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   3800篇
  免费   146篇
  国内免费   1篇
电工技术   29篇
化学工业   843篇
金属工艺   30篇
机械仪表   68篇
建筑科学   136篇
矿业工程   10篇
能源动力   65篇
轻工业   683篇
水利工程   43篇
石油天然气   9篇
无线电   162篇
一般工业技术   371篇
冶金工业   1145篇
原子能技术   8篇
自动化技术   345篇
  2023年   22篇
  2022年   92篇
  2021年   87篇
  2020年   66篇
  2019年   53篇
  2018年   70篇
  2017年   72篇
  2016年   70篇
  2015年   70篇
  2014年   94篇
  2013年   232篇
  2012年   164篇
  2011年   192篇
  2010年   144篇
  2009年   165篇
  2008年   146篇
  2007年   163篇
  2006年   129篇
  2005年   134篇
  2004年   119篇
  2003年   115篇
  2002年   98篇
  2001年   70篇
  2000年   75篇
  1999年   75篇
  1998年   112篇
  1997年   84篇
  1996年   66篇
  1995年   58篇
  1994年   60篇
  1993年   50篇
  1992年   57篇
  1991年   23篇
  1990年   48篇
  1989年   58篇
  1988年   43篇
  1987年   57篇
  1986年   48篇
  1985年   48篇
  1984年   34篇
  1983年   27篇
  1982年   46篇
  1981年   30篇
  1980年   28篇
  1978年   31篇
  1977年   24篇
  1976年   18篇
  1975年   21篇
  1974年   18篇
  1973年   18篇
排序方式: 共有3947条查询结果,搜索用时 31 毫秒
991.
The benefits of working in a research group are clear: students develop domain expertise, gain an understanding and appreciation of the research process and its practice, and acquire team, communication, problem-solving, and higher-level thinking skills. Students with this experience are better equipped to make informed judgements about technical matters and to communicate and work in teams to solve complex problems. Clearly, this type of research experience must be made available to a broader population. This paper discusses how the Systems and Software Engineering Affinity Research Group model provides a socialization mechanism and infrastructure that supports the development and management of large research groups that engage undergraduate and graduate students, who have a wide range of skill levels and experiences, in research and projects. This non-hierarchical model, which is based on the cooperative paradigm, integrates students into small research groups and an encompassing large research group, and uses structured activities to develop their research, technical, communication, and group skills.  相似文献   
992.
The resistance of malaria parasites to available drugs continues to grow, and this makes the need for new antimalarial therapies pressing. Aminoacyl‐tRNA synthetases (ARSs) are essential enzymes and well‐established antibacterial targets and so constitute a promising set of targets for the development of new antimalarials. Despite their potential as drug targets, apicoplastic ARSs remain unexplored. We have characterized the lysylation system of Plasmodium falciparum, and designed, synthesized, and tested a set of inhibitors based on the structure of the natural substrate intermediate: lysyl‐adenylate. Here we demonstrate that selective inhibition of apicoplastic ARSs is feasible and describe new compounds that that specifically inhibit Plasmodium apicoplastic lysyl‐tRNA synthetase and show antimalarial activities in the micromolar range.  相似文献   
993.
Although most disasters are not entirely unexpected and therefore can, to varying degrees, be mitigated for, the UK construction sector does not play a sufficiently integrated role in disaster risk management. Research is reported on the development of a knowledge database and decision support framework to enable more effective disaster risk-management strategies from a construction perspective. A survey of UK professionals involved with disaster risk-management activities (i.e. emergency planning, constructing, urban planning, insurance) indicates that knowledge and awareness of integrated approaches is poor, and the construction sector as a key stakeholder and potential resource is not being used sufficiently. Key recommendations to improve the construction sector in the process are as follows: construction-related stakeholders need to become more involved in groups such as Local Resilience Teams and Forums; risk and hazard awareness training needs to be integrated systematically into the professional training of architects, planners, engineers, developers, etc.; and the construction sector should embrace and pre-empt regulatory changes regarding resilient construction requirements.

Bien que la plupart des catastrophes ne soient pas complètement inattendues et que, dans des proportions variables, elles puissent par conséquent être atténuées, l'industrie britannique du bâtiment ne s'implique pas suffisamment dans la gestion des risques de catastrophes. Il est rendu compte de recherches sur le développement d'une base de connaissances et d'un cadre de soutien à la prise de décision afin de rendre des stratégies de gestion des risques de catastrophes plus efficaces du point de vue de l'industrie du bâtiment. Une enquête auprès des professionnels britanniques impliqués dans les activités de gestion des risques de catastrophes (à savoir, planification des mesures d'urgence, construction, aménagement urbain, assurances) indique que le niveau de connaissances et de sensibilisation en matière d'approches intégrées est faible, et que le secteur du bâtiment en tant que partie prenante essentielle et ressource potentielle n'est pas suffisamment utilisé. Les principales recommandations pour améliorer le secteur du bâtiment sont les suivantes: il faut que les parties prenantes liées à l'industrie du bâtiment soient plus impliquées dans des groupes tels que les Equipes et les Forums Locaux de Résistance (Local Resilience Teams and Forums); il est nécessaire que les formations de sensibilisation aux risques et aux dangers soient systématiquement intégrées dans la formation professionnelle des architectes, des urbanistes, des ingénieurs, des promoteurs, etc., et le secteur du bâtiment devrait adopter facilement et anticiper les changements de réglementation relatifs aux obligations de résistance des constructions.

Mots clés: secteur du bâtiment, atténuation des catastrophes, plans en prévision des catastrophes, gestion des risques de catastrophes, inondations, risques naturels, résistance, Royaume-Uni  相似文献   
994.
This paper reports the results of intermatrix synthesis (IMS) of silver metal nanoparticles (Ag-MNPs) in Purolite C100E sulfonic ion exchange polymer of the gel-type structure. It has been shown that the surface morphology of the initial MNP-free polymer is absolutely smooth, but it dramatically changes after the kinetic loading of Ag on the polymer and then IMS of Ag-MNPs. These morphological changes can be explained by the interaction of Ag-NPs with the polymer chains, leading to a sort of additional cross-linking of the polymer. As a result, the modification of the gel-type matrix with Ag-MNPs leads to the increase of the matrix cross-linking, which results in the increase of its surface area and the appearance of nanoporosity in the polymer gel. Ag-MNPs are located near the polymer surface and do not form any visible agglomerations. All these features of the nanocomposites obtained are important for their practical applications in catalysis, sensor applications, and bactericide water treatment.  相似文献   
995.
996.
The evolution of the phase content in zirconia powders that have been prepared by sol—;gel acid hydrolysis has been investigated using the perturbed-angular-correlation (PAC) technique and X-ray diffractometry. As a consequence of performing annealing treatments at increasing temperatures between room temperature and 1000°C, the amorphous starting material transforms to the tetragonal form and then to the monoclinic form. The metastable tetragonal phase exhibits two hyperfine components, one of which describes very defective zirconium surroundings. The evolution of PAC relative fractions is in agreement with the diffraction results. The durability of the samples in sodium hydroxide seems to increase as the relative amount of the most-defective zirconium surroundings of the tetragonal form increases.  相似文献   
997.
998.
The authors consider instructions that courts do or could give to jurors to guide them in making awards for general damages in civil litigation. The authors review the nature and content of current instructions about the factors that should (or should not) affect jurors' awards, as well as the limited body of empirical research on the impact of these instructions. The most noteworthy feature of current instructions regarding damages is the lack of guidance they provide. The consequence appears to be awards that have considerable variability and that are influenced by improper considerations. The authors also discuss research on the effectiveness of alternative forms of jury instructions and trial procedures in preventing or reducing these problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
999.
Enterophages are a novel group of phages that specifically infect Enterococcus faecalis and have been recently isolated from environmental water samples. Although enterophages have not been conclusively linked to human fecal pollution, we are currently characterizing enterophages to propose them as viral indicators and possible surrogates of enteric viruses in recreational waters. Little is known about the morphological or genetic diversity which will have an impact on their potential as markers of human fecal contamination. In the present study we are determining if enterophages can be grouped by their ability to replicate at different temperatures, and if different groups are present in the feces of different animals. As one of the main objectives is to determine if these phages can be used as indicators of the presence of enteric viruses, the survival rate under different conditions was also determined as was their prevalence in sewage and a large watershed. Coliphages were used as a means of comparison in the prevalence and survival studies. Results indicated that the isolates are mainly DNA viruses. Their morphology as well as their ability to form viral plaques at different temperatures indicates that several groups of enterophages are present in the environment. Coliphage and enterophage concentrations throughout the watershed were lower than those of thermotolerant coliforms and enterococci. Enterophage concentrations were lower than coliphages at all sampling points. Enterophages showed diverse inactivation rates and T90 values across different incubation temperatures in both fresh and marine waters and sand. Further molecular characterization of enterophages may allow us to develop probes for the real-time detection of these alternative indicators of human fecal pollution.  相似文献   
1000.
Many proteins have a multimeric structure and are composed of two or more identical subunits. While this can be advantageous for the host organism, it can be a challenge when targeting specific residues in biochemical analyses. In vitro splitting and re-dimerization to circumvent this problem is a tedious process that requires stable proteins. We present an in vivo approach to transform homodimeric proteins into apparent heterodimers, which then can be purified using two-step affinity-tag purification. This opens the door to both practical applications such as smFRET to probe the conformational dynamics of homooligomeric proteins and fundamental research into the mechanism of protein multimerization, which is largely unexplored for membrane proteins. We show that expression conditions are key for the formation of heterodimers and that the order of the differential purification and reconstitution of the protein into nanodiscs is important for a functional ABC-transporter complex.  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