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131.
132.
在A≈80区奇-奇核旋称反转问题上已提出几种机制,但没有一种理论推断是结论性的.在本工作中将角动量投影壳模型应用到80,82Rb核,对组态为πg9/2⊙νg9/2的正宇称晕带和组态为π(p1/2,p3/2,f5/2)⊙νg9/2 的负宇称晕带理论计算和实验结果进行了比较,特别是对正宇称晕带中的signature反转机制进行了探讨.角动量投影壳模型计算显示正宇称晕带中的signature反转是原子核随自旋增加形状发生变化的信号,其间原子核从低自旋的长椭球变到高自旋的扁椭球.此外,还确定了此两带的原子核形状 相似文献
133.
Stephen J. Elliott 《ETRI Journal》2004,26(6):641-646
As the use of signatures for identification purposes is pervasive in society and has a long history in business, dynamic signature verification (DSV) could be an answer to authenticating a document signed electronically and establishing the identity of that document in a dispute. DSV has the advantage in that traits of the signature can be collected on a digitizer. The research question of this paper is to understand how the individual variables vary across devices. In applied applications, this is important because if the signature variables change across the digitizers this will impact performance and the ability to use those variable. Understanding which traits are consistent across devices will aid dynamic signature algorithm designers to create more robust algorithms. 相似文献
134.
Certificateless signature: a new security model and an improved generic construction 总被引:2,自引:0,他引:2
Bessie C. Hu Duncan S. Wong Zhenfeng Zhang Xiaotie Deng 《Designs, Codes and Cryptography》2007,42(2):109-126
Certificateless cryptography involves a Key Generation Center (KGC) which issues a partial key to a user and the user also
independently generates an additional public/secret key pair in such a way that the KGC who knows only the partial key but
not the additional secret key is not able to do any cryptographic operation on behalf of the user; and a third party who replaces
the public/secret key pair but does not know the partial key cannot do any cryptographic operation as the user either. We
call this attack launched by the third party as the key replacement attack. In ACISP 2004, Yum and Lee proposed a generic
construction of digital signature schemes under the framework of certificateless cryptography. In this paper, we show that
their generic construction is insecure against key replacement attack. In particular, we give some concrete examples to show
that the security requirements of some building blocks they specified are insufficient to support some of their security claims.
We then propose a modification of their scheme and show its security in a new and simplified security model. We show that
our simplified definition and adversarial model not only capture all the distinct features of certificateless signature but
are also more versatile when compared with all the comparable ones. We believe that the model itself is of independent interest.A
conventional certificateless signature scheme only achieves Girault’s Level 2 security. For achieving Level 3 security, that
a conventional signature scheme in Public Key Infrastructure does, we propose an extension to our definition of certificateless
signature scheme and introduce an additional security model for this extension. We show that our generic construction satisfies
Level 3 security after some appropriate and simple modification.
A preliminary version of the extended abstract of partial results appeared in ACISP 2006 [9]. 相似文献
135.
一种改进的椭圆曲线算法及在电子商务中的应用 总被引:4,自引:2,他引:2
徐小平 《微电子学与计算机》2004,21(4):74-77
椭圆曲线公钥密码体制(ECC)具有最高的位安全强度。文章分析了ECC的优势,讨论了椭圆曲线的数学基础和离散对数问题的复杂性,并对现有的ECC数字签名算法(ECDSA)进行了改进,进一步加快了运算速度,缩短了数据传输的时间。将改进的椭圆曲线密码体制应用在电子商务中实现数字签名,取得了较好的效果。 相似文献
136.
一种移动Agent的安全认证方案的设计与实现 总被引:2,自引:0,他引:2
针对移动Agent的安全问题,简要介绍了几种常用的安全认证技术,并在公钥密码体制认证方案的基础上,提出并实现了一种可用于移动Agent和Agent平台之间安全认证的方案。证书采用X.509证书格式,使用RSA和IDEA混合加密的算法,密钥管理采用PGP算法中公私钥环的方式,使该认证方案具有很高的安全性。文中详细说明了方案的实现流程,并深入分析了其安全性。结果表明,采用该方案能有效改善移动Agent的安全性。 相似文献
137.
本文讨论了基于纠错码的公钥体制PEPS2和ECPS3中加密过程的安全性,指出可以在O(n^3)时间内由体制的公开钥信息找到一个转换矩阵,用它也可以解密由秘密置换阵加密的消息,其中n为稳定置换阵的行(列)数,进而,本文给出了用所找到的置换阵破译ECPS2加密和ECPS3部分情况下加密的方法。 相似文献
138.
两种门限签名方案的密码学分析及其改进 总被引:14,自引:0,他引:14
Jan等和Gan分别提出了抗合谋攻击的门限签名方案。给出了一种合谋攻击方案表明他们的方案是不安全的,任何一组成员可以合谋假冒另一组成员对任何消息生成有效的门限签名而不需负任何责任。一旦事后发生纠纷,指定的秘书可以打开签名,而被假冒的成员无法否认签名。为克服他们的方案的安全性缺陷,给出了一个改进方案。并且,基于改进的方案,提出了一个可以追查签名者身份的、抗合谋攻击的门限签名方案。 相似文献
139.
We introduce the notion of signature for relations in mapping class groups and show that the signature of a Lefschetz fibration over the 2-sphere is the sum of the signatures for basic relations contained in its monodromy. Combining explicit calculations of the signature cocycle with a technique of substituting positive relations, we give some new examples of non-holomorphic Lefschetz fibrations of genus and which violate slope bounds for non-hyperelliptic fibrations on algebraic surfaces of general type.
140.
Marten Van Dijk Dwaine Clarke Blaise Gassend G. Edward Suh Srinivas Devadas 《Designs, Codes and Cryptography》2006,39(2):253-273
We present protocols for speeding up fixed-base variable-exponent exponentiation and variable-base fixed-exponent exponentiation
using an untrusted computational resource. In the fixed-base protocols, the exponent may be blinded. In the variable-base
protocols, the base may be blinded. The protocols are described for exponentiation in a cyclic group. We describe how to extend
them to exponentiation modulo an integer where the modulus is the product of primes with single multiplicity. The protocols
provide a speedup of
over the square-and-multiply algorithm, where k is the bitlength of the exponent.
One application of the protocols is to speed up exponentiation-based verification in discrete log-based signature and credential
schemes. The protocols also allow signature verifiers to dynamically choose, for each message, the amount of work it would
like to perform to verify the signature. This results in a work-security tradeoff. We introduce a fifth protocol to perform
variable-base variable- exponent exponentiation, which also has this feature.
Our model allows the trusted resource to perform computations in its idle time. The protocols facilitate the offloading of
work to the offline stage, such that the work the trusted resource performs when it has to do an exponentiation is smaller.
Our protocols are unconditionally secure. 相似文献