全文获取类型
收费全文 | 94650篇 |
免费 | 10650篇 |
国内免费 | 6628篇 |
专业分类
电工技术 | 8211篇 |
综合类 | 9488篇 |
化学工业 | 11104篇 |
金属工艺 | 6109篇 |
机械仪表 | 5888篇 |
建筑科学 | 6213篇 |
矿业工程 | 3921篇 |
能源动力 | 2542篇 |
轻工业 | 10831篇 |
水利工程 | 3039篇 |
石油天然气 | 3180篇 |
武器工业 | 1581篇 |
无线电 | 8197篇 |
一般工业技术 | 7109篇 |
冶金工业 | 11177篇 |
原子能技术 | 1440篇 |
自动化技术 | 11898篇 |
出版年
2024年 | 639篇 |
2023年 | 1598篇 |
2022年 | 3688篇 |
2021年 | 4667篇 |
2020年 | 3361篇 |
2019年 | 2274篇 |
2018年 | 2472篇 |
2017年 | 2815篇 |
2016年 | 2585篇 |
2015年 | 4065篇 |
2014年 | 4991篇 |
2013年 | 5932篇 |
2012年 | 7422篇 |
2011年 | 7685篇 |
2010年 | 7341篇 |
2009年 | 6707篇 |
2008年 | 6801篇 |
2007年 | 6658篇 |
2006年 | 5675篇 |
2005年 | 4399篇 |
2004年 | 3249篇 |
2003年 | 2226篇 |
2002年 | 1970篇 |
2001年 | 1818篇 |
2000年 | 1487篇 |
1999年 | 780篇 |
1998年 | 2765篇 |
1997年 | 1601篇 |
1996年 | 1046篇 |
1995年 | 618篇 |
1994年 | 517篇 |
1993年 | 565篇 |
1992年 | 125篇 |
1991年 | 118篇 |
1990年 | 125篇 |
1989年 | 116篇 |
1988年 | 94篇 |
1987年 | 81篇 |
1986年 | 75篇 |
1985年 | 53篇 |
1983年 | 17篇 |
1982年 | 39篇 |
1981年 | 41篇 |
1980年 | 72篇 |
1979年 | 19篇 |
1977年 | 158篇 |
1976年 | 283篇 |
1975年 | 13篇 |
1959年 | 36篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
空心微珠改性硬质聚氯乙烯复合材料的应用研究 总被引:13,自引:1,他引:12
经过改性的超细空心微珠可以作为填料加入到硬质聚氯乙烯(PVC-U)树脂中,同时改善PVC树脂的流变性、冲击性能和刚性等性能。研究结果表明,超细空心微珠加入到硬质PVC管材中,可以明显改善PVC硬管的加工流动性能,显著缩短塑化时间,降低最大扭矩。而超细空民微珠加入到硬质PVC板材时,可以提高PVC硬板的冲击性能,减小制品的收缩率,赋予PVC硬板优异的耐腐蚀性能,且产品的各项性能均符合PVC板材国家标准GB/T4454-96。 相似文献
105.
106.
107.
马丽霞 《东北电力学院学报》2002,22(1):62-64
论述了某厂一级除盐系统阳床工艺特性及调整试验过程,对存在问题进行分析并改进,得到了实际运行最佳方式和参数,取得良好效果。 相似文献
108.
C Aufricht A Balbisi C Gerdov T Müller MA Lothaller E Balzar 《Canadian Metallurgical Quarterly》1995,207(2):59-62
A 10-year-old German shepherd dog presented with a periodontal 10 mm interproximal defect between the left mandibular fourth premolar and first molar teeth. Bone graft removed from the caudoventral portion of the ipsilateral hemimandible was placed in the defect as a component of the periodontal treatment plan. The use of bone graft likely contributed to periodontal pocket reduction. 相似文献
109.
J Pet?j? K Peltola H Sairanen M Leijala R Kekom?ki E Vahtera MA Siimes 《Canadian Metallurgical Quarterly》1996,112(3):665-671
Fibrinolysis and coagulation were studied in 10 neonates undergoing cardiac operations for congenital heart defects. Coagulation was activated during cardiopulmonary bypass as evidenced by highly increased prothrombin fragment 1 + 2 levels compared with preoperative values. Prothrombin fragment 1 + 2 levels remained elevated until postoperative day 3. Unlike coagulation, fibrinolysis was not activated during cardiopulmonary bypass but did show late activation on postoperative day 3, as evidenced by elevated levels of the fibrin degradation product D-dimer. Lack of fibrinolytic activation during bypass and its appearance on postoperative day 3 were partly explained by changes observed in tissue plasminogen activator and its inhibitor. During bypass, levels of tissue plasminogen activator and its inhibitor increased by 3.4-fold and 3.2-fold, respectively. In the postoperative period, levels of plasminogen activator inhibitor normalized rapidly whereas tissue plasminogen activator remained elevated, resulting in late fibrinolytic activation on postoperative day 3. In accordance with elevated prothrombin fragment 1 + 2, platelet count, antithrombin III, protein C, prothrombin, and factor VII were decreased on postoperative day 2, indicating ongoing consumptive coagulopathy. Nine patients had antithrombin III and six had protein C levels below age-specific normal ranges, consistent with an acquired deficiency state. Three had central venous thrombosis by postoperative day 4 or 5. In all three, thrombosis was preceded by antithrombin III deficiency, protein C deficiency, and highly elevated plasminogen activator inhibitor (3.7 to 37 times the mean of the other patients) on postoperative days 1 to 3. In conclusion, cardiopulmonary bypass in neonates caused rapid and profound alterations in the coagulation and fibrinolytic systems and initiated consumptive coagulopathy lasting until at least postoperative day 3. Thrombophilic abnormalities in antithrombin III, protein C, and fibrinolysis were frequently found and were associated with serious thrombotic complications. 相似文献
110.
A competitive enzyme-linked immunoadsorbent assay (ELISA) technique has been developed to facilitate quantitative analysis of the earliest step in the initiation of the extrinsic pathway of coagulation, i.e., complex formation of factor VII/VIIa with tissue factor. The ELISA measures the binding of biotinylated human plasma factor VII to relipidated recombinant human tissue factor. Quantitation of the relative affinity (expressed as IC50) of any factor VII molecular population or structural analogue for tissue factor can be determined by competitive binding. Subnanomolar concentrations of both wild-type recombinant human factor VII (rFVII) and rFVII(R152Q), a mutation at the FVII activation site, competed effectively with biotinylated plasma-derived factor VII in binding to tissue factor. In contrast, the affinity of rFVII(R79Q), a mutation in the first epidermal growth factor-like domain, was 12-fold lower. Following activation of rFVII(R79Q), its affinity for tissue factor and enzymatic activity increased 4-fold and 6-fold, respectively. For wild-type rFVII, enzymatic activity rose significantly following activation. However, its affinity for tissue factor was unchanged. We conclude that both the activation state of factor VII and the mutation of amino-acid residues within the first epidermal growth factor-like domain may alter the affinity of factor VII for tissue factor. 相似文献