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   1103篇
  免费   24篇
  国内免费   3篇
电工技术   71篇
化学工业   291篇
金属工艺   34篇
机械仪表   19篇
建筑科学   15篇
能源动力   18篇
轻工业   74篇
水利工程   4篇
石油天然气   7篇
无线电   97篇
一般工业技术   163篇
冶金工业   193篇
原子能技术   40篇
自动化技术   104篇
  2023年   5篇
  2022年   20篇
  2021年   21篇
  2020年   13篇
  2019年   6篇
  2018年   19篇
  2017年   14篇
  2016年   23篇
  2015年   9篇
  2014年   27篇
  2013年   48篇
  2012年   33篇
  2011年   50篇
  2010年   37篇
  2009年   34篇
  2008年   36篇
  2007年   54篇
  2006年   26篇
  2005年   43篇
  2004年   32篇
  2003年   33篇
  2002年   26篇
  2001年   32篇
  2000年   24篇
  1999年   32篇
  1998年   76篇
  1997年   58篇
  1996年   40篇
  1995年   31篇
  1994年   30篇
  1993年   32篇
  1992年   10篇
  1991年   11篇
  1990年   16篇
  1989年   12篇
  1988年   14篇
  1987年   9篇
  1986年   11篇
  1985年   7篇
  1984年   16篇
  1983年   8篇
  1982年   5篇
  1981年   13篇
  1980年   6篇
  1979年   9篇
  1978年   2篇
  1977年   4篇
  1976年   5篇
  1975年   2篇
  1973年   2篇
排序方式: 共有1130条查询结果,搜索用时 15 毫秒
91.
BACKGROUND: Follow-up study of patients with surgical repair of aneurysmal subarachnoidal hemorrhage (SAH), looking for clinical outcome predictors. PATIENTS AND METHODS: Sixty two patients consecutively admitted to a teaching hospital, from January 1992 to December 1995 were included in the study. We studied preoperative, intraoperative and postoperative features looking for their relationship with the outcome. The ultimate outcome was evaluated by means of Glasgow Outcome Scale on discharge and 6 months later. RESULTS: Smoking (p = 0.0001) and arterial hypertension (AHT) (p = 0.0186) were more frequent in these patients than in general population, but without relationship to the outcome as with the age of the clinical status on admission. The greatest statistical relationship was found between the level of consciousness on postoperative awakening (measured by the Hunt and Hess scale), and the outcome (p = 2.53 x 10(-8). From our results we made an algorithm that correctly assigned 92% of studied patients to their outcome. CONCLUSIONS: All patients admitted on with aneurysm SAH deserve intensive care treatment besides their clinical grade. The level of consciousness on postoperative awakening was a good outcome predictor.  相似文献   
92.
A new single-chip microprocessor for speech recognition, the SRP, has been developed, utilizing a multiprocessor architecture and a pipelined structure. It can recognize up to 340 isolated words or 40 connected words in real time. The SRP contains a vector distance calculator, a DP-equation calculator, and an I/O controller operating in a pipelined manner. Algorithm variations and operation parameters are user programmable, and the total size of the SRP program for a typical speech recognition system is about 700 words. The device has been fabricated with n-channel Si-gate E/D MOS technology with 2.5 μm design rules and employs 7296 three-transistor dynamic RAM cells for a total of more than 40 000 transistors.  相似文献   
93.
A cold storage system specialized in mobile high-temperature superconducting (HTS) magnets (e.g. for magnetically levitated (maglev) vehicles) has been proposed. In this system, a cooling source is detachable and a HTS coil is capable of maintaining superconducting state with its heat capacity. This system allows a considerably lightweight HTS magnet.An apparatus was constructed to evaluate the possibility of using cold storage systems in maglev vehicles. The thermal characteristic of this apparatus was based on a magnet for previous maglev test vehicles [1]. The operational temperature range of the magnet was assumed from 20 K to 50 K. Some experiments indicated that heat conduction by residual gas was not negligible. Especially over 30 K, gas conduction took a large part of heat input. This phenomenon is attributable to reduction of cryopumping effect. However, activated carbon in the apparatus compensates cryopumping effect. A unique heat capacitor was also used to enhance the cold storage effect. Water ice was chosen as a heat capacitor because water ice has a higher heat capacity than metallic materials at cryogenic temperatures. A small amount of water ice also prolonged cryogenic temperature condition. These results indicate 1 day of cold storage is probable in a magnet for maglev vehicles.  相似文献   
94.
95.
96.
ARTS: Accelerated Ray-Tracing System   总被引:14,自引:0,他引:14  
In this article we propose algorithms that address the two basic problems encountered in generating continuous-tone images by ray tracing: speed and aliasing. We examine previous approaches to the problem and then propose a scheme based on the coherency of an auxiliary data structure imposed on the original object domain. After investigating both simple spatial enumeration and a hybrid octree approach, we developed 3DDDA, a 3D line generator for efficient traversing of both structures. 3DDDA provides an order of magnitude improvement in processing speed compared to other known ray-tracing methods. Processing time is found to be virtually independent of the number of objects involved in the scene. For large numbers of objects, this method actully becomes faster than scan-line methods. To remove jags from edges, a scheme for identifying edge orientation and distance from pixel center to true edge has been implemented. The time required for antialiasing depends on the total length of the edges encountered, but it is normally only a fractional addition to the time needed to produce the scene without antialiasing.  相似文献   
97.
98.
We present a novel thin-sheet X-cut LiNbO/sub 3/ optical modulator structure which can be fabricated by precise polishing and lapping to obtain a thinner LiNbO/sub 3/ substrate for a lower driving voltage in addition to velocity matching and impedance matching. We demonstrated that the fabricated modulator had a driving voltage V/spl pi/ of 2 V and zero chirp for 40-Gb/s operation and had a high potential for suppressed dc drift, and long-term reliability.  相似文献   
99.
Summary Poly(dithiafulvene)s having alkoxy group and mesogenic moiety in the side chain were prepared by cycloaddition polymerization. The effects of the side chains on the structural and optical properties of poly(dithiafulvene)s in solution were investigated. Furthermore, the film state properties of the polymers and their charge transfer complex with electron acceptor were studied before and after annealing.  相似文献   
100.
Morphological changes of solution-grown crystals (SGCs) of poly(l-lactide) (PLLA) following thermal treatment and enzymatic degradation were investigated using atomic force microscopy in terms of defects in the crystals. PLLA SGCs were grown from a dilute solution of acetonitrile at 5 °C. The obtained solution-grown monolamellar crystals have a lozenge-shaped morphology containing unique dimensions, with one side measuring 12 μm. To investigate enzymatic degradation behavior, PLLA SGCs were incubated in buffered solution with proteinase-K at 37 °C. The initial stage of enzymatic degradation of PLLA SGCs with proteinase-K occurs in loosely folding chains at the surface of the crystal. Thermally treated PLLA SGCs below the melting temperature showed an increase of the lamellar thickness of the SGCs at the treated temperature and partial surface erosion following enzyme exposure. These results indicate that less ordered chains exist throughout the lamellae and their thermal-induced chain extension makes them more susceptible to enzyme attack.  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