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   1637篇
  免费   1篇
电工技术   11篇
化学工业   20篇
金属工艺   4篇
机械仪表   5篇
建筑科学   6篇
矿业工程   1篇
能源动力   12篇
轻工业   11篇
石油天然气   1篇
无线电   101篇
一般工业技术   106篇
冶金工业   1301篇
原子能技术   3篇
自动化技术   56篇
  2022年   3篇
  2016年   6篇
  2014年   3篇
  2013年   6篇
  2012年   4篇
  2011年   15篇
  2010年   5篇
  2009年   8篇
  2008年   11篇
  2007年   18篇
  2006年   22篇
  2005年   14篇
  2004年   14篇
  2003年   16篇
  2002年   25篇
  2001年   10篇
  2000年   14篇
  1999年   41篇
  1998年   347篇
  1997年   212篇
  1996年   142篇
  1995年   74篇
  1994年   77篇
  1993年   86篇
  1992年   25篇
  1991年   23篇
  1990年   16篇
  1989年   32篇
  1988年   31篇
  1987年   24篇
  1986年   28篇
  1985年   30篇
  1984年   6篇
  1983年   7篇
  1982年   8篇
  1981年   10篇
  1980年   19篇
  1979年   5篇
  1978年   7篇
  1977年   45篇
  1976年   97篇
  1975年   8篇
  1974年   4篇
  1973年   7篇
  1971年   3篇
  1969年   5篇
  1968年   3篇
  1964年   2篇
  1959年   2篇
  1955年   3篇
排序方式: 共有1638条查询结果,搜索用时 15 毫秒
71.
An 8-Gb/s 0.3-μm CMOS transceiver uses multilevel signaling (4-PAM) and transmit preshaping in combination with receive equalization to reduce intersymbol interference due to channel low-pass effects. High on-chip frequencies are avoided by multiplexing and demultiplexing the data directly at the pads. Timing recovery takes advantage of a novel frequency acquisition scheme and a linear phase-locked loop that achieves a loop bandwidth of 35 MHz, phase margin of 50°, and capture range of 20 MHz without a frequency acquisition aid. The transmitted 8 Gb/s data are successfully detected by the receiver after a 10-m coaxial cable. The 2×2 mm2 chip consumes 1.1 W at 8 Gb/s with a 3-V supply  相似文献   
72.
Decoder design involves choosing the optimal circuit style and figuring out their sizing, including adding buffers if necessary. The problem of sizing a simple chain of logic gates has an elegant analytical solution, though there have been no corresponding analytical results until now which include the resistive effects of the interconnect. Using simple RC models, we analyze the problem of optimally sizing the decoder chain with RC interconnect and find the optimum fan-out to be about 4, just as in the case of a simple buffer chain. As in the simple buffer chain, supporting a fan-out of 4 often requires noninteger number of stages in the chain. Nevertheless, this result is used to arrive at a tight lower bound on the delay of a decoder. Two simple heuristics for sizing of real decoder with integer stages are examined. We evaluate a simple technique to reduce power, namely, reducing the sizes of the inputs of the word drivers, while sizing each of the subchains for maximum speed, and find that it provides for an efficient mechanism to trade off speed and power. We then use the RC models to compare different circuit techniques in use today and find that decoders with two input gates for all stages after the predecoder and pulse mode circuit techniques with skewed N to P ratios have the best performance  相似文献   
73.
74.
Bromine-76 is potentially useful as a radiolabel for monoclonal antibodies (MAbs) in PET imaging. The purpose of the present study was to evaluate the 76Br-labeled anticarcinoembryonic antigen (-CEA) MAb 38S1 as a tumor imaging agent in an experimental tumor model and to study the pharmacokinetics of 76Br-38S1 in comparison with 125I-38S1. METHODS: Nude rats carrying human colon carcinoma xenografts were co-injected with directly labeled 76Br-38S1 and 125I-38S1. Biodistribution of labeled 38S1 was monitored for 4 days after administration, in the case of 76Br activity, including PET imaging. In addition, catabolism of radiolabeled MAbs was analyzed by gel filtration chromatography of blood plasma and homogenized tissues. RESULTS: Tumor sites could be readily identified by PET imaging from 46 hr after administration of 76Br-38S1 and onwards. The concentration of 76Br activity in tumors, blood and most normal tissues was higher than the corresponding 125I concentration at all time points. This was mainly due to catabolism of radiolabeled MAb, resulting in free radiohalides, of which 76Br- was retained in contrast to the rapidly excreted 125I- ion. CONCLUSION: Bromine-76-labeled anti-CEA MAbs may be applied for experimental tumor imaging with PET.  相似文献   
75.
To evaluate the differences between the outcome of elderly patients with severe injuries and that of their contemporaries with a less severe injury, we reviewed 42 severely injured elderly patients and compared them with 76 patients with a femoral neck fracture. We analysed the influence of injury severity and host factors (age, sex and pre-injury medical status) on outcome. The in-hospital mortality rate was 31 per cent in the severely injured patients and 3 per cent in those with a femoral neck fracture. Home was the main discharge destination in the severely injured elderly (34 per cent) and a nursing home in patients with a femoral neck fracture (65 per cent). Functional outcome 1 year after injury was better in the severely injured elderly group. Long-term survival was mainly determined by host factors and not by injury severity. Physicians and policy makers should be careful in predicting the outcome of elderly injured patients merely on the basis of injury severity, because host factors are of greater importance.  相似文献   
76.
77.
78.
79.
Of 101 women, 15-50 years of age, presenting with vaginal discharge, 34 had bacterial vaginosis and were randomly assigned to a seven-day course of oral treatment with either erythromycin (0.5 g b.i.d.) or metronidazole (0.4 g b.i.d.) in a single-blind, cross-over study. Treatment failure (> or = three clinical signs of bacterial vaginosis) occurred in 13 (81%) of 16 patients given erythromycin, as compared with three (17%) of 18 women treated with metronidazole (p < 0.001). Persistence of Gardnerella vaginalis, Mobiluncus species and/or Mycoplasma hominis was found in 14 of 16 patients treated with erythromycin, and in four of 16 patients treated with metronidazole. Treatment with metronidazole was successful (< or = two clinical signs of bacterial vaginosis) in eight of 10 cases of erythromycin treatment failure. Neither of two cases of metronidazole treatment failure was cured with erythromycin. At three-month follow-up of 31 women, persistence or recurrence of bacterial vaginosis was diagnosed in 11 cases (36%).  相似文献   
80.
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