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   970篇
  免费   7篇
化学工业   15篇
机械仪表   1篇
能源动力   3篇
轻工业   6篇
无线电   3篇
一般工业技术   21篇
冶金工业   912篇
自动化技术   16篇
  2023年   2篇
  2022年   1篇
  2021年   1篇
  2017年   7篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   5篇
  2012年   3篇
  2011年   11篇
  2010年   2篇
  2009年   1篇
  2008年   3篇
  2007年   3篇
  2006年   1篇
  2005年   3篇
  2004年   1篇
  2003年   5篇
  2000年   3篇
  1999年   39篇
  1998年   310篇
  1997年   190篇
  1996年   95篇
  1995年   59篇
  1994年   39篇
  1993年   61篇
  1992年   7篇
  1991年   8篇
  1990年   4篇
  1989年   6篇
  1988年   10篇
  1987年   3篇
  1986年   3篇
  1985年   7篇
  1983年   1篇
  1982年   5篇
  1981年   5篇
  1980年   3篇
  1978年   4篇
  1977年   15篇
  1976年   42篇
  1975年   1篇
  1965年   2篇
  1956年   1篇
  1955年   1篇
排序方式: 共有977条查询结果,搜索用时 15 毫秒
101.
Clinically apparent thyroid nodules occur in about 5 percent of the population. Because most patients with thyroid nodules present initially to their primary care physician, family physicians should have a thorough understanding of the diagnosis and treatment of thyroid nodules. The history and physical examination may be helpful in detecting thyroid nodules but are not useful in predicting malignancy. Furthermore, laboratory studies, ultrasonography and nuclear medicine scans do not reliably differentiate between benign and malignant thyroid nodules. In most cases, fine-needle aspiration biopsy can accurately identify malignant thyroid nodules. Fine-needle aspiration biopsy is safe and can be performed in an office setting.  相似文献   
102.
Serine 167 has been identified by radiolabel and amino acid sequencing as the major estrogen-induced phosphorylation site on the human estrogen receptor (hER) from human MCF-7 mammary carcinoma cells. The phosphorylation of the hER on serine 167 was estrogen-dependent, increasing 4-fold upon estradiol treatment of MCF-7 cells and accounted for almost half of the total [32P]phosphate incorporated into the recombinant hER from Sf9 insect cells and the native hER from MCF-7 cells. Casein kinase II was found to phosphorylate the purified recombinant hER on serine 167 in vitro. In addition, estradiol binding enhanced by 2-fold the phosphorylation of the purified recombinant hER by casein kinase II in vitro. Western blot analysis and [32P]phosphate incorporation confirmed the presence of casein kinase II in Sf9 cells. These results demonstrate that the hER is phosphorylated on serine 167 by casein kinase II in a hormone-dependent manner.  相似文献   
103.
We developed gas chromatography-mass spectrometric methods for assaying the enrichment of 99 at.% [6,6-2H2]glucose and 30 at.% [U-13C6]glucose, although both tracers are mostly M + 2. 13C enrichment is determined either by the C-1 to C-5 fragment of glucose aldonitrile pentaacetate or by oxidation of glucose to glucarate. 2H enrichment is assayed as the difference between the 13C enrichment of glucarate and the 2H + 13C enrichment of glucose. The techniques, which were validated in in vivo experiments, are applicable to the determination of simultaneous or sequential measurements of the rate of glucose appearance before and after an intervention. They could also be applied to the simultaneous determination of (i) gluconeogenesis by incorporation of a 13C-labeled precursor into glucose and (ii) the rate of glucose appearance by [6,6-2H2]glucose infusion.  相似文献   
104.
Clean Technologies and Environmental Policy - In this paper, an optimal sizing of a grid-connected PV system to accommodate the load demands of a public building (i.e., Faculty of Sciences and...  相似文献   
105.
The adsorption of hydroquinone by metallic silver in the presence of a long chain alkylammonium quaternary salt was examined at three different pH values corresponding to the hydroquinone molecule, the mono- and the di-anion, and the results were correlated with those obtained from measurements of the development activity of these same species. The combined results indicate that a complex is formed of the hydroquinone di-anion and the quaternary salt which is readily adsorbed by silver, thus providing a substantial shortening of the induction period and acceleration of development.  相似文献   
106.
A rectangular negative branch off-axis hybrid resonator was coupled to a 10 kW class chemical oxygen-iodine laser. Resonator setup and alignment turned out to be straightforward. The extracted power was 6.6 kW and reached approximately 70% of the power for an optimized stable resonator. The divergence of the emitted laser beam in the unstable direction was lower than two times the diffraction limit. Experimentally measured margins for mirror misalignment were found in close agreement with numerical calculations.  相似文献   
107.
108.
Multiple causes, including various types of trauma, prolonged compression, muscle avulsions, burn, snake bites, high-pressure injection injuries, exercise, infection, bleeding, and intravenous drug infiltration, have been reported to lead to the development of a compartment syndrome in the upper extremity. Awareness of the different causes and risks of compartment syndrome should facilitate early diagnosis and prompt treatment to help avoid the development of serious sequelae such as Volkmann's ischemic contracture. A review of the various reports of upper extremity compartment syndromes and classification systems is presented to assist in the understanding of this condition's development.  相似文献   
109.
110.
Click-evoked auditory brainstem responses were recorded in a prosimian primate, the bush baby (Otolemur garnettii), before and after depletion of serotonin (by systemic injection of para-chlorophenylalanine; pCPA) and up to 20 days after discontinuing pCPA injections (during the recovery of serotonin). Biphasic 100 micros clicks were presented at five repetition rates (13.2, 33.2, 53.2, 73.2, and 93.2 clicks/s; RATE) and sound pressure levels (SPL) were varied in 10 dB steps from 120-60 dB SPL peak equivalent. Absolute latencies of vertex-positive peaks I, III, IV, and V were measured from click onset. The latencies from each wave were statistically analyzed with a two-way analysis of variance using either RATE or SPL (but not both) and TIME AFTER pCPA as independent variables. Prior to pCPA, brainstem response latencies increased as a function of both decreasing SPL and increasing RATE. After pCPA, these normal increases in wave latency increased even more, particularly in response to high click rates. After pCPA was discontinued, measurements taken at weekly intervals indicated that latencies decreased after 1 week, increased to the highest values recorded after 2 weeks, and returned to normal after 3 weeks. These dynamic changes were interpreted to be the result of postsynaptic receptor up-regulation during the 10 days of continuous pCPA administration. These results suggest that serotonin plays an important role in sensory processing at the cellular level and, tonically, facilitates the auditory brainstem response to sound.  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