全文获取类型
收费全文 | 421224篇 |
免费 | 34548篇 |
国内免费 | 18947篇 |
学科分类
工业技术 | 474719篇 |
出版年
2024年 | 1185篇 |
2023年 | 5859篇 |
2022年 | 10079篇 |
2021年 | 15395篇 |
2020年 | 11548篇 |
2019年 | 9747篇 |
2018年 | 10871篇 |
2017年 | 12344篇 |
2016年 | 11468篇 |
2015年 | 15466篇 |
2014年 | 20371篇 |
2013年 | 25222篇 |
2012年 | 26772篇 |
2011年 | 29392篇 |
2010年 | 25740篇 |
2009年 | 24973篇 |
2008年 | 24454篇 |
2007年 | 23294篇 |
2006年 | 23773篇 |
2005年 | 20585篇 |
2004年 | 14522篇 |
2003年 | 13222篇 |
2002年 | 13507篇 |
2001年 | 11763篇 |
2000年 | 10559篇 |
1999年 | 10790篇 |
1998年 | 9340篇 |
1997年 | 7635篇 |
1996年 | 6939篇 |
1995年 | 5851篇 |
1994年 | 4958篇 |
1993年 | 3728篇 |
1992年 | 2843篇 |
1991年 | 2230篇 |
1990年 | 1712篇 |
1989年 | 1487篇 |
1988年 | 1164篇 |
1987年 | 784篇 |
1986年 | 610篇 |
1985年 | 463篇 |
1984年 | 334篇 |
1983年 | 262篇 |
1982年 | 255篇 |
1981年 | 226篇 |
1980年 | 202篇 |
1979年 | 148篇 |
1978年 | 82篇 |
1977年 | 100篇 |
1976年 | 102篇 |
1975年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
World Wide Web - Rule mechanism has been widely used in many areas, such as databases, artificial intelligent and pervasive computing. In a rule mechanism, rule activation decides which rules are... 相似文献
103.
Amino acid modified polyaspartic acids were evaluated as calcium-scale inhibitors. Feasibility of scale inhibition experiments was analyzed by molecular dynamics simulation and Gaussian optimization, and the scale inhibition mechanism was theoretically analyzed. Scale inhibition performance was studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, static scale inhibition experiments, and electrochemical performance testing, which provided an experimental basis for the molecular dynamics simulation. The experimental results showed that Arg-SA-PASP has better scale inhibition and corrosion inhibition performance than His-SA-PASP. The scale inhibition effect increased with increasing concentration. Electrochemical tests indicated that Arg-SA-PASP is an excellent scale and corrosion inhibitor. 相似文献
104.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文
105.
106.
Polymer‐grafted inorganic particles (PGIPs) are attractive building blocks for numerous chemical and material applications. Surface‐initiated controlled radical polymerization (SI‐CRP) is the most feasible method to fabricate PGIPs. However, a conventional in‐batch reaction still suffers from several disadvantages, including time‐consuming purification processes, low grafting efficiency, and possible gelation problems. Herein, a facile method is demonstrated to synthesize block copolymer–grafted inorganic particles, that is, poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMEMA)‐b‐poly(N‐isopropylacrylamide) (PNIPAM)–grafted silica micro‐particles using continuous flow chemistry in an environmentally friendly aqueous media. Immobilizing the chain transfer agent and subsequent SI‐CRP can be accomplished sequentially in a continuous flow system, avoiding multi‐step purification processes in between. The chain length (MW) of the grafted polymers is tunable by adjusting the flow time or monomer concentration, and the narrower molar mass dispersity (Ð < 1.4) of the grafted polymers reveals the uniform polymer chains on the particles. Moreover, compared with the in‐batch reaction at the same condition, the continuous system also suppresses possible gelation problems. 相似文献
107.
108.
Xueye Chen Yue Tian 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(3):806-812
Since the beginning of the 21st Century, the development of microfluidic chip technology has been very rapid and has attracted the attention of more and more scholars. As an important part of the microfluidic chip, the performance of the micromixer is critical. The fractal structure in the microchannels helps to improve the mixing performance of the micromixer and improve the mixing efficiency of the micromixer. The research results of other scholars are of great significance to the research of the present paper, which mainly studies the effect of changing the baffle state on the mixing efficiency of the micromixer based on the Koch fractal principle. Through simulation analysis, it was found that the mixing efficiency of the baffles distributed on both sides of the microchannel was higher than the mixing efficiency of the baffles distributed on the microchannel side. When the distance between adjacent baffles was divided into 0.15, 0.25 and 0.35 mm, simulated data suggested that the baffle distance of 0.15 mm was best. Increasing the number of baffles from six to eight groups increased the mixing path of the fluid in the microchannel and improved mixing efficiency. A comparison of mixing efficiencies of the 0°, 15° and 30° baffle angles revealed that very significant improvement in mixing efficiency was obtained at 30°. © 2019 Society of Chemical Industry 相似文献
109.
110.