首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1484篇
  免费   12篇
  国内免费   2篇
电工技术   8篇
综合类   1篇
化学工业   247篇
金属工艺   15篇
机械仪表   21篇
建筑科学   71篇
矿业工程   10篇
能源动力   24篇
轻工业   181篇
水利工程   26篇
石油天然气   5篇
武器工业   1篇
无线电   129篇
一般工业技术   179篇
冶金工业   420篇
原子能技术   1篇
自动化技术   159篇
  2022年   9篇
  2021年   13篇
  2020年   11篇
  2019年   14篇
  2018年   23篇
  2017年   11篇
  2016年   9篇
  2015年   14篇
  2014年   18篇
  2013年   62篇
  2012年   39篇
  2011年   42篇
  2010年   36篇
  2009年   33篇
  2008年   58篇
  2007年   55篇
  2006年   34篇
  2005年   46篇
  2004年   36篇
  2003年   35篇
  2002年   34篇
  2001年   27篇
  2000年   21篇
  1999年   35篇
  1998年   84篇
  1997年   55篇
  1996年   50篇
  1995年   35篇
  1994年   28篇
  1993年   35篇
  1992年   20篇
  1991年   24篇
  1990年   28篇
  1989年   23篇
  1988年   33篇
  1987年   19篇
  1986年   19篇
  1985年   31篇
  1984年   24篇
  1983年   22篇
  1982年   20篇
  1981年   27篇
  1980年   15篇
  1979年   27篇
  1978年   21篇
  1977年   27篇
  1976年   26篇
  1975年   11篇
  1974年   13篇
  1973年   13篇
排序方式: 共有1498条查询结果,搜索用时 0 毫秒
101.
Reviews the book, Initiating and administering guidance services, by S. A. Hamrin (1953). Hamrin addressed this book to school principals and superintendents because "no worthwhile program of guidance services can thrive or even exist long without sympathetic understanding and encouragement of school administrators. It is hoped that this volume will aid in promoting such understanding and assistance." This book appears to be a combination of Hamrin's lectures illustrated by excerpts from term papers written by Hamrin's students. The reviewer was annoyed by the interspersion of the amateurish illustrations in the midst of Hamrin's expert and mature discussions of the various topics. Hamrin has demonstrated in his previous books that his own experience has been rich and sufficiently varied to provide pertinent illustrative material. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
102.
Describes a 15-session group treatment program for couples in a health maintenance organization (HMO). The program demonstrates principles of efficiency, economy, integration of services, and prevention in an HMO. It is argued that the location of the program in a comprehensive organized health care setting enhances the efficacy of the treatment. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
103.
Conducted 3 experiments to investigate the effects of introducing mirror-image configurations into orientation and position discriminations. Ss were 4-8 yr. old children. Results of 2 experiments suggest that the question of mirror images may be irrelevant to the way in which young children differentiate orientation and position; i.e., as many errors were made in successive comparisons of obliques when the obliques were not mirror images as when they were. Similarly when they had to discriminate the positions of dots in squares, Ss confused left with right and up with down as much when the choice squares were asymmetrical as when they were symmetrical. It is suggested that young children adopt a binary match-mismatch code in orientation and position comparisons, which tells them whether lines parallel each other or not and whether objects are in line with each other or not. This code can solve some discriminations but not others. When the code fails, it does so as much with asymmetrical as with symmetrical configurations. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
104.
Three experiments with 204 undergraduates examined the hypothesis that an audience can inhibit overt practice and thereby impair learning of unfamiliar words and enhance learning of familiar words. This hypothesis was derived from an analysis of motoric and symbolic mediation during learning. In comparison with learning while alone, the results show that the audience inhibited overt practice of unfamiliar and familiar words and that reduced practice was detrimental to learning unfamiliar words. Inhibition of overt practice with an audience enhanced learning of familiar words in only 1 of the experiments. Instructions to practice overtly reduced the audience-inhibition effect in learning unfamiliar words. The studies are discussed in the context of drive-theory explanations for social facilitation effects in learning. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
105.
Review of book: R. Scott Tindale et. al (Eds.) Theory and Research on Small Groups. New York: Plenum Press. 1998, 277 pp. Reviewed by Mark F. Stasson, Michael J. Markus, and Jason W. Hart. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
106.
More than 80% of practicing psychologists recommend self-help books to their psychotherapy clients, but only 33% recommend autobiographies written by mental health patients. In this study, 362 psychologists (38% response) provided clinical information and evaluative ratings on such published autobiographical accounts. The effect of reading autobiographies during treatment was typically considered somewhat helpful. The titles and evaluative ratings of 40 leading autobiographies are provided as a resource for the practitioner; the most valued were An Unquiet Mind, Nobody Nowhere, Darkness Visible, Out of the Depths, and Girl Interrupted. The clinical advantages of recommending published autobiographies to clients are reviewed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
107.
108.
Site-directed mutagenesis was used to construct pepsin-resistant, single-point mutations of the N-terminal extended IGF-I analogue, long-R3-IGF-I. In order to identify the most susceptible sites, the kinetics of long-R3-IGF-I digestion by purified porcine pepsin were determined. Pepsin initially cleaved the Leu10-Phe11 bond in the N-terminal extension peptide to generate FVN-R3-IGF-I, followed in rapid succession by cleavage at Gln15-Phe16, Tyr24-Phe25, Leu10-Val11 and Met59-Tyr60 in the IGF-I moiety. Single-point mutations at these sites were designed on the basis of the preferred cleavage bonds for pepsin, as well as amino acid substitutions less likely to disturb protein structure. These included Leu10Val, Phe16Ala, Phe25Leu, Asp53Glu and Met59Gln. All five muteins retained growth-promoting activity equivalent to or higher than that of IGF-I. In terms of pepsin susceptibility, Leu10Val and Asp53Glu were degraded as rapidly as the parent long-R3-IGF-I, Met59Gln and Phe25Leu were partially stabilised, and Phe16Ala showed a marked improvement in stability over a wide range of pepsin:substrate ratios. Accordingly, the Phe16Ala mutein, long-R3A16-IGF-I, has potential for oral applications to enhance gastric growth and repair.  相似文献   
109.
1. Hypertensive cardiac hypertrophy is a major independent predictor of adverse cardiovascular events. In man the cardiac response to increased afterload is very variable, even when ambulatory blood pressure monitoring is used. Analysis of breeding experiments using normotensive and hypertensive rat strains, human twin studies and other data indicate that genetic factors play a significant role in regulating cardiac mass; in other words, a large component of total variability is accounted for by genetic variance. 2. The observation that some patients with only mild-to-moderate hypertension exhibit gross left ventricular hypertrophy (LVH) similar to the inherited hypertrophic cardiomyopathies such as familial hypertrophic cardiomyopathy (FHC) and Friedreich's ataxia (FA) has prompted us to investigate the hypothesis that genetic factors associated with excessive myocardial hypertrophy, viz. mutations in FHC and FA genes alter the hypertrophic response of the heart to pressure overload. Here we review briefly three lines of study: (i) association analysis to test whether the allele frequencies differ in hypertensive patients with or without left ventricular hypertrophy; (ii) characterization of the cardiac manifestations of FA to understand the mechanism by which the heart is affected in a disease associated with pathology in a subgroup of neurons, and (iii) creation of transgenic models to facilitate the investigation of the interaction between hypertrophic stimuli and underlying genetic predisposition. 3. Information on the nature of the cardiac-mass-modifying genes involved may be useful not only for selecting high risk patients in strategies aimed at preventing the development of LVH, but also in opening new avenues of research on the reprogramming of cardiac myocytes to encourage them to hypertrophy in situations where cardiac muscle has been damaged or is hypoplastic.  相似文献   
110.
BACKGROUND: In 1982, the National Surgical Adjuvant Breast and Bowel Project initiated a randomized, double-blinded, placebo-controlled trial (B-14) to determine the effectiveness of adjuvant tamoxifen therapy in patients with primary operable breast cancer who had estrogen receptor-positive tumors and no axillary lymph node involvement. The findings indicated that tamoxifen therapy provided substantial benefit to patients with early stage disease. However, questions arose about how long the observed benefit would persist, about the duration of therapy necessary to maintain maximum benefit, and about the nature and severity of adverse effects from prolonged treatment. PURPOSE: We evaluated the outcome of patients in the B-14 trial through 10 years of follow-up. In addition, the effects of 5 years versus more than 5 years of tamoxifen therapy were compared. METHODS: In the trial, patients were initially assigned to receive either tamoxifen at 20 mg/day (n = 1404) or placebo (n = 1414). Tamoxifen-treated patients who remained disease free after 5 years of therapy were then reassigned to receive either another 5 years of tamoxifen (n = 322) or 5 years of placebo (n = 321). After the study began, another group of patients who met the same protocol eligibility requirements as the randomly assigned patients were registered to receive tamoxifen (n = 1211). Registered patients who were disease free after 5 years of treatment were also randomly assigned to another 5 years of tamoxifen (n = 261) or to 5 years of placebo (n = 249). To compare 5 years with more than 5 years of tamoxifen therapy, data relating to all patients reassigned to an additional 5 years of the drug were combined. Patients who were not reassigned to either tamoxifen or placebo continued to be followed in the study. Survival, disease-free survival, and distant disease-free survival (relating to failure at distant sites) were estimated by use of the Kaplan-Meier method; differences between the treatment groups were assessed by use of the logrank test. The relative risks of failure (with 95% confidence intervals [CIs]) were determined by use of the Cox proportional hazards model. Reported P values are two-sided. RESULTS: Through 10 years of follow-up, a significant advantage in disease-free survival (69% versus 57%, P < .0001; relative risk = 0.66; 95% CI = 0.58-0.74), distant disease-free survival (76% versus 67%, P < .0001; relative risk = 0.70; 95% CI = 0.61-0.81), and survival (80% versus 76%, P = .02; relative risk = 0.84; 95% CI = 0.71-0.99) was found for patients in the group first assigned to receive tamoxifen. The survival benefit extended to those 49 years of age or younger and to those 50 years of age or older. Tamoxifen therapy was associated with a 37% reduction in the incidence of contralateral (opposite) breast cancer (P = .007). Through 4 years after the reassignment of tamoxifen-treated patients to either continued-therapy or placebo groups, advantages in disease-free survival (92% versus 86%, P = .003) and distant disease-free survival (96% versus 90%, P = .01) were found for those who discontinued tamoxifen treatment. Survival was 96% for those who discontinued tamoxifen compared with 94% for those who continued tamoxifen treatment (P = .08). A higher incidence of thromboembolic events was seen in tamoxifen-treated patients (through 5 years, 1.7% versus 0.4%). Except for endometrial cancer, the incidence of second cancers was not increased with tamoxifen therapy. CONCLUSIONS AND IMPLICATIONS: The benefit from 5 years of tamoxifen therapy persists through 10 years of follow-up. No additional advantage is obtained from continuing tamoxifen therapy for more than 5 years.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号