全文获取类型
收费全文 | 73032篇 |
免费 | 7470篇 |
国内免费 | 4631篇 |
专业分类
电工技术 | 3362篇 |
技术理论 | 8篇 |
综合类 | 9043篇 |
化学工业 | 9845篇 |
金属工艺 | 5275篇 |
机械仪表 | 4070篇 |
建筑科学 | 12318篇 |
矿业工程 | 3108篇 |
能源动力 | 1792篇 |
轻工业 | 2545篇 |
水利工程 | 2429篇 |
石油天然气 | 2108篇 |
武器工业 | 875篇 |
无线电 | 4009篇 |
一般工业技术 | 9216篇 |
冶金工业 | 4941篇 |
原子能技术 | 464篇 |
自动化技术 | 9725篇 |
出版年
2024年 | 308篇 |
2023年 | 1115篇 |
2022年 | 1758篇 |
2021年 | 2245篇 |
2020年 | 2347篇 |
2019年 | 2099篇 |
2018年 | 2194篇 |
2017年 | 2718篇 |
2016年 | 2808篇 |
2015年 | 2864篇 |
2014年 | 4267篇 |
2013年 | 5031篇 |
2012年 | 4929篇 |
2011年 | 5316篇 |
2010年 | 4079篇 |
2009年 | 4222篇 |
2008年 | 4136篇 |
2007年 | 4639篇 |
2006年 | 4301篇 |
2005年 | 3733篇 |
2004年 | 3086篇 |
2003年 | 2590篇 |
2002年 | 2265篇 |
2001年 | 1876篇 |
2000年 | 1618篇 |
1999年 | 1432篇 |
1998年 | 1129篇 |
1997年 | 952篇 |
1996年 | 812篇 |
1995年 | 736篇 |
1994年 | 599篇 |
1993年 | 512篇 |
1992年 | 431篇 |
1991年 | 300篇 |
1990年 | 268篇 |
1989年 | 273篇 |
1988年 | 180篇 |
1987年 | 114篇 |
1986年 | 106篇 |
1985年 | 85篇 |
1984年 | 82篇 |
1983年 | 59篇 |
1982年 | 69篇 |
1981年 | 47篇 |
1980年 | 47篇 |
1979年 | 45篇 |
1978年 | 30篇 |
1977年 | 26篇 |
1964年 | 30篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
71.
Jorge Soriano-Santos† Setsuko Iwabuchi Kenshiro Fujimoto 《International Journal of Food Science & Technology》1992,27(3):337-346
Nitrogen was extracted more efficiently from amaranth seed with 0.04 M Na2 SO4 (5% w/v) than with either 0.09 M or 0.17 M NaCl (5% or 10% w/v), despite both solutions having the same ionic strength (μ= 1). Solubility of saline soluble proteins (albumin ± globulin) was very poor in either water or 1M NaCl, but increased in 0.4M NaCl at alkaline pH between 7 and 10. Globulins were very soluble in 0.4M NaCl at a pH 9. Albumin was the main storage protein. Saline soluble proteins formed very weak gels. 相似文献
72.
本文基于弹塑性分叉理论研究单向纤维增强复合材料的压缩破坏模式和压缩强度对缺陷的敏感性问题。对于常见复合材料,所得结论是:无缺陷或者小缺陷情况的破坏模式为倾斜破坏带;大缺陷情况的破坏模式为水平破坏带;形成水平破坏带的压力值小于形成倾斜破坏带的压力。 相似文献
73.
Reviews the book, The concept of structure in psychoanalysis by Theodore Shapiro (see record 1991-97355-000). The present volume is a hardcover edition of a previous supplement to the Journal of the American Psychoanalytic Association based on a series of panels presented at meetings of the American on the role of the concept of structure in current psychoanalytic theory and practice. The result can be taken as a more or less authoritative expression of current thinking about structure in orthodox analytic circles. As such, the volume is informative and in many regards thought provoking. But if readers are looking for a coherent, consistent, and consensually endorsed presentation of the idea of structure, or for a uniform conceptualization of the nature of psychic structure and its role in psychoanalytic praxis, they will have to look elsewhere. The volume is more remarkable for its diversity and often contradictory views on the nature of structure and the relevance of structure to clinical work in the analytic setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
According to D. E. Broadbent's (1958) selective filter theory, people do not process unattended stimuli beyond the analysis of basic physical properties. This theory was later rejected on the basis of numerous findings that people identify irrelevant (and supposedly unattended) stimuli. A careful review of this evidence, however, reveals strong reasons to doubt that these irrelevant stimuli were in fact unattended. This review exposed a clear need for new experiments with tight control over the locus of attention. The authors present 5 such experiments using a priming paradigm. When steps were taken to ensure that irrelevant stimuli were not attended, these stimuli produced no priming effects. Hence, the authors found no evidence that unattended stimuli can be identified. The results support a modern version of Broadbent's selective theory, updated to reflect recent research advances. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
Evaluating Liquefaction Strength of Partially Saturated Sand 总被引:1,自引:0,他引:1
A method is presented for evaluating the liquefaction strength of partially saturated sand using the compression wave velocity (P-wave velocity), a new indicator of saturation. Based on laboratory test results, an empirical correlation that relates the liquefaction strength with the pore pressure coefficient B is firstly proposed. The strength is defined as the cyclic stress ratio required to cause liquefaction at a specified number of cycles. With the aid of a theoretical relation between B and the P-wave velocity, an explicit correlation of more interest is then established between the liquefaction strength of sand and its P-wave velocity. A comparison of the predictions using this explicit correlation with laboratory measurements shows a satisfactory agreement. The significance of this method lies in that it makes it possible to evaluate the liquefaction strength of sand as affected by saturation through the measurement of P-wave velocity, which can be made not only in the laboratory but particularly in the field. 相似文献
76.
The authors study residual stresses in and cyclic strength of shaft with overlapping zones formed during roller burnishing.
The most significant decrease in fatigue strength is shown to occur in the presence of an overlapping zone with the areas
arising due to a lowered roller burnishing pressure in the second pass.
__________
Translated from Problemy Prochnosti, No. 3, pp. 144–148, May–June, 2006. 相似文献
77.
Tsuyoshi Takahashi Masahito Kitou Michio Asai Mitsuyasu Kido Tomio Chiba Junzou Kawakami Yoshiaki Matsui 《Electrical Engineering in Japan》1994,114(2):18-33
Power system control equipment needs higher sensitivity and operational reliability. Advanced voltage control equipment is needed for reducing the frequency of tap changes and improving the characteristics (the relationship between the actual voltage and reference voltage) of the voltage to meet today's power system requirements. However, these objectives are in a trade-off relationship. Studies of voltage control derived from a knowledge base suitable for electric power systems can satisfy these objectives using fuzzy inference. Compared with corresponding conventional equipment, the new equipment improved the deviation of 30 min average voltage of 30 percent. This paper describes the design concept of new voltage control equipment using fuzzy inference. In addition, field test results are described along with rules of fuzzy inference, membership functions, and the deviation of 30 min average voltage through detailed simulation. 相似文献
78.
Nanoadhesives of epoxy resin are synthesized and evaluated. They are organically modified by multiwalled carbon nanotubes (MWCNT) (1% by weight) as reinforcement. Tensile tests are conducted on multiple identical unnotched and notched specimens to evaluate the overloading and fracture behavior of the nanoadhesives and are compared with the neat epoxy resin. In comparison with the neat epoxy, it is found that the 1% MWCNT reinforcement increased the ultimate and residual strength by about 29% and 56%, respectively. In comparison with the neat resin, there is a 265% increase in the fracture toughness of the MWCNT adhesive. Fracture surface analysis revealed the various mechanisms by which the MWCNT adhesives acquire their superior strength and toughness in comparison with the neat resin. 相似文献
79.
The authors propose a behavioral decision theory relevant to the maintenance of desirable identities. The theory, termed deviance regulation theory (DRT), predicts that actions translate into meaningful identities to the extent that they cause the individual to deviate from reference group norms. This straightforward proposition is used to predict the patterning of behavior across a wide array of social contexts. The authors present evidence that predictions generalize across Eastern and Western cultures and to both personal and collective identities. Finally, they show how DRT alters current theoretical assumptions about social motives and social and cultural influence, and they illustrate how it can help explain the structure of both informal and formal social forces. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.