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   291篇
  免费   14篇
电工技术   13篇
化学工业   128篇
金属工艺   3篇
机械仪表   9篇
建筑科学   5篇
能源动力   7篇
轻工业   26篇
水利工程   1篇
无线电   19篇
一般工业技术   51篇
冶金工业   7篇
原子能技术   17篇
自动化技术   19篇
  2022年   5篇
  2021年   3篇
  2020年   1篇
  2019年   2篇
  2018年   5篇
  2017年   5篇
  2016年   9篇
  2015年   11篇
  2014年   10篇
  2013年   18篇
  2012年   12篇
  2011年   14篇
  2010年   10篇
  2009年   9篇
  2008年   20篇
  2007年   12篇
  2006年   17篇
  2005年   12篇
  2004年   5篇
  2003年   7篇
  2002年   12篇
  2001年   4篇
  2000年   6篇
  1999年   3篇
  1998年   3篇
  1997年   7篇
  1996年   9篇
  1995年   4篇
  1994年   9篇
  1993年   1篇
  1992年   4篇
  1991年   3篇
  1990年   7篇
  1989年   5篇
  1988年   4篇
  1987年   3篇
  1986年   1篇
  1985年   6篇
  1984年   7篇
  1983年   3篇
  1982年   3篇
  1980年   3篇
  1979年   2篇
  1978年   2篇
  1975年   2篇
  1974年   3篇
  1973年   1篇
  1966年   1篇
排序方式: 共有305条查询结果,搜索用时 15 毫秒
71.
An airborne laser altimeter using a Nd:YAG laser was constructed to measure surface profiles of sea ice and frozen lakes. The measurements were conducted to develop a technique for estimating the ice amount of the sea ice in the Sea of Okhotsk off the northern shore of Hokkaido Island, Japan. Distributions of freeboards, mean elevations and ice concentrations were investigated from the data observed in 1993-95. Distribution functions of the ice freeboard changed considerably depending on ice concentrations in contrast with the decreasing function for the sea ice in the Arctic Ocean. The mean ice freeboard, however, correlated very well with the ice concentration, which is very important for estimating total ice amounts in regions of drifting ice. The surface roughness of a frozen lake was also observed and analysed.  相似文献   
72.
Many long pyrrole‐imidazole polyamides (PIPs) have been synthesized in the search for higher specificity, with the aim of realizing the great potential of such compounds in biological and clinical areas. Among several types of PIPs, we designed and synthesized hairpin and cyclic PIPs targeting identical sequences. Bind‐n‐Seq analysis revealed that both bound to the intended sequences. However, adenines in the data analyzed by the previously reported Bind‐n‐Seq method appeared to be significantly higher in the motif ratio than thymines, even though the PIPs were not expected to distinguish A from T. We therefore examined the experimental protocol and analysis pipeline in detail and developed a new method based on Bind‐n‐Seq motif identification with a reference sequence (Bind‐n‐Seq‐MR). High‐throughput sequence analysis of the PIP‐enriched DNA data by Bind‐n‐Seq‐MR presented A and T comparably. Surface plasmon resonance assays were performed to validate the new method.  相似文献   
73.
2.2 GBq of 18F (half-life 110 min) was effectively deposited on a graphite electrode of diameter 3 or 5 mm. The fraction of the electro-deposited 18F was as high as 97% of the total 18F produced in the solution. The fraction of the positrons emitted out of the electrode was 44% of the total β+. Thus, as much as 36% of the β+ from the produced 18F is available for the source of slow positron beams.  相似文献   
74.
Cationic polymerization of 2-adamantyl vinyl ether (2-vinyloxytricyclo[3.3.1.13,7]decane; 2-AdVE) and copolymerization of 2-AdVE with n-butyl vinyl ether (NBVE), 2-methoxyethyl vinyl ether (MOVE), or 2-(2-vinyloxyethoxy)ethyl acrylate (VEEA), vinyl ethers containing a flexible chain or a polymerizable group, were performed to obtain poly(vinyl ether) plastics for optical use. With the living cationic initiating systems such as isobutyl vinyl ether–acetic acid adduct/ethylaluminum sesquichloride (IBEA/Et1.5AlCl1.5) or the hydrogen chloride/zinc chloride (HCl/ZnCl2), all the obtained copolymers had unimodal and relatively narrow molecular weight distributions (polydispersity ratio: M w/M n = ~1.5 at high conversion) throughout the copolymerizations. These results indicate that the copolymerizations of 2-AdVE with the three comonomers led to the statistical copolymers without contamination of homopolymers. With BF3OEt2 as an initiator, homopolymer of 2-AdVE and poly(2-AdVE)-based polymers, poly(2-AdVE-stat-NBVE), poly(2-AdVE-stat-MOVE), and poly(2-AdVE-stat-VEEA), were produced with high-molecular weights (M n = 31,800–116,000) in toluene at ?30 °C in quantitative yield within 10 min. They have excellent thermal stability owing to their high glass transition and thermal decomposition temperatures. The transparency (86–91 %) and refractive index (1.52–1.53) of the molded polymers are similar to those of conventional optical plastics such as poly(methyl methacrylate) (PMMA) and polycarbonate (PC), whereas their specific gravity (1.09–1.12) and water absorption (0.06–0.17 %) are significantly lower than those of PMMA and PC. In addition, the Abbe number of poly(2-AdVE), poly(2-AdVE-stat-NBVE), and poly(2-AdVE-stat-MOVE) exceeded 60 and was higher than those of PMMA and PC, indicating that the poly(2-AdVE)-based plastics are very suitable for optical lens.  相似文献   
75.
Appropriate nutrition is an essential prerequisite for effective improvement of athletic performance, conditioning, recovery from fatigue after exercise, and avoidance of injury. Nutritional supplements containing carbohydrates, proteins, vitamins, and minerals have been widely used in various sporting fields to provide a boost to the recommended daily allowance. In addition, several natural food components have been found to show physiological effects, and some of them are considered to be useful for promoting exercise performance or for prevention of injury. However, these foods should only be used when there is clear scientific evidence and with understanding of the physiological changes caused by exercise. This article describes various "functional foods" that have been reported to be effective for improving exercise performance or health promotion, along with the relevant physiological changes that occur during exercise.  相似文献   
76.
Free-radical polymerization of an imidazolium ion-based ionic liquid bearing a methacrylate group, gelling with single-walled carbon nanotubes (SWNTs), allows fabrication of a mechanically reinforced, electroconductive soft material (bucky plastic). A film sample of this material displays an excellent conductivity of 1 S cm(-1) and a 120-fold enhancement of the Young's modulus at a 7 wt % content of SWNTs. The conductivity is temperature-dependent in the range 5-300 K, suggesting that the conductive process involves carrier hopping. Scanning electron and atomic force micrographs of a bucky plastic film display the presence of crosslinked networks consisting of finely dispersed SWNTs. Such nanotube networks, developed in the polymer matrix, likely suppress slipping of entrapped polymer molecules via a strong interfacial interaction and also facilitate intertubular carrier transport. Although a bucky plastic derived from a vinylimidazolium ion-based ionic liquid monomer shows a comparable conductivity to that of the methacrylate version, the film is brittle irrespective of the presence or absence of SWNTs.  相似文献   
77.
Abnormally expanded CAG/CTG repeat DNA sequences lead to a variety of neurological diseases, such as Huntington's disease. Here, we synthesized a cyclic pyrrole-imidazole polyamide (cPIP), which can bind to the minor groove of the CAG/CTG DNA sequence. The double-stranded DNA melting temperature (Tm) and surface plasmon resonance assays revealed the high binding affinity of the cPIP. In addition, next-generation sequencing showed that the cPIP had high specificity for its target DNA sequence.  相似文献   
78.
In order to mitigate the damage due to sediment disasters, knowledge about how slopes fail due to rainfall is indispensable. The main objectives of this paper were to investigate experimentally the effects of surface sand layer density and rainfall intensity on the slop failures due to rainfalls. We conducted a series of experimental tests using 1g physical slope models constructed of Kasumigaura sand and a silt soil named DL clay for the permeable residual surface layer and the firm rock foundation, respectively. A total of nine cases with different combinations of surface sand layer densities and rainfall intensities was tested. Two types of failure: surface slide failure and retrogressive failure, were observed depending on the rainfall intensity and the surface sand layer density. The following mechanism of failure was accounted. At first some sands, which contained a lot of accumulated rainwater, flowed out (flowslide) at the slope toes. The flow slides may be due to the reductions of effective stresses as a result. When a surface slide failure occurred, most of the PWP (pore water pressure) values were still negative but the whole sand layers were almost at the saturation condition. In the case of retrogressive failures, seepage surfaces rose up to higher positions and excess PWPs appeared under the seepage surfaces. This difference of generation mechanism of PWP values may be the deciding factor in the difference in the type of failure.  相似文献   
79.
JAEA and KEK are jointly constructing the high‐intensity proton accelerator project J‐PARC. Its main accelerator is a 3‐GeV rapid cycling synchrotron (RCS). Two types of resonant excitation systems, parallel and cascade, are introduced to excite DC biased 25‐Hz AC currents through its main magnets. The parallel excitation is adopted for the dipole magnet power supply system, and the cascade excitations are adopted for the seven family quadrupole magnets system. In this paper, the two systems are investigated and analyzed, and an explanation is given as to why the different types are adopted in each system. The authors believe that such hybrid exciting systems are most suitable for a high‐power RCS. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 49–60, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20535  相似文献   
80.
Pyrrole-imidazole (PI) polyamides, which target specific DNA sequences, have been studied as a class of DNA minor-groove-binding molecules. To investigate the potential of compounds for cancer treatment, PI polyamides were conjugated with DNA-alkylating agents, such as seco-CBI and chlorambucil. DNA-alkylating PI polyamides have attracted attention because of their sequence-specific alkylating activities, which contribute to reducing the severe side effects of current DNA-damaging drugs. Many of these types of conjugates have been developed as new candidates for anticancer drugs. Herein, we review recent progress into research on DNA-alkylating PI polyamides and their sequence-specific action on targets associated with cancer development.  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