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   1850篇
  免费   39篇
  国内免费   6篇
电工技术   149篇
综合类   5篇
化学工业   413篇
金属工艺   43篇
机械仪表   59篇
建筑科学   41篇
能源动力   64篇
轻工业   155篇
水利工程   5篇
无线电   177篇
一般工业技术   330篇
冶金工业   302篇
原子能技术   21篇
自动化技术   131篇
  2023年   10篇
  2022年   11篇
  2021年   21篇
  2020年   15篇
  2019年   37篇
  2018年   22篇
  2017年   23篇
  2016年   29篇
  2015年   16篇
  2014年   30篇
  2013年   80篇
  2012年   55篇
  2011年   89篇
  2010年   61篇
  2009年   67篇
  2008年   84篇
  2007年   73篇
  2006年   70篇
  2005年   76篇
  2004年   59篇
  2003年   64篇
  2002年   59篇
  2001年   33篇
  2000年   37篇
  1999年   34篇
  1998年   127篇
  1997年   74篇
  1996年   76篇
  1995年   39篇
  1994年   28篇
  1993年   48篇
  1992年   19篇
  1991年   20篇
  1990年   24篇
  1989年   17篇
  1988年   27篇
  1987年   14篇
  1986年   16篇
  1985年   29篇
  1984年   22篇
  1983年   10篇
  1982年   18篇
  1981年   13篇
  1980年   17篇
  1979年   15篇
  1978年   13篇
  1977年   10篇
  1976年   23篇
  1975年   13篇
  1973年   6篇
排序方式: 共有1895条查询结果,搜索用时 15 毫秒
101.
The experience of an emotion considered to be culturally unique (i.e., Japanese Amae) was tested in the United States, where there is no word to describe the concept. North American and Japanese participants read scenarios in which a friend made an inappropriate request (Amae), made no request, or made the request to another friend. Both American and Japanese participants felt more positive emotion and perceived the requester as feeling closer to them in the Amae condition than in the other two conditions. However, Americans felt more in control when asked for a favor than when not asked, a pattern that did not emerge among the Japanese. Cultural specificity of hypocognized emotions is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
102.
We investigate the electronic states of underdoped La 2–x Sr x CuO 4 (LSCO) by using a microscopic model, i.e., t-t-t-J model, containing charge stripes. The numerically exact diagonalization calculation is employed on small clusters. The physical properties observed in the angle-resolved photoemission and optical conductivity experiments are consistently explained in the model with vertical stripes, but not diagonal ones. These results demonstrate a crucial role of the vertical stripes in underdoped LSCO.  相似文献   
103.
Far-infrared laser oscillation due to cyclotron emission in the light hole band of p-type germanium was observed under crossed electric and magnetic fields. The wavelength is inversely proportional to magnetic fields with a cyclotron mass ofm c =0.048m c . Numerical calculations based on Luttinger Hamiltonian show that mixing of wavefunctions between the light and heavy hole bands causes population inversion betweenn=0 andn=1 light-hole Landau levels. It is also shown that non-equidistant energy spacing of light-hole Landau levels is essential to yield net amplification.  相似文献   
104.
105.
Japanese Society of Cryopreserved Thoracic Tissue Implantation was recently set up. Cryopreserved allograft valves are about to pervade in Japan. To clarify the interest, demands and supply of cryopreserved allograft valve in the area of Kyushu and Yamaguchi, we performed questionnaire investigation regarding this issue. Collection rate of this questionnaire was 87.5% (35/40 hospitals). Ninety-seven percent of the hospitals answered that they were interested in cryopreserved allograft. Ninety-four percent of the hospitals answered that they did not ethically hesitate to use cryopreserved allograft. Ninety-one percent of the hospitals hoped to perform cardiac surgery using allograft aortic valve if allograft is available. With respect to securing donors of allograft, two-third of the hospitals did not decide whether they could be involved in obtaining donors of allograft. As the number of the cadaver kidney donors is about 20 per year in the area of Kyushu and Yamaguchi, shortage of donors of allograft valve is anticipated.  相似文献   
106.
The pore-forming alpha 1 subunit of L-type calcium (Ca2+) channels is the molecular target of Ca2+ channel blockers such as phenylalkylamines (PAAs). Association and dissociation rates of (-)devapamil were compared for a highly PAA-sensitive L-type Ca2+ channel chimera (Lh) and various class A Ca2+ channel mutants. These mutants carry the high-affinity determinants of the PAA receptor site in a class A sequence environment. Apparent drug association and dissociation rate constants were significantly affected by the sequence environment (class A or L-type) of the PAA receptor site. Single point mutations affecting the high-affinity determinants in segments IVS6 of the PAA receptor site, introduced into a class A environment, reduced the apparent drug association rates. Mutation I1811M in transmembrane segment IVS6 (mutant AL25/-I) had the highest impact and decreased the apparent association rate for (-)devapamil by approximately 30-fold, suggesting that this pore-lining isoleucine in transmembrane segment IVS6 plays a key role in the formation of the PAA receptor site. In contrast, apparent drug dissociation rates of Ca2+ channels in the resting state were almost unaffected by point mutations of the PAA receptor site.  相似文献   
107.
108.
This paper deals with the improvements in response time and reliability of the aWO3/LiClO4-PC (propylene carbonate) electrochromic display. Response time was improved by adopting the highly porous a-WO3 film, the porous reflector and the high surface area non-polarizable counter-electrode. Results from the reliability tests indicated that the ECD had a sufficient lifetime for practical applications such as in watches, clocks and calculators. The mechanism of performance drift upon cycling the display is investigated using ESCA, AES and atomic absorption methods.  相似文献   
109.
The behavior of polycations as flocculants for kaolinite was examined by means of turbidity measurement, with the use of the following four kinds of cationic polysulfones, with molecular weights ranging from 14,000 to 330,000; diallyldimethylammonium chloride SO2 copolymer [P(DADMAmCl? SO2)], diallyldiethylammonium chloride–SO2 copolymer [P(DADEAmCl? SO2)], diallylmethylamine hydrochloride–SO2 copolymer [P(DAMA? HCl? SO2)], diallylamine hydrochloride–SO2 copolymer [P(DAAHCl? SO2)]. The effect of the degree of polymerization on the flocculation was remarkable at low molecular weight range. The flocculation value, which is defined as the quantity of the polycation required to obtain 50% transparency at 660 mμ of the supernatant fluid of 2% kaolinite suspension, was inversely proportional to the degree of polymerization to the 0.734 power in the case of P(DADMAmCl? SO2). This can be understood as the extension of Schulze-Hardy's law. The four different kinds of polysulfones having a similar molecular weight show almost the same capacity for flocculation in acidic or neutral solution. In alkaline solution, however, P(DAMAHCl? SO2) and P(DAA? HCl? SO2) are less effective and have higher flocculation values than P(DADMAmCl? SO2) and P(DADEAmCl? SO2), which are classified as polyquaternary ammonium chlorides. Moreover the difference increases with increasing pH. This may be attributable to the difference of the dissociability of the polycation. The degree of dissociation of P(DAMA? HCl? SO2) or P(DAA? HCl? SO2) decreases with increasing pH and more additive is required to neutralize negative charges on kaolinite. On the other hand, P(DADMAmCl? SO2) and P(DADEAmCl? SO2) are almost completely dissociated and are good flocculants over a wide range of pH.  相似文献   
110.
Gene expression profiling data from DNA microarray were analyzed using the fuzzy neural network (FNN) modeling method for predicting the distant metastases of breast cancer. The best model consisting of five genes was able to predict metastases of breast cancer with 94% accuracy. Furthermore, 100% accuracy was achieved by majoritarian decision using only 25 genes from five noninferior models which were constructed independently. From the constructed model, gene expression rules, which may cause distant metastases, were explicitly extracted and 60% of the metastases cases could be explained by this rule. The FNN modeling method described in this paper enables precise extraction of significant biological markers affecting prognosis without prior knowledge.  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