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   5187篇
  免费   61篇
  国内免费   11篇
电工技术   30篇
综合类   1篇
化学工业   600篇
金属工艺   208篇
机械仪表   86篇
建筑科学   98篇
矿业工程   10篇
能源动力   52篇
轻工业   310篇
水利工程   31篇
石油天然气   5篇
无线电   438篇
一般工业技术   637篇
冶金工业   2363篇
原子能技术   51篇
自动化技术   339篇
  2021年   34篇
  2019年   41篇
  2018年   37篇
  2017年   27篇
  2016年   50篇
  2015年   30篇
  2014年   45篇
  2013年   158篇
  2012年   93篇
  2011年   132篇
  2010年   90篇
  2009年   120篇
  2008年   136篇
  2007年   121篇
  2006年   117篇
  2005年   109篇
  2004年   107篇
  2003年   101篇
  2002年   90篇
  2001年   80篇
  2000年   96篇
  1999年   117篇
  1998年   561篇
  1997年   381篇
  1996年   289篇
  1995年   194篇
  1994年   155篇
  1993年   198篇
  1992年   87篇
  1991年   85篇
  1990年   79篇
  1989年   84篇
  1988年   85篇
  1987年   105篇
  1986年   63篇
  1985年   74篇
  1984年   39篇
  1983年   48篇
  1982年   48篇
  1981年   51篇
  1980年   53篇
  1979年   30篇
  1978年   48篇
  1977年   77篇
  1976年   120篇
  1975年   44篇
  1974年   33篇
  1973年   32篇
  1972年   31篇
  1970年   33篇
排序方式: 共有5259条查询结果,搜索用时 46 毫秒
61.
The influence of convective heat transfer on constant current density anodizing of aluminium in sulfuric acid has been examined in a wall-jet electrode reactor. The uniformity of the anodic film thickness is related to the local electrode temperature distribution, which is dependent on the convection. The higher the local temperature, the greater the local oxide thickness. An increased local temperature enhances local field assisted oxide dissolution at the pore bases, and consequently acts to increase the local current density. At relatively high current densities, local features develop on the electrode surface, accompanied by high initial, local temperature rises. The relevance of such local features, limiting useful oxide growth, is considered further.  相似文献   
62.
Rates of poor psychological adjustment of children with sickle cell disease remained relatively constant over initial and follow-up assessment points. 50 children (aged 7–12 yrs) and their mothers completed the initial protocol. 30 children completed the follow-up plus 5 additional children and their mothers. These Ss were aged 7–24 yrs at follow-up. With initial levels of adjustment controlled, children's strategies for coping with pain accounted for a significant increment in child-reported symptoms and mother-reported internalizing behavior problems at follow-up beyond the contribution of illness and demographic parameters and follow-up interval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
63.
64.
65.
In contrast to D. C. Zuroff, M. Mongrain, and D. A. Santor (2004), the current authors find the promissory note of dependency-sociotropy (DEP-SOC) and self-criticism-autonomy (SC-AUT) as a model of risk for depression to be in default. The authors propose reorganizing what has been cast as unitary effort into 3 distinct endeavors: a psychoanalytic clinical theory, development of a refined empirical model of risk for clinical depression, and research examining the effects of DEP-SOC and SC-AUT on interpersonal relationships in nonclinical samples. The authors identify some issues that need to be accommodated regardless of whether the assessment of Zuroff et al. (2004) or their own is accepted. DEP-SOC and SC-AUT are best construed as correlated, continuous dimensions. Future work also needs to accommodate depression as chronic recurrent condition, advances in developmental psychopathology, and more stringent criteria for positing a risk factor for clinical disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
66.
Cryptococcal meningitis has a high mortality rate of central nervous infection. The patients usually die of the disease itself, or complications from increased intracranial pressure. Early diagnosis and treatment, including surgical drainage, will improve the results. In this series, twenty-one patients with high intracranial pressure (ICP > 300 mmH2 O) are presented. Fourteen received implantation of Ommaya reservoir to aspirate cerebrospinal fluid (CSF) for relief of symptoms of ICP. Meanwhile 4 of these 14 patients also received intraventricular injection of amphotericin B because of poor response to systemic drugs. Another seven patient received systemic drug therapy only. Survival during therapy occurred in 11 of 14 patients in the surgical group, compared with only 1 of 7 patients treated by drug therapy alone (P = 0.019). In the 14 patients who received implantation of an Ommaya reservoir, there was one complication of CSF leakage when the reservoir ruptured because of repeated aspiration. For patients with cryptococcal meningitis with high ICP, early implantation of an Ommaya reservoir will improve the survival rate.  相似文献   
67.
The normative data provided in the Wechsler Memory Scale—Revised (WMS—R) manual for individuals aged 25–34 yrs were estimated statistically by interpolation. As an empirical check of this procedure, a representative stratified sample in this age range was selected to match the 1980 US Census data on relevant demographic characteristics. Prorated Full Scale IQs for the group were normally distributed, having a mean of 101.3 (SD?=?14.58, range?=?72–231). Differences between the empirically derived and published index scores appeared to be clinically significant. Substantial intra-individual differences were common when Visual–Verbal or General–Attention/Concentration indexes were compared. Normative data for the WMS—R subtests, indexes, and distribution of differences between indexes is provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
68.
The inner filter effect is observed in luminescence whenever a second substance is present that has absorptions which overlap the luminescence. This results in a diminution of the luminescence at those wavelengths and is generally observed in solution. In the present communication we show that this effect can be observed when a solid rare earth complex is physically mixed with a solid luminescent organic matrix with which it does not interact. The resulting luminescence is reduced in emission intensity at those wavelengths corresponding to the absorptions of the rare earth ion. This is illustrated with a mixture of Na3[Ho(ODA)3] ·2NaClO4·6H2O and pyrene at 77 K, and it is shown that the absorption spectrum of the holmium complex can be extracted from the luminescence spectrum of pyrene. This absorption spectrum is in good agreement with that obtained by conventional spectroscopy with a single crystal.  相似文献   
69.
The 29Si MAS NMR spectra of the 2H, 4H, 6H, and 3C polytypes of silicon carbide are presented. An attempt is made to correlate differences in the chemical shifts with local atomic environment. The results of the analysis of the spectra of pure polytypes are used as a basic for the interpretation of the spectra of mixed polytypes and a discussion of the crystallinity and impurity levels of different samples. Carbon-13 chemical shifts obtained from spectra of the same polytypes are also tabulated.  相似文献   
70.
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