全文获取类型
收费全文 | 6900篇 |
免费 | 161篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 497篇 |
综合类 | 18篇 |
化学工业 | 1721篇 |
金属工艺 | 202篇 |
机械仪表 | 166篇 |
建筑科学 | 215篇 |
矿业工程 | 1篇 |
能源动力 | 299篇 |
轻工业 | 590篇 |
水利工程 | 24篇 |
石油天然气 | 7篇 |
无线电 | 500篇 |
一般工业技术 | 1250篇 |
冶金工业 | 684篇 |
原子能技术 | 256篇 |
自动化技术 | 659篇 |
出版年
2023年 | 41篇 |
2022年 | 80篇 |
2021年 | 121篇 |
2020年 | 65篇 |
2019年 | 72篇 |
2018年 | 94篇 |
2017年 | 82篇 |
2016年 | 133篇 |
2015年 | 95篇 |
2014年 | 189篇 |
2013年 | 377篇 |
2012年 | 220篇 |
2011年 | 357篇 |
2010年 | 306篇 |
2009年 | 312篇 |
2008年 | 359篇 |
2007年 | 328篇 |
2006年 | 254篇 |
2005年 | 268篇 |
2004年 | 220篇 |
2003年 | 200篇 |
2002年 | 206篇 |
2001年 | 151篇 |
2000年 | 129篇 |
1999年 | 159篇 |
1998年 | 307篇 |
1997年 | 199篇 |
1996年 | 150篇 |
1995年 | 113篇 |
1994年 | 130篇 |
1993年 | 113篇 |
1992年 | 79篇 |
1991年 | 89篇 |
1990年 | 73篇 |
1989年 | 94篇 |
1988年 | 84篇 |
1987年 | 56篇 |
1986年 | 96篇 |
1985年 | 75篇 |
1984年 | 68篇 |
1983年 | 68篇 |
1982年 | 79篇 |
1981年 | 57篇 |
1980年 | 57篇 |
1979年 | 43篇 |
1978年 | 52篇 |
1977年 | 38篇 |
1976年 | 54篇 |
1975年 | 24篇 |
1973年 | 18篇 |
排序方式: 共有7089条查询结果,搜索用时 15 毫秒
1.
2.
Shouko Nishida Masaya Shibano Hiroshi Kamitakahara Toshiyuki Takano 《International journal of molecular sciences》2015,16(12):29093-29102
We recently observed that the decanoylation of N-phenylthiocarbamoyl chitosan (2) with a mixture of decanoic anhydride and pyridine at 60 °C for 24 h afforded N,N-(decanoyl)phenythiocarbamoyl-/2-isothiocynato chitosan decanoate (3b) rather than the expected product N,N-(decanoyl)phenylthiocarbamoyl chitosan decanoate (3a). This result suggested that some of the N,N-(decanoyl)phenylthiocarmbamoyl groups had been converted to isothiocyanate groups during the decanoylation process. The subsequent reaction of compound 3b with aniline gave N,N-(decanoyl)phenylthiocarbamoyl/N-phenylthiocarbamoyl chitosan decanoate (4) in high yield. A solution of compound 4 in CHCl3 was then added to a solution of copper decanoate (5) in the same solvent, and the resulting mixture was cast onto a glass plate to give a cast film. The film was annealed at 200 °C in an oven to give a greenish film, which showed good near-infrared absorption characteristic in the range of 800–2200 nm. 相似文献
3.
4.
A Synthetic Transcriptional Activator of Genes Associated with the Retina in Human Dermal Fibroblasts
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
5.
Eicosapentaenoic acid (EPA) production by an oleaginous fungus Mortierella alpina expressing heterologous the Δ17‐desaturase gene under ordinary temperature
下载免费PDF全文
![点击此处可从《European Journal of Lipid Science and Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
6.
Hiroshi Takamatsu Hikaru Yamashiro Nobuo Takata Hiroshi Honda 《International Journal of Refrigeration》2003,26(6):79
Heat and mass transfer in a falling film vertical in-tube absorber was studied experimentally with LiBr aqueous solution. The presented results include the effect of solution flow rate, solution subcooling and cooling water temperature on the absorption in a smooth copper tube 16.05 mm I.D. and 400 mm long. The experimental data in the previous report for a 1200-mm-long tube was also re-examined and compared. It was demonstrated by the observation of the flow in the tube that the break down of the liquid film into rivulets leads to deterioration of heat and mass transfer at lower film Reynolds number or in longer tubes. An attempt to evaluate physically acceptable heat and mass transfer coefficients that are defined with estimated temperature and concentration at the vapor–liquid interface was also presented. 相似文献
7.
BaCuQF (Q=S, Se, Te) materials exhibit band gaps that allow transmission of much of the visible spectrum. BaCuSF is transparent in thin-film form with a band gap of 3.1 eV. Band gap estimates for powders of the solid solution series BaCuS1−xSexF were obtained from wavelength-dependent diffuse-reflectance measurements using an integrating sphere. The band gap can be tuned by the substitution of Se for S to 2.9 eV for BaCuSeF. The decrease scales almost linearly with the increase in the volume of the tetragonal unit cell, which is determined primarily by the expansion of the a lattice parameter; the overall volume increase is 7.0% from x=0 to 1. Further reduction of the band gap is observed in BaCuSe1−xTexF solid solutions, where a unit cell volume increase of 5.5% produces a band gap of 2.7 eV in BaCuSe0.5Te0.5F. Powders and films of BaCuSF exhibit strong red luminescence under ultraviolet excitation, which is suppressed by K doping. Additional tuning of band gap and electrical properties (the materials are p-type conductors) can be achieved by replacing Ba with Sr. 相似文献
8.
N Usui S Kamata S Ishikawa T Sawai H Okuyama K Imura A Okada 《Canadian Metallurgical Quarterly》1996,31(2):258-262
Bone marrow examination revealed a lipid-laden histiocytosis in seven patients undergoing long-term total parenteral nutrition necessitated by extensive short-bowel surgical resection. Clinical abnormalities occurred during this treatment which required bone marrow examination. These included hepatosplenomegaly and peripheral blood cytopenia; the median time to the detection of these abnormalities was 64 months. The most striking change within the bone marrow was the presence of many pigment-laden histiocytes which had the typical morphology of sea-blue histiocytes seen in the so-called idiopathic sea-blue histiocyte syndrome. The occurrence of sea-blue histiocytosis in the bone marrow in association with long-term parenteral nutrition for short-bowel syndrome has not, to our knowledge, been reported previously and should now be considered in the differential diagnosis of bone marrow sea-blue histiocytosis. 相似文献
9.
Michio Kumagai Kanako Ishikawa Jiao Chunmeng 《Lakes & Reservoirs: Research and Management》2002,7(4):345-348
We have examined two aspects of the dynamics and biogeochemical significance of the physical environment in Lake Biwa. One is the horizontal distribution of cyanobacteria as it relates to the ‘first gyre’ in the north basin of Lake Biwa. We could easily measure the first gyre using a vessel‐mounted acoustic doppler currents profiler. We were able to quantify the dynamics of the horizontal and vertical structure of currents and water temperature of this gyre. The first gyre did not remain at a fixed position; it moved north and south according to the growth of the gyre. This may play a role in the redistribution of cyanobacteria from place to place in the north basin. The second important environmental dynamic we measured was oxygen consumption rates from 1994 to 2000. We found that the minimum oxygen concentration in the hypolimnion has a clear inverse relationship with the apparent oxygen consumption rates in the 80–85 m depth layer. As a reduction in oxygen concentration in the hypolimnion can have a serious impact on benthic organisms, we concluded that the Lake Biwa environment should be monitored carefully and systematically. 相似文献
10.