全文获取类型
收费全文 | 86819篇 |
免费 | 9995篇 |
国内免费 | 6115篇 |
专业分类
电工技术 | 8433篇 |
技术理论 | 4篇 |
综合类 | 10873篇 |
化学工业 | 5498篇 |
金属工艺 | 6370篇 |
机械仪表 | 12273篇 |
建筑科学 | 7735篇 |
矿业工程 | 3508篇 |
能源动力 | 2204篇 |
轻工业 | 3918篇 |
水利工程 | 2418篇 |
石油天然气 | 2393篇 |
武器工业 | 1097篇 |
无线电 | 6285篇 |
一般工业技术 | 10457篇 |
冶金工业 | 2703篇 |
原子能技术 | 567篇 |
自动化技术 | 16193篇 |
出版年
2024年 | 184篇 |
2023年 | 1351篇 |
2022年 | 2242篇 |
2021年 | 2656篇 |
2020年 | 2988篇 |
2019年 | 2537篇 |
2018年 | 2283篇 |
2017年 | 2918篇 |
2016年 | 3264篇 |
2015年 | 3501篇 |
2014年 | 5468篇 |
2013年 | 5217篇 |
2012年 | 6700篇 |
2011年 | 6882篇 |
2010年 | 5090篇 |
2009年 | 5208篇 |
2008年 | 4934篇 |
2007年 | 6168篇 |
2006年 | 5741篇 |
2005年 | 4674篇 |
2004年 | 3815篇 |
2003年 | 3224篇 |
2002年 | 2780篇 |
2001年 | 2348篇 |
2000年 | 1935篇 |
1999年 | 1602篇 |
1998年 | 1175篇 |
1997年 | 1081篇 |
1996年 | 894篇 |
1995年 | 840篇 |
1994年 | 702篇 |
1993年 | 555篇 |
1992年 | 426篇 |
1991年 | 303篇 |
1990年 | 280篇 |
1989年 | 212篇 |
1988年 | 190篇 |
1987年 | 93篇 |
1986年 | 76篇 |
1985年 | 42篇 |
1984年 | 51篇 |
1983年 | 46篇 |
1982年 | 46篇 |
1981年 | 28篇 |
1980年 | 30篇 |
1979年 | 32篇 |
1978年 | 15篇 |
1977年 | 12篇 |
1974年 | 8篇 |
1959年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
1.
2.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM. 相似文献
3.
4.
The construction and examination of meso-structural finite element models of a Chemical-Vapor-Infiltrated (CVI) C/SiC composite is carried out based on X-ray microtomography digital images (IB-FEM). The accurate meso-structural features of the C/SiC composites, which are consisted of carbon fiber tows and CVI-SiC matrix, in particular the cavity defects, are reconstructed. With the IB-FEM, the damage evolution and fracture behaviors of the C/SiC composite are investigated. At the same time, an in situ tensile test is applied to the C/SiC composite under a CT real-time quantitative imaging system, aiming to investigate the damage and failure features of the material as well as to verify the IB-FEM. The IB-FEM results indicate that material damage initially occur at the defects, followed by propagating toward the fiber-tow/SiC-matrix interfaces, ultimately, combined into macro-cracks, which is in good agreement with the in situ CT experiment results. 相似文献
5.
针对煤矿进口锚杆机除尘马达频繁出现故障的情况,通过排查除尘装置的安装方式和监测马达工作时的压力状态,查找故障原因,并制定解决方案。通过马达外接单向阀,可满足马达进油口最低安全压力限制的要求,解决了马达频繁损坏的问题,保障了设备工作的稳定性,提高了工作效率。 相似文献
6.
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
7.
Li-Xiang Wu Lin-Lin Zhu Wei-Ming Guo Shi-Kuan Sun Wen-Bin Niu Jia-Xiang Xue Jian-Han Zhai Hai-Bin Ma Rui-Lin Lin Hua-Tay Lin Kevin Plucknett Ye-Hong Liao Tong Liu Qi-Sen Ren 《Journal of the European Ceramic Society》2021,41(1):225-232
The joining of liquid-phase sintered SiC (LPS-SiC) ceramics was conducted using spark plasma sintering (SPS), through solid state diffusion bonding, with Ti-metal foil as a joining interlayer. Samples were joined at 1400 °C, under applied pressures of either 10 or 30 MPa, and with different atmospheres (argon, Ar, vs. vacuum). It was demonstrated that the shear strength of the joints increased with an increase in the applied joining pressure. The joining atmosphere also affected on both the microstructure and shear strength of the SiC joints. The composition and microstructure of the interlayer were examined to understand the mechanism. As a result, a SiC-SiC joining with a good mechanical performance could be achieved under an Ar environment, which in turn could provide a cost-effective approach and greatly widen the applications of SiC ceramic components with complex shape. 相似文献
8.
梯度分层铝合金蜂窝板是一种有效的吸能结构,本工作在梯度铝蜂窝结构的基础上根据梯度率的概念,通过改变蜂窝芯层的胞壁长度,设计了4种质量相同、梯度率不同的铝蜂窝夹芯结构。通过准静态压缩实验,并结合非线性有限元模拟准静态及冲击态下梯度铝蜂窝夹芯结构的变形情况及其力学性能,分析对比了相同质量下梯度铝蜂窝夹芯结构在准静态下的变形模式以及冲击载荷下分层均质蜂窝结构和不同梯度率的分层梯度蜂窝结构的动态响应和能量吸收特性。结果表明:在准静态压缩过程中,铝蜂窝梯度夹芯板的变形具有明显的局部化特征,蜂窝芯的变形为低密度优先变形直至密实,层级之间的密实化应变差随芯层密度的增大而逐渐减小;在高速冲击下,梯度蜂窝板并非严格按照准静态过程中逐级变形直至密实,而是在锤头冲击惯性及芯层密度的相互作用下整体发生的线弹性变形、弹性屈曲、塑性坍塌及密实化;另外,在本工作所设计的梯度率中,当梯度率为γ1=0.0276时,梯度蜂窝夹芯板的吸能性达到最好,相较于同等质量下的均质蜂窝夹芯板,能量吸收提高了10.63%。 相似文献
9.
10.
The ways in which environmental priorities are framed are varied and influenced by political forces. One technological advance--the proliferation of government open data portals (ODPs)--has the potential to improve governance through facilitating access to data. Yet it is also known that the data hosted on ODPs may simply reflect the goals and interests of multiple levels of political power. In this article, I use traditional statistical correlation and regression techniques along with newer natural language processing and machine learning algorithms to analyze the corpus of datasets hosted on government ODPs (total: 49,066) to extract patterns that relate scales of governance and political liberalism/conservatism to the priorities and meaning attached to environmental issues. I find that state-level and municipal-level ODPs host different categories of environmental datasets, with municipal-level ODPs generally hosting more datasets pertaining to services and amenities and state-level ODPs hosting more datasets pertaining to resource protection and extraction. Stronger trends were observed for the influences of political conservatism/liberalism among state-level ODPs than for municipal-level ODPs. 相似文献