首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   278篇
  免费   14篇
电工技术   6篇
化学工业   71篇
金属工艺   2篇
机械仪表   2篇
建筑科学   17篇
矿业工程   1篇
能源动力   4篇
轻工业   39篇
水利工程   3篇
无线电   14篇
一般工业技术   23篇
冶金工业   29篇
原子能技术   2篇
自动化技术   79篇
  2024年   1篇
  2023年   1篇
  2022年   5篇
  2021年   10篇
  2020年   2篇
  2019年   8篇
  2018年   4篇
  2017年   6篇
  2016年   9篇
  2015年   9篇
  2014年   12篇
  2013年   8篇
  2012年   11篇
  2011年   21篇
  2010年   11篇
  2009年   15篇
  2008年   14篇
  2007年   18篇
  2006年   12篇
  2005年   10篇
  2004年   21篇
  2003年   15篇
  2002年   13篇
  2001年   3篇
  2000年   9篇
  1999年   13篇
  1998年   4篇
  1997年   5篇
  1996年   1篇
  1995年   4篇
  1994年   3篇
  1993年   4篇
  1991年   2篇
  1988年   1篇
  1986年   2篇
  1982年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
排序方式: 共有292条查询结果,搜索用时 10 毫秒
101.
102.
We take a look at the Composed with Composites initiative. Jaap Ketel, one of the men behind the project, tells us what it's all about.  相似文献   
103.
In 2 experiments, participants haptically estimated length and heaviness of handheld rods while wielding without seeing them. The sets of rods had been constructed such that variation of static moment and the 1st eigenvalue of the inertia tensor (It) were separated. Consistent with previous findings, perceived rod length correlated strongly with It. However, multiple regressions on current data as well as data from previous studies showed a comparable strong correlation between perceived rod length and static moment plus mass. Contrary to previous findings, perceived heaviness correlated strongly with static moment and only weakly with the eigenvalues of the inertia tensor. These results suggest that the inertia tensor does not provide the sole foundation for a theory of dynamic touch. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
104.
The n.m.r. proton signal in coal can be enhanced by irradiating near the larmor frequency of the free electrons present in the coal. Using proton-carbon cross-polarization, this enhancement is transferred to the 13C signal. This decreases the measuring time of a 13C spectrum with several orders of magnitude.  相似文献   
105.
In this paper forward-pruning methods, such as multi-cut and null move, are tested at so-called ALL nodes. We improved the principal variation search by four small but essential additions. The new PVS algorithm guarantees that forward pruning is safe at ALL nodes. Experiments show that multi-cut at ALL nodes (MC-A) when combined with other forward-pruning mechanisms give a significant reduction of the number of nodes searched. In comparison, a (more) aggressive version of the null move (variable null-move bound) gives less reduction at expected ALL nodes. Finally, it is demonstrated that the playing strength of the lines of action program MIA is significantly (scoring 21% more winning points than the opponent) increased by MC-A.  相似文献   
106.
Oil dispersants, the tool of choice for treating oil spills in tropical marine environments, is potentially harmful to marine life, including reef corals. In a previous study, we found that dispersed oil and oil dispersants are harmful to soft and hard coral species at early life stages. In this broader study, we employed a "nubbin assay" on more than 10 000 coral fragments to evaluate the short- and long-term impacts of dispersed oil fractions (DOFs) from six commercial dispersants, the dispersants and water-soluble-fractions (WSFs) of Egyptian crude oil, on two Indo Pacific branching coral species, Stylophora pistillata and Pocillopora damicornis. Survivorship and growth of nubbins were recorded for up to 50 days following a single, short (24 h) exposure to toxicants in various concentrations. Manufacturer-recommended dispersant concentrations proved to be highly toxic and resulted in mortality for all nubbins. The dispersed oil and the dispersants were significantly more toxic than crude oil WSFs. As corals are particularly susceptible to oil detergents and dispersed oil, the results of these assays rules out the use of any oil dispersant in coral reefs and in their vicinity. The ecotoxicological impacts of the various dispersants on the corals could be rated on a scale from the least to the most harmful agent, as follows: Slickgone > Petrotech > Inipol = Biorieco > Emulgal > Dispolen.  相似文献   
107.
The depth-profiles of accelerated aged triterpenoid dammar and mastic varnishes, which had been uncovered by optimized KrF excimer laser ablation (248 nm, 25 ns), were examined by ultraviolet-visible (UV/VIS) spectrophotometry and attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy. The results reflect both the optical properties at the bulk (UV/VIS) and the surface (ATR/FT-IR) and establish the presence of degradation gradients across the depth of the degraded natural resin films. It is demonstrated that the UV part of the ambient radiation is absorbed by the deteriorated surface and that the optical densities of the aged varnish decrease as a function of depth. The absorbed UV wavelengths at the surface and the depth-wise reduction of light intensity result in a depth-dependent decrease in carbonyl absorbance and an increase in C-H bending vibration modes of methylene species pointing to structural modification in the triterpenoid mixture across depth.  相似文献   
108.
The TEX86 is a recently proposed paleothermometer through which ancient seawater temperatures of up to 120 My ago can be reconstructed. It is based on the relative distribution of glycerol dibiphytanyl glycerol tetraethers as measured by high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (HPLC/APCI-MS). The aim of this study was to examine and improve several analytical aspects in the determination of this important proxy in environmental matrices. Comparison of TEX86 analysis using single ion mode (SIM) and mass scanning (m/z 950 to 1450) detection, respectively, revealed that SIM is up to 2 orders of magnitude more sensitive and that the TEX86 can be determined with a reproducibility of +/-0.004 or +/-0.3 degrees C using this method. Comparison of TEX86 values obtained with two different HPLC/APCI-MS set-ups revealed no significant differences. In addition, analysis of TEX86 of extracts obtained by Soxhlet, ultrasonic, and accelerated high-pressure extraction techniques also showed no significant differences between the methods. Our results suggest that TEX86 analysis by HPLC/APCI-MS is robust and can be determined with analytical errors comparable to those of other temperature proxies.  相似文献   
109.
Scope: Little information is available on differences, commonalities and especially interactions in overall gene expression responses as a result of diet, differences in sex (male and female) and effects induced by differences in metabolism. Moreover, it is unknown whether such effects are tissue specific. Methods and results: We investigated the gene expression effects induced by β‐carotene (BC) supplementation, knockout of β‐carotene 15,15‐monooxygenase 1 (Bcmo1) and differences between male and female mice in lung, liver and inguinal white adipose tissue (iWAT). Unsupervised principal component analysis showed that lung gene expression was most affected by knockout of Bcmo1. Liver was most affected by knockout of Bcmo1 and differences in sex. iWAT was most affected by differences in sex. Hardly any genes were commonly influenced by BC among the three tissues. The effect of BC supplementation and knockout of Bcmo1 were relatively sex specific, especially in iWAT. Conclusion: These data demonstrate that gene expression differences induced by BC are limited to the tissue and sex that is analyzed, and that differences in metabolism induced by for example single nucleotide polymorphisms, should be taken into account as much as possible. Moreover, our results indicate that translation from one tissue to the other should be done with caution for any nutritional intervention.  相似文献   
110.
The solubilities of two different non-psychoactive cannabinoids i.e., cannabigerol (CBG) and cannabidiol (CBD), in supercritical carbon dioxide (CO2) have been determined at 315, 326 and 334 K and in the pressure range from 11.3 to 20.6 MPa. These solubility data have been compared to the previously determined solubilities of two psychoactive cannabinoids i.e., (−)-Δ9-tetrahydrocannabinol (Δ9-THC) and cannabinol (CBN), in supercritical CO2. An analytical method with a quasi-flow apparatus was used for the experimental determination. Within the investigated temperature and pressure range, the molar solubility of CBG ranged from 1.17 to 1.91 × 10−4 and the molar solubility of CBD ranged from 0.88 to 2.69 × 10−4. The solubility of the different cannabinoids in supercritical CO2 increases at 326 K in the following order: Δ9-THC < CBG < CBD < CBN. The solubility data were correlated using the Peng-Robinson equation of state in combination with Van der Waals mixing rules. Deviations between calculated results and the experimental data ranged from 0.81 to 6.35% absolute average relative deviation (AARD), except for CBD at 334 K, where the AARD was 18.4%.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号