全文获取类型
收费全文 | 14045篇 |
免费 | 316篇 |
国内免费 | 36篇 |
专业分类
电工技术 | 203篇 |
综合类 | 17篇 |
化学工业 | 2108篇 |
金属工艺 | 281篇 |
机械仪表 | 338篇 |
建筑科学 | 518篇 |
矿业工程 | 24篇 |
能源动力 | 264篇 |
轻工业 | 1717篇 |
水利工程 | 111篇 |
石油天然气 | 32篇 |
无线电 | 1455篇 |
一般工业技术 | 1984篇 |
冶金工业 | 3468篇 |
原子能技术 | 177篇 |
自动化技术 | 1700篇 |
出版年
2023年 | 50篇 |
2022年 | 114篇 |
2021年 | 208篇 |
2020年 | 129篇 |
2019年 | 187篇 |
2018年 | 233篇 |
2017年 | 214篇 |
2016年 | 254篇 |
2015年 | 152篇 |
2014年 | 292篇 |
2013年 | 649篇 |
2012年 | 477篇 |
2011年 | 607篇 |
2010年 | 485篇 |
2009年 | 479篇 |
2008年 | 543篇 |
2007年 | 541篇 |
2006年 | 438篇 |
2005年 | 434篇 |
2004年 | 342篇 |
2003年 | 345篇 |
2002年 | 307篇 |
2001年 | 311篇 |
2000年 | 306篇 |
1999年 | 352篇 |
1998年 | 1084篇 |
1997年 | 686篇 |
1996年 | 507篇 |
1995年 | 375篇 |
1994年 | 307篇 |
1993年 | 324篇 |
1992年 | 170篇 |
1991年 | 156篇 |
1990年 | 157篇 |
1989年 | 158篇 |
1988年 | 154篇 |
1987年 | 116篇 |
1986年 | 125篇 |
1985年 | 178篇 |
1984年 | 118篇 |
1983年 | 108篇 |
1982年 | 81篇 |
1981年 | 111篇 |
1980年 | 101篇 |
1979年 | 97篇 |
1978年 | 52篇 |
1977年 | 130篇 |
1976年 | 182篇 |
1975年 | 57篇 |
1973年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
The levels of bacterial blood endotoxin, antiendotoxin antibodies and the overall immunity were studied in 48 females with inflammatory genital diseases complicated by pelvioperitonitis. The severest pelvioperitonitis-complicated abnormality was shown to characterized by high concentrations of endotoxin and low levels of antibodies. Endotoxinemia was found to be of diagnostic and prognostic value. 相似文献
82.
Hanssen M.; Krabbendam L.; Vollema M.; Delespaul P.; Van Os J. 《Canadian Metallurgical Quarterly》2006,115(1):5
It is unknown to what degree dimensions of schizotypy (subclinical psychosis) show independent, family-specific variation in the general population. Psychologists administered the Community Assessment of Psychic Experiences, the Structured Interview for Schizotypy-Revised (SIS-R), and the Brief Psychiatric Rating Scale to 257 subjects pertaining to 82 general population families. All 3 instruments showed family-specific variation for positive and negative subclinical psychosis dimensions with between-families proportions of total variance between 10% and 40%. However, only the SIS-R showed family-specific variation of the negative dimension independent of its correlation with the positive dimension. The positive dimension of subclinical psychosis shows familial-specific variation in samples unselected for psychiatric disorder, suggesting dimensional liability in the population. The SIS-R additionally captures family-specific variation in the negative domain. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
83.
The fabric and faces of threat, and the expediency and efficiency in the communication of threat, are examined with a threat appraisal model. This model is empirically tested on an ongoing communication challenge, the issuance of terror alerts by the United States' Department of Homeland Security (DHS), focusing on how threat is appraised by both the conservative and liberal audiences. Findings showed a shared view by the DHS and conservative audiences on the levels and nature of threats; liberal audiences thought otherwise. Though there appeared to be a consensus between the conservative and liberal audiences on the efficacy of threat communication, more internal consistency within DHS is needed to optimise its effectiveness. 相似文献
84.
Verbrugge Sara; Dieussaert Kristien; Schaeken Walter; Van Belle William 《Canadian Metallurgical Quarterly》2004,58(2):106
Evidence from reasoning tasks shows that promises and threats both tend to receive biconditional interpretations. They also both display high speaker control. On the face of it, the only difference seems to be the positive or negative signing of the consequent. In a promise, the speaker tries to persuade the hearer to do something by holding out the prospect of a particular reward; in a threat, the speaker tries to refrain the hearer from doing something by holding out the prospect of a particular punishment. This paper investigates the respects in which conditional promises and threats differ further by means of an inference task. The credibility of the consequent was manipulated in order to examine whether the acceptability ratings of inferences based on promises and on threats would be equally affected. The results of the inference task and an analysis of the reasons people give for their answers suggest that the credibility of promises is less affected by the use of excessive consequents than the credibility of threats. In other words, promise remains debt, whereas threat is another matter. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
Insulin-like growth factor I activates the invasion suppressor function of E-cadherin in MCF-7 human mammary carcinoma cells in vitro 总被引:1,自引:0,他引:1
ME Bracke BM Vyncke EA Bruyneel SJ Vermeulen GK De Bruyne NA Van Larebeke K Vleminckx FM Van Roy MM Mareel 《Canadian Metallurgical Quarterly》1993,68(2):282-289
The calcium-dependent cell-cell adhesion molecule E-cadherin has been shown to counteract invasion of epithelial neoplastic cells. Using three monoclonal antibodies, we have demonstrated the presence of E-cadherin at the surface of human MCF-7/6 mammary carcinoma cells by indirect immunofluorescence coupled to flow cytometry and by immunocytochemistry. Nevertheless, MCF-7/6 cells failed to aggregate in a medium containing 1.25 mM CaCl2, and they were invasive after confrontation with embryonic chick heart fragments in organ culture. Treatment of MCF-7/6 cells with 0.5 microgram ml-1 insulin-like growth factor I (IGF-I) led to homotypic aggregation within 5 to 10 min and inhibited invasion in vitro during at least 8 days. The effect of IGF-I on cellular aggregation was insensitive to cycloheximide. However, monoclonal antibodies that interfered with the function of either the IGF-I receptor (alpha IR3) or E-cadherin (HECD-1, MB2) blocked the effect of IGF-I on aggregation. The effects of IGF-I on aggregation and on invasion could be mimicked by 1 microgram ml-1 insulin, but not by 0.5 microgram ml-1 IGF-II. The insulin effects were presumably not mediated by the IGF-I receptor, since they could not be blocked by an antibody against this receptor (alpha IR3). Our results indicate that IGF-I activates the invasion suppressor role of E-cadherin in MCF-7/6 cells. 相似文献
86.
A Cuschieri S Shimi S Banting G Van Velpen P Dunkley 《Canadian Metallurgical Quarterly》1993,1(5-6):303-305
New coaxial curved and bayonet instruments have been designed which permit controlled dissection and directional change of the functional tip, blunt dissection and lift retraction. The instruments are introduced into the peritoneal and thoracic cavities through flexible re-usable metal cannulae. The excellent ergonomic properties of the new instruments have been confirmed by their use in major laparoscopic and thoracoscopic operations. Coaxial instruments enhance the scope of minimal access surgery and have distinct advantages over the traditional straight instruments. 相似文献
87.
G. M. Vyletel J. E. Allison D. C. Van Aken 《Metallurgical and Materials Transactions A》1995,26(12):3143-3154
The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and overaged 2219/TiC/15p and unreinforced
2219 Al were investigated using plastic strain-controlled and stress-controlled testing. In addition, the influence of grain
size on the particle-reinforced materials was examined. In both reinforced and unreinforced materials, the naturally aged
conditions were cyclically unstable, exhibiting an initial hardening behavior followed by an extended region of cyclic stability
and ultimately a softening region. The overaged reinforced material was cyclically stable for the plastic strains examined,
while the overaged unreinforced material exhibited cyclic hardening at plastic strains greater than 2.5 × 10−4. Decreasing grain size of particle-reinforced materials modestly increased the cyclic flow stress of both naturally aged
and overaged materials. Reinforced and unreinforced materials exhibited similar fatigue life behaviors; however, the reinforced
and unreinforced naturally aged materials had superior fatigue lives in comparison to the overaged materials. Grain size had
no effect on the fatigue life behavior of the particle-reinforced materials. The fatigue lives were strongly influenced by
the presence of clusters of TiC particles and exogenous Al3Ti intermetallics.
formerly Research Assistant with the Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI
48109
This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the
1994 TMS/ASM Spring meeting, held February 28–March 3, 1994 in San Francisco, California, under the auspices of the Joint
TMS-SMD/ASM-MSD Composite Materials Committee. 相似文献
88.
89.
J. Van Audenhove J. Pauwels A.J. Fudge 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,236(3):600-603
Recognizing the importance of an assured supply of reference materials of high purity for use as neutron dosimeters, the Monitor Materials subgroup of the European Working Group on Reactor Dosimetry collaborated with the Central Bureau for Nuclear Measurements, Geel, Belgium to establish a list of requirements.CBNM is organizing the availability and characterization of these materials in collaboration with specialist laboratories within the European Community. At present 12 activation and 6 fission dosimetry materials are being examined prior to certification and issue.This source of materials is expected to be of great use for reactor surveillance, interlaboratory comparisons, and other neutron metrology requirements. 相似文献
90.