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71.
72.
Zn2+-protease activity of botulinum neurotoxin causes the blockage of neurotransmitter release resulting in botulism disease. We have investigated the role of Zn2+ in the biological activity of type A botulinum neurotoxin by removing the bound Zn2+ by EDTA treatment, followed by monitoring its structure in terms of secondary and tertiary folding (second derivative UV, FT-IR, and circular dichroism spectroscopy) and function in terms of its effect on the release of norepinephrine from PC12 cells. The single Zn2+ bound to each neurotoxin molecule was reversibly removed by EDTA treatment, whereas the biological activity of the neurotoxin was irreversibly lost. Based on the Amide III IR spectral analysis, the alpha-helical content of neurotoxin increased from 29% to 42% upon removal of Zn2+, which reverted to 31% upon treatment with 1:5 molar excess of exogenous Zn2+. Second derivative UV spectroscopy revealed no change in surface topography of Tyr residues with removal of Zn2+. However, near-UV circular dichroism signals suggested significant alterations in the topography of Phe and Tyr residues that could be buried in the protein matrix. Thermal unfolding experiments suggested that removal of Zn2+ results in the formation of the molten globule-like structure of type A botulinum neurotoxin. Tertiary structural changes introduced by Zn2+ removal were irreversible, which correlated well with the irreversibility of the biological activity of the neurotoxin. On the basis of these results, we suggest that Zn2+ plays a significant structural role in addition to its catalytic role in Zn2+-protease activity of type A botulinum neurotoxin. 相似文献
73.
JF Huntley HD Schallig FN Kooyman A Mackellar F Jackson WD Smith 《Canadian Metallurgical Quarterly》1998,20(11):565-571
A monoclonal antibody to ovine IgE was employed in an ELISA to investigate the IgE antibody responses in serum and gastric lymph to a primary infection of Teladorsagia circumcincta, and following challenge in previously infected sheep. During a primary response, IgE antibody to antigens derived from the infective third stage (L3) and adult (L5) worms were negligible, with low levels of IgE antibody detected in serum and lymph. In contrast, there was a pronounced IgE antibody response in 2/4 sheep to L3 antigens during 2-8 days after challenge of previously infected animals but low levels of IgE antibody to L5 antigens. This response was confirmed in a second but similar experiment, where relatively high levels of IgE antibody was detected to antigens from L3. Antibody levels were higher in lymph than in serum from the same animals, and Western blots of L3 antigen following SDS-PAGE under reducing conditions revealed several bands of MW26-96KD which reacted with the IgE antibody from gastric lymph. Immunohistochemical staining indicated that these IgE antibodies may be reacting with allergens associated with the surface cuticle of the worms. 相似文献
74.
75.
A. L. Fielding J. Mayers 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2002,480(2-3):680-689
The electron Volt Spectrometer (eVS) is an inverse geometry filter difference spectrometer that has been optimised to measure the single atom properties of condensed matter systems using a technique known as Neutron Compton Scattering (NCS) or Deep Inelastic Neutron Scattering (DINS). The spectrometer utilises the high flux of epithermal neutrons that are produced by the ISIS neutron spallation source enabling the direct measurement of atomic momentum distributions and ground state kinetic energies. In this paper the procedure that is used to calibrate the spectrometer is described. This includes details of the method used to determine detector positions and neutron flight path lengths as well as the determination of the instrument resolution. Examples of measurements on 3 different samples are shown, ZrH2, 4He and Sn which show the self-consistency of the calibration procedure. 相似文献
76.
77.
EC Edi-Osagie RE Hopkins V Ogbo F Lockhat-Clegg M Ayeko WO Akpala FN Mayers 《Canadian Metallurgical Quarterly》1998,105(10):1070-1078
OBJECTIVE: To compare the influence on caesarean section morbidity of uterine exteriorisation or in situ repair. DESIGN: Randomised controlled trial. SETTING: Princess Anne Maternity Unit of the Royal Bolton Hospital, UK. POPULATION: One hundred and ninety-four women undergoing delivery by caesarean section. METHODS: Two intra-operative readings of arterial pulse rate, mean arterial blood pressure, and arterial haemoglobin oxygen saturation were obtained. Pre-operative and day-3 haemoglobin concentrations were determined. Intra- and post-operative complications, puerperal pain scores, and febrile and infectious morbidity were assessed. A postal questionnaire was used to assess morbidity six weeks after delivery. MAIN OUTCOME MEASURES: Intra-operative changes in pulse rate, mean arterial blood pressure and oxygen saturation; peri-operative changes in haemoglobin concentration; incidence of intraoperative vomiting, pain, intra- and post-operative complications, and febrile and infectious morbidity; immediate and late puerperal pain scores; satisfaction with the operation. RESULTS: No clinically significant differences between uterine exteriorisation and in situ repair were found in pulse rate, mean arterial pressure, oxygen saturation and haemoglobin changes. Likewise, the incidence of vomiting and pain was similar. Vomiting occurred in 10% of all the women, and 57% of all pain complaints occurred at the initial skin incision. There was a trend towards higher immediate and late pain scores in the exteriorisation group, reaching statistical significance on day 3. Overall, pain scores averaged 6/10 on day 1 despite patient-controlled analgesia, and three-quarters of all women reported persisting pain on day 42. Intra- and post-operative complications, febrile and infectious morbidity, and duration of hospital stay were similar in both groups. CONCLUSIONS: We have demonstrated that uterine exteriorisation and in situ repair have similar effects on peri-operative caesarean section morbidity. Intra-operative pain reflected adequacy of anaesthesia, while vomiting reflected adequacy of pre-operative preparation of patients. Exteriorising the uterus at caesarean section is a valid option. 相似文献
78.
BACKGROUND: Fluoroquinolones are one of the most widely used treatments for gonorrhoeae. Changes in the susceptibility of Neisseria gonorrhoeae to these agents may threaten their use. GOAL OF THIS STUDY: To report several resistant strains (>1 mcg/ml) isolated in the western United States and to evaluate the prevalence of strains with reduced susceptibility (ofloxacin 0.25 mcg/ml, ciprofloxacin 0.06 mcg/ml). STUDY DESIGN: The microbiology and epidemiology of three resistant strains were characterized and 12,761 other strains were evaluated for fluoroquinolone susceptibility as part of the Gonococcal Isolate Surveillance Project of the Centers for Disease Control and Prevention. RESULTS: Fluoroquinolone-resistant strains may appear sporadically. The prevalence of isolates with reduced susceptibility to fluoroquinolones remains low in the Southwest region of the United States. CONCLUSIONS: Continued active surveillance is needed to detect and control the spread of quinolone-resistant Neisseria gonorrhoeae. 相似文献
79.
Superior vena cava syndrome developed in a patient in whom an endocardial transvenous pacemaker had been inserted five years previously. Venography demonstrated an obstructing lesion at the junction of the superior vena cava and right atrium. Balloon catheter dilatation failed to afford any relief from her progressive symptoms. Exploration of the area revealed a benign fibrotic lesion encircling the pacemaker lead within the right atrium. Excision of the lesion, removal of the lead, and patching the right atrium with pericardium resulted in rapid cure. 相似文献
80.
FN Ghadially CJ Lock SE Yang-Steppuhn JM Lalonde 《Canadian Metallurgical Quarterly》1981,13(2):223-230
Cells in culture were exposed to cis-dichlorodiammineplatinum (II) and platinum-uracil blue. No platinum could be demonstrated in an intracellular location morphologically or by electron-probe x-ray analysis in the case of the former compound. However, platinum was readily demonstrated in phagosomes or phagolysosomes after exposure of cells to platinum-uracil blue. 相似文献