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   809篇
  免费   61篇
  国内免费   1篇
电工技术   1篇
综合类   4篇
化学工业   295篇
金属工艺   1篇
机械仪表   15篇
建筑科学   18篇
矿业工程   2篇
能源动力   18篇
轻工业   203篇
水利工程   5篇
石油天然气   3篇
无线电   32篇
一般工业技术   126篇
冶金工业   83篇
原子能技术   1篇
自动化技术   64篇
  2024年   2篇
  2023年   9篇
  2022年   29篇
  2021年   67篇
  2020年   26篇
  2019年   19篇
  2018年   21篇
  2017年   23篇
  2016年   27篇
  2015年   34篇
  2014年   30篇
  2013年   66篇
  2012年   57篇
  2011年   64篇
  2010年   45篇
  2009年   30篇
  2008年   44篇
  2007年   50篇
  2006年   32篇
  2005年   30篇
  2004年   23篇
  2003年   17篇
  2002年   22篇
  2001年   10篇
  2000年   3篇
  1999年   5篇
  1998年   7篇
  1997年   3篇
  1996年   3篇
  1995年   3篇
  1994年   3篇
  1993年   6篇
  1992年   3篇
  1990年   5篇
  1989年   5篇
  1988年   6篇
  1987年   2篇
  1986年   3篇
  1984年   4篇
  1982年   4篇
  1981年   3篇
  1980年   4篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1975年   4篇
  1974年   2篇
  1968年   1篇
  1967年   1篇
  1965年   1篇
排序方式: 共有871条查询结果,搜索用时 15 毫秒
81.
A simple and rapid analytical procedure for determination of saccharin (SAC) and acesulfame-K (AC-K) based on UV-vis measurements and partial least squares (PLS) was proposed. Thus, an experimental design at levels 2 and 15 mg l−1 for SAC and 2 and 20 mg l−1 for AC-K was applied. Because real samples usually contain SAC and AC-K combined with aspartame (ASP), this interference was also included in the model. The procedure was successfully applied for SAC and AC-K simultaneous determination in sweeteners and fruit juice powders, without any separation step to remove ASP. The results were validated by using spiked samples, and the obtained recoveries were satisfactory.  相似文献   
82.
Illustrates continuity and discontinuity through comparison of a female patient's 2 consecutive courses of psychotherapy, the 1st (at age 24 yrs) using drive theory and the 2nd (at age 29 yrs) using the concepts of self psychology. Attention is centered on the manner in which continuity and discontinuity are experienced within the patient and then become a part of that person's ability to redirect, striving toward realizable goals. The manner is examined in which the weakened nuclear self experiences restored cohesion and a renewal of structure building through the response of the therapist to the selfobject needs expressed in the transference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
83.
Sorption of propylene oxide (PPO) by various commodities was studied at different concentrations during a 4-h exposure at 30 °C. A gas chromatograph was used to determine sorption of PPO applied at concentrations of 24, 49, 82 and 112 mg/l by 1±0.01 kg of narcissus bulbs, wheat, corn and cocoa beans in 2.64-l fumigation chambers. Results showed that for corn and cocoa beans the decrease in concentration during the first hour, that ranged from 40% to 76% of the initial concentration applied, was much greater than that for narcissus bulbs and wheat, which ranged from 25% to 41% of the initial concentration applied. PPO was initially taken up faster by corn and cocoa beans than by narcissus bulbs and wheat. The average sorption rate for each commodity increased with increasing initial concentration. The average sorption rate of PPO by corn and cocoa beans ranged from 14.9 to 48.6 ((mg/kg)/h) which was higher at each concentration than sorption by narcissus bulbs and wheat. In spite of the relatively high rates of sorption, the PPO residues among wheat, corn and cocoa beans immediately following a 4-h fumigation were well below the 300 ppm tolerance. These data show that PPO rapidly desorbed from the commodities under fumigation at 30 °C and at ambient atmospheric pressure.  相似文献   
84.
Ovarian granulosa cell tumors (GCTs) are thought to arise from cells of the ovarian follicle and comprise a rare entity of ovarian masses. We recently identified the G-protein-coupled estrogen receptor (GPER/GPR30) to be present in granulosa cells, to be regulated by gonadotropins in epithelial ovarian cancer and to be differentially expressed throughout folliculogenesis. Thus, supposing a possible role of GPER in GCTs, this study aimed to analyze GPER in GCTs. GPER immunoreactivity in GCTs (n = 26; n (primary diagnosis) = 15, n (recurrence) = 11) was studied and correlated with the main clinicopathological variables. Positive GPER staining was identified in 53.8% (14/26) of GCTs and there was no significant relation of GPER with tumor size or lymph node status. Those cases presenting with strong GPER intensity at primary diagnosis showed a significant reduced overall survival (p = 0.002). Due to the fact that GPER is regulated by estrogens, as well as gonadotropins, GPER may also be affected by endocrine therapies applied to GCT patients. Moreover, with our data supposing GPER to be associated with GCT prognosis, GPER might be considered as a possible confounder when assessing the efficacy of hormone-based therapeutic approaches in GCTs.  相似文献   
85.
In this work, the use of magnetic force microscopy (MFM) to acquire images of magnetic nanostructures in liquid environments is presented. Optimization of the MFM signal acquisition in liquid media is performed and it is applied to characterize the magnetic signal of magnetite nanoparticles. The ability for detecting magnetic nanostructures along with the well‐known capabilities of atomic force microscopy in liquids suggests potential applications in fields such as nanomedicine, nanobiotechnology, or nanocatalysis.  相似文献   
86.
The determination of radon-prone areas is usually based on indoor radon data and on the prognosis of the occurrence of houses exceeding the action level. However, the sample of houses in the survey must be representative and large enough, which is not easy to fulfill. Despite this, the determination of localities with high radon risk is useful not only for planning of indoor radon surveys, but also mainly for predicting the risk in newly built houses. There exist two more sources of data that can be used when assigning radon-related index to territories: soil gas radon measurements and gamma dose rate maps, both having their own inaccuracies. An attempt has been made to combine Czech indoor radon data, soil gas radon data and gamma dose rate maps for municipalities, where available. The radon-related index has been constructed by means of statistical analysis (linear regression). The equations found can be used for predicting the radon risk of the municipalities where the data sets are not large enough.  相似文献   
87.
88.
89.
90.
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