全文获取类型
收费全文 | 323215篇 |
免费 | 25796篇 |
国内免费 | 13821篇 |
专业分类
电工技术 | 18835篇 |
技术理论 | 22篇 |
综合类 | 19839篇 |
化学工业 | 53779篇 |
金属工艺 | 17663篇 |
机械仪表 | 19874篇 |
建筑科学 | 26170篇 |
矿业工程 | 9015篇 |
能源动力 | 9307篇 |
轻工业 | 20150篇 |
水利工程 | 5709篇 |
石油天然气 | 18172篇 |
武器工业 | 2450篇 |
无线电 | 38847篇 |
一般工业技术 | 39311篇 |
冶金工业 | 16733篇 |
原子能技术 | 3471篇 |
自动化技术 | 43485篇 |
出版年
2024年 | 1414篇 |
2023年 | 5214篇 |
2022年 | 9607篇 |
2021年 | 12982篇 |
2020年 | 9608篇 |
2019年 | 8114篇 |
2018年 | 8778篇 |
2017年 | 10081篇 |
2016年 | 9193篇 |
2015年 | 12188篇 |
2014年 | 15717篇 |
2013年 | 19487篇 |
2012年 | 19907篇 |
2011年 | 22315篇 |
2010年 | 19244篇 |
2009年 | 18767篇 |
2008年 | 18013篇 |
2007年 | 17091篇 |
2006年 | 17189篇 |
2005年 | 14977篇 |
2004年 | 10260篇 |
2003年 | 9199篇 |
2002年 | 8988篇 |
2001年 | 7945篇 |
2000年 | 7442篇 |
1999年 | 8215篇 |
1998年 | 7273篇 |
1997年 | 5979篇 |
1996年 | 5598篇 |
1995年 | 4662篇 |
1994年 | 3784篇 |
1993年 | 2950篇 |
1992年 | 2280篇 |
1991年 | 1742篇 |
1990年 | 1355篇 |
1989年 | 1145篇 |
1988年 | 915篇 |
1987年 | 630篇 |
1986年 | 514篇 |
1985年 | 407篇 |
1984年 | 272篇 |
1983年 | 246篇 |
1982年 | 206篇 |
1981年 | 174篇 |
1980年 | 170篇 |
1979年 | 112篇 |
1978年 | 67篇 |
1977年 | 68篇 |
1976年 | 81篇 |
1975年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
91.
92.
秦山核电厂气载放射性释放的环境影响 总被引:3,自引:1,他引:2
本文评价了秦山核电厂气载放射性流出物对环境的影响。应用现场及风洞大气扩释实验结果和厂址周围的人口与食谱调查资料,估算了秦山核电厂在正常运行和事故条件下释放的气载放射性流出物对公众产生的个人有效剂量当量和集体有效剂量当量。计算结果表明,正常运行时厂址边界(0.5km)处的最大个人有效剂量当量为2.7×10~(-2)mSv/a,该剂量的大部分来自~(137)Cs 的食入(主要由地表湿沉积引起);80km 范围内的集体有效剂量当量为1.1人·Sv/a,归一化集体有效剂量当量为3.7人·Sv/GW(e)·a。文中还给出了事故情况下剂量估算结果。 相似文献
93.
A direct method for transient stability analysis of a multimachine power system is presented. Emphasis is placed on the detailed development and evaluation of the proposed method in transient stability assessment. An energy-type Lyapunov function, taking into account the effect of transfer conductance, is introduced first. The potential energy boundary surface method is then adopted to determine the critical energy value quickly. The main computational burden in the direct method lies in the reduction of the admittance matrices. In this paper, an efficient reduction technique incorporating the sparsity technique and compensation theory is developed. Finally, the proposed method was tested on the Taipower system, which is the only power system in Taiwan. The results obtained confirm the validity and accuracy of the proposed method, and hence demonstrate the superiority and potential of the direct method in real power system applications. 相似文献
94.
Juin-Hung Chen Hen-Wai Tsao 《Lightwave Technology, Journal of》1998,16(7):1137-1148
This paper presents a design method of optical frequency modulation (FM) subcarrier (with super carrier) transmission modem. The nonideal link characteristics, including laser chirping, fiber dispersion, voltage controlled oscillator (VCO) phase noise, relative intensity noise (RIN), and equivalent network model of laser diode of such a system that may bring about signal distortion are discussed first. We then propose a hierarchical methods to establish the system equivalent model. Finally this FM modem is applied to a GSM wireless system, in which multichannel signals are transmitted over fiber between radio port and basestation, and system performance is appraised by its dynamic range. It is found that optical FM subcarrier (with super carrier) transmission technique can improve the system dynamic range, compared with the intensity modulated direct detection (IMDD) method, and this is a economical and efficient method 相似文献
95.
T. -Y. Chen 《Structural and Multidisciplinary Optimization》1992,4(3-4):179-185
A design optimization procedure using a sequential linear programming technique is proposed in this paper to design minimum weight structures subjected to frequency response and static displacement constraints. The merit of the proposed approach is that the reanalyses of the static and dynamic responses, as well as the computations of the static and dynamic sensitivity data, are performed in a reduced approximate model. A significant saving of computer time for large scale structures is expected. Two numerical examples show good results of this method. 相似文献
96.
Haitao Zhang Zonghai Chen Yongji Wang Ming Li Ting Qin 《International Journal of Adaptive Control and Signal Processing》2006,20(2):53-76
Laguerre Functional Model has many advantages such as good approximation capability for the variances of system time‐delay, order and other structural parameters, low computational complexity, and the facility of online parameter identification, etc., so this model is suitable for complex industrial process control. A series of successful applications have been gained in linear and non‐linear predictive control fields by the control algorithm based on Laguerre Functional Model, however, former researchers have not systemically brought forward the theoretical analyses of the stability, robustness, and steady‐state performance of this algorithm, which are the keys to guarantee the feasibility of the control algorithm fundamentally. Aimed at this problem, we introduce the principles of the Incremental Mode Linear Laguerre Predictive Control (IMLLPC) algorithm, and then systemically propose the theoretical analyses and proofs of the stability and robustness of the algorithm, in addition, we also put forward the steady‐state performance analysis. At last, the control performances of this algorithm on two different physical industrial plants are presented in detail, and a number of experimental results validate the feasibility and superiority of IMLLPC algorithm. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
97.
This paper presents a method for multi-area power system total transfer capability (TTC) computation. This computation takes into account the limits on the line flows, bus voltage magnitude, generator reactive power, voltage stability, as well as the loss of line contingencies. The multi-area TTC problem is solved by using a network decomposition approach based on REI-type network equivalents. Each area uses REI equivalents of external areas to compute its TTC via the continuation power flow (CPF). The choice and updating procedure for the continuation parameter employed by the CPF is implemented in a distributed but coordinated manner. The proposed method leads to potential gains in the computational efficiency with limited data exchanges between areas. The developed procedure is successfully applied to the three-area IEEE 118-bus test system. Numerical comparisons between the integrated and the proposed multi-area solutions are presented for validation. 相似文献
98.
STUDYONRESIDUESOF~(14)C-FENITROTHIONINMODELRICE-FISHECOSYSTEMANDFIELDRICE-FISHECOSYSTEMZhangZhongliang(张仲良);WangHuaxin(王化新);G?.. 相似文献
99.
本文阐述了一种新型的X射线聚束装置─—X射线透镜的聚束原理。给出了透镜的基本设计方法,并对它应用于X射线光刻研究领域的前景作了展望。 相似文献
100.
用于重离子核反应实验测量的纵向电场气体电离室 总被引:1,自引:0,他引:1
本文报道了一种新型的大动态范围,多叠层探测器系统组件之一的纵向电场气体电离室的构造,性能和在中能得离子核反应实验中的应用。 相似文献