全文获取类型
收费全文 | 25905篇 |
免费 | 3150篇 |
国内免费 | 1495篇 |
专业分类
电工技术 | 2270篇 |
综合类 | 2538篇 |
化学工业 | 2291篇 |
金属工艺 | 533篇 |
机械仪表 | 1525篇 |
建筑科学 | 3288篇 |
矿业工程 | 374篇 |
能源动力 | 1139篇 |
轻工业 | 4870篇 |
水利工程 | 2187篇 |
石油天然气 | 859篇 |
武器工业 | 296篇 |
无线电 | 1578篇 |
一般工业技术 | 3055篇 |
冶金工业 | 1212篇 |
原子能技术 | 465篇 |
自动化技术 | 2070篇 |
出版年
2024年 | 160篇 |
2023年 | 558篇 |
2022年 | 1190篇 |
2021年 | 1357篇 |
2020年 | 1248篇 |
2019年 | 1120篇 |
2018年 | 995篇 |
2017年 | 1167篇 |
2016年 | 1202篇 |
2015年 | 1256篇 |
2014年 | 1536篇 |
2013年 | 1689篇 |
2012年 | 2202篇 |
2011年 | 2211篇 |
2010年 | 1375篇 |
2009年 | 1366篇 |
2008年 | 1260篇 |
2007年 | 1377篇 |
2006年 | 1219篇 |
2005年 | 1009篇 |
2004年 | 769篇 |
2003年 | 688篇 |
2002年 | 496篇 |
2001年 | 445篇 |
2000年 | 349篇 |
1999年 | 327篇 |
1998年 | 291篇 |
1997年 | 226篇 |
1996年 | 180篇 |
1995年 | 184篇 |
1994年 | 156篇 |
1993年 | 141篇 |
1992年 | 124篇 |
1991年 | 82篇 |
1990年 | 82篇 |
1989年 | 62篇 |
1988年 | 54篇 |
1987年 | 39篇 |
1986年 | 29篇 |
1985年 | 31篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1965年 | 15篇 |
1964年 | 19篇 |
1963年 | 15篇 |
1961年 | 13篇 |
1957年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
81.
Tucker Don M.; Luu Phan; Frishkoff Gwen; Quiring Jason; Poulsen Catherine 《Canadian Metallurgical Quarterly》2003,112(4):667
Functional neuroimaging suggests that limbic regions of the medial frontal cortex may be abnormally active in individuals with depression. These regions, including the anterior cingulate cortex, are engaged in both action regulation, such as monitoring errors and conflict, and affect regulation, such as responding to pain. The authors examined whether clinically depressed subjects would show abnormal sensitivity of frontolimbic networks as they evaluated negative feedback. Depressed subjects and matched control subjects performed a video game in the laboratory as a 256-channel EEG was recorded. Speed of performance on each trial was graded with a feedback signal of A, C, or F. By 350 ms after the feedback signal, depressed subjects showed a larger medial frontal negativity for all feedback compared with control subjects with a particularly striking response to the F grade. This response was strongest for moderately depressed subjects and was attenuated for subjects who were more severely depressed. Localization analyses suggested that negative feedback engaged sources in the anterior cingulate and insular cortices. These results suggest that moderate depression may sensitize limbic networks to respond strongly to aversive events. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
82.
Learning a sequence of target locations when the sequence is uncorrelated with a sequence of responses and target location is not the response dimension (pure perceptual-based sequence learning) was examined. Using probabilistic sequences of target locations, the author shows that such learning can be implicit, is unaffected by distance between target locations, and is mostly limited to first-order transition probabilities. Moreover, the mechanism underlying learning affords processing of information at anticipated target locations and appears to be attention based. Implications for hypotheses of implicit sequence learning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
83.
小儿的心理状态与成人有着明显的差异,在其住院和接受医疗期间可出现严重的心理反应,导致植物神经功能紊乱,使机体低抗力下降,而削弱机体对麻药的耐受力,不利于麻醉诱导及管理,而且还会造成小儿的精神创伤。文章初步探讨了小儿麻醉心理学的有关问题。 相似文献
84.
高分辨率双侧向测井响应数值模拟分析 总被引:6,自引:0,他引:6
我国自行研制的新型的高分辨率双侧向测井仪已逐渐投入大规模的生产应用,可为解决油田薄层油气藏的勘探开发问题提供有力的支持。本文利用有限元方法对新型的高分辨率双侧向测井仪及国内目前大规模应用的常规双侧向测井仪的分层能力、探测深度、侵入影响和井眼影响等响应特征进行了数值模拟,并对其测井响应进行了对比分析。数值模拟表明:与常规双侧向测井相比,虽然高分辨率双侧向测井资料井眼的影响更复杂,但测量结果既能得到较高纵向分辨率,又具有较深的径向探测深度,基本上可以取代常规双侧向测井仪在测井中应用。文中数值模拟结果可以为测井作业人员和解释人员在资料验收及解释处理等方面提供参考和指导。 相似文献
85.
George Grant Fiona Greer Norma H. McKenzie Arpad Pusztai 《Journal of the science of food and agriculture》1985,36(5):409-414
In a series of 10-day pair feeding experiments it was found that the nutritional value of diets containing beans was essentially the same for rats aged between 30 and 123 days. Thus net protein utilisation (NPU) values of 25–39 on diets containing Processor bean (35 g protein kg?1) + egg albumin (65g protein kg?1) were obtained. As food intakes were considerably reduced when rats were fed diets containing more than 35g protein kg?1 of Processor bean, the measurement of protein utilisation became increasingly more difficult. The severe disruption of the brush borders of duodenal and jejunal enterocytes, originally observed when bean-containing diets were fed to young (30-day-old) rats was also found with rats up to the age of 120 days on similar diets. Similarly, the development of circulating anti-lectin antibodies in the animals showed no age dependence within the age limits investigated. It was also shown that oral immunisation did not protect the rats from the effects of toxicity and that the immune response was a result of continuous absorption of lectin throughout the feeding period. Thus the extent and the mechanism of toxicity of Phaseolus vulgaris bean lectins were found not to be dependent on the age or maturity of the animal. 相似文献
86.
The authors examined whether participants can shift their criterion for recognition decisions in response to the probability that an item was previously studied. Participants in 3 experiments were given recognition tests in which the probability that an item was studied was correlated with its location during the test. Results from all 3 experiments indicated that participants' response criteria were sensitive to the probability that an item was previously studied and that shifts in criterion were robust. In addition, awareness of the bases for criterion shifts and feedback on performance were key factors contributing to the observed shifts in decision criteria. These data suggest that decision processes can operate in a dynamic fashion, shifting from item to item. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
S. M. Fitzpatrick D. Miller I. Weatherston J. N. McNeil 《Journal of chemical ecology》1985,11(2):207-215
Levels of benzaldehyde recovered from virginPseudaletia unipuncta (Haw.) males were not influenced by (1) the time hairpencils remained in the solvent (1-72 hr), (2) anesthetization or agitation of males prior to excision of hairpencils, or (3) the time (photophase or scotophase) that hairpencils were excised. Thus the interindividual variability observed is not a methodological artifact. Most males had similar concentrations in both hairpencils, although in some cases only one hairpencil contained pheromone. In one case, a male with partially extruded hairpencils had no benzaldehyde at all. Neither pupal weight nor hairpencil length proved to be reliable indicators of pheromone content.Contribution No. 373, Département de biologie, Université Laval. 相似文献
88.
89.
90.
T. D. M. Weijers H. Timmers R. G. Elliman 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):397-401
The impact of the pulse height deficit effect in gas ionization detectors on the accurate extraction of depth information from heavy ion elastic recoil detection spectra has been investigated. Thin GaN films and GexSi1−x/Si heterostructures have been analyzed with a 200 MeV 197Au beam. Employing an empirical parameterisation of the pulse height deficit, a global energy calibration of the detector can be achieved. Energy spectra have been compared, calibrated with either a constant or a full energy-dependent compensation for the deficit. A constant compensation results in significant distortion of the extracted depth profile for heavier ions, whereas an energy-dependent compensation yields true concentration–depth profiles. 相似文献