全文获取类型
收费全文 | 5490篇 |
免费 | 137篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 54篇 |
综合类 | 4篇 |
化学工业 | 1164篇 |
金属工艺 | 89篇 |
机械仪表 | 92篇 |
建筑科学 | 190篇 |
矿业工程 | 18篇 |
能源动力 | 133篇 |
轻工业 | 381篇 |
水利工程 | 68篇 |
石油天然气 | 22篇 |
无线电 | 333篇 |
一般工业技术 | 846篇 |
冶金工业 | 1583篇 |
原子能技术 | 32篇 |
自动化技术 | 621篇 |
出版年
2021年 | 70篇 |
2020年 | 45篇 |
2019年 | 56篇 |
2018年 | 68篇 |
2017年 | 77篇 |
2016年 | 78篇 |
2015年 | 65篇 |
2014年 | 106篇 |
2013年 | 288篇 |
2012年 | 149篇 |
2011年 | 229篇 |
2010年 | 207篇 |
2009年 | 192篇 |
2008年 | 211篇 |
2007年 | 202篇 |
2006年 | 214篇 |
2005年 | 183篇 |
2004年 | 161篇 |
2003年 | 168篇 |
2002年 | 125篇 |
2001年 | 104篇 |
2000年 | 107篇 |
1999年 | 111篇 |
1998年 | 246篇 |
1997年 | 183篇 |
1996年 | 140篇 |
1995年 | 130篇 |
1994年 | 134篇 |
1993年 | 110篇 |
1992年 | 104篇 |
1991年 | 55篇 |
1990年 | 87篇 |
1989年 | 72篇 |
1988年 | 73篇 |
1987年 | 65篇 |
1986年 | 60篇 |
1985年 | 86篇 |
1984年 | 85篇 |
1983年 | 75篇 |
1982年 | 60篇 |
1981年 | 53篇 |
1980年 | 46篇 |
1979年 | 57篇 |
1978年 | 59篇 |
1977年 | 56篇 |
1976年 | 69篇 |
1975年 | 35篇 |
1974年 | 40篇 |
1973年 | 30篇 |
1972年 | 33篇 |
排序方式: 共有5630条查询结果,搜索用时 31 毫秒
51.
Environmentally responsive hydrogels have become attractive research subjects for many applications. In this work, a series of pH‐sensitive and color‐changing nanoparticles (nanogels) with core–shell structures were synthesized. The cores were blue latex particles synthesized by a miniemulsion technique with styrene and methacrylic acid as monomers and Neozapon Blue 807 as a dye. The shell was a pH‐sensitive polymer that was precipitation‐polymerized onto the core from 2‐(diethylamino) ethyl methacrylate with N,N′‐methylenebisacrylamide, poly(propylene glycol) diacrylate, and divinylbenzene as crosslinking agents. In the resultant latexes, the color was observed to change from deep blue to pale blue as the pH of the system was changed from a high of 10 to a low of 3. The synthesized latexes and particles (gels) were then characterized with an ultraviolet–visible spectrometer, dynamic light scattering, Fourier transform infrared, and nuclear magnetic resonance. Atomic force microscopy was also used to investigate the different morphologies of the particles after the synthesized latexes were dried at different pH values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
52.
Higher testosterone levels are related to assertiveness and dominance. Given the relevance of those behavioral correlates to spouses' daily transactions, links between testosterone levels and marital interaction were explored among 92 newlywed couples. Marital problem-solving and social support transactions were assessed, and saliva was collected and assayed for testosterone. Whether marital behavior was related to husbands' and wives' testosterone levels was examined. The link between spouses' testosterone and their behavior was contingent on the partner's testosterone levels. Husbands exhibited more adaptive problem-solving behaviors and social support provision when husbands and wives were concordant for lower testosterone levels. In contrast, wives exhibited more adaptive support provision when spouses had discordant testosterone levels such that wives had higher levels and husbands had lower levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
53.
This study compared the effects of estrogen (E) on the hyperactivity induced by (+)-3,4-methylenedioxymethamphetamine (MDMA) with E effects on cocaine-evoked hyperactivity in female rats. Sprague-Dawley rats were ovariectomized (OVX); half of them received a 17β-estradiol (E?) implant (OVX + E). Three weeks later, rats received saline, (+)-MDMA (1, 2, or 4 mg/kg) or cocaine (5, 10, or 20 mg/kg), and locomotor activity was monitored. OVX + E rats exhibited greater locomotor hyperactivity in response to both psychostimulants than did OVX rats. The enhanced response to cocaine appeared within 5 min following drug injection whereas the enhanced response to (+)-MDMA was delayed for approximately 30 min. The differential effects of E on hyperactivity may be due to the unique profiles of dopamine (DA) and serotonin (5-HT) in response to (+)-MDMA and cocaine. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
Harris Grant T.; Rice Marnie E.; Quinsey Vernon L.; Lalumière Martin L.; Boer Douglas; Lang Carol 《Canadian Metallurgical Quarterly》2003,15(3):413
Four actuarial instruments for the prediction of violent and sexual reoffending (the Violence Risk Appraisal Guide [VRAG], Sex Offender Risk Appraisal Guide [SORAG], Rapid Risk Assessment for Sex Offender Recidivism [RRASOR], and Static-99) were evaluated in 4 samples of sex offenders (N = 396). Although all 4 instruments predicted violent (including sexual) recidivism and recidivism known to be sexually motivated, areas under the receiver operating characteristic (ROC) were consistently higher for the VRAG and the SORAG. The instruments performed better when there were fewer missing items and follow-up time was fixed, with an ROC area up to .84 for the VRAG, for example, under such favorable conditions. Predictive accuracy was higher for child molesters than for rapists, especially for the Static-99 and the RRASOR. Consistent with past research, survival analyses revealed that those offenders high in both psychopathy and sexual deviance were an especially high-risk group. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
Piasecki Thomas M.; Jorenby Douglas E.; Smith Stevens S.; Fiore Michael C.; Baker Timothy B. 《Canadian Metallurgical Quarterly》2003,11(4):276
Five parameters of postcessation smoking withdrawal variability derived from clinical data (T. M. Piasecki, D. E. Jorenby, S. S. Smith, M. C. Fiore, & T. B. Baker, 2003a, 2003b) were predicted from baseline measures and pharmacotherapy assignment. Smokers who were more dependent, older, and high in negative affect reported more severe withdrawal. Women, heavier smokers, and those with a history of depression reported more variable symptoms. Smokers treated with nicotine patch, bupropion, or both reported less severe withdrawal than did those given placebo, but medication did not affect the slope of symptoms over time, day-to-day variability of symptoms, or the size of acute changes in symptoms associated with lapses to smoking. Prior research has shown that these symptom facets predict later relapse: thus, current pharmacotherapies may aid cessation by diminishing withdrawal severity, but they do not affect all clinically important aspects of withdrawal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
W. S. Holland P. A. R. Ade M. J. Griffin I. D. Hepburn D. G. Vickers C. R. Cunningham P. R. Hastings W. K. Gear W. D. Duncan T. E. C. Baillie E. E. Haller J. W. Beeman 《Journal of Infrared, Millimeter and Terahertz Waves》1996,17(4):669-692
We describe the design and construction of bolometric detectors for SCUBA - the Submillimetre Common-User Bolometer Array for the James Clerk Maxwell Telescope in Hawaii. The instrument contains 131 individual detectors, in two arrays, optimized for the submillimetre atmospheric transmission windows. The detectors are cooled by dilution refrigeration to a temperature of 100 mK, so that the receiver performance will be limited by photon noise from the sky and telescope background in all wavebands. A future paper will describe the performance of the detectors with reference to typical data obtained during the laboratory commissioning period. 相似文献
57.
GR Douglas J Jiao JD Gingerich LM Soper JA Gossen 《Canadian Metallurgical Quarterly》1996,28(4):317-324
In order to help establish criteria for optimizing protocols for in vivo mutation studies, lacZ transgenic mice (Muta mouse) were treated with five consecutive daily doses of ethylnitrosourea (50 mg/kg), sampled at times up to 55 days after treatment, and mutant frequencies and DNA sequences determined for liver and bone marrow. In the bone marrow, the mutant frequency rose very rapidly in the first 5 days after treatment to 34 times the control frequency. Subsequently, there was a brood peak where the mutant frequency did not vary significantly, although it did appear to begin to decline after 45 days. In contrast, in the liver, the peak mutant frequency (11 times the control frequency) was not achieved until 35 days, after which there appeared to be a slow decline up to 55 days, which was not statistically significant. Once the maximum mutant frequency was reached, the mutation spectra in the two tissues were indistinguishable. In contrast to the G:C-->A:T transitions in 5'-CpG sites characteristic of untreated mice, A:T-->T:A transversions and A:T-->G:C transitions were prominent in both liver and bone marrow of ENU-treated mice, suggesting the involvement of unrepaired O2- and O4-ethylthymine adducts. In addition, G:C-->T:A transversions were induced in liver. This study demonstrates the possibility that although tissues may have different mutation fixation times, a single mutation fixation time equal to the longest time may be appropriate for in vivo mutation studies, provided that the mutation frequency does not decline appreciably after the peak is reached. This study also illustrates the necessity of ensuring that mutation characteristics are determined after optimal fixation has occurred. 相似文献
58.
Douglas E. Olesen 《The Electricity Journal》1995,8(10)
Technology developments on the horizon promise to transform the electricity industry far from its present shape and structure. But, just as technology has played a critical role in pushing the industry to its present thrust toward competition and vertical de-integration, a sensible technology policy can make a utility or power supplier a winmer tomorrow. 相似文献
59.
60.
Cunningham Stacey C.; Corrigan Sheila A.; Malow Robert M.; Smason Ivan H. 《Canadian Metallurgical Quarterly》1993,7(4):246
Assessed the differences between cocaine- and cocaine-plus-alcohol-dependent inpatients along several psychological variables. Of the 144 men that served as Ss, 113 were cocaine dependent and 31 were dependent on both cocaine and alcohol (CD-AD). CD-AD Ss showed significantly more symptoms of depression and anxiety and were more likely to have antisocial and avoidant personality disorders. The CD-AD group scored higher overall on the MMPI clinical scales. Results suggest that patients dependent on both cocaine and alcohol require increased attention to psychopathology during treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献