全文获取类型
收费全文 | 254096篇 |
免费 | 22389篇 |
国内免费 | 15029篇 |
专业分类
电工技术 | 38754篇 |
技术理论 | 23篇 |
综合类 | 28925篇 |
化学工业 | 12952篇 |
金属工艺 | 10549篇 |
机械仪表 | 20734篇 |
建筑科学 | 21214篇 |
矿业工程 | 10386篇 |
能源动力 | 9705篇 |
轻工业 | 5724篇 |
水利工程 | 7807篇 |
石油天然气 | 11411篇 |
武器工业 | 4386篇 |
无线电 | 26399篇 |
一般工业技术 | 15664篇 |
冶金工业 | 8046篇 |
原子能技术 | 2982篇 |
自动化技术 | 55853篇 |
出版年
2024年 | 343篇 |
2023年 | 2451篇 |
2022年 | 4590篇 |
2021年 | 5986篇 |
2020年 | 6443篇 |
2019年 | 4718篇 |
2018年 | 4079篇 |
2017年 | 6061篇 |
2016年 | 6948篇 |
2015年 | 8229篇 |
2014年 | 15602篇 |
2013年 | 13526篇 |
2012年 | 18913篇 |
2011年 | 20186篇 |
2010年 | 15201篇 |
2009年 | 15296篇 |
2008年 | 15386篇 |
2007年 | 19784篇 |
2006年 | 17912篇 |
2005年 | 15902篇 |
2004年 | 13103篇 |
2003年 | 11851篇 |
2002年 | 9072篇 |
2001年 | 7582篇 |
2000年 | 6359篇 |
1999年 | 5178篇 |
1998年 | 3883篇 |
1997年 | 3197篇 |
1996年 | 2892篇 |
1995年 | 2439篇 |
1994年 | 2033篇 |
1993年 | 1376篇 |
1992年 | 1149篇 |
1991年 | 841篇 |
1990年 | 704篇 |
1989年 | 616篇 |
1988年 | 413篇 |
1987年 | 227篇 |
1986年 | 138篇 |
1985年 | 143篇 |
1984年 | 131篇 |
1983年 | 105篇 |
1982年 | 86篇 |
1981年 | 77篇 |
1980年 | 62篇 |
1979年 | 55篇 |
1978年 | 37篇 |
1977年 | 29篇 |
1976年 | 24篇 |
1959年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Xiao-Lei Qiu Zi-Rui Fan Yang-Yang Liu Ding-Fu Wang Shi-Xin Wang Chun-Xia Li 《International journal of molecular sciences》2021,22(8)
A self-nanoemulsifying drug delivery system (SNEDDS) was developed to enhance the absorption of heparin after oral administration, in which heparin was compounded with phospholipids to achieve better fat solubility in the form of heparin-phospholipid (HEP-Pc) complex. HEP-Pc complex was prepared using the solvent evaporation method, which increased the solubility of heparin in n-octanol. The successful preparation of HEP-Pc complex was confirmed by differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR) spectroscopy, NMR, and SEM. A heparin lipid microemulsion (HEP-LM) was prepared by high-pressure homogenization and characterized. HEP-LM can enhance the absorption of heparin after oral administration, significantly prolong activated partial thromboplastin time (APTT) and thrombin time (TT) in mice, and reduce fibrinogen (FIB) content. All these outcomes indicate that HEP-LM has great potential as an oral heparin formulation. 相似文献
2.
3.
邓乐善 《中国水能及电气化》2021,(1):56-58
针对民乐县农村人饮机井水位自动供水系统控制中存在的可靠性低、成本高等问题,文章结合深井泵提取地下水进行供水的实际情况,提出了软启动控制柜+浮球开关+微电脑时间控制器改进的思路和方法,运用效果良好。 相似文献
4.
平台支持船由于作业需要通常配备有动力定位系统,其在侧推工况下舱室噪声超标较为严重。针对这个问题采用计算流体力学(CFD)方法,得到侧推螺旋桨作用在导管上的脉动压力,并将时域计算结果转换成噪声计算的激励条件。采用有限元(FE)与统计能量分析(SEA)混合方法建立船体中频段FE-SEA耦合模型并建立船体高频段SEA模型,对某65 m AHTS船侧推工况下全频段(63 Hz~8000 Hz)舱室噪声进行预报,分析该船噪声分布规律及主要影响因素。并建立起全船的SEA模型,在中频段对比SEA与FE-SEA两种方法得到的舱室声压级频谱曲线,验证了使用混合模型的必要性。 相似文献
5.
谭金军 《自动化技术与应用》2021,40(1):181-183
为进一步提升企业思想政治教育工作的信息化水平,本文详细介绍了企业思想政治教育系统的数据库设计方案,以便更加充分地发挥各种多媒体教学设备在企业思想政治教育工作方面的优势。 相似文献
6.
7.
8.
In this paper, a novel method is proposed for increasing the performance through coupling of top-down models adjusting the object detector based on a new loss function. Generally, object detectors and keypoint estimators are sequentially used in real-time multi-person pose estimations; however, these two models are separately trained. Therefore, the results of the object detector are not optimized for the keypoint estimator. To solve this problem, we analyze the relationship between the two models and propose a feedback-based loss optimization in the object detector, based on the estimation results of the keypoint estimator. In addition, the resulting bounding box of the object detector is readjusted to improve the accuracy of the keypoint estimation model. The experimental results demonstrate that the proposed approach can perform real-time operations with a high frame rate similar to that of the baseline model. Moreover, it achieved an accuracy of 74.2 average precision (AP), which is higher than the state-of-the-arts model including the human detector used in the experiment. 相似文献
9.
《Ceramics International》2021,47(24):34521-34528
Aiming at the problem that power density and energy density are difficult to obtain simultaneously under low field, a novel composition (1-x)Na0·5Bi0·5TiO3-xBaZn1/3Ta2/3O3((1-x)NBT-xBZT) was designed and fabricated via solid-state methods. With the addition of BZT, the crystal lattice, structural symmetry, grain size, and dense degree were all increased proved by XRD, Raman, and Archimedes drainage method et al. Because of the enhancement of relaxor behavior, the x=0.10 sample displayed a high permittivity εr of 2871±15% and a low dielectric loss tan δ ≤ 0.025 in the wide temperature range of 60–400 oC. This ceramic also showed maximum recoverable energy density Wd (2.07 J/cm3) with high efficiency η (71.5%) under a low field of 150 kV/cm. Moreover, pulse discharge testing proved that this ceramic possessed both a significant discharge energy density WD (0.96 J/cm3) and a record high power density PD (108.54 MW/cm3). This work provided a promising material for high power and energy applications. 相似文献
10.
Friederike Freiin von Hvel Ekaterini Kefalakes Claudia Grothe 《International journal of molecular sciences》2021,22(1)
Fibroblast growth factor 2 (FGF-2), ubiquitously expressed in humans and mice, is functionally involved in cell growth, migration and maturation in vitro and in vivo. Based on the same mRNA, an 18-kilo Dalton (kDa) FGF-2 isoform named FGF-2 low molecular weight (FGF-2LMW) isoform is translated in humans and rodents. Additionally, two larger isoforms weighing 21 and 22 kDa also exist, summarized as the FGF-2 high molecular weight (FGF-2HMW) isoform. Meanwhile, the human FGF-2HMW comprises a 22, 23, 24 and 34 kDa protein. Independent studies verified a specific intracellular localization, mode of action and tissue-specific spatiotemporal expression of the FGF-2 isoforms, increasing the complexity of their physiological and pathophysiological roles. In order to analyze their spectrum of effects, FGF-2LMW knock out (ko) and FGF-2HMWko mice have been generated, as well as mice specifically overexpressing either FGF-2LMW or FGF-2HMW. So far, the development and functionality of the cardiovascular system, bone formation and regeneration as well as their impact on the central nervous system including disease models of neurodegeneration, have been examined. This review provides a summary of the studies characterizing the in vivo effects modulated by the FGF-2 isoforms and, thus, offers a comprehensive overview of its actions in the aforementioned organ systems. 相似文献