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   25428篇
  免费   462篇
  国内免费   124篇
电工技术   517篇
综合类   64篇
化学工业   3702篇
金属工艺   1023篇
机械仪表   735篇
建筑科学   679篇
矿业工程   71篇
能源动力   744篇
轻工业   2219篇
水利工程   224篇
石油天然气   190篇
武器工业   1篇
无线电   2700篇
一般工业技术   4483篇
冶金工业   6184篇
原子能技术   455篇
自动化技术   2023篇
  2022年   141篇
  2021年   231篇
  2020年   209篇
  2019年   238篇
  2018年   365篇
  2017年   353篇
  2016年   397篇
  2015年   260篇
  2014年   425篇
  2013年   1149篇
  2012年   653篇
  2011年   909篇
  2010年   686篇
  2009年   781篇
  2008年   822篇
  2007年   862篇
  2006年   687篇
  2005年   746篇
  2004年   618篇
  2003年   650篇
  2002年   689篇
  2001年   689篇
  2000年   615篇
  1999年   627篇
  1998年   2174篇
  1997年   1411篇
  1996年   1047篇
  1995年   721篇
  1994年   626篇
  1993年   643篇
  1992年   362篇
  1991年   347篇
  1990年   345篇
  1989年   348篇
  1988年   296篇
  1987年   269篇
  1986年   247篇
  1985年   279篇
  1984年   217篇
  1983年   201篇
  1982年   185篇
  1981年   218篇
  1980年   203篇
  1979年   164篇
  1978年   154篇
  1977年   277篇
  1976年   387篇
  1975年   128篇
  1974年   109篇
  1973年   117篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
A new numerical scheme for computing balancing coordinate transformations in linear systems theory is presented. The method is closely related to the Jacobi method for diagonalizing symmetric matrices. Here the minimization of the sum of traces of the Gramians by orthogonal and nonorthogonal Jacobi-type rotations is considered. The algorithm is shown to be globally convergent to a balancing transformation that arranges the Hankel singular values in a prescribed ordering. Local quadratic convergence of the algorithm is shown.  相似文献   
152.
The paper offers an associative-neural-net method to optimize resource allocation between independent tasks in a multiprocessor system. In the case of a dual-core CPU the method allows the task to be fully solved in O(M) operations. The text was submitted by the authors in English.  相似文献   
153.
 A three-axial tactile force sensor for the investigation of micromechanical structures has been developed using silicon micromachining technology. The sensor is capable of performing mechanical micro material characterisation such as the determination of the spring constant of complex micromechanical structures. Another application for this sensor is dimensional metrology where it has been tested as a 3D probe in a test set-up for coordinate measurements.  相似文献   
154.
The acidity constants, pK(a) values for protonation of some substituted thiazole derivatives were calculated by using AM1 and PM3 basis sets of semi-empirical methods and B3LYP/6-31G(d) basis sets of density functional theory (DFT) calculated physical and thermodynamic parameters. Correlation search among the experimental and calculated acidity constants, pK(a) values, revealed that the best correlation exist between the experimental and ab initio calculated pK(a) values with a regression of R(2)=0.98.  相似文献   
155.
In this paper we present storage structures for efficiently processing XML path queries on healthcare data stored in smart cards using XML format. In the design of the storage structures that we present, properties of healthcare data and fundamental types of queries on the healthcare data are taken into account as well as the constraints of the smart cards. We compare the space and time efficiency of the proposed storage structures for various types of queries.  相似文献   
156.
U. Rösler 《Algorithmica》2001,29(1-2):238-261
This paper develops general tools for the analysis of stochastic divide and conquer algorithms. We concentrate on the average performance and the distribution of the running time of the algorithm. As a special example we analyse the average performance and the running time distribution of the (2k + 1)-median version of Quicksort. Online publication October 13, 2000.  相似文献   
157.
1.  Embrittlement of the weld joints of the investigated chrome—manganese—nickel steels in the 350–500°C range is caused primarily by processes occurring in the -ferrite, 475° brittleness or precipitation of excess phases at the interphase boundaries and within the -ferrite grains. The level of plasticity is determined not by the quantily of -ferrite in the structure but by the density and quantity of excess phase precipitates in it.
2.  Aging processes occur in the weld zone at lower temperatures than in the base metal. For weld joints of the experimental steels 05Kh18G2N5T and 05Kh18G10N5M3F the maximum operating temperature for long service is 300°C and for 05Kh18G10N5M3AF steel below 300°C.
Volgograd Polytechnic Institute. A. A. Baikov Institute of Metallurgy. All-Union Scientific-Research and Design Institute for Chemical and Petroleum Apparatus Construction Technology. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 21–23, May, 1993.  相似文献   
158.
The article describes responsibility as a term with six relations and four different levels. It analyses the conflicts between different addresses, levels and values and emphasizes the need to integrate the responsibilities of the physician. The term "responsibility" provides a more differentiating analytical tool for conflicts in medical acting than the so-called "principles of biomedical ethics".  相似文献   
159.
In this paper some trends of gerontology during the last 45 years in Germany are described. A survey of the development of gerontology in the former GDR is followed by an analysis of the "Zeitschrift für Alternsforschung" from 1980-1990. The main result is the predominance of publications on the care system since the middle of the 1980s. With regard to the development of gerontology in the western part of Germany, an analysis of publications in the "Zeitsschrift für Gerontologie" from 1968-1991 shows changes in the main topics during this period. Until the middle of the 1970s there was a predominance of publications in the field of: intelligence, learning, memory and perception. The emphasis of publications from 1977-1985 was on stress and coping. In the middle of the 1980s there was an increasing interest in the analysis of social network and competence in the elderly. The paper discusses these trends of gerontological research in the eastern and western parts of Germany.  相似文献   
160.
Diclofenac HEP plaster was tested in an open study in the treatment of different traumatic sport and overload injuries, to confirm the results of efficacy and tolerability already shown in other clinical studies. A total of 101 patients were assigned to treatment and were eligible for the evaluation of results at the end of a 14-day treatment period. The average score of spontaneous pain, assessed by means of a verbal scale and a visual analogical scale, showed a clear difference in pain rating between the beginning and end of treatment. In general 60% pain reduction was observed. The difference in analgesic activity was already apparent on the 7th day of treatment (-28%). The reduction of pain was confirmed by changes in another subjective sign related to the injury: provoked pain. This symptom decreased in a manner comparable to spontaneous pain: 61% pain reduction after 2 weeks of treatment. Global assessment of efficacy, performed by the investigator at the end of treatment, showed the clear therapeutic activity of local treatment with diclofenac HEP plaster. Satisfactory results were obtained and only 18% of the patients (most of them with chronic and persistent pain) experienced ineffective pain relief at the end of the 2-week treatment. The beneficial effects of diclofenac HEP plaster on pain are confirmed by the patients' assessment, since almost identical scores were obtained. It is striking that the overall tolerance of diclofenac HEP plaster, applied topically twice a day for 2 weeks, was "good" or "excellent" in the 101 patients treated. Any side effect was reported on the patient's card and all the patients completed the study.  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