全文获取类型
收费全文 | 4122篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 20篇 |
金属工艺 | 1篇 |
机械仪表 | 4篇 |
建筑科学 | 3篇 |
轻工业 | 8篇 |
无线电 | 4篇 |
一般工业技术 | 17篇 |
冶金工业 | 4061篇 |
自动化技术 | 7篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 130篇 |
1998年 | 1369篇 |
1997年 | 765篇 |
1996年 | 457篇 |
1995年 | 272篇 |
1994年 | 230篇 |
1993年 | 235篇 |
1992年 | 29篇 |
1991年 | 54篇 |
1990年 | 38篇 |
1989年 | 37篇 |
1988年 | 48篇 |
1987年 | 45篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 1篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 21篇 |
1980年 | 30篇 |
1978年 | 8篇 |
1977年 | 80篇 |
1976年 | 133篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有4126条查询结果,搜索用时 31 毫秒
981.
SM Sine 《Canadian Metallurgical Quarterly》1997,272(38):23521-23527
Cysteine was introduced from residues 116 to 121 of the gamma subunit of the fetal mouse acetylcholine receptor, and the mutant receptors were treated with methanethiosulfonate reagents and examined for changes in ligand binding properties. Of the 18 combinations of mutant and reagent, only receptors harboring gammaL119C treated with the quaternary ammonium reagent MTSET (trimethylammonium-ethyl methanethiosulfonate) show a decreased number of alpha-bungarotoxin (alpha-btx) sites. The decrease of 50% suggests that alpha-btx binding to the site harboring gammaL119C is blocked. Analysis of binding of the site-selective ligands dimethyl-d-tubocurarine (DMT) and alpha-conotoxin M1 (CTX) confirm specificity of modification for the site harboring gammaL119C. Cysteines placed at equivalent positions of the delta and epsilon subunits also lead to selective loss of alpha-btx binding following MTSET treatment. gammaL119C receptors treated with the primary amine reagent MTSEA (aminoethyl methanethiosulfonate) retain alpha-btx binding to both sites but show reduced affinity for DMT and CTX at the modified site. Lysine mutagenesis of Leugamma119, Leudelta121, and Leuepsilon119 mimics MTSEA treatment, whereas mutagenesis of Thralpha119 and Glnbeta119 is without effect, demonstrating subunit and residue specificity of MTSEA modification. MTSET modification of nearby gammaY117C does not block alpha-btx binding but markedly diminishes affinity for DMT and CTX. The overall findings indicate a localized point of interaction between alpha-btx and the modified gammaL119C, deltaL121C, and epsilonL119C. 相似文献
982.
SM Aronson 《Canadian Metallurgical Quarterly》1996,79(10):349-350
983.
OBJECTIVE: To test the hypothesis that ibuprofen increases the risk of hospitalization for gastrointestinal bleeding, renal failure, or anaphylaxis among febrile children. DESIGN: Randomized double-blind acetaminophen-controlled trial. SETTING: Outpatient pediatric and family medicine practices. PATIENTS: A total of 84,192 children. INTERVENTION: Patients were randomly assigned to receive 12 mg/kg of acetaminophen, 5 mg/kg of ibuprofen, or 10 mg/kg of ibuprofen. MAIN OUTCOME MEASURES: Hospitalizations for acute gastrointestinal bleeding, acute renal failure, and anaphylaxis. RESULTS: A total of 277 patients (0.3%) were unavailable for follow-up. Overall, 795 participants (1%) were hospitalized, primarily for infectious diseases; hospitalization rates did not differ according to treatment group. Four children had diagnoses of acute, nonmajor gastrointestinal bleeding (two in each ibuprofen dosage group); among ibuprofen-treated children, the observed risk of gastrointestinal bleeding, 7.2 per 100,000 (95% confidence interval, 2 to 18 per 100,000), was not significantly different from the risk among acetaminophen-treated children (P = .31). There were no hospitalizations for acute renal failure or anaphylaxis; the upper 95% confidence bound for the risk of either of these outcomes was 5.4 per 100,000 ibuprofen-treated children. Among a number of other possibly serious adverse drug events, low white blood cell count was marginally associated with ibuprofen treatment. Because this association was observed in the setting of multiple comparisons and white blood cell counts may have been low before treatment, causation is unclear. CONCLUSIONS: The risk of hospitalization for gastrointestinal bleeding, renal failure, or anaphylaxis was not increased following short-term use of ibuprofen in children. These data, however, provide no information on the risks of less severe outcomes or the risks of prolonged ibuprofen use. 相似文献
984.
985.
986.
987.
DR Ingrams MS Volk BS Biesman MM Pankratov SM Shapshay 《Canadian Metallurgical Quarterly》1998,108(6):883-886
This experimental study investigates the effect of mitomycin C (MMC) on sinus mucosal healing. MMC has an antiproliferative action on fibroblasts. It is used in glaucoma surgery to prevent restenosis of fistulas. Antrostomies were drilled in rabbit maxillary sinuses. One side was used as a control and the other treated with MMC at a concentration of 0.04, 0.4, or 1 mg/mL. Two animals from each group were sacrificed at 1, 2, 4, and 12 weeks. The antrostomies in the control and 0.04-mg/mL groups had closed by 1 week; in the 0.4-mg/mL group by 4 weeks, and in the 1.0-mg/mL group by 12 weeks. Ciliary function was initially impaired but normalized within 1 week. Both light and scanning electron microscopy showed no permanent damage to the cilia. These results suggest that MMC can be used to delay closure of antrostomies in sinus surgery. 相似文献
988.
HE Greenberg M Scharf W Mendelson JM Cook E Cox SM Scharf 《Canadian Metallurgical Quarterly》1997,60(7):485-492
beta-carboline-3-carboxylate-t-butyl ester (beta CCT) is the most selective antagonist for the alpha 1 beta 2 gamma 2 benzodiazepine (BZ) receptor subtype which blocks anticonvulsant and antipunishment (anxiolytic) but not sedative and myorelaxant effects of diazepam. We sought to determine whether the alpha 1 beta 2 gamma 2 BZ receptor subtype modulates ventilation and whether beta CCT antagonizes respiratory depressant effects of BZ's. Room air (RA) ventilation and the ventilatory response to 6% & 12% CO2 were non-invasively assessed by barometric plethysmography in 30 gm mice, n = 11. Plethysmograph signal amplitude (AMP), respiratory rate (RR) and minute ventilatory effort (MVE = AMP*RR), were measured. Runs were performed pre-drug & after IP injection of saline, vehicle for beta CCT, beta CCT (60mg/kg), midazolam (10mg/kg), and midazolam followed by beta CCT. Compared with pre-drug value, midazolam depressed MVE during RA and CO2 stimulation (% of pre-drug value: RA:57.7 +/- 17.4%, 6% CO2:53.73 +/- 14.3%, 12% CO2:69.1 +/- 26.1%, p < .0001, ANOVA). Subsequent beta CCT partially reversed this depression during RA conditions (72.8 +/- 25.7% of pre-drug value, p < .03 compared with midazolam) and 6% CO2 stimulation (67.1 +/- 10.7% of pre-drug value, p < .006 compared with midazolam) but not with 12% CO2. Thus, the alpha 1 beta 2 gamma 2 BZ receptor subtype modulates ventilation and beta CCT partially antagonizes respiratory depressant effects of BZ's. 相似文献
989.
Generation of constitutively active recombinant caspases-3 and -6 by rearrangement of their subunits 总被引:1,自引:0,他引:1
SM Srinivasula M Ahmad M MacFarlane Z Luo Z Huang T Fernandes-Alnemri ES Alnemri 《Canadian Metallurgical Quarterly》1998,273(17):10107-10111
Caspases play a major role in the transduction of the apoptotic signal and execution of apoptosis in mammalian cells. Ectopic overexpression of the short prodomain caspases-3 and -6 precursors in mammalian cells does not induce apoptosis. This is due to their inability to undergo autocatalytic processing/activation and suggests that they depend on the long prodomain caspases for activation. To investigate directly the apoptotic activity of these two caspases in vivo, we engineered constitutively active recombinant caspases-3 and -6 precursors. This was achieved by making contiguous precursor caspases-3 and -6 molecules, which have their small subunits preceding their large subunits. Unlike their wild type counterparts, these recombinant molecules were capable of autocatalytic processing in an in vitro translation reaction, suggesting that they are catalytically active. They were also capable of autoprocessing and inducing apoptosis in vivo independent of the upstream caspases. Furthermore, their autocatalytic and apoptotic activities were inhibited by the pancaspase inhibitor z-VAD-fluoromethylketone, but not by CrmA or Bcl-2, thus directly demonstrating that the targets of inhibition of apoptosis by CrmA and Bcl-2 are upstream of caspases-3 and -6. Since caspases-3 and -6 are the most downstream executioners of apoptosis, the constitutively active versions of these caspases could be used at very low concentrations in gene therapy model systems to induce apoptosis in target tissues or tumors. 相似文献
990.
WH Yu M Kimura A Walczewska JC Porter SM McCann 《Canadian Metallurgical Quarterly》1998,95(13):7795-7798
Adenosine has been identified in the anterior pituitary gland and is secreted from cultured folliculostellate (FS) cells. To determine whether adenosine controls the secretion of anterior pituitary hormones in vitro, adenosine was incubated with anterior pituitaries. It stimulated prolactin (PRL) release at the lowest concentration used (10(-10) M); the stimulation peaked at 10(-8) M with a threefold increase in release and declined to minimal stimulation at 10(-4) and 10(-3) M. Follicle-stimulating hormone release was maximally inhibited at 10(-8) M, whereas luteinizing hormone release was not significantly inhibited. Two selective A1 adenosine receptor antagonists (10(-7) or 10(-5) M) had no effect on basal PRL release, but either antagonist completely blocked the response to the most effective concentration of adenosine (10(-8) M). In contrast, a highly specific A2 receptor antagonist (10(-7) or 10(-5) M) had no effect on basal PRL release or the stimulation of PRL release induced by adenosine (10(-8) M). We conclude that adenosine acts to stimulate PRL release in vitro by activating A1 receptors. Since the A1 receptors decrease intracellular-free calcium, this would decrease the activation of nitric oxide synthase in the FS cells, resulting in decreased release of nitric oxide (NO). NO inhibits PRL release by activating guanylate cyclase that synthesizes cGMP from GTP; cGMP concentrations increase in the lactotrophs leading to inhibition of PRL release. In the case of adenosine, NO release from the FS cells decreases, resulting in decreased concentrations of NO in the lactotrophs, consequent decreased cGMP formation, and resultant increased PRL release. 相似文献