全文获取类型
收费全文 | 15500篇 |
免费 | 883篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 168篇 |
综合类 | 43篇 |
化学工业 | 3343篇 |
金属工艺 | 307篇 |
机械仪表 | 315篇 |
建筑科学 | 690篇 |
矿业工程 | 45篇 |
能源动力 | 506篇 |
轻工业 | 1230篇 |
水利工程 | 124篇 |
石油天然气 | 51篇 |
无线电 | 1130篇 |
一般工业技术 | 2963篇 |
冶金工业 | 2245篇 |
原子能技术 | 117篇 |
自动化技术 | 3134篇 |
出版年
2023年 | 165篇 |
2022年 | 361篇 |
2021年 | 574篇 |
2020年 | 374篇 |
2019年 | 380篇 |
2018年 | 497篇 |
2017年 | 462篇 |
2016年 | 532篇 |
2015年 | 467篇 |
2014年 | 595篇 |
2013年 | 1062篇 |
2012年 | 975篇 |
2011年 | 1157篇 |
2010年 | 807篇 |
2009年 | 749篇 |
2008年 | 791篇 |
2007年 | 776篇 |
2006年 | 581篇 |
2005年 | 505篇 |
2004年 | 372篇 |
2003年 | 383篇 |
2002年 | 339篇 |
2001年 | 214篇 |
2000年 | 187篇 |
1999年 | 208篇 |
1998年 | 214篇 |
1997年 | 188篇 |
1996年 | 185篇 |
1995年 | 178篇 |
1994年 | 153篇 |
1993年 | 149篇 |
1992年 | 120篇 |
1991年 | 74篇 |
1990年 | 122篇 |
1989年 | 116篇 |
1988年 | 80篇 |
1987年 | 94篇 |
1986年 | 100篇 |
1985年 | 100篇 |
1984年 | 88篇 |
1983年 | 76篇 |
1982年 | 96篇 |
1981年 | 90篇 |
1980年 | 71篇 |
1979年 | 70篇 |
1978年 | 62篇 |
1977年 | 74篇 |
1976年 | 61篇 |
1975年 | 45篇 |
1974年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
891.
Although fatty acid-binding proteins (FABP) differentially affect fatty acid uptake, nothing is known regarding their role(s)
in determining cellular phospholipid levels and phospholipid fatty acid composition. The effects of liver (L)- and intestinal
(I)-FABP expression on these parameters were determined using stably transfected L-cells. Expression of L- and I-FABP increased
cellular total phospholipid mass (nmol/mg protein) 1.7- and 1.3-fold relative to controls, respectively. L-FABP expression
increased the masses of choline glycerophospholipids (ChoGpl) 1.5-fold, phosphatidylserine (PtdSer) 5.6-fold, ethanolamine
glycerophospholipids 1.4-fold, sphingomyelin 1.7-fold, and phosphatidylinositol 2.6-fold. In contrast, I-FABP expression only
increased the masses of ChoGpl and PtdSer, 1.2- and 3.1-fold, respectively. Surprisingly, both L- and I-FABP expression increased
ethanolamine plasmalogen mass 1.6- and 1.1-fold, respectively, while choline plasmalogen mass was increased 2.3- and 1.7-fold,
respectively. The increase in phospholipid levels resulted in dramatic 48 and 33% decreases in the cholesterol-to-phospholipid
ratio in L- and I-FABP expressing cells, respectively. L-FABP expression generally increased polyunsaturated fatty acids,
primarily by increasing 20∶4n−6 and 22∶6n−3, while decreasing 18∶1n−9 and 16∶1n−7. I-FABP expression generally increased only
20∶4n−6 proportions. Hence, expression of both I- and L-FABP differentially affected phospholipid mass, class composition,
and acyl chain composition. Although both proteins enhanced phospholipid synthesis, the effect of L-FABP was much greater,
consistent with previous work suggesting that these two FABP differentially affect lipid metabolism. 相似文献
892.
Daniel Foty 《Analog Integrated Circuits and Signal Processing》1999,21(3):229-252
The present state of the art in analytical MOSFET modeling for SPICE circuit simulation is reviewed, with emphasis on the circuit design usage of these models. It is noted that the model formulation represents an upper limit of what is possible from any type of model, but that good parameter extraction is required to most closely approach that limit. The individual model types presently in common use are examined, with discussion of the behavior of each model, its strengths and weaknesses, its applicability to certain types of circuits, and criteria that a circuit design consumer can employ to judge a model before using it for circuit design. Some related issues, such as node charge and gate capacitance modeling, charge conservation, and statistical simulation of process variations, are also evaluated. Finally, new trends, directions, and requirements of MOSFET modeling for circuit simulation are considered. 相似文献
893.
Spectroscopic analysis of fire suppressants and refrigerants by laser-induced breakdown spectroscopy 总被引:3,自引:0,他引:3
Laser-induced breakdown spectroscopy is evaluated as a means of detecting the fire suppressants CF(3)Br, C(3)F(7)H, and CF(4) and the refrigerant C(2)F(4)H(2). The feasibility of employing laser-induced breakdown spectroscopy for time- and space-resolved measurement of these agents during use, storage, and recharge is discussed. Data are presented that demonstrate the conditions necessary for optimal detection of these chemicals. 相似文献
894.
In this article, the authors assessed job seekers' organizational image beliefs before and after they experienced 3 recruitment media. The authors examined whether perceptions of media richness and credibility were related to improvements in the correspondence between job seekers' image beliefs and firms' projected images. Both media richness and credibility perceptions were associated with correspondence between job seekers' image beliefs and firms' projected images. However, results revealed that richness and credibility perceptions were likely to enhance job seekers' initial beliefs about firms' images when their beliefs were positive but did not diminish job seekers' beliefs about firms' images when their initial impressions were too positive. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
895.
Rodrigo Scherer Paula Rossini Augusti Vivian Caetano Bochi Camila Steffens Leadir Lucy Martins Fries Ana Paula Daniel Ernesto Hashime Kubota João Radünz Neto Tatiana Emanuelli 《Food chemistry》2006,99(1):136-142
The effect of two slaughter methods (immersion in ice-water slurry and electrical stunning followed by ice slurry asphyxiation) on chemical and microbiological parameters of grass carp (Ctenopharyngodon idella) stored in ice for 20 days was evaluated. No differences in total volatile basic nitrogen (TVB-N), pH, carbohydrate or protein content of mucus were observed between the slaughter methods. Ice-slaughtered fish had lower bacteria counts at the beginning of storage, but higher counts than fish slaughtered by electricity at the end of storage (p < 0.05). However, no significant differences in the shelf life were observed between the slaughter methods evaluated (limit of acceptability – counts > 3 × 106 CFU g−1 – attained after 13–16 days). Results indicated that the chemical parameters evaluated have a limited applicability to assess the shelf life of grass carp stored in ice, since pH limit (6.8) was exceeded after 4 days, while TVB-N limit (30 mg%) was not attained after 20 days of storage. 相似文献
896.
Daniel Gilbert 《Computational Economics》1992,5(3):iii-iii
A message from the managing editor 相似文献
897.
898.
Jean-Marie Piot Didier Guillochon Danielle Leconte Daniel Thomas 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1988,42(2):147-156
Many uses of protein hydrolysates have been developed and applied to areas such as nutritional therapy, culture media, and the isolation of biologically active peptides. All these applications need carefully controlled and characterized hydrolysates. In order to produce such a type of hydrolysate, it is possible to use haemoglobin which is a very well defined and constant protein source. Enzymic hydrolysis of haemoglobin by pepsin was carried out at pilot-plant scale in an ultrafiltration reactor with mineral membranes. The object was to obtain a reproducible, decolorized, salt-free enzymic hydrolysate. Two types of membranes were tested having 10000 dalton (M5 type) and 20000 dalton (M4 type) cut-offs. Little significant difference was observed in the final products when both types of membranes were used. Reproducibility of hydrolysates was verified by amino acid analysis and gel filtration chromatography. The haemoglobin hydrolysates produced contained more than 90% protein and are especially suitable for fine applications. 相似文献
899.
Daniel Y. C. Wei Bakhtier Farouk Diran Apelian 《Metallurgical and Materials Transactions B》1988,19(1):213-226
A numerical model is developed for the prediction of melting metal powder particles in an inductively coupled r.f. plasma
torch. The model is developed for dilute spray conditions where the gas phase flow is not affected by the loading condition.
The governing equation for the gas phase flow contains the source terms from the electromagnetic field. The theoretical calculations
have shown that particle thermal history and its velocity are greatly affected by the plasma operating conditions (i.e., carrier gas flow rate, injector location, and power level,etc.). Without the proper control of particle trajectories, particles may bounce around the fireball and exit the torch as unmelted
or resolidified solid particles. With the insertion of an injector or injecting particles with a high carrier gas flow rate,
the predictions show that even relatively small size particles can be directed into the fireball and maintained in the molten
state before they impact on the substrate. Consequently, more uniform and dense deposits can be achieved. 相似文献
900.