全文获取类型
收费全文 | 35417篇 |
免费 | 5511篇 |
国内免费 | 2155篇 |
专业分类
电工技术 | 4086篇 |
技术理论 | 2篇 |
综合类 | 3561篇 |
化学工业 | 3093篇 |
金属工艺 | 1454篇 |
机械仪表 | 2577篇 |
建筑科学 | 4083篇 |
矿业工程 | 2304篇 |
能源动力 | 2235篇 |
轻工业 | 3768篇 |
水利工程 | 2011篇 |
石油天然气 | 2867篇 |
武器工业 | 474篇 |
无线电 | 2623篇 |
一般工业技术 | 2524篇 |
冶金工业 | 1985篇 |
原子能技术 | 401篇 |
自动化技术 | 3035篇 |
出版年
2024年 | 324篇 |
2023年 | 832篇 |
2022年 | 1531篇 |
2021年 | 1767篇 |
2020年 | 1888篇 |
2019年 | 1410篇 |
2018年 | 1245篇 |
2017年 | 1456篇 |
2016年 | 1562篇 |
2015年 | 1613篇 |
2014年 | 2407篇 |
2013年 | 2167篇 |
2012年 | 2643篇 |
2011年 | 2757篇 |
2010年 | 2099篇 |
2009年 | 2084篇 |
2008年 | 1715篇 |
2007年 | 2098篇 |
2006年 | 1866篇 |
2005年 | 1573篇 |
2004年 | 1332篇 |
2003年 | 1161篇 |
2002年 | 970篇 |
2001年 | 793篇 |
2000年 | 725篇 |
1999年 | 600篇 |
1998年 | 418篇 |
1997年 | 323篇 |
1996年 | 299篇 |
1995年 | 281篇 |
1994年 | 226篇 |
1993年 | 179篇 |
1992年 | 134篇 |
1991年 | 101篇 |
1990年 | 90篇 |
1989年 | 80篇 |
1988年 | 48篇 |
1987年 | 43篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1980年 | 15篇 |
1976年 | 9篇 |
1966年 | 7篇 |
1964年 | 14篇 |
1962年 | 6篇 |
1959年 | 11篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
22.
A. Alt Dr.‐Ing. H. Mertens U. Arz L. Blessing C. Berger 《Materialwissenschaft und Werkstofftechnik》2007,38(5):402-409
High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence. 相似文献
23.
In its policy rationale for evidence-based practice in psychology (EBPP), the APA Presidential Task Force on Evidence-Based Practice (see record 2006-05893-001) claims to have constituted itself with "scientists and practitioners from a wide range of perspectives and traditions, reflecting the diverse perspectives within the field" (p. 273). We applaud this attention to diversity but contend that an entire perspective of the debate was omitted in the Task Force's newly approved policy and its underlying report. The failure to consider a philosophy of science perspective led the Task Force to make a number of epistemological assumptions that are not based on evidence or rationale and that thus violate the very spirit of evidence-based decision making. In this comment, we reveal a few of these assumptions and discuss their detrimental consequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
24.
Hitsman Brian; Borrelli Belinda; McChargue Dennis E.; Spring Bonnie; Niaura Raymond 《Canadian Metallurgical Quarterly》2003,71(4):657
The authors conducted a meta-analysis of published studies to (a) evaluate the premise that a history of major depression is associated with failure to quit smoking and (b) identify factors that moderate the relationship between history of depression and cessation outcome. Fifteen studies met the selection requirements and were coded for various study methodology and treatment characteristics. DSTAT was used to calculate individual study effect sizes, determine the mean effect size across studies. and test for moderator effects. No differences in either short-term (≤ 3 months) or long-term abstinence rates (≥ 6 months) were observed between smokers positive versus negative for history of depression. Lifetime history of major depression does not appear to be an independent risk factor for cessation failure in smoking cessation treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
用单透镜变换由多模光纤出射的大功率Nd:YAG激光束的特性 总被引:1,自引:0,他引:1
根据理论假设,通过选取单透镜的参数和位置,计算说明了单透镜使经由多模光纤出射的大功率Nd:YAG激光束的发射角压缩,光束聚焦效率提高,光束截面场为高斯分布;文中的计算结果符合已知规律,从而说明了理论假设的正确性。 相似文献
26.
ETRⅠ-30调速器是瑞士爱舍维斯工厂生产的具有PID调节规律的电液调速器。本文对其液压控制系统作了较详细的介绍,供有关人员参考。 相似文献
27.
单层球面网壳地震反应特征分析 总被引:29,自引:0,他引:29
考虑不同矢跨比、荷载、跨度和支座刚度等多种因素的影响,对单层球面网壳在地震作用下的反应进行了较全面的研究,给出了其随各参数变化的规律,得出了在单层球面网壳抗震设计中起控制作用的是水平地震作用而不是竖向地震作用等有益的结论.此外本文还给出了由于阻尼比不同而需对引用现行抗震规范反应谱分析的网壳地震作用进行修正的建议. 相似文献
28.
Li Yonghua Wang Chunbo Chen Hongwei 《Frontiers of Energy and Power Engineering in China》2007,1(1):96-100
Power plants in China have to burn blended coal instead of one specific coal for a variety of reasons. So it is of great necessity
to investigate the combustion of blended coals. Using a test rig with a capacity of 640 MJ/h with an absolute milling system
and flue gas online analysis system, characteristics such as burnout, slag, and pollution of some blended coals were investigated.
The ratio of coke and slag as a method of distinguishing coal slagging characteristic was introduced. The results show that
the blending of coal has some effect on NO
x
but there is no obvious rule. SO
x
emission can be reduced by blending low sulfur coal.
Translated from Proceedings of the CSEE, 2005, 25(18): 97–103 [译自: 中国电机工程学报] 相似文献
29.
连续蒸煮器内洗涤结合器外扩散洗涤,具有洗涤时间长、洗涤效率高、提取黑液浓度高、浆层厚度均匀、浆层结构组织和浓度一致等特点,运行可靠,易于自动化控制,实现了洗涤用水的封闭循环。 相似文献
30.
较系统地介绍了我国第1条国产化的中宽带钢冷连轧生产线,即唐山建龙钢铁控股有限公司900mm冷连轧生产线的工艺流程、主要设备组成及技术特点。重点介绍了900mm 4机架六辊轧机的技术参数、性能特点及自动控制系统。该生产线投产以来,取得了较好效果。 相似文献