全文获取类型
收费全文 | 10840篇 |
免费 | 1188篇 |
国内免费 | 679篇 |
专业分类
电工技术 | 438篇 |
综合类 | 1029篇 |
化学工业 | 1730篇 |
金属工艺 | 637篇 |
机械仪表 | 525篇 |
建筑科学 | 1485篇 |
矿业工程 | 455篇 |
能源动力 | 202篇 |
轻工业 | 147篇 |
水利工程 | 243篇 |
石油天然气 | 1288篇 |
武器工业 | 42篇 |
无线电 | 1295篇 |
一般工业技术 | 959篇 |
冶金工业 | 304篇 |
原子能技术 | 41篇 |
自动化技术 | 1887篇 |
出版年
2024年 | 48篇 |
2023年 | 119篇 |
2022年 | 218篇 |
2021年 | 272篇 |
2020年 | 271篇 |
2019年 | 257篇 |
2018年 | 218篇 |
2017年 | 304篇 |
2016年 | 327篇 |
2015年 | 375篇 |
2014年 | 687篇 |
2013年 | 645篇 |
2012年 | 881篇 |
2011年 | 874篇 |
2010年 | 674篇 |
2009年 | 728篇 |
2008年 | 678篇 |
2007年 | 775篇 |
2006年 | 688篇 |
2005年 | 571篇 |
2004年 | 496篇 |
2003年 | 513篇 |
2002年 | 427篇 |
2001年 | 320篇 |
2000年 | 273篇 |
1999年 | 219篇 |
1998年 | 190篇 |
1997年 | 130篇 |
1996年 | 108篇 |
1995年 | 92篇 |
1994年 | 88篇 |
1993年 | 58篇 |
1992年 | 39篇 |
1991年 | 28篇 |
1990年 | 25篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
东营凹陷滚动勘探开发技术研究与应用 总被引:4,自引:0,他引:4
东营凹陷已进入勘探开发成熟期 ,滚动勘探开发是增储稳产的主要手段 ,精细油藏描述是其关键。总结滚动勘探开发的 4种方式 (老区扩边、发现新块、发现新层系和新区滚动勘探开发 ) ,对断块复杂程度提出按每平方千米内所有断层的累加长度划分的新方法 ,从构造描述、储集层描述和油藏描述方面介绍了滚动勘探开发的技术方法。以永 8断块为例 ,在层位标定、反射特征分析、构造描述流程、地震地质分析等方面进行深入分析 ,归纳精细油藏描述的具体方法 ,强调了三维地震数据体的相干分析、属性分析等技术的重要作用。应用这一滚动勘探开发技术 ,使东营凹陷每年新增滚动储量近2 0 0 0× 10 4 t。图 3参 10 相似文献
62.
Fault-based side channel cryptanalysis is very effective against symmetric and asymmetric encryption algorithms. Although straightforward hardware and time redundancy based concurrent error detection (CED) architectures can be used to thwart such attacks, they entail significant overhead (either area or performance). In this paper we investigate two systematic approaches to low-cost, low-latency CED for symmetric encryption algorithm RC6. The proposed techniques have been validated on FPGA implementations of RC6, one of the advanced encryption standard finalists. 相似文献
63.
H.‐G. Boyen G. Kstle K. Zürn T. Herzog F. Weigl P. Ziemann O. Mayer C. Jerome M. Mller J.P. Spatz M.G. Garnier P. Oelhafen 《Advanced functional materials》2003,13(5):359-364
Starting with Co‐salt‐loaded inverse micelles, which form if the diblock copolymer polystyrene‐block‐poly(2‐vinylpyridine) is dissolved in a selective solvent like toluene and CoCl2 is added to the solution, monomicellar arrays of such micelles exhibiting a significant hexagonal order can be prepared on top of various substrates with tailored intermicellar distances and structure heights. In order to remove the polymer matrix and to finally obtain arrays of pure Co nanoparticles, the micelles are first exposed to an oxygen plasma, followed by a treatment in a hydrogen plasma. Applying in‐situ X‐ray photoelectron spectroscopy, it is demonstrated that: 1) The oxygen plasma completely removes the polymer, though conserving the original order of the micellar array. Furthermore, the resulting nanoparticles are entirely oxidized with a chemical shift of the Co 2p3/2 line pointing to the formation of Co3O4. 2) By the subsequent hydrogen plasma treatment the nanoparticles are fully reduced to metallic Co. 3) By exposing the pure Co nanoparticles for 100 s to various oxygen partial pressures pequation/tex2gif-inf-5.gif, a stepwise oxidation is observed with a still metallic Co core surrounded by an oxide shell. The data allow the extraction of the thickness of the oxide shell as a function of the total exposure to oxygen (pequation/tex2gif-inf-7.gif × time), thus giving the opportunity to control the ferromagnetic–antiferromagnetic composition of an exchange‐biased magnetic system. 相似文献
64.
茨21-133井CO2吞吐技术初步试验 总被引:1,自引:0,他引:1
茨榆坨油田茨13块原油属于普通稠油,1993年开始蒸汽吞吐采油,从第二轮开始效果明显变差,注汽返排率低,有效周期短,产量下降快,套管变形井增多。针对这些问题,在该区块茨21—133井进行CO2吞吐采油工艺现场试验,获得成功,增油效果明显。 相似文献
65.
A method for the synthesis of novel sulfated ionomer of styrene–butadiene–styrene triblock copolymer (SBS) was developed. SBS was first epoxidized by performic acid in the presence of a phase‐transfer catalyst; this was followed by a ring‐opening reaction with an aqueous solution of alkali salt of bisulfate. The optimum conditions for the ring‐opening reaction of the epoxidized SBS with an aqueous solution of KHSO4 were studied. During the ring‐opening reaction, both phase‐transfer catalyst and ring‐opening catalyst were necessary to enhance the conversion of epoxy groups to ionic groups. The products were characterized with Fourier transform infrared spectrophotometry and transmission electron microscopy (TEM). After the potassium ions of the ionomer were substituted with lead ions, the lead sulfated ionomer exhibited dark spots under TEM. Some properties of the sulfated ionomer were studied. With increasing ionic groups or ionic potential of the cations, the water absorbency and emulsifying volume of the ionomer and the intrinsic viscosity of the ionomer solution increased, whereas the oil absorbency decreased. The sulfated ionomer possessed excellent emulsifying properties compared with the sulfonated SBS ionomer. The sodium sulfated ionomers in the presence of 10% zinc stearate showed better mechanical properties than the original SBS. When the ionomer was blended with crystalline polypropylene, a synergistic effect occurred with respect to the tensile strength. The ionomer behaved as a compatibilizer for blending equal amounts of SBS and oil‐resistant chlorohydrin rubber. In the presence of 3% ionomer, the blend exhibited much better mechanical properties and solvent resistance than the blend without the ionomer. SEM photographs indicated improved compatibility between the two components of the blend in the presence of the ionomer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
66.
通过对锯切装置的改进,提高了锯切性能,降低了锯条成本,保证了锯切质量,使设备更加高效、安全的工作。 相似文献
67.
68.
69.
给出了感应电机内部物理过程的框图描述。这种描述准确地反映了电机学中主、漏磁路分别处理的一般方法,感应电机内部各物理量之间的数量关系和电机学所基于的若干基本电磁定律,感应电机内部物理量之间的关系。 相似文献
70.