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Crossover designs are an extremely useful tool to investigators, and group sequential methods have proven highly proficient at improving the efficiency of parallel group trials. Yet, group sequential methods and crossover designs have rarely been paired together. One possible explanation for this could be the absence of a formal proof of how to strongly control the familywise error rate in the case when multiple comparisons will be made. Here, we provide this proof, valid for any number of initial experimental treatments and any number of stages, when results are analyzed using a linear mixed model. We then establish formulae for the expected sample size and expected number of observations of such a trial, given any choice of stopping boundaries. Finally, utilizing the four-treatment, four-period TOMADO trial as an example, we demonstrate that group sequential methods in this setting could have reduced the trials expected number of observations under the global null hypothesis by over 33%. 相似文献
23.
Xianliang Meng Guifeng Zhang Guoguang Wu Mingqiang Gao Jingzhu Dai 《Chemical Engineering Communications》2020,207(6):861-870
AbstractThe evolution of active groups at low temperature was examined using Chinese lignite by infrared technology and X-ray photoelectron spectroscopy (XPS). The results showed that the hydroxyl, aliphatic ether, methylene, and methyl groups played important roles in the low-temperature oxidation of lignite below 200?°C. Carbonyl and carboxyl groups were important intermediates. Thus, a multi-step evolution mechanism involving the hydroxyl, aliphatic ether groups, and alkane was reasoned to describe the low-temperature oxidation of lignite. In addition, according to the oxidation kinetics experiment and the evolution laws of the active groups, the ratios of the reaction lines were determined considering the accuracy of thermal effects. The thermal effects and the heat release intensities of each temperature interval were obtained based on the evolution mechanism and the reaction ratios. The shortest spontaneous combustion period of lignite was calculated and compared with the experimental value, which proved that the reasoned evolution mechanism of the active groups and the calculations of the thermal effects were reliable. 相似文献
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Fe-2Cu-0.8C powder mixes were prepared by a wet mixing and spray-drying process using iron, copper, graphite and zinc stearate as main raw materials, and stearic acid, alcohol wax and amide wax as binders. The properties of the as-prepared binder treated powder mixes were investigated. The bonding efficiency of the binders was tested by measure the retention of graphite and copper in the powder mixes after dusting resistance test. The test results show that the wet mixing and spray-drying process can realise the bonding of different particles and improve processing properties of the powder mixes. A flow rate of 30.6?s/50?g and an apparent density of 3.18?g/cm3 were obtained for powder mixes with alcohol wax as binder. The results of dusting resistance test demonstrated that alcohol wax and amide wax have better bonding effect for Cu and graphite powders, respectively, which was reflected by the difference value of electronegativity between Fe, Cu, C elements and functional groups. Compared with mechanically mixing powder mixes, using binder treated powder mixes can also reduce the friction coefficient during compaction by 0.012–0.026. The addition of different binders also has a great influence on the properties of sintered parts. 相似文献
26.
为解决共享交通下的共乘用户群体发现效率低、准确率不高问题,依据R-树原理建立GeoOD-Tree索引,并在此基础上提出以最大化共乘率为目标的群体发现策略。首先,对原始时空轨迹数据进行特征提取与标定处理,挖掘有效出行起讫点(OD)轨迹;其次,针对用户起讫点轨迹的特征,建立GeoOD-Tree索引进行有效的存储管理;最后,给出以最大化共乘行程为目标的群体发现模型,并运用K最近邻(KNN)查询对搜索空间剪枝压缩,提高群体发现效率。采用西安市近12000辆出租车营运轨迹数据,选取动态时间规整(DTW)等典型算法与所提算法在查询效率与准确率上进行性能对比分析。与DTW算法相比,所提算法的准确率提高了10.12%,查询效率提高了约15倍。实验结果表明提出的群体发现策略能有效提高共乘用户群体发现的准确率和效率,可有效提升共乘出行方式的出行率。 相似文献
27.
The construction of specialty groups in higher vocational colleges is in full swing. However, due to the cognitive bias and
the lack of construction paradigm for reference, the construction of specialty groups is still in the period of "crossing the river by
feeling the stones" with different opinions. There are some problems in the construction of specialty groups, such as unclear under-
standing of the concept of specialty groups, unreasonable logic of groups, unclear construction of groups, and nonstandard manage-
ment of groups. This paper describes the specific content of the construction of modern information technology specialty group
based on the Sydney Agreement, hoping to form a reference paradigm for the construction of specialty group of similar colleges and
universities. 相似文献
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Medel Manuel L. Zulueta Donala Janreddy Shang-Cheng Hung 《Israel journal of chemistry》2015,55(3-4):347-359
In recent years, there has been rapid expansion of glycan synthesis, fueled by the recognition that the structural complexity of sugars translates to a myriad of biological functions. Such chemical syntheses involve many challenges, mostly due to the regio- and stereochemical aspects of glycosidic bond formation. One-pot strategies were developed to assist in attaining faster and more economical access to the glycan constructs. In this front, achievements in protecting group manipulation, glycosylation, and combinations of these have been reported. Protecting group manipulations in one pot take advantage of the reaction compatibility of commonly used transformations, many of which occur in high regioselectivity. Sequential glycosylations, on the other hand, rely on leaving group orthogonalities and reactivity tuning, as well as the preactivation technique. Altogether, these approaches offer attractive means to the much needed glycan structures and, consequently, help usher in advances in glycoscience. 相似文献