全文获取类型
收费全文 | 5766篇 |
免费 | 38篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 34篇 |
综合类 | 5篇 |
化学工业 | 608篇 |
金属工艺 | 71篇 |
机械仪表 | 57篇 |
建筑科学 | 129篇 |
矿业工程 | 11篇 |
能源动力 | 47篇 |
轻工业 | 222篇 |
水利工程 | 15篇 |
石油天然气 | 29篇 |
无线电 | 204篇 |
一般工业技术 | 494篇 |
冶金工业 | 3335篇 |
原子能技术 | 43篇 |
自动化技术 | 511篇 |
出版年
2022年 | 22篇 |
2021年 | 28篇 |
2019年 | 31篇 |
2018年 | 27篇 |
2017年 | 42篇 |
2016年 | 39篇 |
2015年 | 27篇 |
2014年 | 43篇 |
2013年 | 195篇 |
2012年 | 100篇 |
2011年 | 122篇 |
2010年 | 83篇 |
2009年 | 102篇 |
2008年 | 125篇 |
2007年 | 116篇 |
2006年 | 122篇 |
2005年 | 124篇 |
2004年 | 110篇 |
2003年 | 93篇 |
2002年 | 76篇 |
2001年 | 81篇 |
2000年 | 61篇 |
1999年 | 164篇 |
1998年 | 882篇 |
1997年 | 478篇 |
1996年 | 362篇 |
1995年 | 245篇 |
1994年 | 188篇 |
1993年 | 216篇 |
1992年 | 59篇 |
1991年 | 57篇 |
1990年 | 79篇 |
1989年 | 83篇 |
1988年 | 80篇 |
1987年 | 83篇 |
1986年 | 77篇 |
1985年 | 83篇 |
1984年 | 53篇 |
1983年 | 60篇 |
1982年 | 45篇 |
1981年 | 69篇 |
1980年 | 52篇 |
1979年 | 61篇 |
1978年 | 61篇 |
1977年 | 87篇 |
1976年 | 137篇 |
1975年 | 42篇 |
1974年 | 44篇 |
1973年 | 28篇 |
1972年 | 20篇 |
排序方式: 共有5815条查询结果,搜索用时 15 毫秒
1.
2.
David J. Lawrence Brianna L. Smith Cameron D. Collard Keyton A. Elliott Kyle L. Fakhoury Jeffery D. Mangold Anna N. Soyka 《International Journal of Hydrogen Energy》2021,46(2):1642-1655
Monolithically-integrated tandem photoanodes were fabricated on substrates consisting of epitaxial n-GaAs1-xPx (x ? 0.32) grown on n+-GaAs wafers. A p+-n junction photovoltaic (PV) cell was first formed by zinc diffusion into the n-GaAs0.68P0.32 from a deposited ZnO coating. After diffusion the ZnO serves as a transparent electrical contact to the resulting p+-GaAs0.68P0.32 surface layer. Transparent, conducting SnO2:F provides chemical and mechanical protection for the ZnO and the underlying PV cell, and it electrically connects this cell to a top BiVO4 photocatalyst layer. In some photoanodes, a WO3 thin film was interposed between the SnO2:F and BiVO4. All oxide coatings were produced by ultrasonic spray pyrolysis except WO3, which was spin coated. Unassisted (unbiased) solar water splitting was achieved, with a solar-to-hydrogen efficiency approaching 2%, without addition of any co-catalyst to the BiVO4 surface. This work can provide insights to other researchers regarding scalable, low cost approaches for the planar monolithic integration of oxide photoanode materials with PV cells to create new tandem devices. 相似文献
3.
4.
JB Kamien WK Bickel BJ Smith GJ Badger JR Hughes 《Canadian Metallurgical Quarterly》1997,58(4):983-991
The percentage of long-term survivors after intensive chemotherapy and the outcome of MDS patients who achieve partial remission (PR) with intensive chemotherapy (IC) are not known. Between 1981 and 1996 we treated 99 patients with de novo MDS who had high-risk MDS or progression to AML, with IC. 41 (41%) achieved CR, 16 (16%) achieved partial remission (PR), 26 (26%) had failure, and 16 (16%) died in aplasia. Eight of the patients who achieved CR were autografted, three were allografted and the remaining cases received moderate consolidation chemotherapy. After IC, the 16 PR patients fulfilled the criteria for RA in 15 cases and CMML in one case. Median PR duration was 17 months, and three PR were > 3 years (39, 50+, 82+ months). Median actuarial survival of patients who achieved PR and CR was 18 months and 20 months from the onset of IC, respectively (difference not significant). Of the 71 patients treated before 1993, with sufficient follow-up, 10 (14%) had survived > 4 years (long-term survivors). Four of them were alive in first CR after 49+ to 110+ months and probably cured, two were alive in PR after 50+ and 82+ months and four had died after 49-78 months. Long-term survivors were characterized by a significantly higher incidence of RAEB-T at diagnosis, and with normal or favourable cytogenetic findings. In patients with RAEB-T at diagnosis included before 1993, 8/23 (35%) cases who had no unfavourable karyotype had survived > 4 years. Our findings suggest that MDS patients who achieve PR with IC, and not only those who achieve CR, can benefit from this type of treatment. The percentage of long-term survivors remains low, however, and is almost restricted to patients with RAEB-T at diagnosis and no unfavourable karyotype. 相似文献
5.
6.
7.
We have compared the duration of motor block produced by four local anaesthetics administered into a chronically implanted subarachnoid catheter in rabbits. Each group (n = 6) received four different doses of amethocaine, bupivacaine, lignocaine or procaine, and the duration of the resulting motor block was assessed. Dose-response curves were plotted for each drug. As a measure of activity of the anaesthetics, we used the dose of each drug required to produce block of 60-min duration (D60 min) and the correlation between D60 min and different drug properties was examined. An inverse linear correlation (r = 0.995; P < 0.01) was observed between log D60 min and the log of the partition coefficient of the local anaesthetics. No correlation was found between the effect and degree of protein binding, pKa or molecular weight. These results suggest that, in spinal anaesthesia, the partition coefficient could be used as a predictor of the duration of anaesthetic action. 相似文献
8.
Bound-state beta decay of highly ionized atoms 总被引:1,自引:0,他引:1
9.
Free and bound non-sulphonated aromatic amines (NSAA) are determined in the food colours tartrazine, sunset yellow FCF and allura red. After reduction of the bound amines with sodium dithionite, the NSAA are extracted into chloroform, then transferred to aqueous acid solution, diazotized with sodium nitrite and coupled with 2-naphthol-3,6-disulphonic acid, disodium salt (R-salt). Reversed-phase ion-pair liquid chromatography and an absorbance detector at 512 nm are used to analyse the coloured derivatives. Samples of dyes were spiked with known amounts of aniline, 1-naphthylamine, 2- and 4-aminobiphenyl, 4-aminoazobenzene, benzidine, p-cresidine or 4-nitro-p-cresidine bound to R-salt. Recoveries averaged 90% in tartrazine, 65% in sunset yellow FCF and 71% in allura red. Detection limits ranged between 2 and 32 ng/g. A survey of 24 commercial samples revealed levels up to 520 micrograms/g total NSAA. The majority of NSAA are bound to the coupling compound during the manufacturing process and less than 7% remain as free amines in the dye. 相似文献
10.
Lawrence K. Forbes Graeme C. Hocking Simon Wotherspoon 《Journal of Engineering Mathematics》2004,48(1):69-91
Rainwater can collect in a lens-shaped region within the rock of a tropical island, and may be separated from the underlying salt water by a sharp interface. This paper presents a nonlinear theory for determining the shape of this interface. The island is assumed to be saturated with rain, and provision is made for the outflow of rain-water through the sides of the island. The effect of a bore well on the shape of the interface is investigated, and the problem is solved using a spectral method. An integral-equation method is also presented for the case when the island has infinite width. 相似文献