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KS Tsai 《Canadian Metallurgical Quarterly》1997,96(10):802-805
Taiwanese people have spinal bone mineral density (BMD) values similar to those of Caucasians, whereas their hip BMD values are 10% to 15% lower. In 1992, the prevalence of vertebral fractures, diagnosed according to the -3 SD morphometric criteria, was 18% for women and 12% for men older than 65 years in the major cities of Taiwan. Despite this high prevalence of vertebral fractures, the incidence of hip fractures in the elderly of both sexes was only 203 per 100,000 in 1996, which was lower than in Caucasians and similar to that in mainland Chinese. Hip and vertebral fractures are both associated with lower BMD values. The risk factors for low BMD in Taiwan include a lighter body weight and aging in both sexes, and menopause for women. An increased bone turnover rate is associated with a lower BMD in both men and postmenopausal women, although the rate seems to increase in women but decrease in men with aging. In Taipei City, daily calcium intake is relatively low (mean intake +/- SD; 640 +/- 240 mg), but the vitamin D stores seem to be generally adequate for middle-aged and elderly women. There was a significant association between a higher daily calcium intake and a higher BMD/lower bone turnover rate for women in this age group. Vitamin D receptor allelic polymorphism was not an important factor in low BMD and rapid bone turnover. 相似文献
175.
DT Chua JS Sham DL Kwong KS Tai PM Wu M Lo A Yung D Choy L Leong 《Canadian Metallurgical Quarterly》1997,39(3):711-719
PURPOSE: To investigate the variability of tumor volume in nasopharyngeal carcinoma using quantitative measurements of tumor bulk derived from computed tomography, and to study the prognostic value of tumor volume in comparison with other variables. METHODS AND MATERIALS: Two hundred ninety patients with newly diagnosed nasopharyngeal carcinoma were included in the study. The primary tumor volume (PTV) and nodal tumor volume (NTV) were obtained by outlining the tumor contour followed by summation of areas in sequential pretreatment computed tomography axial scans. Total tumor volume (TTV) was obtained by adding the PTV and NTV. All patients had radiotherapy as the primary treatment, 67 patients also received cisplatin-based neoadjuvant chemotheraphy. RESULTS: A large variation in tumor volume was observed, especially in advanced stage disease. The median PTV (cc) in Ho's T1, T2, and T3 disease were: 6.9 (range: 0.9-42.7), 18.8 (1.6-127.9), and 52.4 (3.3-166.8). The median TTV (cc) in Ho's stage I to IV disease were: 7.6 (range: 1.3-42.7), 19.8 (3.2-55.7), 40.7 (4.1-222.7), and 51.1 (3.1-274.7). Patients with a large PTV (>60 cc) were associated with significantly poorer local control (5-year local control rate: 56%) and disease-specific survival (5-year survival rate: 53%). In patients with a small PTV (< or =20 cc), there were no significant differences in local control among different T stages. Large NTV (>30 cc) was associated with significantly higher distant failure rate (5-year distant relapse-free survival rate: 54%) and lower disease-specific survival (5-year survival rate: 40%). In multivariate analysis, only PTV was found to be an independent factor in predicting local control. CONCLUSION: A large variation of tumor volume was present in different T stage disease of nasopharyngeal carcinoma, and PTV represents an independent prognostic factor of local control that appears to be more predictive than Ho's T stage classification. 相似文献
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KS McNaught PA Carrupt C Altomare S Cellamare A Carotti B Testa P Jenner CD Marsden 《Canadian Metallurgical Quarterly》1998,56(8):921-933
The cause of neurodegeneration in Parkinson's disease (PD) remains unknown. However, isoquinoline derivatives structurally related to the selective dopaminergic toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its active metabolite, 1-methyl-4-phenylpyridinim (MPP+), have emerged as candidate endogenous neurotoxins causing nigral cell death in Parkinson's disease. Isoquinoline derivatives are widely distributed in the environment, being present in many plants and foodstuffs, and readily cross the blood-brain barrier. These compounds occur naturally in human brain where they are synthesized by non-enzymatic condensation of biogenic amines (e.g. catecholamines and phenylethylamine) with aldehydes, and are metabolized by cytochrome P450s and N-methyltransferases. In addition, isoquinoline derivatives are oxidized by monoamine oxidases to produce isoquinolinium cations with the concomitant generation of reactive oxygen species. Neutral and quaternary isoquinoline derivatives accumulate in dopaminergic nerve terminals via the dopamine re-uptake system, for which they have moderate to poor affinity as substrates. Several isoquinoline derivatives are selective and more potent inhibitors of NADH ubiquinone reductase (complex I) and alpha-ketoglutarate dehydrogenase activity in mitochondrial fragments than MPP+, and lipophilicity appears to be important for complex I inhibition by isoquinoline derivatives. However, compared with MPP+, isoquinoline derivatives are selective but less potent inhibitors of NADH-linked respiration in intact mitochondria, and this appears to be a consequence of their rate-limiting ability to cross mitochondrial membranes. Although both active and passive processes are involved in the accumulation of isoquinoline derivatives in mitochondria, inhibition of respiration is determined by steric rather than electrostatic properties. Compared with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine or MPP+, isoquinoline derivatives show selective but relatively weak toxicity to dopamine-containing cells in culture and following systemic or intracerebral administration to experimental animals, which appears to be a consequence of poor sequestration of isoquinoline derivatives by mitochondria and by dopamine-containing neurones. In conclusion, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-like cytotoxic characteristics of isoquinoline derivatives and the endogenous/environmental presence of these compounds make it conceivable that high concentrations of and/or prolonged exposure to isoquinoline derivatives might cause neurodegeneration and Parkinson's disease in humans. 相似文献
177.
KS Yarnall BK Rimer D Hynes G Watson PR Lyna CT Woods-Powell J Terrenoire LT Barber 《Canadian Metallurgical Quarterly》1998,11(2):96-104
One hundred eleven (58%) of 191 adolescent inpatients previously admitted to the emergency wards at the Child and Adolescent Psychiatric Clinics in the cities of Uppsala and G?teborg participated in a 2-4 year follow-up evaluation. The prevalence, incidence, and stability of depressive symptoms, suicidal ideation, and suicide attempts among the adolescents, and predictors of follow-up functioning were examined. Although a majority of the patients substantially reduced their depressive symptoms over the 2-4 year period, a smaller group (13%), mainly girls (94%), continued reporting high symptom levels at follow-up, and one out of five adolescents had moderate-severe levels of suicidal ideation. The accumulated frequency of suicide attempts among the patients shortly prior to hospitalization and during the follow-up was 59% including two patients who committed suicide. Significant predictors of depressive symptom severity at follow-up were depressive symptom scores and V-diagnoses at inpatient assessment. Previous suicide attempts before hospitalization, high levels of self-reported depressive symptoms and nonintact family status at inpatient assessment predicted suicide attempts during the follow-up period. The high prevalence of attempted and completed suicide in this clinical group underscores the importance of developing effective treatments for suicidal adolescents. 相似文献
178.
Protein splicing of the Saccharomyces cerevisiae vacuolar membrane ATPase intein involves four highly coordinated reactions that result in precise cleavage and formation of peptide bonds. In this study, we investigated the roles of the last N-extein residue (-1 residue) and the intein penultimate residue in modulating splicing reactions. Most of the 20 amino acid substitutions at the -1 position had no effect on overall protein splicing but could lead to significant accumulation of thioester intermediates when splicing was blocked by mutation. A subset of -1 substitutions attenuated the initiation of protein splicing and enabled us to demonstrate in vitro splicing of a mesophilic intein containing all wild-type catalytic residues. Substitutions involving the intein penultimate residue allowed modulation of the branch resolution and C-terminal cleavage reaction. Our data suggest that the N-S acyl rearrangement, which initiates splicing, may also serve as the rate-limiting step. Through appropriate amino acid substitutions, we were able to modulate splicing reactions in vitro by change in pH or temperature or addition of thiol reagents. Both insertion and deletion were tolerated in the central region of the intein although splicing or structure of the intein may have been affected. 相似文献
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180.
A study was conducted to investigate the reduction and elimination of Escherichia coli O157:H7 by the effects of gamma irradiation and ozone treatment. Log phase cells were found to be more sensitive to gamma irradiation than stationary phase cells. E. coli O157:H7 was found to be considerably more resistant to irradiation at -18 degrees C than at 20 degrees C. The D values for this organism for treatment with ozone in tryptic soy agar were higher than those for treatment with ozone in phosphate buffer. Gamma irradiation at a dose of 1.5 kGy or ozone treatment at a concentration of 3 to 18 ppm for 20 to 50 min was required to assure the elimination of E. coli O157:H7. 相似文献