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   2371篇
  免费   48篇
  国内免费   8篇
电工技术   7篇
综合类   7篇
化学工业   106篇
金属工艺   6篇
机械仪表   8篇
建筑科学   20篇
矿业工程   12篇
能源动力   15篇
轻工业   43篇
水利工程   2篇
石油天然气   6篇
武器工业   3篇
无线电   125篇
一般工业技术   62篇
冶金工业   1921篇
原子能技术   2篇
自动化技术   82篇
  2023年   3篇
  2022年   10篇
  2021年   19篇
  2020年   17篇
  2019年   13篇
  2018年   14篇
  2017年   15篇
  2016年   21篇
  2015年   15篇
  2014年   14篇
  2013年   16篇
  2012年   18篇
  2011年   36篇
  2010年   22篇
  2009年   20篇
  2008年   31篇
  2007年   22篇
  2006年   18篇
  2005年   25篇
  2004年   16篇
  2003年   20篇
  2002年   17篇
  2001年   19篇
  2000年   14篇
  1999年   63篇
  1998年   611篇
  1997年   349篇
  1996年   225篇
  1995年   133篇
  1994年   96篇
  1993年   104篇
  1992年   29篇
  1991年   29篇
  1990年   26篇
  1989年   16篇
  1988年   23篇
  1987年   24篇
  1986年   27篇
  1985年   18篇
  1983年   3篇
  1982年   10篇
  1981年   15篇
  1980年   15篇
  1979年   2篇
  1978年   5篇
  1977年   53篇
  1976年   107篇
  1975年   2篇
  1973年   3篇
  1955年   1篇
排序方式: 共有2427条查询结果,搜索用时 15 毫秒
1.
2.
Cases of isolated hepatic tuberculosis (TB) are rare. The diagnosis is often delayed or missed because of nonspecific symptoms and laboratory findings. Besides, the disease is extremely rare even in a country where TB is an alarming public health problem. This report demonstrates the difficulty in correctly diagnosing local hepatic TB. We report the case of a 62‐year‐old male patient with end‐stage renal disease treated with hemodialysis, who developed 2 months of abdominal distension and general anorexia, with hyperechoic hepatic lesions on ultrasound. Computed tomography suspected multiple liver tumors. The liver biopsy finally led to the diagnosis of TB of the liver without other involvements. We conclude that isolated hepatic TB is one of the rare forms of extrapulmonary TB in dialysis patients. A greater awareness of this rare clinical entity may prevent needless surgical interventions.  相似文献   
3.
Minds and Machines - To address the rising concern that algorithmic decision-making may reinforce discriminatory biases, researchers have proposed many notions of fairness and corresponding...  相似文献   
4.
A dual-mode ring bandpass filter with two pairs of capacitors has been designed. The capacitors are used to control the location of the even- and odd-mode frequencies independently, allowing weak coupling for narrow-band filter design with realizable capacitance values. Theoretical expressions have been derived for these frequencies. A 4% bandwidth bandpass filter centered at 1.9 GHz was designed and tested with good agreement between theoretical and measured results.  相似文献   
5.
6.
The relative importance of fat and lean tissue mass in determining bone mineral mass among postmenopausal women was examined in this 1-year longitudinal study. Fifty postmenopausal Caucasian women entered the study; 45 of them completed a 1-year follow-up. Dual-energy X-ray absorptiometry was employed for measuring total and regional bone mineral density (BMD) and bone mineral content (BMC), fat tissue mass (FTM), lean tissue mass (LTM), and body weight. Results from linear regression analysis using the cross-sectional data (n = 50) of the study indicated that LTM explained a larger percentage of variation in bone mineral mass than did FTM. FTM and LTM were found to be moderately correlated (r = 0.55); when FTM was entered in the same predicting regression models, LTM was a significant predictor (p < 0.05) of the total and regional BMC, but not BMD. The percent FTM (and inversely %LTM) was correlated with BMD and BMC, but significant correlation was primarily found only for total body BMD (or BMC). Weight was the best predictor of total body BMD and BMC. Longitudinally (n = 45), annual changes in both FTM and weight were significantly associated with annual changes in regional BMD after adjustment for initial bone mineral values (p < 0.05). We conclude that bone mineral mass is more closely related to LTM than to FTM, while annual changes in regional BMD are more closely correlated with changes in FTM in healthy postmenopausal women. Meanwhile, increased body weight is significantly associated with increased bone mineral mass.  相似文献   
7.
8.
9.
Minimum onset latency (Lmin) of single- and multiple-unit responses were mapped in the primary auditory cortex (AI) of barbiturate-anesthetized cats. Contralateral Lmin for multiple units was non-homogeneously distributed along the dorso-ventral/isofrequency axis of the AI. Responses with shorter latencies were more often located in the central, more sharply tuned region while longer latencies were more frequently encountered in the dorsal and ventral portions of the AI. For single units, a large scatter of Lmin values was found throughout the extent of the AI including cortical depth. The relationship between Lmin and previously reported spectral, intensity and temporal parameters was analyzed and revealed statistically significant correlations between minimum onset latency and the following response properties in some but not all studied animals: sharpness of tuning of a frequency response area 10 dB above threshold, broadband transient response, strongest response level, monotonicity of rate/level functions, dynamic range, and preferred frequency modulation sweep direction. This analysis suggests that Lmin is determined by several independent factors and that the prediction of Lmin based on relationships with other spectral and temporal response properties is inherently weak. The spatial distribution and the functional relationship between these response parameters may provide an important aspect of the time-based cortical representation of specific features in the animal's natural environment.  相似文献   
10.
Coronary artery calcification is a marker of atherosclerosis. Detection and quantification has previously been accomplished with electron-beam computed tomography (CT). Use of spiral CT for this application has been limited by cardiac motion. The authors evaluated a retrospective cardiac-gated postprocessing technique that necessitates no modification of scanner hardware or software. At spiral CT in 26 patients, motion artifact was reduced, coronary arteries were consistently visualized, and quantification of calcification could be performed in those patients with prominent deposits. Coronary artery calcification screening can therefore be offered in sites that have access to only spiral CT.  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