全文获取类型
收费全文 | 363816篇 |
免费 | 30042篇 |
国内免费 | 18484篇 |
学科分类
工业技术 | 412342篇 |
出版年
2024年 | 1118篇 |
2023年 | 3642篇 |
2022年 | 6910篇 |
2021年 | 8178篇 |
2020年 | 8912篇 |
2019年 | 7454篇 |
2018年 | 7152篇 |
2017年 | 8928篇 |
2016年 | 10427篇 |
2015年 | 11674篇 |
2014年 | 21471篇 |
2013年 | 19144篇 |
2012年 | 24495篇 |
2011年 | 26084篇 |
2010年 | 20556篇 |
2009年 | 21472篇 |
2008年 | 20115篇 |
2007年 | 25909篇 |
2006年 | 24720篇 |
2005年 | 21118篇 |
2004年 | 17956篇 |
2003年 | 16094篇 |
2002年 | 13236篇 |
2001年 | 11274篇 |
2000年 | 9410篇 |
1999年 | 7527篇 |
1998年 | 5668篇 |
1997年 | 4921篇 |
1996年 | 4484篇 |
1995年 | 3830篇 |
1994年 | 3409篇 |
1993年 | 2520篇 |
1992年 | 2219篇 |
1991年 | 1648篇 |
1990年 | 1447篇 |
1989年 | 1248篇 |
1988年 | 988篇 |
1987年 | 680篇 |
1986年 | 504篇 |
1985年 | 508篇 |
1984年 | 585篇 |
1983年 | 520篇 |
1982年 | 424篇 |
1981年 | 464篇 |
1980年 | 255篇 |
1979年 | 152篇 |
1978年 | 96篇 |
1977年 | 86篇 |
1976年 | 70篇 |
1975年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
2.
3.
4.
《Planning》2015,(1)
目的 探讨气管上段腺样囊性癌的临床病理特征及诊断和鉴别诊断要点。方法 收集2000年1月至2014年2月在北京协和医院确诊的4例气管上段腺样囊性癌病例,通过光镜、免疫组织化学及组织化学染色分析其临床病理特征、免疫组织化学特点、诊断及鉴别诊断要点。结果 4例气管上段腺样囊性癌患者中,男1例,女3例,平均年龄47岁(38~57岁);既往均无腺样囊性癌病史,1例患者既往有结节性甲状腺肿手术史。镜下检查4例均为筛状/管状型腺样囊性癌,3例累及甲状腺组织,3例累及神经组织,未见淋巴结受累。免疫组织化学染色示4例P16、CD117、BCL2、P63、SMA均阳性,Ki67指数平均8%,TTF1和P53均阴性;4例中基底膜样物胶原Ⅳ阳性;组织化学染色示AB/PAS阳性。术后均接受总剂量为48~56 Gy的放疗,随访6~120个月,平均72.5个月,1例术后96个月复发,3例随访期间无复发及转移。结论 气管上段腺样囊性癌是罕见的原发于气管的低度恶性肿瘤,肿瘤生长缓慢,就诊时多数已侵及甲状腺组织,需要与原发于甲状腺的恶性肿瘤相鉴别,特别是在甲状腺穿刺及术中冰冻检查时。结合电子喉气管镜下表现、典型的形态学及免疫组织化学和组织化学染色有助于准确诊断。手术难以切除干净,术后放疗对延缓疾病复发有一定帮助。 相似文献
5.
6.
Temperature history can have a significant effect on the strength of water-saturated chalk.In this study,hydrostatic stress cycles are applied to understand the mechanical response of chalk samples exposed to temperature cycling between each stress cycle,compared to the samples tested at a constant temperature.The total accumulated strain during a stress cycle and the irreversible strain are reported.Chalk samples from Kansas(USA)and Mons(Belgium),with different degrees of induration(i.e.amount of contact cementation),were used.The samples were saturated with equilibrated water(polar)and nonpolar Isopar H oil to quantify water weakening.All samples tested during 10 stress cycles with varying temperature(i.e.temperature cycled in between each stress cycle)accumulated more strain than those tested at constant temperatures.All the stress cycles were performed at 30℃.The two chalk types behaved similarly when saturated with Isopar H oil,but differently when saturated with water.When saturated with water,the stronger Kansas chalk accumulated more total strain and more irreversible strain within each stress cycle than the weaker Mons chalk. 相似文献
7.
In this paper, we study scheduling games under mixed coordination mechanisms on hierarchical machines. The two scheduling policies involved are ‐ and ‐, where ‐ (resp., ‐) policy sequences jobs in nondecreasing order of their hierarchies, and jobs of the same hierarchy in nonincreasing (resp., nondecreasing) order of their processing times. We first show the existence of a Nash equilibrium. Then we present the price of anarchy and the price of stability for the games with social costs of minimizing the makespan and maximizing the minimum machine load. All the bounds given in this paper are tight. 相似文献
8.
The synthesis of BaMgAl10O17∶ Eu2 (BAM) phosphors using the sol-gel method and their luminescence properties were reported. The blue-light emitting BAM was synthesized using citric acid and ethylene glycol as chelating materials. Emission of blue-light was obtained from these phosphors. The luminescent intensity increases as the temperature of heat treatment is increased. This study investigated the effects of the molar ratio of ethylene glycol to citric acid (Φ value), with respect to the phase formation and luminescence properties of BAM. The variation of the Φ value resulted in the change of the sol-gel reaction mechanism and the microstructures of the resultant powders. An increase in Φ value leads to an increase in the rate of BAM phase formation. The photoluminescent intensity of the prepared phosphors increases with heating temperatures because of enhanced crystallization. 相似文献
9.
通过对接轨站设置位置和布置图型主要影响因素的分析。按照能够充分反映接轨站作业特点的交接方式。对接轨站所采用的布置图型进行了归纳和分类。 相似文献
10.