全文获取类型
收费全文 | 13678篇 |
免费 | 1863篇 |
国内免费 | 1183篇 |
专业分类
电工技术 | 2107篇 |
综合类 | 1357篇 |
化学工业 | 1473篇 |
金属工艺 | 222篇 |
机械仪表 | 858篇 |
建筑科学 | 539篇 |
矿业工程 | 175篇 |
能源动力 | 339篇 |
轻工业 | 836篇 |
水利工程 | 332篇 |
石油天然气 | 594篇 |
武器工业 | 95篇 |
无线电 | 1523篇 |
一般工业技术 | 2583篇 |
冶金工业 | 189篇 |
原子能技术 | 315篇 |
自动化技术 | 3187篇 |
出版年
2024年 | 82篇 |
2023年 | 299篇 |
2022年 | 411篇 |
2021年 | 451篇 |
2020年 | 571篇 |
2019年 | 549篇 |
2018年 | 528篇 |
2017年 | 641篇 |
2016年 | 719篇 |
2015年 | 610篇 |
2014年 | 860篇 |
2013年 | 1164篇 |
2012年 | 938篇 |
2011年 | 988篇 |
2010年 | 658篇 |
2009年 | 761篇 |
2008年 | 732篇 |
2007年 | 769篇 |
2006年 | 717篇 |
2005年 | 567篇 |
2004年 | 543篇 |
2003年 | 424篇 |
2002年 | 348篇 |
2001年 | 284篇 |
2000年 | 295篇 |
1999年 | 240篇 |
1998年 | 192篇 |
1997年 | 213篇 |
1996年 | 189篇 |
1995年 | 151篇 |
1994年 | 131篇 |
1993年 | 95篇 |
1992年 | 84篇 |
1991年 | 95篇 |
1990年 | 71篇 |
1989年 | 43篇 |
1988年 | 34篇 |
1987年 | 31篇 |
1986年 | 27篇 |
1985年 | 29篇 |
1984年 | 36篇 |
1983年 | 27篇 |
1982年 | 50篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Dr. Adarshi P. Welegedara Dr. Ansis Maleckis Ruchira Bandara Dr. Mithun C. Mahawaththa Iresha Dilhani Herath Yi Jiun Tan Dr. Angeliki Giannoulis Prof. Daniella Goldfarb Prof. Gottfried Otting Prof. Thomas Huber 《Chembiochem : a European journal of chemical biology》2021,22(8):1480-1486
The selenol group of selenocysteine is much more nucleophilic than the thiol group of cysteine. Selenocysteine residues in proteins thus offer reactive points for rapid post-translational modification. Herein, we show that selenoproteins can be expressed in high yield and purity by cell-free protein synthesis by global substitution of cysteine by selenocysteine. Complete alkylation of solvent-exposed selenocysteine residues was achieved in 10 minutes with 4-chloromethylene dipicolinic acid (4Cl-MDPA) under conditions that left cysteine residues unchanged even after overnight incubation. GdIII−GdIII distances measured by double electron–electron resonance (DEER) experiments of maltose binding protein (MBP) containing two selenocysteine residues tagged with 4Cl-MDPA-GdIII were indistinguishable from GdIII−GdIII distances measured of MBP containing cysteine reacted with 4Br-MDPA tags. 相似文献
2.
Protective coatings from diethylphosphatoethyltriethoxysilane (DEPETS) have been deposited on different polymer substrates in a plasma discharge operated at atmospheric pressure. Plasma polymer chemistry and structure were characterized by means of Fourier transform infrared spectroscopy (FTIR), laser desorption ionization-mass spectrometry (LDI-MS), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). A chemical structure of the plasma polymer has been proposed based on the coating molecular characterization. Coatings were deposited on polycarbonate (PC) and polyamide 6 (PA6) substrates. The flame retardant properties of coated substrate samples were assessed using cone calorimetry and compared to those of bare substrates. A significant increase in the time to ignition (TTI), up to +143%, was recorded after coating deposition due to the formation of a high-performance barrier layer at the surface of both polymer substrates. 相似文献
3.
ABSTRACTThis paper presents an empirical assessment of four state-of-the-art risk-averse approaches to deal with the capacitated lot-sizing problem under stochastic demand. We analyse two mean-risk models based on the semideviation and on the conditional value-at-risk risk measures, and alternate first and second-order stochastic dominance approaches. The extensive computational experiments based on different instances characteristics and on a case-study suggest that CVaR exhibits a good trade-off between risk and performance, followed by the semideviation and first-order stochastic dominance approach. For all approaches, enforcing risk-aversion helps to reduce the cost-standard deviation substantially, which is usually accomplished via increasing production rates. Overall, we can say that very risk-averse decision-makers would be willing to pay an increased price to have a much less risky solution given by CVaR . In less risk-averse settings, though, semideviation and first-order stochastic dominance can be appealing alternatives to provide significantly more stable production planning costs with a marginal increase of the expected costs. 相似文献
4.
This paper is concerned with the problem of joint input and state estimation for linear stochastic systems with direct feedthrough. Based on the fact that each unknown input between any two time steps is always bounded, a novel improved algorithm is proposed. Compared with existing results, this algorithm can effectively enhance estimation accuracy. Moreover, the stability of the algorithm is also discussed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach. 相似文献
5.
6.
Hashim A.
Hashim 《国际强度与非线性控制杂志
》2020,30(10):3848-3870
》2020,30(10):3848-3870
This paper introduces two novel nonlinear stochastic attitude estimators developed on the Special Orthogonal Group with the tracking error of the normalized Euclidean distance meeting predefined transient and steady‐state characteristics. The tracking error is confined to initially start within a predetermined large set such that the transient performance is guaranteed to obey dynamically reducing boundaries and decrease smoothly and asymptotically to the origin in probability from almost any initial condition. The proposed estimators produce accurate attitude estimates with remarkable convergence properties using measurements obtained from low‐cost inertial measurement units. The estimators proposed in continuous form are complemented by their discrete versions for the implementation purposes. The simulation results illustrate the effectiveness and robustness of the proposed estimators against uncertain measurements and large initialization error, whether in continuous or discrete form. 相似文献
7.
8.
讨论了在VMI管理思想下对具有随机需求特性的多客户库存分配问题 ,重点论述了有效近似算法的设计过程 ,最后基于一组模拟数据给出了一个算例。 相似文献
9.
BaTiO3基Au纳米颗粒复合薄膜的制备及其光学性质研究 总被引:1,自引:1,他引:0
采用溶胶-凝胶(sol-gel)方法,成功的将高体积面分比的Au纳米颗粒复合到BaTiO3的非晶薄膜中,并对其光学性质进行了研究。用XRD、TEM、椭偏仪、吸收光谱、光克尔效应OKE(Optical Kerr Effcet)方法对薄膜进行了表征和测试。从吸收光谱观察到表面等离子体共振SPR(Surface Plasma Resonance)峰随热处理温度升高而红移的现象。光学非线性测试表明薄膜具有高的三阶非线性极化率Χ^(3)和超快的响应时间。 相似文献
10.
论文提出利用用户提供的个性化信息来随机产生关联大素数,保证了素数选取的随机化、个性化,提高了RSA算法的安全性。 相似文献