全文获取类型
收费全文 | 5312篇 |
免费 | 64篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 62篇 |
综合类 | 28篇 |
化学工业 | 270篇 |
金属工艺 | 39篇 |
机械仪表 | 202篇 |
建筑科学 | 83篇 |
矿业工程 | 23篇 |
能源动力 | 31篇 |
轻工业 | 506篇 |
水利工程 | 11篇 |
石油天然气 | 14篇 |
无线电 | 172篇 |
一般工业技术 | 411篇 |
冶金工业 | 3177篇 |
原子能技术 | 18篇 |
自动化技术 | 345篇 |
出版年
2022年 | 26篇 |
2020年 | 26篇 |
2019年 | 41篇 |
2018年 | 19篇 |
2016年 | 21篇 |
2015年 | 21篇 |
2014年 | 31篇 |
2013年 | 247篇 |
2012年 | 78篇 |
2011年 | 86篇 |
2010年 | 65篇 |
2009年 | 74篇 |
2008年 | 97篇 |
2007年 | 107篇 |
2006年 | 73篇 |
2005年 | 84篇 |
2004年 | 75篇 |
2003年 | 68篇 |
2002年 | 70篇 |
2001年 | 58篇 |
2000年 | 64篇 |
1999年 | 139篇 |
1998年 | 1006篇 |
1997年 | 568篇 |
1996年 | 377篇 |
1995年 | 223篇 |
1994年 | 177篇 |
1993年 | 208篇 |
1992年 | 52篇 |
1991年 | 67篇 |
1990年 | 65篇 |
1989年 | 71篇 |
1988年 | 79篇 |
1987年 | 76篇 |
1986年 | 59篇 |
1985年 | 71篇 |
1984年 | 29篇 |
1983年 | 30篇 |
1982年 | 41篇 |
1981年 | 50篇 |
1980年 | 31篇 |
1979年 | 33篇 |
1978年 | 18篇 |
1977年 | 93篇 |
1976年 | 174篇 |
1975年 | 23篇 |
1974年 | 16篇 |
1973年 | 18篇 |
1955年 | 21篇 |
1954年 | 17篇 |
排序方式: 共有5392条查询结果,搜索用时 15 毫秒
61.
E Buskens EW Steyerberg J Hess JW Wladimiroff DE Grobbee 《Canadian Metallurgical Quarterly》1997,87(6):962-967
OBJECTIVES: This study assessed the potential impact of fetal ultrasound screening on the number of newborns affected by cardiac anomalies. METHODS: A decision model was developed that included the prevalence and history of congenital heart disease, characteristics of ultrasound, risk of abortion, and attitude toward pregnancy termination. Probabilities were obtained with a literature survey; sensitivity analysis showed their influence on expected outcomes. RESULTS: Presently, screening programs may prevent the birth of approximately 1300 severely affected newborns per million second-trimester pregnancies. However, over 2000 terminations of pregnancy would be required, 750 of which would have ended in intrauterine death or spontaneous abortion. Further, 9900 false-positive screening results would occur, requiring referral. Only the sensitivity of routine screening and attitude toward termination of pregnancy appeared to influence the yield substantially. CONCLUSIONS: The impact of routine screening for congenital heart disease appeared relatively small. Further data may be required to fully assess the utility of prenatal screening. 相似文献
62.
SUSANNA DE CORDT MARC HENDRICKX GEERT MAESMANS PAUL TOBBACK 《International Journal of Food Science & Technology》1992,27(6):661-673
Biphasic and nth-order models were tested as to their usefulness to fit experimental inactivation data of Bacillus licheniformis α-amylase, immobilized on glass beads, and were discussed with respect to their suitability to characterize the considered enzymic system as a time—temperature integrator (TTI) to evaluate heat processes. Both isothermal and non-isothermal inactivation experiments were carried out. Model (kinetic) parameters (rate constant k, activation energy EA and reaction order n) were estimated using a non-linear regression procedure. The results obtained, especially the activation energy of about 293 kJ mole–1 , indicated a potential use of this system as a TTI for heating processes in the temperature range of 96–108°C. 相似文献
63.
Examined intake profiles of 54 depressed women survivors of child sexual abuse presenting for a specialized group therapy program at a community mental health center. The 32 therapy completers were compared with the 22 dropouts. Both groups possessed extensive and severe childhood and adult abuse histories. Both were extremely socially disadvantaged and clinically impaired as measured on the Millon Clinical Multiaxial Inventory (MCMI). Dropouts were more likely to have been battered as children and to have been sexually abused only within the family. Completers were more likely to have been multiply offended both by intrafamilial and extrafamilial perpetrators. The groups differed in terms of marital status and extent of economic dependence on spouse. Dropouts appeared to be more actively enmeshed in the abuse cycle at the time of therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
Learned behaviors and tolerance to ethanol can be maintained by peripheral injection of arginine8-vasopressin (vasopressin) under conditions in which they would otherwise be lost. However, the sites of this action in the brain have not been clearly identified. Using a polyclonal antibody raised against Fos and Fos-like proteins, we have demonstrated increases in immunoreactive Fos and Fos-like proteins in the suprachiasmatic, supraoptic and paraventricular nuclei of the hypothalamus, and lesser increases in piriform cortex and amygdala, of the rat 2 h after a s.c. injection of vasopressin. Our results suggest that the exogenous vasopressin may exert its central action by activating a cellular immediate early gene in specific brain regions. 相似文献
65.
D. Grant Fisher 《加拿大化工杂志》1991,69(1):5-26
This paper presents an overview and personnal perspective on recent developments and current practice in computer process model. The basic concepts behind conventional process control are reviewed to provide a starting point for the non-control specialist and process engineer. The ensuing sections on Internal Model Control (IMC), Model Predictive Control (MPC) and adaptive control illustrate the evolution of control technology from the traditional multiloop strategies to the modern, multivariable, model-based, computer control systems now being used in industry. The paper does not provide a complete, critical review of process control. However, the discussion and the recommended references should provide a good starting point for anyone wanting to become familiar with current practice and some of the new directions of process control. 相似文献
66.
Ariosto B. Jorge Gabriel O. Ribeiro Timothy S. Fisher 《International journal for numerical methods in engineering》2003,56(1):117-144
This work presents two new error estimation approaches for the BEM applied to 2D potential problems. The first approach involves a local error estimator based on a gradient recovery procedure in which the error function is generated from differences between smoothed and non‐smoothed rates of change of boundary variables in the local tangential direction. The second approach involves the external problem formulation and gives both local and global measures of error, depending on a choice of the external evaluation point. These approaches are post‐processing procedures. Both estimators show consistency with mesh refinement and give similar qualitative results. The error estimator using the gradient recovery approach is more general, as this formulation does not rely on an ‘optimal’ choice of an external parameter. This work presents also the use of a local error estimator in an adaptive mesh refinement procedure. This r‐refinement approach is based on the minimization of the standard deviation of the local error estimate. A non‐linear programming procedure using a feasible‐point method is employed using Lagrange multipliers and a set of active constraints. The optimization procedure produces finer meshes close to a singularity and results that are consistent with the problem physics. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
67.
68.
69.
Human gene for physical performance 总被引:2,自引:0,他引:2
70.