全文获取类型
收费全文 | 7171篇 |
免费 | 29篇 |
专业分类
电工技术 | 11篇 |
综合类 | 1篇 |
化学工业 | 197篇 |
金属工艺 | 26篇 |
机械仪表 | 11篇 |
建筑科学 | 25篇 |
能源动力 | 26篇 |
轻工业 | 77篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 102篇 |
一般工业技术 | 153篇 |
冶金工业 | 6476篇 |
原子能技术 | 3篇 |
自动化技术 | 88篇 |
出版年
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 14篇 |
2019年 | 13篇 |
2018年 | 20篇 |
2017年 | 8篇 |
2016年 | 20篇 |
2015年 | 16篇 |
2014年 | 14篇 |
2013年 | 42篇 |
2012年 | 24篇 |
2011年 | 23篇 |
2010年 | 24篇 |
2009年 | 30篇 |
2008年 | 35篇 |
2007年 | 26篇 |
2006年 | 25篇 |
2005年 | 25篇 |
2004年 | 24篇 |
2003年 | 38篇 |
2002年 | 17篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 228篇 |
1998年 | 2053篇 |
1997年 | 1125篇 |
1996年 | 816篇 |
1995年 | 432篇 |
1994年 | 366篇 |
1993年 | 382篇 |
1992年 | 51篇 |
1991年 | 95篇 |
1990年 | 57篇 |
1989年 | 79篇 |
1988年 | 72篇 |
1987年 | 72篇 |
1986年 | 70篇 |
1985年 | 53篇 |
1984年 | 6篇 |
1983年 | 15篇 |
1982年 | 31篇 |
1981年 | 45篇 |
1980年 | 74篇 |
1979年 | 11篇 |
1978年 | 19篇 |
1977年 | 145篇 |
1976年 | 332篇 |
1975年 | 16篇 |
1974年 | 8篇 |
1971年 | 8篇 |
排序方式: 共有7200条查询结果,搜索用时 10 毫秒
1.
Jasmin Kuhn Philipp M. Klein Nader Al Danaf Joel Z. Nordin Sren Reinhard Dominik M. Loy Miriam Hhn Samir El Andaloussi Don C. Lamb Ernst Wagner Yoshitsugu Aoki Taavi Lehto Ulrich Lchelt 《Advanced functional materials》2019,29(48)
Phosphorodiamidate morpholino oligomers (PMOs) are oligonucleotide analogs that can be used for therapeutic modulation of pre‐mRNA splicing. Similar to other classes of nucleic acid‐based therapeutics, PMOs require delivery systems for efficient transport to the intracellular target sites. Here, artificial peptides based on the oligo(ethylenamino) acid succinyl‐tetraethylenpentamine (Stp), hydrophobic modifications, and an azide group are presented, which are used for strain‐promoted azide‐alkyne cycloaddition conjugation with splice‐switching PMOs. By systematically varying the lead structure and formulation, it is determined that the type of contained fatty acid and supramolecular assembly have a critical impact on the delivery efficacy. A compound containing linolenic acid with three cis double bonds exhibits the highest splice‐switching activity and significantly increases functional protein expression in pLuc/705 reporter cells in vitro and after local administration in vivo. Structural and mechanistic studies reveal that the lipopeptide PMO conjugates form nanoparticles, which accelerate cellular uptake and that the content of unsaturated fatty acids enhances endosomal escape. In an in vitro Duchenne muscular dystrophy exon skipping model using H2K‐mdx52 dystrophic skeletal myotubes, the highly potent PMO conjugates mediate significant splice‐switching at very low nanomolar concentrations. The presented aminoethylene‐lipopeptides are thus a promising platform for the generation of PMO‐therapeutics with a favorable activity/toxicity profile. 相似文献
2.
Varani L. Reggiani L. Kuhn T. Gonzalez T. Pardo D. 《Electron Devices, IEEE Transactions on》1994,41(11):1916-1925
We present a microscopic interpretation of electronic noise in semiconductor materials and two-terminal devices. The theory is based on Monte Carlo simulations of the carrier motion self-consistently coupled with a Poisson solver. Current and voltage noise operations are applied and their respective representations discussed. As application we consider the cases of homogeneous materials, resistors, n+nn + structures, and Schottky-barrier diodes. Phenomena associated with coupling between fluctuations in carrier velocity and self-consistent electric field are quantitatively investigated for the first time. At increasing applied fields hot-carrier effects are found to be of relevant importance in all the cases considered here. As a general result, noise spectroscopy is found to be a source of valuable information to investigate and characterize transport properties of semiconductor materials and devices 相似文献
3.
Parametric DC measurements on pseudomorphic AlGaAs/InGaAs modulation-doped field-effect transistors (MODFETs) were carried out over the 300-405 K temperature range. A gradual channel device model was developed to simulate the temperature dependent behavior and assist in the interpretation of the characteristics. The simulations are shown to provide good predictive ability and confirm the physical reasons why the zero temperature coefficient point of a MODFET occurs only for gate bias voltages below the threshold voltage 相似文献
4.
5.
6.
MG McInnis A Chakravarti J Blaschak MB Petersen V Sharma D Avramopoulos JL Blouin U K?nig C Brahe TC Matise 《Canadian Metallurgical Quarterly》1993,16(3):562-571
A genetic linkage map of human chromosome 21q (HC21q) containing 43 markers genotyped by the polymerase chain reaction in the CEPH pedigrees is presented. The markers placed on this map are highly polymorphic with an average heterozygosity of 61%. The average interval size of the markers localized at 1000:1 odds is 2.5 cM. The map has a total length of 65.5 cM, with male and female lengths of 47.7 and 83.3 cM, respectively. The genotypes used in the construction of this map were subjected to rigorous error checking, which is reflected in the shorter map length compared to previous maps; the estimated error rate in genotyping is less than 0.04%. As noted in previous linkage maps there is increased recombination in females on proximal HC 21q and in the male in a region near the telomere. This map of HC 21 represents a highly informative and dense meiotic linkage map and will be useful in linking disease phenotypes to loci on this chromosome. 相似文献
7.
8.
9.
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
10.
C Fernández Pinilla M Luque Otero N Martell Claros JM Alcázar de la Osa JL Rodicio Díaz LM Ruilope Urioste 《Canadian Metallurgical Quarterly》1993,101(5):168-171
BACKGROUND: Hypertension and hypercholesterolemia are frequently associated with this leading to considerable cardiovascular risk. METHODS: An open parallel randomized study was performed in which the effects of doxazosin, an alpha-adrenergic blocker and enalapril, an inhibitor of the angiotensin converting enzyme were compared in 70 patients with essential high blood pressure and plasma cholesterol levels greater than 240 mg/dl. Following 2-4 weeks of placebo administration the patients were randomly treated with one of the two drugs. When required doses were increased and hydrochlorothiazide added until blood pressure lower than 160/95 mmHg was achieved. After this period the patients were observed for a minimum of 8 weeks. The mean length of the study was of 22 weeks. RESULTS: Both drugs significantly reduced blood pressure without modifying cardiac frequency. Doxazosin tended to favorably modify the lipid profile of the plasma while enalapril significantly reduced the levels of cholesterol, lipids and high density lipoproteins (HDL). Upon termination of the study the total HDL/cholesterol index increased 8.6% in those treated with doxazosin and decreased 5.5% in those receiving enalapril (p < 0.05). CONCLUSIONS: Although doxazosin and enalapril are potent antihypertensive drugs, the effects on plasma lipid obtained with doxazosin indicate that a reduction in cardiovascular risk was achieved with this drug in the patients included in this study. 相似文献