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   25604篇
  免费   515篇
  国内免费   21篇
电工技术   274篇
综合类   26篇
化学工业   3073篇
金属工艺   278篇
机械仪表   386篇
建筑科学   994篇
矿业工程   47篇
能源动力   505篇
轻工业   2248篇
水利工程   287篇
石油天然气   29篇
无线电   1881篇
一般工业技术   2769篇
冶金工业   10288篇
原子能技术   159篇
自动化技术   2896篇
  2023年   76篇
  2022年   180篇
  2021年   303篇
  2020年   160篇
  2019年   233篇
  2018年   301篇
  2017年   280篇
  2016年   322篇
  2015年   287篇
  2014年   459篇
  2013年   744篇
  2012年   766篇
  2011年   1038篇
  2010年   724篇
  2009年   764篇
  2008年   788篇
  2007年   784篇
  2006年   636篇
  2005年   622篇
  2004年   570篇
  2003年   544篇
  2002年   480篇
  2001年   386篇
  2000年   357篇
  1999年   606篇
  1998年   3442篇
  1997年   2103篇
  1996年   1346篇
  1995年   792篇
  1994年   767篇
  1993年   766篇
  1992年   264篇
  1991年   271篇
  1990年   302篇
  1989年   277篇
  1988年   294篇
  1987年   210篇
  1986年   190篇
  1985年   242篇
  1984年   161篇
  1983年   121篇
  1982年   132篇
  1981年   162篇
  1980年   144篇
  1979年   113篇
  1978年   99篇
  1977年   247篇
  1976年   378篇
  1975年   93篇
  1974年   78篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
26 previously treated patients with progressive recurrent small cell lung cancer (SCLC) were given vinorelbine (Navelbine), 30 mg/m2 weekly. All patients had responded to first-line chemotherapy and were off therapy for at least 3 months. Partial response was observed in 4 out of 25 eligible patients (16%; 95% confidence interval 4-36%), stable disease in 7 patients and progression in 12 patients. The limiting toxicity was a non-cumulative leucopenia (80%, 32% WHO grade 3-4). Reaction at the site of injection was observed in 5 patients, causing treatment discontinuation in 2 cases. Other non-haematological toxicities were moderate. These results suggest acceptable toxicity and some antitumour activity of vinorelbine in pretreated SCLC patients.  相似文献   
34.
35.
In a previous study a solvent mixture of heptane containing 40 mass % heptanol was selected as an alternative in the industrial extraction of caprolactam to replace benzene, toluene, or chlorinated hydrocarbons. This work reports the equilibrium distribution ratio of caprolactam and four model impurities of organic nature, namely, cyclohexanone, aniline, n‐methylcaprolactam, and cyclohexane‐carboxamide, comparing the mixed solvents with toluene as a reference. The resulting phase equilibria were interpreted using the equilibrium stage model. Based on these calculations it was found that, compared to toluene, the co‐extracted fraction of cyclohexanone and aniline was higher, that of n‐methylcaprolactam was comparable, and that of cyclohexane‐carboxamide was lower using the mixed solvent. Overall, the mixed solvent reduced the fraction of co‐extracted impurities by almost 10 %.  相似文献   
36.
The mycotoxin contamination of feed components used by the Dutch cooperative feed industry was surveyed to estimate the risk for animal production losses. Of 89 randomly and 6 selectively taken samples of raw materials harvested in 1988 and 1989 27% were contaminated with ochratoxin A (OCHRA), 31% with zearalenone (ZEA) and 20% with deoxynivalenol (DON). The mean content (microgram/kg) of all positive randomly taken samples was 18 (OCHRA), 62 (ZEA) and 630 (DON). The highest level (microgram/kg) for all samples was 120 (OCHRA) in barley, 3100 (ZEA) in corn cob mix and 1900 (DON) in maizegluten feed. The results of this survey show that feed components are often contaminated with mycotoxins. However, the contamination level could only sporadically cause production losses in animal husbandry.  相似文献   
37.
Simulations with regional climate models (RCMs), carried out for the Rhine basin, have been analyzed in the context of implications of the possible future discharge of the Rhine river. In a first analysis, the runoff generated by the RCMs is compared to observations, in order to detect the way the RCMs treat anomalies in precipitation in their land surface component. A second analysis is devoted to the frequency distribution of area averaged precipitation, and the impact of selection of various driving global climate models.  相似文献   
38.
Often companies in the (petro‐) chemical industry claim that all possible countermeasures against potential accidents have been taken and therefore accidents are unforeseeable. In this paper we question this statement by analysing the pre‐warning signals (precursors) preceding a number of industrial accidents. 17 accidents that occurred in the (petro‐) chemical industry have been investigated by exploring FACTS, an accident database containing information about industrial accidents worldwide. This paper will demonstrate that the existence of precursor information could have been used to foresee and even prevent these accidents if a proper control action had been initiated. The accidents are analysed further, according to a control model, which was adapted from that of C. Argyris. It demonstrates the ineffectiveness of several elements of business process control loops and that the so‐called ‘double‐loop learning’ cycle is more important than the ‘single‐loop learning’ cycle if one considers safety improvement. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
39.
40.
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