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   2308篇
  免费   2篇
  国内免费   1篇
综合类   2篇
化学工业   20篇
金属工艺   3篇
机械仪表   4篇
建筑科学   3篇
能源动力   1篇
轻工业   22篇
石油天然气   1篇
无线电   7篇
一般工业技术   8篇
冶金工业   2223篇
自动化技术   17篇
  2021年   1篇
  2020年   1篇
  2018年   1篇
  2016年   2篇
  2014年   10篇
  2013年   10篇
  2012年   6篇
  2011年   4篇
  2010年   8篇
  2009年   7篇
  2008年   3篇
  2007年   2篇
  2006年   1篇
  2004年   3篇
  2003年   5篇
  2002年   5篇
  2001年   3篇
  2000年   1篇
  1999年   72篇
  1998年   747篇
  1997年   423篇
  1996年   240篇
  1995年   137篇
  1994年   117篇
  1993年   137篇
  1992年   11篇
  1991年   21篇
  1990年   27篇
  1989年   24篇
  1988年   34篇
  1987年   33篇
  1986年   15篇
  1985年   24篇
  1983年   3篇
  1982年   8篇
  1981年   7篇
  1980年   16篇
  1978年   3篇
  1977年   43篇
  1976年   90篇
  1975年   2篇
  1970年   1篇
  1966年   1篇
  1963年   2篇
排序方式: 共有2311条查询结果,搜索用时 14 毫秒
21.
Cognitive accounts of panic predict that panic disorder patients will be particularly prone to misinterpret autonomic sensations. Several studies have produced results consistent with this prediction, but each is open to alternative interpretation. To clarify matters, 2 studies administered the Body Sensations Interpretation Questionnaire (BSIQ) to panic patients and controls. Panic patients were more likely to interpret ambiguous autonomic sensations as signs of immediately impending physical or mental disaster and were more likely than other anxiety disorder patients and nonpatients to believe these interpretations. In a 3rd study, a brief version of the BSIQ was shown to have satisfactory test-retest reliability, to change with treatment, and to discriminate treatments that varied in their effects on panic.  相似文献   
22.
采用微波辐射辅助柠檬酸络合法制备Ho3+/Tm3+/Yb3+共掺杂CaWO4纳米晶升频转换荧光粉。将柠檬酸络合物前驱体在300~700°C热处理3 h。Ho3+/Tm3+/Yb3+共掺杂CaWO4C在400°C时开始结晶,在600°C时结晶完成。经600°C热处理的Ho3+/Tm3+/Yb3+共掺杂CaWO4主要呈球形,且形态均匀。在980 nm的激光激发下,Ho3+/Tm3+/Yb3+共掺杂CaWO4纳米晶出现肉眼可见的明亮的白色升频转换发射,这种现象来自Tm3+的475 nm蓝光发射以及Ho3+的543 nm绿光和651 nm红光发射。通过调整Tm3+和Ho3+的浓度可以控制Ho3+/Tm3+/Yb3+共掺杂CaWO4的CIE色度图从冷到暖白色之间变化。讨论了Tm3+和Ho3+浓度对升频转换光性能的影响以及与激光泵功率相关的影响机制。  相似文献   
23.
Social comparisons entail not only information about one’s standing in a social group (intragroup or local comparison) but also information about the standing of the group in comparison to other groups (intergroup or general comparison). In Studies 1–3, the authors explored the relative impact of intergroup and intragroup comparisons on self-evaluations and affect. While intragroup comparison feedback consistently impacted self-evaluations and affect, intergroup comparison information exerted a significant impact only when intragroup comparison information was unavailable. The authors refer to this general tendency as contextual neglect. Studies 4 and 5 showed that contextual neglect is due primarily to the fact that low-level, local comparison information displaces or supersedes the effect of higher level, general comparison data and that people clearly recognize the superior diagnosticity of higher level comparisons while continuing to rely on small, haphazard sample data to evaluate their ability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
24.
25.
OBJECTIVE: To compare the efficacy of IUI husband in natural versus FSH stimulated cycles. DESIGN: Prospective, controlled study. MATERIALS AND METHODS: IUI were performed in 57 infertile couples with natural cycles, and in 16 under FSH and GnRH stimulation (Short protocol). In stimulated patients also hCG and hydrogesteron were given. Indication in both groups was idiopathic infertility. Duration of infertility and the age were comparable. Semen preparation and ovarian monitoring were the same in 2 groups. RESULTS: Three pregnancies in 57 natural IUI cycles (5.3%) and 5 out of 16 cycles in stimulated women (31.2% per cycle-with one triple pregnancy). CONCLUSION: In couples with idiopathic infertility FSH stimulation significantly increases rate of pregnancy and multiple gestation.  相似文献   
26.
Mammalian cells are hypersensitive to very low doses of X-rays (< 0.2 Gy), a response which is followed by increased radioresistance up to 1 Gy. Increased radioresistance is postulated to be a response to DNA damage, possibly single-strand breaks, and it appears to be a characteristic of low linear energy transfer (LET) radiation. Here we demonstrate a correspondence between the extent of the increased radioresistance and linear energy transfer of 250 kVp X-rays and plateau and Bragg peak negative pi-mesons. The results support our hypothesis since the size of the increased radioresistant response appears to correspond to the number of radiation induced single-strand breaks. Furthermore, since survival prior to the increased radioresistant response (< 0.2 Gy) was LET-independent, these data support the notion that the increased radioresistant response may dictate the overall survival response to higher doses. However, while these data provide further circumstantial evidence for the involvement of DNA strand breaks in the triggering of increased radioresistance, more direct conclusions cannot be made. The data are not accurate enough to detect structure in the single-strand break profiles, the production of single-strand breaks being apparently linear with dose.  相似文献   
27.
28.
29.
A high capacity gel filtration system was developed with the purpose of isolating factor VIII (FVIII) and von Willebrand factor (vWF) directly from plasma in significantly higher yields than obtained by cryoprecipitation, the technique most commonly used to recover FVIII-vWF from human plasma. After laboratory-scale gel filtration of plasma, a FVIII-containing fraction was collected containing about 90% of FVIII in the applied plasma and with almost tenfold higher purity than that obtained by cryoprecipitation. The gel filtration step has been scaled up for use as the initial step in the manufacturing process for a FVIII preparation (Nordiate).  相似文献   
30.
Three cheetahs (Acinonyx jubatus) had a clinical history of chronic spiral bacteria-associated gastritis and three cheetahs had no clinical history of gastritis. Gastric biopsies were obtained from all six cheetahs prior to treatment for gastritis and 3 wk and 1 yr posttreatment. The cheetahs were treated with tetracycline hydrochloride 500 mg p.o. q.i.d., metronidazole 250 mg p.o. q.i.d., and bismuth subsalicylate 300 mg p.o. q.i.d. Each drug was administered concurrently for 7 days. Following this treatment, each cheetah was maintained on 300 mg bismuth subsalicylate p.o. s.i.d. for 1 yr. The three cheetahs with a history of gastritis were culture positive for Helicobacter acinonyx and remained positive during the entire study. The three cheetahs with no clinical history of gastritis were culture negative for H. acinonyx, but gastric biopsies revealed Gastrospirillum-like bacteria (tentatively named Helicobacter heilmannii) pretreatment. Gastric biopsies were negative for H. heilmannii on subsequent examinations. Although the treatment did not eradicate H. acinonyx, it did provide symptomatic relief from the vomiting, anorexia, and weight loss associated with clinical gastritis. The use of endoscopically guided gastric mucosal biopsies for urease testing and histopathologic examination of Warthin-Starry-stained sections is a sensitive and specific method of diagnosing spiral bacteria-associated gastritis. Treatment of spiral bacteria-associated gastritis in cheetahs should include the rational use of antibiotics (tetracycline or amoxicillin and metronidazole), bismuth compounds, and omeprazole and evaluation of husbandry methods to reduce stress.  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