全文获取类型
收费全文 | 3759篇 |
免费 | 34篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
综合类 | 6篇 |
化学工业 | 133篇 |
金属工艺 | 4篇 |
机械仪表 | 35篇 |
建筑科学 | 21篇 |
矿业工程 | 5篇 |
能源动力 | 30篇 |
轻工业 | 119篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 117篇 |
一般工业技术 | 154篇 |
冶金工业 | 3020篇 |
原子能技术 | 6篇 |
自动化技术 | 123篇 |
出版年
2023年 | 9篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 20篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 13篇 |
2014年 | 23篇 |
2013年 | 39篇 |
2012年 | 17篇 |
2011年 | 34篇 |
2010年 | 16篇 |
2009年 | 24篇 |
2008年 | 33篇 |
2007年 | 33篇 |
2006年 | 28篇 |
2005年 | 33篇 |
2004年 | 25篇 |
2003年 | 29篇 |
2002年 | 36篇 |
2001年 | 22篇 |
2000年 | 30篇 |
1999年 | 124篇 |
1998年 | 966篇 |
1997年 | 543篇 |
1996年 | 379篇 |
1995年 | 192篇 |
1994年 | 166篇 |
1993年 | 210篇 |
1992年 | 30篇 |
1991年 | 37篇 |
1990年 | 48篇 |
1989年 | 52篇 |
1988年 | 40篇 |
1987年 | 37篇 |
1986年 | 35篇 |
1985年 | 41篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 23篇 |
1981年 | 15篇 |
1980年 | 38篇 |
1978年 | 9篇 |
1977年 | 61篇 |
1976年 | 117篇 |
1973年 | 11篇 |
1971年 | 6篇 |
1966年 | 6篇 |
排序方式: 共有3794条查询结果,搜索用时 0 毫秒
21.
MD Cohen ST Auringer JL Grosfeld CA Galliani NA Heerema 《Canadian Metallurgical Quarterly》1993,23(6):463-466
The purpose of this study is to present three patients with multifocal primary neuroblastoma, to review the literature, and describe the radiographic findings. SUBJECTS AND METHODS: Three children with multifocal neuroblastoma have been identified. The case histories and imaging findings in these patients are reviewed. RESULTS: Two children had synchronous and one child had metachronous multifocal primary neuroblastoma. The primary tumors were both in the abdomen in one patient, both in the chest in another patient, and in the chest and abdomen in the third patient. Evidence for multifocal origin of these tumors, rather than metastatic spread, is presented. CONCLUSION: Multifocal primary neuroblastomas can occur. The tumors maybe synchronous or metachronous. Awareness of this disorder may prevent errors in diagnosis and staging. Although not identified in our patients there is a strong familial incidence of neuroblastomas in those patients with multifocal tumors. 相似文献
22.
23.
Pulmonary surfactant is a complex mixture of lipids and proteins that functions to keep alveoli from collapsing at the end of expiration. Dipalmitoylphosphatidylcholine has been identified as the most important component for lowering surface tension at the air-liquid interface. Hydrophobic surfactant apoproteins, SP-B and SP-C, play essential roles in the biophysical functions of the surfactant phospholipids. Hydrophilic surfactant apoproteins (SP-A and SP-D) that are members of C-type lectin superfamily, interact with phospholipids and glycolipids and modulate host defense functions in the lung. SP-A also plays an important role in regulating phospholipid homeostasis in the alveolar spaces. Recent advances in genetics and molecular biology have clarified the structure-function relationship of surfactant apoproteins. 相似文献
24.
25.
26.
27.
28.
The activity of rifabutin (LM 427) against Mycobacterium leprae was evaluated in armadillos inoculated earlier with human-derived M. leprae. Rifabutin was administered daily at a dose of 6 mg/kg body weight/day. The effect of rifabutin on M. leprae harvested from armadillos was determined by measuring the intracellular levels of ATP (an indicator of metabolic activity) of M. leprae and also their ability to multiply in the mouse footpads and in vitro in DH medium. Within 2 weeks of initiating the treatment, ATP levels declined to 21% of the original (pre-treatment level) and these M. leprae failed to multiply in the footpads of mice as well as in the in vitro culture system. This suggests that rifabutin was able to kill all M. leprae within 2 weeks. After 8 weeks the treatment was terminated and results showed that M. leprae from the treated armadillos remained non-viable in the mouse footpad system as well as in the in vitro system, indicating bactericidal action of rifabutin. The results suggest that rifabutin can be a substitute for rifampin in the leprosy multi-drug therapy regimen. 相似文献
29.
SJ Mihic Q Ye MJ Wick VV Koltchine MD Krasowski SE Finn MP Mascia CF Valenzuela KK Hanson EP Greenblatt RA Harris NL Harrison 《Canadian Metallurgical Quarterly》1997,389(6649):385-389
Volatile anaesthetics have historically been considered to act in a nonspecific manner on the central nervous system. More recent studies, however, have revealed that the receptors for inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) and glycine are sensitive to clinically relevant concentrations of inhaled anaesthetics. The function of GABA(A) and glycine receptors is enhanced by a number of anaesthetics and alcohols, whereas activity of the related GABA rho1 receptor is reduced. We have used this difference in pharmacology to investigate the molecular basis for modulation of these receptors by anaesthetics and alcohols. By using chimaeric receptor constructs, we have identified a region of 45 amino-acid residues that is both necessary and sufficient for the enhancement of receptor function. Within this region, two specific amino-acid residues in transmembrane domains 2 and 3 are critical for allosteric modulation of both GABA(A) and glycine receptors by alcohols and two volatile anaesthetics. These observations support the idea that anaesthetics exert a specific effect on these ion-channel proteins, and allow for the future testing of specific hypotheses of the action of anaesthetics. 相似文献