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   2413篇
  免费   10篇
  国内免费   4篇
电工技术   35篇
化学工业   82篇
金属工艺   9篇
机械仪表   13篇
建筑科学   19篇
矿业工程   1篇
能源动力   18篇
轻工业   23篇
水利工程   10篇
石油天然气   3篇
无线电   47篇
一般工业技术   90篇
冶金工业   1975篇
原子能技术   15篇
自动化技术   87篇
  2021年   8篇
  2019年   4篇
  2018年   7篇
  2017年   8篇
  2016年   4篇
  2014年   8篇
  2013年   40篇
  2012年   15篇
  2011年   12篇
  2010年   10篇
  2009年   19篇
  2008年   16篇
  2007年   20篇
  2006年   28篇
  2005年   25篇
  2004年   27篇
  2003年   22篇
  2002年   21篇
  2001年   16篇
  2000年   18篇
  1999年   60篇
  1998年   637篇
  1997年   340篇
  1996年   248篇
  1995年   116篇
  1994年   104篇
  1993年   111篇
  1992年   24篇
  1991年   27篇
  1990年   30篇
  1989年   41篇
  1988年   34篇
  1987年   23篇
  1986年   30篇
  1985年   36篇
  1984年   6篇
  1983年   5篇
  1982年   13篇
  1981年   8篇
  1980年   23篇
  1979年   5篇
  1978年   9篇
  1977年   36篇
  1976年   78篇
  1975年   8篇
  1974年   7篇
  1955年   3篇
  1923年   3篇
  1922年   3篇
  1921年   3篇
排序方式: 共有2427条查询结果,搜索用时 15 毫秒
1.
Antibiotic resistance is a growing problem for public health and associated with increasing economic costs and mortality rates. Silver and silver-related compounds have been used for centuries due to their antimicrobial properties. In this work, we show that 1,3-dibenzyl-4,5-diphenyl-imidazol-2-ylidene silver(I) acetate/NHC*-Ag-OAc (SBC3) is a reversible, high affinity inhibitor of E. coli thioredoxin reductase (TrxR; Ki=10.8±1.2 nM). Minimal inhibition concentration (MIC) tests with different E. coli and P. aeruginosa strains demonstrated that SBC3 can efficiently inhibit bacterial cell growth, especially in combination with established antibiotics like gentamicin. Our results show that SBC3 is a promising antibiotic drug candidate targeting bacterial TrxR.  相似文献   
2.
This paper extends an analysis developed for tubular permanent-magnet machines to account for the effect of fringing associated with the finite length of the ferromagnetic armature core. The magnetic field distribution, established by using an analytical technique formulated in the cylindrical coordinate system, provides an accurate means of evaluating the effect of the fringing flux on the thrust force and the back-electromotive force. Finite-element calculations confirm the analytically derived results. In Part II of the paper, the analysis is used to predict the cogging force that results from end effects and to facilitate minimization of the force.  相似文献   
3.
Test Case Generation as an AI Planning Problem   总被引:6,自引:0,他引:6  
While Artificial Intelligence techniques have been applied to a variety of software engineering applications, the area of automated software testing remains largely unexplored. Yet, test cases for certain types of systems (e.g., those with command language interfaces and transaction based systems) are similar to plans. We have exploited this similarity by constructing an automated test case generator with an AI planning system at its core. We compared the functionality and output of two systems, one based on Software Engineering techniques and the other on planning, for a real application: the StorageTek robot tape library command language. From this, we showed that AI planning is a viable technique for test case generation and that the two approaches are complementary in their capabilities.  相似文献   
4.
5.
6.
The equilibrium shape and dihedral angles at the solid–liquid–vapor tri-junctions of two-phase alloy small particles containing a cusp-oriented interface were modeled as a function of phase fraction, surface energy and the interfacial energy. The calculation was applied to different combinations of surface and/or interfacial energies to demonstrate the various possible particle shapes and dihedral angles that result for two-phase particles. The dihedral angles at the tri-junction vary with the phase fraction, due to the coupling between the relative amounts of each phase, interfacial energy relative to the two surface energies and the equilibrium conditions at the tri-junction. These features can be used to find the ratio of the interfacial energy to the surface energies of two-phase particles for any state of matter.  相似文献   
7.
In this paper we deduce, from analytical field solutions, the influence of leading design parameters on the performance of a radially magnetized, iron-cored, tubular permanent-magnet machine and its drive system. We derive analytical formulas for predicting the open-circuit electromotive force, the thrust force, the iron loss, and the winding resistance and inductances, as well as the converter losses. The force density, the machine and drive system efficiencies, and the power factor and converter volt-ampere (VA) rating are established as functions of a set of machine dimensional ratios, with due account of magnetic saturation and subject to a specified thermal constraint. We validate the utility and accuracy of the analytically derived formulas by finite-element calculations. Finally, we show that the design optimization of such a linear drive system must account for the losses and VA rating of the converter as well as the design parameters of the tubular machine.  相似文献   
8.
Plant seeds store triacylglycerols as energy sources for germination and postgerminative growth of seedlings. The triacylglycerols are preserved in small, discrete, intracellular organelles called oil bodies. A new method was developed to purify seed oil bodies. The method included extraction, flotation by centrifugation, detergent washing, ionic elution, treatment with a chaotropic agent, and integrity testing by use of hexane. These processes subsequently removed non-specifically associated or trapped proteins within the oil bodies. Oil bodies purified by this method maintained their integrity and displayed electrostatic repulsion and steric hindrance on their surface. Compared with the previous procedure, this method allowed higher purification of oil bodies, as demonstrated by SDS-PAGE using five species of oilseeds. Oil bodies purified from sesame were further analyzed by two-dimensional gel electrophoresis and revealed two potential oleosin isoforms. The integrity of oil bodies in germinating sesame seedlings was examined by hexane extraction. Our results indicated that consumption of triacylglycerols reduced gradually the total amount of oil bodies in seedlings, whereas no alteration was observed in the integrity of remaining oil bodies. This observation implies that oil bodies in germinating seeds are not degraded simultaneously. It is suggested that glyoxisomes, with the assistance of mitochondria, fuse and digest oil bodies one at a time, while the remaining oil bodies are preserved intact during the whole period of germination.  相似文献   
9.
A 78-year-old Chinese woman presented with recurrent postprandial abdominal pain. Computerised tomography revealed a small bowel tumour causing volvulus of a segment of the small bowel. Laparotomy confirmed an extraluminal ileal tumour with partial volvulus of the involved small bowel segment. Small bowel resection was done. Histological and ultrastructural studies confirmed a gastrointestinal autonomic nerve tumour. We review the medical literature on this rare tumour.  相似文献   
10.
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