全文获取类型
收费全文 | 1267篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 4篇 |
金属工艺 | 1篇 |
机械仪表 | 5篇 |
建筑科学 | 2篇 |
能源动力 | 3篇 |
轻工业 | 16篇 |
无线电 | 1篇 |
一般工业技术 | 9篇 |
冶金工业 | 1229篇 |
原子能技术 | 1篇 |
自动化技术 | 2篇 |
出版年
2021年 | 2篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2006年 | 7篇 |
2004年 | 4篇 |
2003年 | 2篇 |
1999年 | 42篇 |
1998年 | 401篇 |
1997年 | 202篇 |
1996年 | 145篇 |
1995年 | 82篇 |
1994年 | 55篇 |
1993年 | 78篇 |
1992年 | 4篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 12篇 |
1988年 | 24篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 23篇 |
1976年 | 59篇 |
1975年 | 3篇 |
排序方式: 共有1273条查询结果,搜索用时 8 毫秒
91.
Serotonin (5-hydroxytryptamine, 5-HT) may play an important role in the pathogenesis of schizophrenia. Previous studies suggested that the efficacy of atypical neuroleptic drugs (e.g., risperidone and clozapine) on negative symptoms may be related to the 5-HT2a receptor. Although association studies between MspI polymorphism (T102C) and the 5-HT2a receptor gene and schizophrenia have been reported, their results are still controversial. The aim of this study was to examine the association between T102C polymorphism of the 5-HT2a receptor gene and schizophrenia as well as the association between the polymorphism and negative symptoms in a Japanese population (106 patients with schizophrenia and 109 healthy controls). No significant positive associations were observed. Our results suggest that the 5-HT2a receptor gene is not involved in the pathogenesis of schizophrenia or negative symptoms. 相似文献
92.
During an immune response, effector CD8+ T cells can kill infected cells by the perforin-dependent pathway. In comparison to CD4+ T cells, which are major sources of cytokines, normal CD8+ T cells produced less interleukin 2 and interferon gamma, and proliferated less vigorously after antigenic stimulation. Killing of target cells was a major cause of these reduced responses, since perforin-deficient CD8+ T cells showed substantially increased cytokine synthesis and proliferation. Cytotoxicity by the alternate Fas pathway also resulted in self-limitation of CD8+ T cell cytokine synthesis. This relationship between cytotoxicity and cytokine synthesis may regulate CD8+ T function in different phases of an immune response. 相似文献
93.
WA Paxton R Liu S Kang L Wu TR Gingeras NR Landau CR Mackay RA Koup 《Canadian Metallurgical Quarterly》1998,244(1):66-73
Escherichia coli leader peptidase, an integral membrane protein, is responsible for the cleavage of the signal sequence of many exported proteins. Recent studies suggest that it is a novel serine protease that utilizes a serine-lysine catalytic dyad. In an effort to further understand the mechanism of this enzyme, an internally quenched fluorescent peptide substrate incorporating the leader peptidase cleavage site of maltose binding protein signal peptide, Y(NO2)-F-S-A-S-A-L-A-K-I-K(Abz) (anthraniloyl), was designed and synthesized. In the intact peptide, the fluorescence of the anthraniloyl group is quenched by the 3-nitrotyrosine. This quenched fluorescence is liberated upon cleavage of the peptide by the leader peptidase, resulting in increased fluorescence that could then be monitored fluorometrically. The designed substrate can be cleaved effectively by E. coli leader peptidase as detected by both HPLC and fluorescent spectroscopy. Mass spectra of cleavage products demonstrated that the cleavage occurs at the predicted site (A-K). The cleavage of the peptide substrate has a linear dependence on the enzyme concentration (0.1 to 1.9 microM) and the kcat/K(m) was calculated to be 71.1 M-1 s-1. These data are comparable with the unmodified peptide substrate. This report represents the first direct continuous assay based on fluorescence resonance energy transfer for E. coli leader peptidase. 相似文献
94.
We report a patient diagnosed prenatally on routine fetal ultrasound, at 30 weeks' gestation, with subdural haemorrhage. The mother had suffered a mild abdominal trauma and had Factor XI deficiency; however, both were felt to be aetiologically insignificant. Prenatal follow-up showed a complete resolution of the haematoma and no postnatal sequelae have been noted to date. The aetiologies and outcomes in the few previously reported cases are reviewed and compared with our case. 相似文献
95.
PY Henry S Hariharan S Prathap TR Jeevaraj J Joseph 《Canadian Metallurgical Quarterly》1998,14(1-2):127-128
A unique case of benign sacrococcygeal teratoma associated with an N-type rectobulbar fistula is reported. 相似文献
96.
BA Gower TR Nagy CA Trowbridge C Dezenberg MI Goran 《Canadian Metallurgical Quarterly》1998,67(5):821-827
Ethnic differences in obesity-related disease prevalence may relate to differences in fat distribution or metabolism. We conducted a study in 73 African American and white children to examine the relation between fat distribution and insulin and to determine whether ethnic differences in fat distribution or in adiposity-insulin relations contribute to differences in insulin concentrations. Fasting and postchallenge insulin concentrations were determined by oral-glucose-tolerance test, total body fat by dual-energy X-ray absorptiometry, and subcutaneous abdominal (SAAT) and intraabdominal (IAAT) adipose tissue by computerized tomography. African Americans had greater fasting insulin (x +/- SD: 79 +/- 37 compared with 55 +/- 23 pmol/L, P < 0.01), incremental 30-min insulin (567 +/- 438 compared with 300 +/- 304 pmol/L, P < 0.001), and incremental area under the insulin curve (AUC; 262 +/- 209 compared with 164 +/- 156 pmol/L, P < 0.01). In multiple linear regression, fasting insulin was independently related to total fat within both ethnic groups (model R2 = 0.42 and 0.52 for African Americans and whites, respectively), incremental 30-min insulin to total fat and IAAT in whites only (model R2 = 0.71), and AUC to SAAT in African Americans only (model R2 = 0.49). Adjusting insulin indexes for adiposity did not eliminate the significant effect of ethnicity. In general, relations between adiposity and insulin were stronger in whites than in African Americans. African American children had higher insulin concentrations than white children after total body fat, IAAT, and SAAT were controlled for. However, strong relations between adiposity (total and abdominal) and insulin in both groups suggest that obesity may contribute to disease risk regardless of ethnicity. 相似文献
97.
SI Becker R Wang RC Hedstrom JC Aguiar TR Jones SL Hoffman MJ Gardner 《Canadian Metallurgical Quarterly》1998,66(7):3457-3461
Immunization of mice with DNA vaccines encoding the full-length form and C and N termini of Plasmodium yoelii merozoite surface protein 1 provided partial protection against sporozoite challenge and resulted in boosting of antibody titers after challenge. In C57BL/6 mice, two DNA vaccines provided protection comparable to that of recombinant protein consisting of the C terminus in Freund's adjuvant. 相似文献
98.
TR Mahalingam S Vijayalakshmi RK Prabhu A Thiruvengadasami CK Mathews KR Shanmugasundaram 《Canadian Metallurgical Quarterly》1997,57(3):191-206
Blood is one of the widely used specimens for biological trace element research because of its biological significance and ease of sampling. We have conducted a study of the blood of the Kalpakkam township population for trace and minor elements. For this purpose, analytical methods have been developed and standardized in our laboratory for the elemental analysis of blood plasma and red cells. Inductively coupled plasma-mass spectrometry (ICP-MS), a relatively new technique, has been applied for the analysis of trace elements. Details regarding spectral interference and matrix interference encountered in the analysis of blood and the methods of correcting them have been discussed. Flame atomic absorption spectrometry (AAS)/atomic emission spectrometry (AES) has been applied for the determination of minor elements. Precision and accuracy of these methods have also been discussed. 相似文献
99.
Implant micromotion is considered to be a major factor in the loosening of cementless total hip replacements. Translational micromotion at the bone-implant interface generally occurs in all three spatial directions. Under physiological loading, the interfacial micromotion consists of a cyclic amplitude and changes in the mean, which, in the cranio-caudal direction, represents subsidence of the prosthesis. Existing measurement strategies, which are based on dial gauges, extensometers, LVDTs, hall-effect transducers or strain gauge techniques provide information about only one component of the general three-dimensional micromovement. Moreover, in the majority of the studies, the data are difficult to interpret due to the measured motions being composed of interfacial micromotion and femoral strains. A new transducer was designed that allows the accurate measurement of all three isolated components of micromotion. An optoelectronic approach, based on silicon position-sensitive detectors (PSD) in combination with high precision mechanical parts, was chosen. To exclude thermodrifts during long-term testing, a thermistor was integrated in the sensor. Validation experiments on a precision positioning table indicated the high precision and resolution of the developed sensors. Furthermore, in-vitro tests on a standard press-fit prosthesis demonstrated the easy handling and reliability of the system. 相似文献
100.
OBJECTIVES: The purpose of this study was to determine the physiologic variables that predict major adverse events in children in the intensive care unit after cardiac operations. METHODS: A cohort observational study was conducted. At the time of admission to the intensive care unit and 4, 8, 12, and 24 hours later the following variables were recorded: mean arterial pressure, heart rate, cardiac index, oxygen delivery, mixed venous oxygen saturation, base deficit, blood lactate, gastric intramucosal pH, carbon dioxide difference (the difference between arterial carbon dioxide tension and gastric intraluminal carbon dioxide tension), and toe-core temperature gradient. Major adverse events were prospectively identified as cardiac arrest, need for emergency chest opening, development of multiple organ failure, and death. RESULTS: Ninety children were included in the study; 12 had major adverse events and there were 4 deaths. Blood lactate level, mean arterial pressure, and duration of cardiopulmonary bypass were the only significant, independent predictors of major adverse events when measured at the time of admission to the intensive care unit. The odds ratio (95% confidence intervals) for major adverse events if a lactate level was greater than 4.5 mmol/L was 5.1 (1.2 to 21.1), for admission hypotension 2.3 (0.5 to 9.8), and for a cardiopulmonary bypass time greater than 150 minutes 13.7 (3.3 to 57.2). Four hours after admission lactate and carbon dioxide difference, and 8 hours after admission lactate and base deficit, were independently significant predictors. The odds ratios for major adverse events if the blood lactate level was greater than 4 mmol/L at 4 and 8 hours were 8.3 (1.8 to 38.4) and 9.3 (1.9 to 44.3), respectively. At no time in the first 24 hours were cardiac output, oxygen delivery, mixed venous oxygen saturation, toe-core temperature gradient, or heart rate significant predictors of major adverse events. CONCLUSIONS: In the context of our current treatment strategies, the duration of cardiopulmonary bypass and blood lactate level, measured in the early postoperative period, were the best predictors of impending major adverse events. 相似文献