全文获取类型
收费全文 | 102289篇 |
免费 | 9036篇 |
国内免费 | 4964篇 |
专业分类
电工技术 | 6500篇 |
技术理论 | 21篇 |
综合类 | 18139篇 |
化学工业 | 6162篇 |
金属工艺 | 4514篇 |
机械仪表 | 8831篇 |
建筑科学 | 17588篇 |
矿业工程 | 4655篇 |
能源动力 | 2594篇 |
轻工业 | 3834篇 |
水利工程 | 5981篇 |
石油天然气 | 3824篇 |
武器工业 | 1007篇 |
无线电 | 6884篇 |
一般工业技术 | 10512篇 |
冶金工业 | 3639篇 |
原子能技术 | 600篇 |
自动化技术 | 11004篇 |
出版年
2024年 | 328篇 |
2023年 | 838篇 |
2022年 | 1664篇 |
2021年 | 1894篇 |
2020年 | 2138篇 |
2019年 | 1741篇 |
2018年 | 1784篇 |
2017年 | 2538篇 |
2016年 | 2932篇 |
2015年 | 3520篇 |
2014年 | 7199篇 |
2013年 | 5769篇 |
2012年 | 7635篇 |
2011年 | 8037篇 |
2010年 | 6388篇 |
2009年 | 6971篇 |
2008年 | 6304篇 |
2007年 | 8164篇 |
2006年 | 7425篇 |
2005年 | 6107篇 |
2004年 | 4999篇 |
2003年 | 4148篇 |
2002年 | 3296篇 |
2001年 | 2806篇 |
2000年 | 2445篇 |
1999年 | 1872篇 |
1998年 | 1264篇 |
1997年 | 1098篇 |
1996年 | 998篇 |
1995年 | 810篇 |
1994年 | 666篇 |
1993年 | 513篇 |
1992年 | 447篇 |
1991年 | 282篇 |
1990年 | 264篇 |
1989年 | 240篇 |
1988年 | 184篇 |
1987年 | 120篇 |
1986年 | 91篇 |
1985年 | 52篇 |
1984年 | 58篇 |
1983年 | 34篇 |
1982年 | 25篇 |
1981年 | 51篇 |
1980年 | 38篇 |
1979年 | 29篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1975年 | 12篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Craig S. Long Albert A. Groenwold 《International journal for numerical methods in engineering》2004,61(6):837-855
Reduced integration is frequently used in evaluating the element stiffness matrix of quadratically interpolated finite elements. Typical examples are the serendipity (Q8) and Lagrangian (Q9) membrane finite elements, for which a reduced 2 × 2 Gauss–Legendre integration rule is frequently used, as opposed to full 3 × 3 Gauss–Legendre integration. This ‘softens’ these element, thereby increasing accuracy, albeit at the introduction of spurious zero energy modes on the element level. This is in general not considered problematic for the ‘hourglass’ mode common to Q8 and Q9 elements, since this spurious mode is non‐communicable. The remaining two zero energy modes occurring in the Q9 element are indeed communicable. However, in topology optimization for instance, conditions may arise where the non‐communicable spurious mode associated with the elements becomes activated. To effectively suppress these modes altogether in elements employing quadratic interpolation fields, two modified quadratures are employed herein. For the Q8 and Q9 membrane elements, the respective rules are a five and an eight point rule. As compared to fully integrated elements, the new rules enhance element accuracy due to the introduction of soft, higher‐order deformation modes. A number of standard test problems reveal that element accuracy remains comparable to that of the under‐integrated counterparts. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
42.
陈继初 《湖南冶金职业技术学院学报》2003,(4)
会计政策选择类型在理论上大体可分为机会主义型和效率(或有效契约)型。会计政策选择具有效率性,但也为经理人员的机会主义行为打开了大门。在我国,由于企业缺乏一系列有效的激励约束机制,会计政策选择的机会主义仍然严重。为此,必须建立适合我国企业有效的激励约束机制。 相似文献
43.
G. MENEGHETTI P. LAZZARIN 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(2):95-106
The paper presents an expression useful to estimate the notch stress intensity factor (NSIF) from finite element analyses carried out by using a mesh pattern with a constant element size. The evaluation of the NSIF from a numerical analysis of the local stress field usually requires very refined meshes and then large computational effort. The usefulness of the presented expression is that (i) only the elastic peak stress numerically evaluated at the V‐notch tip is needed and no longer the whole stress–distance set of data; (ii) the adopted meshes are rather coarse if compared to those necessary for the evaluation of the whole local stress field. The proposed expression needs the evaluation of a virtual V‐notch tip radius, i.e. the radius which would produce the same elastic peak stress than that calculated by FEM at the sharp V‐notch tip by means of a given mesh pattern. Once such a radius has been theoretically determined for a given geometry, the expression can be applied in a wide range of notch depths and opening angles. 相似文献
44.
A. Alt Dr.‐Ing. H. Mertens U. Arz L. Blessing C. Berger 《Materialwissenschaft und Werkstofftechnik》2007,38(5):402-409
High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence. 相似文献
45.
No authorship indicated 《Canadian Metallurgical Quarterly》2007,62(5):388
Announces the 2007 recipient of the Gold Medal Award for Life Achievement in the Practice of Psychology: Patricia M. Bricklin. A brief biography, highlighting areas of special focus in Bricklin's work, is provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
No authorship indicated 《Canadian Metallurgical Quarterly》2007,62(5):391
Announces the 2007 recipient of the Gold Medal Award for Life Achievement in the Psychology in the Public Interest: Rhoda K. Unger. A brief biography, highlighting areas of special focus in Unger's work, is provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
R. Knockaert I. Doghri Y. Marchal T. Pardoen F. Delannay 《International Journal of Fracture》1996,81(4):383-399
Double-edge notched (DENT) steel plates were pulled until complete fracture and several experimental observations were made (using profilometry and scanning electron microscopy). The essential work of fracture (EWF) model was found to be well verified. Numerical simulations—up to the maximum load only—of some experiments were performed using the finite element method (FEM), and incorporating geometric and material non-linearities (large deformation elasto-plasticity). Some experimental measurements were compared with the corresponding numerical computations and excellent agreement was found. 相似文献
48.
Recently, a demand for small-capacity generators has been increasing as electric sources in small ships and automobiles or as portable electric sources driven by engines. It is desired that the structure of small-capacity generators be simple and robust, and that the generators be highly reliable, easily maintained and controlled. This paper describes an analysis of the original brushless synchronous generator without exciter. The output voltage can be adjusted in the wide range by controlling the stator dc current. To analyze the characteristics of this generator, the finite element method is applied. It is found that the results of theoretical analysis agree well with the experimental results. 相似文献
49.
研究了热传导方程的通解,进而提出激光热源形成的微观机理和热源形成过程的三个理论计算式。对激光热效应的应用具有指导意义。 相似文献
50.
NUMERICALSIMULATIONSOFWHOLEFIELDBEHAVIORFORROUNDBUOYANTJETLiWei,HuaiWen-xin(WuhanUniversityofHydraulicandElectricEngineering,... 相似文献