全文获取类型
收费全文 | 348920篇 |
免费 | 28333篇 |
国内免费 | 17286篇 |
专业分类
电工技术 | 21851篇 |
技术理论 | 60篇 |
综合类 | 48279篇 |
化学工业 | 34747篇 |
金属工艺 | 15179篇 |
机械仪表 | 23486篇 |
建筑科学 | 51155篇 |
矿业工程 | 18396篇 |
能源动力 | 10595篇 |
轻工业 | 17598篇 |
水利工程 | 18208篇 |
石油天然气 | 14160篇 |
武器工业 | 3387篇 |
无线电 | 21649篇 |
一般工业技术 | 30832篇 |
冶金工业 | 19037篇 |
原子能技术 | 3294篇 |
自动化技术 | 42626篇 |
出版年
2024年 | 1049篇 |
2023年 | 3310篇 |
2022年 | 6357篇 |
2021年 | 7617篇 |
2020年 | 8128篇 |
2019年 | 6839篇 |
2018年 | 6614篇 |
2017年 | 8238篇 |
2016年 | 9767篇 |
2015年 | 11175篇 |
2014年 | 20508篇 |
2013年 | 18718篇 |
2012年 | 23391篇 |
2011年 | 25226篇 |
2010年 | 19809篇 |
2009年 | 21073篇 |
2008年 | 19567篇 |
2007年 | 25245篇 |
2006年 | 23684篇 |
2005年 | 20390篇 |
2004年 | 17152篇 |
2003年 | 15321篇 |
2002年 | 12584篇 |
2001年 | 10521篇 |
2000年 | 9048篇 |
1999年 | 7364篇 |
1998年 | 5559篇 |
1997年 | 4861篇 |
1996年 | 4534篇 |
1995年 | 3780篇 |
1994年 | 3359篇 |
1993年 | 2487篇 |
1992年 | 2194篇 |
1991年 | 1635篇 |
1990年 | 1404篇 |
1989年 | 1236篇 |
1988年 | 992篇 |
1987年 | 671篇 |
1986年 | 494篇 |
1985年 | 410篇 |
1984年 | 389篇 |
1983年 | 292篇 |
1982年 | 247篇 |
1981年 | 200篇 |
1980年 | 177篇 |
1979年 | 133篇 |
1978年 | 80篇 |
1977年 | 81篇 |
1976年 | 57篇 |
1975年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
L. S. Mazov 《Journal of Superconductivity and Novel Magnetism》2007,20(7-8):583-585
It is demonstrated that scattering of mobile charge carriers by fluctuations of local spin density in the normal state of
SC-cuprates results in anomalous contribution to the transport phenomena (Hall and Nernst effects are included). Depending
on their sign and magnitude, they can change value and sign of the corresponding effect measured. 相似文献
982.
Mark S. MACGREGOR Sue J. CARR 《Hemodialysis international. International Symposium on Home Hemodialysis》2007,11(Z2):S1-S4
Hemodialysis was a neglected aspect of nephrology in the UK. At the request of the Renal Association, the first UK Haemodialysis Masterclass was organized in 2007. The articles in this supplement arose from that meeting. Here, an overview of UK hemodialysis services and nephrology training is presented as background. Government‐funded dialysis should be provided to all UK citizens who require it. In 2005, there were 17,645 patients receiving hemodialysis, 5057 on peritoneal dialysis and 19,074 with kidney transplants, looked after by 359 nephrologists working in 73 National Health Service renal units. Renal replacement therapy incidence and prevalence remain comparatively low, at 108 and 694 per million population, respectively. Whether this represents inadequate provision or genuinely lower need remains unclear. The Renal Association sets clinical practice guidelines for dialysis, and audits performance via the UK Renal Registry. Postgraduate medical education is undergoing radical change in the UK. This is driven by the reduction in trainee doctors' working hours to 48 hr/week (mandated by the European Working Time Directive), and the governments' wish to reduce the duration of training, but also by a desire to formalize training, Our challenge is to continue to produce talented clinical nephrologists educated in breadth and depth, despite the reduced emphasis on clinical experience and omission of period of scientific research. The future for hemodialysis services in the UK is, however, promising with an expansion in the number of specialists and dialysis centers, and a growing interest in dialysis practice and research. 相似文献
983.
Mark S. MACGREGOR 《Hemodialysis international. International Symposium on Home Hemodialysis》2007,11(Z2):S10-S16
Survival of patients on hemodialysis remains poor, but the benefits of increasing urea clearance have probably been maximized within our current treatment schedules. Long dialysis sessions (8 hr) produce impressive outcomes, with mortality 53% to 55% lower than conventional schedules. Even increasing from 4 to 5 hr may improve survival. Increased frequency of dialysis (6 times weekly) produces impressive reductions in left ventricular mass and could conceivably be implemented in‐center. Preliminary data suggest a 61% reduction in mortality with increased frequency. Nightly dialysis combines longer sessions with increased frequency and has produced remarkable clinical gains in blood pressure, left ventricular mass, serum phosphate, and sleep apnea. However, the data are mainly from case series and impact on mortality remains unknown. Expansion of home hemodialysis would be necessary for this modality to grow. Convective therapies remove middle molecules more effectively, and observational data suggest hemodiafiltration has the potential to improve mortality by 35% to 36%. Hemodiafiltration has the advantage of being relatively easy to implement. The uremic milieu is complex and further investigation of the underlying pathophysiology is needed to inform future dialysis interventions. The survival data above are from observational studies, and hence benefits are likely to be exaggerated. Randomized trials of dialysis interventions are desperately needed. They remain difficult to perform, because of the complexity of both the patient population and the interventions, and because of limited available funding. 相似文献
984.
新经济增长理论对我国人力资本发展的借鉴 总被引:3,自引:0,他引:3
新经济增长理论为人力资本理论注入了新的内容,为各国如何利用人力资本发展经济提供了理论指导。分析了新经济增长理论中有关人力资本的理论,以此对我国经济和人力资本的发展提出了一些借鉴;收益递增模型。 相似文献
985.
数字移动电视的现状与发展前景 总被引:2,自引:0,他引:2
随着数字电视的普及推广,数字移动电视应运而生,并得到迅速发展。数字移动电视通常安装在交通工具上,兼具移动性和数字化的特点。它突破了传统电视固定收视的局限,带来了电视传播的新概念。同时,数字移动电视根据自身传播特性,不断探索新的运营模式,并带来一系列的产业链效应,蕴含着无限商机 相似文献
986.
吴桂金 《河南机电高等专科学校学报》2004,12(5):64-65
由于过烧石灰的存在和消解不当等原因,造成消石灰安定性不合格,当石灰稳定类路面结构成型或投入使用后,消石灰中的生石灰颗粒开始吸收周围水分,慢慢消解,消解过程中发生体积膨胀,对路面产生破坏。解决石灰安定性问题对防止公路前修后坏,延长路面使用寿命具有积极的现实意义。 相似文献
987.
道路与匝道中线自动绘制的算法与实现 总被引:1,自引:0,他引:1
道路与立交匝道平面中线的计算机自动绘制是道路路线CAD软件的核心功能之一,在道路工程计算机动态交互式设计、计算机辅助成图方面具有基础性作用.依据道路中线线形的曲率变化特点,推导了道路中线坐标计算的通用数学模型,并根据一个工程实例在通用图形系统AutoCAD环境下实现了道路与匝道中线的自动绘制. 相似文献
988.
The behavior of an ultrasonic shot peening process is observed and analyzed by using a model of inelastic hard spheres in a gravitational field that are fluidized by a vibrating bottom wall (sonotrode) in a cylindrical chamber. A marked heterogeneous distribution of impacts appears when the collision between the shot and the side wall becomes inelastic with constant dissipation. This effect is one order of magnitude larger than the simple heterogeneity arising from boundary collision on the cylinder. Variable restitution coefficients bring the simulation closer to the general observation and allow the investigation of peening regimes with changing shot density. We compute within this model other physical quantities (impact velocities, impact angle, temperature and density profile) that are influenced by the number N of spheres. 相似文献
989.
Ashraf Ayoub 《Computers & Structures》2003,81(7):411-421
This paper presents an inelastic element for the analysis of beams on foundations. The element is derived from a two-field mixed formulation with independent approximation of forces and displacements. The state determination algorithm for the implementation of the element in a general purpose nonlinear finite element analysis program is presented and its stability characteristics are discussed. Numerical studies are performed to compare the model with the classical displacement formulation. The studies confirm the superiority of the proposed model in describing the inelastic behavior of beams on foundations. 相似文献
990.
References: 《计算技术与自动化》2003,22(Z1):54-57
In order to avoid unnecessary damage of electrical equipments and installations,high quality power should be delivered to the end user and strict control on frequency should be made, Therefore, it is important to estimate the power system's harmonic components with higher accuracy. This paper presents a new approach for estimating harmonic component in a power system using secant - fuzzy linear regression method. In this approach the non - sinusoidal voltage or current waveform is written as I linear function. The coefficient of this function is assumed to be fuzzy number with a membership function that has center and spread value. The time dependent quantity is written as Taylor series with two different time dependent quantities. The objective is to use the sample obtained from the transmission line to find the power system harmonic components and frequencies. We used an experimental voltage signal from a sub power station as a numerical test. 相似文献