全文获取类型
收费全文 | 2087篇 |
免费 | 95篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 24篇 |
综合类 | 16篇 |
化学工业 | 593篇 |
金属工艺 | 45篇 |
机械仪表 | 33篇 |
建筑科学 | 146篇 |
矿业工程 | 3篇 |
能源动力 | 31篇 |
轻工业 | 171篇 |
水利工程 | 19篇 |
石油天然气 | 3篇 |
无线电 | 139篇 |
一般工业技术 | 402篇 |
冶金工业 | 192篇 |
原子能技术 | 16篇 |
自动化技术 | 354篇 |
出版年
2023年 | 24篇 |
2022年 | 50篇 |
2021年 | 71篇 |
2020年 | 40篇 |
2019年 | 47篇 |
2018年 | 44篇 |
2017年 | 42篇 |
2016年 | 54篇 |
2015年 | 47篇 |
2014年 | 76篇 |
2013年 | 100篇 |
2012年 | 100篇 |
2011年 | 161篇 |
2010年 | 105篇 |
2009年 | 122篇 |
2008年 | 115篇 |
2007年 | 88篇 |
2006年 | 90篇 |
2005年 | 78篇 |
2004年 | 74篇 |
2003年 | 61篇 |
2002年 | 58篇 |
2001年 | 49篇 |
2000年 | 43篇 |
1999年 | 44篇 |
1998年 | 44篇 |
1997年 | 35篇 |
1996年 | 24篇 |
1995年 | 25篇 |
1994年 | 35篇 |
1993年 | 21篇 |
1992年 | 12篇 |
1991年 | 25篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1970年 | 6篇 |
1969年 | 6篇 |
1968年 | 10篇 |
1967年 | 5篇 |
排序方式: 共有2187条查询结果,搜索用时 15 毫秒
91.
通过调查得知,包括虚拟现实技术在机床制造中应用可能性的应用方法、策略和工具在产品开发中的现状.对调查结果进行了讨论,考虑到研究理论的可移植性和对企业内部实战的依赖性.讨论的结果为基础研究领域的命题"基于职能单位的产品开发"提供结论. 相似文献
92.
93.
94.
Matilda Zemanov Emmanuel Lecomte Pavol
ajgalík Ralf Riedel 《Journal of the European Ceramic Society》2002,22(16):2963-2968
The pyrolised polysilazanes poly(hydridomethyl)silazane NCP 200 and poly(urea)silazane CERASET derived Si–C–N amorphous powders were used for preparation of micro/nano Si3N4/SiC composites by hot pressing. Y2O3–Al2O3 and Y2O3–Yb2O3 were used, as sintering aids. The resulting ceramic composites of all compositions were dense and polycrystalline with fine microstructure of average grain size <1 μm of both Si3N4 and SiC phases. The fine SiC nano-inclusions were identified within the Si3N4 micrograins. Phase composition of both composites consist of , β modifications of Si3N4 and SiC. High weight loss was observed during the hot pressing cycle, 12 and 19 wt.% for NCP 200 and CERASET precursors, respectively. The fracture toughness of both nanocomposites (NCP 2000 and CERASET derived) was not different. Indentation method measured values are from 5 to 6 MPa m1/2, with respect to the sintering additive system. Fracture toughness is slightly sensitive to the SiC content of the nanocomposite. Hardness increases with the content of SiC in the nanocomposite. The highest hardness was achieved for pyrolysed CERASET precursor with 2 wt.% Y2O3 and 6 wt.% Yb2O3, HV 23 GPa. This is a consequence of the highest SiC content as well as the chemical composition of additives. 相似文献
95.
Karolina Mazur Raminder Singh Ralf P. Friedrich Hatice Gen Harald Unterweger Kamila Saasiska Rafa Bogucki Stanisaw Kuciel Iwona Cicha 《大分子材料与工程》2020,305(9)
The composites based on polylactide (PLA) and poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) with the addition of antibacterial particles: silver (Ag) and copper oxide (CuO) are characterized. Basic mechanical properties and biodegradation processes, as well as biocompatibility of materials with human cells are determined. The addition of Ag or CuO to the polymers do not significantly affect their mechanical properties, flammability, or biodegradation rate. However, several differences between the base materials are observed. PLA‐based composites have higher tensile and impact strength values, while PHBV‐based ones have a higher modulus of elasticity, as well as better mechanical properties at elevated temperatures. Concerning biocompatibility, each of the tested materials support the growth of fibroblasts over time, although large differences are observed in the initial cell attachment. The analysis of hydrolytic degradation effects on the structure of materials shows that PHBV degrades much faster than PLA. The results of this study confirm the good potential of the investigated biodegradable polymer composites with antibacterial particles for future biomedical applications. 相似文献
96.
Treatment of strongflow wool scouring effluent by biological emulsion destabilisation 总被引:4,自引:0,他引:4
The stable oil-in-water emulsion contained in wool scouring effluent was destabilised by aerobic biological treatment as the basis of a potential new effluent treatment process. The de-emulsified wool wax, which is recalcitrant to biodegradation, can then be readily removed by centrifugation. In 12-day batch experiments, 97% of wool wax and 87% of COD were removed after gentle centrifuging at 200 x g, compared to only 6% and 8%, respectively, for sterile controls. Steady-state chemostat experiments under optimum conditions gave essentially complete removal of wool wax and 90% removal of COD at less than 40 h retention time, and demonstrated that the mechanism of pollutant removal was by bioflocculation rather than aerobic degradation. At 100 L pilot scale, 95% of wool wax and 82% of COD were consistently removed over a period of 116 days of continuous operation at 38 h retention time and 30 degrees C, producing a spadable sludge of 5.7 mL/g. Variable influent concentration or filamentous bacteria did not disrupt this process and foaming was readily controlled using a mechanical foam breaker. After a shutdown period of 15 days the process could be restarted easily, achieving normal performance within one retention time. The successful operation of the pilot reactor suggests this process could be developed to full scale and incorporated into an overall treatment package. 相似文献
97.
Cai M Zhao Z Yin Z Ahrens L Huang P Cai M Yang H He J Sturm R Ebinghaus R Xie Z 《Environmental science & technology》2012,46(2):661-668
Perfluoroalkyl compounds (PFCs) were determined in 22 surface water samples (39-76°N) and three sea ice core and snow samples (77-87°N) collected from North Pacific to the Arctic Ocean during the fourth Chinese Arctic Expedition in 2010. Geographically, the average concentration of ∑PFC in surface water samples were 560 ± 170 pg L(-1) for the Northwest Pacific Ocean, 500 ± 170 pg L(-1) for the Arctic Ocean, and 340 ± 130 pg L(-1) for the Bering Sea, respectively. The perfluoroalkyl carboxylates (PFCAs) were the dominant PFC class in the water samples, however, the spatial pattern of PFCs varied. The C(5), C(7) and C(8) PFCAs (i.e., perfluoropentanoate (PFPA), perfluoroheptanoate (PFHpA), and perfluorooctanoate (PFOA)) were the dominant PFCs in the Northwest Pacific Ocean while in the Bering Sea the PFPA dominated. The changing in the pattern and concentrations in Pacific Ocean indicate that the PFCs in surface water were influenced by sources from the East-Asian (such as Japan and China) and North American coast, and dilution effect during their transport to the Arctic. The presence of PFCs in the snow and ice core samples indicates an atmospheric deposition of PFCs in the Arctic. The elevated PFC concentration in the Arctic Ocean shows that the ice melting had an impact on the PFC levels and distribution. In addition, the C(4) and C(5) PFCAs (i.e., perfluorobutanoate (PFBA), PFPA) became the dominant PFCs in the Arctic Ocean indicating that PFBA is a marker for sea ice melting as the source of exposure. 相似文献
98.
Carl-Friedrich Krger Ralf Miethchen Hanna Mann Klaus Hoffmann Kurt Wiechert 《Advanced Synthesis \u0026amp; Catalysis》1978,320(6):881-903
Acid-catalyzed Reactions of Aromatic Hydrocarbons with Alkanes and Cycloalkanes. IX. Alkylations with 2,2,4-Trimethylpentane (Isooctane) The non-conventional alkylation of benzene, toluene, ethyl- and isopropylbenzene, fluoro- and chlorobenzene with 2,2,4-trimethylpentane in the presence of acid catalysts is described. The composition of the rather complex reaction mixtures is determined by gas-liquid chromatography and mass spectrometry, tert. butylarenes being the main products beside alkylsubstituted indanes and tetralines. Their formation is interpreted as a competition between fragmentation and isomerization of the alkylating agent. By use of trifluoromethanesulfonic acid or combinations of catalysts from HF or HSO3F with variant metallic fluorides at lower temperatures the selectivity of the reaction may be partially raised. 相似文献
99.
100.