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   1685篇
  免费   30篇
  国内免费   2篇
化学工业   68篇
金属工艺   3篇
机械仪表   12篇
建筑科学   33篇
矿业工程   1篇
能源动力   11篇
轻工业   43篇
水利工程   10篇
石油天然气   3篇
无线电   14篇
一般工业技术   52篇
冶金工业   1414篇
原子能技术   3篇
自动化技术   50篇
  2023年   3篇
  2022年   7篇
  2021年   10篇
  2020年   9篇
  2019年   7篇
  2018年   12篇
  2017年   10篇
  2016年   6篇
  2015年   11篇
  2014年   16篇
  2013年   21篇
  2012年   16篇
  2011年   11篇
  2010年   14篇
  2009年   8篇
  2008年   21篇
  2007年   15篇
  2006年   13篇
  2005年   9篇
  2004年   13篇
  2003年   5篇
  2002年   3篇
  2001年   8篇
  2000年   3篇
  1999年   40篇
  1998年   407篇
  1997年   230篇
  1996年   179篇
  1995年   86篇
  1994年   81篇
  1993年   69篇
  1992年   18篇
  1991年   29篇
  1990年   23篇
  1989年   11篇
  1988年   14篇
  1987年   24篇
  1986年   14篇
  1985年   14篇
  1984年   3篇
  1983年   5篇
  1982年   14篇
  1981年   13篇
  1980年   15篇
  1979年   2篇
  1978年   4篇
  1977年   52篇
  1976年   107篇
  1975年   2篇
  1968年   2篇
排序方式: 共有1717条查询结果,搜索用时 46 毫秒
51.
It has been established that hippocampus, enthorhinal cortex, amygdala and substantia nigra (pars reticulata) lesions before head injury lead to a decrease of kainic acid-induced behavioral and electrographic seizure expressions. It can be concluded that after head injury the activation of limbic structures excitability due to excitation of "inputs" to these formations takes place. The obtained data indicate the significant role of nucleus caudatus in activation of posttraumatic brain excitatory mechanisms.  相似文献   
52.
53.
54.
55.
With the ever-increasing use of pharmaceuticals and the relatively high risk of developing drug allergies, particularly for patients in hospitals and for ambulatory patients with a history of drug allergy, the need to develop in vitro assays for drug allergy is great. In the early 1970's a mast cell technique was developed for diagnosis of drug allergies. A PRIST inhibition assay has also recently been developed to detect IgE antibodies to drug allergens. This test has also been referred to as the Total IgE Inhibition Test by Specific Drug Allergen, and is a variant of the in vitro RAST Test. In vitro mast cell and IgE inhibition tests are applied for identification of drug and chemical allergens and for their cautious clinical trial to prevent future drug and chemical reactions. Over the last eight years, over 1,300 patients were examined utilizing the mast cell technique. Over 100 drugs were tested, with penicillin, barbiturates, "caine" derivatives and sulfonamides most frequently employed. Of 270 patients with well-defined drug reactions, 190 (70 per cent) gave a positive response to the mast cell test. Eighty-five per cent of sera tested with Type I reactions gave a mast cell response. Of these, a group of 30 patients was studied with PRIST inhibition as well. Procedures for comparative testing of necessary drugs and/or chemicals in cases of high anaphylaxis risk of reaction in the clinical setting, hospital or office are included in the study as well as individual case reports. Mast cell assay coupled with IgE inhibition has been successfully used to diagnose drug and chemical allergic reactions. The incidence of positivity is high when the offending drug causes a Type I allergic reaction. The cases reported indicate that both the Mast Cell and the PRIST inhibition assays are useful for diagnosing and setting the clinical treatment and clinical course of the patient. The mast cell assay would be potentially employed for patient use in hospitals where the incidence of drug allergy is highest and for occupational health in the chemical industry. The greatest potential would be in outpatient care applied to patients with multiple drug allergies in the selection of safe drugs (test negative by both methods, and other clinical studies) for future drug usage.  相似文献   
56.
Peg Solitaire is a well known puzzle, which can prove difficult despite its simple rules. Pegs are arranged on a board such that at least one ‘hole’ remains. By making draughts/checkers-like moves, pegs are gradually removed until no further moves are possible or some goal configuration is achieved. This paper considers the English variant, consisting of a board in a cross shape with 33 holes. Modelling Peg Solitaire via constraint or integer programming techniques presents a considerable challenge and is examined in detail. The merits of the resulting models are discussed and they are compared empirically. The sequential nature of the puzzle naturally conforms to a planning problem, hence we also present an experimental comparison with several leading AI planning systems. Other variants of the puzzle, such as ‘Fool's Solitaire’ and ‘Long-hop’ Solitaire are also considered.  相似文献   
57.
The aim of this work is to produce a simplified vegetation map of ice-free areas of the Fildes Peninsula (FP) and Ardley Island (AI) thought object-oriented classification using a QuickBird satellite image and to evaluate the influence of the global solar radiation (GSR) over the vegetation distribution. The vegetation data were generated from multiresolution segmentation using the panchromatic and infrared layers, and for the classification we calculated the normalized vegetative difference index (NVDI) and the green NVDI. Two classes were created – Lichen and Moss Cushion SubFormation and Moss Subformation – with 48 vegetation samples collected on surveys during the austral summers of 2008 and 2009. We used a kappa index to evaluate the classification efficiency using 100 sampled points obtained in austral summer of 2013. The GSR was estimated, and in order to evaluate the effect of meteorological phenomena and cloudless, we measured the GSR using a net radiometer model CNR4 installed in FP between 2014 and 2016. The estimate of GSR was done for seasons of 2015, in order to estimate the light compensation point and the saturation point for the plant communities in FP and AI. The kappa index was 0.73 and the global accuracy was 0.78, showing consistency between the classification and ground truth. The area was covered by vegetation in FP was 16.7% and in AI is 59.1%. The vegetation cover is distributed differently at FP and AI, and our results suggest GSR plays an important role in vegetation distribution and these tendencies could be related to greater GSR demand by mosses when compared to lichens.  相似文献   
58.
59.
60.
The thermomechanical degradation and thermostabilization of poly(lactic acid) (PLA) have been studied using subsequent extrusion cycles under different temperature profiles. Primary and secondary antioxidants were used to avoid degradation process during extrusion. Melt flow index (MFI), size exclusion chromatography (SEC), and infrared spectroscopy (FTIR) analysis were used to evaluate the degradation and stabilization of PLA. The MFI and SEC analysis show that the main thermodegradation mechanism of PLA is governed by scission reactions. FTIR analysis confirmed the SEC results and showed that the synergetic effect between primary and secondary antioxidant is a suitable way to thermostabilize the PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40023.  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