全文获取类型
收费全文 | 2852篇 |
免费 | 22篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 27篇 |
综合类 | 2篇 |
化学工业 | 381篇 |
金属工艺 | 49篇 |
机械仪表 | 48篇 |
建筑科学 | 114篇 |
矿业工程 | 15篇 |
能源动力 | 58篇 |
轻工业 | 247篇 |
水利工程 | 33篇 |
石油天然气 | 22篇 |
无线电 | 175篇 |
一般工业技术 | 338篇 |
冶金工业 | 913篇 |
原子能技术 | 13篇 |
自动化技术 | 446篇 |
出版年
2022年 | 20篇 |
2021年 | 16篇 |
2019年 | 16篇 |
2017年 | 17篇 |
2016年 | 26篇 |
2015年 | 16篇 |
2014年 | 32篇 |
2013年 | 127篇 |
2012年 | 61篇 |
2011年 | 91篇 |
2010年 | 70篇 |
2009年 | 77篇 |
2008年 | 100篇 |
2007年 | 99篇 |
2006年 | 107篇 |
2005年 | 94篇 |
2004年 | 95篇 |
2003年 | 75篇 |
2002年 | 79篇 |
2001年 | 65篇 |
2000年 | 50篇 |
1999年 | 56篇 |
1998年 | 113篇 |
1997年 | 105篇 |
1996年 | 92篇 |
1995年 | 70篇 |
1994年 | 59篇 |
1993年 | 92篇 |
1992年 | 70篇 |
1991年 | 42篇 |
1990年 | 49篇 |
1989年 | 67篇 |
1988年 | 51篇 |
1987年 | 63篇 |
1986年 | 41篇 |
1985年 | 44篇 |
1984年 | 61篇 |
1983年 | 47篇 |
1982年 | 29篇 |
1981年 | 27篇 |
1980年 | 32篇 |
1979年 | 31篇 |
1978年 | 34篇 |
1977年 | 35篇 |
1976年 | 36篇 |
1975年 | 29篇 |
1974年 | 32篇 |
1973年 | 22篇 |
1971年 | 19篇 |
1970年 | 13篇 |
排序方式: 共有2881条查询结果,搜索用时 15 毫秒
1.
Larry Gillard 《电子产品世界》2003,(14):31-32
从电力与精确数字、模拟信号,到高压气态和液态介质,如今的用户定制电缆几乎无所不传。线缆制造商们现在可以提供的连接线缆材料可谓五花八门,从多种规格的传统铜线和光纤,到各类软管和导管,甚至包括碳纤维等半导体材料。在对一种专用电缆的设计作出最终决定前,要做一点“外形匹配”的工作。通常要回答的问题包括:“要传输些什么?”、“有什么限制条件?”、“完成任务应该采用何种连接物”。在进行优化的阶段,还要另外考虑使用环境,包括可能存在的电磁干扰、机械应力影响(如扭曲和/或摩擦)、化学和/或高温的损伤。细绞合铜导线在进行大功率… 相似文献
2.
Barch Deanna M.; Mitropoulou Vivian; Harvey Philip D.; New Antonia S.; Silverman Jeremy M.; Siever Larry J. 《Canadian Metallurgical Quarterly》2004,113(4):556
Research suggests that schizotypal personality disorder (SPD) is a part of the spectrum of schizophrenia-related illnesses. This article hypothesizes that a deficit in the representation and maintenance of context is a core cognitive disturbance in schizophrenia and that SPD individuals should demonstrate context-processing deficits. To test this hypothesis, the authors administered 3 versions of their AX-CPT task, designed to assess context processing, to 35 healthy controls and 26 individuals with DSM-IV SPD. They also administered working memory and selective attention tasks. SPD individuals displayed context representation deficits similar to those found in schizophrenia but did not show the same additional deficits in context maintenance. Context processing was strongly associated with working memory and selective attention performance in the SPD individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
S Moss B Ibbotson H Prosser D Goldberg P Patel N Simpson 《Canadian Metallurgical Quarterly》1997,32(6):344-354
The Psychiatric Assessment Schedule for Adults with Developmental Disability (PAS-ADD) is a semi-structured interview for use with respondents who have learning disability and for key informants. This report investigates the ability of the instrument to detect symptoms that had been found to exist during routine clinical assessment of the patients. Field trials involved 95 referred patients with learning disability and a key informant for each sample member. Clinical opinions of the referring psychiatrists were sought using a symptom checklist. Referrer checklist symptoms and PAS-ADD data were both factor analysed. Validity testing involved (a) computation of correlations between PAS-ADD factors and checklist data and (b) comparison of PAS-ADD and referrers' diagnoses. Results indicated good validity for the PAS-ADD in relation to psychotic symptoms and depressive symptoms. Anxiety symptom identification was not well validated, probably due to small numbers. Expansive mood identified by the referrers was not detected by the PAS-ADD because there is currently no corresponding section in the interview. Where the PAS-ADD produced a diagnosis (in 58 members of the sample), 44 were in agreement with the referrer. Probability of diagnosis by PAS-ADD increased with the number of relevant active symptoms identified by the referrer. The PAS-ADD has been shown in a previous report to have the sensitivity to detect mental disorders not known to psychiatric services. For psychotic and depressive conditions, our results showed that symptom detection was in good agreement with the information provided by the referring psychiatrists on their patients. The PAS-ADD needs a section on hypomania and further investigation of its detection of anxiety disorders. 相似文献
4.
Ipratropium bromide is a synthetic derivative of atropine with little absorption when used in inhalation, and therefore little secondary effects. The authors review its pharmacological properties and therapeutic efficacy in the treatment of asthma in children. Combined nebulized inhalation of ipratropium bromide and beta 2 sympathomimetic results in a more efficient and more sustained bronchodilatation than beta 2 sympathicomimetic alone in the treatment of acute asthma in children. Ipratropium bromide should be usefully introduced in the therapeutic scheme of acute asthma in children. Further studies will be necessary in order to determine its efficacy and tolerance in infants. 相似文献
5.
6.
Moss C.D. Teixeira F.L. Yang Y.E. Jin Au Kong 《Geoscience and Remote Sensing, IEEE Transactions on》2002,40(1):178-186
A three-dimensional (3D) finite-difference time-domain (FDTD) scheme is introduced to model the scattering from objects in continuous random media. FDTD techniques have been previously applied to scattering from random rough surfaces and randomly placed objects in a homogeneous background, but little has been done to simulate continuous random media with embedded objects where volumetric scattering effects are important. In this work, Monte Carlo analysis is used in conjunction with FDTD to study the scattering from perfectly electrically conducting (PEC) objects embedded in continuous random media. The random medium models under consideration are chosen to be inhomogeneous soils with a spatially fluctuating random permittivities and prescribed correlation functions. The ability of frequency averaging techniques to discriminate objects in this scenarion is also briefly investigated. The simulation scheme described in this work can be adapted and used to help in interpreting the scattered field data from targets in random environments such as geophysical media, biological media, or atmospheric turbulence 相似文献
7.
A quantum chemical study of the binding of Li+ cation to polyalkyloxides has been carried out. The lithium cation interaction with three polyalkyloxides (polyethylene oxide (PEO), polytrimethylene oxide (PTMO), and polypropylene oxide (PPO)) has been investigated using ab initio molecular orbital theory at the HF/6-31G* level with molecular models for the polymers. Coordination by one to six oxygens was considered. In addition, higher level calculations were carried out using G3(MP2) theory for coordination of Li+ by one oxygen. For coordination of lithium by one oxygen, the binding energy ordering is PTMO>PPO>PEO, with PTMO having the largest lithium cation affinity. The same ordering is found for larger coordination numbers with the exception of coordination by six oxygens, where the ordering changes due to the steric interactions. 相似文献
8.
Larry Bennett 《Journal of Urban Affairs》1987,9(3):263-276
ABSTRACT: In 1983 Chicago elected its first black mayor, Harold Washington. During Washington's first term of office, his administration not only reordered municipal priorities in such a fashion as to benefit his core, minority voting constituency, but also defined a municipal agenda emphasizing greater attention to neighborhood needs and more open government. In 1984 an important neighborhood coalition, the Save Our Neighborhoods/Save Our City Coalition (SON/SOC), proposed a linked development policy to tap downtown investment for neighborhood projects. Although SON/SOC's proposal was compatible with the Washington neighborhood agenda, this mainly white organization and the Washington administration experienced considerable difficulty in forging a mutually acceptable proposal The linked development debate in Chicago demonstrates the salience of race, class-cultural factors, and alternative approaches to neighborhood mobilization as barriers to the development of progressive coalitions in city politics. 相似文献
9.
Shokooh-Saremi M. Ta'eed V.G. Littler I.C.M. Moss D.J. Eggleton B.J. Ruan Y. Luther-Davies B. 《Electronics letters》2005,41(13):738-739
The first ultra-strong, near-perfect, raised-apodised Bragg gratings in As/sub 2/S/sub 3/ chalcogenide rib waveguides using /spl lambda/=532 nm light and a modified Sagnac holographic writing setup are demonstrated. Good agreement is achieved between the experimental results and the numerical modelling of the gratings using the transfer matrix analysis for thin film structures. 相似文献
10.
The increasing complecity of many expert system application areas calls for the integration of the knowledge of multiple experts. The use of multiple experts introduces some interesting new problems during the process of knowledge acquisition. The problems are further complicated when the experts are geographically dispersed or unavailable for face-to-face interactions.
This article discusses the motivations for acquiring the knowledge of multiple experts, the problems related to knowledge acquisition, new issues that arise whens multiple experts interact, solutions that can be brought to bear in building multiple expert systems (particularly when experts are geographically dispersed), and new tools for knowledge engineers to use when dealing with multiple experts. 相似文献