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   18354篇
  免费   709篇
  国内免费   22篇
电工技术   217篇
综合类   18篇
化学工业   3802篇
金属工艺   345篇
机械仪表   406篇
建筑科学   1007篇
矿业工程   49篇
能源动力   505篇
轻工业   1679篇
水利工程   121篇
石油天然气   57篇
武器工业   1篇
无线电   1631篇
一般工业技术   3099篇
冶金工业   3074篇
原子能技术   189篇
自动化技术   2885篇
  2023年   159篇
  2022年   297篇
  2021年   463篇
  2020年   346篇
  2019年   367篇
  2018年   425篇
  2017年   393篇
  2016年   497篇
  2015年   426篇
  2014年   523篇
  2013年   1085篇
  2012年   865篇
  2011年   1123篇
  2010年   771篇
  2009年   829篇
  2008年   875篇
  2007年   762篇
  2006年   717篇
  2005年   595篇
  2004年   495篇
  2003年   442篇
  2002年   426篇
  2001年   303篇
  2000年   325篇
  1999年   354篇
  1998年   750篇
  1997年   487篇
  1996年   402篇
  1995年   294篇
  1994年   271篇
  1993年   269篇
  1992年   183篇
  1991年   156篇
  1990年   137篇
  1989年   139篇
  1988年   126篇
  1987年   117篇
  1986年   120篇
  1985年   141篇
  1984年   136篇
  1983年   116篇
  1982年   92篇
  1981年   104篇
  1980年   88篇
  1979年   100篇
  1978年   87篇
  1977年   117篇
  1976年   139篇
  1975年   83篇
  1974年   72篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A molecular model of the binding site of an anti-carbohydrateantibody (YsT9.1) has been developed using computer-assistedmodeling techniques and molecular dynamics calculations. Sequencehomologies among YsT9.1 and the Fv regions of McPC603, J539and human Bence-Jones protein REI, all of which have solvedcrystal structures, provided the basis for the modeling. Thegroove-type combining site model had a topography which wascomplementary to low energy confonners of the polysaccharide,a Brucella O-antigen, and the site could be almost completelyfilled by a pentasaccharide epitope in either of two dockingmodes. Putative interactions between this epitope and the antibodyare consistent with the known structural requirements for bindingand lead to the design of oligosaccharide inhibitors that probethe veracity of the modeled docked complex. Ultimately boththe Fv model and the docked complex will be compared with independentcrystal structures of YsT9.1 Fab with and without pentasaccharideinhibitor, currently at the stage of refinement.  相似文献   
52.
53.
Liu  Xinke  Kao  Evan  Haraldsson  Henrik  Ballweber  Megan  Martin  Alastair  Li  Youxiang  Wang  Yuting  Saloner  David 《Magma (New York, N.Y.)》2021,34(5):659-666
Magnetic Resonance Materials in Physics, Biology and Medicine - To determine the intra-individual flow variation in serially acquired studies, and the influence of this variation on subsequent...  相似文献   
54.
Corrosion of oil-fired domestic boilers Depending on the surface temperature of the flue gas side the corrosion of oil fired domestic boilers proceeds either mainly by acid corrosion or by oxygen corrosion:
  • – At surface temperatures of 60°C and higher the corrosion mechanism of acid corrosion prevails and the corrosion rates amount to 0.1–0.3 mm/year (values referred to continuous burner operation). The corrosion products consist of soluble iron(II)- and iron(III)sulfates. Higher corrosion rates can be attributed to an appreciable catalytic formation of sulfur trioxide on the corrosion products formed on the convective heating surfaces.
  • – At surface temperatures of 40°C the mechanism of oxygen corrosion already dominates and the corrosion rates are about ten times higher (1.5–3 mm/year, referred to continous burner operation). The high portion of ioron oxide hydrates, especially goethit (α-FeOOH), makes the corrosion products difficult to remove.
  • – Distinctly reduced service lives are also expected for the so called reduced temperature boilers (“Niedertemperaturkessel”) and low temperature boiers (“Tieftemperaturkessel”): According to the manufacturers these boilers may be operated at boiler water temperatures well below 60°C, as they are equipped with constructive measures to enhance the surface temperature on the flue gas side. However, these measures are only fully effective under stationary conditions.
Some of the results were obtained from weight loss measurements on test specimen made from St 35.8 and gray cast iron, that were exposed to the flue gases of an oil fired experimental boiler. Other important results come from field measurements of the sulfuric acid content of about 30 boilers that are in practical use.  相似文献   
55.
The effects of heat treatments on the mechanical and fracture properties of continuous fiber Pitch 100 graphite/6061 aluminum (P100 Gr/6061 Al) composite were evaluated by varying solution temperature and aging time. All heat treatments resulted in decreased mechanical properties due to the reaction at the fiber/matrix interface during solution treatments. SEM analysis of the fractured samples showed a large degree of fiber pullout, interface failure, and matrix cracking.  相似文献   
56.
Programmers build large‐scale systems with multiple languages to leverage legacy code and languages best suited to their problems. For instance, the same program may use Java for ease of programming and C to interface with the operating system. These programs pose significant debugging challenges, because programmers need to understand and control code across languages, which often execute in different environments. Unfortunately, traditional multilingual debuggers require a single execution environment. This paper presents a novel composition approach to building portable mixed‐environment debuggers, in which an intermediate agent interposes on language transitions, controlling and reusing single‐environment debuggers. We implement debugger composition in Blink, a debugger for Java, C, and the Jeannie programming language. We show that Blink is (i) simple: it requires modest amounts of new code; (ii) portable: it supports multiple Java virtual machines, C compilers, operating systems, and component debuggers; and (iii) powerful: composition eases debugging, while supporting new mixed‐language expression evaluation and Java native interface bug diagnostics. To demonstrate the generality of interposition, we build prototypes and demonstrate debugger language transitions with C for five of six other languages (Caml, Common Lisp, C#, Perl 5, Python, and Ruby) without modifications to their debuggers. Using real‐world case studies, we show that diagnosing language interface errors require prior single‐environment debuggers to restart execution multiple times, whereas Blink directly diagnoses them with one execution. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
57.
We describe the architecture of an original biofeedback system for balance improvement for fall prevention and present results of a feasibility study. The underlying principle of this biofeedback consists of providing supplementary information related to foot sole pressure distribution through a wireless embedded tongue-placed tactile output device.Twelve young healthy adults voluntarily participated in this experiment. They were asked to stand as immobile as possible with their eyes closed in two conditions of no-biofeedback and biofeedback. Centre of foot pressure (CoP) displacements were recorded using a force platform. Results showed reduced CoP displacements in the biofeedback relative to the no-biofeedback condition.On the whole, the present findings evidence the effectiveness of this system in improving postural control on young healthy adults. Further investigations are needed to strengthen the potential clinical value of this device.  相似文献   
58.
59.
60.
Martin PA  Guelachvili G 《Applied optics》1996,35(36):7066-7069
A new method to detect molecular ions selectively in gas discharges by Fourier transform emission spectroscopy is proposed. This method is by dual-beam optical subtraction. The difference spectrum between blue and red Doppler-shifted components is obtained directly thus eliminating the large background that is due to neutral precursors.  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