全文获取类型
收费全文 | 304418篇 |
免费 | 22729篇 |
国内免费 | 13413篇 |
专业分类
电工技术 | 18385篇 |
技术理论 | 7篇 |
综合类 | 20008篇 |
化学工业 | 43465篇 |
金属工艺 | 18145篇 |
机械仪表 | 17959篇 |
建筑科学 | 20680篇 |
矿业工程 | 7935篇 |
能源动力 | 7719篇 |
轻工业 | 20039篇 |
水利工程 | 6465篇 |
石油天然气 | 12347篇 |
武器工业 | 2500篇 |
无线电 | 35261篇 |
一般工业技术 | 38989篇 |
冶金工业 | 11731篇 |
原子能技术 | 2712篇 |
自动化技术 | 56213篇 |
出版年
2024年 | 1095篇 |
2023年 | 3685篇 |
2022年 | 7183篇 |
2021年 | 9833篇 |
2020年 | 7510篇 |
2019年 | 5842篇 |
2018年 | 20308篇 |
2017年 | 20472篇 |
2016年 | 16135篇 |
2015年 | 10323篇 |
2014年 | 12600篇 |
2013年 | 14608篇 |
2012年 | 19647篇 |
2011年 | 26649篇 |
2010年 | 24115篇 |
2009年 | 20469篇 |
2008年 | 21473篇 |
2007年 | 21613篇 |
2006年 | 13184篇 |
2005年 | 11559篇 |
2004年 | 8380篇 |
2003年 | 7397篇 |
2002年 | 6558篇 |
2001年 | 5403篇 |
2000年 | 4584篇 |
1999年 | 4032篇 |
1998年 | 2877篇 |
1997年 | 2416篇 |
1996年 | 2232篇 |
1995年 | 1848篇 |
1994年 | 1495篇 |
1993年 | 999篇 |
1992年 | 848篇 |
1991年 | 589篇 |
1990年 | 453篇 |
1989年 | 376篇 |
1988年 | 274篇 |
1987年 | 177篇 |
1986年 | 156篇 |
1985年 | 83篇 |
1984年 | 71篇 |
1983年 | 56篇 |
1982年 | 62篇 |
1981年 | 60篇 |
1980年 | 56篇 |
1968年 | 50篇 |
1965年 | 46篇 |
1959年 | 46篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
Shaofeng Wang Jianwei Xu Yuejin Tong Lin Wang Chaobin He 《Polymer International》2005,54(9):1268-1274
A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry 相似文献
83.
J.A. Bakken L. Barone D. Braun M. Caillat C. Dionisi C. Dor H. Elmamouni F. Ferroni G.L. Grazer J.T. He R. Herbiet B. Ille P. Lecomte E. Longo P.F. Loverre Y.S. Lu J.P. Martin U. Micke R.P. Mount P.A. Pirou H.-G. Sander D. Schmitz M. Schneegans D.P. Stickland R.L. Sumner K.L. Tung E. Valente M. Vivargent 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,228(2-3):294-302
A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained (
) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement. 相似文献
84.
本文介绍了一个用户接口管理系统NUUIMS的设计和实现.重点叙述了该系统基于规范化目标用户接口模型的设计思想,系统组成及描述方法.文章也讨论了使用NUUIMS设计而成的用户接口的特点. 相似文献
85.
86.
Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable
sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L−1 sodium tungstate, potassium iodate and 1 mol L−1 orthophosphoric acid to aqueous solution of 0·1 mol L−1 zirconium(IV) oxychloride. Its ion exchange capacity for Na+ and K+ was found to be 2·20 and 2·35 meq g−1 dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier
transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger
at different temperatures has been studied. The analytical importance of the material has been established by quantitative
separation of Pb2+ from other metal ions. 相似文献
87.
Jonathan P. Belnoue Giang D. Nguyen Alexander M. Korsunsky 《International Journal of Fracture》2007,144(1):53-60
This paper presents a new 1-D non-local damage-plasticity deformation model for ductile materials. It uses the thermodynamic
framework described in Houlsby and Puzrin (2000) and holds, nevertheless, some similarities with Lemaitre’s (1971) approach.
A 1D finite element (FE) model of a bar fixed at one end and loaded in tension at the other end is introduced. This simple
model demonstrates how the approach can be implemented within the finite element framework, and that it is capable of capturing
both the pre-peak hardening and post-peak softening (generally responsible for models instability) due to damage-induced stiffness
and strength reduction characteristic of ductile materials. It is also shown that the approach has further advantages of achieving
some degree of mesh independence, and of being able to capture deformation size effects. Finally, it is illustrated how the
model permits the calculation of essential work of rupture (EWR), i.e. the specific energy per unit cross-sectional area that
is needed to cause tensile failure of a specimen. 相似文献
88.
中国铜冶炼企业的竞争趋势及对策建议 总被引:1,自引:0,他引:1
文章分析了我国大型及中小型铜冶炼企业所面临竞争环境,提出了我国铜冶炼企业应采取的对策建议,即:联合进口原料;走大型企业联合之路,组建中国铜业集团;开发利用海外资源;加大国内资源勘探;继续进行技改、挖潜,提高企业竞争力等。 相似文献
89.
A photochromic nanocomposite based on Keggin structure phosphomolybdic acid (PMoA) well dispersed in polyethyleneglycol (PEG) was fabricated. TEM image showed that PMoA nanoparticles with narrow size distribution were finely dispersed in polymer matrix. FT-IR results showed that the Keggin geometry of polyoxometalates was still preserved inside the composites and strong coulombic interaction was built between PMoA and polymer matrix. Under UV irradiation, the film was reduced photochemically to yield a blue species, which was in accordance with a charge-transfer mechanism. 相似文献
90.
Yewang Su Baohua Ji Yonggang Huang Kehchih Hwang 《Journal of Materials Science》2007,42(21):8885-8893
Wet adhesion is widely adopted in biological adhesion systems in nature. Wet adhesion is studied in this paper with the focus
on the effect of different contact shapes (flat, concave, convex, and ring-like) on the adhesion force. The evolution of the
liquid bridge between a fiber tip and substrate during the detaching process shows two transition points. The first transition
from the radius-controlled to the contact-angle controlled process is critical to influence the strength and robustness of
adhesion. We show that a concave shape is more effective than a flat one, while a convex shape has no advantage. A ring-like
contact shape has advantages in a hydrophobic environment and on a rough surface. 相似文献