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151.
压力敏感性材料球形孔洞动态扩展问题 总被引:1,自引:1,他引:0
为进一步研究岩土材料爆炸场的特点,采用椭圆型屈服准则和自相似假设,并结合Hopkins三区模型,研究幂硬化材料球形孔洞动态扩展问题.通过对弹性区的研究得出弹性区应力的分布和弹塑性交界处的连续条件;然后在塑性区给出一个求解动态扩展问题的非线性微分方程组;最后通过打靶法数值求解该非线性微分方程组,给出满足边界条件的数值解,并讨论材料参数对场量的影响.结果表明,椭圆型屈服准则能很好地描述压力敏感性材料中孔洞的动态扩展. 相似文献
152.
丛枝菌根(AM)对水稻生长促进及化肥减量研究 总被引:5,自引:2,他引:3
为了考察丛枝菌根(Arbuscular Mycorrhiza,AM)对水稻生长促进及化肥减量效果,以摩西球囊霉(Glomus mosseae)为实验材料在不同丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)含量的基质中进行水稻盆栽试验.对比分析了水稻根部AMF的侵染状况,及其对水稻生长的促进作用,并在此基础上探讨了AMF强化在农业面源污染化肥减量中的作用.结果表明:自然基质中土著G.mosseae普遍存在,并可与水稻根系形成菌根结构,但其对水稻的影响与AMF空白基质相比差异并不显著.AMF强化能显著提高其对水稻根部的侵染率.与自然基质相比,AMF强化使水稻的株高、总生物量、根系总表面积及产量分别提高了20.6%、30%、36.6%、45.3%.经计算,每生产100kg水稻,AMF强化相对于自然条件下氮肥、磷肥、钾肥施用量分别减少3.14kg、1.88kg、2.42kg,削减程度高达47%.AMF强化能够有效促进水稻生长并提高其产量,而且在农业面源污染化肥减量方面具有重要作用. 相似文献
153.
GUAN Ping LIU ChangChun & Lü HeXiang College of Architectural Engineering Dalian University Dalian China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 《中国科学E辑(英文版)》2009,52(5):1248-1253
The traditional unified viscoplasticity constitutive model can be only applied to metal materials. The study of the unified
constitutive theory for metal materials has discovered the correlation between the classical plasticity theory and the unified
viscoplasticity constitutive model, thus leading to the concepts of the classic plastic potential and yield surface in the
unified constitutive model. Moreover, this research has given the continuous expression of the classical plastic multiplier
and presented the corresponding constructive method, which extends its physical significance and lays down a good foundation
for the application of the unified constitutive theory to the material analysis in more fields. This paper also introduces
the unified constitutive model for metal materials and geo-materials. The numerical simulation indicates that the construction
should be both reasonable and practical.
Supported by the National Natural Science Foundation of China (Grant No. 90410012) 相似文献
154.
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157.
The phosphate sorption isotherms are needed to explain differential plant responses to P fertilization in soils. Laboratory and greenhouse experiments investigated the use of phosphorus sorption isotherms in relation to P fertilizer requirement of wheat in ten benchmark soils of Punjab, India. The modified Mitscherlich Equation (3) was used to describe plant response observed in different soils. Maximum obtainable yield (MOY) ranged from 11.6 g pot–1 in Gurdaspur (I) sandy clay loam to 7.0 g pot–1 in Nabha sandy clay loam. Response to P applied @ 25 mg P kg–1 soil was maximum (77%) in Bathinda sand and minimum in Chuharpur clay loam (33%). The response curvature varied from 3.74 × 10–2 in Nabha sandy clay loam to 4.43 × 10–2 in Kanjli sandy loam. The soil solution P required to produce optimum yield (90% MOY) varied from 1.61 µg ml–1 in Bathinda sand to 0.10 µg ml–1 in Sadhugarh clay. Dry matter yield obtained at 0.2 µg ml–1 solution P concentration ranged from 55% in Bathinda sand to 85% of MOY in Gurdaspur (II) clay loam. At the same solution P concentration (0.1 µg P ml–1), dry matter yield was 91% in Sadhugarh clay, 80% in Gurdaspur (II) clay loam and, 43% of MOY in Bathinda sand and eventually coincided with the decreasing maximum buffer capacity (MBC) in these soils. At the same level of sorbed P (100 mg P kg–1 soil) the yield was observed to be inversely proportional to MBC. The study, therefore, concludes that, soils should be grouped according to their P sorption characteristics and MBC before using critical soil solution P as a criterion for obtaining optimum yields. 相似文献
158.
Five phenolic compounds produced by decomposing rice straw and sterile extracts of decomposing rice straw in soil were very inhibitory to growth of three strains ofRhizobium. The effects were additive and in several instances synergistic. The phenolic compounds also reduced nodule numbers and hemoglobin content of the nodules in two bean (Phaseolus vulgaris) varieties. Extracts of decomposing rice straw in soil (same concentration as in the soil) significantly reduced N2 fixation (acetylene reduction) in Bush Black Seeded beans. This may explain in part the great reduction in soybean yields in Taiwan following rice crops when the rice stubble is left in the field. 相似文献
159.
In situ esterifications of high-acidity rice bran oil with methanol and ethanol and with sulfuric acid as catalyst were investigated.
In the esterification with methanol, all free fatty acids (FFA) dissolved in methanol were interesterified within 15 min,
and it was possible to obtain nearly pure methyl esters. The amount of methyl esters obtained from a given rice bran was dependent
on the FFA content of the rice bran oil. In the esterification with ethanol, it was not possible to obtain pure esters as
in methanol esterification, because the solubilities of oil components in ethanol were much higher than those in methanol. 相似文献
160.
亚硫酸盐―甲醛―蒽醌(SFP-AQ)法是适合于草类原料的一种制浆方法。文章研究了氧脱木质素对稻草SFP浆的卡伯值、白度、粘度及强度性能的影响。结果表明,较高的用碱量有助于残余木质素的脱除,在合适的工艺条件下,稻草SFP浆单段氧脱木质素的脱木质素率可达50%以上。在氧脱木质素用碱量3.5%、氧压0.4 MPa、温度110℃、时间60 min或90 min的条件下,稻草SFP浆的卡伯值较低、白度较高,而同时具有良好的粘度和强度性能。 相似文献