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   2826篇
  免费   39篇
  国内免费   21篇
电工技术   32篇
综合类   4篇
化学工业   334篇
金属工艺   55篇
机械仪表   64篇
建筑科学   42篇
矿业工程   3篇
能源动力   95篇
轻工业   89篇
水利工程   26篇
石油天然气   7篇
无线电   182篇
一般工业技术   371篇
冶金工业   1393篇
原子能技术   25篇
自动化技术   164篇
  2023年   23篇
  2022年   59篇
  2021年   86篇
  2020年   71篇
  2019年   52篇
  2018年   60篇
  2017年   69篇
  2016年   56篇
  2015年   38篇
  2014年   66篇
  2013年   109篇
  2012年   62篇
  2011年   82篇
  2010年   57篇
  2009年   76篇
  2008年   75篇
  2007年   50篇
  2006年   51篇
  2005年   19篇
  2004年   21篇
  2003年   28篇
  2002年   16篇
  2001年   16篇
  2000年   24篇
  1999年   64篇
  1998年   420篇
  1997年   266篇
  1996年   174篇
  1995年   104篇
  1994年   71篇
  1993年   96篇
  1992年   20篇
  1991年   41篇
  1990年   26篇
  1989年   34篇
  1988年   22篇
  1987年   38篇
  1986年   26篇
  1985年   39篇
  1984年   18篇
  1983年   12篇
  1982年   14篇
  1981年   8篇
  1980年   12篇
  1979年   9篇
  1978年   7篇
  1977年   33篇
  1976年   52篇
  1975年   5篇
  1969年   2篇
排序方式: 共有2886条查询结果,搜索用时 15 毫秒
61.
Journal of Failure Analysis and Prevention - In the original version of this article, Vipin’s name was incorrect. It is correct as reflected here. The original article has also been corrected.  相似文献   
62.
Alloy nanoparticles (NPs) can offer a wide range of opportunities for various applications due to their composition and structure dependent properties such as multifunctionality, electronic heterogeneity, site-specific response, and multiple plasmon resonance bands. In this work, the fabrication of self-assembled PdxAg1-x NPs alloy nanostructures with distinct size, density, shape, and composition is demonstrated via the solid-state dewetting of sputtered Pd/Ag thin films on c-plane sapphire. The initial stage of bilayer dewetting exhibits the nucleation of voids, followed by the expansion of voids and cluster breakdown and finally shape transformation along with the temperature control. Bilayer composition shows a substantial influence on the dewetting such that the overall dewetting is enhanced along with the increased Ag composition, i.e. Pd0.25Ag0.75 > Pd0.5Ag0.5 > Pd0.75Ag0.25. On the other hand, the size and density of NPs can be efficiently controlled by varying the initial thickness of bilayers. Reflectance peaks in UV and near-infrared (NIR) regions and a wide absorption band in the visible region arisen from the surface plasmon resonance are observed in reflectance spectra. The peak intensity depends on the composition of PdxAg1-x NPs and the NIR peaks gradually blue-shift with the size decrement.  相似文献   
63.
Microsystem Technologies - Due to fast technological development, human beings generally depend upon computer and other digital equipments in different areas of concern/applications. Therefore,...  相似文献   
64.
65.
Wireless Personal Communications - Increased dominance of mobile applications (henceforth, app) over conventional software applications is quite apparent; however, there is a lack of structured...  相似文献   
66.
Water Resources Management - Climatic changes have altered hydrological and climatic parameters worldwide, and climate projections suggest that such alterations will continue. In order to maintain...  相似文献   
67.
I compared reproductive success (lifetime number of fertilized eggs) as a function of mate choice among females of the stink bug, Nezara viridula L. (Hemiptera: Pentatomidae). 'Choosing' (C) females were placed with one of two males on alternate days. CI females chose between inexperienced males while CR females chose between males previously rejected by CI females. 'Non-choosing' (N) females were placed with the same male every day. Non-choosing NI, NR and NA females encountered, respectively, inexperienced males, previously rejected males, or previously accepted and mated males. Reproductive success was highest for CI females, showing direct selection on mate preferences. Reproductive success did not differ between CR and NR females, indicating that male quality, not the act of choosing a mate, affects fitness. CI females preferred males with longer antennae and their fecundity (lifetime number of eggs) was correlated with male antenna length, consistent with antenna length as an indicator of male ability to transfer nutritive sperm produced in paired harlequin lobes of the testes. Harlequin lobes were smaller in rejected than chosen males. In second-generation mate choice trials, sons of NR females competed well against sons of NA females but not against sons of CI females. This suggests that non-genetic paternal contributions that decline with prior mating account for the attractiveness of sons because sons of CI and NA females shared the same fathers. Sons experiencing mating success came from larger eggs and egg size was greatest for CI females, perhaps as a consequence of paternal nutritional contributions. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.  相似文献   
68.
The p38 mitogen-activated protein (MAP) kinase defines a subgroup of the mammalian MAP kinases that are induced in response to lipopolysaccharide, hyperosmolarity, and interleukin 1. p38 MAP kinase appears to play a role in regulating inflammatory responses, including cytokine secretion and apoptosis. Here we show that diverse classes of DNA-damaging agents such as cisplatinum, 1-beta-D-arabinofuranosylcytosine, UV light, ionizing radiation, and methyl methanesulfonate activate p38 MAP kinase. We also demonstrate that cells deficient in c-Abl fail to activate p38 MAP kinase after treatment with cisplatinum and 1-beta-D-arabinofuranosylcytosine but not after exposure to UV and methyl methanesulfonate. Reconstitution of c-Abl in the Abl-/- cells restores that response. Similar results were obtained for induction of the Jun-NH2-kinase/stress-activated protein kinase. These findings indicate that p38 MAP and Jun-NH2-kinase/stress-activated protein kinases are differentially regulated in response to different classes of DNA-damaging agents.  相似文献   
69.
Comparison of interaction energy between an oligonucleotide and a DNA-binding ligand in the minor and major groove modes was made by use of restrained molecular dynamics. Distortion in DNA was found for the major groove mode whereas less significant changes for both ligand and DNA were detected for the minor groove binding after molecular dynamics simulation. The conformation of the ligand obtained from the major groove modes resembles that computed with the ligand soaked in water. The van der Waals contact energy was found to be as significant as electrostatic energy and more important for difference in binding energy between these two binding modes. The importance of van der Waals force in groove binding was supported by computations on the complex formed by the repressor peptide fragment from the bacteriophage 434 and its operator oligonucleotide.  相似文献   
70.
This study tests the widely-cited claim from Volterra & Taeschner (1978), which is reinforced by Clark's PRINCIPLE OF CONTRAST (1987), that young simultaneous bilingual children reject cross-language synonyms in their earliest lexicons. The rejection of translation equivalents is taken by Volterra & Taeschner as support for the idea that the bilingual child possesses a single-language system which includes elements from both languages. We examine first the accuracy of the empirical claim and then its adequacy as support for the argument that bilingual children do not have independent lexical systems in each language. The vocabularies of 27 developing bilinguals were recorded at varying intervals between ages 0;8 and 2;6 using the MacArthur CDI, a standardized parent report form in English and Spanish. The two single-language vocabularies of each bilingual child were compared to determine how many pairs of translation equivalents (TEs) were reported for each child at different stages of development. TEs were observed for all children but one, with an average of 30% of all words coded in the two languages, both at early stages (in vocabularies of 2-12 words) and later (up to 500 words). Thus, Volterra & Taeschner's empirical claim was not upheld. Further, the number of TEs in the bilinguals' two lexicons was shown to be similar to the number of lexical items which co-occurred in the monolingual lexicons of two different children, as observed in 34 random pairings for between-child comparisons. It remains to be shown, therefore, that the bilinguals' lexicons are not composed of two independent systems at a very early age. Furthermore, the results appear to rule out the operation of a strong principle of contrast across languages in early bilingualism.  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