全文获取类型
收费全文 | 4881篇 |
免费 | 159篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 38篇 |
综合类 | 6篇 |
化学工业 | 804篇 |
金属工艺 | 57篇 |
机械仪表 | 55篇 |
建筑科学 | 184篇 |
矿业工程 | 9篇 |
能源动力 | 96篇 |
轻工业 | 610篇 |
水利工程 | 54篇 |
石油天然气 | 3篇 |
无线电 | 315篇 |
一般工业技术 | 596篇 |
冶金工业 | 1808篇 |
原子能技术 | 27篇 |
自动化技术 | 382篇 |
出版年
2023年 | 47篇 |
2022年 | 102篇 |
2021年 | 111篇 |
2020年 | 67篇 |
2019年 | 63篇 |
2018年 | 87篇 |
2017年 | 75篇 |
2016年 | 94篇 |
2015年 | 74篇 |
2014年 | 86篇 |
2013年 | 197篇 |
2012年 | 162篇 |
2011年 | 261篇 |
2010年 | 191篇 |
2009年 | 197篇 |
2008年 | 244篇 |
2007年 | 215篇 |
2006年 | 204篇 |
2005年 | 169篇 |
2004年 | 140篇 |
2003年 | 122篇 |
2002年 | 144篇 |
2001年 | 102篇 |
2000年 | 87篇 |
1999年 | 108篇 |
1998年 | 297篇 |
1997年 | 219篇 |
1996年 | 152篇 |
1995年 | 118篇 |
1994年 | 119篇 |
1993年 | 102篇 |
1992年 | 70篇 |
1991年 | 42篇 |
1990年 | 57篇 |
1989年 | 53篇 |
1988年 | 49篇 |
1987年 | 41篇 |
1986年 | 27篇 |
1985年 | 35篇 |
1984年 | 32篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 16篇 |
1980年 | 21篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 31篇 |
1976年 | 46篇 |
1975年 | 12篇 |
1973年 | 10篇 |
排序方式: 共有5044条查询结果,搜索用时 15 毫秒
41.
Liew Jeffrey; Eisenberg Nancy; Losoya Sandra H.; Fabes Richard A.; Guthrie Ivanna K.; Murphy Bridget C. 《Canadian Metallurgical Quarterly》2003,17(4):584
Relations of heart rate and skin conductance reactions to mildly evocative empathy-inducing slides with socioemotional functioning were examined for 154 children (mean age = 9 years, 5 months). In addition, maternal expressivity was tested as a moderator of these relations. Parents and teachers rated children's socioemotional functioning, and a behavioral measure of children's regulation was obtained. Boys who exhibited higher skin conductance and higher heart rate to slides depicting negative emotions were better regulated, less emotionally intense, and better adjusted than their peers. Furthermore, boys' regulation and adjustment were positively related to such physiological responding to negative slides if maternal negative expressivity was relatively low or moderate, but not high. Fewer findings were obtained for girls or for positive slides. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
Friedman Sara R.; Rapport Lisa J.; Lumley Mark; Tzelepis Angela; VanVoorhis Amy; Stettner Lawrence; Kakaati Laura 《Canadian Metallurgical Quarterly》2003,17(1):50
Social and emotional competence were evaluated using self-report and behavioral measures in adults with attention-deficit/hyperactivity disorder (ADHD) and controls. Adults with ADHD viewed themselves as less socially competent but more sensitive toward violations of social norms than controls. Films depicting emotional interactions were used to assess linguistic properties of free recall and perceived emotional intensity. Although adults with ADHD used more words to describe the scenes, they used fewer emotion-related words, despite rating the emotions depicted as more intense than did controls. In contrast, no group differences for words depicting social or cognitive processes were observed. Overall, adults with ADHD appear more aware of their problems in social versus emotional skills. Findings may have implications for improving the psychosocial functioning of these adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
Matrix metalloproteinases are thought to be key players in the remodelling activity of cells associated with both physiological and pathological processes. They share a relatively conserved structure with a number of identifiable modules linked to their specific functions. The structure of the individual domains of a number of matrix metalloproteinases have now been elucidated. Here we review these data in the light of complementary studies on the behaviour of these enzymes in biological systems. In particular we focus on the C-terminal hemopexin-like domain which has intriguingly specific roles in individual matrix metalloproteinases. 相似文献
44.
KM Borow A Neumann RM Lang D Ehler B Valentine-Bates A Wolff K Friday M Murphy 《Canadian Metallurgical Quarterly》1993,21(4):939-949
BACKGROUND: Alveolar macrophages from patients with sarcoidosis were analyzed for their ability to secrete tumor necrosis factor-alpha (TNF-alpha), interleukin-1-beta (IL-1-beta), and interleukin-6 (IL-6). RESULTS: Constitutive release of all three monokines in these patients was concomitantly increased in the active state of disease in comparison with inactive sarcoidosis or healthy control subjects. Alveolar macrophages from patients with inactive sarcoidosis compared with cells from healthy subjects showed increased spontaneous secretion of TNF-alpha and IL-6 only, whereas the constitutive release of IL-1-beta was similar as in healthy volunteers. In vitro stimulation of alveolar macrophages from healthy control subjects with lipopolysaccharide or pokeweed mitogen led to a time- and dose-dependent enhanced secretion of TNF-alpha, IL-1-beta, and IL-6. In a similar manner, with corresponding cells from patients with sarcoidosis the secretion of all three cytokines could be further increased by stimulation with lipopolysaccharide or pokeweed mitogen. CONCLUSIONS: The data presented indicate that an increased release of TNF-alpha, IL-1-beta, and IL-6 correlates to disease activity and may play a critical part in the pathogenesis of sarcoidosis. 相似文献
45.
ML McLaws C Murphy P Taylor M Ferson J Gold R Donnellan D Dalton 《Canadian Metallurgical Quarterly》1997,18(11):778-780
The rate of nosocomial respiratory syncytial virus (RSV) infection was measured in a large pediatric hospital using an incidence density method. The at-risk days for nosocomial RSV were summed during a defined winter period in which there were 54 admissions with community-acquired RSV infection giving a rate of 2.9 cases per 1,000 at-risk days (95% confidence interval, 0.3-5.4 per 1,000). 相似文献
46.
47.
The ingestion of I-131 by pregnant women can have consequences for the developing foetus, in particular brain function. As the foetal thyroid accumulates iodine from the twelfth week of gestation onwards, the determination of foetal brain dose resulting from such I-131 accumulation is essential. Normal dosimetric methods fail to treat the case of foetus. Using an approximation method based on the MIRD approach, a foetal dose estimation scheme is developed to allow the determination of foetal brain dose from foetal thyroid irradiation. Dose values are obtained for the foetus based on the maternal intake of I-131. It was found that the choice of biokinetic model for the mother/foetus has a large impact on the determined dose estimate. 相似文献
48.
49.
The authors of [Remarks on the LUC public key system, see ibid., vol. 30, p. 123, 1994] consider the Lucas function on which the public cryptosystem LUC proposed by Smith and Lennon [1993] is based. For a finite field G with m∈G, the Lucas function Vn(m) is defined by the second order linear recurrence relation Vn(m)=mVn-1(m)-Vn-2(m) where Vo (m)=2, V1(m)=m. The characteristic polynomial f of the Lucas function is f(x)=x2-mx+1, and Vx(m)=α x+α-x where α is a root of f. We now consider some of the results of and give concise proofs 相似文献
50.
When the phenotype of neurons in pre- and paravertebral sympathetic ganglia are compared, there are marked differences in NGF dependence, neuropeptide content, connectivity and electrophysiological properties. The trophic interactions that induce these differences are currently poorly understood. One explanation is that prevertebral neurons receive a second neurotrophic signal, other than NGF, from their target of innervation. If this is the case, neurons in the prevertebral ganglia should express another neurotrophin receptor, in addition to the NGF receptor (trkA). To test this prediction, the level of expression of three neurotrophin receptors, trkA, trkB and trkC, were examined in one paravertebral sympathetic ganglia, the SCG, and two prevertebral ganglia, the celiac and superior mesenteric ganglia. It was found that mRNA encoding the full-length form of the trkB receptor was barely expressed in the SCG. Significantly higher levels of full-length trkB mRNA expression were found in the prevertebral ganglia. Ligands of the trkB receptor may, therefore, contribute to the differentiation and/or survival of some prevertebral sympathetic neurons. 相似文献