全文获取类型
收费全文 | 38418篇 |
免费 | 6024篇 |
国内免费 | 2654篇 |
专业分类
电工技术 | 3335篇 |
技术理论 | 2篇 |
综合类 | 4112篇 |
化学工业 | 4600篇 |
金属工艺 | 1720篇 |
机械仪表 | 2473篇 |
建筑科学 | 4274篇 |
矿业工程 | 2406篇 |
能源动力 | 2064篇 |
轻工业 | 4725篇 |
水利工程 | 2235篇 |
石油天然气 | 3354篇 |
武器工业 | 857篇 |
无线电 | 2832篇 |
一般工业技术 | 2842篇 |
冶金工业 | 2464篇 |
原子能技术 | 403篇 |
自动化技术 | 2398篇 |
出版年
2024年 | 191篇 |
2023年 | 879篇 |
2022年 | 1672篇 |
2021年 | 1994篇 |
2020年 | 2102篇 |
2019年 | 1577篇 |
2018年 | 1339篇 |
2017年 | 1619篇 |
2016年 | 1727篇 |
2015年 | 1796篇 |
2014年 | 2615篇 |
2013年 | 2394篇 |
2012年 | 2999篇 |
2011年 | 3023篇 |
2010年 | 2296篇 |
2009年 | 2253篇 |
2008年 | 1846篇 |
2007年 | 2260篇 |
2006年 | 2016篇 |
2005年 | 1777篇 |
2004年 | 1431篇 |
2003年 | 1247篇 |
2002年 | 1058篇 |
2001年 | 846篇 |
2000年 | 768篇 |
1999年 | 629篇 |
1998年 | 445篇 |
1997年 | 353篇 |
1996年 | 315篇 |
1995年 | 299篇 |
1994年 | 245篇 |
1993年 | 211篇 |
1992年 | 159篇 |
1991年 | 123篇 |
1990年 | 115篇 |
1989年 | 81篇 |
1988年 | 45篇 |
1987年 | 45篇 |
1986年 | 30篇 |
1985年 | 31篇 |
1984年 | 36篇 |
1983年 | 22篇 |
1982年 | 27篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1966年 | 8篇 |
1964年 | 15篇 |
1959年 | 11篇 |
1957年 | 9篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
121.
Posttraumatic stress in children and adolescents exposed to family violence: I. Overview and issues.
Exposure to child physical abuse and parents' domestic violence can subject youth to pervasive traumatic stress and can lead to posttraumatic stress disorder (PTSD). This article presents evolving conceptualizations in the burgeoning field of trauma related to family violence exposure and describes how the often repeating and ongoing nature of family violence exposure can complicate a PTSD diagnosis. In addition, recent literature indicates that children exposed to family violence may experience problems in multiple domains of functioning and may meet criteria for multiple disorders in addition to PTSD. Considerations salient to the recognition of traumatic stress in this population and that inform assessment and treatment planning are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
122.
膨胀岩工程特性试验研究 总被引:5,自引:0,他引:5
为研究南水北调中线工程膨胀岩的工程特性,选取新乡潞王坟段的代表性岩层——强风化黏土岩和泥灰岩的原状样及扰动样,进行了物理性质试验、击实试验、力学性质试验以及膨胀特性试验。试验成果表明:对扰动样的标准击实基本上很难达到天然状态下的干密度状态,土体的结构性在击实过程中不能得到较好的恢复;初始含水率越小,吸湿能力越大,其强度降低程度越大,饱和强度参数越小;含水率低的试样,其破坏强度大,但破坏应变小;相同的压实度下,含水率越低试样的软化现象越明显;相同压实度的土样,含水率越大,其初始切线模量越小;压实度在90%~98%,压实度越大,膨胀力与膨胀率越大;随着压实度超过98%,膨胀率与压实度关系曲线存在一峰值转折点,而且此峰值点出现在压实度为98%~100%。压力与膨胀率关系曲线分两直线段:一陡降段和一平缓段,各曲线之间近似平行,曲线截距为无荷膨胀率数值。该成果为南水北调中线工程膨胀岩渠坡段的设计施工提供了科学依据。 相似文献
123.
M A Ramaswamy 《Sadhana》1987,10(3-4):445-458
The theoretical aerodynamic characteristics of a typical lifting symmetric supercritical airfoil demonstrating its superiority
over thenaca 0012 airfoil from which it was derived are presented in this paper. Further, limited experimental results confirming the
theoretical inference are also presented.
Invited Lecture given at the 3rd Asian Congress on Fluid Mechanics, held in Tokyo during 1–5 September, 1986 相似文献
124.
125.
126.
127.
NiTi形状记忆合金激光气体氮化层表面特征 总被引:2,自引:0,他引:2
为改善NiTi合金的表面性能,利用2kW连续波Nd:YAG对NiTi合金进行激光气体氮化处理。采用SEM、TEM、XRD、XPS和纳米压痕研究了氮化层的显微组织及表面特征.结果表明:激光气体氮化可以在NiTi合金表面制备连续、无裂纹、厚度为2μm的TiN表面层,该表面层中基本不合有Ni元素且具有很高的硬度,其纳米压痕硬度为29.28GPa. 相似文献
128.
This article reports research intended to assess and extend a recent theory of peer responses to low-performing team members (J. A. LePine & L. Van Dyne, 2001a). An instrument that assesses 4 types of peer responses to low performers (compensating for, training, motivating, and rejecting) was developed and then cross-validated in a subsequent study. Results of the study supported the validity of the peer responses measure and were generally consistent with the attributional theory of peer responses. Low-performer characteristics influenced the peer responses. These effects were mediated in part by peer attributions, affect, and cognitions, which explained variance in the peer responses over and above the variance explained by respondents' personality characteristics (i.e., The Big Five). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
129.
Evidence is presented that bears on 9 hypotheses about the link between religion or spirituality and mortality, morbidity, disability, or recovery from illness. In healthy participants, there is a strong, consistent, prospective, and often graded reduction in risk of mortality in church/service attenders. This reduction is approximately 25% after adjustment for confounders. Religion or spirituality protects against cardiovascular disease, largely mediated by the healthy lifestyle it encourages. Evidence fails to support a link between depth of religiousness and physical health. In patients, there are consistent failures to support the hypotheses that religion or spirituality slows the progression of cancer or improves recovery from acute illness but some evidence that religion or spirituality impedes recovery from acute illness. The authors conclude that church/service attendance protects healthy people against death. More methodologically sound studies are needed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
130.
Much research has examined gender and age effects on compensation, concluding that a wage gap exists favoring men and negative stereotypes against older workers persist. Although the effect of an employee's gender or age has been widely studied, little work has examined the impact of the demographic characteristics of a focal employee's immediate referent groups (e.g., subordinates, peers, or supervisors) on pay. The effect of the gender and age composition of a focal manager's subordinates, peers, and supervisor on the manager's compensation levels was investigated in a sample of 2,178 managers across a wide range of organizations and functional areas. After controlling for a number of human capital variables, results indicated that not only does a wage gap favoring men exist, but also managerial pay is lower when managers' referent groups are largely female, when subordinates are outside the prime age group, and when peers and supervisors are younger. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献