全文获取类型
收费全文 | 6496篇 |
免费 | 2篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 14篇 |
建筑科学 | 2篇 |
轻工业 | 4篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 5篇 |
一般工业技术 | 3篇 |
冶金工业 | 6457篇 |
自动化技术 | 9篇 |
出版年
2023年 | 1篇 |
2019年 | 2篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2010年 | 1篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2003年 | 9篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 158篇 |
1998年 | 1921篇 |
1997年 | 1133篇 |
1996年 | 755篇 |
1995年 | 388篇 |
1994年 | 344篇 |
1993年 | 386篇 |
1992年 | 49篇 |
1991年 | 101篇 |
1990年 | 104篇 |
1989年 | 89篇 |
1988年 | 101篇 |
1987年 | 87篇 |
1986年 | 76篇 |
1985年 | 59篇 |
1983年 | 12篇 |
1982年 | 32篇 |
1981年 | 47篇 |
1980年 | 57篇 |
1978年 | 26篇 |
1977年 | 180篇 |
1976年 | 350篇 |
1975年 | 10篇 |
1955年 | 4篇 |
1954年 | 3篇 |
排序方式: 共有6498条查询结果,搜索用时 13 毫秒
31.
The anaphylactic shock of the rabbit is characterized by an acute right ventricular overload, accompanied by severe alterations of cardiac electrogenesis. During shock, the mean QRS vector, as measured from the algebraic sum of the Q, R, and S deflections on the three leads, shifts to the right, inferiorly and anteriorly. An injury current quickly appears. The TQ vector points away from the right ventricle. A progressive depolarization on the right ventricular wall is displayed by suction electrodes and the suppression of right ventricular hypertension by a cross circulation produces an almost immediate disappearance of the injury current. The geneses of these electrical alterations are briefly discussed. The possibility of an anaphylactic reaction at the level of the coronary arterial wall, previously mentioned in the literature, seems unlikely. The role of the haemodynamic changes and of the increased right ventricular blood pool is thought to be predominant. 相似文献
32.
The sulfated material which locates in the basal membrane of ciliary body epithelium when immature rat eyes are incubated with Na235SO4 was studied. On the basis of its chromatographic behavior compared with standard preparations, we conclude that the material consists of sulfatides. 相似文献
33.
A comparison of the quantity and the quality of pollen content in the atmosphere of two regions, one of the plains bordering the Mediterranean sea (altitude 40 m), the other of the mountains of the Pyrenees (altitude 1550 m), was made during the climatological year 1974-1975. The method which was used intercepts the pollen flux of the atmosphere with a vertical filtering unit, which is exposed facing the direction of wind on the filtering door of the weather-vane and collects much larger quantities of pollen than the other techniques of collection. The atmospheric currents displace from one region to another numerous spores and pollens, the trajectories of which are directly influenced by the general circulation of the atmosphere. The density of these fluxes can be very large, reaching 2500 grains/m3 of air at M.T.P.R. in the last week of January; the taxons collected are very numerous (more than 700). The atmospheric transfer of pollen modifies largely the pollen content of the atmosphere of different flowering domains. These interferences manifest themselves in the simplest cases by the presence of two peaks of concentration, the principal corresponding to the local efflorescence, the second to the pollen transferred from other regions. The pollen concentrations in the mountains are one-third of those in the plains. Pollination in the mountains is several weeks late in comparison to the plain during the first semester, whereas during the second semester, it is the plains that show a certain delay. These findings show why some allergic patients who go to the mountains during summer are affected twice by pollination. 相似文献
34.
Nanosecond-pulse fluorimetry of wheat germ agglutinin is analyzed as a function of both excitation and emission wavelengths. When excited at 280 nm, wheat germ agglutinin fluorescence exhibited three lifetimes: one corresponding to the tyrosine residues as a whole and two others corresponding to the tryptophyl emission. The tyrosine contribution to the emission spectrum deduced from this method was in good agreement with that reported previously in steady-state fluorescence experiments [Privat, J.P. and Monsigny, M. (1975) Eur. J. Biochem. 60, 555-567]. The fluorescence decay of each tryptophan residue was not a single exponential function when wheat germ agglutinin was excited at 295 nm. This could be related to the microenvironment of the indole chromophores in the protein. The comparison of the quantum yield and of average lifetime showed that some tryptophan residues were completely quenched. Energy transfer from tyrosines to tryptophan residues previously detected in steady-state fluorescence was also revealed by fluorescence decay measurements. Comparison of both methods showed that an important part of transfers occurred with a very fast rate equal to or greater than 10(10) s-1. Both lifetimes and the ratio of the short and the long-lived component were found dependent on tri-N-acetylchitotriose binding. 相似文献
35.
Two triglyceride lipases in postheparin plasma, the lipoprotein lipase (LPL) and the hepatic triglyceride lipase (H-TGL) were separated by heparin-sepharose affinity chromatography and studied in controls and patients during the course of acute hepatitis. All three patients had increased content of triglycerides in the low density lipoproteins, and two of them had hypertriglyceridemia. Low activities of both lipases were found in the acute stage of the disease in all three patients. Concomitantly one of the patients had absolute low lecithin: cholesterol acyltransferase (LCAT) activity, and in the two other patients a relative LCAT deficiency was present. The increased content of triglycerides in LDL that may be found in liver disease, may not only be due to low H-TGL and LPL, but also LCAT deficiency. 相似文献
36.
JP Derenne J Couture S Iscoe A Whitelaw J Milic-Emili 《Canadian Metallurgical Quarterly》1976,40(5):805-814
The effect of general anesthesia on control of breathing was studied by CO2 rebreathing and occlusion pressure measurements in six normal human subjects under methoxyflurane anesthesia. CO2 was found to increase the amplitude of the occlusion pressure wave without changing its shape, so that CO2 responses in terms of the occlusion pressure developed 100 ms after the onset of inspiration (Po/0.1) gave results equivalent to the responses in terms of Po/1.o or any other parameter of the pressure wave. Methoxyflurane depressed the ventilatory response to CO2 but not the occlusion pressure response, implying that the most important action of the anesthetic was to increase the effective elastance of the respiratory system rather than to depress the respiratory centers. The elastance was further increased by CO2, and this mechanical change had the effect of shifting the "apneic threshold" extrapolated from the ventilatory response curve to a lower PAco2. Frequency of breathing, inspiratory and expiratory times were not altered by CO2 in anesthetized subjects. 相似文献
37.
38.
39.
DW Seccombe P Dodek J Frohlich P Hahn JP Skala DJ Campbell 《Canadian Metallurgical Quarterly》1976,22(10):1589-1592
Because of renewed interest in a possible connection between carnitine, lipid disorders, and myopathy, an automated method of analysis is desirable. Deproteinization of serum by use of membrane filter cones and automated assay with a bichromatic analyzer (the ABA-100) substantially increases efficiency without sacrificing the specificity and accuracy of the original manual enzymatic method. The described procedure allows for analysis of 80 speciments a day and is thus suitable for screening of selected populations. Normal values found in blood sera of adults were in the range of 25.0-73.8 mu mol/liter and the method has sufficient sensitivity to accurately measure concentrations as small as 10 mu mol/liter. 相似文献
40.
JP Radó 《Canadian Metallurgical Quarterly》1976,67(3):322-330
Carbamazepine (CA)-induced antidiuresis and fluorescence in urinary cortisol assay was compared during short-term and prolonged treatment in 3 patients with pituitary diabetes insipidus. The fluorescence induced by excreted CA-metabolite(s) (probably CA-10-11 epoxide and its derivatives) was used for the rough clinical estimation of the rate of metabolic elimination of the drug. A marked decrease was observed both in the antidiuretic response induced by CA and excretion of CA metabolite(s) during prolonged treatment - with a fixed dose of CA. These findings suggest that diminishing antidiuretic effectiveness might be due to auto-induction of CA. Auto-induction of CA may explain the delay in improvement of renal concentrating operation in patients with DI during long-term treatment with fixed doses of CA. Another clinical consequence of this mechanism may be the prevention of the development of water intoxication in neuro-psychiatric patients undergoing chronic treatment with CA. 相似文献