全文获取类型
收费全文 | 22662篇 |
免费 | 935篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 300篇 |
综合类 | 24篇 |
化学工业 | 4838篇 |
金属工艺 | 406篇 |
机械仪表 | 473篇 |
建筑科学 | 1319篇 |
矿业工程 | 68篇 |
能源动力 | 646篇 |
轻工业 | 2353篇 |
水利工程 | 145篇 |
石油天然气 | 67篇 |
武器工业 | 1篇 |
无线电 | 1933篇 |
一般工业技术 | 3707篇 |
冶金工业 | 3709篇 |
原子能技术 | 224篇 |
自动化技术 | 3411篇 |
出版年
2023年 | 173篇 |
2022年 | 338篇 |
2021年 | 512篇 |
2020年 | 377篇 |
2019年 | 421篇 |
2018年 | 480篇 |
2017年 | 433篇 |
2016年 | 582篇 |
2015年 | 500篇 |
2014年 | 670篇 |
2013年 | 1269篇 |
2012年 | 1043篇 |
2011年 | 1295篇 |
2010年 | 924篇 |
2009年 | 1013篇 |
2008年 | 1054篇 |
2007年 | 942篇 |
2006年 | 901篇 |
2005年 | 751篇 |
2004年 | 639篇 |
2003年 | 575篇 |
2002年 | 512篇 |
2001年 | 378篇 |
2000年 | 405篇 |
1999年 | 412篇 |
1998年 | 885篇 |
1997年 | 577篇 |
1996年 | 485篇 |
1995年 | 338篇 |
1994年 | 347篇 |
1993年 | 318篇 |
1992年 | 235篇 |
1991年 | 202篇 |
1990年 | 186篇 |
1989年 | 189篇 |
1988年 | 169篇 |
1987年 | 168篇 |
1986年 | 146篇 |
1985年 | 201篇 |
1984年 | 191篇 |
1983年 | 161篇 |
1982年 | 125篇 |
1981年 | 147篇 |
1980年 | 136篇 |
1979年 | 137篇 |
1978年 | 129篇 |
1977年 | 170篇 |
1976年 | 194篇 |
1975年 | 113篇 |
1974年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
D Martin 《Canadian Metallurgical Quarterly》1998,28(7):52-53
A clinical ladder identifies nursing competence, provides recognition and financial reward for bedside nursing practice, promotes responsibility, accountability, project and committee involvement, and enhances self-worth and positive morale. Because of the program's blend of skill levels, it develops a climate for clinical learning while promoting professional growth and confidence. 相似文献
33.
34.
By nature, cryptographers tend to be extremely cautious and conservative. From their perspective, spending time getting people to use a new cryptographic algorithm is roughly on par with getting involved in a land war in Asia. In some cases, however, the difficulty involved in developing a new algorithm is worth the effort. This is the case with identity-based encryption (IBE), a new type of public-key algorithm 相似文献
35.
Steel box sections are usually fabricated from flat plates which are welded at the corners. The welding process can introduce residual stresses and geometric imperfections into the sections which can influence their strength. For some thin-walled sections, large periodic geometric imperfections have been observed in manufactured sections. Subsequent investigations have indicated that the imperfections are in fact buckling deformations i.e. the box section has buckled due to welding residual stresses prior to any application of external load. The welding procedure and the behaviour of the box sections under load has been modelled using a finite element analysis that accounts for both geometric and material non-linearities. Tests have been carried out on box sections with a range of width to thickness ratios for the plate elements. Modelling has been shown to give good correlation with the test results. The conditions for buckling to take place as a result of the welding process have been established. A design method has been proposed. 相似文献
36.
Karl Rihaczek 《Datenschutz und Datensicherheit - DuD》2006,30(3):131-131
Ohne Zusammenfassung 相似文献
37.
A comparison between different PMD compensation techniques 总被引:17,自引:0,他引:17
Sunnerud H. Chongjin Xie Karlsson M. Samuelsson R. Andrekson P.A. 《Lightwave Technology, Journal of》2002,20(3):368-378
We quantify the benefits of using different techniques for compensation of polarization mode dispersion (PMD) in fiber-optic communication systems by means of numerical simulations. This is done both with respect to PMD-induced pulse broadening and in terms of system outage probability for different data formats [nonreturn-to-zero (NRZ) and return-to-zero (RZ)]. Attention is focused on simple and relevant single- and double-stage post-transmission compensators with a few degrees of freedom (DOF). It is generally believed that a PMD compensator with a polarization controller and a variable delay line can only compensate the PMD to the first order. We show, from analytical results, the counterintuitive fact that this scheme can also partially compensate for higher order PMD. We also investigate the benefit of using a polarizer as compensation element where the optical average power can be used as a feedback signal 相似文献
38.
当今,从事OC-48、OC-192技术的设计师在设计基于因特网协议(IP协议)的下一代系统时,因系统含有诸如ASIC、网络处理器(NP)、高速跟踪器等元件,以及分组SONET物理层(PoS-PHY)接口规范等的演变,而一直面临挑战。抖动和扭斜失真等现象的存在给诸如系统分组接口第4层(SPI-4)和通用交换接口(CSIX)等总线结构本已拥挤的时序容限,以及四元数据率静态RAM传送表访问时间带来极大混乱。再加上诸如低压差分信号(LVDS)、高速收发逻辑和短线串行终端逻辑等超低电压峰-峰信号技术的引入,使数据出错的可能性变得异常之高。而利用仿真技… 相似文献
39.
The cost of maintaining a software system over a long period of time far exceeds its initial development cost. Much of the maintenance cost is attributed to the time required by new developers to understand legacy systems. High-level structural information helps maintainers navigate through the numerous low-level components and relations present in the source code. Modularization tools can be used to produce subsystem decompositions from the source code but do not typically produce high-level architectural relations between the newly found subsystems. Controlling subsystem interactions is one important way in which the overall complexity of software maintenance can be reduced.We have developed a tool, called ARIS (Architecture Relation Inference System), that enables software engineers to define rules and relations for regulating subsystem interactions. These rules and relations are called Interconnection Styles and are definedusing a visual notation. The style definition is used by our tool to infer subsystem-level relations in designs being reverse engineered from source code.In this paper we describe our tool and its underlying techniques and algorithms. Using a case study, we describe how ARIS is used to reverse engineer high-level structural information from a real application. 相似文献
40.