首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3200篇
  免费   53篇
  国内免费   2篇
电工技术   43篇
综合类   2篇
化学工业   346篇
金属工艺   39篇
机械仪表   49篇
建筑科学   82篇
矿业工程   6篇
能源动力   67篇
轻工业   261篇
水利工程   10篇
石油天然气   23篇
无线电   231篇
一般工业技术   328篇
冶金工业   1573篇
原子能技术   15篇
自动化技术   180篇
  2022年   19篇
  2021年   24篇
  2020年   26篇
  2019年   31篇
  2018年   29篇
  2017年   35篇
  2016年   41篇
  2015年   18篇
  2014年   30篇
  2013年   82篇
  2012年   68篇
  2011年   92篇
  2010年   56篇
  2009年   72篇
  2008年   72篇
  2007年   61篇
  2006年   44篇
  2005年   47篇
  2004年   63篇
  2003年   54篇
  2002年   37篇
  2001年   31篇
  2000年   42篇
  1999年   84篇
  1998年   444篇
  1997年   270篇
  1996年   181篇
  1995年   127篇
  1994年   95篇
  1993年   110篇
  1992年   29篇
  1991年   43篇
  1990年   41篇
  1989年   36篇
  1988年   46篇
  1987年   36篇
  1986年   38篇
  1985年   44篇
  1984年   31篇
  1983年   26篇
  1982年   39篇
  1981年   44篇
  1980年   34篇
  1979年   27篇
  1978年   32篇
  1977年   67篇
  1976年   119篇
  1975年   13篇
  1974年   19篇
  1973年   14篇
排序方式: 共有3255条查询结果,搜索用时 11 毫秒
71.
Although “User-Centred”, “Participatory”, and other similar design approaches have proved to be very valuable for mainstream design, their principles are more difficult to apply successfully when the user group contains, or is composed of, older and/or disabled users. In the field of design for older and disabled people, the “Universal Design”, “Inclusive Design” and “Design for All” movements have encouraged designers to extend their design briefs to include older and disabled people. The downside of these approaches is that they can tend to encourage designers to follow a traditional design path to produce a prototype design, and only then investigate how to modify their interfaces and systems to cope with older and/or disabled users. This can lead to an inefficient design process and sometimes an inappropriate design, which may be “accessible” to people with disabilities, but in practice unusable. This paper reviews the concept that the authors have called “User-Sensitive Inclusive Design”, which suggests a different approach to designing for marginalised groups of people. Rather than suggesting that designers rely on standards and guidelines, it is suggested that designers need to develop a real empathy with their user groups. A number of ways to achieve this are recommended, including the use of ethnography and techniques derived from professional theatre both for requirements gathering and for improving designers’ empathy for marginalised groups of users, such as older and disabled people.  相似文献   
72.
In recent years, studies have shown that video game experience is related to improvements across a variety of cognitive and visuospatial tasks. This study investigated the relationship between prior video game experience and spatial performance in virtual and real environments. Across two experiments, gaming experience was related to performance in desktop virtual environments; those with more video game experience were more accurate in pointing to nonvisible targets. In contrast, gaming experience was unrelated to three different real environment tasks, suggesting that video games may primarily influence perceptual and cognitive abilities in the visual domain over abilities that also involve kinesthetic or vestibular input. Contrary to expectations, gaming experience was also related to performance in immersive virtual environments, which may be related to the use of a joystick interface during immersive travel. Video game experience was also positively related to performance in a dynamic spatial task and to verbal SAT and math SAT scores. Sex differences in desktop virtual navigation and dynamic spatial ability were eliminated when game experience was included as a covariate.  相似文献   
73.
74.
Stepwise refinement is a crucial conceptual tool for system development, encouraging program construction via a number of separate correctness-preserving stages which ideally can be understood in isolation. A crucial conceptual component of security is an adversary’s ignorance of concealed information. We suggest a novel method of combining these two ideas.Our suggestion is based on a mathematical definition of “ignorance-preserving” refinement that extends classical refinement by limiting an adversary’s access to concealed information: moving from specification to implementation should never increase that access. The novelty is the way we achieve this in the context of sequential programs.Specifically we give an operational model (and detailed justification for it), a basic sequential programming language and its operational semantics in that model, a “logic of ignorance” interpreted over the same model, then a program-logical semantics bringing those together — and finally we use the logic to establish, via refinement, the correctness of a real (though small) protocol: Rivest’s Oblivious Transfer. A previous report? treated Chaum’s Dining Cryptographers similarly.In passing we solve the Refinement Paradox for sequential programs.  相似文献   
75.
针对卫星通信网络吞吐量不足、可靠性不高的问题,提出一种基于复数域网络编码(Complex Field Network Coding,CFNC)的卫星通信方案。该方案在信号发送前对源信息作预编码处理,即在复数域上选取一个大小合适的参数化空时码与源信号相乘,编码后的信号与源信号在复数域上有着一一映射关系。对该方案的吞吐量和成对差错概率(Pairwise Error Probability,PEP)做了详尽的理论分析,结果表明,采用该编码方案的卫星通信系统在终端发射功率不变的情况下,吞吐量比路由模式提高了100%以上,比传统的CFNC方式至少可提高75%。该方案还可以扩展至更多的地面源节点,从而支持多用户网络通信。最后,仿真实验表明,在较高的信噪比下,PEP仿真值逼近于渐近值,验证了理论分析的正确性。  相似文献   
76.
Under study was the efficacy of three schedules of dose fractionation in intracavitary gamma-therapy in cervical cancer patients treated on the machine "AGAT-B". Single doses were 1000, 700 and 500 rad, while total dosage at point A depending on the stage of the disease was within the range of 4000-5000 rad. The survival during the first, second and third years following termination of the radiotherapy was found to be identical for patients of all the groups under examination. No differences were noted in them also in the character of early radiation reactions on the part of the adjacent organs. The frequency and severity of late radiation injuries of the urinary bladder, rectum and vagina were related to the dose fractionation regimen.  相似文献   
77.
Dufour Gland Contents of Ants of the Cataglyphis bicolor Group   总被引:1,自引:0,他引:1  
The species of desert-dwelling ants of the Cataglyphis bicolor (Hymenoptera: Formicidae) group are difficult to distinguish by morphological features. Analysis of the secretion from the Dufour glands of workers of a number of colonies was undertaken to see if it provided a clear test of species. Linked 6c-ms showed in all samples straight and branched-chain alkanes, linear alkenes, ketones, aldehydes, acetates, and a group of C22 to C28 esters not previously identified in this genus. Contents of the Dufour glands of C. savignyi from Tunisia and Egypt were similar, and comprised straight and branched-chain alkanes, alkenes and small amounts of esters. C. bicolor from Tunisia contained compounds similar to C. savignyi but was distinguished from the latter by larger amounts of the esters. The major compound in the glands of C. viaticus was tridecane, in contrast to the pentadecane of other species. It also contained a branched alkane, 3-methyltridecane as a major component. Branched-chain esters and a wide variety of acetates were also found in this species. C. diehlii had a limited range of compounds, with branched alkanes almost completely absent and high proportions of pentadecene and dodecyl acetate. C. bombycinus, a sympatric species, but recognized as not belonging to the bicolor group by its different mandibular gland substances, was notable in having butanoate esters in its Dufour glands. Despite these differences among species, both the great variability of individuals from a single colony and the among between conspecific colonies make species diagnosis from a few individuals difficult, in contrast with postpharyngeal glands, which, as recently reported, give a clearer indication of species.  相似文献   
78.
It has been stated that boiled for three hours haemocytocardiotoxin (HT) from cobra poison loses "direct" hemolytic activity and is unable to potentiate a haemolytic effect of phospholipase A. Surface activity of HT does not change. It is shown that in the course of heat denaturation the aggregation of toxin molecules to dimers and trimers takes place and electrophoretic mobility is decreased. The fluorescence of HT tyroxin residues supported the fact of its irreversible heat denaturation.  相似文献   
79.
Compositional noninterference from first principles   总被引:1,自引:1,他引:0  
The recently formulated Shadow Semantics for noninterference-style security of sequential programs avoids the Refinement Paradox by preserving demonic nondeterminism in those cases where reducing it would compromise security. The construction (originally) of the semantic domain for The Shadow, and the interpretation of programs in it, relied heavily on intuition, guesswork and the advice of others. That being so, it is natural after the fact to try to reconstruct an idealised “inevitable” path from first principles to where we actually ended up: not only does one learn (more) about semantic principles by doing so, but the “rational reconstruction” helps to expose the choices made, along the way, and to legitimise the decisions that resolved them. Unlike our other papers on noninterference, this one does not contain a significant case study: instead its aim is to provide the most accessible account we can of the methods we use and why our model, in its details, has turned out the way it has. In passing, it might give some insight into the general role and significance of compositionality and testing-with-context for program semantics. Finally, a technical contribution here is a new “Transfer Principle” that captures uniformly a large class of classical refinements that remain valid when noninterference is taken into account in our style.  相似文献   
80.
To test whether pain blocked by hypnotic analgesia may still be perceived at some level, 20 highly hypnotizable undergraduates participated in an experiment involving cold pressor pain in the normal condition and in hypnotically suggested analgesia. 3 reports were obtained reflecting felt pain within the hypnotic analgesia condition: the usual verbal report on a numerical scale, a manual report by "automatic key pressing," and a retrospective verbal report through "automatic talking." 9 Ss who were amnesic for both keypressing and automatic talking reported more pain in the automatic (hidden) reports than in their usual verbal reports. 8 of these 9, following release of amnesia, had a clear perception of 2 levels of awareness of the pain: the usual hypnotic experience of pain attenuated by analgesia suggestions, and a knowledge at another level of a more severe pain. In no case, however, did an S give a retrospective report of normal suffering at this "hidden" level. The hypnotically analgesic S may have reported no pain verbally because he was amnesic for it; when amnesia was removed he recalled the sensory pain, but without a suffering component, because suffering apparently did not occur. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号