全文获取类型
收费全文 | 1693篇 |
免费 | 34篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 55篇 |
综合类 | 1篇 |
化学工业 | 385篇 |
金属工艺 | 44篇 |
机械仪表 | 25篇 |
建筑科学 | 55篇 |
矿业工程 | 11篇 |
能源动力 | 31篇 |
轻工业 | 197篇 |
水利工程 | 19篇 |
石油天然气 | 3篇 |
无线电 | 100篇 |
一般工业技术 | 278篇 |
冶金工业 | 335篇 |
原子能技术 | 11篇 |
自动化技术 | 178篇 |
出版年
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 18篇 |
2017年 | 15篇 |
2016年 | 18篇 |
2015年 | 25篇 |
2014年 | 20篇 |
2013年 | 75篇 |
2012年 | 43篇 |
2011年 | 67篇 |
2010年 | 39篇 |
2009年 | 47篇 |
2008年 | 67篇 |
2007年 | 36篇 |
2006年 | 32篇 |
2005年 | 33篇 |
2004年 | 33篇 |
2003年 | 40篇 |
2002年 | 29篇 |
2001年 | 42篇 |
2000年 | 40篇 |
1999年 | 25篇 |
1998年 | 87篇 |
1997年 | 68篇 |
1996年 | 45篇 |
1995年 | 39篇 |
1994年 | 41篇 |
1993年 | 26篇 |
1992年 | 29篇 |
1991年 | 17篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 20篇 |
1982年 | 20篇 |
1981年 | 18篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 19篇 |
1977年 | 35篇 |
1976年 | 40篇 |
1974年 | 24篇 |
1973年 | 19篇 |
1972年 | 17篇 |
1971年 | 14篇 |
1967年 | 14篇 |
排序方式: 共有1728条查询结果,搜索用时 15 毫秒
1.
A task-switching paradigm with a 2:1 mapping between cues and tasks was used to separate cue-switching processes (indexed through pure cue-switch costs) from actual task-switching processes (indexed through additional costs in case of cue and task changes). A large portion of total switch costs was due to cue changes (Experiments 1 and 2), and cue-switch costs but not task-switch costs were sensitive to effects of practice (Experiment 1) and preparation (Experiment 2). In contrast, task-switch costs were particularly sensitive to response-priming effects (Experiments 1 and 2) and task-set inhibition (Experiment 3). Results suggest two processing stages relevant during task-set selection: cue-driven retrieval of task rules from long-term memory and the automatic application of rules to a particular stimulus situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
Hydroelectric generators of less than 20 kilowatts can be in remote areas served only by a single-phase line. For high efficiency and low cost, a three-phase induction generator should be used. This three-phase generator can operate with balanced voltages and currents when the ``phase-splitting' circuit uses two capacitors connetted to two different single-phase voltage sources. 相似文献
3.
For pt.I. see ibid., vol.8, no.3, p.36-43 (1991). Contactless tools for testing inside dynamic RAMs, including hot-spot detection, emission microscopy, scanning laser microscopy, and submicron electron beam testing, are described. Basic principles and experimental setups are described. The utility of the techniques is assessed 相似文献
4.
JM Bach H Otto GT Nepom G Jung H Cohen J Timsit C Boitard PM van Endert 《Canadian Metallurgical Quarterly》1997,10(4):375-386
Tissue composition and the distribution of body mass are described for four genera of East African Bovidae (Madoqua, Gazella, Damaliscus, Hippotragus) with supporting data from four others (Neotragus, Oryx, Tragelaphus, Connochaetes). These species are high in muscle mass, an adaptation convergent with other high-speed terrestrial cursors, bounders, and saltators. The segments below the elbow/cubitus and knee/stifle/genu joints in small bovids are both lighter in percent of total body mass (8.6% TBM) and less heavily muscled (10-15% of total limb musculature) than those segments in macaques (13.6% TBM, 20-25% of the limb musculature). Bovid species differ from one another in the regional distribution of muscle mass. Madoqua kirkii (4-5 kg) concentrates muscle in the lumbar extensors and hindlimbs; large species such as Damaliscus doreas (50-60 kg) and Hippotragus niger (160-220 kg) distribute it more evenly between the lumbar and cervical regions and between the hindlimbs and forelimbs. Gazella dorcas (10-20 kg) is quantitatively intermediate in those characteristics. The redistribution of muscle mass with increasing size correlates with the loss of axial bending of the vertebral column: in small, hindlimb dominant, 'dorsomobile' species such as Madoqua sagittal mobility increases stride length through 'extended' suspension; in large 'dorsostable' species such as Damaliscus and Hippotragus the vertebral column resists bending, consequently abbreviating or omitting this non-contact phase of the gait cycle. Locomotor adaptation as it is reflected in size, shape, and musculoskeletal structure is the key to habitat choice, dietary specialization, social structure, and male agonistic behavior and, therefore, central to the fabric of behavioral ecology. 相似文献
5.
The p53 tumor suppressor gene encodes a phosphoprotein which when overexpressed can induce growth arrest at the G1 and G2/M phases of the cell cycle, promote differentiation and apoptosis. This paper demonstrates that p53 can associate with trk tyrosine kinase. Expression of a murine temperature-sensitive (ts) p53 mutant in PC12 cells overexpressing trk (a model system to analyse cellular differentiation and signal transduction induced by NGF) induces morphological changes in the absence of NGF stimulation at 32 degrees C but not at 37 degrees C. In cells differentiated by p53, trk, but not EGFr, was hyperphosphorylated on tyrosine. Furthermore trk was not phosphorylated when expressed in Saos-2 cells (human osteosarcoma cells that lack expression of both endogenous trk and p53) at either temperature. However, transfection of ts p53 into these cells induces trk phosphorylation at 32 degrees C in the absence of NGF stimulation. Association of trk and p53 can be detected in NIH3T3 and PC12 cells co-expressing trk and the ts p53 mutant, in NIH3T3 and PC12 cells transfected with trk alone, and in untransfected PC12 cells, showing that overexpressed and/or endogenous trk associates with endogenous, low levels of p53. These data suggest a novel function for p53 which involves the stimulation of signal transduction pathways (mediating morphological properties of cells), possibly through association with and hyperphosphorylation of trk. 相似文献
6.
S Schumacher H Volkmer F Buck A Otto A Tarnók S Roth FG Rathjen 《Canadian Metallurgical Quarterly》1997,136(4):895-906
Chicken acidic leucine-rich EGF-like domain containing brain protein (CALEB) was identified by combining binding assays with immunological screens in the chicken nervous system as a novel member of the EGF family of differentiation factors. cDNA cloning indicates that CALEB is a multidomain protein that consists of an NH2-terminal glycosylation region, a leucine-proline-rich segment, an acidic box, a single EGF-like domain, a transmembrane, and a short cytoplasmic stretch. In the developing nervous system, CALEB is associated with glial and neuronal surfaces. CALEB is composed of a 140/130-kD doublet, an 80-kD band, and a chondroitinsulfate-containing 200-kD component. The latter two components are expressed in the embryonic nervous system and are downregulated in the adult nervous system. CALEB binds to the extracellular matrix glycoproteins tenascin-C and -R. In vitro antibody perturbation experiments reveal a participation of CALEB in neurite formation in a permissive environment. 相似文献
7.
8.
C Sergi K Jundt S Seipp T Goeser L Theilmann G Otto HF Otto WJ Hofmann 《Canadian Metallurgical Quarterly》1998,29(6):861-871
BACKGROUND/AIMS: The aim of the study was to assess the impact factor of HCV and HGV in fulminant hepatic failure. METHODS: The 5'-untranslated regions of HCV RNA and HGV RNA and a segment of the core antigen sequence of HBV were amplified after extracting the nucleic acids from snap-frozen tissue aliquots from explanted livers of 26 consecutive patients undergoing orthotopic liver transplantation for fulminant hepatic failure preoperatively diagnosed as either autoimmune (n=2), HAV/HBV (n=8), toxic (n=4) or aetiologically unknown (n=12). RESULTS: HCV RNA was detected in five of 26 (19.2%) livers with fulminant hepatic failure. All five HCV RNA-positive livers belonged to the group of non-toxic, non-autoimmune liver failure (n=20), three of them were found in the group of liver failure with unknown aetiology (n=12) and two in the group of HBV-associated liver failure (n=7), making an HCV incidence of 25%, 25% and 28.6%, in the different groups, respectively. HGV RNA was detected in 10 of 17 (58.8%) explants and in all four groups of fulminant hepatic failure as defined preoperatively. HBV DNA was identified in six livers of 26 patients (23.1%) with fulminant hepatic failure. Neither HCV RNA nor HBV DNA was detected in the livers of patients with toxic or autoimmune fulminant hepatic failure. CONCLUSIONS: These results indicate that HBV and HCV, but not HGV, play an aetiologic role in fulminant hepatic failure. HCV-positive cases were concentrated either in the group of otherwise unexplained fulminant hepatic failure or in the group of HBV fulminant hepatic failure. HGV-positive cases, on the other hand, were found within all four preoperatively defined groups, indicating a role as cofactor rather than as single aetiologic agent. 相似文献
9.
10.
Reviews the book, Forms of feeling: The heart of psychotherapy by Robert F. Hobson. Robert Hobson calls this book his autobiography as a therapist. As such it provides interesting glimpses into some of his more meaningful sessions with clients, illuminating his approach to therapy and enabling the reader to see a master therapist at work. Hobson also presents a new method of therapy, which he calls the conversational model. On this level, his book is considerably less satisfying. Hobson succinctly outlines the general principles of the conversational model and basic skills required of the therapist, but in so doing offers essentially little new information, however valid the points may be. According to Hobson, the conversational model is designed for clients whose problems arise from disturbances in their significant relationships, and those problems are best solved not by talking about them but by being in a relationship such as therapy that provides "a special kind of friendship." Hobson puts great stress on the use of metaphorical language in therapy and learning how to use the language of art as well as of science. He relies heavily on literary quotations, prefacing each section with one or two, and liberally interspersing many more within the pages of text. The net result is not so much illuminating as it is wearisome, and the general tone is slightly pretentious and, when Hobson addresses his "dear Reader" directly, somewhat condescending. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献