全文获取类型
收费全文 | 2093篇 |
免费 | 24篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 92篇 |
金属工艺 | 9篇 |
机械仪表 | 5篇 |
建筑科学 | 14篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 58篇 |
水利工程 | 14篇 |
无线电 | 70篇 |
一般工业技术 | 110篇 |
冶金工业 | 1634篇 |
原子能技术 | 14篇 |
自动化技术 | 79篇 |
出版年
2023年 | 5篇 |
2022年 | 14篇 |
2021年 | 16篇 |
2020年 | 28篇 |
2019年 | 23篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 10篇 |
2014年 | 15篇 |
2013年 | 24篇 |
2012年 | 15篇 |
2011年 | 38篇 |
2010年 | 19篇 |
2009年 | 18篇 |
2008年 | 20篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 19篇 |
2004年 | 12篇 |
2003年 | 17篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 16篇 |
1999年 | 35篇 |
1998年 | 473篇 |
1997年 | 280篇 |
1996年 | 189篇 |
1995年 | 147篇 |
1994年 | 96篇 |
1993年 | 92篇 |
1992年 | 28篇 |
1991年 | 25篇 |
1990年 | 17篇 |
1989年 | 11篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 62篇 |
1976年 | 111篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 3篇 |
排序方式: 共有2117条查询结果,搜索用时 0 毫秒
71.
AV Krylov YN Antonenko EA Kotova TI Rokitskaya AA Yaroslavov 《Canadian Metallurgical Quarterly》1998,440(1-2):235-238
Effect of a cationic polymer, poly(L-lysine), on the kinetic properties of ionic channels formed by neutral gramicidin A (gA) and its negatively charged analogue O-pyromellitylgramicidin (OPg) in a bilayer lipid membrane is studied using a method of sensitized photoinactivation. This newly developed method is based on the analysis of transmembrane current transients induced by a flash in the presence of a photosensitizer. It has been shown previously that the time course of the flash-induced current decrease in most cases follows a single exponential decay with an exponential factor (tau, the characteristic time of photoinactivation) that correlates well with the single-channel lifetime. Addition of polylysine does not affect tau for gA channels, but causes a substantial increase in tau for OPg channels. This effect is reversed by addition of polyacrylic acid. The deceleration of the photoinactivation kinetics is ascribed to electrostatic interaction of polylysine with OPg probably resulting in OPg clustering. The latter can stabilize the channel state by reducing the rotational and lateral mobility of OPg monomers and dimers, and thus increase the single channel lifetime. 相似文献
72.
A van der Lugt EJ Gussenhoven G Pasterkamp T Stijnen JA Reekers FG van den Berg AV Tielbeek JL Seelen H Pieterman 《Canadian Metallurgical Quarterly》1998,16(2):110-119
The skepticism surrounding the potential benefits of resistance exercise training prevalent just decades ago has evolved over the years to an understanding of the integral nature muscular overload plays in the training programs for athletes. The science of training elite athletes is progressing rapidly, as insights into the physiological adaptations resulting from varying program configurations become available. Resistance training impacts several body systems, including muscular, endocrine, skeletal, metabolic, immune, neural, and respiratory. An understanding and appreciation of basic scientific principles related to resistance training is necessary in order to optimize training responses. Careful selection of the acute program variables in a workout to simulate sports-specific movements is required for optimal transfer of gains made in training to competition. Thus, whether athletes require predominantly eccentric, isometric, slow-velocity, or high-velocity strength or power in their athletic event will dictate the time commitment to each component and form the basis for designing individual workouts. Program variation over a training period is essential to maximize gains and prevent overtraining. 相似文献
73.
The aim of this study was to assess the referral pattern and the impact on long-term survival of postoperative radiotherapy in patients with adenocarcinoma of the endometrium stage I. This was a retrospective study performed in a regional cancer registry which covers a population of approximately 1,000,000 persons. All 724 patients registered between 1975 and 1992 in the Comprehensive Cancer Centre South, Eastern Section, The Netherlands, were analysed. All patients had received surgery as primary treatment which was performed in one of the seven community hospitals of the region. Radiotherapy was given in one regional department. All pathology reports were checked for data on tumour differentiation and myometrial invasion. Almost half the patients (45%) were referred for postoperative radiotherapy. The depth of myometrial invasion and the degree of tumour differentiation were the main factors (P < 0.0001) influencing referral for postoperative radiotherapy. The referral pattern varied between the different hospitals, but became more similar during 1985-1988, to diverge again in recent years. In patients younger than 60 years, the depth of myometrial invasion was significantly (P = 0.01) correlated with survival. In patients older than 60 years, tumour differentiation (P = 0.05) and age (P < 0.001) were correlated with survival, but not the depth of myometrial invasion. After adjustment for known prognostic factors, a survival benefit of postoperative radiotherapy could not be established. The studied group had an excess death rate over the normal Dutch female population. This excess death rate did not decrease during follow-up, as even after 10 years an excess death rate was found. A prospective randomised trial is ongoing in The Netherlands. 相似文献
74.
75.
TM Gerhardt GE Schmahl C Flotho AV Rath CM Niemeyer 《Canadian Metallurgical Quarterly》1997,99(4):882-887
Activation of the Evi-1 gene was first described to be associated with the transformation of murine myeloid leukaemias and has previously been detected in cases of human acute myeloid leukaemia (AML) and chronic myeloid leukaemia (CML) in blast crises and in myelodysplastic syndromes. In this study we determined the frequency and the level of Evi-1 expression in juvenile myelomonocytic leukaemia (JMML) and in normal haemopoiesis. Using RT-PCR and Southern blot hybridization mRNA of Evi-1 could be detected in bone marrow (BM) and peripheral blood (PB) mononuclear cells (MNC) of normal donors. In JMML 12/20 patients examined expressed elevated levels of Evi-1 compared to normal controls. In these samples over-expression of the gene was correlated with a higher percentage of blasts (P = 0.02). Expression levels in BFU-E and CFU-GM derived colonies from BM of JMML patients were lower than those in the corresponding MNC samples. Analysis of CD34+ and CD34- cells demonstrated that Evi-1 is primarily expressed in the CD34+ cell population of both JMML and normal donors. These findings suggest that Evi-1 expression is linked to the early stages of haemopoiesis. Studies on the regulation of Evi-1 expression in CD34+ cells will elucidate its function in progenitor cells and clarify its possible role in the pathogenesis of JMML. 相似文献
76.
77.
NN Belosel''ski? OB Ershova IuN Pribytkov AV Bessarab 《Canadian Metallurgical Quarterly》1997,69(5):55-58
To specify shape of the vertebra in relation to age and sex, the authors studied roentgenomorphometric evidence upon examination of the thoracic and lumbar spine in 600 patients over 50. Vertebral deformities were found in 45.1 and 44.5% of the examined males and females, respectively. Changes corresponding to vertebral body fracture were recorded in 12.3% of the males and 15.3% of the females. Age-related trends in the frequency of various defects have been analyzed. The frequency differed in males and females. 相似文献
78.
A two-dimensional photoetched glass flow cell was used to observe the process by which an emulsion was broken down by a granular porous coalescer. The effects of wettability, emulsion and collector zeta potentials, and emulsion droplet size on the coalescence phenomenon were studied. The possible use of a graded medium or a coalescer with mixed wettability to enhnce the coalescence process was also examined. Based on these visual studies, a set of guidelines was developed to aid in the selection of a porous coalescer for a given separation duty. 相似文献
79.
80.
Jonathan P. Moses Kent A. Harries Christopher J. Earls Wahyu Yulismana 《Canadian Metallurgical Quarterly》2006,11(4):401-409
Glass fiber-reinforced polymer (GFRP) bridge deck systems offer an attractive alternative to concrete decks, particularly for bridge rehabilitation projects. Current design practice treats GFRP deck systems in a manner similar to concrete decks, but the results of this study indicate that this approach may lead to nonconservative bridge girder designs. Results from a number of in situ load tests of three steel girder bridges having the same GFRP deck system are used to determine the degree of composite action that may be developed and the transverse distribution of wheel loads that may be assumed for such structures. Results from this work indicate that appropriately conservative design values may be found by assuming no composite action between a GFRP deck and steel girder and using the lever rule to determine transverse load distribution. Additionally, when used to replace an existing concrete deck, the lighter GFRP deck will likely result in lower total stresses in the supporting girders, although, due to the decreased effective width and increased distribution factors, the live-load-induced stress range is likely to be increased. Thus, existing fatigue-prone details may become a concern and require additional attention in design. 相似文献