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101.
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Multisensor Fusion: An Autonomous Mobile Robot 总被引:7,自引:0,他引:7
A conventional autonomous mobile robot is introduced. The main idea is the integration of many conventional and sophisticated sensor fusion techniques, introduced by several authors in recent years. We show the actual possibility of integrating all these techniques together, rather than analyzing implementation details. The topics of multisensor fusion, observation integration and sensor coordination are widely used throuhout the article. The final goal is to demonstrate the validity of both mathematical and artificial intelligence techniques in guaranteeing vehicle survival in a dynamic environment, while the robot carries out a specific task. We review conventional techniques for the management of uncertainty while we describe an implementation of a mobile robot which combines on-line heterogeneous sensors in its navigation and localisation tasks. 相似文献
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数据流模型作为一种新型的模型,在许多应用中扮演着重要的角色.基于数据流模型的查询处理技术也得到了广泛的研究.为了提高查询系统的性能,现有的研究成果主要可以划分为两类:调度优化和降低负载方法.调度优化方法通过改变元组执行次序来提高查询性能.降低负载方法在负载超出系统处理能力时,通过减少输入流量来提高吞吐率.然而,同时运用这两种方法来提高查询性能的研究工作还很少.结合共享滑动窗口查询操作的调度优化方法和降低负载方法,提出了两种在burst环境下提高查询吞吐率的策略:均匀降载策略和小窗口准确降载策略.理论分析和实验结果均证明这两种策略能显著提高系统的性能. 相似文献
105.
Wang Z. Das S.K. Che H. Mohan Kumar 《Parallel and Distributed Systems, IEEE Transactions on》2004,15(11):983-995
In the literature, there exit two types of cache consistency maintenance algorithms for mobile computing environments: stateless and stateful. In a stateless approach, the server is unaware of the cache contents at a mobile user (MU). Even though stateless approaches employ simple database management schemes, they lack scalability and ability to support user disconnectedness and mobility. On the other hand, a stateful approach is scalable for large database systems at the cost of nontrivial overhead due to server database management. We propose a novel algorithm, called Scalable Asynchronous Cache Consistency Scheme (SACCS), which inherits the positive features of both stateless and stateful approaches. SACCS provides a weak cache consistency for unreliable communication (e.g., wireless mobile) environments with small stale cache hit probability. It is also a highly scalable algorithm with minimum database management overhead. The properties are accomplished through the use of flag bits at the server cache (SC) and MU cache (MUC), an identifier (ID) in MUC for each entry after its invalidation, and estimated time-to-live (TTL) for each cached entry, as well as rendering of all valid entries of MUC to uncertain state when an MU wakes up. The stale cache hit probability is analyzed and also simulated under the Rayleigh fading model of error-prone wireless channels. Comprehensive simulation results show that the performance of SACCS is superior to those of other existing stateful and stateless algorithms in both single and multicell mobile environments. 相似文献
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远程缓冲区溢出攻击的原理分析与检测 总被引:4,自引:0,他引:4
基于缓冲区溢出的攻击是目前使用相当普遍的一种黑客技术,该文分析了这种攻击的基本原理,在此基础上提出了利用NDIS开发包进行检测的一般方法,并且用实验证实了这种方法的有效性。 相似文献
108.
It is difficult to predict the measurement bias arising from the compliance of the atomic force microscope (AFM) probe. The issue becomes particularly important in this situation where nanometer uncertainties are sought for measurements with dimensional probes composed of flexible carbon nanotubes mounted on AFM cantilevers. We have developed a finite element model for simulating the mechanical behavior of AFM cantilevers with carbon nanotubes attached. Spring constants of both the nanotube and cantilever in two directions are calculated using the finite element method with known Young's moduli of both silicon and multiwall nanotube as input data. Compliance of the nanotube-attached AFM probe tip may be calculated from the set of spring constants. This paper presents static models that together provide a basis to estimate uncertainties in linewidth measurement using nanotubes. In particular, the interaction between a multiwall nanotube tip and a silicon sample is modeled using the Lennard-Jones theory. Snap-in and snap-out of the probe tip in a scanning mode are calculated by integrating the compliance of the probe and the sample-tip interacting force model. Cantilever and probe tip deflections and points of contact are derived for both horizontal scanning of a plateau and vertically scanning of a wall. The finite element method and the Lennard-Jones model provide a means to analyze the interaction of the probe and sample and measurement uncertainty, including actual deflection and the gap between the probe tip and the measured sample surface. 相似文献
109.
Whole-mount immunohistochemistry (whole-mount IH) of the seminiferous tubule is widely used to investigate the self-renewal and differentiation of spermatogonial stem cells (SSCs). Examination of the length of spermatogonial cysts is critical for tracing SSCs lineage by using Whole-mount IH. However, it is difficult for antibody molecules to penetrate into the depth of seminiferous epithelium because its thickness and the tight peritubular myoid and basement membrane outside. Here, we developed a free-floating immunofluorescent procedure of mouse seminiferous tubules using regular incubation time and normal antibody concentration. Microscopic results showed that undifferentiated spermatogonia were positively labeled by promyelocytic leukemia zinc finger protein, E-cadherin, and glial cell line-derived neurotrophic factor family receptor alpha 1, respectively. Spermatogonial cysts in varied length were revealed clearly and spermatogonia subpopulations including A(single) (A(s)), A(paired) (A(pr)), and A(aligned) (A(al)) were distinguished in lower background images. This method provides us an alternate simple way to trace the lineage of individual SSCs and show their three-dimensional locations and distributions within their niches anatomically in next step. 相似文献
110.