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   928篇
  免费   35篇
电工技术   6篇
综合类   10篇
化学工业   229篇
金属工艺   3篇
机械仪表   19篇
建筑科学   32篇
矿业工程   6篇
能源动力   14篇
轻工业   145篇
水利工程   9篇
石油天然气   3篇
无线电   47篇
一般工业技术   129篇
冶金工业   229篇
原子能技术   1篇
自动化技术   81篇
  2023年   11篇
  2022年   28篇
  2021年   42篇
  2020年   17篇
  2019年   23篇
  2018年   21篇
  2017年   26篇
  2016年   17篇
  2015年   17篇
  2014年   23篇
  2013年   65篇
  2012年   37篇
  2011年   52篇
  2010年   47篇
  2009年   35篇
  2008年   47篇
  2007年   27篇
  2006年   43篇
  2005年   36篇
  2004年   27篇
  2003年   25篇
  2002年   20篇
  2001年   10篇
  2000年   10篇
  1999年   10篇
  1998年   11篇
  1997年   14篇
  1996年   20篇
  1995年   11篇
  1994年   5篇
  1993年   9篇
  1992年   5篇
  1991年   9篇
  1990年   11篇
  1989年   11篇
  1988年   11篇
  1987年   15篇
  1986年   8篇
  1985年   10篇
  1984年   5篇
  1983年   7篇
  1980年   6篇
  1979年   4篇
  1978年   7篇
  1977年   8篇
  1976年   5篇
  1975年   8篇
  1974年   7篇
  1973年   5篇
  1972年   8篇
排序方式: 共有963条查询结果,搜索用时 15 毫秒
1.
DNA methylation is one of the most studied epigenetic mechanisms that play a pivotal role in regulating gene expression. The epigenetic component is strongly involved in aging-bone diseases, such as osteoporosis and osteoarthritis. Both are complex multi-factorial late-onset disorders that represent a globally widespread health problem, highlighting a crucial point of investigations in many scientific studies. In recent years, new findings on the role of DNA methylation in the pathogenesis of aging-bone diseases have emerged. The aim of this systematic review is to update knowledge in the field of DNA methylation associated with osteoporosis and osteoarthritis, focusing on the specific tissues involved in both pathological conditions.  相似文献   
2.
Soybean oil hydrogenation alters the linolenic acid molecule to prevent the oil from becoming rancid, however, health reports have indicated trans-fat caused by hydrogenation, is not generally regarded as safe. Typical soybeans contain approximately 80 g kg−1 to 120 g kg−1 linolenic acid and 240 g kg−1 of oleic acid. In an effort to accommodate the need for high-quality oil, the United Soybean Board introduced an industry standard for a high oleic acid greater than 750 g kg−1 and linolenic acid less than 30 g kg−1 oil. By combing mutations in the soybean plant at four loci, FAD2-1A and FAD2-1B, oleate desaturase genes and FAD3A and FAD3C, linoleate desaturase genes, and seed oil will not require hydrogenation to prevent oxidation and produce high-quality oil. In 2017 and 2018, a study comparing four near-isogenic lines across multiple Tennessee locations was performed to identify agronomic traits associated with mutations in FAD3A and FAD3C loci, while holding FAD2-1A and FAD2-1B constant in the mutant (high oleic) state. Soybean lines were assessed for yield and oil quality based on mutations at FAD2-1 and FAD3 loci. Variations of wild-type and mutant genotypes were compared at FAD3A and FAD3C loci. Analysis using a generalized linear mixed model in SAS 9.4, indicated no yield drag or other negative agronomic traits associated with the high oleic and low linolenic acid genotype. All four mutations of fad2-1A, fad2-1B, fad3A, and fad3C were determined as necessary to produce a soybean with the new industry standard (>750 g kg−1 oleic and <30 g kg−1 linolenic acid) in a maturity group-IV-Late cultivar for Tennessee growers.  相似文献   
3.
今天的液晶显示器(LCD)所达到的性能和图像质量在仅仅几年之前还是梦想,LCD显示器在几个相关的前沿领域不断发展.小型LCD体现得比其他任何领域都更为真切.手机行业的激烈竞争和螺旋式上升的用户需求正在驱动显示技术去满足融合的需要,即移动通信与移动计算和/或移动娱乐的融合.  相似文献   
4.
Serum total cholesterol, high density lipoprotein (HDL) cholesterol, and triglyceride levels were studied in healthy male and female subjects consuming for one-week periods a diet of conventional food (CF) providing 42% of energy as fat, principally butter fat, and then in random order nutritionally complete, defined formula diets of moderate (32%) to very low (1%) fat content. Compared to CF, the formula with 32% of energy as corn oil lowered serum cholesterol by 25% and the ratio of total to HDL-cholesterol by 13%. Low (9%) and very low (1–3%) fat formulas reduced HDL-cholesterol by as much as 40%, raised the total: HDL-cholesterol ratio by about 20% and raised serum triglyceride levels by as much as 100%. When low and very low fat formulas were ingested for three weeks, these effects persisted although maximal responses occurred during the first week. These results demonstrated that a moderate fat formula diet with a high P/S ratio had a more favorable effect on serum lipid levels than various low fat formulas. Low fat conventional food diets should be studied in long-term controlled metabolic experiments before such diets are recommended to the general population for coronary heart disease or cancer prevention.  相似文献   
5.
What is the current standard of practice for evaluations of juvenile competence to stand trial (JCST)? The present study surveyed psychologists regarding the practices used when conducting JCST evaluations. Respondents rated the importance of 17 elements that might be included in a JCST evaluation report. Of these elements, 7 were considered essential by 70% or more of respondents, with 9 additional elements rated as either essential or recommended. A majority of respondents felt that the use of psychological and forensic instruments was important. A list of tests used is provided, and the implications for the development of standards and policy are discussed to provide practitioners with additional knowledge that will help to further the state of the discipline. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
7.
We assessed effects of passive sensitization on human bronchial smooth muscle (BSM) response to mechanical stretching in vitro. Bronchial rings were sham (control) or passively sensitized overnight by using sera from donors demonstrating sensitivity to Dermatophagoides farinae and having immunoglobulin E (IgE) concentrations of 2,600 +/- 200 U/ml. Tissues were fixed isometrically to force transducers to measure responses to electrical field stimulation (EFS) and quick stretch (QS). The myogenic response to QS was normalized to the maximal response to EFS (%EFS). The myogenic response of sensitized BSM was 47.9 +/- 10.9 %EFS to a QS of approximately 6.5% optimal length (Lo); sham-sensitized tissues had a myogenic response of 13.5 +/- 6.4 %EFS (P = 0.012 vs. passively sensitized). A QS of approximately 13% Lo in sensitized BSM caused a response of 82.8 +/- 20.9 %EFS; sham-sensitized tissues developed a response of 38.2 +/- 17.3 %EFS (P = 0.004). BSM incubated with serum from nonallergic donors did not demonstrate increased QS response (4.6 +/- 1.4 %EFS, P = not significant vs. tissue exposed to atopic sera). However, tissues incubated in sera from nonatopic donors supplemented with hapten-specific chimeric IgE (JW8) demonstrated augmented myogenic response to QS of approximately 6.5% Lo (21.9 +/- 6.2 %EFS, P = 0. 027 vs. nonatopic sera alone). We demonstrate that passive sensitization of human BSM preparations causes induction and augmentation of myogenic contractions to QS; this hyperresponsiveness corresponds to the IgE concentration in sensitizing sera.  相似文献   
8.
Poor spellers in 2nd grade (n?=?128) participated in 24 20-min sessions that included (a) direct instruction in the alphabet principle (most frequent phoneme-spelling connections); (b) modeling of different approaches, singly and in combination, for developing connections between spoken and written words for 48 words ordered by sound-spelling predictability; and (c) practice in composing. Results of this multilayered intervention showed that (a) more than 1 way of developing sound-spelling connections is effective in teaching spelling but that after training in the alphabet principle, combining whole word and onset-rime training is most effective in achieving transfer of the alphabet principle across word contexts; (b) functional spelling units of not only a single letter but also 2 or more letters are important in beginning spelling; and (c) training in spelling transfers to composition and word recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
10.
M. I. Possner's 1980 reaction time (RT) paradigm was used to examine the engagement and disengagement operations of visual selective attention in patients with schizophrenia. In the 1st experiment 14 medicated, chronic schizophrenic Ss (diagnosed by criteria of the Diagnostic and Statistical Manual of Mental Disorders [DSM-I]), and 15 age-matched normal and control Ss made a speeded response to a target preceded by a valid, and invalid, or no cue. Control Ss showed the expected advantage and disadvantage in RT for valid and invalid cues, which suggests intact engagement and disengagement operations. For schizophrenic Ss, valid cues also enhanced RT, but invalid cues did not slow RT. Similar results were found in the 2nd experiment. The failure of unpredictable, invalid cues to inhibit RT in chronic schizophrenia may be related to an abnormality in the disengagement operation of selective attention. (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