全文获取类型
收费全文 | 1357篇 |
免费 | 19篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 17篇 |
综合类 | 8篇 |
化学工业 | 134篇 |
金属工艺 | 32篇 |
机械仪表 | 33篇 |
建筑科学 | 84篇 |
矿业工程 | 4篇 |
能源动力 | 34篇 |
轻工业 | 42篇 |
水利工程 | 22篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 134篇 |
一般工业技术 | 163篇 |
冶金工业 | 488篇 |
原子能技术 | 19篇 |
自动化技术 | 170篇 |
出版年
2022年 | 17篇 |
2021年 | 17篇 |
2020年 | 19篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 15篇 |
2014年 | 26篇 |
2013年 | 36篇 |
2012年 | 29篇 |
2011年 | 34篇 |
2010年 | 40篇 |
2009年 | 34篇 |
2008年 | 31篇 |
2007年 | 38篇 |
2006年 | 29篇 |
2005年 | 36篇 |
2004年 | 28篇 |
2003年 | 22篇 |
2002年 | 26篇 |
2001年 | 27篇 |
2000年 | 24篇 |
1999年 | 48篇 |
1998年 | 117篇 |
1997年 | 80篇 |
1996年 | 68篇 |
1995年 | 35篇 |
1994年 | 37篇 |
1993年 | 43篇 |
1992年 | 19篇 |
1991年 | 11篇 |
1990年 | 22篇 |
1989年 | 20篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 21篇 |
1983年 | 22篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 23篇 |
1976年 | 42篇 |
1975年 | 9篇 |
1969年 | 7篇 |
1968年 | 10篇 |
排序方式: 共有1392条查询结果,搜索用时 0 毫秒
81.
This study measured volumetric liver blood flow and galactose clearance concurrently during orthotopic liver transplant in human subjects. Ultrasound transit time flowmeters measured hepatic artery and portal vein flow 1-3 h after reperfusion. Galactose (100 mg/min) was infused over 45-60 min to steady state for calculation of clearance. Mean +/- S.D. total volumetric flow was 1966 +/- 831 ml/min with portal flow contributing 86%. Mean galactose clearance was 1988 +/- 641 ml/min. There was a significant correlation (p < 0.05, r = 0.61) between volumetric total liver blood flow and galactose clearance. The data show that: (i) the newly transplanted liver is capable of metabolizing galactose within 1-3 h of reperfusion; and (ii) liver blood flow is high in the newly implanted liver. The clinical importance of this observation is that there is increased clearance of high first pass substances by the transplanted liver which may be of importance in patient management. 相似文献
82.
伸出织物表面的短、粗纤维末梢是产生贴身纺织品针刺感的主要原因,本质是纤维末梢刺扎并诱发皮肤伤害性机械刺激感受器.通常基于固定-铰接约束条件下弹性压杆轴向压缩稳定性理论,计算纤维末梢的临界压力判断这种感受器的诱发可能性.然而,这种方法忽略了织物握持纤维末梢的强度、纤维末梢接触皮肤的滑动阻力及其柔韧性特征.本文以伸出织物表面的直立纤维末梢为对象,假设其织物握持端为线弹性转动约束、另一端受皮肤的接触反作用力和滑动阻力作用,建立纤维末梢刺扎人体皮肤的弯曲变形力学模型.通过参数化模拟,本文比较分析了纤维末梢在弹性-支撑约束和固定-铰接约束条件下的弯曲变形行为.研究发现,纤维末梢在弹性-支撑约束条件下的弯曲力学行为才能解释其刺扎皮肤产生的大多数力学现象及针刺感现象. 相似文献
83.
对分子束外延(MBE)自组织生长的InAlAs量子点材料进行了拉曼散射实验。结合原子力显微镜(AnD对量子点形貌观察的结果,分析了InAlAs量子点生长过程中尺寸、密度和均匀性的改变,并研究了三维岛的结构对拉曼谱线的影响。对InAlAs淀积厚度不同样品的拉曼谱分析表明,岛状结构的尺寸横纵比与类GaAsLO模和类AlAs LO模的半高全宽有密切关系。不同偏振下的拉曼实验证实了该结构中的光学声子在Z(X,X)Z偏振条件下为非拉曼活性。 相似文献
84.
A numerical procedure is presented for solving Cauchy integrals with fourth-order accuracy. The method, based on Spline Collocation Polynomials, is shown to be superior, by far, to a second-order-accurate finite difference approach. The evaluation of the integral (direct problem) and of the integrand as well (inverse problem) is considered. Several approaches are considered and some unexpected results for the case of the inverse problem are pointed out. 相似文献
85.
86.
A nonstationary method of investigating heat transfer during boiling on a flat surface is described. The heat flux is determined from the reduction in the intrinsic energy of a massive bar over a definite time interval by graphic integration of the temperature field over the bar length. 相似文献
87.
An improved selective attention model is proposed in this paper, which is designed as a network of spiking neurons of Hodgkin--Huxley type with star-like connections between the central units and peripheral neurons. In this model, peripheral neurons represent the neurons located in the primary visual cortex. Since orientation preference is an important property of neurons in primary visual cortex, it should be considered except for external stimuli intensity. Simulation results show that the improved model can sequentially select objects with different orientation preferences and has a reliable shift of attention from one object to another, which are consistent with the experimental results that the neurons with different orientation preferences are laid out in pinwheel patterns. 相似文献
88.
辽宁省凌源县牛河梁出土的炉壁研究 总被引:3,自引:1,他引:2
在牛河梁的一座人工建造的金字塔顶部发现的,被认定是从其它地方迁移过去的炉壁残片及其粘附的炉渣是辽西地区年代最早的冶铜遗物,热释光测定其年代为距今300~3500年,属夏家店下层化,炉渣含镁较高,夹杂有各种粒度的纯铜颗粒财质广场 河梁附近有多处古代开采遗迹的铜矿点,其脉石矿物也含有较高的镁,这些事实表明这些炉壁残片及其粘附的炉渣是冶炼当地氧化矿石的遗物,炉壁残片结果显示,炼炉上部内径约25cm,有 相似文献
89.
Hydrogen effects on the spall strength and fracture characteristics of amorphous Fe-Si-B alloy at very high strain rates 总被引:1,自引:0,他引:1
N. Eliaz Ph.D. E. Moshe S. Eliezer D. Eliezer 《Metallurgical and Materials Transactions A》2000,31(4):1085-1093
A novel approach is suggested, using laser-induced shock wave measurements to estimate the effects of cathodic hydrogen charging
on the mechanical properties and fracture characteristics of materials. This approach is applied to (1) determine the dominant
mechanism of hydrogen embrittlement (HE) in an amorphous Fe80B11Si9 alloy; and (2) estimate the effects of the high pressures involved in cathodic charging. The dynamic spall strength of an
amorphous Fe80B11Si9 alloy shocked before and after hydrogenation by a high-power laser to very high pressures (tens of giga Pascals) is measured.
The dynamic spall strength of crystalline iron is measured as well for comparison. An optically recording velocity interferometer
system (ORVIS) is used to measure the profile of the free surface velocity in time. The spall strength and the strain rate
are calculated from the measurement of the free surface velocity as a function of time. Fracture characteristics are studied
by scanning electron microscopy (SEM). The main conclusions are (1) the most reasonable mechanism of HE in the amorphous Fe-Si-B
alloy is the high-pressure bubble formation; (2) the high pressures involved in cathodic hydrogen charging or laser-induced
shock waves measurements may have similar effects on fracture characteristics; and (3) at very high strain rates, the spall
strength is determined mainly by the interatomic bonds. 相似文献
90.
This article proposes a standard, easy-to-interpret effect size estimate for one-sample research. The proportion index (π) shows the hit rate on a scale on which .50 is always the null value regardless of the number of equally likely choices. The index π is useful in the design of one-sample research because it can guide the best choice of number of response alternatives. Significance tests and confidence limits are readily computed. For meta-analyses of one-sample studies, tests of heterogeneity of a set of πs and contrasts among them are described. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献