全文获取类型
收费全文 | 2715篇 |
免费 | 122篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 51篇 |
综合类 | 67篇 |
化学工业 | 578篇 |
金属工艺 | 105篇 |
机械仪表 | 105篇 |
建筑科学 | 151篇 |
矿业工程 | 41篇 |
能源动力 | 177篇 |
轻工业 | 336篇 |
水利工程 | 16篇 |
石油天然气 | 33篇 |
武器工业 | 2篇 |
无线电 | 147篇 |
一般工业技术 | 389篇 |
冶金工业 | 326篇 |
原子能技术 | 21篇 |
自动化技术 | 327篇 |
出版年
2024年 | 15篇 |
2023年 | 21篇 |
2022年 | 43篇 |
2021年 | 52篇 |
2020年 | 85篇 |
2019年 | 78篇 |
2018年 | 97篇 |
2017年 | 76篇 |
2016年 | 98篇 |
2015年 | 48篇 |
2014年 | 87篇 |
2013年 | 225篇 |
2012年 | 139篇 |
2011年 | 138篇 |
2010年 | 113篇 |
2009年 | 144篇 |
2008年 | 130篇 |
2007年 | 110篇 |
2006年 | 98篇 |
2005年 | 70篇 |
2004年 | 85篇 |
2003年 | 110篇 |
2002年 | 156篇 |
2001年 | 122篇 |
2000年 | 57篇 |
1999年 | 53篇 |
1998年 | 124篇 |
1997年 | 65篇 |
1996年 | 50篇 |
1995年 | 27篇 |
1994年 | 27篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1965年 | 3篇 |
排序方式: 共有2872条查询结果,搜索用时 0 毫秒
151.
Nanostructured thin films of lead sulfide have been synthesized by a new electrochemical approach based on the underpotential deposition (UPD) of Pb and S from the saturated solution of PbS containing excess of PbS particles as a source of Pb2+ and S2− at various temperatures.We have demonstrated that this new electrochemical route is a simple method with several advantages, including better control of the growth conditions and a one-step process to obtain the nanostructures of PbS. Scanning probe microscopy studies indicate that the growth of PbS nanofilms follows a two-dimensional layer-by-layer growth kinetics at the beginning of electrodeposition but a three-dimensional growth dominates after the formation of the first few layers. The results of morphological and structural investigations reveal that PbS nanostructures grown by this method are single-crystalline in cubic structure and have a preferential orientation along the [2 0 0] direction. The optical absorption spectra of PbS nanostructures show the blue-shift with respect to those of the bulk counterpart, which are attributed as quantum-size effect. 相似文献
152.
Java supports the monitor construct for language‐level synchronization in the context of multi‐threading. This paper introduces the lightweight monitor, an efficient user‐level monitor implementation. The lightweight monitor is useful for single‐threaded Java programs as well as for multi‐threaded Java programs with little lock contention. A 32‐bit lock is embedded in each object for efficient lock access while other monitor data structures are managed using a hash table. We highly optimized the lock manipulation code, which is translated and inlined by a just‐in‐time (JIT) compiler. In the most probable cases, only nine SPARC instructions are spent for lock acquisition and five instructions are spent for lock release. Our experimental results indicate that the lightweight monitor is faster than the monitor implementation in the SUN JDK 1.2 RC1 by up to 21 times in the absence of lock contention and by up to seven times in the presence of lock contention. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
153.
Hakioğlu T 《Journal of the Optical Society of America. A, Optics, image science, and vision》2000,17(12):2411-2421
The two-dimensional Wigner function is examined in polar canonical coordinates, and covariance properties under the action of affine canonical transformations are derived. 相似文献
154.
155.
Raković MJ Kattawar GW Mehrubeoğlu MB Cameron BD Wang LV Rastegar S Coté GL 《Applied optics》1999,38(15):3399-3408
We present both experimental measurements and Monte-Carlo-based simulations of the diffusely backscattered intensity patterns that arise from illuminating a turbid medium with a polarized laser beam. It is rigorously shown that, because of axial symmetry of the system, only seven elements of the effective backscattering Mueller matrix are independent. A new numerical method that allows simultaneous calculation of all 16 elements of the two-dimensional Mueller matrix is used. To validate our method we compared calculations to measurements from a turbid medium that consisted of polystyrene spheres of different sizes and concentrations in deionized water. The experimental and numerical results are in excellent agreement. 相似文献
156.
B Tander K Sarica D Baskin L Abbaso?lu D Sakiz M Bulut 《Canadian Metallurgical Quarterly》1998,14(1-2):14-16
Unilateral torsion of the spermatic cord has been demonstrated to damage the contralateral testis; however, the pathogenesis has not yet been examined in detail. The purpose of this study was to evaluate the influence of unilateral torsion on the contralateral testis in rats by performing ipsilateral division of the genitofemoral nerve (GFN) and/or late orchiectomy. Male 25-day-old, prepubertal Wistar albino rats were divided into five groups: (1) sham operation; (2) unilateral testicular torsion; (3) simultaneous unilateral testicular torsion and ipsilateral GFN division; (4) unilateral testicular torsion and orchiectomy on the 4th day after torsion; and (5) simultaneous unilateral testicular torsion and GFN ipsilateral division, and orchiectomy on the 4th day after torsion. Torsions performed were 720 degrees, all on the right testes. On day 55 after torsion, which represents the early postpubertal period of the rat, the contralateral testes were removed. Tubular biopsy score (TBS) was calculated, and seminiferous tubular diameters (STD) were measured. Student's t-test was used for statistical analysis. There was no contralateral testicular damage in the control group, but in all of the study groups destructive changes were found in the left gonad after torsion of the right testicle. The mean TBS of the study groups was higher than that of the control group. STD values were lower in the study groups, but the differences were not statistically significant between groups. In prepubertal rats, unilateral torsion causes histologically measurable changes in the contralateral testis. Ipsilateral division of the GFN and late orchiectomy did not cause any significant alterations in terms of contralateral damage. Further investigations are needed to determine the role of the GFN in testicular torsion. 相似文献
157.
158.
159.
Ergin itipitiolu 《International journal for numerical methods in engineering》1983,19(6):803-810
Universal serendipity elements (USE) are defined as isoparametric elements having linear, quadratic and cubic node configurations at their edges in an arbitrary manner. Formulation of shape functions and their derivatives for USE is presented. A computer algorithm which allows the efficient application of USE is explained. Only corner nodes are kept transparent to the user. Changing the order of USE is fully automated. It is concluded that the USE concept allows interactive mesh refinement in an efficient manner and eliminates the difficulties encountered in the use of higher order isoparametric serendipity elements. 相似文献
160.