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941.
Russell G. Smith William F. Reiter Guillaume Vitupier Steven C. Lovejoy 《Canadian Metallurgical Quarterly》2005,10(1):5-11
Stress analysis of the components of a sheave used to transfer loads between the lift span and counterweight in a movable span bridge is investigated. Stress analysis is a requirement for properly designing such sheaves. Modeling of the mechanism of load transfer from the wire ropes to the sheave is accomplished in three ways: (1) the traditional manner using a uniform pressure distribution; (2) using a varying pressure distribution developed from belt/pulley theory; and (3) using the finite-element method with nonlinear contact elements between the wire rope and the sheave. Internal stresses in the sheave are calculated using uniform distributed pressure and a varying pressure distribution. It is determined that the load distribution on the sheave from the wire ropes is precisely the same for the nonlinear contact analysis and the belt/pulley analysis. The internal stress analysis results show that the traditional, uniformly distributed load representation is less conservative than the more realistic belt/pulley load representation. A methodology is developed that can be utilized to more accurately model the load transfer representation without the complexity of nonlinear analyses. 相似文献
942.
Jian Zhi Hu Ja Hun Kwak Zhenguo Yang William Osborn Tippawan Markmaitree Leon L. Shaw 《Journal of power sources》2008,181(1):116-119
Using variable temperature in situ 1H NMR spectroscopy on a mixture of LiNH2 + LiH that was mechanically activated using high-energy ball milling, the dehydrogenation of the LiNH2 + LiH to Li2NH + H2 was investigated. The analysis indicates NH3 release at a temperature as low as 30 °C and rapid reaction between NH3 and LiH at 150 °C. The transition from NH3 release to H2 appearance accompanied by disappearance of NH3 confirms unambiguously the two-step elementary reaction pathway proposed by other workers. 相似文献
943.
William R. Bevier Warren A. Hunt Jr J Strother Moore William D. Young 《Journal of Automated Reasoning》1989,5(4):411-428
The term systems verification refers to the specification and verification of the components of a computing system, including compilers, assemblers, operating systems and hardware. We outline our approach to systems verification, and summarize the application of this approach to several systems components. These components consist of a code generator for a simple high-level language, an assembler and linking loader, a simple operating system kernel, and a microprocessor design. 相似文献
944.
945.
946.
In principle, the version space approach can be applied to any induction problem. However, in some cases the representation language for generalizations is so powerful that (1) some of the update functions for the version space are not effectively computable, and (2) the version space contains infinitely many generalizations. The class of context-free grammars is a simple representation that exhibits these problems. This paper presents an algorithm that solves both problems for this domain. Given a sequence of strings, the algorithm incrementally constructs a data structure that has nearly all the beneficial properties of a version space. The algorithm is fast enough to solve small induction problems completely, and it serves as a framework for biases that permit the solution of larger problems heuristically. The same basic approach may be applied to representations that include context-free grammars as special cases, such as And-Or graphs, production systems, and Horn clauses. 相似文献
947.
When a man loses the ability to be the "breadwinner," what types of conflicts does he experience? More important, how can counselors understand the full depth of his concerns if social class is not explored? However, the extant literature on social class and counseling applications is meager. Hence, the author explains the social class worldview model and modern classism theory as frameworks to understand subjective social class experiences. Although the models are theoretical, the author provides case vignettes to illustrate how clinicians can gather and interpret social class information and integrate it into client profiles and treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
948.
949.
Tantalum diboride (TaB2) was synthesized by reducing Ta2O5 using B4C and graphite at 1600 °C under flowing Ar. The powder had an average particle size of 0.4 μm with both needle-like and rounded particles. The TaB2 powder was hot pressed to relative densities of 97% at 2000 °C (3.6 μm grain size) and 98% at 2100 °C (5.3 μm grain size). Mechanical properties were measured for TaB2 hot pressed at 2100 °C and were comparable to those of the commonly studied diborides, ZrB2 and HfB2. The Young's modulus was 551 GPa, Vickers' hardness was 25.6 GPa, flexure strength was 555 MPa, and fracture toughness was 4.5 MPa-m1/2. 相似文献
950.
Burt S. Alexandra; Krueger Robert F.; McGue Matt; Iacono William G. 《Canadian Metallurgical Quarterly》2001,110(4):516
Research has documented high levels of covariation among childhood externalizing disorders, but the etiology of this covariation is unclear. To unravel the sources of covariation among attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD), the authors studied 11-year-old twins (N/&=/&1,506) from the Minnesota Twin Family Study. Symptom counts for each of these disorders were obtained from interviews administered to the twins and their mothers. A model was fit that allowed the parsing of genetic, shared environmental (factors that make family members similar to each other), and nonshared environmental (factors that make family members different from each other) contributions to covariation. The results revealed that although each disorder was influenced by genetic and environmental factors, a single shared environmental factor made the largest contribution to the covariation among ADHD, ODD, and CD. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献