全文获取类型
收费全文 | 44973篇 |
免费 | 4940篇 |
国内免费 | 2921篇 |
专业分类
电工技术 | 3531篇 |
技术理论 | 2篇 |
综合类 | 4130篇 |
化学工业 | 6924篇 |
金属工艺 | 2306篇 |
机械仪表 | 2717篇 |
建筑科学 | 3936篇 |
矿业工程 | 1249篇 |
能源动力 | 1216篇 |
轻工业 | 4419篇 |
水利工程 | 1088篇 |
石油天然气 | 2041篇 |
武器工业 | 463篇 |
无线电 | 4674篇 |
一般工业技术 | 4692篇 |
冶金工业 | 1929篇 |
原子能技术 | 587篇 |
自动化技术 | 6930篇 |
出版年
2024年 | 236篇 |
2023年 | 757篇 |
2022年 | 1464篇 |
2021年 | 1965篇 |
2020年 | 1569篇 |
2019年 | 1232篇 |
2018年 | 1338篇 |
2017年 | 1554篇 |
2016年 | 1371篇 |
2015年 | 1985篇 |
2014年 | 2485篇 |
2013年 | 2871篇 |
2012年 | 3169篇 |
2011年 | 3288篇 |
2010年 | 3035篇 |
2009年 | 2847篇 |
2008年 | 3034篇 |
2007年 | 2770篇 |
2006年 | 2627篇 |
2005年 | 2069篇 |
2004年 | 1642篇 |
2003年 | 1577篇 |
2002年 | 1897篇 |
2001年 | 1665篇 |
2000年 | 1113篇 |
1999年 | 816篇 |
1998年 | 493篇 |
1997年 | 451篇 |
1996年 | 382篇 |
1995年 | 295篇 |
1994年 | 213篇 |
1993年 | 126篇 |
1992年 | 120篇 |
1991年 | 80篇 |
1990年 | 62篇 |
1989年 | 60篇 |
1988年 | 49篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 25篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1974年 | 3篇 |
1959年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
1 Introduction Owing to the effect of crosswind, initial disturbance and the deviation of engine parameters.etc in the initial aviation, variable rolling velocity aerocraft will produce attitude angle deviation (AAD) in the ideal orientations. It must control the attitude of the aerocraft, accordingly, AAD of aerocraft can be amended.Angle stabilization control system is used for the attitude control of rolling aerocraft by this paper. This control system is generally located in the control… 相似文献
192.
国家粮储库屋面防水APP卷材施工技术 总被引:1,自引:0,他引:1
针对国家粮食储备库的特点,就屋面防水APP卷材热熔法施工的施工准备及工艺流程进行了介绍,提出了具体的施工技术要点及质量通病的防治措施,取得了良好的施工效果。 相似文献
193.
Jinsheng Que Qing Wang Jianping Chen Bingfei Shi Qinghui Meng 《Bulletin of Engineering Geology and the Environment》2008,67(4):479-483
The paper describes some geotechnical properties of the soft soils in Guangzhou College City, China, which are difficult to
both sample and test. Laboratory and in situ tests were carried out to assess the physical and mechanical indices of the soils.
The data were statistically analyzed and linear regression undertaken such that equations could be developed by which the
geotechnical properties of the soft soils can be predicted. The statistical validity of the degree of correlation confirmed
that using these equations, the mechanical indices can be estimated from physical indices determined by routine testing.
相似文献
194.
A new efficient numerical method and the dynamic analysis of composite laminates with piezoelectric layers 总被引:1,自引:0,他引:1
Firstly, a numerical method for the inversion of Laplace transform is developed and its accuracy is shown through examples. Then, a state-vector equation for the dynamic problems of piezoelectric plates is deduced directly from a modified mixed variational principle for piezoelectric bodies and its exact solution for the dynamic problems of simply supported rectangle piezoelectric plate is simply given. For multilayered hybrid plates, we derive the solution in terms of the propagator matrices. The techniques accounts for the compatibility of generalized displacements and generalized stresses on the interface both the elastic layers and piezoelectric layers, and the transverse shear deformation and the rotary inertia of laminate are also considered in the global algebraic equation of structure. Meanwhile, there is no restriction on the thickness and the number of layers. As an application of the numerical inversion of Laplace transform presented in this paper, typical numerical examples of the harmonic vibration and transient response are proposed and discussed. Since the highly accurate numerical results, they can serve as benchmarks to test various thick plate theories and various numerical methods, such as the finite and boundary element methods for transient response problems. 相似文献
195.
Ching‐Nan Chuang Liang Chao Ying‐Jie Huang Tar‐Hwa Hsieh Hung‐Yi Chuang Shu‐Chi Lin Ko‐Shan Ho 《应用聚合物科学杂志》2008,107(6):3917-3924
The synthesis of a p‐toluidine/formaldehyde (PTF) resin was performed, and the effects of the molar ratio of the individual monomers and the polymerization conditions on the structure of the PTF resin were studied. Fourier transform infrared and 13C‐NMR spectra were used to characterize the PTF. Wide‐angle X‐ray diffraction patterns revealed the crystalline structures of various PTFs. Polarized optical microscopy revealed that the molar ratio of the monomers had a strong effect on the crystalline morphologies. A longer polymerization time turned out a polymer with a higher intrinsic viscosity and molecular weight, which led to differences in the proton conductivity. All of the PTFs showed a higher proton conductivity than a commercial Nafion membrane at 90–100°C and 0% relative humidity. The proton conductivity of the PTF series could be improved by sulfonation with sulfuric acid and could be maintained after blending with polyurethane. Pure methanol could be used as a fuel source because of the insolubility and nonwetting properties of PTF in methanol to increase the output current density for a PTF membrane electrode assembly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
196.
A novel mixed‐mode expanded bed adsorbent with anion‐exchange properties was explored with benzylamine as the functional ligand. The cellulose composite matrix, densified with stainless steel powder, was prepared with the method of water‐in‐oil suspension thermal regeneration. High activation levels of the cellulose matrix were obtained with allyl bromide because of the relative inertness of the allyl group under the conditions of the activation reaction. After the formation of the bromohydrin with N‐bromosuccinimide and coupling with benzylamine, the activated matrix was derived to function as a mixed‐mode adsorbent containing both hydrophobic and ionic groups. The protein adsorption capacity was investigated with bovine serum albumin as a model protein. The results indicated that the prepared adsorbent could bind bovine serum albumin with a high adsorption capacity, and it showed salt tolerance. Effective desorption was achieved by a pH adjustment across the isoelectric point of the protein. The interactions between the cell and adsorbent were studied, and the bioadhesion was shielded by the adjustment of the salt concentration above 0.1M. Stable fluidization in the expanded bed was obtained even in a 2% (dry weight) yeast suspension. The direct capture of target proteins from a biomass‐containing feedstock without extra dilution steps could be expected with the mixed‐mode adsorbent prepared in this work, and this would be especially appropriate for expanded bed adsorption applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
197.
The collagen-chitosan complex nanofibers have been prepared for the first time by electrospinning. The mixed HFP/TFA (the volume ratio of 90/10) was found to be the appropriate solvent for electrospinning. The concentration of the spinning solution and the ratio of chitosan/collagen were varied and adjusted to get smooth nanofibers. It was found that the diameter of the spun fibers became thick with the concentration of the solution increasing and became fine with the ratio of the chitosan/collagen increasing. We have characterised the molecular interactions in collagen-chitosan complex by Fourier transform infrared spectroscopy. The spun fibers are designed to mimic the native extracellular matrix for tissue engineering and to develop functional biomaterials. 相似文献
198.
199.
可编程控制器在恶劣环境下比继电器,接触器安全,可靠,耐用,以水压试验机编程控制器程序控制为例。阐述了液压,气动。电气联合作用下系统的可编程控制设计方法以及防干扰措施。 相似文献
200.
复杂连通区域扫描线填充算法的问题及改进 总被引:1,自引:0,他引:1
针对复杂连通区域扫描线填充算法可能出现的重复填充错误,分析了产生错误的原因,并给出了相应的改进办法.从而实现了复杂连通区域的快速正确填充。 相似文献