全文获取类型
收费全文 | 8360篇 |
免费 | 518篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 114篇 |
综合类 | 23篇 |
化学工业 | 2202篇 |
金属工艺 | 243篇 |
机械仪表 | 147篇 |
建筑科学 | 591篇 |
矿业工程 | 98篇 |
能源动力 | 283篇 |
轻工业 | 594篇 |
水利工程 | 50篇 |
石油天然气 | 20篇 |
武器工业 | 1篇 |
无线电 | 661篇 |
一般工业技术 | 1742篇 |
冶金工业 | 470篇 |
原子能技术 | 48篇 |
自动化技术 | 1599篇 |
出版年
2024年 | 15篇 |
2023年 | 117篇 |
2022年 | 208篇 |
2021年 | 327篇 |
2020年 | 199篇 |
2019年 | 210篇 |
2018年 | 231篇 |
2017年 | 267篇 |
2016年 | 351篇 |
2015年 | 293篇 |
2014年 | 378篇 |
2013年 | 596篇 |
2012年 | 533篇 |
2011年 | 718篇 |
2010年 | 506篇 |
2009年 | 475篇 |
2008年 | 487篇 |
2007年 | 427篇 |
2006年 | 379篇 |
2005年 | 304篇 |
2004年 | 254篇 |
2003年 | 187篇 |
2002年 | 166篇 |
2001年 | 103篇 |
2000年 | 96篇 |
1999年 | 115篇 |
1998年 | 126篇 |
1997年 | 99篇 |
1996年 | 87篇 |
1995年 | 51篇 |
1994年 | 59篇 |
1993年 | 39篇 |
1992年 | 48篇 |
1991年 | 26篇 |
1990年 | 40篇 |
1989年 | 23篇 |
1988年 | 28篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 31篇 |
1983年 | 18篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 28篇 |
1975年 | 14篇 |
1969年 | 11篇 |
排序方式: 共有8886条查询结果,搜索用时 15 毫秒
31.
The exact magnetization pattern of magnetic films close to a spin-reorientation transition is difficult to analyze due to the intrinsically three-dimensional (3d) variation of the orientation of the local magnetization. We present a technique how this can be performed, based on the analysis of high quality 2d polarization maps from a single scanning electron microscope with polarization analysis (SEMPA) measurement with tilted sample. The key tool is the statistical distribution of all occurring polarization doublets, visualized in a 2d histogram plot. From the shape of the distribution the type of transition—canted-phase, or coexisting phases—can be inferred. For the canted-phase state, the canting angle can be accurately determined from geometrical considerations. With help of the histogram the image data can be analyzed and the three components of the magnetization can be calculated for most points of the image. For a Co/Pt multilayer film we found a cone state. The magnetization forms a complex pattern consisting of out-of-plane domains while the in-plane magnetization shows a maze pattern. 相似文献
32.
Christian Riesch Bernhard Jakoby 《IEEE sensors journal》2007,7(3):464-469
In this paper, a readout circuit for a thickness shear-mode (TSM) resonator is presented which can be used for sensing applications in liquids such as viscosity sensing. The system features compensation of both spurious capacitances and conductances in parallel to the resonator. This allows measurements even in conductive liquids without the need for an elaborate sealing of the sensor. The influence of the spurious elements is determined by means of two orthogonal synchronous detectors and eliminated by active compensation using voltage-controlled amplifiers (VCAs). Furthermore, the circuit is robust against possible phase errors. The basic concept is discussed in detail, and a readout circuit is developed. A prototype is presented, and sample results are given, demonstrating the feasibility of the approach 相似文献
33.
The present study evaluated the reliability and validity of the Triage Assessment Survey: Organizations (TAS:O), a 27-item, 5-point, Likert summated rating scale. One hundred and seventeen participants responded to the TAS:O after reading mild, moderate, marked and severe organizational crisis scenarios. The overall Cronbach's alpha and split-half reliability were both .93. Confirmatory factor analysis revealed three factors, supporting the hypothesis that the TAS:O is comprised of three distinct factors (i.e., Affect, Behavior, and Cognition). An analysis of variance provided evidence that the TAS:O has the capacity to distinguish among mild, moderate, marked, and severe crises. Because this research is the first to evaluate the TAS:O, further studies are needed to strengthen confidence in the psychometric properties of this scale. 相似文献
34.
35.
The European Space Agency ESA aims at minimizing the safety risks of their space flight projects. Hazard and risk reduction is supported by hazard analysis and probabilistic risk assessment. In hazard analysis hazardous conditions and accident scenarios are identified. Risk assessment is the probabilistic evaluation of accident scenarios and is the basis for risk management. The risk assessment method involves the determination and propagation of event probability. Expert judgement is used in a structured way. In risk management the risk assessment results are used to prioritize and optimize risk reduction efforts and to support risk acceptance evaluations. 相似文献
36.
37.
Christian Azar 《Energy》1994,19(12):1255-1261
Haraden's model for estimating the economic cost of global warming is analysed. We change his method of discounting and some of his input parameters in a manner consistent with physical and economic theory as well as empirical data. We then find much higher costs than Haraden found. These costs are compared to the cost of reducing CO2 emissions and we find that deep cuts of the emissions of CO2 are preferable. A check of the sensitivity of our results with respect to some crucial parameter values does not alter that conclusion. 相似文献
38.
P Lund-Johansen I Hjermann BM Iversen E Thaulow 《Canadian Metallurgical Quarterly》1993,113(6):732-735
Alpha-receptor blockers reduce blood pressure by blocking of the alpha 1-receptors in the smooth muscle cells in the arteriolar walls. The heart pump function is not disturbed. Most studies have shown that the alpha-receptor blockers induce a reduction in plasma-triglycerides and an increase in the ratio between HDL- and LDL-cholesterol. They do not interfere with the metabolism of electrolytes, glucose or uric acid and have no negative effect on pulmonary function. Although long-term use does not induce a permanent increase in heart rate, some patients respond to initial therapy with faster heart rate and palpitations. The alpha-receptor blockers should not be used in patients with coronary heart disease if the patient is not on chronic beta-blockade. When these precautions are followed, the alpha-blockers can be used as first-line treatment--just like ACE-inhibitors and calcium-antagonists. 相似文献
39.
The heat affect zone (HAZ) is in many cases considered to be the most critical part of a weldment. In this paper, the effect of crack size and weld metal mismatch on the HAZ cleavage toughness of wide plate specimens with X-groove has been investigated by the J-Q-M theories and a simple micromechanism for cleavage fracture. Two crack sizes have been studied (a/w = 0.1 and 0.3). In the analyses, the HAZ yield strength is assumed to be higher than the base metal. For each crack size, weld metal local overmatch and local evenmatch with respect to the HAZ are considered. For a given global strain, the results indicate that weld metal overmatch and evenmatch yield the same crack tip loading in terms of J-integral for a/w = 0.3. For a/w = 0.1, overmatch gives lower crack tip loading than evenmatch. For a given crack tip loading, weld metal local evenmatch in general results in less effective crack tip loading than the overmatch. Overmatch is detrimental to HAZ toughness, but this detrimental effect becomes less significant when the crack size decreases. 相似文献
40.