全文获取类型
收费全文 | 12535篇 |
免费 | 1360篇 |
国内免费 | 837篇 |
专业分类
电工技术 | 1139篇 |
综合类 | 1794篇 |
化学工业 | 825篇 |
金属工艺 | 304篇 |
机械仪表 | 685篇 |
建筑科学 | 1169篇 |
矿业工程 | 330篇 |
能源动力 | 404篇 |
轻工业 | 740篇 |
水利工程 | 387篇 |
石油天然气 | 667篇 |
武器工业 | 118篇 |
无线电 | 1659篇 |
一般工业技术 | 1014篇 |
冶金工业 | 976篇 |
原子能技术 | 130篇 |
自动化技术 | 2391篇 |
出版年
2024年 | 52篇 |
2023年 | 142篇 |
2022年 | 321篇 |
2021年 | 367篇 |
2020年 | 418篇 |
2019年 | 365篇 |
2018年 | 361篇 |
2017年 | 409篇 |
2016年 | 403篇 |
2015年 | 479篇 |
2014年 | 765篇 |
2013年 | 707篇 |
2012年 | 1011篇 |
2011年 | 970篇 |
2010年 | 792篇 |
2009年 | 825篇 |
2008年 | 692篇 |
2007年 | 860篇 |
2006年 | 787篇 |
2005年 | 699篇 |
2004年 | 566篇 |
2003年 | 498篇 |
2002年 | 424篇 |
2001年 | 347篇 |
2000年 | 264篇 |
1999年 | 211篇 |
1998年 | 160篇 |
1997年 | 137篇 |
1996年 | 101篇 |
1995年 | 97篇 |
1994年 | 88篇 |
1993年 | 65篇 |
1992年 | 49篇 |
1991年 | 44篇 |
1990年 | 41篇 |
1989年 | 31篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1966年 | 8篇 |
1963年 | 11篇 |
1960年 | 5篇 |
1959年 | 7篇 |
1957年 | 6篇 |
1955年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
加氢裂化反应器新型冷氢箱的研究与工程设计 总被引:6,自引:1,他引:5
报道了加氢加化反应器新型旋流式冷氢箱的研究设计及实用效果,催化剂床层径向温差不大于5℃。 相似文献
23.
Color characteristics of Cu-Zn-Al alloys 总被引:4,自引:0,他引:4
COLORCHARACTERISTICSOFCu-Zn-AlALLOYS ̄①Li,Baomian;Zhang,Xiuhua(ShenyangInstituteofGoldTechnology,Shenyang110015)COLORCHARACTER... 相似文献
24.
Although comparative judgment methods have a number of distinct advantages over ratings, they share one common problem: On the basis of comparative judgments, it is not possible to recover the origin of item evaluations. One item may be judged more positively than another, but this result does not allow any conclusions about whether either of the items are attractive or unattractive. This article discusses the implications of this limitation for the interpretation of individual differences in comparative judgments. It also presents 3 different methods that may allow determination of the scale origin using a nested model comparison approach. An application illustrates the proposed approach as well as the benefits of determining the scale origin in understanding value judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
Ken Mattsson 《Journal of scientific computing》2003,18(1):133-153
Four different methods of imposing boundary conditions for the linear advection-diffusion equation and a linear hyperbolic system are considered. The methods are analyzed using the energy method and the Laplace transform technique. Numerical calculations are done, considering in particular the case when the initial data and boundary data are inconsistent. 相似文献
26.
Simultaneous HPLC quantification of total cholesterol,tocopherols and β-carotene in Barrosã-PDO veal 总被引:1,自引:0,他引:1
José A. Mestre Prates Mário A. Gonçalves Quaresma Rui J. Branquinho Bessa Carlos M.G. Andrade Fontes Cristina M.P. Mateus Alfaia 《Food chemistry》2006
A simple, rapid and sensitive procedure for the simultaneous determination of total cholesterol, tocopherols and β-carotene in meat is described. The method involves a direct saponification of the meat, a single n-hexane extraction and the analysis of the extracted compounds by normal-phase HPLC, using fluorescence (tocopherols) and UV–Vis photodiode array (cholesterol and β-carotene) detections in tandem. Rates of recovery of spiked meat samples were 93% for cholesterol, 83–86% for (α-, β- and -γ) tocopherols and 89% for β-carotene. Repeatabilities were high (CV < 6%) for all determined compounds, except for δ-tocopherol. This tocopherol, which is not usually present in meat, showed a much lower recovery percentage (73%) and repeatability (12.8%). This methodology was applied for the quantification of total cholesterol, tocopherols and β-carotene in three muscles (longissimus thoracis, longissimus lumborum and semitendinosus) of the Portuguese traditional Barrosã-PDO veal, obtained from autochthonous calves fed extensively during summer (with the least abundant green pastures) and slaughtered in early autumn (October). Barrosã-PDO veal showed median contents of total cholesterol (0.50–0.56 mg/g) and, depending on the analysed muscle, moderate to high contents of α-tocopherol (3.3–3.9 μg/g) and β-carotene (0.07–0.09 μg/g), suggesting an high sensorial and hygienic quality. 相似文献
27.
Guimond Serge; Dambrun Micha?l; Michinov Nicolas; Duarte Sandra 《Canadian Metallurgical Quarterly》2003,84(4):697
Social dominance orientation (SDO) has been proposed as an important variable in the explanation of prejudice. We distinguish between three conceptualizations of SDO: SDO as a personality trait (personality model), SDO as a moderator of the effects of situational variables (Person X Situation model), and SDO as a mediator of the effect of social position on prejudice (group socialization model [GSM]). Four studies (N = 1,657) looking at the relations between social positions, SDO, and prejudice in a natural setting and in a laboratory setting provide strong support for the GSM. In contrast to previous correlational findings, there is evidence of a cause (dominant social position), an effect (prejudice increases), and a mediator (SDO). These results suggest new perspectives on the integration of individual and contextual determinants of prejudice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
A numerical study of the transport phenomena arising in a single-screw extruder channel is carried out. A non-Newtonian fluid
is considered, using a power law model for the variable viscosity. Chemical reaction kinetics are also included. Finite difference
computations are carried out to solve the governing set of partial differential equations for the velocity, temperature and
species concentration fields, over a wide range of governing parameters for the case of a tapered screw channel.
The numerical treatment for this combined heat and mass transfer problem is outlined. A marching procedure in the down-channel
direction is adopted and the validity of the scheme for practical problems discussed. For large viscous dissipation, the material
heats up considerably due to the prevailing shear field, affecting the viscosity significantly, and results in large changes
in the pressure development at the end of the channel. The rate of reaction controls the mass diffusion rate which in turn
affects viscosity and the flow significantly. The dimensionless throughput,q
v
, is one of the most important parameters in the numerical solution. The dimensionless pressure variation is very sensitive
toq
v
, and orders of magnitude changes are possible for small variations inq
v
. Schemes for dealing with other important effects such as back flow, heat transfer by conduction in the barrel, and the effect
of the die are also outlined.
A list of symbols is given at the end of the paper
This is publication No. F-10544-4-91 of the New Jersey Agricultural Experiment Station supported by State Funds and the Center
for Advanced Food Technology (CAFT). The Center for Advanced Food Technology is a New Jersey Commission on Science and Technology Center. This work was also
supported in part by the US Army Research Office. 相似文献
29.
本文阐述了一项水能利用的新技术:通过密闭容器将水的落差转换成压力气体,再通过压力气体去压缩另一密闭容器内的水。进而实现提水的目的。实验、计算和分析显示,这是一种切实可行的提水新技术。 相似文献
30.
Leonid Shaikhet 《Asian journal of control》2006,8(1):76-81
Some new Lyapunov type theorems for stochastic difference equations with continuous time are proven. It is shown that these theorems simplify an application of Lyapunov functionals construction method. 相似文献