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   1711篇
  免费   12篇
电工技术   3篇
化学工业   32篇
金属工艺   2篇
机械仪表   7篇
建筑科学   5篇
能源动力   1篇
轻工业   31篇
水利工程   1篇
石油天然气   3篇
无线电   41篇
一般工业技术   36篇
冶金工业   1547篇
原子能技术   1篇
自动化技术   13篇
  2019年   2篇
  2018年   2篇
  2017年   10篇
  2016年   4篇
  2015年   2篇
  2014年   3篇
  2013年   4篇
  2012年   8篇
  2011年   5篇
  2010年   7篇
  2009年   5篇
  2008年   3篇
  2007年   11篇
  2006年   9篇
  2005年   2篇
  2004年   12篇
  2003年   8篇
  2002年   2篇
  2001年   4篇
  2000年   4篇
  1999年   30篇
  1998年   426篇
  1997年   288篇
  1996年   157篇
  1995年   115篇
  1994年   84篇
  1993年   99篇
  1992年   19篇
  1991年   13篇
  1990年   25篇
  1989年   22篇
  1988年   20篇
  1987年   17篇
  1986年   10篇
  1985年   6篇
  1984年   3篇
  1983年   4篇
  1982年   5篇
  1981年   12篇
  1980年   23篇
  1979年   2篇
  1978年   4篇
  1977年   60篇
  1976年   135篇
  1975年   5篇
  1974年   7篇
  1973年   4篇
  1972年   5篇
  1970年   3篇
  1955年   2篇
排序方式: 共有1723条查询结果,搜索用时 787 毫秒
81.
Fibroblast growth factor receptor (FGFR) activation leads to receptor autophosphorylation and increased tyrosine phosphorylation of several intra cellular proteins. We have previously shown that autophosphorylated tyrosine 766 in FGFR1 serves as a binding site for one of the SH2 domains of phospholipase Cy and couples FGFR1 to phosphatidylinositol hydrolysis in several cell types. In this report, we describe the identification of six additional autophosphorylation sites (Y-463, Y-583, Y-585, Y-653, Y-654 and Y-730) on FGFR1. We demonstrate that autophosphorylation on tyrosines 653 and 654 is important for activation of tyrosine kinase activity of FGFR1 and is therefore essential for FGFR1-mediated biological responses. In contrast, autophosphorylation of the remaining four tyrosines is dispensable for FGFR1-mediated mitogen-activated protein kinase activation and mitogenic signaling in L-6 cells as well as neuronal differentiation of PC12 cells. Interestingly, both the wild-type and a mutant FGFR1 (FGFR1-4F) are able to phosphorylate Shc and an unidentified Grb2-associated phosphoprotein of 90 kDa (pp90). Binding of the Grb2/Sos complex to phosphorylated Shc and pp90 may therefore be the key link between FGFR1 and the Ras signaling pathway, mito-genesis, and neuronal differentiation.  相似文献   
82.
83.
84.
85.
The AA. investigated the frequency of antibodies against Toxoplasma gondii in 426 women with repeated abortions, perinatal mortality and malformed newborns. They showed on the whole a low incidence even if they demonstrated a high incidence (77.7%) of antibodies in women with malformed newborns. The meaning of the observations are briefly discussed.  相似文献   
86.
Urinary metabolites and the pharmacokinetics of radioactivity derived from 14C-metronidazole (14C-MTZ) were determined after intravenous (iv) or intravaginal (ivg) administration of 10 mg/kg to adult rats. Following iv or ivg administration, the disappearance of 14C from blood followed the kinetics of a two-compartment open-system model. The blood half-lives of 14C during the beta-phase were 10.9 +/- 1.6 and 13.6 +/- 4.2 hr, after iv and ivg administration, respectively. After ivg application, the MTZ-derived radioactivity was detected in tail blood at 5 min, peaked at 1 hr, declined rapidly to 6 hr and more slowly thereafter. The vaginal absorption half-life of 14C-MTZ was 0.28 +/- 0.09 hr. About 12% of the administered dose remained in the vagina after 1 hr and 1.5% after 24 hr. At 24 hr, the tissue distribution and concentration of 14C were similar in iv and ivg dosed rats, the highest 14C concentration being present in the kidneys and lowest in the fat. The percentages of the dose excreted in 24 hr in the urine and feces were 58 and 15 after iv administration, compared to 37 and 40 after the ivg route, respectively. Unchanged 14C-MTZ and five of its metabolites were detected in the urine irrespective of the route of administration. The results show that metronidazole is rapidly absorbed through the vaginal mucosa of the rat and the metabolism and excretion of this chemotherapeutic agent are influenced by the route of administration.  相似文献   
87.
88.
Kunnil J  Swartz B  Reinisch L 《Applied optics》2004,43(28):5404-5409
Fluorescence has been suggested as a method with which to detect and identify bacterial spores. To better understand the nature of the fluorescence signal, we observed the intrinsic steady-state fluorescence and phosphorescence spectra of Bacillus globigii (BG) in both dried and aqueous forms. In vitro, dried, and suspension forms of BG were measured at room temperature in 300-600-nm excitation wavelengths. Also, the phosphorescence of dry BG spores was measured at room temperature at 300-600-nm excitation wavelengths. The wet BG spores exhibited a strong maximum in their fluorescence spectrum, with the peak excitation wavelength near 300 nm and emission wavelength near 400 nm. When the BG was dried, this peak shifted to an approximately 450-nm excitation maximum and an 500-nm emission maximum. The difference between the wet and the dry spore fluorescence spectra cannot be explained by the phosphorescence of the dry spores. Other changes must take place when the spores are wet to account for the large changes observed in the spectrum.  相似文献   
89.
The effect of variation in dietary ascorbic acid on surgically induced osteoarthritis was examined in the stifle joints of guniea pigs. Two different surgical procedures were used to induce osteoarthritis in the right stifle joint of these animals. Guinea pigs were maintained either on a high (150 mg/day) or low (2.4 mg/day) dietary intake of vitamin C. Regardless of the surgical procedure used to induce osteoarthritis, the animals maintained on the high level of vitamin C consistently showed severe joint damage than animals on the low level of the vitamin.  相似文献   
90.
Reviews the book, Aesthetics and Psychobiology by D. E. Berlyne (see record 1973-00821-000). Progress in the aesthetic disciplines has been at a snail's pace. Berlyne charges six factors with having impeded advance: the belief in art as a supernatural phenomenon, the failure to separate factual from normative questions, the conception of art as a unitary phenomenon, the habit of treating art in isolation from nonartistic forms of behavior, the preoccupation with uniqueness in aesthetic taste, and the concentration on verbal judgments in aesthetic work. But the future looks brighter, due primarily to the following developments: (1) the rise of information theory, which provides procedures for rigorously analyzing some of the features of stimulus patterns that most concern aesthetics, (2) recent empirical and theoretical contributions in both psychology and neurophysiology to the understanding of pleasure and arousal, and (3) findings bearing on the nature of exploratory behavior, both in animals and humans, particularly as these teach the motivational importance of such elements as complexity, novelty and uncertainty, so-called "collative" variables, that "seem to be identifiable with the irreducibly essential ingredients of art and of whatever else is aesthetically appealing" (viii). The principal aim of Berlyne's book is to establish the ground gained in these three areas, compare it to the contributions made by earlier workers, and effectuate "a provisional synthesis that will at least bring key problems to the fore" (viii). It is a formidable task. Inevitably, the effort fares better in some assignments than others. Ironically, what discrepancies in quality do exist would probably project less were Berlyne not so knowledgeable about his subject matter. He is, quite obviously, in the tradition of those "cultured gentlemen" with whom he is wont to populate the early history of psychological science. Parenthetically, one suspects that he could supplement the present work with a very creditable companion volume in the philosophy of aesthetics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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