全文获取类型
收费全文 | 1807篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 84篇 |
综合类 | 1篇 |
化学工业 | 75篇 |
金属工艺 | 22篇 |
机械仪表 | 21篇 |
建筑科学 | 32篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 95篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 65篇 |
一般工业技术 | 98篇 |
冶金工业 | 1167篇 |
原子能技术 | 19篇 |
自动化技术 | 132篇 |
出版年
2021年 | 14篇 |
2019年 | 15篇 |
2018年 | 24篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 21篇 |
2013年 | 62篇 |
2012年 | 38篇 |
2011年 | 32篇 |
2010年 | 39篇 |
2009年 | 25篇 |
2008年 | 38篇 |
2007年 | 30篇 |
2006年 | 24篇 |
2005年 | 28篇 |
2004年 | 12篇 |
2003年 | 27篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 18篇 |
1999年 | 50篇 |
1998年 | 347篇 |
1997年 | 167篇 |
1996年 | 114篇 |
1995年 | 72篇 |
1994年 | 70篇 |
1993年 | 68篇 |
1992年 | 13篇 |
1991年 | 22篇 |
1990年 | 24篇 |
1989年 | 24篇 |
1988年 | 20篇 |
1987年 | 25篇 |
1986年 | 14篇 |
1985年 | 23篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 14篇 |
1977年 | 30篇 |
1976年 | 81篇 |
1975年 | 10篇 |
1973年 | 12篇 |
1972年 | 12篇 |
1971年 | 11篇 |
1970年 | 6篇 |
排序方式: 共有1826条查询结果,搜索用时 62 毫秒
1.
AH Lauber TJ Barrett M Subramaniam M Schuchard TC Spelsberg 《Canadian Metallurgical Quarterly》1997,272(39):24657-24665
The receptor-binding factor (RBF) for the avian oviduct progesterone (Pg) receptor (PR) has previously been shown to be a unique 10-kDa nuclear matrix protein that generates high affinity PR-binding sites on avian DNA. This paper describes the use of Southwestern blot and DNA gel shift analyses with RBF protein to identify a minimal 54-base pair RBF-binding element in the matrix-associated region (MAR) of the Pg-regulated c-myc gene promoter. This element contains a 5'-GC-rich domain and a 3'-AT-rich domain, the latter of which has a homopurine/homopyrimidine structure. The gel shift assays required the generation of an RBF-maltose fusion protein (RBF-MBP), which specifically binds this element and is supershifted when the anti-RBF polyclonal antibody is added. Computer analysis of the full-length amino acid sequence for RBF predicts a DNA-binding motif involving a beta-sheet structure at the N-terminal domain. Southern blot analyses using nuclear matrix DNA suggests that there are dual MAR sites in the c-myc promoter, which flank an intervening domain containing the RBF element. The co-transfection of this MAR sequence, containing the RBF element and cloned into a luciferase reporter vector, together with an RBF expression vector construct, into steroid treated human MCF-7 cells, results in a decrease of the c-myc promoter activity relative to control transfections containing only the parent vector of the RBF expression construct. These data suggest that a unique chromatin/nuclear matrix structure, composed of the RBF-DNA element complex which is flanked by nuclear matrix attachment sites, serves to bind the PR and repress the c-myc promoter. 相似文献
2.
Kosslyn Stephen M.; Koenig Olivier; Barrett Anna; Cave Carolyn Backer; Tang Joyce; Gabrieli John D. E. 《Canadian Metallurgical Quarterly》1989,15(4):723
Analyses of human object recognition abilities led to the hypothesis that 2 kinds of spatial relation representations are used in human vision. Evidence for the distinction between abstract categorical spatial relation representations and specific coordinate spatial relation representations was provided in 4 experiments. These results indicate that Ss make categorical judgments—on/off, left/right, and above/below—faster when stimuli are initially presented to the left cerebral hemisphere, whereas they make evaluations of distance—in relation to 2 mm, 3 mm, or 1 in. (2.54 cm)—faster when stimuli are initially presented to the right cerebral hemisphere. In addition, there was evidence that categorical representations developed with practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
4.
These experiments explored the role of prior experience in 12- to 18-month-old infants' tool-directed actions. In Experiment 1, infants' use of a familiar tool (spoon) to accomplish a novel task (turning on lights inside a box) was examined. Infants tended to grasp the spoon by its handle even when doing so made solving the task impossible (the bowl did not fit through the hole in the box, but the handle did) and even though the experimenter demonstrated a bowl-grasp. In contrast, infants used a novel tool flexibly and grasped both sides equally often. In Experiment 2, infants received training using the novel tool for a particular function; 3 groups of infants were trained to use the tool differently. Later, infants' performance was facilitated on tasks that required infants to grasp the part of the tool they were trained to grasp. The results suggest that (a) infants' prior experiences with tools are important to understanding subsequent tool use, and (b) rather than learning about tool function (e.g., hammering), infants learn about which part of the tool is meant to be held, at least early in their exposure to a novel tool. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
This report summarizes the panel held at the 109th Annual Convention, American Psychological Association, August 26, 2001, San Francisco. The chair was William Glover and the speakers were Samuel Gerson, Karen Maroda, and Andre Patsalides. The invited symposium was directed at discussing different perspectives related to the presence of desire in the analytic process. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
BD Shenstone A Mahmoud R Woodward D Elvins R Palmer EF Ring AK Bhalla 《Canadian Metallurgical Quarterly》1994,33(6):541-545
A prospective longitudinal study of patients with early RA was performed to examine the influence of disease duration, disease activity and physical activity on bone loss. Sixty-seven patients with non-steroid treated RA of less than 5 yr duration, including 16 patients with disease duration less than 6 months, had BMD measurements of the femoral neck and the lumbar spine over a 12-month period using dual energy X-ray absorptiometry. The BMD changes were compared with values from 72 control patients and were also correlated with serial measurements of disease activity (measured by the Stoke Index) and disability [measured by the Health Assessment Questionnaire (HAQ) score], at 3-monthly intervals over the 12-month period. No significant differences in BMD changes were found between RA patients and controls overall. Patients with disease duration of less than 6 months had significantly greater loss of BMD at the femoral neck (-3.9%, S.E.M. 1.5) than the remainder of the cohort (-0.2%, S.E.M. 0.7) (P = 0.02) and controls (-0.8%, S.E.M. 0.6). Lumbar spine BMD changes correlated with the initial Stoke Index (Rs-0.373, P = 0.01) but not mean Stoke Indices. There was no correlation of BMD changes with age or HAQ scores. These findings suggest that significant bone loss occurs within the first few months of disease in patients with RA. 相似文献
7.
Although there have been recent molecular biological studies for evidence of possible changes in trypanosome biochemistry, such studies are not yet complemented by parallel clinical studies to determine the possible implications to the sleeping sickness patient. The study of the duration of symptoms and the case fatality of T. b. rhodesiense showed that the disease progressed to the stage of central nervous system involvement between three weeks to two months of infection. Most (> 80%) deaths occurred within six months of illness. The case fatality rate of treated sleeping sickness patients was 6% of which the rate in the late-stage of sleeping sickness was more than two and a half times that in the early stage. The incidence of melarsoprol encephalopathy was 2.5% and case fatality due to this condition was 1.0% and similar to previous findings. Thus it appears the virulence of T. b. rhodesiense circulating in south east Uganda has not changed during the past decades. 相似文献
8.
Rotational and functional motor behavioral changes were studied in five MPTP lesioned chronic hemiparkinsonian Macaca nemestrina monkeys after i.m. pramipexole, a predominant D2 subfamily agonist. Pramipexole induced contraversive rotations in a dose-dependent manner with an optimal dose of 56 microg/kg for approximately 2 to 4 hr after injection. Three different rating scales were used to determine drug-induced functional improvement. They included a monkey parkinsonism rating scale, volitional responses to fruit presentations, and number of hand movements that appeared volitional. A dose of 56 microg/kg of pramipexole produced functional improvements on hand disability, and on a parkinsonian rating scale for monkeys in a dose-dependent manner from 32 to 100 microg/kg. These doses produced an increase in significant hand movements in the affected (contralateral) as well as in the normal (ipsilateral) hand to the side of the brain lesion compared with 5% dextrose in water vehicle control. With a dose of 100 microg/kg, the therapeutic effects of pramipexole on hand movements were less than with 56 microg/kg, due to side effects such as scratching. 相似文献
9.
EF Bernstein FJ Sullivan JB Mitchell GD Salomon E Glatstein 《Canadian Metallurgical Quarterly》1993,20(3):435-453
Radiation therapy exerts both acute and chronic effects on normal tissue included within treatment fields. The physics of radiation therapy and treatment techniques to minimize deleterious effects of radiation are presented. Management of radiation-damaged skin is discussed. Radiation effect on tissue, wound healing, and tumorigenesis also are reviewed. 相似文献
10.
Ann Barrett Anuradha Prakash Deborah Sakelakos Irwin Taub Samuel Cohen Yuki Ohashi 《Food Hydrocolloids》1998,12(4):401-408
The effects of composition and thermal treatment on the water sorption and diffusional properties of idealized protein gels arranged in bilayer configurations were determined; these water binding/migration properties were related to the mechanical characteristics of the gels. Samples were prepared from whey protein concentrate (WPC), they consisted of water:WPC ratios of 1.5 to 5.67, and were thermally set for 20–60 min. Moisture migration rates from samples interfaced with filters were determined, as were moisture sorption capacities of samples immersed in water. The physical properties of the gels were assessed by uniaxial compression and microscopy. Results showed that gel strength and consequent extent of protein interaction—as affected by thermal treatment—controlled the ability of the gel structure to absorb water. Sorption was exponentially correlated with gel modulus and linearly correlated with a function of protein content, heating time, and immersion time. Rates of diffusion from interfaced gels were dependent solely on water content. It was concluded that the degree of protein interaction, whether influenced by concentration or thermal treatment, affected network extensibility and thus the capacity of the gels to act as receptors of moisture. Results have implications for the functionality of shelf-stable sandwiches and other multicomponent foods. 相似文献