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961.
Plant growth and crop yield can be significantly impeded by a number of soil physical parameters including soil water content, mechanical strength and soil electrical conductivity (EC). Therefore, to simultaneously measure these physical parameters along vertical depths in the field, it has been desired for many years. This study focused on developing a multi-sensor system, which contained a cell with three sensors for measuring soil water content, mechanical strength and EC. Additionally a Hall-current sensor was proposed to measure the operating current of a dc-motor, which generated the penetrating force during operating process. Based on the theoretical analysis of the transformation from electrical to mechanical energy, it was feasible to evaluate the soil mechanical strength from the operating current of the dc-motor. In order to verify the performance of the designed system and the theoretical analysis addressed, relevant calibrations and tests were conducted. The results demonstrate that the multi-sensor system could be beneficial and practical for field surveys. 相似文献
962.
Bente Foereid G. T. Barthram Carol A. Marriott 《Nutrient Cycling in Agroecosystems》2007,77(2):143-153
Extensive agricultural systems have been promoted all over Europe. Most studies of such systems have focused on plant species
composition, while few studies have looked at soil effects. We report on an experiment at three upland sites where soil carbon,
nitrogen and pH were measured twice a year for 12 years. There were four grazing treatments: no grazing, grazed to maintain
a sward height of 8 cm, grazed to maintain 4 cm (all without fertiliser) and grazed to maintain 4 cm with the addition of
fertiliser. There was no significant effect of treatment, but there were differences between sites over time. A simulation
model, CENTURY, was adapted to the data. It also predicted little difference between treatments, but the fit to data was not
very good. It was necessary to assume that the soils contained a store of undecomposed organic matter or peat that was now
slowly decomposing as a result of liming. The need to modify the model to include a pH effect on decomposition in the model
is highlighted. 相似文献
963.
拟启动压力对低渗透单相流体及油水两相渗流的影响——以沙埝油田沙7断块为例 总被引:1,自引:1,他引:0
应用压差-流量法测定岩心启动压力,根据实验结果和数学方法分析启动压力对油水渗流的影响,并对达西公式和JBN计算方法进行改进,推导出适合低渗透储层规律的公式.研究结果表明,由于启动压力的存在,低渗透油藏油水渗流非达西现象突出,借用达西公式所获得的视渗透率随压力梯度发生变化,当压力梯度达到最大启动压力梯度时,渗流进入拟线性流阶段. 相似文献
964.
Soil moisture is an important state variable connecting the land surface-atmosphere system, and its information can be efficiently acquired by the new technique of microwave remote sensing. Accurate interpretation of the microwave soil moisture products qualities and in-depth understanding of their temporal and spatial distributions are important prerequisites for their successful application in earth science through data assimilation. In this study, three microwave soil moisture products, FengYun-3C(FY-3C), Soil Moisture Active Passive (SMAP) and Advanced Scatterometer(ASCAT), were evaluated over China based on the triple collocation (TC) method. The abilities of three products to obtain temporal and spatial variations of soil moisture were illustrated by Hovm?ller diagram. The results show that: (1) SMAP generally outperforms ASCAT and FY-3C, with highest TC-based signal-to-noise ratio(SNR) under different land use types. The TC-based SNRs are 1.668dB, -0.316dB and -2.182dB for SMAP, ASCAT and FY-3C respectively; and their correlation coefficients with ground observations are 0.514, 0.501 and 0.209, respectively. (2) The accuracies of FY-3C and ASCAT in Northwest China are overall higher than those in the southern China. All three products can capture the latitudinal and longitudinal gradients of soil moisture, whereas their seasonal fluctuations are higher than those of in-situ measurements. Among three products, FY-3C shows highest spatial gradient and strongest seasonal fluctuations. (3) FY-3C product performance is more susceptible to vegetation coverage than ASCAT and SMAP, but it outperforms ASCAT in barren areas. The results of our study could provide useful insights for assimilating microwave soil moisture products into land surface models to improve hydrological prediction. 相似文献
965.
Cluster analysis is a statistical method for grouping similar mathematical data sets and is used herein for delineating geostratigraphy from piezocone penetration test data. In terms of site characterization, clustering is an improvement over other statistical methods because no preliminary estimation of the inherent groups within the analyzed data is needed, and no overlapping is permitted between identified clusters. Clustering can accommodate single or multivariables and no data filtering is required. Its application to defining stratigraphic interfaces is illustrated using five case studies with layered profiles. Clustering is able to detect major changes within the stratigraphy not apparent by visually examining the trends of piezocone data or by available cone soil classification methods. 相似文献
966.
967.
哈萨克斯坦盐下油藏双重介质三维地质建模 总被引:11,自引:7,他引:4
以哈萨克斯坦肯基亚克盐下石炭系油藏为例.在详细岩心观察基础上.综合取心、测井、地质、地震等多方面资料,分步建立了双重介质储集层的三维地质模型.首先建立研究区构造模型,利用地震相和测井相分析建立沉积相模型,在数据结构分析和方法优选的基础上.建立相控的储集层基质属性模型;第二步利用地震几何属性分析和岩心裂缝描述结果.模拟建立裂缝分布网络模型;第三步将基质属性和裂缝分布网络模型有机结合,利用基质和裂缝渗流交换原理建立双重介质储集层三维综合地质模型.建模最终给出了裂缝的网络分布模型,裂缝的等效渗透率和双重介质等效渗透率模型,可直接提供给油藏工程研究人员开展数值模拟研究. 相似文献
968.
969.
Claire Bourlieu Mariana Ferreira Bruno Barea Valérie Guillard Pierre Villeneuve Stéphane Guilbert Nathalie Gontard 《European Journal of Lipid Science and Technology》2009,111(5):489-498
Four acetostearin products with increasing acetylation degree were synthesized by chemical interesterification followed by fractionation/blending stages. Their physical properties and functional barrier properties were studied and compared to the properties of technical tristearin. Increasing acetylation degree (AD) modified the triacylglycerols crystal habits and probably led to an increase in acyl chain fluidity, which induced, at macroscopic levels, a decrease in solid fat content (SFC), in melting point, in surface and bulk material hydrophobicity, and an increased moisture effective diffusivity. Water vapor permeability (WVP) coefficients of the materials were partially influenced by the AD factor, but also by the development of macroscopic cracks in lipids presenting high SFC. Acetylated stearin up to 47% (acetyl mol/mol of esterified chain) presented the lowest WVP at 20 °C resulting from an adequate balance between hydrophobicity and mechanical properties of the material. 相似文献
970.