全文获取类型
收费全文 | 7962篇 |
免费 | 583篇 |
国内免费 | 229篇 |
专业分类
电工技术 | 248篇 |
综合类 | 334篇 |
化学工业 | 1608篇 |
金属工艺 | 259篇 |
机械仪表 | 443篇 |
建筑科学 | 597篇 |
矿业工程 | 158篇 |
能源动力 | 252篇 |
轻工业 | 628篇 |
水利工程 | 139篇 |
石油天然气 | 244篇 |
武器工业 | 31篇 |
无线电 | 880篇 |
一般工业技术 | 1165篇 |
冶金工业 | 402篇 |
原子能技术 | 116篇 |
自动化技术 | 1270篇 |
出版年
2024年 | 23篇 |
2023年 | 121篇 |
2022年 | 250篇 |
2021年 | 296篇 |
2020年 | 251篇 |
2019年 | 209篇 |
2018年 | 235篇 |
2017年 | 271篇 |
2016年 | 270篇 |
2015年 | 319篇 |
2014年 | 417篇 |
2013年 | 490篇 |
2012年 | 536篇 |
2011年 | 591篇 |
2010年 | 488篇 |
2009年 | 494篇 |
2008年 | 451篇 |
2007年 | 406篇 |
2006年 | 423篇 |
2005年 | 323篇 |
2004年 | 239篇 |
2003年 | 199篇 |
2002年 | 205篇 |
2001年 | 144篇 |
2000年 | 152篇 |
1999年 | 167篇 |
1998年 | 154篇 |
1997年 | 104篇 |
1996年 | 107篇 |
1995年 | 59篇 |
1994年 | 67篇 |
1993年 | 49篇 |
1992年 | 34篇 |
1991年 | 44篇 |
1990年 | 27篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 3篇 |
排序方式: 共有8774条查询结果,搜索用时 15 毫秒
101.
Traumatic brain injury (TBI) is a devastating injury with severe consequences. In this paper, we conduct a simulation study on the commonly implemented care delivery process for TBI rehabilitation in the US, which covers three care categories: inpatient acute, outpatient sub-acute and general residential care. Our investigation is focused on assessing how coverage duration of publicly funded rehabilitation impacts two key system outcomes: sub-acute rehabilitation readmission and total rehabilitation spending. We develop prediction models on the above two outcomes for patients of different conditions. We introduce the notions of forceful transition and medical necessity adjustment, and embed the notions in a state-transition simulation model. Our simulation results suggest that to minimise the care spending, the duration of publicly insured outpatient sub-acute rehab be set smaller than what is currently implemented but not to the point where coverage should be completely removed. Our sensitivity analysis justifies the robustness of our results under variations on model parameters. 相似文献
102.
103.
Nanotransfer Printing: Inkjet‐Assisted Nanotransfer Printing for Large‐Scale Integrated Nanopatterns of Various Single‐Crystal Organic Materials (Adv. Mater. 15/2016) 下载免费PDF全文
104.
Crystallization‐Induced Emission Enhancement of a Deep‐Blue Luminescence Material with Tunable Mechano‐ and Thermochromism 下载免费PDF全文
Zhen Wu Shenzhong Mo Lina Tan Bing Fang Zhiqiang Su Yantu Zhang Meizhen Yin 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(40)
Organic luminescent materials with the ability to reversibly switch the luminescence when subjected to external stimuli have attracted considerable interest in recent years. However, the examples of luminescent materials that exhibit multiresponsive properties are rarely reported. In this work, a new stimuli‐responsive dye P1 is designed and synthesized with two identical chromophores of naphthalimide, one at each side of an amidoamine‐based spacer. This amide‐rich molecule offers many possibilities for forming intra‐ and intermolecular hydrogen bond interactions. Particularly, P1 has an intrinsic property of cocrystallizing with methanol. Compared with the pristine P1 sample, the as‐prepared two‐component cocrystalline material displays an exceptive deep‐blue emission, which is extremely rare among naphthalimide‐based molecules in the solid state. Furthermore, the target material exhibits an obvious mechanochromic fluorescent behavior and a large spectral shift under force stimuli. On the other hand, the cocrystalline material shows an unusual “turn off” thermochromic luminescence accompanied by solvent evaporation. Moreover, using external stimuli to reversibly manipulate fluorescent quantum yields is rarely reported to date. The results demonstrate the feasibility of a new design strategy for solid‐state luminescence switching materials: the incorporation of solvents into organic compounds by cocrystallization to obtain a crystalline state luminescence system. 相似文献
105.
以企业兼并为主要方式的企业资产重组是当前我团经济体制改革的热点之一。本文从实际出发,阐明企业兼并对我国经济建设的意义,分析近十多年来我国企业兼并的基本特征及存在的问题,并提出相关的解决问题的对策建议。 相似文献
106.
Novel GaInSbAs/GaSb multiple-quantum-well lasers operating near room temperature have been successfully used for tunable diode laser absorption spectroscopy in the vicinity of 2.35 mum. Continuous current tuning over a more than 150-GHz frequency range has been realized. Direct absorption measurements have been carried out on the R, R, R, and R lines of carbon monoxide. Traces of carbon monoxide at the level of 0.3 part in 10(6) in volume at 100 Torr could be detected by the low-frequency wavelength-modulation technique and an astigmatic multipass cell. These results show a potential use of these diode lasers in portable low-cost trace-pollutant sensors. 相似文献
107.
Emmanuel Bruno Nicolas Faessel Herv�� Glotin Jacques Le Maitre Michel Scholl 《World Wide Web》2011,14(5-6):623-649
We present in this paper a model for indexing and querying web pages, based on the hierarchical decomposition of pages into blocks. Splitting up a page into blocks has several advantages in terms of page design, indexing and querying such as (i) blocks of a page most similar to a query may be returned instead of the page as a whole (ii) the importance of a block can be taken into account, as well as (iii) the permeability of the blocks to neighbor blocks: a block b is said to be permeable to a block b?? in the same page if b?? content (text, image, etc.) can be (partially) inherited by b upon indexing. An engine implementing this model is described including: the transformation of web pages into blocks hierarchies, the definition of a dedicated language to express indexing rules and the storage of indexed blocks into an XML repository. The model is assessed on a dataset of electronic news, and a dataset drawn from web pages of the ImagEval campaign where it improves by 16% the mean average precision of the baseline. 相似文献
108.
运用量子化学微扰理论MP2方法,采用6-311++G(d,p)基组,对吡咯与双卤分子XY(XY=ClF,BrF,BrCl)形成的卤键复合物进行构型全优化,得到各分子的稳定几何构型和分子间相互作用能.利用电子密度拓扑分析方法分析卤键复合物的拓扑性质,探讨了该类分子间卤键的作用本质.证明吡咯与双卤分子间存在Y-X...N和Y-X...π2类相互作用,且后者比前者强.复合物中的卤键介于共价键与离子键之间,偏于静电作用成分为主.形成卤键后,2种类型卤键复合物中的电子受体X-Y键伸长,其振动频率发生红移.用电子密度拓扑分析程序GTA-2000,将π型卤键体系中π电子与σ电子分开处理,绘制出π电子密度等值线图和Laplacian量等值线图,更加形象地说明π型卤键的存在和作用本质.利用AIM程序计算了卤键复合物中各原子电子积分的性质,原子积分性质随着卤键形成发生了改变. 相似文献
109.
Jose Gonzalez-Mora Fernando De la Torre Nicolas Guil Emilio L. Zapata 《Image and vision computing》2010
Over the last decade 3D face models have been extensively used in many applications such as face recognition, facial animation and facial expression analysis. 3D Morphable Models (MMs) have become a popular tool to build and fit 3D face models to images. Critical to the success of MMs is the ability to build a generic 3D face model. Major limitations in the MMs building process are: (1) collecting 3D data usually involves the use of expensive laser scans and complex capture setups, (2) the number of available 3D databases is limited, and typically there is a lack of expression variability and (3) finding correspondences and registering the 3D model is a labor intensive and error prone process. 相似文献
110.