全文获取类型
收费全文 | 1212篇 |
免费 | 18篇 |
专业分类
电工技术 | 16篇 |
化学工业 | 95篇 |
金属工艺 | 11篇 |
机械仪表 | 19篇 |
建筑科学 | 13篇 |
能源动力 | 8篇 |
轻工业 | 57篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 104篇 |
一般工业技术 | 159篇 |
冶金工业 | 645篇 |
原子能技术 | 5篇 |
自动化技术 | 96篇 |
出版年
2022年 | 9篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2014年 | 15篇 |
2013年 | 29篇 |
2012年 | 14篇 |
2011年 | 30篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 22篇 |
2007年 | 21篇 |
2006年 | 30篇 |
2005年 | 24篇 |
2004年 | 21篇 |
2003年 | 21篇 |
2002年 | 26篇 |
2001年 | 30篇 |
2000年 | 13篇 |
1999年 | 28篇 |
1998年 | 208篇 |
1997年 | 96篇 |
1996年 | 73篇 |
1995年 | 63篇 |
1994年 | 34篇 |
1993年 | 27篇 |
1992年 | 14篇 |
1991年 | 8篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1987年 | 24篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1978年 | 8篇 |
1977年 | 22篇 |
1976年 | 41篇 |
1975年 | 8篇 |
1973年 | 7篇 |
1971年 | 7篇 |
1966年 | 4篇 |
1965年 | 4篇 |
1960年 | 4篇 |
排序方式: 共有1230条查询结果,搜索用时 15 毫秒
1.
Dopamine receptors influence vasoactive intestinal peptide release from turkey hypothalamic explants
Amongst the elements which contributed to the success of the early lung transplants at the beginning of the 1980's we feel that the careful selection of candidates probably played a predominant role. If some of the selection criteria initially described remain somewhat intangible, others have either been eased or have been invalidated. The experience acquired over the last 15 years has enabled to precise the optimal moment to include patients on the waiting list and to refine the choice for the type of surgical procedure according to the underlying disease. This article aims to review the different selection criteria for candidates for transplantation and stresses those which have recently undergone change. 相似文献
2.
3.
The interactions of the antihistaminic drug chlorpheniramine maleate (CPM) with the negatively charged polyelectrolytes poly(sodium 4-styrenesulfonate) (PSS) and poly(acrylic acid) (PAA) are studied by the washing method of the diafiltration technique at conditions simulating those of the small intestine such as pH 7.5 and 0.13 M NaCl. The results are compared with those already reported involving other pharmacologically important polyelectrolytes such as alginic acid (ALG), carboxymethylcellulose (CMC), and κ- and ι-carrageenan (κ- and ι-CAR). As in the case of ALG, CMC, and CAR, interactions of CPM with PAA appear to be electrostatic and are cleaved in the presence of 0.13 M NaCl. On the contrary, apart from electrostatic interactions, additional interactions are found with PSS and residual interactions are kept in the presence of 0.13 M NaCl, a fact that may be attributed to π-π interactions and hydrophobic forces. The effect of the addition of 4 M urea, branched poly(ethyleneimine) (BPEI), and poly(vinylpyrrolidone) (PVP) is also studied. The addition of urea 4 M or 0.001 M BPEI produces a decrease on the amounts of counterions bound to PSS at infinite elution, while the addition of PVP does not produce any change on the diafiltration profiles. 相似文献
4.
OM Elashry G Giusti RB Nadler EM McDougall RV Clayman 《Canadian Metallurgical Quarterly》1997,158(2):363-369
The choline-containing phosphoglycolipid, MfGL-II, is the major polar lipid of Mycoplasma fermentans PG18. Anti-MfGL-II antisera raised in rabbits using the purified MfGL-II as an immunogen were employed in immunogold electron microscopic and immunofluorescence studies showing that MfGL-II is uniformly distributed and exposed on the cell surface of M. fermentans cells. The specificity of the antibodies was determined by immunostaining of lipid extracts separated by thin layer chromatography. The antibodies recognize lipids specific to M. fermentans but did not cross-react with lipid extracts of M. penetrans, M. capricolum, M. gallisepticum or Acholeplasma laidlawii. As phosphocholine almost completely abolished antibody interaction with MfGL-II in an ELISA assay it is suggested that the anti-MfGL-II repertoire is composed primarily of anti-phosphocholine antibodies. The anti-MfGL-II antisera inhibit the attachment of M. fermentans to Molt-3 lymphocytes suggesting that MfGL-II plays a major role in M. fermentans-host cell interaction. 相似文献
5.
This study examines the links between antecedents and consequences of Gabonese teachers' (N= 152) work motivation. The theoretical underpinnings are based on the Motivational Model of Job Burnout (MMJB) which is grounded in Self-Determination Theory (SDT) and states that the more supervisors satisfy an employee's need for self-determination, competence, and relatedness, the more self-determined is the latter's work motivation. The level of self-determined motivation has an impact on job satisfaction, which in turn determines life satisfaction. Higher levels of self-determined motivation also buffer emotional exhaustion and psychological distress. The model was confirmed via structural equation modeling and provides support for the validity and generalizability of the MMJB and SDT. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
In this paper, we summarize our recent efforts to analyze transmission probabilities of extremely thin SiO2 gate oxides using microscopic models of Si[100]-SiO2-Si[100] heterojunctions. We predict energy-dependent tunneling masses and their influence on transmission coefficients, discuss tunneling probabilities and analyze effects arising from the violation of parallel momentum conservation. As an application of the present method, gate currents in short bulk MOSFETs are calculated, including elastic defect-assisted contributions. 相似文献
7.
Many-Body Terms in van der Waals Cohesion Energy of Nanotubes 总被引:2,自引:0,他引:2
We have developed a model for the calculation of van der Waals force for layered systems with axial symmetry. Our result can be applied to compute the cohesion of a carbon nanotube to a substrate, the cohesion between nanotubes, and between shells of multiwall nanotubes. We have obtained unusal power laws for the distance dependence of the many-body van der Waals potential. 相似文献
8.
OM Takayanagui AA Castro e Silva RC Santiago NS Odashima VC Terra AM Takayanagui 《Canadian Metallurgical Quarterly》1996,54(4):557-564
Cysticercosis is a severe public health problem in several regions of Asia, Africa and Latin America. Epidemiologic studies based on the frequency of cases observed in specialized neurology, neurosurgery and computed tomography services, at autopsy and in seroepidemiologic studies do not permit the determination of the true prevalence of the disease in the population. The objective of the present study was to investigate the prevalence of cysticercosis by compulsory notification. The coefficient of prevalence was 54 cases/100,000 inhabitants in the municipality of Ribeir?o Preto. The results also indicated that cysticercosis is not under control in our region since 21% of cases presented the active form of the disease. Compulsory notification proved to be a valuable resource for the epidemiologic study of cysticercosis, also permitting the mapping of more affected areas for a better direction of prevention strategies. 相似文献
9.
10.
Many industrial processes and scientific experiments utilize large amounts of ac power at frequencies from 3 kHz to 500 kHz. The phase angle and the impedances of these loads often vary over a wide range. This paper describes an instrument to provide an accurate measurement of currents (1 A to 1000 A), voltages (100 V to 20 kV), and powers (100 W to 20 MW) over the frequency range from 25 kHz to 500 kHz. It deals with loads having power factors down to nearly zero and with load impedances from 10 Ω to 20 kΩ. The paper contains practical details of both the design and the calibration of the front-end voltage and current transducers. The characteristics of a nearly ideal broadband current transducer are presented. Overall instrument calibration, verification and traceability problems are considered in detail 相似文献