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   2129篇
  免费   28篇
电工技术   37篇
综合类   2篇
化学工业   186篇
金属工艺   29篇
机械仪表   49篇
建筑科学   104篇
矿业工程   5篇
能源动力   44篇
轻工业   151篇
水利工程   32篇
石油天然气   9篇
无线电   152篇
一般工业技术   267篇
冶金工业   810篇
原子能技术   22篇
自动化技术   258篇
  2021年   17篇
  2020年   12篇
  2019年   16篇
  2018年   17篇
  2017年   16篇
  2016年   17篇
  2015年   21篇
  2014年   37篇
  2013年   119篇
  2012年   43篇
  2011年   60篇
  2010年   44篇
  2009年   42篇
  2008年   53篇
  2007年   71篇
  2006年   66篇
  2005年   60篇
  2004年   56篇
  2003年   41篇
  2002年   62篇
  2001年   36篇
  2000年   38篇
  1999年   53篇
  1998年   184篇
  1997年   134篇
  1996年   102篇
  1995年   69篇
  1994年   54篇
  1993年   50篇
  1992年   38篇
  1991年   30篇
  1990年   30篇
  1989年   41篇
  1988年   34篇
  1987年   23篇
  1986年   25篇
  1985年   35篇
  1984年   16篇
  1983年   20篇
  1982年   25篇
  1981年   30篇
  1980年   18篇
  1979年   15篇
  1978年   14篇
  1977年   37篇
  1976年   37篇
  1974年   9篇
  1973年   15篇
  1972年   14篇
  1971年   9篇
排序方式: 共有2157条查询结果,搜索用时 15 毫秒
71.
Attempted to determine whether the Reitan-Halstead Organic Test Battery separates neuropsychiatric hospital organics from schizophrenics. It was administered to 25 schizophrenics and 25 cerebral-lesion organics at each of 2 chronicity levels. Only 1 of the 24 diagnosis/diagnosis * chronicity effects used to evaluate the data was significant at the .05 level, indicating that actuarial application of Reitan-Halstead scores is of no practical value in the separation of the 2 groups. To determine whether expert clinicians might improve upon the actuarial results, protocols of 24 schizophrenics and 24 organics were sent to 8 Reitan-Halstead experts who were instructed to separate them into brain-damaged and schizophrenic diagnostic groups. The mean number of correct classifications, 25.5 out of 48 suggested that clinical judgment added nothing to actuarial prediction in this case. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
72.
Eighty-four geriatirc ward patients were randomly assigned to groups targeted for outplacement planning or inpatient care. During the following year, half of the former were placed in community settings while nearly all of the latter remained in the hospital. Neither the physical health, level of self-care, or psychiatric condition ratings of the two groups changed differentially over that time. However, the mean Morale Inventory score of the outplacement sample improved while that of the in-patient group remained static. Additional analyses were run between three groups - outplacement planning subjects who were released, those who were not released, and inpatient planning men who were not released. These results confirmed those of the first analyses; the only significant difference appeared on the Morale Inventory, the patients who left showing more improvement than the other two groups. The results argue for an increased emphasis on outplacement programs among geriatric patients.  相似文献   
73.
Measurements of linear cross polarization and attenuation on a terrestrial link in the U.K. are reported and correlated with rainfall information. The cross polarization measured during rainfall is compared with theoretically predicted values and monthly cross-polar statistics are presented for a 16-month period.  相似文献   
74.
Attenuation and phase coefficients are evaluated for microwave radio propagation through oblate spheroidal raindrops on slant radio paths. From these coefficients, it is evident that the resultant crosspolarisation for linearly or circularly polarised waves should be significantly less on satellite radio paths than on horizontal radio paths.  相似文献   
75.
The field equations of three-dimensional elastostatics are transformed to boundary integral equations. The elastic body is divided into subregions, and the surface and interfaces are represented by quadrilateral and triangular elements with quadratic variation of geometry and linear, quadratic or cubic variation of displacement and traction with respect to intrinsic co-ordinates. The integral equation is discretized for each subregion, and a system of banded form obtained. For the integration of kernel-shape function products, Gaussian quadrature formulae are chosen according to upper bounds for error in terms of derivatives of the integrands. Use of the integral formulation is illustrated by the analysis of a prestressed concrete nuclear reactor pressure vessel.  相似文献   
76.
77.
94 schizophrenic patients served as Ss. 8 previously used and potential process-reactive measures were intercorrelated and factored by the principal-factor solution. 2 factors were rotated. The 1st factor, consisting of marital status and the Philips, Elgin, and Ullmann-Giovannoni scales, consisted of traditional process-reactive measures. The variables making up the 2nd factor do not appear to be appropriate process-reactive indices. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
78.
79.
A hybrid method for locating multipole equilibrium configurations has been proposed recently. The hybrid method combined the efficiency of a quasi-Newton method capable of locating stable and unstable equilibrium solutions with a robust homotopy method capable of tracking equilibrium paths with turning points and exploiting sparsity of the Jacobian matrix at the same time. A quasi-Newton method in conjunction with a deflation technique is proposed here as an alternative to the hybrid method. The proposed method not only exploits sparsity and symmetry, but also represents an improvement in efficiency.  相似文献   
80.
Yielding of the clamped-wire system in the Ilizarov external fixator   总被引:3,自引:0,他引:3  
This study demonstrates that the clamped-wire system used to suspend bones within an Ilizarov external fixator yields when the perpendicular load exceeds 50 N per wire. Cyclic loading was applied to tensioned wires clamped within an Ilizarov ring component, with steadily increasing load amplitude. Wires were tested at four initial tension settings. The amount of energy lost within the clamped-wire system per load cycle was calculated for every test. The results showed that there was a consistent trend to increasing non-recoverable energy loss per load cycle when peak loads exceed 50 N for all initial tension settings. A finite element (FE) model replicating the experimental conditions was performed to investigate the levels of stress within the loaded wires. The FE model analyses showed that high stresses were generated in the wires close to the clamping sites, and that the stress levels could reasonably be expected to exceed the material yield stress when loaded to about 55 N, for all initial tension settings. The results show that material yield, accompanied by some wire slippage through the clamps, is responsible for system yield, in agreement with previous studies. Although the initial wire tension has an appreciable effect on the wire stiffness, it did not affect the elastic load range of the clamped-wire system. To prevent yield of the clamped-wire system in practice, the fixator should be assembled with sufficient wires to ensure that the load transmitted to each wire by the patient does not exceed 50 N.  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