全文获取类型
收费全文 | 2582篇 |
免费 | 5篇 |
国内免费 | 3篇 |
专业分类
综合类 | 1篇 |
化学工业 | 30篇 |
金属工艺 | 16篇 |
机械仪表 | 7篇 |
建筑科学 | 8篇 |
能源动力 | 2篇 |
轻工业 | 8篇 |
无线电 | 30篇 |
一般工业技术 | 35篇 |
冶金工业 | 2411篇 |
原子能技术 | 1篇 |
自动化技术 | 41篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 8篇 |
2011年 | 17篇 |
2010年 | 10篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 88篇 |
1998年 | 754篇 |
1997年 | 462篇 |
1996年 | 280篇 |
1995年 | 159篇 |
1994年 | 116篇 |
1993年 | 160篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 27篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 23篇 |
1985年 | 16篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 21篇 |
1978年 | 6篇 |
1977年 | 56篇 |
1976年 | 116篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1959年 | 2篇 |
1957年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有2590条查询结果,搜索用时 0 毫秒
21.
The influence of the nicotine antagonist dihydro-beta-erythroidine (DH beta E) was examined on various behavioural effects of nicotine in rats. Motor activity was recorded in photocell cages whereas discriminative stimulus effects were examined using two-lever drug discrimination procedures with a tandem schedule of food reinforcement (n = 8 throughout). DH beta E (0.1-3.2 mg/kg) failed to antagonise the decreases in motor activity that nicotine (0.4-0.6 mg/kg) produced in experimentally naive rats, whereas mecamylamine (1.5 mg/kg) completely blocked this effect of nicotine. DH beta E (0.1-3.2 mg/kg) antagonised the increases in motor activity that nicotine (0.4 mg/kg) produced in rats with extensive previous exposure to both nicotine and the photocell apparatus. In rats trained to discriminate either 0.1 or 0.4 mg/kg nicotine from saline, DH beta E (0.1-3.2 mg/kg) blocked the discriminative stimulus effect of nicotine. The block of the discriminative effect could be reversed by increasing the dose of nicotine; DH beta E (1.6 mg/kg) shifted the dose-response curve for nicotine discrimination to the right by a factor of 9.4. In addition, nicotine in doses of 0.32-0.64 mg/kg decreased the overall rate of lever pressing but DH beta E (1.6 mg/kg) did not influence the dose-response curve for this effect. Thus, DH beta E potently blocked the locomotor activating and discriminative stimulus effects of nicotine at doses that did not antagonise its locomotor depressant and operant response rate-reducing effects. This selective blockade supports the involvement of different subtypes of nicotinic receptor in the mediation of diverse behavioural effects. Furthermore, the rightward shift of the dose-response curve for nicotine discrimination suggested a competitive mode of action for DH beta E. 相似文献
22.
23.
MG Narducci L Virgilio JB Engiles AM Buchberg L Billips A Facchiano CM Croce G Russo JL Rothstein 《Canadian Metallurgical Quarterly》1997,15(8):919-926
In human leukemias and lymphomas nonrandom chromosomal rearrangements cause changes in cell growth and/or survival in such a way as to promote malignancy. The detailed study of the biochemical and genetic pathways altered in human cancer requires the identification or development of models to allow the study and manipulation of cancer gene function. Recently, the breakpoint gene TCL1, involved in chromosome translocations observed mostly in mature T-cell proliferations and chronic lymphocytic leukemias (CLL), was isolated and characterized, and showed to be part of a new gene family of proteins involved in these tumors. The murine Tcl1 gene, is similar in sequence to the murine and human MTCP1 gene also involved in T cell leukemias. The murine Tcl1 gene was shown to reside on mouse chromosome 12 in a region syntenic to human chromosome 14. Furthermore, we show that the murine Tcl1 gene is expressed early in mouse embryonic development and demonstrates expression in fetal hematopoietic organs as well as in immature T and B cells. Characterization of the murine Tcl1 gene will help in developing a mouse model of CLL and would provide the best opportunity to study and decipher the role of TCL1 in malignant transformation. 相似文献
24.
25.
26.
27.
28.
The effects of acute pentobarbital treatment were assessed using a complex operant test battery containing five tasks in which correct performance is thought to depend upon processes associated with short-term memory and attention [delayed-matching-to-sample (DMTS)], color and position discrimination [conditioned position responding (CPR)], motivation [progressive ratio (PR)], time perception [temporal response differentiation (TRD)], and learning [incremental repeated acquisition (IRA)]. Adult, male rhesus monkeys were tested 15 min after IV injection of saline or pentobarbital (1, 3, 5.6, 10, or 15 mg/kg). Behavioral endpoints measured included percent task completed, response rate or latency, and response accuracy. The order of task sensitivity to disruption by PBT was TRD > IRA = DMTS = PR > CPR, in which sensitivity was defined as a significant disruption in any aspect of task performance. PBT slowed response rates at 10.0 and/or 15.0 mg/kg in all tasks. Accuracy was decreased in the TRD task at > or = 5.6 mg/kg but doses of > or = 10.0 mg/kg were required to decrease accuracy in the IRA, DMTS, and CPR tasks. Thus, behavior thought to model time perception (TRD) was more sensitive than behavior modeling learning (IRA), short-term memory and attention (DMTS), and motivation (PR). CPR was the least sensitive behavior. Because pentobarbital exerts its effects at least in part via GABA systems, the effects in the current study were compared with those of a previous study of the acute effects of diazepam. The two compounds exerted fundamentally different effects on operant test battery performance. 相似文献
29.
MC Bonhomme KL Grove S Caron CT Crilley G Thibault CF Deschepper R Garcia 《Canadian Metallurgical Quarterly》1998,9(10):1777-1786
The natriuretic peptide receptor (NPR) family consists of three receptor subtypes: two transmembrane forms that contain a guanylyl cyclase intracellular domain (NPR-A and NPR-B), and one truncated form (NPR-C). Because of the lack of specific agonists and antagonists for each receptor subtype and to the difficulty to detect the presence of small quantities of NPR-B by ligand binding studies, polyclonal antibodies against a peptide whose sequence was chosen from a region of the extracellular domain of rat NPR-B that is not homologous to sequences in NPR-A and NPR-C were developed. Western blotting with affinity-purified anti-NPR-B (413-426)-Tyr revealed a polypeptide of approximately 120 kD on COS-1 cell membranes transfected with rat NPR-B cDNA. The antibody recognized a second polypeptide, approximately 5 to 10 kD smaller, which probably represents the unglycosylated receptor. Anti-NPR-B (413-426)-Tyr did not show crossreactivity to any other NPR. Western blotting analysis with anti-NPR-B (413-426)-Tyr also identified a protein of appropriate size in renal vascular membranes. These results were supported by immunohistochemistry findings that demonstrated staining for NPR-B on papillary and medullary capillaries, glomeruli, and renal arteries. This study concludes that NPR-B is present in the rat kidney, although it was only detected in vascular structures. 相似文献
30.