全文获取类型
收费全文 | 1166篇 |
免费 | 8篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 20篇 |
机械仪表 | 4篇 |
建筑科学 | 2篇 |
矿业工程 | 1篇 |
能源动力 | 3篇 |
轻工业 | 17篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 16篇 |
一般工业技术 | 20篇 |
冶金工业 | 1065篇 |
自动化技术 | 17篇 |
出版年
2022年 | 1篇 |
2021年 | 6篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 11篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 10篇 |
2010年 | 1篇 |
2009年 | 4篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 12篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 31篇 |
1998年 | 348篇 |
1997年 | 187篇 |
1996年 | 126篇 |
1995年 | 58篇 |
1994年 | 47篇 |
1993年 | 65篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 17篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 12篇 |
1978年 | 2篇 |
1977年 | 25篇 |
1976年 | 72篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有1174条查询结果,搜索用时 15 毫秒
81.
T Genzini A de Oliveira e Silva MP de Miranda CR de Melo RJ Felipe TE dos Santos ES Cardoso CF Costa-Filho RG Haetinger EC Pereira 《Canadian Metallurgical Quarterly》1995,32(4):162-167
Hemangiomas are the most common benign vascular tumor found in the liver. In this study, 103 cases of hepatic hemangiomas were analysed in a retrospective manner. Image aspects such as those seen in ultrassonography, computed tomography, nuclear magnetic resonance and arteriography are discussed. The incidence was higher amongst the female sex, between individuals from 40 to 60 years old, which presented predominantly without symptoms (66%) and localized mainly in the right hepatic lobe (74%). The meaning of those aspects, when adopted, permits the clinicians to differentiate benign from malignant nodular lesions in the liver. 相似文献
82.
To engineer an a non-islet cell capable of glucose-stimulated insulin secretion, a chinese hamster ovary cell line (CHO) was transfected with a mammalian expression vector carrying the human insulin cDNA (pCB/hINS). More proinsulin than insulin was released daily by the stably transformed cell line (CHO-INS). Examination of acid-ethanol extracts confirmed that both insulin and proinsulin were stored. Immunohistochemical analysis of the cells also showed that (pro)insulin was stored. Unlike beta cells, CHO-INS cells did not secrete insulin in response to glucose. To investigate this lack of effect, we examined whether transfection of GLUT2 cDNA, which is ordinarily not expressed in CHO-INS cells, would confer glucose-stimulated insulin secretion. Consequently, we have demonstrated that glucose regulated insulin release occurs in the CHO-INS-GLUT2 cell line and that glucose potentiates the insulin secretory response to non-glucose secretagogues. 相似文献
83.
Monolithic columns for capillary electrochromatography have been prepared within the confines of untreated fused-silica capillaries in a single step by a simple copolymerization of mixtures of butyl methacrylate, ethylene dimethacrylate, and 2-acrylamido-2-methyl-1-propane-sulfonic acid (AMPS) in the presence of a porogenic solvent. The use of these novel macroporous monoliths eliminates the need for frits, the difficulties encountered with packed capillaries, and capillary surface functionalization. Since the porous properties of the monolithic materials can be easily tailored through changes in the composition of the ternary porogenic solvent, the effects of both pore size and the percentage of sulfonic acid monomer on the efficiency and the electroosmotic flow velocity of the capillary columns could be studied independently over a broad range. A simple increase in the content of charged functionalities within the monolith leads to an expected acceleration of the flow velocity. However, increasing the pore size leads to a substantial deterioration of the efficiency of the separation. In contrast, monoliths with increasing levels of AMPS in which the pore size remains fixed due to adjustments in the composition of the porogenic solvent show no deterioration in efficiency while maintaining the same increase in flow velocity, thus producing a significant reduction in separation time. Additionally, measurements on monoliths with constant levels of AMPS but different pore sizes suggest that flow velocity may be affected by the flow resistance within the capillary column. 相似文献
84.
MS Macieira EA Silva WG Almeida EM Nakamura-Palacios EC Vasquez 《Canadian Metallurgical Quarterly》1997,68(3):149-154
Metaphor comprehension was studied in schizophrenics as compared to psychiatric and nonpsychiatric controls. Subjects were asked in a two-condition forced-choice response task to detect the metaphor similar or contrary to a proverb with an abstract meaning. Schizophrenic patients were impaired in both conditions. However, the paranoid patients' performances did not differ from psychiatric and nonpsychiatric controls. These results are consistent with the hypothesis that the ability of metaphorizing is preserved in some schizophrenic patients. 相似文献
85.
P. Ruben Mercado 《Computational Economics》2004,23(4):303-313
This article analyzes the trade-off between `caution' and `intensity' in the use of the control variable in a one-state one-control dynamic stochastic quadratic linear optimization problem with discount factor. It studies the effects that changes in uncertainty of the control parameter have on the optimal first period response of the control variable, showing that the trade-off between `caution' and `intensity' depends on the timing of the uncertainty. Given an increase in current uncertainty and an equal increase in future uncertainty, caution will always prevail over intensity. Moreover, the prevalence of caution will be enlarged as the increase in future uncertainty moves farther away into the future, while this prevalence will be reduced as the increase in future uncertainty expands into the future. Finally, for the infinite horizon case, caution is the optimal policy response. 相似文献
86.
PURPOSE: To determine medical students' experiences in working with diabetic patients, their cognitive competence and their confidence in meeting diabetic patients' educational needs, and changes in their expertise with advancing education. METHOD: The study was conducted in March 1994 at the University of Illinois College of Medicine, where students work with ambulatory patients in a longitudinal primary care experience from their second year through graduation. A combined questionnaire and objective quiz was developed and distributed to 138 second-, third-, and fourth-year students. The students were asked whether they had had experience in seeing a newly diagnosed diabetic patient, in what setting, and whether they felt confident in educating such patients on various common topics. They were also asked about their interests in and preferences for learning about diabetic patients' education. A 50-item objective quiz on the management of diabetes followed the questionnaire. Data were analyzed with several statistical methods. RESULTS: In all, 65 of the students (47%) responded; the majority were third- or fourth-year students. The percentages of students who felt confident ranged from 83% who felt confident about counseling about exercise to only 16% who felt confident about pre-conception counseling. All of the students but one felt that diabetic patients' education was an important topic, and all but two were interested in it. The students' quiz scores showed no significant difference by year of training; for all the students the average score was 39.6% correct, with no increase in score for increased training. Also, the students who were more confident about their abilities to provide patient education on a certain topic were no more likely to have accurate information about that topic than were those who were not confident. CONCLUSION: Although they were clearly interested in diabetic patients' education, the students did not feel confident in providing it, nor did they have the cognitive competence to do so. Medical schools have a responsibility to students and to their patients to formally address the issues of patient education. 相似文献
87.
A Spinetti A Margutti S Bertolini F Bernardi G BiFulco EC degli Uberti F Petraglia AR Genazzani 《Canadian Metallurgical Quarterly》1997,137(6):664-669
OBJECTIVE: Menopause is associated with critical changes in the cardiovascular system, and the possible effect of hormonal replacement therapy (HRT) on these changes is under investigation. The aim of our study was to evaluate in postmenopausal women the effects of HRT and clonidine on the response of plasma calcitonin gene-related peptide (CGRP) and plasma atrial natriuretic peptide (ANP) to the upright posture test and the saline infusion test respectively. METHODS: CGRP and ANP levels were measured with specific radioimmunological assays and expressed in pmol/l (means +/- S.E.M). DESIGN: Postmenopausal women (age 46-53 years) (n = 18) were studied before and after 3 months of HRT (n = 13) or clonidine treatment (n = 5). RESULTS: After HRT or clonidine treatment plasma CGRP levels (14.9 +/- 1.6 and 15.9 +/- 3.8 pmol/l) were significantly higher than before (9.8 +/- 0.6 and 10.5 +/- 1.6 pmol/l) (P < 0.01). The assumption of upright posture caused no change in plasma CGRP levels before treatment, while after HRT, but not after clonidine treatment, an increase in plasma CGRP levels was observed (P < 0.01 at 5 and 20 min). Basal plasma ANP levels significantly decreased after both HRT and clonidine treatment (P < 0.01). In untreated women the saline infusion test did not induce any change in plasma ANP levels; a significant response to the test was restored after HRT but not after clonidine treatment (P < 0.01 at 90 and 120 min). CONCLUSIONS: The results show that some of the adaptive responses modified by menopausal changes are restored by HRT but not clonidine treatment, suggesting a modulatory role for sex steroid hormones in cardiovascular function and salt and water balance. 相似文献
88.
89.
90.
EC Hatchikian N Forget A Bernadac D Alazard B Ollivier 《Canadian Metallurgical Quarterly》1995,146(2):129-141
Various sulphate-reducing bacteria differing in the number of genes encoding hydrogenase were shown to ferment lactate in coculture with Methanospirillum hungatei, in the absence of sulphate. The efficiency of interspecies H2 transfer carried out by these species of sulphate-reducing bacteria does not appear to correlate with the distribution of genes coding for hydrogenase. Desulfovibrio vulgaris Groningen, which possesses only the gene for [NiFe] hydrogenase, oxidizes hydrogen in the presence of sulphate and produces some hydrogen during fermentation of pyruvate without electron acceptor. The hydrogenase of D. vulgaris was purified and characterized. It exhibits a molecular mass of 87 kDa and is composed of two different subunits (60 and 28 kDa). D. vulgaris hydrogenase contains 10.6 iron atoms, 0.9 nickel atom and 12 acid-labile sulphur atoms/molecule, and the absorption spectrum of the enzyme is characteristic of an iron-sulphur protein. Maximal H2 uptake and H2 evolution activities were 332 and 230 units/mg protein, respectively. D. vulgaris cells contain exclusively the [NiFe] hydrogenase, whatever the growth conditions, as shown by biochemical and immunological studies. Immunocytolocalization in ultrathin frozen sections of cells grown on lactate and sulphate, on H2 and sulphate and on pyruvate showed that the [NiFe] hydrogenase was located in the periplasmic space. Labelling was enhanced in cells grown on H2 and sulphate and on pyruvate. The results enable us to conclude that D. vulgaris Groningen contains a single hydrogenase of the [NiFe] type, located in the periplasmic space like that described for D. gigas. This enzyme appears to be involved in both H2 uptake and H2 production, depending on the growth conditions. 相似文献