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   2560篇
  免费   195篇
  国内免费   5篇
电工技术   37篇
综合类   1篇
化学工业   675篇
金属工艺   51篇
机械仪表   46篇
建筑科学   68篇
矿业工程   4篇
能源动力   90篇
轻工业   245篇
水利工程   21篇
石油天然气   2篇
无线电   230篇
一般工业技术   540篇
冶金工业   142篇
原子能技术   18篇
自动化技术   590篇
  2024年   5篇
  2023年   39篇
  2022年   83篇
  2021年   113篇
  2020年   85篇
  2019年   77篇
  2018年   80篇
  2017年   84篇
  2016年   108篇
  2015年   94篇
  2014年   123篇
  2013年   170篇
  2012年   204篇
  2011年   229篇
  2010年   171篇
  2009年   149篇
  2008年   153篇
  2007年   127篇
  2006年   127篇
  2005年   79篇
  2004年   72篇
  2003年   60篇
  2002年   42篇
  2001年   25篇
  2000年   20篇
  1999年   23篇
  1998年   44篇
  1997年   31篇
  1996年   16篇
  1995年   14篇
  1994年   15篇
  1993年   18篇
  1992年   5篇
  1991年   15篇
  1990年   4篇
  1989年   3篇
  1988年   3篇
  1987年   6篇
  1986年   4篇
  1985年   5篇
  1984年   4篇
  1983年   5篇
  1982年   5篇
  1981年   5篇
  1979年   6篇
  1975年   3篇
  1972年   1篇
  1971年   1篇
  1967年   1篇
  1931年   1篇
排序方式: 共有2760条查询结果,搜索用时 15 毫秒
991.
The synthesis, crystal structure, electrochemical and optical properties of a novel blue emitting ladder pentaphenylene are reported and compared with those of its 3π−2 spiro parent, in order to study the effect of the spiro-linked fluorene rings. Anodic oxidation of the novel compound results via electropolymerization, in the formation of an electroactive material that displays interesting electrochemical and optical properties.  相似文献   
992.
Gastrointestinal bleeding caused by erosion of a pancreaticoduodenal artery aneurysm in patients with pancreatitis is a rare but potentially life threatening disease. In this case report, the successful treatment of a patient bleeding from a ruptured pancreaticoduodenal artery aneurysm is described. A review of the literature of reported cases discusses the value of early angiographic intervention in patients with unexplained gastrointestinal hemorrhage and suspected rupture of an aneurysm.  相似文献   
993.
Verification of Real-Time Systems using Linear Relation Analysis   总被引:3,自引:2,他引:1  
Linear Relation Analysis [11] is an abstract interpretation devoted to the automatic discovery of invariant linear inequalities among numerical variables of a program. In this paper, we apply such an analysis to the verification of quantitative time properties of two kinds of systems: synchronous programs and linear hybrid systems.  相似文献   
994.
The authors are concerned with the comparative analysis of interactive processes in a meeting, subject to various situations of mediation. The research is based on the analysis of records of actual meetings, either in face to face situations, or in audio or video-conferences. Interactivity is first defined as the ability to interrupt in order to help the communication process. The mechanisms which regulate this interactivity are then analyzed, as well as its functions in the way exchanges proceed and speech is built. The thesis is put forward that parallel to the exchange of informations linked to the contents of the meeting, an exchange of control signals, chiefly of an infra and non verbal kind, takes place as on a signalling channel, the role of which is to regulate: the allocation of speech turn-taking, the mutual understanding of participants, the setting out of the speech issued on the main channel, the construction of the common knowledge useful to the achievement of the task, the regulation of speech status, the production of ambiguous and unopposable speeches… The study enables identification of the disturbances brought to the regulation of interactivity when the technical conditions of mediation do change, and allows improvement of the designing of the protocoles aimed at selecting voice and image data before their transmission through teleconferencing systems.  相似文献   
995.
Dendrotoxin I (DTX-I) is a 60-residue peptide from the venom of the black mamba snake Dendroaspis polylepis, which binds to neuronal K+ channels. The structure reported previously for DTX-I was synthesized for the first time by a solution procedure. The synthetic product was confirmed to have the correct primary and disulfide structure determined by peptide mapping, sequence analysis and mass measurements. Comparison of synthetic DTX-I with the natural one by high-performance liquid chromatography and capillary zone electrophoresis, as well as by sequence analysis, revealed that the Asn residue at position 12 in the synthetic peptide was Asp in the natural product. Synthesis of DTX-I with Asp at position 12 gave a peptide identical with the natural product in all aspects. NMR analysis of synthetic [Asn12]- and [Asp12]-DTX-I also supported our findings that the Asn residue at position 12 in the DTX-I molecule should be revised as Asp. [Asn12]- and [Asp12]-DTX-I had very similar binding affinities when tested against radiolabeled dendrotoxin binding to rat brain synaptosomal membranes.  相似文献   
996.
Tetrahydro-2-pyranyl ethers from fatty primary alcohols can be converted in a one-step procedure into the corresponding carboxylic acids in high yields. This process avoids the synthesis of symmetrical esters, particularly for long-chain compounds. This reaction proved to be useful, for instance, to produce polyunsaturated fatty acids immediately before their biological testing.  相似文献   
997.
A new tomographic process measures the spatial phase fractions in slug flow and possesses high positional and temporal resolution. The measuring method is based on the electrical conductivity of the flowing fluids, which is measured between numerous parallel wires. The individual measurements are directly proportional to the relative liquid content. With the aid of an iterative reconstruction procedure they permit calculation of the phase fractions. The quality of reconstruction is improved by consideration of a priori knowledge. The temporal resolution is 0.009 s and the spatial resolution less than 0.1% of the flow cross-section.  相似文献   
998.
At the beginning of the 20th century, Alfred Binet sought teaching positions at the Colfte de France and the Sorbonne. Binet wanted to develop experimental psychology in France, but the strong psychopathological orientation of French psychology blocked his ambition. The 1st part of this article relates the history of the introduction of psychology, via Théodule Ribot, to the Sorbonne and the Coll6ge de France. Ribot's premature retirement from the Collège de France in 1901 triggered a battle that led to Binet's repeated failure to gain access to these institutions of higher education and the success in 1902 of Ribot's students: Pierre Janet at the Colfte de France and Georges Dumas at the Sorbonne. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
999.
(Bi1-xSbx)2Te3 thermoelectric thin films were deposited on stainless steel discs in 1 M perchloric acid and 0.1 M tartaric acid by pulse electrodeposition in order to optimize the grain growth. The influence of the electrolyte composition, the cathodic current density and the cathodic pulse time on film stoichiometry were studied. The results show that it is necessary to increase the Sb content in the electrolyte to obtain the (Bi0.25Sb0.75)2Te3 film stoichiometry. Pulse plating reduced the grain size and the roughness, compared with continuous plating. Thermoelectric and electrical properties were also studied and it was found that the Seebeck coefficient and electrical resistivity were related to two parameters: the cathodic pulse current density and the films thickness.  相似文献   
1000.
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