全文获取类型
收费全文 | 90159篇 |
免费 | 1260篇 |
国内免费 | 456篇 |
专业分类
电工技术 | 906篇 |
综合类 | 2343篇 |
化学工业 | 13050篇 |
金属工艺 | 4881篇 |
机械仪表 | 3206篇 |
建筑科学 | 2410篇 |
矿业工程 | 568篇 |
能源动力 | 1555篇 |
轻工业 | 4310篇 |
水利工程 | 1336篇 |
石油天然气 | 451篇 |
无线电 | 9818篇 |
一般工业技术 | 17299篇 |
冶金工业 | 2938篇 |
原子能技术 | 332篇 |
自动化技术 | 26472篇 |
出版年
2024年 | 63篇 |
2023年 | 177篇 |
2022年 | 331篇 |
2021年 | 432篇 |
2020年 | 324篇 |
2019年 | 338篇 |
2018年 | 14731篇 |
2017年 | 13620篇 |
2016年 | 10223篇 |
2015年 | 831篇 |
2014年 | 533篇 |
2013年 | 815篇 |
2012年 | 3463篇 |
2011年 | 9820篇 |
2010年 | 8561篇 |
2009年 | 5837篇 |
2008年 | 7030篇 |
2007年 | 7950篇 |
2006年 | 309篇 |
2005年 | 1335篇 |
2004年 | 1227篇 |
2003年 | 1280篇 |
2002年 | 619篇 |
2001年 | 160篇 |
2000年 | 248篇 |
1999年 | 105篇 |
1998年 | 126篇 |
1997年 | 67篇 |
1996年 | 93篇 |
1995年 | 48篇 |
1994年 | 47篇 |
1993年 | 52篇 |
1992年 | 47篇 |
1991年 | 54篇 |
1990年 | 30篇 |
1988年 | 44篇 |
1987年 | 30篇 |
1984年 | 27篇 |
1968年 | 43篇 |
1967年 | 35篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1963年 | 28篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 39篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
61.
Habibullah Khalilullah Deepak K. Agarwal Mohamed J. Ahsan Surender S. Jadav Hamdoon A. Mohammed Masood Alam Khan Salman A. A. Mohammed Riaz Khan 《International journal of molecular sciences》2022,23(12)
Newly designed series of indole-containing pyrazole analogs, pyrazolinylindoles, were synthesized, and their structures were confirmed based on the spectral data of the 1H NMR, 13C NMR, and HR-MS analyses. Preliminary anti-cancer activity testings were carried out by the National Cancer Institute, United States of America (NCI, USA). Compounds HD02, HD05, and HD12 demonstrated remarkable cytotoxic activities against nine categories of cancer types based cell line panels which included leukemia, colon, breast, melanoma, lungs, renal, prostate, CNS, and ovarian cancer cell lines. The highest cytotoxic effects were exhibited by the compounds HD02 [1-(5-(1-H-indol-3-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-2-phenylethanone], HD05 [1-(3-(4-chlorophenyl)-5-(1H-indol-3-yl)-4,5-dihydro-1H-pyrazol-1-yl)-2-phenoxyethanone], and HD12 [(3-(4-chlorophenyl)-5-(1H-indol-3-yl)-4,5-dihydro-1H-pyrazol-1-yl)(pyridin-4-yl)methanone] against some of the 56 types of NCI-based cell lines in different panels. Compound HD05 showed the maximum range of cancer cell growth inhibitions against all categories of the cell lines in all nine panels. On average, in comparison to the referral standard, imatinib, at a dose level of 10 µM, the HD05 showed significant activity against leukemia in the range of 78.76%, as compared to the imatinib at 9% of cancer cells’ growth inhibitions. Molecular docking simulation studies were performed in silico on the epidermal growth factor receptor (EGFR) tyrosine kinase, in order to validate the activity. 相似文献
62.
Ahmed R. Weshahy Ahmed K. Sakr Ayman A. Gouda Bahig M. Atia H. H. Somaily Mohamed Y. Hanfi M. I. Sayyed Ragaa El Sheikh Enass M. El-Sheikh Hend A. Radwan Mohamed F. Cheira Mohamed A. Gado 《International journal of molecular sciences》2022,23(15)
Spent Ni–Cd batteries are now considered an important source for many valuable metals. The recovery of cadmium, cobalt, and nickel from spent Ni–Cd Batteries has been performed in this study. The optimum leaching process was achieved using 20% H2SO4, solid/liquid (S/L) 1/5 at 80 °C for 6 h. The leaching efficiency of Fe, Cd, and Co was nearly 100%, whereas the leaching efficiency of Ni was 95%. The recovery of the concerned elements was attained using successive different separation techniques. Cd(II) ions were extracted by a solvent, namely, Adogen® 464, and precipitated as CdS with 0.5% Na2S solution at pH of 1.25 and room temperature. The extraction process corresponded to pseudo-2nd-order. The prepared PTU-MS silica was applied for adsorption of Co(II) ions from aqueous solution, while the desorption process was performed using 0.3 M H2SO4. Cobalt was precipitated at pH 9.0 as Co(OH)2 using NH4OH. The kinetic and thermodynamic parameters were also investigated. Nickel was directly precipitated at pH 8.25 using a 10% NaOH solution at ambient temperature. FTIR, SEM, and EDX confirm the structure of the products. 相似文献
63.
Optimization of abrasive water jet cutting of ductile materials 总被引:1,自引:0,他引:1
Full factorial design of experiments was developed in order to investigate the effects of jet pressure, abrasive mixing rate, cutting feed, and plate thickness upon three response variables, surface finish of cutting wear zone, percentage proportion of striation free area, and maximum width of cut. The set of sixteen experiments was performed on each of the following two ductile materials: AISI 4340 (high strength low alloy steel, hardened to 49HRc) and Aluminum 2219. Analysis of Variance (ANOVA) was performed on experimental data in order to determine the significance of effects of different parameters on the performance measures. It was found that cutting feed and thickness were highly influential parameters, while abrasive mixing rate is influential upon surface roughness only. Strong interaction was found between jet pressure and workpiece material. Multi-criteria numerical optimization was performed in order to simultaneously maximize/minimize different combinations of performance measures. 相似文献
64.
DCAF: An MPEG-21 Dynamic Content Adaptation Framework 总被引:1,自引:3,他引:1
Universal Multimedia Access aims at providing a gratifying end user-experience by either adapting the content, be it static
or dynamic, to suit the usage environment or adapting the usage environment, be it client- or server-centric, to suit content.
This paper presents our MPEG-21 Dynamic Content Adaptation Framework, acronym DCAF, which uses a fusion of Genetic Algorithms
and Strength Pareto Optimality to adapt content in order to suit the usage environment.
相似文献
Marios C. Angelides (Corresponding author)Email: |
65.
66.
67.
Previously unexplored resonance conditions are shown to exist for the classical hydrogen atomic system, where the electron
is treated as a classical charged point particle following the nonrelativistic Lorentz-Dirac equation of motion about a stationary
nucleus of opposite charge. For circularly polarized (CP) light directed normal to the orbit, very pronounced subharmonic
resonance behavior is shown to occur with a variety of interesting properties. In particular, only if the amplitude of the
CP light exceeds a critical value, will the resonance continue without radius and energy decay. A perturbation analysis is
carried out to illustrate the main features of the behavior. The present phenomena adds to a growing list of other nonlinear
dynamical behaviors of this simple system, that may well be important for more deeply understanding classical and quantum
connections. 相似文献
68.
Lei Wang Xiaoqing Gong Yongqin Zhang Pengfei Xu Xiaojiang Chen Dingyi Fang Xia Zheng Jun Guo 《Multimedia Tools and Applications》2018,77(3):2973-2990
Chinese calligraphy is a unique visual art, and and is one of the material basis of China’s traditional cultural heritage. However, time had caused the old calligraphy works to weathering and damages, so it is necessary to utilize advanced technologies to protect those works. One of those technologies is digital imaging, and the obtained images by digital imaging can preserve the visual information of calligraphy works better, furthermore, they can be used in further researches. While the basic works for those researches are to extract the artistic features which include two elements, i.e., form and spirit. However, most of the existing methods only extract the form and ignore the characters’ spirit, especially they are insensitive to the slight variation in complex ink strokes. To solve these problems, this paper proposes an extraction method based on regional guided flter (RGF) with reference images, which is generated by KNN matting and used as the input image for RGF. Since RGF is sensitive to the slight variation of ink, so the detailed information of the inside of strokes can be detected better. Besides, unlike the past works, which filter the whole strokes, RGF filters the inside of strokes and edges in different windows respectively, which results in that the edges are preserved accurately. Results from a deployment of several famous Chinese calligraphy works demonstrate that our method can extract more accurate and complete form and spirit with lower error rate. 相似文献
69.
The polynomial-time solvable k-hurdle problem is a natural generalization of the classical s-t minimum cut problem where we must select a minimum-cost subset S of the edges of a graph such that |p∩S|≥k for every s-t path p. In this paper, we describe a set of approximation algorithms for “k-hurdle” variants of the NP-hard multiway cut and multicut problems. For the k-hurdle multiway cut problem with r terminals, we give two results, the first being a pseudo-approximation algorithm that outputs a (k−1)-hurdle solution whose cost is at most that of an optimal solution for k hurdles. Secondly, we provide a
2(1-\frac1r)2(1-\frac{1}{r})-approximation algorithm based on rounding the solution of a linear program, for which we give a simple randomized half-integrality
proof that works for both edge and vertex k-hurdle multiway cuts that generalizes the half-integrality results of Garg et al. for the vertex multiway cut problem. We
also describe an approximation-preserving reduction from vertex cover as evidence that it may be difficult to achieve a better
approximation ratio than
2(1-\frac1r)2(1-\frac{1}{r}). For the k-hurdle multicut problem in an n-vertex graph, we provide an algorithm that, for any constant ε>0, outputs a ⌈(1−ε)k⌉-hurdle solution of cost at most O(log n) times that of an optimal k-hurdle solution, and we obtain a 2-approximation algorithm for trees. 相似文献
70.
In this paper we propose an automatic methodology to verify the soundness of model checking reduction techniques. The idea is to use the consistency of the specifications to verify if the reduced model is faithful to the original one. The user provides the reduction technique, the specification and the system under verification. Then, using Higher Order Logic he verifies automatically if the reduction technique is soundly applied. The method is completely defined in an MDG–HOL special integration platform that combines an automatic high level model checking tool Multiway Decision Graphs (MDGs) within the HOL theorem prover. We provide two case studies, the first one is the reduction using SAT–MDG of an Island Tunnel Controller and the second one is the MDG–HOL assume-guarantee reduction of the Look-Aside Interface. The obtained results of our approach offer a considerable gain in terms of the correctness of heuristics and reduction techniques as applied to commercial model checking, however a small penalty is paid in terms of CPU time and memory usage. 相似文献