全文获取类型
收费全文 | 40349篇 |
免费 | 3995篇 |
国内免费 | 2893篇 |
专业分类
电工技术 | 1081篇 |
综合类 | 4211篇 |
化学工业 | 5066篇 |
金属工艺 | 5280篇 |
机械仪表 | 3518篇 |
建筑科学 | 5936篇 |
矿业工程 | 2652篇 |
能源动力 | 1120篇 |
轻工业 | 2340篇 |
水利工程 | 1939篇 |
石油天然气 | 2307篇 |
武器工业 | 350篇 |
无线电 | 1189篇 |
一般工业技术 | 6376篇 |
冶金工业 | 2760篇 |
原子能技术 | 318篇 |
自动化技术 | 794篇 |
出版年
2024年 | 155篇 |
2023年 | 532篇 |
2022年 | 1743篇 |
2021年 | 1745篇 |
2020年 | 1272篇 |
2019年 | 1178篇 |
2018年 | 1110篇 |
2017年 | 1362篇 |
2016年 | 1492篇 |
2015年 | 1538篇 |
2014年 | 2228篇 |
2013年 | 2447篇 |
2012年 | 2632篇 |
2011年 | 2925篇 |
2010年 | 2231篇 |
2009年 | 2312篇 |
2008年 | 2170篇 |
2007年 | 2588篇 |
2006年 | 2270篇 |
2005年 | 1988篇 |
2004年 | 1703篇 |
2003年 | 1439篇 |
2002年 | 1292篇 |
2001年 | 1077篇 |
2000年 | 965篇 |
1999年 | 800篇 |
1998年 | 676篇 |
1997年 | 602篇 |
1996年 | 511篇 |
1995年 | 413篇 |
1994年 | 358篇 |
1993年 | 284篇 |
1992年 | 257篇 |
1991年 | 179篇 |
1990年 | 164篇 |
1989年 | 154篇 |
1988年 | 96篇 |
1987年 | 71篇 |
1986年 | 45篇 |
1985年 | 35篇 |
1984年 | 41篇 |
1983年 | 18篇 |
1982年 | 29篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 21篇 |
1964年 | 10篇 |
1961年 | 6篇 |
1959年 | 8篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
在介绍推进波作用下底泥起动特点的基础上,将上层水体作为粘性流体,底泥作为粘弹性体,推导了推进波作用下泥床面剪应力的表达式,并根据试验结果,给出了推进波作用下底泥起动时的床面剪应力与底泥流变参数的关系。 相似文献
72.
M. Kovac 《Journal of Materials Engineering and Performance》1994,3(1):61-64
This article discusses residual stress measurements by means of electrochemical removal of material layers with residual stresses
and simultaneous measurement of strain on the opposite specimen side with strain gages. Exact measurements are impossible
particularly because of the small bevel gear module. With the method presented, the average residual stresses in the tooth
root plane and underlying layers are measured. Residual stress distribution after each consecutive production phase is plotted
and analyzed. Residual stress measurements enable the engineer to adequately assess each individual production phase and by
that improve the quality of the complete production process. 相似文献
73.
Quantitative x-ray diffraction topography techniques have been used to measure the residual strain magnitude and uniformity
of deposition for Mo and W sputtered films on Si(100) substrates. High sensitivity rocking curve measurements were able to
determine differential strains for films as thin as 2.5 nm; while Bragg angle contour mapping had similar sensitivity and
was also able to assess coating uniformity and stress distribution over areas covering a whole wafer. Measurements of strain
versus film thickness over a range of 2.5 nm to 80 nm showed that a critical thickness exists for maximum residual strain.
Growth beyond this range produces stress relaxation. This non-destructive type of analysis could be employed on a wide range
of film-substrate combinations. 相似文献
74.
Johan M. Thevelein 《Yeast (Chichester, England)》1994,10(13):1753-1790
75.
76.
全20CrMnTi表面激光重熔的组织与性能研究 总被引:2,自引:0,他引:2
本文对激光重熔20CrMnTi材料表明改性层显微组织分布特征、表面硬度分布规律以及残余应力状态作了研究,结果表明,表面改性层由熔融层、相变硬化层及过渡层组成,且材料表面显微硬度得到大幅度提高,表面硬度达到HV841,约提高4倍。硬化层深度约1mm。残余应力测试得出最大残余应力出现在熔凝带中心,表现为压应力。随着离中心距离的增大,残余应力逐步降低,到熔化带边缘,表现为低幅值压应力;而熔池的外边缘应力在热影响区则转变为拉应力状态。 相似文献
77.
Wide variability exists with respect to how breast cancer survivors respond to common psychological and psychosocial challenges of their disease, ranging from posttraumatic stress disorder to posttraumatic growth. This cross-sectional study examined contextual, disease-related, and intraindividual predictors of posttraumatic growth in 224 randomly selected breast cancer survivors. A series of hierarchical regression analyses found that age at diagnosis, marital status, employment, education, perceived intensity of disease, and active coping accounted for 34%, 35%, and 28% of the variance in growth in relationships with others, new possibilities, and appreciation for life. These findings suggest that a more comprehensive model of growth will be helpful in understanding the various factors that play a role in breast cancer survivors' perception of psychological and psychosocial growth. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
While concerns about the psychological effects of war are not new, only recently has systematic attention been paid to such problems among past and present military personnel. There is increasing recognition that mental health has serious implications for operational performance, retention, and compensation. Although little controlled research exists with this population, preliminary evidence suggests that psychological treatments for posttraumatic stress disorder may be beneficial, albeit less so than for civilian populations. This article reviews evidence for each of several psychological treatment stages: stabilization and engagement, psychoeducation, symptom management, prolonged exposure, cognitive restructuring, and relapse prevention, with particular reference to the clinical issues raised by military personnel. Possible explanations for reduced treatment effects in this population compared with civilians are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
79.
应用地应力模拟技术研究断块区剩余油分布 总被引:1,自引:0,他引:1
应力场数值模拟不仅能够重塑出不同阶段地应力场,而且还可以定量一半定量地预测破裂的发生、裂缝的方向和密度,进一步探讨时间和空间上油气运移的规律,为油田勘探、开发提供必要的依据。本文以大庆萨北开发区北二西断层区为研究对象,通过应力场数值模拟研究了流体运移势场与剩余油分布的关系、流体运移与构造应力的关系、裂缝形成与剩余油分布的关系,确定了剩余油分布的有利区域,为油田注采系统的设计、部署和油田开发及措施调整提供了依据。 相似文献
80.
New accurate two-noded shear-flexible curved beam elements 总被引:2,自引:0,他引:2
There are two purposes of this work. One is to present two accurate two-noded finite elements which are derived from the
potential energy principle and the Hellinger–Reissner functional principle respectively. The second is to show the successful
application of the internal displacement parameters in developing a high-order related displacement-rotation interpolation
field. Because the derived interpolation field is capable of accurately modeling deformation modes in extreme thin curved
beams and nearly straight beams, both shear locking and membrane shocking are avoided. Several standard numerical tests display
superior behaviors of the present elements.
Received: 5 February 2002 / Accepted: 16 September 2002 相似文献