全文获取类型
收费全文 | 1307篇 |
免费 | 33篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 71篇 |
金属工艺 | 13篇 |
机械仪表 | 9篇 |
建筑科学 | 9篇 |
能源动力 | 6篇 |
轻工业 | 31篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 24篇 |
一般工业技术 | 109篇 |
冶金工业 | 1015篇 |
原子能技术 | 1篇 |
自动化技术 | 40篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 10篇 |
2017年 | 18篇 |
2016年 | 10篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 18篇 |
2012年 | 21篇 |
2011年 | 20篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 10篇 |
2003年 | 17篇 |
2002年 | 14篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 28篇 |
1998年 | 273篇 |
1997年 | 189篇 |
1996年 | 115篇 |
1995年 | 66篇 |
1994年 | 55篇 |
1993年 | 75篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 44篇 |
1976年 | 79篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有1340条查询结果,搜索用时 0 毫秒
1.
2.
Nanocrystalline TiO2 photosensitized with natural polymers with enhanced efficiency from 400 to 600 nm 总被引:1,自引:0,他引:1
Rodolfo Espinosa Inti Zumeta Jorge L. Santana Francisco Martínez-Luzardo Bernardo Gonzlez Sergilus Docteur Elena Vigil 《Solar Energy Materials & Solar Cells》2005,85(3):359-369
TiO2 sensitization for solar applications requires not only efficient but also stable and inexpensive sensitizers. Different condensed tannins extracted from bark wastes of tropical wood trees were studied as possible sensitizers of TiO2. These natural polymers adhere strongly to the TiO2 even from aqueous solutions. Absorption spectra are presented for 1 mM aqueous sensitizing solutions prepared with lyophilized condensed tannins which absorb light in the visible range. Spectral photocurrent measurements and I–V characterization show that no bias is required for electron injection to the TiO2 from all studied condensed tannins. Incident photon to current efficiency (IPCE) analysis indicates that surface complexation originates absorption bands with different electron injection efficiencies. These play a dominant role in determining IPCE spectral shape. We propose that surface modification by the sensitizer changes the surface trap density, thereby decreasing recombination losses. 相似文献
3.
Here we are presenting the case of a 70-years-old woman who has hepatic cirrhosis anti-HCV and insulin-dependent diabetes mellitus, without relevant epidemiologic ascendants or previous transfusions and HBV, HIV negatives. On admission to our hospital she showed signs of autoimmune hemolytic anaemia (AHA) which was confirmed by positive direct Coombs test and an improvement in blood test after corticoid treatment. Having discarded other possible causes such as drugs infectious diseases or essential mixed cryoglobulinemia (CME), we put forward the possible association between AHA and infection by HCV, where AHA was an extrahepatic immunological manifestation of HCV. This fact has never been brought to light in previous medical literature. 相似文献
4.
A Voskova-Goldman A Peier CT Caskey CS Richards LG Shaffer 《Canadian Metallurgical Quarterly》1997,48(6):1633-1638
The challenge of Duchenne muscular dystrophy (DMD) carrier identification resides in the ability to identify the presence of a mutant gene over the background contributed by the normal allele. Current diagnosis of carrier status when a deletion has been identified in a proband is based on an analysis of a gene dosage. We present a diagnostic strategy that uses fluorescence in situ hybridization (FISH) to detect female carriers with major deletions in the dystrophin gene. We screened a human X-chromosome-derived genomic library with a full-length dystrophin cDNA and isolated 15 dystrophin-specific cosmids that contain DMD gene exons. Six cosmids were further tested as FISH probes in control individuals and subsequently applied on chromosomes from eight males with DMD and known deletions and on samples from three female carriers. As expected, X chromosomes in normal females displayed four signals, two for the DMD-specific probe and two for the X-chromosome centromeric probe. Hybridization on chromosomal spreads from carriers of deletions revealed only one signal from the DMD-specific probe and two from the control centromeric probe. Males carrying deletions showed no DMD-specific signal for the deleted exons tested. Our data indicate that FISH could represent an alternative method for the detection of female carriers with DMD gene deletions. 相似文献
5.
LG Westergaard PE Rasmussen S Maigaard HJ Ingerslev AN Andersen JF Larsen J Starup PJ Hornnes CY Andersen 《Canadian Metallurgical Quarterly》1993,155(33):2511-2514
Medical indications for in vitro fertilization and embryo transfer (IVF-ET) internationally and in Denmark are reviewed. Reports from large international centres document that tubal infertility, unexplained infertility, endometriosis and male infertility are equally good indications for IVF. Traditionally, tubal infertility has been the only medical indication qualifying for IVF treatment within the National Health Service in Denmark. Thus, in this country, couples with unexplained and male infertility and with endometriosis have to pay up to 25,000 D.Kr. per IVF-ET treatment in private fertility clinics. Since there is no scientific basis for this discrimination, it is urged that the present rules are changed, so that couples with unexplained and male infertility and endometriosis are also allowed IVF treatment free of charge in the public fertility clinics. 相似文献
6.
We propose a new, less costly, design to test the equivalence of digital versus analogue mammography in terms of sensitivity and specificity. Because breast cancer is a rare event among asymptomatic women, the sample size for testing equivalence of sensitivity is larger than that for testing equivalence of specificity. Hence calculations of sample size are based on sensitivity. With the proposed design it is possible to achieve the same power as a completely paired design by increasing the number of less costly analogue mammograms and not giving the more expensive digital mammograms to some randomly selected subjects who are negative on the analogue mammogram. The key idea is that subjects who are negative on the analogue mammogram are unlikely to have cancer and hence contribute less information for estimating sensitivity than subjects who are positive on the analogue mammogram. To ascertain disease state among subjects not biopsied, we propose another analogue mammogram at a later time determined by a natural history model. The design differs from a double sampling design because it compares two imperfect tests instead of combining information from a perfect and imperfect test. 相似文献
7.
8.
9.
10.