全文获取类型
收费全文 | 5277篇 |
免费 | 104篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 43篇 |
综合类 | 4篇 |
化学工业 | 878篇 |
金属工艺 | 89篇 |
机械仪表 | 78篇 |
建筑科学 | 282篇 |
矿业工程 | 15篇 |
能源动力 | 188篇 |
轻工业 | 493篇 |
水利工程 | 36篇 |
石油天然气 | 13篇 |
无线电 | 391篇 |
一般工业技术 | 640篇 |
冶金工业 | 1586篇 |
原子能技术 | 41篇 |
自动化技术 | 608篇 |
出版年
2021年 | 53篇 |
2020年 | 45篇 |
2019年 | 60篇 |
2018年 | 47篇 |
2017年 | 58篇 |
2016年 | 81篇 |
2015年 | 68篇 |
2014年 | 83篇 |
2013年 | 244篇 |
2012年 | 151篇 |
2011年 | 216篇 |
2010年 | 170篇 |
2009年 | 177篇 |
2008年 | 189篇 |
2007年 | 175篇 |
2006年 | 168篇 |
2005年 | 154篇 |
2004年 | 130篇 |
2003年 | 120篇 |
2002年 | 143篇 |
2001年 | 93篇 |
2000年 | 84篇 |
1999年 | 110篇 |
1998年 | 224篇 |
1997年 | 181篇 |
1996年 | 125篇 |
1995年 | 113篇 |
1994年 | 129篇 |
1993年 | 115篇 |
1992年 | 81篇 |
1991年 | 59篇 |
1990年 | 80篇 |
1989年 | 63篇 |
1988年 | 73篇 |
1987年 | 61篇 |
1986年 | 70篇 |
1985年 | 87篇 |
1984年 | 90篇 |
1983年 | 64篇 |
1982年 | 71篇 |
1981年 | 69篇 |
1980年 | 59篇 |
1979年 | 55篇 |
1978年 | 45篇 |
1977年 | 78篇 |
1976年 | 89篇 |
1975年 | 72篇 |
1974年 | 42篇 |
1973年 | 52篇 |
1972年 | 45篇 |
排序方式: 共有5385条查询结果,搜索用时 15 毫秒
31.
Many companies are using Just-In-Time (JIT) control systems in their mixed-model multi-level production facilities. When scheduling these facilities the most important objective is to keep a constant rate of usage for every part used by the system. In this paper a mathematical model for scheduling these facilities is studied and techniques for determining good schedules are developed. Procedures for solving very large problems are given. 相似文献
32.
Tucker Joan S.; Friedman Howard S.; Tsai Catherine M.; Martin Leslie R. 《Canadian Metallurgical Quarterly》1995,10(1):3
Models of the relations between contact with pets and better health are examined in an archival prospective study using data derived from the longitudinal study initiated by Terman in 1921 (current N?=?343 men, 300 women) . In survival analyses of documented longevity, playing with pets in 1977 (M age?=?67 years) was not associated with mortality risk through 1991 for the total sample nor for those who were unmarried or those who were less satisfied with their human relationships. Playing with pets was not associated with health-prone attributes or healthy behaviors such as personality, social ties, education, and smoking. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
33.
Capacity and power control issues are considered for urban CDMA microcells that operate on channels characterized by log-normal shadowing and Nakagami fading. The effects of fading on the desired and interfering signals, variations in the shadow standard deviation, imperfect power control, and the requiredE
b
/N
o
for satisfactory link operation are investigated. It is shown that the reverse channel is relatively insensitive, and the forward channel very sensitive, to shadow and fading variations. Power control error is shown to significantly degrade reverse channel capacity. Twobiased forward channel power control strategies are introduced to enhance existing unbiasedbalancing forward channel power control algorithms.This research has been supported by BNR Inc. 相似文献
34.
35.
36.
A method for predicting the long-term performance of solar energy systems, based on the analysis of system performance for one particular day—the typical meteorological day (TMD)—is presented. The TMD is constructed from the cumulative time distribution of insolation values on the collector aperture. The TMD method requires little calculational effort and a small data base relative to standard yearly computer simulations. Good agreement is found between the predictions of the new method and the corresponding results of the
-f-chart method. The TMD method is of particular value for cases that may often be treated inaccurately by simple calculational methods: (1) high threshold problems; (2) systems with short response times (e.g., due to small storage); and (3) systems in which collectors other than flat plates are used (the method is applicable to all solar collector types). 相似文献
37.
Carl A. Soderstrom Patricia C. Dischinger Gordon S. Smith J.Richard Hebel David R. McDuff David A. Gorelick Timothy J. Kerns Shiu M. Ho Kathleen M. Read 《Accident; analysis and prevention》1997,29(6):715-721
A structured in-depth interview employing standardized criteria was used to determine the prevalence of lifetime and current alcohol dependence (alcoholism) in unselected consecutive patients admitted to a regional Level I trauma center. Of 629 patients, 157 (25.0%) were current alcoholics at the time of injury. An additional 87 (13.8%) were diagnosed as lifetime non-current alcoholics. There was no significant difference in the rates of current alcohol dependence among patients injured in vehicular crashes (23.5%), other unintentional trauma victims (29.3%), and those injured as a result of violence (24.6%). Of BAC + (blood alcohol concentration positive) patients, 54.5% were current alcoholics. However, 14.4% of alcohol-negative patients were also diagnosed as alcohol dependent. 相似文献
38.
Kallie Christopher S.; Schrater Paul R.; Legge Gordon E. 《Canadian Metallurgical Quarterly》2007,33(1):183
Walking without vision results in veering, an inability to maintain a straight path that has important consequences for blind pedestrians. In this study, the authors addressed whether the source of veering in the absence of visual and auditory feedback is better attributed to errors in perceptual encoding or undetected motor error. Three experiments had the following results: No significant differences in the shapes of veering trajectories were found between blind and blindfolded participants; accuracy in detecting curved walking paths was not correlated with simple measures of veering behavior; and explicit perceptual cues to initial walking direction did not reduce veering. The authors present a model that accounts for the major characteristics of participants' veering behavior by postulating 3 independent sources of undetected motor error: initial orientation, consistent biases in step direction, and, most important, variable error in individual steps. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
Analytic expressions are derived for the angular acceptance function of two-dimensional compound parabolic concentrator solar collectors (CPC's) of arbitrary degree of truncation. Taking into account the effect of truncation on both optical and thermal losses in real collectors, we also evaluate the increase in monthly and yearly collectible energy. Prior analyses that have ignored the correct behavior of the angular acceptance function at large angles for truncated collectors are shown to be in error by 0–2% in calculations of yearly collectible energy for stationary collectors. 相似文献
40.