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   683篇
  免费   28篇
  国内免费   6篇
电工技术   1篇
综合类   2篇
化学工业   295篇
金属工艺   9篇
机械仪表   8篇
建筑科学   15篇
矿业工程   4篇
能源动力   28篇
轻工业   60篇
水利工程   6篇
石油天然气   13篇
无线电   25篇
一般工业技术   164篇
冶金工业   21篇
原子能技术   1篇
自动化技术   65篇
  2024年   4篇
  2023年   11篇
  2022年   84篇
  2021年   74篇
  2020年   14篇
  2019年   19篇
  2018年   20篇
  2017年   14篇
  2016年   40篇
  2015年   18篇
  2014年   37篇
  2013年   52篇
  2012年   43篇
  2011年   45篇
  2010年   24篇
  2009年   31篇
  2008年   31篇
  2007年   23篇
  2006年   20篇
  2005年   23篇
  2004年   18篇
  2003年   14篇
  2002年   18篇
  2001年   3篇
  2000年   6篇
  1999年   4篇
  1998年   4篇
  1997年   6篇
  1996年   2篇
  1994年   1篇
  1993年   3篇
  1992年   3篇
  1991年   2篇
  1990年   2篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
排序方式: 共有717条查询结果,搜索用时 15 毫秒
51.
In countries with unstable conditions, negotiations regarding construction work takes place under conditions of great uncertainty with both sides, the purchaser and the investor, trying to minimize the difficulties. This paper gives an insight of how matters relating to costing are looked at by professionals when faced with such conditions.  相似文献   
52.
Single-crystal silicon microstructures, of identical design, exhibit different failure rates (following fabrication or mechanical shock testing) due to various processes. The microstructures fabricated with a boron diffusion and subsequent removal of the boron-diffused layer have a higher survival rate to the fabrication process and to mechanical shock. The survival rate (a survivor has an intact proof mass and beam) through the process is increased by 26.5%. At a 3680g shock, the boron-diffused devices have a 2.3% lower failure rate but the difference is not statistically significant. These results have been developed with wafer-level shock testing, which permits bulk testing of many samples in a cost-effective manner.  相似文献   
53.
Psammoma bodies (PBs) are one of many choroids plexus aging changes. The aim of our research was to perform the quantification of PBs' presence in human choroids plexus stroma, as well as to evaluate the characteristics of choroids plexus stroma in cases in which PBs were present. Afterwards, the observations of the histochemical analysis would be confirmed by immunohistochemical analysis. Choroid plexuses of 30 cadavers were used for the histochemical and, choroids plexuses of 15 cadavers in which PBs' presence was confirmed during the histochemical analysis, were used as material for the immunohistochemical analysis. Light microscopy, histochemical, immunohistochemical, and morphometric method were applied during the study. Classification of the cases was performed by cluster analysis. We observed increase of choroids plexus PBs' presence during the aging process. But this increase is not linear. Their presence is the largest in the second cluster that is younger than the third and older than the first. Nuclear morphometric parameters of the stroma in these cases showed that the cellular composition in this cluster is different than in other two and, that contain larger number of lymphoid cells. Immunohistochemical analysis showed PBs' positive reaction on vimentin, CD45R0, and LCA markers, while in their vicinity, as well as inside them, numerous T-cells were observed. So, the presence of CD45R0 and LCA-positive T cells, PBs' positive reaction on the same markers, indirectly connect these cells with PBs' formation process.  相似文献   
54.
The lipid composition of the seed oil of three varieties (L-74, VIR-11 and BGR-455) of Lallemantia iberica Fisch. &; Mey. (Lamiaceae) harvested in Bulgaria was examined in detail. Triacylglycerols (TAG >90%), phospholipids (<3%), sterol esters (~0.2%), and accompanying compounds—sterols (~0.3%) and tocopherols (336–499 mg/kg)—were determined for the first time. In addition, the specific distribution of fatty acids between the lipid classes was elucidated. Nineteen TAG species were unambiguously identified and quantified and of these the highly unsaturated trilinolenin, dilinolenyl linoleate and dilinolenyl palmitate comprised 59% of the total TAG. Phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine were the main phospholipids. Beta-sitosterol was the main sterol component, followed by campesterol and stigmasterol. Gamma-tocopherol predominated (>90%) in the tocopherol fraction. Palmitic acid (16:0) was the major fatty acid of the phospholipids and oleic acid (cis 9-18:1) dominated in the sterol ester fraction. The three varieties have similar lipid compositions with BGR-455 being slightly more saturated. Due to its composition, Lallemantia oil might compete successfully with flax and other plant oils as a source of linolenic fatty acid in industrial and dietary applications.  相似文献   
55.
Phase equilibria of the ternary Cu-Co-S system were studied within liquidus–solidus temperature range in the inert atmosphere at atmospheric pressure. Integrated application of such methods as differential thermal analysis, thermogravimetry, scanning electron microscopy, and electron probe microanalysis, makes it possible to determine phase transitions temperature and equilibrium phases composition in the system with high level of accuracy. Experimental results obtained in this work for the Cu-Co-S system are presented as liquidus and solidus surfaces projections of the Cu-Co-S system. Phase transformations occurring in the system are discussed.  相似文献   
56.
Irradiation with helium ions is an effective method for triggering ferromagnetism in graphite. Chemical inertness of helium suggests that local magnetic moment formation is determined solely by the intrinsic carbon defects created during the target damage. Interacting moments are located in two places: in the vicinity of the sample surface and near the point of maximum defect generation.  相似文献   
57.
In this paper, we describe the development of microcontact printing stamps from photopatternable silicone. The photopatternability of this material enables convenient and fast stamp fabrication, and allows rapid patterning of substrates for culturing biological cells. Microcontact printing stamps made of the photopatternable silicone with linewidths as small as 2 μm were fabricated and reliable cell patterning results were obtained by optimizing the stamping process. An optimal stamp surface was obtained by optimizing the photolithographic process. Our successful demonstration of patterning cells using the photopatternable silicone stamps establishes this alternative approach for fabricating microcontact printing stamps.  相似文献   
58.
59.
60.
The light‐induced reversible switching of the swelling of microgel particles triggered by photo‐isomerization and binding/unbinding of a photosensitive azobenzene‐containing surfactant is reported. The interactions between the microgel (N‐isopropylacrylamide, co‐monomer: allyl acetic acid, crosslinker: N,N′‐methylenebisacrylamide) and the surfactant are studied by UV‐Vis spectroscopy, dynamic and electrophoretic light scattering measurements. Addition of the surfactant above a critical concentration leads to contraction/collapse of the microgel. UV light irradiation results in transcis isomerization of the azobenzene unit incorporated into the surfactant tail and causes an unbinding of the more hydrophilic cis isomer from the microgel and its reversible swelling. The reversible contraction can be realized by blue light irradiation that transfers the surfactant back to the more hydrophobic trans conformation, in which it binds to the microgel. The phase diagram of the surfactant‐microgel interaction and transitions (aggregation, contraction, and precipitation) is constructed and allows prediction of changes in the system when the concentration of one or both components is varied. Remote and reversible switching between different states can be realized by either UV or visible light irradiation.  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