 MPa, and increased rapidly for exposures above the apparent cavitation threshold (using the H2O2 production test) of about 0.4 MPa spatial peak pressure amplitude. In the DNA transfection tests, 20 micrograms/mL luciferase reporter plasmid was added to the suspension during exposure, and cells were assayed for proliferation ability and luciferase gene expression 2 days after exposure. Cell proliferation was greatly reduced above the cavitation threshold. Luciferase production was significant for 0.20-MPa exposure, and reached 0.33 ng per 10(6) cells at 0.8-MPa exposure. The luciferase production was great for cells exposed in medium supplemented with serum than for cells exposed in serum-free medium. Cells harvested for exposure either in the log phase or in the stationary phase of culture gave similar proliferation and transfection results. The effects essentially disappeared when the Albunex was omitted from the suspension and the tube was not rotated. Thus, sonoporation by ultrasonic cavitation in the rotating tube system yields plasmid transfection with subsequent transient gene expression. 相似文献
54.
H Chao ME Houston RS Hodges CM Kay BD Sykes MC Loewen PL Davies FD S?nnichsen 《Canadian Metallurgical Quarterly》1997,36(48):14652-14660
The most abundant isoform (HPLC-6) of type I antifreeze protein (AFP1) in winter flounder is a 37-amino-acid-long, alanine-rich, alpha-helical peptide, containing four Thr spaced 11 amino acids apart. It is generally assumed that HPLC-6 binds ice through a hydrogen-bonding match between the Thr and neighboring Asx residues to oxygens atoms on the {2021} plane of the ice lattice. The result is a lowering of the nonequilibrium freezing point below the melting point (thermal hysteresis). HPLC-6, and two variants in which the central two Thr were replaced with either Ser or Val, were synthesized. The Ser variant was virtually inactive, while only a minor loss of activity was observed in the Val variant. CD, ultracentrifugation, and NMR studies indicated no significant structural changes or aggregation of the variants compared to HPLC-6. These results call into question the role of hydrogen bonds and suggest a much more significant role for entropic effects and van der Waals interactions in binding AFP to ice. 相似文献
55.
V Kerekatte BD Keiper C Badorff A Cai KU Knowlton RE Rhoads 《Canadian Metallurgical Quarterly》1999,73(1):709-717
Infection of cells by picornaviruses of the rhinovirus, aphthovirus, and enterovirus groups results in the shutoff of host protein synthesis but allows viral protein synthesis to proceed. Although considerable evidence suggests that this shutoff is mediated by the cleavage of eukaryotic translation initiation factor eIF4G by sequence-specific viral proteases (2A protease in the case of coxsackievirus), several experimental observations are at variance with this view. Thus, the cleavage of other cellular proteins could contribute to the shutoff of host protein synthesis and stimulation of viral protein synthesis. Recent evidence indicates that the highly conserved 70-kDa cytoplasmic poly(A)-binding protein (PABP) participates directly in translation initiation. We have now found that PABP is also proteolytically cleaved during coxsackievirus infection of HeLa cells. The cleavage of PABP correlated better over time with the host translational shutoff and onset of viral protein synthesis than did the cleavage of eIF4G. In vitro experiments with purified rabbit PABP and recombinant human PABP as well as in vivo experiments with Xenopus oocytes and recombinant Xenopus PABP demonstrate that the cleavage is catalyzed by 2A protease directly. N- and C-terminal sequencing indicates that cleavage occurs uniquely in human PABP at 482VANTSTQTM downward arrowGPRPAAAAAA500, separating the four N-terminal RNA recognition motifs (80%) from the C-terminal homodimerization domain (20%). The N-terminal cleavage product of PABP is less efficient than full-length PABP in restoring translation to a PABP-dependent rabbit reticulocyte lysate translation system. These results suggest that the cleavage of PABP may be another mechanism by which picornaviruses alter the rate and spectrum of protein synthesis. 相似文献
56.
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58.
BD Spiess MH Wall BS Gillies JC Fitch LO Soltow WL Chandler 《Canadian Metallurgical Quarterly》1997,78(2):820-826
Thromboelastography (TEG) has been used after cardiopulmonary bypass (CPB) to diagnose excessive postoperative hemorrhage. Conventional TEG during CPB is not possible due to the sensitivity of the TEG to even small amounts of heparin, which produces a nondiagnostic tracing. The purpose of this study was to compare heparin neutralization using heparinase or protamine in TEG blood samples obtained during CPB. TEG testing was performed on 48 patients before, during and after CPB. Tissue plasminogen activator activity and antigen were measured on a subset of 32 patients. We found: 1) heparinase neutralized at least 10 IU/ml heparin while 1.6 ug/ml protamine neutralized up to 7 IU/ml heparin, 2) in samples with complete heparin neutralization by both methods, there was no significant difference in the R values, 3) while there was good correlation for other TEG parameters between heparinase and protamine treated samples, heparinase treatment produced shorter K values and higher angle, MA and A60, 4) while fibrinolysis was detected using both methods, heparinase treatment suppressed fibrinolysis in the TEG in both samples from patients and after in vitro addition of tissue plasminogen activator, 5) TEG was not a sensitive indicator of t-PA activity, detecting only 21% of samples with increased t-PA activity during bypass, and 5) heparinase was at least 100 times more expensive than protamine. We conclude that while both heparinase and protamine can be used to neutralize heparin in TEG samples obtained during CPB, protamine neutralization is more sensitive to fibrinolysis and less expensive, but the protamine dose must be carefully selected to match the heparin level used at individual institutions. 相似文献
59.
This is the first report showing VIP fibers in the optic chiasm and the optic nerves of intact rats. These fibers form a fan-shaped dorso-medial bundle in the optic nerves. After colchicine injection into the vitreous body VIP fibers could be followed farther in the optic nerve toward the eye when compared to intact rats. After removal of eyes (enucleation) the VIP fiber-bundle became more prominent and VIP immunoreactive perikarya appeared in the supraoptic and para ventricular nuclei. When five-nine months after the enucleation Phaseolus vulgaris leucoagglutinin was administered to the paraventricular or supraoptic area, the anterogradely transported tracer was demonstrated in the optic nerve. These observations suggest the existence of a hypothalamic projection to the eye, which is, at least in part, VIP immunoreactive. 相似文献