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   1544篇
  免费   3篇
电工技术   4篇
化学工业   118篇
金属工艺   5篇
机械仪表   9篇
建筑科学   15篇
能源动力   3篇
轻工业   121篇
水利工程   4篇
石油天然气   2篇
无线电   19篇
一般工业技术   81篇
冶金工业   1067篇
原子能技术   1篇
自动化技术   98篇
  2023年   6篇
  2021年   11篇
  2019年   17篇
  2018年   13篇
  2017年   17篇
  2016年   10篇
  2015年   5篇
  2014年   11篇
  2013年   17篇
  2012年   21篇
  2011年   20篇
  2010年   17篇
  2009年   19篇
  2008年   22篇
  2007年   22篇
  2006年   8篇
  2005年   11篇
  2004年   18篇
  2003年   12篇
  2002年   12篇
  2001年   16篇
  2000年   13篇
  1999年   32篇
  1998年   300篇
  1997年   188篇
  1996年   107篇
  1995年   70篇
  1994年   63篇
  1993年   68篇
  1992年   13篇
  1991年   28篇
  1990年   12篇
  1989年   23篇
  1988年   18篇
  1987年   12篇
  1986年   19篇
  1985年   17篇
  1983年   12篇
  1982年   10篇
  1981年   13篇
  1980年   14篇
  1979年   5篇
  1978年   8篇
  1977年   34篇
  1976年   91篇
  1975年   11篇
  1973年   8篇
  1971年   6篇
  1969年   8篇
  1968年   5篇
排序方式: 共有1547条查询结果,搜索用时 15 毫秒
61.
Thermofractography is suitable for the rapid identification of the basic components of epoxy resins. 2–3 mg of the polymer sample are being heated in the temperature gradient of 200 to 450°C. The thus forming decomposition products are being transferred as a starting line onto the separating thin layer by means of a carrier gas. After development the thermofractogram (TFG) shows in the temperature range of 200 to approx. 350°C the free oligomeres. The resulting phenols and their subsequent products appear on the TFG from 350°C. A cycloaliphatic type does not give phenolic fragments. The degradation mechanisms of epoxy resins are being discussed in regard to the TFG results and are being confirmed by establishing TGA curves. For the rapid evaluation of the thermofractograms of epoxy resins a questioning scheme is given as an evaluation key.  相似文献   
62.
Stahl CA  Berg EP 《Meat science》2003,64(2):169-174
The objective of this study was to evaluate the growth and meat quality of hogs supplemented with creatine monohydrate (CMH) and (or) a simple carbohydrate (dextrose) for the last 30 days of production. Crossbred market barrows (n=32; 75 kg) were blocked by weight and randomly allotted to one of eight pens with four animals per pen. Dietary treatments were a control (normal corn and soybean meal diet), CMH (control diet supplemented with 0.55% CMH), DEXT (control diet supplemented with 2.1% dextrose), and COMBO (control diet supplemented with CMH and DEXT). Average daily gain on test, fat depth, hot carcass weight, and LMA (postmortem dot grid measurement) were not affected by dietary treatment. However, a nonsignificant trend (P=0.07) was observed for 10th rib loin muscle area (LMA) gain on test as determined by real-time ultrasound comparisons over the course of the 30 days feeding duration (COMBO=4.24 cm(2) increase vs. control=1.0 cm(2) increase). No significant differences in pork quality were noted across treatment groups.  相似文献   
63.
Transformants of bakers' yeast (Saccharomyces cerevisiae) can be generated when non-growing cells metabolize sugars (without additional nutrients) in the presence of plasmid DNA. These results suggest that there is a mechanism by which DNA can naturally be taken up by the yeast cell. Natural transformation does not take place in common complete or minimal yeast culture media such as YPD and YNB. The starvation conditions used in our experiments thus seem to be an important prerequisite for such transformation events.  相似文献   
64.
For many organisms, meiotic double crossing over is less frequent than expected on the assumption that exchanges occur at random with respect to each other. This "interference," which can be almost total for nearby intervals, diminishes as the intervals in which the double crossovers are scored are moved farther apart. Most models for interference have assumed, at least implicitly, that the intensity of interference depends inversely on the physical distance separating the intervals. However, several observations suggest that interference depends on genetic distance (Morgans) rather than physical distance (base pairs or micrometers). Accordingly, we devise a model in which interference is related directly to genetic distance. Its central feature is that recombinational intermediates (C's) have two fates--they can be resolved with crossing over (Cx) or without (Co). We suppose that C's are distributed at random with respect to each other (no interference); interference results from constraints on the resolution of C's. The basic constraint is that each pair of neighboring Cx's must have between them a certain number of Co's. The required number of intervening Co's for a given organism or chromosome is estimated from the fraction of gene conversions that are unaccompanied by crossover of flanking markers. The predictions of the model are compared with data from Drosophila and Neurospora.  相似文献   
65.
66.
Forschung im Ingenieurwesen - Nasslaufende Lamellenkupplungen weisen zu Betriebsbeginn eine Phase des Einlaufens auf, in der sich das Reibungsverhalten durch Anpassung der Reibflächen...  相似文献   
67.
Cerebral palsy (CP) is a perinatally acquired nonprogressive brain damage resulting in motor impairment affecting mobility and posture. Early identification of infants with CP is desired to target early interventions and follow-up. During early infancy, distinct motion patterns occur which are highly predictive for later disability. These motor patterns can be observed and recorded. In this paper, a method to predict later CP based on early video recordings of the infants' spontaneous movements, applying optical flow and statistical pattern recognition, is presented. We extract motion information from video recordings of young infants using a total variation related optical flow method. By using wavelet analysis features from motion trajectories of points initiated on a regular grid were extracted and classified using a support vector machine.  相似文献   
68.
In this article, a new model predictive control approach to nonlinear stochastic systems will be presented. The new approach is based on particle filters, which are usually used for estimating states or parameters. Here, two particle filters will be combined, the first one giving an estimate for the actual state based on the actual output of the system; the second one gives an estimate of a control input for the system. This is basically done by adopting the basic model predictive control strategies for the second particle filter. Later in this paper, this new approach is applied to a CSTR (continuous stirred-tank reactor) example and to the inverted pendulum. These two examples show that our approach is also real-time-capable.  相似文献   
69.
A complete quantitative account of P. Wason's (1966) abstract selection task is proposed. The account takes the form of a mathematical model. It is assumed that some response patterns are caused by inferential reasoning, whereas other responses reflect cognitive processes that affect each card selection separately and independently of other card selections. The model parameters assess the contributions of different interpretational, inferential, and heuristic factors that jointly determine performance in the selection task. The interpretation of most of the model parameters in terms of these different factors is validated experimentally. This model of the selection task is the first to account for the observed frequencies of all 16 possible response patterns that can arise. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
70.
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