全文获取类型
收费全文 | 6651篇 |
免费 | 1107篇 |
国内免费 | 128篇 |
专业分类
电工技术 | 28篇 |
综合类 | 299篇 |
化学工业 | 3894篇 |
金属工艺 | 38篇 |
机械仪表 | 33篇 |
建筑科学 | 91篇 |
矿业工程 | 28篇 |
能源动力 | 133篇 |
轻工业 | 1621篇 |
水利工程 | 15篇 |
石油天然气 | 93篇 |
武器工业 | 23篇 |
无线电 | 297篇 |
一般工业技术 | 1204篇 |
冶金工业 | 31篇 |
原子能技术 | 38篇 |
自动化技术 | 20篇 |
出版年
2024年 | 97篇 |
2023年 | 264篇 |
2022年 | 285篇 |
2021年 | 426篇 |
2020年 | 376篇 |
2019年 | 365篇 |
2018年 | 297篇 |
2017年 | 355篇 |
2016年 | 321篇 |
2015年 | 324篇 |
2014年 | 382篇 |
2013年 | 483篇 |
2012年 | 497篇 |
2011年 | 428篇 |
2010年 | 319篇 |
2009年 | 326篇 |
2008年 | 242篇 |
2007年 | 319篇 |
2006年 | 294篇 |
2005年 | 240篇 |
2004年 | 162篇 |
2003年 | 152篇 |
2002年 | 142篇 |
2001年 | 118篇 |
2000年 | 120篇 |
1999年 | 105篇 |
1998年 | 85篇 |
1997年 | 61篇 |
1996年 | 44篇 |
1995年 | 32篇 |
1994年 | 45篇 |
1993年 | 47篇 |
1992年 | 33篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 11篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 15篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有7886条查询结果,搜索用时 15 毫秒
1.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation 下载免费PDF全文
2.
P. Meenakshi S. E. Noorjahan R. Rajini U. Venkateswarlu C. Rose T. P. Sastry 《Bulletin of Materials Science》2002,25(1):25-29
DriedMusa paradiciaca (banana) stem and veins of the leaves, which were hitherto discarded as a waste, were collected and used as starting material
for the preparation of cellulose and cellulose acetate. This cellulose acetate was mixed with polystyrene to form blend of
cellulose acetate-polystyrene in order to provide enhanced stability and extended utility to the end products. The films of
these composites or their individual partners were made separately and studied for their mechanical properties, chemical modification
and morphological changes. We report here that banana stem is good source of cellulose and that cellulose completely undergoes
modification upon esterification. 相似文献
3.
纤维素经高能射线辐照,能产生一系列的化学和物理性质的变化。本文报道在不同剂量的~(60)Coγ射线辐照下,稻草中的水溶性糖、易水解糖、难水解糖,以及氨基酸、蛋白质等物质的化学变化;用辐射与加泡涨剂相结合的方法处理稻草,可以降低剂量、提高效应。 相似文献
4.
5.
Carboxymethyl-2-diethylaminoethylcellulose (CM-DEAE cellulose) was prepared by etherification of carboxymethylcellulose with diethylaminoethyl chloride in a NaOH solution. The behaviour of CM-DEAE cellulose in aqueous solution was studied by viscosity and GPC measurements. The degree of substitution (DS) and existing states of DEAE substituents were examined by the use of proton NMR, and those of the CM substituents were observed with FT-IR. The results reveal that the reduced viscosity and apparent molecular size of CM-DEAE cellulose vary with the concentration of sodium chloride and changes in pH and DS. These phenomena can be explained in terms of inter- and intra-molecular ionic interactions. 相似文献
6.
氧浓度对近临界水中纤维素分解的影响 总被引:3,自引:0,他引:3
研究了不同初始氧浓度对纤维素在近临界水中分解的影响,实验结果表明,氧浓度显著地影响产物总碳收支平衡,液相不同组分的收率、气体的产量以及气相产物的组成,微量氧对产物总碳收支平衡影响不大,而对液相不同组分的收率有一定的影响。从实验结果可以看出,离子型反应机理在纤维素水解的第一步中起主导作用。而单糖的进一步分解是一个以自由基反应机理为主的过程。 相似文献
7.
Swelling degrees of poly(N-vinyl-2-pyrrolidone) (PVP) gel were measured in aqueous salt solutions and in water/organic solvent mixtures to find marked ion- and solvent-specificities. In order to investigate any correlation of those specificities with hydration or solvation of PVP, IR spectra band of the CO group was monitored by means of ATR method both for PVP gel and the relevant solution systems. Dependence of the peak frequency on the swelling ratio suggested that hydration of PVP carbonyl group in deswollen gel systems is different from that in the corresponding solution systems. In the solution systems, PVP carbonyl band showed a high-wavenumber shift for deswollen systems, which can be well correlated with changes in water proton charge through ionic hydration and with Gutmann's acceptor number of organic solvents. In the deswollen gel systems, the CO band showed a low-wavenumber shift, suggesting a strong hydration or doubly hydrated state. This unexpected behavior was interpreted by assuming an intermolecular hydrogen bond of two carbonyl groups intermediated by water molecules. 相似文献
8.
共聚物水凝胶的合成及其溶胀性能研究 总被引:3,自引:1,他引:2
以过氧化二苯甲酰(BPO)为引发剂,合成了N-乙烯基吡咯烷酮(NVP)-甲基丙烯酸肛羟乙酯(HEMA)-甲基丙烯酸丁酯(BMA)共聚物水凝胶,可作为软性角膜接触镜材料。探讨了不同比例的NVP、HEMA、BMA对材料溶胀性能的影响。 相似文献
9.
Highly transparent cellulose hydrogels with physical crosslinkage were prepared from nonaqueous organic cellulose solutions and viscose by coagulating and regenerating cellulose in an aqueous solution containing a water‐miscible organic solvent. Nonaqueous organic cellulose solutions used were LiCl/dimethylacetamide, paraformaldehyde/dimethyl sulfoxide, and triethylammonium chloride/dimethyl sulfoxide. Preparation conditions and physical properties of the transparent cellulose hydrogels were studied. The transparency of the cellulose hydrogels depended on the composition of the aqueous solution containing the organic solvent. Furthermore, transparent cellulose hydrogels from viscose showed high tensile strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3020–3025, 2003 相似文献
10.
The first part of this paper analyses the influence of the molecular weight and concentration of carboxymethyl cellulose (CMC) and of kaolin concentration on rheology of the coating colours and on paper properties coated with ultra lightweight coatings (ULWC). In the second part, relationships between the rheological characteristics of the coating colour formulations and coated paper surface quality was also studied.New indexes on paper roughness at micro-scale are presented (RZI and SRI). In general, they show good correlation with sheet gloss. A new gloss index (SGI) is presented, accounting for the contribution of gloss from machine direction (MD) and cross direction (CD). Porosimetry was used to access microstructural characteristics in order to correlate them with light scattering and gloss properties. The former property is closely related to Hg intrusion volume of the coated layer while gloss is related to surface porosity with pore diameters in the range of 7–15 μm as measured by Hg intrusion volume. 相似文献