全文获取类型
收费全文 | 36708篇 |
免费 | 4106篇 |
国内免费 | 2097篇 |
专业分类
电工技术 | 2990篇 |
技术理论 | 1篇 |
综合类 | 2667篇 |
化学工业 | 5452篇 |
金属工艺 | 1967篇 |
机械仪表 | 2578篇 |
建筑科学 | 2726篇 |
矿业工程 | 1249篇 |
能源动力 | 1049篇 |
轻工业 | 3220篇 |
水利工程 | 808篇 |
石油天然气 | 1340篇 |
武器工业 | 401篇 |
无线电 | 4800篇 |
一般工业技术 | 3950篇 |
冶金工业 | 1590篇 |
原子能技术 | 416篇 |
自动化技术 | 5707篇 |
出版年
2024年 | 205篇 |
2023年 | 638篇 |
2022年 | 1400篇 |
2021年 | 1765篇 |
2020年 | 1405篇 |
2019年 | 1064篇 |
2018年 | 1264篇 |
2017年 | 1495篇 |
2016年 | 1310篇 |
2015年 | 2044篇 |
2014年 | 2418篇 |
2013年 | 2717篇 |
2012年 | 2966篇 |
2011年 | 3140篇 |
2010年 | 2729篇 |
2009年 | 2427篇 |
2008年 | 2328篇 |
2007年 | 2107篇 |
2006年 | 1940篇 |
2005年 | 1602篇 |
2004年 | 1182篇 |
2003年 | 791篇 |
2002年 | 686篇 |
2001年 | 555篇 |
2000年 | 480篇 |
1999年 | 371篇 |
1998年 | 325篇 |
1997年 | 244篇 |
1996年 | 229篇 |
1995年 | 167篇 |
1994年 | 137篇 |
1993年 | 130篇 |
1992年 | 118篇 |
1991年 | 81篇 |
1990年 | 52篇 |
1989年 | 74篇 |
1988年 | 40篇 |
1987年 | 38篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 21篇 |
1980年 | 29篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1970年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
基于地理信息系统的天津房地产管理数据库 总被引:1,自引:0,他引:1
从地理信息系统CIS的组成开始.提出该类系统的组织与管理方法,同时重点介绍了在现阶段开发该类系统时所使用的高端技术,最后对GIS系统的发展趋势作出分析与顶测。 相似文献
62.
63.
64.
生态用水和社会经济用水的竞争状况使得研究水资源短缺地区流域“三生”用水系统演化状况,以及有效进行流域“三生”用水系统的调控十分必要。从宏观角度出发,本文提出了构建流域主要指标为状态变量下的“三生”用水系统演化模拟模型,并利用模型进行演化趋势预测的分析思路。以蓟运河流域为例,构建了人口数量、人均GDP、生态系统指数以及生态用水比例为状态变量的“三生”用水系统演化模型。通过定量模拟,表明若不加以调控,该流域最终将走向生态失衡、经济停滞的恶性局面。由参数设置对调控方案进行分析,提出了提高生态用水比例、控制经济增长速度、提高用水效率和积极进行生态建设对策,为实现蓟运河流域的“三生”用水系统可持续发展服务。 相似文献
65.
分析了千兆以太网体系结构,给出了符合IEEE 802.3z标准中1000BASE-X规范的发送器电路结构,并采用TSMC 0.25 μm CMOS 混合信号工艺设计了符合该规范的高速复接电路和锁相环时钟倍频电路.芯片核心电路面积分别为(0.3×0.26)mm2和(0.22×0.12)mm2.工作电压2.5 V时,芯片核心电路功耗分别为120 mW和100 mW.时钟倍频电路的10倍频输出时钟信号频率为1.25 GHz,其偏离中心频率1MHz处的单边带相位噪声仅为-109.7 dBc/Hz.在驱动50 Ω输出负载的条件下,1.25 Gbit/s的高速输出数据信号摆幅可达到410 mV. 相似文献
66.
Fei Hu Ankur Teredesai 《Pervasive Computing, IEEE》2007,6(1):88-91
Today, there's an urgent need for well-trained pervasive computing engineers and scientists. Pervasive computing has evolved into a critical field, influencing a broad range of industries from healthcare to manufacturing to defense. However, most computer engineering and computer science programs pay marginal attention, at best, to the field. In this issue, the authors of the Rochester Institute of Technology describes a set of courses on pervasive computing topics and a supporting laboratory designed for both computer engineering and computer science students 相似文献
67.
Bonto-Kane Maria Vicente A. Chin Alvin Mc Carthy Sheila Srikulwong Mayuree Timmins Paul J. 《Pervasive Computing, IEEE》2007,6(4)
Pervasive computing is as much about the user as it is about the technology. So, the Fifth International Conference on Pervasive Computing emphasized desirability rather than just feasibility. Featured themes included user benefits, human-computer interaction, group and social interactions, context awareness, finding and positioning people and objects, and personal privacy. 相似文献
68.
In control systems, actuators often have nonlinear characteristics that can not be neglected. For linear systems driven by actuators satisfying the generalized sector condition, a robust state feedback controller synthesis method is proposed to achieve the ultimate boundedness control. The method is based on the linear matrix inequality approach and is easy to apply. As an important special case of the generalized sector condition, the saturation characteristic of actuators is discussed separately, and non‐conservative results are obtained. 相似文献
69.
H Lee KB Idler P Swanson JJ Aparicio KK Chin JP Lax M Nguyen T Mann G Leckie A Zanetti 《Canadian Metallurgical Quarterly》1993,196(1):57-69
Seven cardiac electrophysiology stimulators from four manufacturers (Biotronik, Bloom, Digitimer and Medtronic) in common current use are reviewed. The stimulators differ in the features provided and the design adopted to achieve these features. The number of output channels ranges from one to four, the number of extra-stimuli available ranges from two to six, and these can be delivered as a variety of sequences. Some of the stimulators (Digitimer and Bloom) are modular while others (Biotronik and Medtronic 532 series) are of an integrated design comprising a single physical unit. The design of the Medtronic EP-2 has both integrated and modular characteristics. The features of the stimulators associated with input, output, control and the user interface are specifically reviewed. The features are also compared against the published recommendations of the American Heart Association. In addition, a summary of stimulator user comments from a number of electrophysiology centres is presented. All of the stimulators fulfil, or are close to fulfilling, basic electrophysiological requirements, but some provide more complex facilities such as would be required by specialist centres. 相似文献
70.
The adult songbird forebrain undergoes neuronal production throughout adulthood, with the production of new neurons in discrete regions of the neostriatal ventricular zone. Upon mitogenesis, these new neurons migrate into the subjacent brain parenchyma along radially directed guide fibers. In long-term ventricular zone explant cultures, derived from the higher vocal center of the adult canary, newly migratory neurons were found to associate preferentially with a characteristic substrate cell type. These small, parvonuclear substrate cells formed tightly packed epithelioid sheets, in which ciliated ependymal cells were common, as recognized by both live observation and electron microscopy. A subpopulation of these cells was immunostained by monoclonal antibody 3A7, which preferentially stains the guide fiber network of the adult avian brain. These 3A7+ cells included ependymal cells and bipolar radial cells, as well as morphologically defined astrocytes. As they matured in vitro, the 3A7+ bipolar radial cells extended long, unbranching fibers, which ultimately traversed the culture substrate. Like ependymal cells, they supported neuronal migration. These cells were likely homologous to radial guide cells in vivo. Thus, neuronal migration in adult avian forebrain culture occurred upon guide cells of ependymal derivation. 相似文献