全文获取类型
收费全文 | 203140篇 |
免费 | 2740篇 |
国内免费 | 612篇 |
专业分类
电工技术 | 3493篇 |
综合类 | 152篇 |
化学工业 | 29522篇 |
金属工艺 | 8063篇 |
机械仪表 | 6092篇 |
建筑科学 | 5003篇 |
矿业工程 | 1387篇 |
能源动力 | 5179篇 |
轻工业 | 17526篇 |
水利工程 | 2316篇 |
石油天然气 | 4046篇 |
武器工业 | 8篇 |
无线电 | 23171篇 |
一般工业技术 | 40403篇 |
冶金工业 | 38802篇 |
原子能技术 | 5093篇 |
自动化技术 | 16236篇 |
出版年
2021年 | 1659篇 |
2019年 | 1614篇 |
2018年 | 2617篇 |
2017年 | 2703篇 |
2016年 | 2844篇 |
2015年 | 1844篇 |
2014年 | 3128篇 |
2013年 | 9146篇 |
2012年 | 5179篇 |
2011年 | 7190篇 |
2010年 | 5749篇 |
2009年 | 6495篇 |
2008年 | 6629篇 |
2007年 | 6691篇 |
2006年 | 5713篇 |
2005年 | 5381篇 |
2004年 | 5129篇 |
2003年 | 5039篇 |
2002年 | 4644篇 |
2001年 | 4750篇 |
2000年 | 4657篇 |
1999年 | 4821篇 |
1998年 | 11452篇 |
1997年 | 8200篇 |
1996年 | 6501篇 |
1995年 | 4743篇 |
1994年 | 4350篇 |
1993年 | 4165篇 |
1992年 | 3313篇 |
1991年 | 3110篇 |
1990年 | 2943篇 |
1989年 | 3008篇 |
1988年 | 2888篇 |
1987年 | 2464篇 |
1986年 | 2376篇 |
1985年 | 2772篇 |
1984年 | 2555篇 |
1983年 | 2385篇 |
1982年 | 2127篇 |
1981年 | 2233篇 |
1980年 | 2049篇 |
1979年 | 2154篇 |
1978年 | 2146篇 |
1977年 | 2379篇 |
1976年 | 3206篇 |
1975年 | 1848篇 |
1974年 | 1773篇 |
1973年 | 1784篇 |
1972年 | 1451篇 |
1971年 | 1342篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Z.S. AL-Hakkak Alya M.B. Murad Afaf F. Hussain 《Journal of Stored Products Research》1985,21(3):119-121
The present study was conducted to explore the sterilizing effect of phosphine on Ephestia cautella. Three to four-day old pupae were exposed to 0, 0.007, 0.014, 0.021, 0.028, 0.035, 0.042 and 0.049 mg/l of phosphine for 24 h at room temperature. The normally developed adults of each treatment were pair mated and several physiological and genetical parameters were investigated. The results showed gradual increases with dose in pupal mortality and adult malformation. The crossing results showed no changes in adult longevity and mating frequency. However, consistent reduction was noted in the fecundity and fertility of normally emerged adults. Preliminary data indicated similar levels of inherited sterility in the F1 adults raised from the above mentioned crosses. 相似文献
942.
943.
944.
Protsko L.B. Sorenson P.G. Tremblay J.P. Schaefer D.A. 《IEEE transactions on pattern analysis and machine intelligence》1991,17(1):10-21
The authors formulate the criteria for drawing dataflow diagrams and describe the placement and routing algorithms used in a system called MONDRIAN. A generalized approach to the question of software diagrams is proposed based on the authors' experience with MONDRIAN and a metasystem approach to the creation of CASE (computer-aided software engineering) environments. A formal approach to the definition of software objects and their graphical representation is given. The use of location constraints as a basis for generalized layout algorithms is discussed 相似文献
945.
946.
Bovine mammary tissue was collected by surgical biopsy at intervals during involution for histological and ultrastructural observation. In lactating tissue (d 0 of involution, collected 8 h after the final milking), alveolar epithelial cells had marked ultrastructural evidence of lactation, including protein-containing secretory vesicles, lipid droplets, extensive rough endoplasmic reticulum, and numerous mitochondria. By d 2 of involution, alveolar epithelial cells contained large vacuoles apparently formed by coalescing of protein-containing secretory vesicles and lipid droplets. Large vacuoles were observed in epithelial cells until about the 3rd wk of involution. By d 2 of involution, the Golgi apparatus generally was not apparent. Rough endoplasmic reticulum and mitochondria were observed throughout the period studied, although in reduced amounts compared with their presence in lactating tissue. A marked increase in lysosomal or cytosegresomal structures in epithelial cells was not observed. There was no evidence of extensive sloughing of epithelial cells from the basement membrane. There was a progressive increase in the interalveolar area and a concurrent decrease in the alveolar luminal area as involution progressed. Ultrastructural examination showed that alveolar epithelial cells at d 21 and 30 of involution appear to be functionally active but not secreting milk components. 相似文献
947.
948.
Lyashenko B. A. Soroka E. B. Rutkovskii A. V. Lipinskaya N. V. 《Strength of Materials》2002,34(4):402-406
The authors suggest that the dimensions of a discrete section of a coating should be chosen on the basis of calculation of the critical crack spacing in cohesion cracking. This approach allows for residual stresses in the coating. The reliability of the calculation method has been verified experimentally by direct measurement of the crack spacing. 相似文献
949.
A. T. Mamadalimov B. L. Oksegendler Sh. O. Otazhonov B. É. Turaev T. A. Usmanov N. K. Khakimova Zh. A. Kadirov 《Technical Physics Letters》2002,28(7):581-583
The photoelectric properties of cotton fibers treated with iodine were studied in the fundamental absorption range. The samples exhibit a sublinear illumination-current characteristic and a long-term relaxation of photoconductivity (PC) after UV irradiation (hν=5 eV) of the iodine-doped fibers. A PC mechanism is proposed which explains both the nonlinear variation of photocurrent with illumination intensity and the PC decay according to a bimolecular recombination law after UV irradiation of the iodine-doped fiber in the fundamental absorption range. 相似文献
950.
A RKHS interpolator-based graph matching algorithm 总被引:1,自引:0,他引:1
van Wyk M.A. Durrani T.S. van Wyk B.J. 《IEEE transactions on pattern analysis and machine intelligence》2002,24(7):988-995
We present an algorithm for performing attributed graph matching. This algorithm is derived from a generalized framework for describing functionally expanded interpolators which is based on the theory of reproducing kernel Hilbert spaces (RKHS). The algorithm incorporates a general approach to a wide class of graph matching problems based on attributed graphs, allowing the structure of the graphs to be based on multiple sets of attributes. No assumption is made about the adjacency structure of the graphs to be matched 相似文献