全文获取类型
收费全文 | 1904篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 26篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 4篇 |
矿业工程 | 1篇 |
轻工业 | 4篇 |
无线电 | 13篇 |
一般工业技术 | 28篇 |
冶金工业 | 1820篇 |
原子能技术 | 1篇 |
自动化技术 | 7篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 1篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 3篇 |
1999年 | 50篇 |
1998年 | 601篇 |
1997年 | 314篇 |
1996年 | 229篇 |
1995年 | 104篇 |
1994年 | 96篇 |
1993年 | 103篇 |
1992年 | 11篇 |
1991年 | 21篇 |
1990年 | 24篇 |
1989年 | 36篇 |
1988年 | 29篇 |
1987年 | 17篇 |
1986年 | 24篇 |
1985年 | 32篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 16篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 34篇 |
1976年 | 70篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有1909条查询结果,搜索用时 15 毫秒
991.
David A. Rider Brian J. Worfolk Kenneth D. Harris Abeed Lalany Kevin Shahbazi Michael D. Fleischauer Michael J. Brett Jillian M. Buriak 《Advanced functional materials》2010,20(15):2404-2415
A cationic and water‐soluble polythiophene [poly[3‐(6‐pyridiniumylhexyl)thiophene bromide] (P3PHT+Br?)] is synthesized and used in combination with anionic poly(3,4‐ethylenedioxythiophene):poly(p‐styrenesulfonate) (PEDOT:PSS)? to produce hybrid coatings on indium tin oxide (ITO). Two coating strategies are established: i) electrostatic layer‐by‐layer assembly with colloidal suspensions of (PEDOT:PSS)?, and ii) modification of an electrochemically prepared (PEDOT:PSS)? film on ITO. The coatings are found to modify the work function of ITO such that it could act as a cathode in inverted 2,5‐diyl‐poly(3‐hexylthiophene) (P3HT)/[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) polymer photovoltaic cells. The interfacial modifier created from the layer‐by‐layer assembly route is used to produce efficient inverted organic photovoltaic devices (power conversion efficiency ~2%) with significant long‐term stability in excess of 500 h. 相似文献
992.
CC Merck 《Canadian Metallurgical Quarterly》1976,4(1):7-18
Dog platelets are refractory to aggregation by arachidonic acid (AA) but generate an unstable activity that aggregates rabbit platelets. Formation of this activity is inhibited by indomethacin, by the peroxide scavenging enzyme catalase, by two chelating agents that bind Cu+ and Cu2+ ions, by the -SH agent dithiothreitol and is stimulated by cysteine. Agitation of dog platelets is followed by spontaneous aggregation and uncovers aggregation by AA, which is blocked by indomethacin. Neither indomethacin nor apyrase prevent spontaneous aggregation, ruling out both activation of prostaglandin synthetase and leakage of ADP as possible explanations. Complexation of plasma Ca2+ by citrate as an explanation for refractoriness to AA was ruled out by replacing citrate with heparin. Dog platelets are also refractory to PGH2 formed from AA by the cyclo oxygenase component of prostaglandin synthetase. Aggregation of rabbit platelets by PGH2 is not inhibited by indomethacin, by catalase, by dithiothreitol or by metal chelating agents and is not potentiated by cysteine. This confirms that the reagents act before PGH2 is formed. Aggregating activity generated by dog platelets is probably due to an unstable lipoperoxide whose generation involves mechanisms similar to those responsible for aggregation of rabbit platelets, since similar antagonists block both processes. 相似文献
993.
AD Brandling-Bennett RS Jackson SB Halstead CC Campbell KL Herrmann JF Modlin JD Meyers JJ Witte 《Canadian Metallurgical Quarterly》1976,130(10):1081-1084
Three years after receiving rubella vaccine, 1,060 elementary school children living on the island of Maui, Hawaii, were revaccinated with either HPV-77 DE-5 or RA 27/3 rubella vaccine given subcutaneously or intranasally in order to compare the effectiveness of these two vaccines in raising antibody titers. RA 27/3 was the more effective booster vaccine, producing fourfold or greater titer rises in 20.1% of recipients, including 80% of children with hemagglutination-inhibiting antibody titers less than or equal to 1:40 at the time of revaccination, intranasal revaccination was not significantly more effective than subcutaneous revaccination, although it did elicit higher titers in children who responded. Responses differed according to the vaccine that children had received three years earlier. Because antibody titers have persisted in vaccinated children, routine administration of a second dose of rubella vaccine is not currently recommended. 相似文献
994.
MR Stein RE Julis CC Peck W Hinshaw JE Sawicki JJ Deller 《Canadian Metallurgical Quarterly》1976,29(9):940-948
Our investigation was designed to retest the hypothesis of the efficacy of human chorionic gonadotropin (HCG) on weight reduction in obese women in a clinic setting. We sought to duplicate the Asher-Harper study (1973) which had found that the combination of 500 cal diet and HCG had a statistically significant benefit over the diet and placebo combination as evidenced by greater weight loss and decrease in hunger. Fifty-one women between the ages of 18 and 60 participated in our 32-day prospective, randomized, double-blind comparison of HCG versus placebo. Each patient was given the same diet (the one prescribed in the Asher-Harper study), was weighed daily Monday through Saturday and was counselled by one of the investigators who administered the injections. Laboratory studies were performed at the time of initial physical examinations and at the end of the study. Twenty of 25 in the HCG and 21 of 26 patients in the placebo groups completed 28 injections. There was no statistically significant difference in the means of the two groups in number of injections received, weight loss, percent of weight loss, hip and waist circumference, weight loss per injections, or in hunger ratings. HCG does not appear to enhance the effectiveness of a rigidly imposed regimen for weight reduction. 相似文献
995.
In four patients with Prinzmetal's variant form of angina, the attack was induced by the combined administration of epinephrine (0.4 to 0.5 mg, given subcutaneously at 7:30 to 8:00 A.M.) and propranolol (40 mg. given orally at 5:00 A.M.). Selective coronary cinearteriography was done before, during, and after the attack with constant monitoring of the ECG and blood pressure. Severe spasm of the right coronary artery occurred at the proximal portion in association with ST-segment elevation in Lead III during the attack and disappeared with the subsidence of the attack in all of them. These results strongly suggest that severe spasm of a large coronary artery mediated by alpha-adrenergic receptors is responsible for the attack of Prinzmetal's variant form of angina. 相似文献
996.
CC Velardo 《Canadian Metallurgical Quarterly》1976,24(10):470-472
The outcome o,f marriages contracted after spinal cord injury suffered by males was examined via the questionnaire method. Of those whose first marriage occurred after their injury, the divorce rate was 24.4%. Of those whose were married prior to injury and then remarried following injury, 16.4% were divorced. If all post-injury marriages are considered, the divorce rate is 23.1%. This is close to the divorce rate of the United States as a whole. The outcome of post-injury marriages was also examined with respect to time since injury, level of injury, presence of post-injury children, and post-injury education and employment. Particular attention was given to those males who had never been married prior to their injury. 相似文献
997.
Some basic fallacies in the computation of the paternity index have been pointed out. The general finding that the true fathers' mean paternity index is greater than that of nonfathers is a necessary consequence of an algebraic identity, having nothing to do with paternity or nonpaternity. It has also been shown that the paternity index is not a likelihood ratio as claimed. The fact that a paternity index may frequently take values less than unity leads to absurd conclusions regarding the probability of paternity. A formula relating prior and posterior probabilities of paternity, based solely on genetic marker testing results (exclusion or nonexclusion), is reiterated as a substitute for the current paternity index. 相似文献
998.
This study evaluated the spectral characteristics of neuronal discharges in the caudal hypoglossal nucleus and their physiological relevance in adult, male Sprague Dawley rats which were anaesthetized and maintained with pentobarbital sodium. Based on auto-spectral analysis of extracellular single-neuron activity, three spectral patterns were identified in the spontaneous discharges of hypoglossal neurons. Neurons that exhibited a rhythmic pattern manifested a concentrated peak in the auto-spectrogram that corresponded to the mean discharge rate. A majority of hypoglossal neurons displayed the modulated pattern, which was manifested either as scattered power densities (wide-band modulated pattern) or with a peak frequency component that was different from the mean discharge rate (narrow-band modulated pattern). Neurons that exhibited a mixed pattern displayed both rhythmic and modulated spectral patterns. Cross-spectral analysis further revealed that respiratory modulation constituted a major physiological influence on caudal hypoglossal neurons. The respiratory modulated pattern, however, could be converted to a mixed pattern in the presence of a central dipsogen, angiotensin III. The results suggest that the spectral patterns of neuronal discharges in caudal hypoglossal neurons represent manifestations of multiple physiological information, including that regarding respiration and dipsogenesis, which is encoded in these neurons. It was also shown that this information may only be revealed by auto-spectral and cross-spectral analysis of neuronal discharge signals. 相似文献
999.
GP Hanley CC Piazza WW Fisher SA Contrucci KA Maglieri 《Canadian Metallurgical Quarterly》1997,30(3):459-473
Functional communication training (FCT) and noncontingent reinforcement (NCR) are commonly prescribed treatments that are based on the results of a functional analysis. Both treatments involve delivery of the reinforcer that is responsible for the maintenance of destructive behavior. One major difference between the two treatment procedures is that client responding determines reinforcement delivery with FCT (e.g., reinforcement of communication is delivered on a fixed-ratio 1 schedule) but not with NCR (e.g., reinforcement is delivered on a fixed-time 30-s schedule). In the current investigation, FCT and NCR were equally effective in reducing 2 participants' destructive behavior that was sensitive to attention as reinforcement. After the treatment analysis, the participants' relative preference for each treatment was evaluated using a modified concurrent-chains procedure. Both participants demonstrated a preference for the FCT procedure. The results are discussed in terms of treatment efficacy and preference for control over when reinforcement is delivered. In addition, a method is demonstrated in which clients with developmental disabilities can participate in selecting treatments that are designed to reduce their destructive behavior. 相似文献
1000.
Retention of replication fidelity by a DNA polymerase functioning in a distantly related environment
The primary structures of the replicative DNA polymerases (gp43s) of bacteriophage T4 and its distant phylogenetic relative RB69 are diverged, retaining only 61% identity and 74% similarity. Nevertheless, RB69 gp43 substitutes effectively for T4 gp43 in T4 DNA replication in vivo. We show here that RB69 gp43 replicates T4 genomes in vivo with a fidelity similar to that achieved by T4 gp43. Furthermore, replication by RB69 gp43 in the distantly related environment does not enhance the mutator activities of mutations in T4 genes that encode other components of the multienzyme DNA replicase. We also show that the fidelities of RB69 gp43 and T4 gp43 are both high in vitro and that they are similarly and sharply reduced in vivo by mutations that eliminate the 3'-exonucleolytic proofreading function. We conclude that gp43 interactions with the other replication proteins are probably nonessential for polymerase fidelity. 相似文献