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   5850篇
  免费   277篇
  国内免费   21篇
电工技术   57篇
综合类   23篇
化学工业   1145篇
金属工艺   91篇
机械仪表   128篇
建筑科学   302篇
矿业工程   10篇
能源动力   240篇
轻工业   360篇
水利工程   56篇
石油天然气   31篇
无线电   534篇
一般工业技术   1179篇
冶金工业   846篇
原子能技术   46篇
自动化技术   1100篇
  2023年   56篇
  2022年   118篇
  2021年   186篇
  2020年   133篇
  2019年   178篇
  2018年   214篇
  2017年   137篇
  2016年   167篇
  2015年   133篇
  2014年   199篇
  2013年   353篇
  2012年   315篇
  2011年   353篇
  2010年   258篇
  2009年   265篇
  2008年   274篇
  2007年   277篇
  2006年   202篇
  2005年   194篇
  2004年   169篇
  2003年   175篇
  2002年   145篇
  2001年   86篇
  2000年   101篇
  1999年   75篇
  1998年   237篇
  1997年   164篇
  1996年   99篇
  1995年   108篇
  1994年   80篇
  1993年   71篇
  1992年   60篇
  1991年   45篇
  1990年   32篇
  1989年   32篇
  1988年   39篇
  1987年   35篇
  1986年   19篇
  1985年   29篇
  1984年   20篇
  1983年   15篇
  1982年   26篇
  1981年   29篇
  1980年   22篇
  1979年   21篇
  1978年   17篇
  1977年   26篇
  1976年   49篇
  1975年   14篇
  1972年   13篇
排序方式: 共有6148条查询结果,搜索用时 15 毫秒
51.
The collared peccary (Tayassu tajacu) is widely distributed over the American continent, being found from the south of the USA to the north of Argentina. In Brazil, it is spread all over the country, being one of the potential species to be raised in captivity. Therefore, the cytogenetic techniques could be a potential tool for reproductive monitoring of animals raised in captivity, mainly when destined for commercial purposes. This study had the objective of determining the chromosome number of two populations raised in captivity and characterizing them by GTG banding. For this purpose, an analysis was made of mitotic metaphases obtained from lymphocyte cultures made from blood samples of 11 animals, six of which from the Northeast and five from the North of Brazil. The results of this analysis showed the same karyotype pattern for the species (2n=30 chromosomes and NF=48), besides corresponding to the South American pattern of the species, i.e., without a translocation between autosomes 1 and 8, chromosome X acrocentric, and no differences were found between the two populations studied. However, chromosomal polymorphisms were observed compared to data from the literature on populations from North and South America.  相似文献   
52.
In the literature on statistical inference in software reliability, the assumptions of parametric models and random sampling of bugs have been pervasive. We argue that both assumptions are problematic, the first because of robustness concerns and the second due to logical and practical difficulties. These considerations motivate the approach taken in this paper. We propose a nonparametric software reliability model based on the order-statistic paradigm. The objective of the work is to estimate, from data on discovery times observed within a type I censoring framework, both the underlying distribution F from which discovery times are generated and N, the unknown number of bugs in the software. The estimates are used to predict the next time to failure. The approach makes use of Bayesian nonparametric inference methods, in particular, the beta-Stacy process. The proposed methodology is illustrated on both real and simulated data  相似文献   
53.
陆虎(Land Rover)G4越野挑战赛.是各大汽车公司彼此互相交流的重大活动。经过三年多的精心准备.2006年G4挑战赛正式拉开了帷幕——一个月时间,18组挑战者.4000公里行程.跨越泰国、老挝、巴西和波利维亚。本届赛事是2003年G4挑战赛的延续.它的前身就是2000年结束的“骆驼杯”越野挑战赛。  相似文献   
54.
This paper analyses inter-organizational networks that link together firms operating in the food processing and distribution industry in the UK. In doing so, the paper draws on insights recently developed by Mark Casson that treat inter-firm networks as an institutional response to the changing costs and opportunities of information management. Detailed analysis of product innovation and supply-chain management issues within the industry, exemplified by the growth of chilled ready-meals, leads to the identification of two distinct but complementary inter-firm networks: a network of control and a network of innovation. In each case, the study finds that the critical information is derived from the retailers' interface with consumers and thus that these information-based networks are effectively controlled by the leading supermarket chains. The study's conclusions are considered in relation to the recent findings of the UK Competition Commission following its investigation into grocery retailing in Britain.  相似文献   
55.
In 3 eye-tracking experiments, the authors investigated the use of morphological information during pronoun resolution. Experiments 1 and 2 showed that disruption occurred when a preferred assignment was inconsistent with gender information. Experiment 2 ensured that this difficulty was not due to the introduction of a new discourse entity. Experiment 3 showed that disruption also occurred when number information was inconsistent with the preferred assignment. The results indicate that the use of morphological information is delayed until after the computation of coreference relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
56.
Physalis angulata L (Solanaceae) is a medicinal plant from North of Brazil, whose different extracts and infusions are commonly used in the popular medicine for the treatment of malaria, asthma, hepatitis, dermatitis and rheumatism. However, the genotoxic effects of P. angulata on human cells is not well known. The main purpose of the present study was to evaluate the in vitro genotoxic effects of aqueous extract of P. angulata using the comet assay and the micronucleus assay in human lymphocytes provided from 6 healthy donors. Treatments with P. angulata extracts were performed in vitro in order to access the extent of DNA damage. The comet assay has shown that treatments with P. angulata at 0.5, 1.0, 2.0, 3.0 and 6.0 microg/mL in culture medium were genotoxic. Lymphocytes treated with P. angulata at the concentrations of 3.0 and 6.0 microg/mL in culture medium showed a statistically significant increase in the frequency of micronucleus (p<0.05), however, the cytokinesis blocked proliferation index (CBPI) was not decreased after P. angulata treatment. In conclusion, the present work demonstrated the genotoxic effects of P. angulata extract on human lymphocytes in vitro.  相似文献   
57.
58.
A new evaluation model for SK combinator expressions is presented and used as a basis for the design of a novel processor. The resulting machine architecture resembles a dataflow ring, but executions are constrained to be fully lazy. An automatic dynamic load sharing mechanism for a distributed multiprocessor architecture is suggested, and initial simulation results are presented.  相似文献   
59.
60.
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