全文获取类型
收费全文 | 5859篇 |
免费 | 268篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 33篇 |
综合类 | 1篇 |
化学工业 | 957篇 |
金属工艺 | 65篇 |
机械仪表 | 66篇 |
建筑科学 | 271篇 |
矿业工程 | 11篇 |
能源动力 | 121篇 |
轻工业 | 642篇 |
水利工程 | 58篇 |
石油天然气 | 18篇 |
无线电 | 354篇 |
一般工业技术 | 966篇 |
冶金工业 | 1957篇 |
原子能技术 | 14篇 |
自动化技术 | 596篇 |
出版年
2023年 | 32篇 |
2022年 | 70篇 |
2021年 | 109篇 |
2020年 | 72篇 |
2019年 | 77篇 |
2018年 | 102篇 |
2017年 | 110篇 |
2016年 | 103篇 |
2015年 | 116篇 |
2014年 | 137篇 |
2013年 | 319篇 |
2012年 | 238篇 |
2011年 | 410篇 |
2010年 | 311篇 |
2009年 | 272篇 |
2008年 | 335篇 |
2007年 | 316篇 |
2006年 | 271篇 |
2005年 | 242篇 |
2004年 | 198篇 |
2003年 | 180篇 |
2002年 | 161篇 |
2001年 | 130篇 |
2000年 | 117篇 |
1999年 | 115篇 |
1998年 | 254篇 |
1997年 | 177篇 |
1996年 | 124篇 |
1995年 | 114篇 |
1994年 | 102篇 |
1993年 | 91篇 |
1992年 | 56篇 |
1991年 | 29篇 |
1990年 | 38篇 |
1989年 | 40篇 |
1988年 | 33篇 |
1987年 | 34篇 |
1986年 | 33篇 |
1985年 | 36篇 |
1984年 | 31篇 |
1983年 | 24篇 |
1982年 | 27篇 |
1981年 | 30篇 |
1980年 | 21篇 |
1979年 | 26篇 |
1978年 | 26篇 |
1977年 | 39篇 |
1976年 | 61篇 |
1975年 | 21篇 |
1973年 | 19篇 |
排序方式: 共有6130条查询结果,搜索用时 31 毫秒
41.
42.
To investigate the benefits and perceived effectiveness of instructional technology, students enrolled in several courses were compared on student evaluations of instruction, grades and an attitudinal questionnaire. The instructors of the courses taught the same course across two successive semesters, using traditional “chalk-and-talk” methods the first semester, and PowerPoint the next; all other techniques (e.g., exams, lecture material) were held constant. Results suggest that organization and clarity, entertainment and interest, professor likeability, and good professor behaviors were enhanced with PowerPoint although final grades were not. 相似文献
43.
44.
Clementz Brett A.; McDowell Jennifer E.; Zisook Sidney 《Canadian Metallurgical Quarterly》1994,103(2):277
In Study 1, 30 schizophrenia Ss and 27 nonpsychiatric comparison Ss were presented with a fixation task, a visually guided reflexive saccade (prosaccade) task, a predictive tracking task (0.4-Hz square wave), and an antisaccade task. The 2 groups did not differ on either the fixation or prosaccade tasks. Schizophrenia Ss had an increased number of errors on the antisaccade task and had decreased rightward visually guided saccade amplitudes during the predictive tracking task. In Study 2, 13 psychiatric comparison Ss and 32 1st-degree biological relatives of the schizophrenia Ss were compared with the schizophrenia Ss and a larger and older sample of nonpsychiatric Ss (n?=?33) on the predictive tracking and antisaccade tasks. The groups did not differ on predictive saccadic tracking. The schizophrenia Ss and their 1st-degree biological relatives made more errors on the antisaccade task than both the nonpsychiatric and psychiatric comparison groups (who did not significantly differ). Results are consistent with the notion that dysfunction of dorsolateral prefrontal cortex, caudate nucleus, or both is related to liability for schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
Jones Enrico E.; Ghannam Jess; Nigg Joel T.; Dyer Jennifer F. 《Canadian Metallurgical Quarterly》1993,61(3):381
Articulates a paradigm for single-case research in psychotherapy. A patient diagnosed as having major depressive disorder was seen in an intensive, twice-weekly psychodynamic psychotherapy for 2.5 years. Each session was videotaped, and assessments of patient change were obtained at regular intervals. A time-series analysis was used to model fluctuations in the therapy process to take into account time and the effect of previous events on subsequent changes, thereby preserving the context-determined meaning for therapist and patient actions. A bidirectional analysis of causal effects shows that the influence processes between therapist and patient are mutual and reciprocal and suggests that the effect of the patient on the therapist and on the process has not been made sufficiently explicit in previous models of process and change. The potential of intensive single-case designs for uncovering causal effects in psychotherapy is demonstrated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
Hopkins William D.; Bennett Allyson J.; Bales Stacy L.; Lee Jennifer; Ward Jeannette P. 《Canadian Metallurgical Quarterly》1993,107(4):403
Behavioral laterality was studied in a captive group of 11 bonobos (Pan paniscus). In an observational method a significant left lateral bias in carrying and a right lateral bias in leading limb were found. Direction of lateral bias in carrying and leading limb was enhanced when Ss maintained a bipedal posture. Analysis of bimanual feeding behavior revealed a significant right-hand bias for eating when the Ss were holding food with their left hand. In an experimental method a significant shift toward greater right-hand use was found when Ss were required to maintain a bipedal, rather than a quadrupedal, posture. There was no evidence of lateral bias for measures of face touching, self-touching, or gestures. The results are discussed in the context of previous reports of primate laterality. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
Clonality in T-cell malignancy was investigated using T-cell receptor (TcR) V beta 1-20 family primers and polymerase chain reaction amplification (PCR) of cDNA prepared from tissue biopsies and blood involved with tumour. Secondary PCR amplification of the VDJ joints of primary PCR products was performed to distinguish clonal from polyclonal products, and clonal V beta gene products were confirmed by direct PCR sequencing in the majority of cases. In eight T-cell malignancies including T-cell acute lymphoblastic leukaemia (T-ALL) and T-cell chronic lymphocytic leukaemia (T-CLL) shown to be clonal by Southern blot analysis, one or two primary PCR products were identified and shown to be clonal. In five cases of peripheral T-cell lymphoma (PTCL) all V beta 1-20 families were identified after primary PCR amplification, and clonal products were identified in two cases after secondary amplification; TcR V beta clonal families could not be demonstrated in the remaining three cases. These data were in agreement with previous Southern blot analysis of these cases, and confirmed the presence of reactive T cells in PTCL as well as providing further evidence for the genotypic heterogeneity of this entity. In the remaining case, a blood lymphocytosis, primary PCR amplification produced predominant TcR V beta 6 and V beta 12 family products, of which the V beta 6 family proved clonal after secondary PCR amplification. There was no evidence for overrepresentation of TCR V beta families by the tumour populations in this study, furthermore the data confirm the involvement of reactive cells in T-cell malignancy and the genetic heterogeneity of PTCL. 相似文献
48.
Christian Jennifer L.; O'Leary K. Daniel; Vivian Dina 《Canadian Metallurgical Quarterly》1994,8(1):32
Marital discord and depressive symptomatology have repeatedly been found to be associated, but little is known about variables that influence this relationship. Data were collected from 139 couples seeking marital therapy, and analyses were conducted separately by gender. For wives, lower problem-solving ability, physical aggression by the partner, and 1 relationship belief predicted depressive symptomatology after the variance due to marital discord was removed in regression analyses. In addition to these predictors, less spouse-specific assertiveness, unemployment, and 1 other relationship belief were associated with depressive symptomatology for women after the variance due to marital discord was removed in partial correlation analyses. For men, only lower problem-solving ability added to the prediction of depressive symptomatology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
49.
50.
Multisite microprobes for neural recordings 总被引:1,自引:0,他引:1
Blum N.A. Carkhuff B.G. Charles H.K. Jr. Edwards R.L. Meyer R.A. 《IEEE transactions on bio-medical engineering》1991,38(1):68-74
Multisite, passive microprobes have been developed to allow simultaneous recording of action potential activity from multiple neurons at different locations in the brain. The microprobes were fabricated using standard integrated circuit techniques. The probe is a planar structure that consists of gold electrodes sandwiched between two polyimide dielectric layers and bonded to a molybdenum structural support. Windows in the top dielectric layer expose the electrode sites and bonding pads. In two distinct versions of the probe four or six recordings sites, respectively, of approximately 25 microns 2 are arranged on a dagger-shaped structure which can penetrate the pia. The bonding pads and interconnect wires at the probe head are entirely encapsulated in a tubular fixture that is packed with silicone RTV and sealed with epoxy to protect the interconnections from contact with body fluids. The site impedances at 1 kHz are typically between 2 and 4 M omega. Probe lifetimes for continuous immersion in physiological saline solution, as measured by impedance, have exceeded 750 h. The failure mechanism is believed to be due to moisture and ion absorption in the top dielectric layer. In acute neurophysiological experiments using the four site probes, action potential activity was recorded from physiologically identified neurons in the dorsal column nuclei of anesthetized rat. 相似文献