全文获取类型
收费全文 | 9471篇 |
免费 | 443篇 |
国内免费 | 82篇 |
专业分类
电工技术 | 194篇 |
综合类 | 90篇 |
化学工业 | 1640篇 |
金属工艺 | 220篇 |
机械仪表 | 299篇 |
建筑科学 | 362篇 |
矿业工程 | 13篇 |
能源动力 | 279篇 |
轻工业 | 497篇 |
水利工程 | 38篇 |
石油天然气 | 45篇 |
武器工业 | 2篇 |
无线电 | 1760篇 |
一般工业技术 | 1606篇 |
冶金工业 | 1755篇 |
原子能技术 | 88篇 |
自动化技术 | 1108篇 |
出版年
2023年 | 95篇 |
2022年 | 138篇 |
2021年 | 197篇 |
2020年 | 149篇 |
2019年 | 134篇 |
2018年 | 199篇 |
2017年 | 194篇 |
2016年 | 200篇 |
2015年 | 199篇 |
2014年 | 290篇 |
2013年 | 543篇 |
2012年 | 461篇 |
2011年 | 491篇 |
2010年 | 388篇 |
2009年 | 456篇 |
2008年 | 461篇 |
2007年 | 419篇 |
2006年 | 379篇 |
2005年 | 325篇 |
2004年 | 304篇 |
2003年 | 310篇 |
2002年 | 261篇 |
2001年 | 230篇 |
2000年 | 214篇 |
1999年 | 215篇 |
1998年 | 619篇 |
1997年 | 405篇 |
1996年 | 295篇 |
1995年 | 175篇 |
1994年 | 158篇 |
1993年 | 180篇 |
1992年 | 88篇 |
1991年 | 85篇 |
1990年 | 77篇 |
1989年 | 58篇 |
1988年 | 61篇 |
1987年 | 61篇 |
1986年 | 62篇 |
1985年 | 38篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 13篇 |
1981年 | 42篇 |
1980年 | 27篇 |
1979年 | 23篇 |
1978年 | 27篇 |
1977年 | 53篇 |
1976年 | 59篇 |
1974年 | 12篇 |
1971年 | 13篇 |
排序方式: 共有9996条查询结果,搜索用时 15 毫秒
91.
The effect of Pseudomonas aeruginosa infection on clinical parameters in steady-state bronchiectasis
PL Ho KN Chan MS Ip WK Lam CS Ho KY Yuen KW Tsang 《Canadian Metallurgical Quarterly》1998,114(6):1594-1598
STUDY OBJECTIVE: To investigate the effect of Pseudomonas aeruginosa infection on clinical parameters in Chinese patients with noncystic fibrosis and steady-state bronchiectasis. DESIGN: Prospective, cross-sectional clinicomicrobiological study with informed consent. SETTING: Consecutive outpatient recruitment from a specialist bronchiectasis respiratory clinic. PATIENTS: Outpatients (n = 100; 62 women; 55.1+/-16.7 years old; FEV1/FVC 1.4+/-0.7/2.1+/-0.9 L), who had stable respiratory symptoms for more than 3 weeks. MEASUREMENTS AND RESULTS: Respiratory pathogens isolated from the sputum were: Pseudomonas aeruginosa (33), Haemophilus influenzae (10), Moraxella catarrhalis (2), other Gram-negative bacilli (5), Streptococcus pneumoniae (6), Staphylococcus aureus (5), mycobacteria (3), and yeast (1). Clinical parameters in patients with positive isolation of P aeruginosa were compared with those without the organism in the sputum culture (non-P aeruginosa). In the P aeruginosa group, the FEV1/FVC ratio and sputum volume were lower (p < 0.005) and higher (p < 0.0001), respectively, than those of the non-P aeruginosa group. The FEV1/FVC ratio (< 60%) and sputum volume (grading > 5) were independently associated with a positive sputum isolation of P aeruginosa with odds ratios of 3.1 (confidence interval [CI] 1.2 to 8.4; p < 0.01) and 4.7 (CI 1.6 to 13.3; p < 0.001), respectively. CONCLUSIONS: P aeruginosa is the predominant respiratory pathogen isolated in the sputum of Chinese patients with steady-state bronchiectasis, and its isolation is associated with high sputum output (> or = 75th quartile) and moderately severe airflow obstruction (FEV1/FVC < 60%). 相似文献
92.
Lactation records (n = 2362) of 1402 crossbred cows in 22 cooperating dairy herds in southeastern Brazil were evaluated. Cows were mixtures of Zebu (Gir, Guzera, and unknown) and European breeding (mostly Holstein). Lactation milk yields were expressed as total, 3050-d, or deviated 305-d yields, either adjusted or unadjusted for days in milk (DIM). Mean DIM was 280. Arithmetic means unadjusted for DIM were 1942, 1666, and 5 kg per record. Milk yields of daughters from sires of 6/8 and 7/8 European breeds were higher than yields of daughters from sires of 5/8 European breeds when data were either adjusted or unadjusted for DIM. The differences associated with breed group of sire were only slightly reduced when records were adjusted for DIM. There was no evidence of a decline in milk yield as the fraction of European breeding of the sire increased from 6/8 to 7/8. For a given breed group of sire, whether the grandsire was purebred or crossbred had no detectable effect. These results should be useful in determining strategies for crossbreeding of dairy cows in tropical areas, particularly when crossbred sires are used. 相似文献
93.
KJ Barakat K Cheng WW Chan BS Butler TM Jacks KD Schleim DF Hora GJ Hickey RG Smith AA Patchett RP Nargund 《Canadian Metallurgical Quarterly》1998,8(11):1431-1436
A new class of potent, orally active phenyl piperazine-based GH secretagogues have been discovered from attempts to mimic the arrangement of the phenyl substituent in the spiroindanyl piperidine and spiroindoline sulfonamide privileged structures of 4 and 1, respectively. The best of these compounds, 18 (EC50 = 2.8 nM) is nearly as potent as MK-0677 for releasing GH from rat pituitary cells. 相似文献
94.
95.
96.
Meraj Talha Rauf Hafiz Tayyab Zahoor Saliha Hassan Arslan Lali M. IkramUllah Ali Liaqat Bukhari Syed Ahmad Chan Shoaib Umar 《Neural computing & applications》2021,33(17):10737-10750
Neural Computing and Applications - Lung cancer is a deadly disease if not diagnosed in its early stages. However, early detection of lung cancer is a challenging task due to the shape and size of... 相似文献
97.
We propose a novel fault detection and localization scheme for all-optical networks with the information of real-time data
traffic. Our adaptive fault localization framework is based on combining passive and proactive monitoring solutions, together
with adaptive management in two phases. Numerical results indicate that our proposed scheme has good scalability, in terms
of the number of fault monitors required. Also, we show that our framework allows more flexible network design, and requires
much less monitoring bandwidth when compared with the passive monitoring solutions. 相似文献
98.
This paper addresses the problem of designing robust tracking control for a class of uncertain wheeled mobile robots actuated by brushed direct current motors. This class of electrically‐driven mechanical systems consists of the robot kinematics, the robot dynamics, and the wheel actuator dynamics. Via the backstepping technique, an intelligent robust tracking control scheme that integrates a kinematic controller and an adaptive neural network‐based (or fuzzy‐based) controller is developed such that all of the states and signals of the closed‐loop system are bounded and the tracking error can be made as small as possible. Two adaptive approximation systems are constructed to learn the behaviors of unknown mechanical and electrical dynamics. The effects of both the approximation errors and the unmodeled time‐varying perturbations in the input and virtual‐input weighting matrices are counteracted by suitably tuning the control gains. Consequently, the robust control scheme developed here can be employed to handle a broader class of electrically‐driven wheeled mobile robots in the presence of high‐degree time‐varying uncertainties. Finally, a simulation example is given to demonstrate the effectiveness of the developed control scheme. 相似文献
99.
We predicted low perceived caregiver control over caregiving failure to be related to (a) coercive or abusive parenting and (b) affective reactions to "difficult" children. On the basis of a multidimensional scaling analysis of the Parent Attribution Test (Study 1), we constructed a scale (PCF) that assessed perceived balance of control over caregiving failure (attributed control to caregivers vs attributed control to children). In Study 2, we found low PCF to predict abusiveness and nonabusive coerciveness among mothers in counseling at a child abuse agency. Additionally, we found low PCF to predict experienced annoyance/irritation among unrelated mothers interacting with children at relatively high risk for abuse (compared with their lower-risk siblings). We interpreted results as demonstrating the potential importance of low perceived control as a moderator of negative affect in response to difficult children. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
100.
An improved version of Afek and Gafni's synchronous algorithm for distributed election in complete networks is given and anO(n) expected message complexity is shown.
M.Y. Chan received her Ph.D. in 1988 from the University of Hong Kong, and her M.S. and B.A. degrees in computer science from the University of California, San Diego in 1980 and 1981, respectively. She is currently an Assistant Professor at the University of Texas at Dallas.
Francis Y.L. Chin (S71-M76-SM85) received the B.Sc. degree in engineering science from the University of Toronto, Toronto, Canada, in 1972, and the M.S., M.A., and Ph.D. degrees in electrical engineering and computer science from Princeton University, New Jersey, in 1974, 1975, and 1976, respectively. Since 1975, he has taught at the University of Maryland, Baltimore Country, University of California, San Diego, University of Alberta, and Chinese University of Hong Kong. He is currently Head of the Department of Computer Science, University of Hong Kong. He has served as a program co-chairman of the 1988 International Conference on Computer Processing of Chinese and Oriental Languages (Toronto) and the International Computer Science Conference '88 (Hong Kong). His current research interests include algorithm design and analysis, parallel and distributed computing. 相似文献