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   905篇
  免费   17篇
电工技术   13篇
化学工业   147篇
金属工艺   16篇
机械仪表   14篇
建筑科学   24篇
能源动力   13篇
轻工业   75篇
水利工程   6篇
石油天然气   1篇
无线电   92篇
一般工业技术   126篇
冶金工业   307篇
原子能技术   6篇
自动化技术   82篇
  2022年   9篇
  2021年   13篇
  2020年   8篇
  2019年   11篇
  2018年   8篇
  2017年   14篇
  2016年   7篇
  2015年   6篇
  2014年   11篇
  2013年   35篇
  2012年   25篇
  2011年   52篇
  2010年   24篇
  2009年   31篇
  2008年   37篇
  2007年   38篇
  2006年   35篇
  2005年   47篇
  2004年   28篇
  2003年   28篇
  2002年   25篇
  2001年   14篇
  2000年   15篇
  1999年   19篇
  1998年   44篇
  1997年   31篇
  1996年   33篇
  1995年   17篇
  1994年   18篇
  1993年   15篇
  1992年   18篇
  1991年   11篇
  1990年   18篇
  1989年   17篇
  1988年   12篇
  1987年   22篇
  1986年   20篇
  1985年   8篇
  1983年   6篇
  1982年   8篇
  1980年   9篇
  1979年   6篇
  1977年   14篇
  1976年   10篇
  1975年   5篇
  1974年   4篇
  1971年   3篇
  1970年   4篇
  1966年   3篇
  1964年   3篇
排序方式: 共有922条查询结果,搜索用时 15 毫秒
11.
There are pervasive sex differences in psychological and physical well-being, many of which can be linked to the differential socialization of men and women. Numerous studies have linked psychological masculinity and femininity to well-being. In the present article, this literature is explained by focusing on the specific personality traits captured by conventional measures of masculinity and femininity: agency (focus on self and forming separations) and communion (focus on others and forming connections), respectively. Both agency and communion are required for optimal well-being (D. Bakan, 1966); when one exists in the absence of the other (unmitigated communion or unmitigated agency), however, negative health outcomes occur. Research that is consistent with this idea is presented, and the processes by which unmitigated agency and unmitigated communion affect well-being are explored. These processes involve control, social support, and health behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
12.
13.
Five experiments are reported that investigate the distribution of selective attention to verbal and nonverbal components of an utterance when conflicting information exists in these channels. A Stroop-type interference paradigm is adopted in which attributes from the verbal and nonverbal dimensions are placed into conflict. Static directional (deictic) gestures and corresponding spoken and written words show symmetrical interference (Experiments 1, 2, and 3), as do directional arrows and spoken words (Experiment 4). This symmetry is maintained when the task is switched from a manual keypress to a verbal naming response (Experiment 5), suggesting the mutual influence of the 2 dimensions is independent of spatial stimulus-response compatibility. It is concluded that the results are consistent with a model of interference in which information from pointing gestures and speech is integrated prior to the response selection stage of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
14.
Therapeutic ultrasound angioplasty has been investigated, clinically, by a number of researchers and represents a potentially promising therapy for the treatment of atherosclerotic lesions. To date, there has been no detailed analysis of the effect of mechanical design parameters, such as wire geometry or damping characteristics, on wire waveguide performance. An apparatus capable of delivering therapeutic ultrasound down small diameter nickel–titanium (NiTi) wire waveguides is described. The output peak-to-peak (p–p) displacements at the distal tip of a 1.0 mm diameter waveguide were measured experimentally, by means of an optical microscope and image analysis software. The output was measured for a range of waveguide lengths from 118 to 303 mm. Wire waveguide distal tip displacements as high as 98 μm (p–p) at 23.5 kHz were measured. For the range of lengths tested, the experimental measurements show the critical relationship between the length of the waveguide and the output distal tip displacements. A finite element model that can predict the resonant frequencies and distal tip displacements of various wire waveguide geometries and configurations, including the effect of damping, is presented. This numerical model has been validated against the experimental displacement data obtained. This will be a valuable design tool for ensuring the safety and effectiveness of therapeutic ultrasound angioplasty procedures.  相似文献   
15.
During development, changes occur in both the sites of erythropoiesis and the globin genes expressed at each developmental stage. Previous work has shown that high-level expression of human beta-like globin genes in transgenic mice requires the presence of the locus control region (LCR). Models of hemoglobin switching propose that the LCR and/or stage-specific elements interact with globin gene sequences to activate specific genes in erythroid cells. To test these models, we generated transgenic mice which contain the human Agamma-globin gene linked to a 576-bp fragment containing the human beta-spectrin promoter. In these mice, the beta-spectrin Agamma-globin (betasp/Agamma) transgene was expressed at high levels in erythroid cells throughout development. Transgenic mice containing a 40-kb cosmid construct with the micro-LCR, betasp/Agamma-, psibeta-, delta-, and beta-globin genes showed no developmental switching and expressed both human gamma- and beta-globin mRNAs in erythroid cells throughout development. Mice containing control cosmids with the Agamma-globin gene promoter showed developmental switching and expressed Agamma-globin mRNA in yolk sac and fetal liver erythroid cells and beta-globin mRNA in fetal liver and adult erythroid cells. Our results suggest that replacement of the gamma-globin promoter with the beta-spectrin promoter allows the expression of the beta-globin gene. We conclude that the gamma-globin promoter is necessary and sufficient to suppress the expression of the beta-globin gene in yolk sac erythroid cells.  相似文献   
16.
The application of nonradioactive RNA probes for Northern blotting offers the advantage of a rapid turn-around time for results without the loss of sensitivity for target mRNA detection. However, a problem that has impeded the widespread use of nonradioactive RNA probes for use in Northern blotting is the difficulty in stripping these probes from nylon membranes after hybridization. In this report we describe two protocols for stripping digoxigenin (Dig)-labeled RNA probes from nylon membranes. One protocol utilizes a phosphate-buffered formamide stripping solution to remove nonchemically modified (regular) RNA probes while the other method utilizes strippable probes that were produced with a chemically modified nucleotide (CTP) and removed by a specific stripping solution. This latter method was developed by Ambion Inc. and is called Strip-EZ. We also describe a protocol for the detection of two separate rat mRNAs using both biotin and digoxigenin-labeled RNA probes that does not require stripping the membrane after hybridization. Finally, we describe the use of another new labeling technology, called Chem-Link, that quickly and conveniently labels RNA for use in Northern blotting.  相似文献   
17.
Nausea and vomiting are common gastrointestinal complaints that can be triggered by diverse emetic stimuli through central and/or peripheral nervous systems. Both nausea and vomiting are considered as defense mechanisms when threatening toxins/drugs/bacteria/viruses/fungi enter the body either via the enteral (e.g., the gastrointestinal tract) or parenteral routes, including the blood, skin, and respiratory systems. While vomiting is the act of forceful removal of gastrointestinal contents, nausea is believed to be a subjective sensation that is more difficult to study in nonhuman species. In this review, the authors discuss the anatomical structures, neurotransmitters/mediators, and corresponding receptors, as well as intracellular emetic signaling pathways involved in the processes of nausea and vomiting in diverse animal models as well as humans. While blockade of emetic receptors in the prevention of vomiting is fairly well understood, the potential of new classes of antiemetics altering postreceptor signal transduction mechanisms is currently evolving, which is also reviewed. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide potential answers.  相似文献   
18.
19.
The effect of water addition on the complete oxidation of benzene and propane VOCs by uranium oxide catalysts has been investigated. Benzene oxidation was studied using a silica supported U3O8 catalyst. Complete oxidation is promoted by the addition of 2.6% water compared with the reactivity when no water is added to the reactant feed. Increasing the water concentration to 12.1% resulted in a suppression of oxidation activity. Investigation of propane oxidation using U3O8 shows a dramatic promotion of activity. Propane conversion was ca. 50% at 600 °C without added water, whilst it increased to 100% at 400 °C with the addition of 2.6% water. A comparison of oxidation activity has been made with Mn2O3, an oxide recognised for complete oxidation. In contrast to the U3O8 catalysts the addition of 2.6% water suppresses the activity of Mn2O3. In situ powder X-ray diffraction studies showed that the bulk U3O8 structure was stable under all the reaction conditions. The origin of the increased activity is not clear but may be due to modification of the catalyst surface and the contribution from new reaction pathways such as steam reforming.  相似文献   
20.
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