全文获取类型
收费全文 | 1677篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 6篇 |
建筑科学 | 1篇 |
轻工业 | 9篇 |
无线电 | 1篇 |
冶金工业 | 1640篇 |
原子能技术 | 1篇 |
自动化技术 | 20篇 |
出版年
2015年 | 1篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2001年 | 1篇 |
1999年 | 47篇 |
1998年 | 422篇 |
1997年 | 253篇 |
1996年 | 199篇 |
1995年 | 84篇 |
1994年 | 94篇 |
1993年 | 116篇 |
1992年 | 15篇 |
1991年 | 26篇 |
1990年 | 28篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 30篇 |
1986年 | 39篇 |
1985年 | 25篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 24篇 |
1978年 | 8篇 |
1977年 | 53篇 |
1976年 | 114篇 |
1975年 | 4篇 |
1955年 | 2篇 |
排序方式: 共有1678条查询结果,搜索用时 0 毫秒
951.
DP Slovut JC Wenstrom RB Moeckel RF Wilson JW Osborn JH Abrams 《Canadian Metallurgical Quarterly》1998,25(5):322-330
1. The present study was performed to test whether beat-to-beat cardiovascular control in cardiac allograft recipients resides in cholinergic and/or adrenergic nerves that are intrinsic to the heart. 2. Heart rate (HR) fluctuations synchronous with respiration during spontaneous, double tidal volume and metronome-synchronized breathing were quantified in 13 human heart transplant recipients. We also examined the effects of sequential cholinergic and beta-adrenoceptor (combined) autonomic blockade on respiratory sinus arrhythmia (RSA). We computed RSA amplitude and the correlation between respiration and changes in HR (cardiopulmonary synchronization; CPS). Group means were compared using repeated-measures analysis of variance. Transplant recipients served as their own controls. 3. In the basal state, moderate RSA amplitude and CPS were observed. During cholinergic and combined blockade, we observed no significant change in RSA amplitude, whereas CPS increased significantly during combined blockade (P < 0.05). The amplitude of RSA increased during respiration at double baseline tidal volume, but not at any of the other breathing manoeuvres (P < 0.01). In contrast, CPS increased significantly during both patterned breathing manoeuvres. No significant correlation was seen between mean right atrial pressure and RSA amplitude. In 23% of subjects with low CPS, HR oscillated with arterial pressure. These oscillations were independent of respiration. During all three patterns of respiration, a significant inverse correlation was observed between CPS and pulse pressure (r = -0.53 to -0.73). Thus, as the amplitude of pulse pressure increased, respiration accounted for a smaller percentage of HR variation. 4. In conclusion, RSA persists and the magnitude of CPS increases following combined autonomic blockade. These studies suggest that while RSA after cardiac transplantation is not cholinergically or adrenergically mediated, it may be related to mechanical stretch of the sinus node caused by changes in intrathoracic pressure and perfusion pressure. 相似文献
952.
DA Pettit MP Harrison JM Olson RF Spencer GA Cabral 《Canadian Metallurgical Quarterly》1998,51(3):391-402
A sample of UK consumers (N = 311) was interviewed in order to identify the attitudinal, cognitive and involvement characteristics of probable early adopters of polyunsaturated fatty acid (PUFA) fed fish. Attitude to fish significantly influenced PUFA fish, premium price PUFA fish, PUFA salmon, PUFA eel and PUFA sturgeon purchase. Involvement in healthy eating influenced PUFA fish, premium price PUFA fish and PUFA salmon purchase. Cognitive style did not influence PUFA fish and premium price PUFA fish purchase; nor, contrary to earlier research, did cognitive style and involvement interact to influence intended PUFA fish purchases. 相似文献
953.
AL Mason L Xu L Guo S Munoz JB Jaspan M Bryer-Ash Y Cao DM Sander Y Shoenfeld A Ahmed J Van de Water ME Gershwin RF Garry 《Canadian Metallurgical Quarterly》1998,351(9116):1620-1624
BACKGROUND: Retroviruses have been implicated in the aetiology of various autoimmune diseases. We used immunoblots as a surrogate test to find out whether retroviruses play a part in the development of primary biliary cirrhosis. METHODS: We did western blot tests for HIV-1 and the human intracisternal A-type particle (HIAP), on serum samples from 77 patients with primary biliary cirrhosis, 126 patients with chronic liver disease, 48 patients with systemic lupus erythematosus, and 25 healthy volunteers. FINDINGS: HIV-1 p24 gag seroreactivity was found in 27 (35%) of 77 patients with primary biliary cirrhosis, 14 (29%) of 48 patients with systemic lupus erythematosus, 14 (50%) of 28 patients with chronic viral hepatitis, and nine (39%) of 23 patients with either primary sclerosing cholangitis or biliary atresia, compared with only one (4%) of 24 patients with alcohol-related liver disease or alpha1-antitrypsin-deficiency liver disease, and only one (4%) of 25 healthy volunteers (p=0.003). Western blot reactivity to more than two HIAP proteins was found in 37 (51%) of patients with primary biliary cirrhosis, in 28 (58%) of patients with systemic lupus erythematosus, in 15 (20%) of patients with chronic viral hepatitis, and in four (17%) of those with other biliary diseases. None of the 23 patients with either alcohol-related liver disease or alpha1-antitrypsin deficiency, and only one of the healthy controls showed the same reactivity to HIAP proteins (p<0.0001). Our results showed a strong association between HIAP seroreactivity and the detection of autoantibodies to double-stranded DNA. HIAP seroreactivity was also strongly associated with the detection of mitochondrial, nuclear, and extractable nuclear antigens. INTERPRETATION: The HIV-1 and HIAP antibody reactivity found in patients with primary biliary cirrhosis and other biliary disorders may be attributable either to an autoimmune response to antigenically related cellular proteins or to an immune response to uncharacterised viral proteins that share antigenic determinants with these retroviruses. 相似文献
954.
955.
RF Hoyt SP Sorokin EM McDowell NA McNelly 《Canadian Metallurgical Quarterly》1993,236(1):15-22; discussion 22-4
Clusters of small-granule endocrine cells, neuroepithelial bodies (NEBs), appear in the airway lining of pseudoglandular lungs, but their prenatal function has remained obscure. Transplacental labeling of S-phase cells in Syrian golden hamsters has allowed us to relate NEBs to patterns of replication in the surrounding endoderm. Two methods were used: 1) continuous exposure to 3H-thymidine for the last 25% (4 days) of gestation, and 2) 2-hr exposure to 5-bromo-2'-deoxyuridine (BrdU) on fetal day 15. 3H-thymidine incorporation was assessed in autoradiographs of neonatal lung by grain counting from 923 nonendocrine and 251 endocrine cells in 28 airway epithelial terrains, each centered on a NEB: 12 in the perihilar, 8 in the middle, and 8 in the distal third of the left axial bronchus. Grain densities for 10-25 nonendocrine cells on either side of the NEB were plotted vs. position relative to the endocrine cell cluster and analyzed by rank-order correlation and linear regression. Label was highest in cells closest to NEBs in all 12 terrains (P < 0.05-0.001) in the perihilar airway, in 3 of 8 terrains (P < 0.025-0.001) in the middle third of the bronchus, and in respective, pooled populations (P < 0.001). The effect was not demonstrable in the distal third of the airway. In the 15-day fetus 243 mm of airway perimeter were measured and 3,218 BrdU-labeled epithelial cells counted from sections through the entire length of the left axial airway and the lobar bronchus, intermediate, and terminal bronchioles of the infracardiac (IC) lobe.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
956.
A method is outlined for modelling the relationship between breast-milk production and time from delivery, suitable for data collected longitudinally. The relationship is described using inverse polynomials. In a two-level model the coefficients are specified as random variables across subjects, allowing within- and between-subject variation to be separately estimated. In a three-level model, day-to-day variation can also be separately estimated. The model is illustrated using data from the Chiang Mai Lactation Project. It allows the use of covariates that vary over time, and provides a method of analysis that is compatible with the practical constraints on the timing of data collection that are inherent in longitudinal studies. 相似文献
957.
RF Jeffrey AA Khan JT Douglas EJ Will AM Davison 《Canadian Metallurgical Quarterly》1993,17(8):717-720
A preparation of low molecular weight heparin (Fragmin) was administered to patients with multiorgan failure receiving continuous venovenous hemodialysis. Three patients received a high-dose regimen (35 IU/kg bolus followed by 13 IU/kg infusion), and 7 received a low-dose regimen (8 and 5 IU/kg, respectively) for 36 h. High-dose Fragmin was associated with minimal clotting in the extracorporeal circuit. Plasma fibrinopeptide A levels declined, and mean anti-Xa activity was in the range 0.47-0.79 IU/ml. The urea equilibration coefficient (UEC) (100% at initiation) remained above 90% throughout. All 3 patients had mild bleeding episodes, which led to discontinuation of Fragmin in 1. During all low-dose treatments, marked thrombus formation occurred in the extracorporeal circuit, and in 2, the circuit clotted within the study period. Fibrinopeptide A levels further increased in 4 patients, and mean anti-Xa activity was in the range 0.27-0.53 IU/ml. UEC declined appreciably in 3 treatments (including the 2 in which early circuit clotting occurred). One patient experienced a mild bleeding episode. The low-dose Fragmin regimen produced safer anticoagulation in patients at risk from bleeding and is suitable for prolonged renal support although the tendency to thrombosis may necessitate more frequent circuit changes. 相似文献
958.
Bloomenthal M. Riesenfeld R. Cohen E. Fish R. Drake S. 《Robotics & Automation Magazine, IEEE》2001,8(3):25-32
Reports research on an experimental system for automated manufacturing with custom fixturing. In this approach, high level, feature-based shape models are transformed automatically into process plans from which computer numeric code for target machining centres is then derived automatically. This approach is targeted initially at parts with 2.5D features, including sculpted-exterior profiles and features requiring four- and five-axis indexing for manufacture. This part class has great practical utility and can be used to build very complex assemblies 相似文献
959.
Kai HUANG Xiao-xu ZHANG Si-wen XIU Dan-dan ZHENG Min YU De MA Kai HUANG Gang CHEN Xiao-lang YAN 《浙江大学学报:C卷英文版》2015,(2):135-152
研究目的:性能估计已成为异构MPSo C设计中一个非常重要且具有挑战性的任务。在设计早期进行准确快速估计性能对于设计空间探索十分必要。本文采用GCC剖析技术和代码标注技术,结合MPSo C分层抽象概念,探讨逐层次完善的性能评估技术在MPSo C体系结构探索中的应用。创新要点:为面向多媒体应用的MPSo C性能估计提出一个从VA层到TA层的剖析和标注相结合流程,使性能估计可以被有效逐层完善。研究方法:基于GNU gcov工具,在本机模拟过程中剖析给定应用程序代码执行的统计信息,并且支持实时性能分析,快速、准确估计VA模型的计算负载。基于VA模型得到的计算负载性能的结果标注,利用TA模型的System C时序精确级仿真得到通信延时结果,使TA模型性能估计更高效,完善整个MPSo C性能估计。重要结论:研究一个剖析和标注技术相结合的MPSo C性能评估方法和流程。在VA层得到准确计算负载性能并标注给TA层;在TA层利用基于标注的仿真方法完善通信延时,使得性能估计更高效。通过M-JPEG和MEPG2两个典型视频多媒体应用实验,展示本文方法的高效、快速与准确。 相似文献
960.
Kristin Potter Amy Gooch Bruce Gooch Peter Willemsen Joe Kniss Richard Riesenfeld Peter Shirley 《Computer Graphics Forum》2009,28(1):56-66
This work introduces a technique for interactive walk-throughs of non-photorealistically rendered (NPR) scenes using three-dimensional (3D) line primitives to define architectural features of the model, as well as indicate textural qualities. Line primitives are not typically used in this manner in favour of texture mapping techniques which can encapsulate a great deal of information in a single texture map, and take advantage of GPU optimizations for accelerated rendering. However, texture mapped images may not maintain the visual quality or aesthetic appeal that is possible when using 3D lines to simulate NPR scenes such as hand-drawn illustrations or architectural renderings. In addition, line textures can be modified interactively, for instance changing the sketchy quality of the lines. The technique introduced here extracts feature edges from a model, and using these edges, generates a reduced set of line textures which indicate material properties while maintaining interactive frame rates. A clipping algorithm is presented to enable 3D lines to reside only in the interior of the 3D model without exposing the underlying triangulated mesh. The resulting system produces interactive illustrations with high visual quality that are free from animation artifacts. 相似文献