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   6627篇
  免费   234篇
  国内免费   7篇
电工技术   66篇
综合类   2篇
化学工业   1086篇
金属工艺   140篇
机械仪表   130篇
建筑科学   296篇
矿业工程   21篇
能源动力   147篇
轻工业   456篇
水利工程   72篇
石油天然气   35篇
无线电   538篇
一般工业技术   1150篇
冶金工业   1803篇
原子能技术   34篇
自动化技术   892篇
  2023年   48篇
  2022年   80篇
  2021年   132篇
  2020年   90篇
  2019年   106篇
  2018年   114篇
  2017年   109篇
  2016年   107篇
  2015年   112篇
  2014年   173篇
  2013年   361篇
  2012年   277篇
  2011年   341篇
  2010年   214篇
  2009年   204篇
  2008年   257篇
  2007年   256篇
  2006年   227篇
  2005年   163篇
  2004年   160篇
  2003年   171篇
  2002年   137篇
  2001年   103篇
  2000年   102篇
  1999年   123篇
  1998年   406篇
  1997年   272篇
  1996年   182篇
  1995年   129篇
  1994年   113篇
  1993年   128篇
  1992年   85篇
  1991年   68篇
  1990年   81篇
  1989年   80篇
  1988年   81篇
  1987年   76篇
  1986年   53篇
  1985年   73篇
  1984年   51篇
  1983年   47篇
  1982年   50篇
  1981年   58篇
  1980年   52篇
  1979年   51篇
  1978年   52篇
  1977年   74篇
  1976年   83篇
  1975年   45篇
  1973年   41篇
排序方式: 共有6868条查询结果,搜索用时 46 毫秒
71.
A method for machine interpretation of architectural (or other) schematic drawings is presented. The central problem is to build an efficient drawing parser (i.e., a program that identifies the semantic entities, characteristics, and relationships that are represented in the drawing). The parser is built from specifications of the drawing grammar and an underlying spatial model. The grammar describes what to look for, and the spatial model enables the parser to find it quickly. Coupled with existing optical recognition technology, this technique enables the use of drawings directly as: (1) a database to drive various Architecture-Engineering-Construction (AEC) applications; (2) a communication protocol to integrate CAD systems; (3) a traditional user interface.  相似文献   
72.
Evaluated the efficacy of outpatient group treatment of chronic pain and the effect of spouse involvement in treatment in chronic pain patients ranging in age from 23 to 69 yrs who were randomly assigned to couples group treatment (n?=?17), patient-only group treatment (n?=?14), or waiting-list controls (n?=?12). 29 Ss had low back pain; the remaining Ss reported pain in the knee, arm, leg, hip, head, and phantom limb. The Ss completed the MMPI—168 and measures of health-related psychosocial and physical dysfunction and marital satisfaction. Results indicate that the 16-hr cognitive-behavioral program produced reductions in pain, somatization, spouse-observed pain behavior, physical and psychosocial dysfunction, spouse-rated dysfunction, and utilization of health care resources. Depression was not affected by treatment. Spouse involvement did not facilitate response to treatment on any variables. Also, Ss in the individual condition only showed improved marital satisfaction. All treatment gains were maintained at 3-mo to 7-mo follow-ups. Results indicate that brief outpatient treatment can significantly ameliorate chronic pain problems, and spouse involvement is not essential for a positive response to treatment. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
73.
74.
When Bonner & Moore was formed in 1956, few-if any-other firms were offering computer consulting services to private industry. Over the years, Bonner & Moore's software development and computer modeling projects took the company far and wide, from Texas oil refineries to the other side of the globe. Its computer services created a solid financial success.  相似文献   
75.
76.
77.
This paper documents the first of the two interrelated studies that were conducted to more fundamentally understand the scalability of flame heat flux, the motivation being that it has been reported that flame heat flux back to the burning surface in bench‐scale experiments is not the same as for large‐scale fires. The key aspect was the use of real scale applied heat flux up to 200kW/m2 which is well beyond that typically considered in contemporary testing. The main conclusions are that decomposition kinetics needs to be included in the study of ignition and the energy balance for steady burning is too simplistic to represent the physics occurring. An unexpected non‐linear trend is observed in the typical plotting methods currently used in fire protection engineering for ignition and mass loss flux data for several materials tested and this non‐linearity is a true material response. Using measured temperature profiles in the condensed phase shows that viewing ignition as an inert material process is inaccurate at predicting the surface temperature at higher heat fluxes. The steady burning temperature profiles appear to be invariant with applied heat flux. This possible inaccuracy was investigated by obtaining the heat of gasification via the ‘typical technique’ using the mass loss flux data and comparing it to the commonly considered ‘fundamental’ value obtained from differential scanning calorimetry measurements. This comparison suggests that the ‘typical technique’ energy balance is too simplified to represent the physics occurring for any range of applied heat flux. Observed bubbling and melting phenomena provide a possible direction of study. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
78.
Bench-scale reactor experiments were performed to study the dissolution of a binary naphthalene-in-nonane mixture nonaqueous phase liquid (NAPL) pool over a wide range of average pore water velocities, vx (≈0.1–60 m/day). Experimental NAPL pool dissolution flux values were determined using a steady-state mass balance approach. The experimental flux data were compared to model predictions made assuming either local equilibrium or mass-transfer limited conditions. The local equilibrium model could describe the trends in the average effluent concentration and dissolution flux with 0.110?m/day. Data determined to be under mass-transfer limited conditions were fit to the nonequilibrium model to estimate values for an overall mass-transfer coefficient. The calculated overall mass-transfer coefficients had an average value of 0.407 m/day and showed no correlation with vx, probably due to mass-transfer resistance becoming dominated by the diffusional resistance in the NAPL. These results suggest that the nonequilibrium approach is better suited for describing high velocity (vx>10?m/day) dissolution of multicomponent NAPL pools, and that flushing of groundwater at very high velocities may not be an effective approach for enhancing NAPL-pool dissolution flux.  相似文献   
79.
80.
In this study we investigated changes to horizontal cells in human retinae affected by glaucoma. Glaucoma is characterized by raised intraocular pressure and is responsible for retinal ganglion cell and, possibly, photoreceptor degeneration. It was therefore assumed that horizontal cells might also be affected. The carbocyanine dye DiI was placed at discrete points on fixed, whole-mounted retinae obtained from normal and glaucomatous patients. After allowing 6-24 weeks for intramembranous diffusion within the lipid layers of the nerve cells and, therefore, fluorescent labeling, we measured horizontal cell soma and dendritic field sizes. Selected cells were then embedded in Araldite and cut at 4 microns. Horizontal cells in glaucomatous eyes appeared larger and had a granulated outline as compared with cells from normal retinae. Analysis of the mean cell soma size indicated that cells were 26% larger in the glaucomatous retinae and that this increase was significantly different from that seen in normal retinae (P < 0.05). The dendritic field size was unaffected (P > 0.05). As seen in cross section there was a clear loss of photoreceptor outer segments, and shrunken silhouettes of photoreceptor inner segments with pyknotic nuclei were observed. It is proposed that the increase in some size is indicative of horizontal cell responses that are likely to culminate in degeneration as a result of heightened intraocular pressure. In addition, this paper provides further evidence that photoreceptors are affected by advanced glaucoma.  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