全文获取类型
收费全文 | 2561篇 |
免费 | 11篇 |
专业分类
电工技术 | 20篇 |
综合类 | 1篇 |
化学工业 | 74篇 |
金属工艺 | 5篇 |
机械仪表 | 9篇 |
建筑科学 | 18篇 |
矿业工程 | 1篇 |
能源动力 | 29篇 |
轻工业 | 52篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 78篇 |
一般工业技术 | 134篇 |
冶金工业 | 2050篇 |
原子能技术 | 22篇 |
自动化技术 | 72篇 |
出版年
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 13篇 |
2015年 | 4篇 |
2014年 | 13篇 |
2013年 | 35篇 |
2012年 | 15篇 |
2011年 | 21篇 |
2010年 | 19篇 |
2009年 | 33篇 |
2008年 | 34篇 |
2007年 | 16篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 21篇 |
2003年 | 25篇 |
2002年 | 24篇 |
2001年 | 29篇 |
2000年 | 15篇 |
1999年 | 69篇 |
1998年 | 663篇 |
1997年 | 353篇 |
1996年 | 236篇 |
1995年 | 146篇 |
1994年 | 92篇 |
1993年 | 121篇 |
1992年 | 27篇 |
1991年 | 28篇 |
1990年 | 34篇 |
1989年 | 33篇 |
1988年 | 21篇 |
1987年 | 21篇 |
1986年 | 25篇 |
1985年 | 41篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 22篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1978年 | 8篇 |
1977年 | 59篇 |
1976年 | 99篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有2572条查询结果,搜索用时 15 毫秒
11.
SL Tannheimer SL Barton SP Ethier SW Burchiel 《Canadian Metallurgical Quarterly》1997,18(6):1177-1182
A method was developed to determine in eggs 2 components [4,6-dimethyl-2-hydroxypyrimidine and 1,3-bis(4-nitrophenyl)urea] of the anticoccidial drug nicarbazin, used to treat poultry. Samples were extracted with acetonitrile, and the extracts were washed with hexane and evaporated to dryness before analysis by liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization. By switching from positive to negative ion monitoring and using gradient elution, both components were measured within one run. The limit of quantitation of the assay was 10 ng/g for each component. The results of a preliminary feeding trial in which chickens were fed contamination levels of the drug are also reported. 相似文献
12.
13.
14.
FM Loehrer CP Angst FP Brunner WE Haefeli B Fowler 《Canadian Metallurgical Quarterly》1998,13(3):656-661
BACKGROUND: Elevated homocysteine concentrations have been associated with premature arteriosclerosis and with impairment of key methylation reactions through accumulation of the homocysteine metabolite S-adenosylhomocysteine. In end-stage renal failure high homocysteine concentrations are commonly found but thus far the concentrations of related adenosylated metabolites in plasma have not been assessed. METHODS: In this prospective study we determined plasma homocysteine and related metabolites in 25 patients on regular haemodialysis, and in 40 healthy volunteers. Blood samples from patients were drawn immediately before and in 10 patients additionally after the dialysis session. RESULTS: Folic acid and vitamin B12 in plasma were similar in patients (mean +/- SEM 25+/-2 nmol/l and 400+/-41 pmol/l respectively) and controls (24+/-3 and 324+/-23 respectively). In patients plasma homocysteine, S-adenosylmethionine and S-adenosylhomocysteine were markedly elevated (36.6+/-3.6 micromol/l, 381+/-32nmol/l and 1074+/-55 nmol/l respectively) compared to the control values (6.8+/-0.4 micromol/l, 60+/-3 nmol/l and 24.4+/-1.1 nmol/l respectively) whereas the molar ratio of plasma S-adenosylmethionine and S-adenosylhomocysteine was significantly decreased (0.36+/-0.02 and 2.7+/-0.2 in patients and controls respectively). Haemodialysis failed to normalize the abnormal levels of these metabolites. CONCLUSION: Since the ratio of S-adenosylmethionine : S-adenosylhomocysteine is closely linked to the activity of numerous enzymatic methylation reactions, these results suggest that methylation may be impaired in these patients. 相似文献
15.
16.
17.
18.
In search for cancer chemoprevention agents, seven new amide compounds have been synthesized. The structures have been determined based on spectral and chemical data. N-4-(ethoxycarbophenyl)-alpha-naphthamide and N-4-(ethoxycarbophenyl)-beta-naphthamide were shown to be 81% and 79% effective, respectively, for inducing different in HL-60 human promyelocytic leukemia cells at the concentration of 10(-5) mol/L in NBT tests. 相似文献
19.
Antisera towards neurotensin (NT) and the structurally related peptide, LANT6, were used to characterize immunoreactive peptides and proteins in extracts of chicken tissues. A 17 kDa protein was identified by Western blotting as a potential precursor to NT and LANT6. However, the posttranslational processing of this common precursor appeared to be tissue specific, giving rise to disproportionate amounts of NT and LANT6, along with varying expression of a large molecular LANT6 (M(r), 15 kDa). The intestinal cells containing immunoreactive NT, LANT6, and large molecular LANT6 behaved similarly during fractionation by size and density. These activities also banded together in particles resembling vesicles during centrifugation of isotonic homogenates of tissue. These results suggest that chicken NT and LANT6 are biosynthesized as parts of the same precursor, the processing of which can give rise to a variety of products stored within secretory vesicles. 相似文献
20.
Haemangiopericytoma of nose and paranasal sinuses is relatively uncommon tumour. It occurs in adults in sixth and seventh decades of life. In view of paucity of intranasal haemangiopericytoma old in Indian literature and young age of patient, we are reporting one case in 28-year-old female who presented with recurrent, profuse epistaxis. 相似文献