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   18222篇
  免费   432篇
  国内免费   25篇
电工技术   227篇
综合类   13篇
化学工业   3994篇
金属工艺   279篇
机械仪表   363篇
建筑科学   882篇
矿业工程   116篇
能源动力   449篇
轻工业   1396篇
水利工程   165篇
石油天然气   182篇
武器工业   1篇
无线电   1043篇
一般工业技术   2837篇
冶金工业   4367篇
原子能技术   170篇
自动化技术   2195篇
  2022年   147篇
  2021年   210篇
  2020年   188篇
  2019年   205篇
  2018年   237篇
  2017年   218篇
  2016年   273篇
  2015年   229篇
  2014年   352篇
  2013年   1067篇
  2012年   622篇
  2011年   863篇
  2010年   562篇
  2009年   612篇
  2008年   788篇
  2007年   743篇
  2006年   746篇
  2005年   631篇
  2004年   504篇
  2003年   493篇
  2002年   490篇
  2001年   318篇
  2000年   327篇
  1999年   318篇
  1998年   291篇
  1997年   317篇
  1996年   325篇
  1995年   306篇
  1994年   320篇
  1993年   369篇
  1992年   323篇
  1991年   235篇
  1990年   275篇
  1989年   284篇
  1988年   223篇
  1987年   284篇
  1986年   269篇
  1985年   322篇
  1984年   298篇
  1983年   256篇
  1982年   236篇
  1981年   248篇
  1980年   196篇
  1979年   230篇
  1978年   228篇
  1977年   172篇
  1976年   174篇
  1975年   202篇
  1974年   160篇
  1973年   159篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Experimental tests showed that poststrike elevation in tongue-flicking rate (PETF) and strike-induced chemosensory searching (SICS) in the gila monster last longer than reported for any other lizard. Based on analysis of numbers of tongue-flicks emitted in 5-min intervals, significant PETF was detected in all intervals up to and including minutes 41–45. Using 10-min intervals, PETF lasted though minutes 46–55. Two of eight individuals continued tongue-flicking throughout the 60 min after biting prey, whereas all individuals ceased tongue-flicking in a control condition after minute 35. The apparent presence of PETF lasting at least an hour in some individuals suggests that there may be important individual differences in duration of PETF. PETF and/or SICS are present in all families of autarchoglossan lizards studied except Cordylidae, the only family lacking linguallly mediated prey chemical discrimination. However, its duration is known to be greater than 2-min only in Helodermatidae and Varanidae, the living representatives of Varanoidea. That prolonged PETF and SICS are typical of snakes provides another character supporting a possible a varanoid ancestry for Serpentes. Analysis of 1-min intervals showed that PETF occurred in the first minute. A review of the literature suggests that a pause in tongue-flicking and delay of searching movements are absent in lizards and the few nonvenomous colubrid snakes tested. The delayed onset of SICS may be a specific adaptation of some viperid snakes to allow potentially dangerous prey to be rendered harmless by venom following voluntary release after envenomation and preceding further physical contact with the prey.  相似文献   
12.
With the goal of improving process efficiency and reducing risk, this article describes a pollution-prevention analysis technique that can be applied to most secondary steel heat-treating operations involving quenching. Costs, risk assessments, and pollution-prevention options are discussed, as are the effects of quenching on two subsequent processes—parts cleaning and tempering. In contrast to many process comparisons, the issues of worker exposure, material safety and toxicity, liability, waste reduction, reclamation, and disposal are emphasized.  相似文献   
13.
14.
The dependence of the cetane number of hydrotreated light cycle oil on chemical composition has been investigated. Cetane number was related to hydrogen content and aromaticity. The latter was determined by high performance liquid chromatography and also by carbon-13 n.m.r. spectroscopy. Specific correlations were developed in each case and a regression coefficient of 0.99 and a standard error of 1.25 were obtained for the best case. The usefulness of predicting cetane number from fuel composition is discussed.  相似文献   
15.
16.
Recent, as well as past, studies of reactor trip frequencies and other types of operating experience have shown that relatively high frequencies are likely in new plants with little accumulated operating time. In order to better understand all the factors which contribute to high frequencies in new plants, the authors have made a comparison of reactor trip frequencies between plants which went into operation in the 1960's and the early 1970's and those which have gone into operation more recently. Trip frequency versus accumulated operating time for two plant groups are compared to see the extent to which design differences (e.g., capacity, thermal margin) affect trip frequency.This paper also presents a review of some recent events in which plant age has played a major role. The events which are reviewed have been identified through the normal systematic event analysis program conducted by the NRC. Information regarding these events was obtained through followup by reviews conducted by NRC Resident Inspectors as well as event reports submitted by licensees.  相似文献   
17.
MKT1 is required for m aintenance of K2 above 30°C in strains with the L-A-HN variant of the L-A double-stranded RNA virus of Saccharomyces cerevisiae. We report that MKT1 encodes a 92 979 Da protein with serine-rich regions and the retroviral protease signature, DTG, but with no substantial homology to proteins presently in the databases. This sequence is available from GenBank under Accession Number U09129.  相似文献   
18.
Examined the effects of traditional Asian cultural norms, family roles, and values upon the psychodynamic formulation of a 25-yr-old Asian American man. The main tenets of control-mastery theory (CMT; J. Weiss et al [1986]), a cognitive approach to psychoanalytic psychotherapy, are presented, and its plan formulation method is discussed. The need for a more comprehensive consideration of Asian culture, Asian-American identity formation, and acculturative stress in clinical case formulations is presented. Theory modifications are discussed that should help to reconcile differences between the Western values inherent in CMT and traditional Asian approaches to psychotherapy and mental health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
19.
72 patients engaged in residential drug abuse treatment who also had cognitive impairment were randomly assigned to 1 of 4 groups. One group of patients received 2 hrs of computer-assisted cognitive rehabilitation per week over a 6-mo period; a 2nd group received 2 hrs of progressive muscle relaxation per week over a 6-mo period; a 3rd group was taught typing on a computer; and a 4th group received no treatment beyond that provided by the program. All patients were tested with a neuropsychological test battery at admission and at monthly intervals thereafter for 6 mo. Results show that Ss in the cognitive rehabilitation group demonstrated a faster rate of cognitive recovery during the first 2 mo of treatment and had more efficient cognitive functioning over the first 4 mo of residence. These patients were also rated as more "appropriately participatory" in the treatment program by the clinical staff. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
20.
Multisystemic therapy (MST) delivered through a community mental health center was compared with usual services delivered by a Department of Youth Services in the treatment of 84 serious juvenile offenders and their multiproblem families. Offenders were assigned randomly to treatment conditions. Pretreatment and posttreatment assessment batteries evaluating family relations, peer relations, symptomatology, social competence, and self-reported delinquency were completed by the youth and a parent, and archival records were searched at 59 wks postreferral to obtain data on rearrest and incarceration. In comparison with youths who received usual services, youths who received MST had fewer arrests and self-reported offenses and spent an average of 10 fewer weeks incarcerated. In addition, families in the MST condition reported increased family cohesion and decreased youth aggression in peer relations. The relative effectiveness of MST was neither moderated by demographic characteristics nor mediated by psychosocial variables. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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