全文获取类型
收费全文 | 577720篇 |
免费 | 7041篇 |
国内免费 | 1011篇 |
专业分类
电工技术 | 10575篇 |
综合类 | 474篇 |
化学工业 | 94451篇 |
金属工艺 | 23449篇 |
机械仪表 | 18763篇 |
建筑科学 | 12931篇 |
矿业工程 | 4328篇 |
能源动力 | 14703篇 |
轻工业 | 48517篇 |
水利工程 | 7029篇 |
石油天然气 | 15022篇 |
武器工业 | 39篇 |
无线电 | 60667篇 |
一般工业技术 | 117643篇 |
冶金工业 | 95954篇 |
原子能技术 | 14708篇 |
自动化技术 | 46519篇 |
出版年
2022年 | 4539篇 |
2021年 | 6388篇 |
2020年 | 4364篇 |
2019年 | 5636篇 |
2018年 | 9619篇 |
2017年 | 9845篇 |
2016年 | 10316篇 |
2015年 | 6423篇 |
2014年 | 10756篇 |
2013年 | 26871篇 |
2012年 | 16491篇 |
2011年 | 21897篇 |
2010年 | 17578篇 |
2009年 | 19388篇 |
2008年 | 19586篇 |
2007年 | 19248篇 |
2006年 | 16670篇 |
2005年 | 15023篇 |
2004年 | 14248篇 |
2003年 | 13904篇 |
2002年 | 13443篇 |
2001年 | 12967篇 |
2000年 | 12407篇 |
1999年 | 12123篇 |
1998年 | 27727篇 |
1997年 | 20113篇 |
1996年 | 15711篇 |
1995年 | 12057篇 |
1994年 | 10906篇 |
1993年 | 10659篇 |
1992年 | 8389篇 |
1991年 | 8143篇 |
1990年 | 8021篇 |
1989年 | 7787篇 |
1988年 | 7506篇 |
1987年 | 6771篇 |
1986年 | 6565篇 |
1985年 | 7423篇 |
1984年 | 6722篇 |
1983年 | 6457篇 |
1982年 | 5789篇 |
1981年 | 5912篇 |
1980年 | 5649篇 |
1979年 | 5747篇 |
1978年 | 5680篇 |
1977年 | 6186篇 |
1976年 | 7691篇 |
1975年 | 5117篇 |
1974年 | 4904篇 |
1973年 | 4983篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
A. O. Skomorokhov V. N. Kutinsky M. T. Slepov 《Pattern Recognition and Image Analysis》2006,16(1):85-88
The paper describes a few modifications of the classification tree construction algorithm that have proved to be useful for
solving tasks of noise spectra processing with reference to NPP diagnostics.
The article was translated by the authors. 相似文献
962.
The effect of coherency loss on the development of precipitate size distribution under cascade-producing irradiation is considered. The nucleation of coherent precipitates, their growth followed by coherency loss and cascade-induced dissolution of large incoherent precipitates can occur simultaneously resulting in formation of a quasi-stationary size distribution of semicoherent precipitates. To describe this process we consider co-evolution of a mixed population of coherent, semicoherent and incoherent precipitates. Mathematically, the problem is formulated as a set of discrete rate equations of nucleation kinetics (the Master equation approach) which is also used for later stages of evolution. To solve the corresponding large set of equations (typically, more than 105 equations) an efficient numerical method is developed. The simulation results obtained for material parameters and irradiation conditions typical for nuclear reactors show that the coherency loss affects considerably evolution of the precipitate population. Under certain irradiation conditions, both in solution-annealed alloys and in aged ones, the mean precipitate size and the number density during prolonged irradiation tend to steady state values, whereas the size distribution function of large precipitates narrows. The width of the quasi-stationary size distribution is controlled by cascade parameters. It was found that the asymptotic quasi-stationary state of the precipitate population may depend on initial state of the alloy. 相似文献
963.
I. Ya. Braslavskii A. V. Kostylev D. V. Mezeusheva 《Russian Electrical Engineering》2007,78(11):603-606
The use of prognostic control methods in the digital systems controlling asynchronous electric drives are considered. The methodology for synthesizing predictors on the basis of neural networks is explained. An example of the synthesis of a numeral predictor for a closed control loop is considered. 相似文献
964.
965.
V. N. Serebryany A. Ya. Kochubei S. F. Kurtasov K. E. Mel’nikov 《Russian Metallurgy (Metally)》2007,(1):73-78
Quantitative texture analysis is used to study texture formation in an MA2-1 magnesium alloy subjected to axisymmetric upsetting at temperatures of 250–450°C and strain rates of 10?4–100 ?1. The deformed structure is examined by optical microscopy, and the results obtained are used to plot the structural-state diagram of the alloy after 50% upsetting. The experimental textures are compared with the textures calculated in terms of a thermoactivation model. 相似文献
966.
Motion field and optical flow: qualitative properties 总被引:7,自引:0,他引:7
Verri A. Poggio T. 《IEEE transactions on pattern analysis and machine intelligence》1989,11(5):490-498
It is shown that the motion field the 2-D vector field which is the perspective projection on the image plane of the 3-D velocity field of a moving scene, and the optical flow, defined as the estimate of the motion field which can be derived from the first-order variation of the image brightness pattern, are in general different, unless special conditions are satisfied. Therefore, dense optical flow is often ill-suited for computing structure from motion and for reconstructing the 3-D velocity field by algorithms which require a locally accurate estimate of the motion field. A different use of the optical flow is suggested. It is shown that the (smoothed) optical flow and the motion field can be interpreted as vector fields tangent to flows of planar dynamical systems. Stable qualitative properties of the motion field, which give useful informations about the 3-D velocity field and the 3-D structure of the scene, usually can be obtained from the optical flow. The idea is supported by results from the theory of structural stability of dynamical systems 相似文献
967.
968.
I A Bukaeva L A Iakovleva B A Lapin L V Indzhiia E M Kobe 《Eksperimental?nai?a onkologii?a》1987,9(4):26-30
The results of morphological study of B- and T-cellular immunoblast baboon lymphomas are presented. Differences are found both in the structure of tumour cells and in the histostructure of tumours as a whole. The tumor cells of B-immunoblastic lymphomas expressed mainly IgM. The tumour cells of certain T-immunoblastic lymphomas being investigated by means of monoclonal OKT4 antibodies had a surface phenotype peculiar to T-helper cells. 相似文献
969.
I A Lisniak 《Eksperimental?nai?a onkologii?a》1987,9(4):72-73
A fraction with the angiogenetic activity was obtained by the methods of the gel-chromatography on G-100 and the ion-exchange chromatography on DEAE-cellulose. Treatment of this fraction with the 10% water isopropanol solution has led to dissociation of the obtained material with a release of a low-molecular-weight angiogenic factor with a high angiogenic activity when tested on the chorioallantoic membrane. The molecular weight of this factor (300-600 daltons) was estimated by the chromatography on the biogel P2. 相似文献
970.
Factors affecting the performance of antacids F-MA 11, dihydroxy aluminum aminoacetate, magaldrate and magnesium hydroxide were studied in vitro using Schaub's acid neutralization test, a modified Reheis reaction velocity test and the USP test. From the results obtained it was evident that type and combination of antacid, the adjuvants and formulation techniques used in preparation of antacids affect their performance. The USP preliminary antacid test and acid neutralization test are not optimal in vitro tests to evaluate in vitro onset and duration of action of antacids. 相似文献