全文获取类型
收费全文 | 12006篇 |
免费 | 403篇 |
国内免费 | 79篇 |
专业分类
电工技术 | 278篇 |
综合类 | 258篇 |
化学工业 | 1681篇 |
金属工艺 | 428篇 |
机械仪表 | 389篇 |
建筑科学 | 359篇 |
矿业工程 | 99篇 |
能源动力 | 246篇 |
轻工业 | 1077篇 |
水利工程 | 135篇 |
石油天然气 | 89篇 |
武器工业 | 18篇 |
无线电 | 1254篇 |
一般工业技术 | 1538篇 |
冶金工业 | 3402篇 |
原子能技术 | 123篇 |
自动化技术 | 1114篇 |
出版年
2022年 | 99篇 |
2021年 | 162篇 |
2020年 | 156篇 |
2019年 | 129篇 |
2018年 | 139篇 |
2017年 | 171篇 |
2016年 | 166篇 |
2015年 | 150篇 |
2014年 | 219篇 |
2013年 | 505篇 |
2012年 | 331篇 |
2011年 | 393篇 |
2010年 | 337篇 |
2009年 | 358篇 |
2008年 | 378篇 |
2007年 | 362篇 |
2006年 | 377篇 |
2005年 | 297篇 |
2004年 | 272篇 |
2003年 | 270篇 |
2002年 | 275篇 |
2001年 | 223篇 |
2000年 | 233篇 |
1999年 | 259篇 |
1998年 | 871篇 |
1997年 | 554篇 |
1996年 | 488篇 |
1995年 | 347篇 |
1994年 | 310篇 |
1993年 | 347篇 |
1992年 | 180篇 |
1991年 | 165篇 |
1990年 | 161篇 |
1989年 | 159篇 |
1988年 | 162篇 |
1987年 | 158篇 |
1986年 | 145篇 |
1985年 | 154篇 |
1984年 | 115篇 |
1983年 | 111篇 |
1982年 | 89篇 |
1981年 | 99篇 |
1980年 | 78篇 |
1979年 | 89篇 |
1978年 | 75篇 |
1977年 | 123篇 |
1976年 | 211篇 |
1975年 | 81篇 |
1974年 | 76篇 |
1961年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
111.
Cntextual logic provides a mechanism to reason about modules.In this paper,this theory of modules if modules is extended to a context theory of classes where class is in the true spirit of object-oriented databases.The logic,referred to as CLOG,is class-based.CLOG supports class,object identity,multiple role of object, monotonic and non-monotonic inheritance of data and method,method factoring,views,derived and query classes.Views and derived classes are queries in themselves.Objects are pure data terms representing the ground instances of facts in the class.Object identity is a first class term in the logic.Inheritance is handled through delegation. 相似文献
112.
We report a very rare case of an avulsion of the pectoralis major tendon in association with a two-part proximal humerus fracture. Pectoralis major tendon avulsion was confirmed intraoperatively during open reduction and internal fixation of the humerus fracture. In retrospect, the preoperative radiographic finding of posterolateral and proximal displacement of the humeral shaft suggested an injury to the pectoralis major. Because others have reported that the best treatment of a pectoralis major tendon avulsion is surgical repair, we feel that it is important to suspect such an injury in a proximal humerus fracture when this anatomic displacement is present. 相似文献
113.
Johnson Robert; Hobfoll Stevan E.; Zalcberg-Linetzy Ana 《Canadian Metallurgical Quarterly》1993,6(3):266
Examined the relationships among social support knowledge, supportive behavior, intimacy with one's spouse, and satisfaction with support provided by one's spouse among 41 Israeli kibbutz couples. The hypothesis that support knowledge and support behavior influence the intimacy between couples and increase satisfaction with spouse's social support efforts was tested. Alternative causal mechanisms are explored with simultaneous equation modeling. Results indicate that satisfaction with social support behavior by one's spouse is mediated entirely by intimacy with one's spouse. Results also indicate that partner's knowledge about social support behavior directly affects intimacy and indirectly generates social support satisfaction independent of actual supportive behavior. The findings do not differ by sex. The consistency of the findings with family behavior exchange theory and implications for marital therapy are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
114.
We show for the first time that signal processing schemes based on noncoherent signal addition will require signal transfer characteristics exhibiting high degrees of curvature. We quantify this by proposing a set of single-input, dual-output, power-conserving transfer functions and generating designs based on these characteristics. We then analyze the sensitivity of such a design scheme to nonidealities in the signal level and device behavior, and show that a sampling operation is only possible for transfer characteristics with residual "low" output of less than about 10% and low intensity reflectivity higher than 98%. For single device signal loss of up to 0.1 dB, we show that the best possible crosstalk-to-noise ratio in a packet forwarder (27 dB), is limited by the availability of the sampling operation. 相似文献
115.
Mapping of the Saccharomyces cerevisiae CDC3, CDC25, and CDC42 genes to chromosome XII by chromosome blotting and tetrad analysis 总被引:9,自引:0,他引:9
D I Johnson C W Jacobs J R Pringle L C Robinson G F Carle M V Olson 《Yeast (Chichester, England)》1987,3(4):243-253
CDC3, CDC25 and CDC42 were localized to chromosome XII by hybridizing the cloned genes to Southern blots of chromosomes separated by orthogonal-field-alternation gel electrophoresis. Meiotic tetrad analyses further localized these genes to the region distal to the RDN1 locus on the right arm of the chromosome. The STE11 gene, which had previously been mapped to chromosome XII (Chaleff and Tatchell, 1985), was found to be tightly linked to ILV5. The data suggest a map order of CEN12-RDN1-CDC42-(CDC25-CDC3)-(ILV5- STE11)-URA4. Certain oddities of the data set raise the possibility that there may be constraints on the patterns of recombination in this region of chromosome XII. 相似文献
116.
Masahiro Baba Goh Itoh Haruhiko Okumura 《Journal of the Society for Information Display》2007,15(3):205-211
Abstract— In this paper, a software‐processed edge‐ and level‐adaptive overdrive (SELAO) method, which is a novel overdrive technique that utilizes not only a temporal change of gray levels but also a spatial edge intensity of motion pictures, is proposed. The SELAO method is a software video‐processing technology to improve motion‐picture quality rendered on LCDs more than is possible with a conventional SLAO method without edge‐adaptive overdrive, and it works in real time on commonly used personal computers (PCs). 相似文献
117.
Combined-Stage Sintering Model 总被引:8,自引:0,他引:8
James D. Hansen Richard P. Rusin Mao-Hua Teng D. Lynn Johnson 《Journal of the American Ceramic Society》1992,75(5):1129-1135
By focusing on the similarities between the three stages of sintering, a single equation is derived that quantifies sintering as a continuous process from beginning to end. The microstructure is characterized by two separate parameters representing geometry and scale. The dimensionless geometry parameter, denoted T, comprises five scaling factors that relate specific microstructural featuers (e.g., surface curvature) to the scale (grain diameter). Calculations of T from experimental data show (a) agreement with computer simulations of initial-stage sintering, (b) the effect of surface diffusion on T, and (c) changes in T with microstructural evolution during sintering. Application of the model to the design of firing schedules and the study of microstructural geometry effects on sintering is discussed. 相似文献
118.
Poly(tetrahydropyranyl-2-methacrylate) (PTHPMA) was found to be miscible with Poly(vinyl phenol) (PVPH), Poly(hydroxy ether of bisphenol A) (Phenoxy), and Poly(styrene-co-allyl alcohol) (PSAA). However, Poly(cyclohexyl methacrylate) (PCHMA) is immiscible with all these three hydroxyl-containing polymers. Poly(acetonyl methacrylate) (PACMA) was found to be miscible with PVPH but immiscible with Phenoxy and PSAA. Miscible PTHPMA-Phenoxy blends showed lower critical solution temperature behavior. 相似文献
119.
RS Wallis P Nsubuga C Whalen RD Mugerwa A Okwera D Oette JB Jackson JL Johnson JJ Ellner 《Canadian Metallurgical Quarterly》1996,174(4):727-733
Macrophage activation and tumor necrosis factor-alpha (TNF-alpha) production are critical in tuberculosis immunity but may result in increased human immunodeficiency virus (HIV) expression and accelerated HIV disease progression in HIV-infected persons. Pentoxifylline inhibits expression of TNF-alpha and HIV. A double-blind, placebo-controlled study of adjunctive therapy with pentoxifylline (1800 mg/day) as a timed-release formulation was done in Ugandan HIV-infected patients with pulmonary tuberculosis. Subjects had early HIV disease (mean CD4 cell count, 380/microL) and did not receive other antiretroviral drugs. Pentoxifylline resulted in decreased plasma HIV RNA and serum beta 2-microglobulin and, in a subset of moderately anemic patients, improved blood hemoglobin levels. Trends were noted toward reduced TNF-alpha production in vitro and improved performance scores, but these did not reach statistical significance. No effect was noted on body mass, CD4 cell count, or survival. Additional studies of more potent TNF-alpha inhibitors in HIV-positive subjects with tuberculosis are warranted. 相似文献
120.
Clostridium tertium bacteremia is unusual, seen most often with gastrointestinal disease and/or neutropenia. Two cases are described. The first was a 19-yr-old female with acute leukemia, who developed gastrointestinal symptoms and C. tertium bacteremia while neutropenic. The second was a 57-yr-old female with quiescent ulcerative colitis, who presented with fever, rigors and epigastric pain. Four organisms including C. tertium were isolated from blood cultures. This patient responded to broad spectrum antimicrobial therapy, whereas the first patient required the addition of specific agents to recover. C. tertium is aerotolerant and thus can be misidentified as a Bacillus or Corynebacterium spp. Our isolates had a distinctive Gram stain morphology, were catalase negative and failed to sporulate aerobically--this aided in the recognition of this significant Gram-positive bacillus. 相似文献