全文获取类型
收费全文 | 5490篇 |
免费 | 529篇 |
国内免费 | 100篇 |
学科分类
工业技术 | 6119篇 |
出版年
2024年 | 22篇 |
2023年 | 131篇 |
2022年 | 171篇 |
2021年 | 345篇 |
2020年 | 222篇 |
2019年 | 210篇 |
2018年 | 254篇 |
2017年 | 237篇 |
2016年 | 228篇 |
2015年 | 192篇 |
2014年 | 224篇 |
2013年 | 351篇 |
2012年 | 271篇 |
2011年 | 304篇 |
2010年 | 252篇 |
2009年 | 231篇 |
2008年 | 247篇 |
2007年 | 215篇 |
2006年 | 196篇 |
2005年 | 155篇 |
2004年 | 153篇 |
2003年 | 118篇 |
2002年 | 143篇 |
2001年 | 62篇 |
2000年 | 69篇 |
1999年 | 66篇 |
1998年 | 142篇 |
1997年 | 98篇 |
1996年 | 80篇 |
1995年 | 71篇 |
1994年 | 58篇 |
1993年 | 51篇 |
1992年 | 46篇 |
1991年 | 36篇 |
1990年 | 37篇 |
1989年 | 41篇 |
1988年 | 19篇 |
1987年 | 35篇 |
1986年 | 26篇 |
1985年 | 41篇 |
1984年 | 39篇 |
1983年 | 23篇 |
1982年 | 22篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1977年 | 16篇 |
1976年 | 22篇 |
1974年 | 13篇 |
1973年 | 12篇 |
排序方式: 共有6119条查询结果,搜索用时 62 毫秒
61.
提出了一种面向大视场高精度视觉测量的多红外目标靶点(红外LED)亮度自适应控制方法。以微控制器PIC16F873A和LED驱动芯片MAX6964作为核心器件,设计了可满足大空间范围内靶点亮度控制需求的多目标靶点控制驱动器。为了使LED在近距测量时的调节精度和远近距离测量时的发光亮度都能满足要求,根据MAX6964输出特点设计了PWM信号输出电路,并采用推挽电路驱动LED。实验证明,目标靶点在CCD相机上成像光斑稳定一致。 相似文献
62.
San-Vicente G Aguinaga I Tomás Celigüeta J 《IEEE transactions on visualization and computer graphics》2012,18(2):228-241
Mass-Spring Models (MSMs) are used to simulate the mechanical behavior of deformable bodies such as soft tissues in medical applications. Although they are fast to compute, they lack accuracy and their design remains still a great challenge. The major difficulties in building realistic MSMs lie on the spring stiffness estimation and the topology identification. In this work, the mechanical behavior of MSMs under tensile loads is analyzed before studying the spring stiffness estimation. In particular, the performed qualitative and quantitative analysis of the behavior of cubical MSMs shows that they have a nonlinear response similar to hyperelastic material models. According to this behavior, a new method for spring stiffness estimation valid for linear and nonlinear material models is proposed. This method adjusts the stress-strain and compressibility curves to a given reference behavior. The accuracy of the MSMs designed with this method is tested taking as reference some soft-tissue simulations based on nonlinear Finite Element Method (FEM). The obtained results show that MSMs can be designed to realistically model the behavior of hyperelastic materials such as soft tissues and can become an interesting alternative to other approaches such as nonlinear FEM. 相似文献
63.
Renato Maia Renato Cerqueira Clarisse Sieckenius de Souza Tomás Guisasola-Gorham 《Empirical Software Engineering》2012,17(3):166-199
Today middleware is much more powerful, more reliable and faster than it used to be. Nevertheless, for the application developer,
the complexity of using middleware platforms has increased accordingly. The volume and variety of application contexts that
current middleware technologies have to support require that developers be able to anticipate the widest possible range of
execution environments, desired and undesired effects of different programming strategies, handling procedures for runtime
errors, and so on. This paper shows how a generic framework designed to evaluate the usability of notations (the Cognitive Dimensions of Notations Framework, or CDN) has been instantiated and used to analyze the cognitive
challenges involved in adapting middleware platforms. This human-centric perspective allowed us to achieve novel results compared
to existing middleware evaluation research, typically centered around system performance metrics. The focus of our study is
on the process of adapting middleware implementations, rather than in the end product of this activity. Our main contributions
are twofold. First, we describe a qualitative CDN-based method to analyze the cognitive effort made by programmers while adapting
middleware implementations. And second, we show how two platforms designed for flexibility have been compared, suggesting
that certain programming language design features might be particularly helpful for developers. 相似文献
64.
Tomá? Kroupa 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(11):1851-1861
We generalise belief functions to many-valued events which are represented by elements of Lindenbaum algebra of infinite-valued ?ukasiewicz propositional logic. Our approach is based on mass assignments used in the Dempster–Shafer theory of evidence. A generalised belief function is totally monotone and it has Choquet integral representation with respect to a unique belief measure on Boolean events. 相似文献
65.
Federico Ferreres Alberto Ortiz Carmen Silva Christina Garcia-Viguera Francisco A. Tomás-Barberán Francisco Tomás-Lorente 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1992,194(2):139-143
Summary The flavonoids present in ten selected samples of La Alcarria honey with different pollen compositions have been HPLC analysed in order to establish if correlations between botanical origin and flavonoid profiles are possible. A common flavonoid pattern is observed in the different samples showing that pollen is not the main source of honey flavonoids. A close correlation between the flavonoid patterns of honey flavonoids and propolis flavonoids has been found suggesting that flavonoid analysis could be more useful in geographical origin determinations than in botanical origin studies.
Flavonoide des La-Alcarria-Honigs Eine Studie ihres botanischen Ursprungs
Zusammenfassung Die Flavonoide in Proben in Alcarria-Honig mit unterschiedlicher Pollenzusammensetzung wurden untersucht, um Kortrelationen zwischen dem botanischen Ursprung und den möglichen Flavonoiden zu finden. In den verschiedenen Proben wurde ein Flavonoid-Muster gefunden, wobei der Pollen nicht die Hauptquelle der Honigflavonoide ist. Es wurde jedoch eine enge Korrelation zwischen den Flavonoid-Mustern des Honigs und des Bienenkittharzes gefunden, was für die geographische Herkunft wichtiger ist als die botanische.相似文献
66.
The empowerment of service workers: what, why, how, and when 总被引:17,自引:0,他引:17
In recent years, businesses have rushed to adopt an empowerment approach to service delivery in which employees face customers "free of rulebooks," encouraged to do whatever is necessary to satisfy them. But that approach may not be right for everyone. Bowen and Lawler look at the benefits and costs of empowering employees, the range of management practices that empower employees to varying degrees, and key business characteristics that affect the choice of approaches. Managers need to make sure that there is a good fit between their organizational needs and their approach to frontline employees. 相似文献
67.
Joseph R. Fox P. Costa Kokoropoulos Gary H. Wiseman H. K. Bowen 《Journal of Materials Science》1987,22(12):4528-4531
Organosilanes of the general formula R
x
Si(OR)4–x
(where R is an alkyl group and R = CH3 or CH2CH3) were used to sterically stabilize hexane dispersions of submicrometre silica spheres. The dispersions were characterized according to sediment volume results. For 0.5m silica particles, the sediment density increased by more than a factor of three up to 50 to 55% of theoretical in the presence of organosilanes with 12 or more carbons in the R group. Solid-state13C nuclear magnetic resonance was used to characterize the powder-dispersant interaction; this technique can distinguish between carbons in the R group of the organosilane and residual organic groups in the silica. Scanning electron micrographs of filter compacts were used to further characterize the dispersions and indicated the presence of primary particles as well as small agglomerates. 相似文献
68.
针对电动汽车充电站建设运营成本高,土地利用率较低,功能单一的缺点,提出了电动汽车充光储一体化充电站的容量优化方法。考虑光伏出力及电动汽车充电负荷的不确定性,研究在不确定性环境下的容量配置问题,以保证优化方案的可靠性。基于机会约束规划,以建设运营成本最小为目标建立电动汽车充光储一体化充电站容量配置模型,通过序列运算理论将模型中含有随机变量的约束进行确定性转化,采用CPLEX作为模型的求解工具。算例验证了所提模型及方法的有效性。 相似文献
69.
Veronika Olejnickova Matej Kocka Alena Kvasilova Hana Kolesova Adam Dziacky Tom Gidor Lihi Gidor Barbora Sankova Martina Gregorovicova Robert G. Gourdie David Sedmera 《International journal of molecular sciences》2021,22(5)
The mammalian ventricular myocardium forms a functional syncytium due to flow of electrical current mediated in part by gap junctions localized within intercalated disks. The connexin (Cx) subunit of gap junctions have direct and indirect roles in conduction of electrical impulse from the cardiac pacemaker via the cardiac conduction system (CCS) to working myocytes. Cx43 is the dominant isoform in these channels. We have studied the distribution of Cx43 junctions between the CCS and working myocytes in a transgenic mouse model, which had the His-Purkinje portion of the CCS labeled with green fluorescence protein. The highest number of such connections was found in a region about one-third of ventricular length above the apex, and it correlated with the peak proportion of Purkinje fibers (PFs) to the ventricular myocardium. At this location, on the septal surface of the left ventricle, the insulated left bundle branch split into the uninsulated network of PFs that continued to the free wall anteriorly and posteriorly. The second peak of PF abundance was present in the ventricular apex. Epicardial activation maps correspondingly placed the site of the first activation in the apical region, while some hearts presented more highly located breakthrough sites. Taken together, these results increase our understanding of the physiological pattern of ventricular activation and its morphological underpinning through detailed CCS anatomy and distribution of its gap junctional coupling to the working myocardium. 相似文献
70.
当具有恒功率特性的负荷与源侧换流器级联时,会降低直流微网系统的阻尼,带来稳定性问题。针对上述问题,采用TS模糊模型,对含恒功率负荷的非线性直流微网系统进行建模。为有效抵抗直流微网和控制系统参数的不确定性,设计了一种鲁棒非脆弱控制器,在计算参数不确定矩阵的基础上,推导以线性矩阵不等式表示的Lyapunov指数稳定条件。经Matlab/Simulink仿真测试,所设计控制器满足直流微网对于稳定性的要求,能够提高闭环系统的暂态性能,对系统及控制器内部的不确定性拥有较强的鲁棒性。 相似文献