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   8841篇
  免费   172篇
  国内免费   6篇
电工技术   63篇
综合类   2篇
化学工业   1252篇
金属工艺   76篇
机械仪表   113篇
建筑科学   231篇
矿业工程   7篇
能源动力   175篇
轻工业   376篇
水利工程   28篇
石油天然气   13篇
无线电   579篇
一般工业技术   857篇
冶金工业   4364篇
原子能技术   61篇
自动化技术   822篇
  2022年   55篇
  2021年   81篇
  2020年   47篇
  2019年   61篇
  2018年   86篇
  2017年   102篇
  2016年   126篇
  2015年   88篇
  2014年   114篇
  2013年   255篇
  2012年   213篇
  2011年   258篇
  2010年   213篇
  2009年   222篇
  2008年   212篇
  2007年   220篇
  2006年   225篇
  2005年   165篇
  2004年   178篇
  2003年   150篇
  2002年   147篇
  2001年   111篇
  2000年   104篇
  1999年   199篇
  1998年   1410篇
  1997年   864篇
  1996年   584篇
  1995年   344篇
  1994年   264篇
  1993年   304篇
  1992年   74篇
  1991年   85篇
  1990年   92篇
  1989年   84篇
  1988年   93篇
  1987年   75篇
  1986年   61篇
  1985年   110篇
  1984年   58篇
  1983年   60篇
  1982年   57篇
  1981年   93篇
  1980年   75篇
  1979年   53篇
  1978年   23篇
  1977年   113篇
  1976年   223篇
  1975年   44篇
  1974年   30篇
  1973年   26篇
排序方式: 共有9019条查询结果,搜索用时 22 毫秒
1.
INTRODUCTION: Even though there are few epidemiological studies evaluating the birth weights of different groups of malformed babies with chromosomal abnormalities, it is widely known that infants with trisomy 18, and to a lesser degree those with trisomy 13 and other chromosomal alterations, have low birth weights. PATIENTS AND METHODS: In this study we present the analysis of the birth weights and gestational ages of a large sample of babies (23,155 malformed and a similar number of nonmalformed babies), separating the different groups of chromosomal anomalies and comparing the weight in the clinical groups of malformed infants. RESULTS: Most of the groups with chromosomal abnormalities present lower birth weights in comparison to the other groups. CONCLUSIONS: The results of our study support the conclusion that the relationship between chromosomal alterations and low birth weight is sufficiently important that such a low birth weight in children with minor or major anomalies should be considered as one more indication to perform chromosomal analysis.  相似文献   
2.
3.
4.
A remarkable correlation exists between the degree of expansion of polyurethane foams and the structure of the reacting premixes. Polyurethane foams obtained from reacting premixes containing microemulsions are highly expanded. The expansion rate is proportional to the volume fraction of microemulsion in the premix. The stability of premixes with and without microemulsion is completely different suggesting distinct creaming mechanisms. We apply this idea to synthesize polyurethane foams from microemulsions successfully. This approach can be used to rationalize the design of polyurethane formulations leading to highly expanded foams.  相似文献   
5.
6.
Roasting coffee led to a drop in the ochratoxin A (OTA) concentration, as measured by the reference method, especially for dark type roasts. The way the beverage was prepared also affected the OTA content, which could paradoxically be higher than that of the initial roasted coffee. Assays on the thermal stability of pure OTA showed that it ought to be found in larger quantities in roasted coffee. This suggested that OTA was masked by reactions with the substrate during roasting. The absence of OTA in green coffee is therefore the best guarantee of safety.  相似文献   
7.
8.
9.
10.
Four hundred forty-six patients with Tourette Syndrome (TS) and/or their parents completed a 52-item self-report survey about vocal and motor tics, and the frequency of associated co-morbid conditions of aggression, obsessions and compulsions, attentional problems, sleep disturbance, mood disturbance, anxiety, and self-mutilative behaviours which have been frequently reported in the literature on TS. Respondents also responded to an open-ended question regarding the most disabling aspects of TS. Results were analyzed within two age groups; under 18 years of age (N = 245) and 18 years of age or older (N = 177). Tics and associated conditions were the most frequently reported disabling aspect by both age groups. Subjects under age 18, however, reported significantly more frequent problems with hyperactivity, temper control, aggressive behaviours and sleepwalking than adults with TS.  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