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Previous studies have indicated that milrinone, a specific type III phosphodiesterase inhibitor, may be able to induce chloride secretion in cystic fibrosis (CF) tissues. We have now assessed the effect of this agent in vivo on the nasal epithelium of CF mutant mice and also in the nose and lungs of human subjects with CF. Wild-type mice showed a small hyperpolarization of the nasal potential difference (PD) in response to milrinone (100 microM, 1.6 +/- 0.6 mV, n = 8, P < 0.05). In contrast, CF mice carrying either the most common human mutation of the gene for the CF transmembrane regulator (CFTR), DeltaF508 (protein mislocalized), or the G551D mutation (protein normally localized) failed to demonstrate this response. Milrinone perfused alone had no significant effect on the baseline nasal PD of human subjects without CF (14.7 +/- 4.0 mV preperfusion; 15.3 +/- 4.6 mV postperfusion), but significantly (P < 0.05) augmented the hyperpolarization induced by a subsequently perfused low-chloride solution (with milrinone, 36.8 +/- 3.0 mV, n = 6; without milrinone, 18.1 +/- 2.2 mV, n = 19). In contrast, in human subjects with CF (n = 6), milrinone alone significantly (P < 0. 05) altered the nasal baseline PD (52.2 +/- 3.3 mV preperfusion; 57. 4 +/- 4.2 mV, postperfusion) but not the subsequent responses to the low-chloride solution (with milrinone, 1.1 +/- 2.2 mV, n = 4; without milrinone, 0.6 +/- 0.5 mV, n = 28) or to isoproterenol (100 microM). In a separate study in subjects (n = 6) with the DeltaF508 mutation, nasal coadministration of milrinone with isoproterenol produced no effect in the presence of amiloride and a low-chloride solution (-0.8 +/- 0.5 mV). This was also the case in the nasal epithelium of CF subjects (n = 4) carrying at least one G551D allele (-0.3 +/- 0.8 mV). Similarly, milrinone did not hyperpolarize the PD of either the tracheal (n = 6) or segmental (n = 6) airways of CF subjects (DeltaF508) when applied topically in vivo in the presence of amiloride, isoproterenol, or adenosine triphosphate (all 100 microM) in a low-chloride solution. These data do not support the use of milrinone to induce chloride secretion in CF airways in vivo. 相似文献
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The secure and reliable group communication gains popularity in imbalanced mobile networks due to the increase demand of the group-oriented applications such as teleconferences, collaborative workspaces, etc. For acquiring the group security objectives, many authenticated group key agreement (AGKA) protocols exploiting the public key infrastructure have been proposed, which require additional processing and storage space for validation of the public keys and the certificates. In addition, the most of the AGKA protocols are implemented using bilinear pairing and a map-to-point (MTP) hash function. The relative computation cost of the bilinear pairing is approximately two to three times more than the elliptic curve point multiplication (ECPM) and the MTP function has higher computation cost than an ECPM. Due to the limitation of communication bandwidth, computation ability, and storage space of the low-power mobile devices, these protocols are not suitable especially for insecure imbalanced mobile networks. To cope with the aforementioned problems, in this paper, we proposed a pairing-free identity-based authenticated group key agreement protocol using elliptic curve cryptosystem. It is found that the proposed protocol, compared with the related protocols, not only improves the computational efficiencies, but also enhances the security features. 相似文献
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Design and analysis of an improved smartcard‐based remote user password authentication scheme 下载免费PDF全文
SK Hafizul Islam 《International Journal of Communication Systems》2016,29(11):1708-1719
With the fast development of the Internet and the telecommunication technologies, internet users are carrying out various electronic transactions over internet by means of the authentication protocols. To ensure efficient and robust online transaction, security of authentication protocol turns out to be a great concern nowadays. As a result, smartcard‐based password authentication and session key agreement scheme receives significant attention in recent years. In the literature, various authentication schemes have been proposed by the cryptographic research community. Recently, Li et al. analyze some security weaknesses of the authentication scheme of Chen et al. and propose an enhancement based on the discrete logarithm problem and computational Diffie–Hellman problem. This paper further cryptanalyzes the scheme of Li et al. and identifies various security loopholes and then constructs a modified authentication scheme as a remedy. The security and efficiency evaluations demonstrate that our scheme has more security features and low computation costs than the related schemes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Cerebrospinal fluid creatine phosphokinase in the normal dog 总被引:1,自引:0,他引:1
Sixty-seven cerebrospinal fluid samples obtained from 44 healthy dogs were assayed for creatine phosphokinase enzyme activity. All samples contained 1 Sigma unit or less of creatine phosphokinase. Temporal variability within individuals was minimal. The biological characteristics and potential use of this enzyme in neurologic disease are discussed. 相似文献
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LK Bogush IA Zharakhovich MM Shmelev NE Kubrik SK Rasshivalov 《Canadian Metallurgical Quarterly》1976,71(1):89-93
The single nephron glomerular filtration rate (SNGFR) was determined in superficial (S) and juxtamedullary (JM) nephrons of 10 anesthetized rabbits by the 14C ferrocyanide infusion technique. The length of the proximal tubules and the volume of the glomeruli were also determined for the same nephrons. SNGFR was higher in JM than in S: 28.6 +/- 3.4 versus 22.6 +/- 3.0 nl/min, P less than 0.001. In JM nephrons, glomeruli were larger than in S: 1.3 +/- 0.1 versus 0.9 +/- 0.1 nl, P less than 0.001, whereas there was no difference between proximal tubule length in either category (s, 8.7 +/- 0.3 and JM, 8.9 +/- 0.5 mm). In 6 out of 8 animals, SNGFR was significantly correlated to glomerular volume. Lack of correlation was observed between SNGFR and length of proximal tubule in all animals but one. These results show that the rabbit, as well as small rodents and the dog, has a higher SNGFR in juxtamedullary than superficial glomeruli. Although this functional difference is not related to the length of the proximal tubule in each individual animal, the ratio between the mean SNGFR value and the mean length of the proximal tubule in superficial rabbit nephrons is similar to the ratio found in other species. 相似文献