全文获取类型
收费全文 | 1912篇 |
免费 | 47篇 |
专业分类
电工技术 | 30篇 |
综合类 | 2篇 |
化学工业 | 246篇 |
金属工艺 | 53篇 |
机械仪表 | 31篇 |
建筑科学 | 70篇 |
能源动力 | 36篇 |
轻工业 | 142篇 |
水利工程 | 11篇 |
无线电 | 171篇 |
一般工业技术 | 281篇 |
冶金工业 | 691篇 |
原子能技术 | 17篇 |
自动化技术 | 178篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 18篇 |
2018年 | 18篇 |
2017年 | 19篇 |
2016年 | 29篇 |
2015年 | 23篇 |
2014年 | 25篇 |
2013年 | 75篇 |
2012年 | 56篇 |
2011年 | 72篇 |
2010年 | 56篇 |
2009年 | 55篇 |
2008年 | 66篇 |
2007年 | 65篇 |
2006年 | 52篇 |
2005年 | 50篇 |
2004年 | 47篇 |
2003年 | 40篇 |
2002年 | 45篇 |
2001年 | 39篇 |
2000年 | 36篇 |
1999年 | 48篇 |
1998年 | 142篇 |
1997年 | 100篇 |
1996年 | 68篇 |
1995年 | 61篇 |
1994年 | 61篇 |
1993年 | 72篇 |
1992年 | 26篇 |
1991年 | 22篇 |
1990年 | 28篇 |
1989年 | 26篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 13篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1977年 | 19篇 |
1976年 | 42篇 |
1975年 | 17篇 |
1974年 | 11篇 |
1972年 | 10篇 |
1971年 | 9篇 |
排序方式: 共有1959条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
IG Sumner A Vaughan R Eisenthal RW Pickersgill AJ Owen PW Goodenough 《Canadian Metallurgical Quarterly》1993,1164(3):243-251
Papaya proteinase omega (pp omega) has been purified from dried latex both by immunoaffinity and traditional methods. Kinetic analysis revealed that (1), the pp omega-catalysed hydrolysis of N-benzoyl-L-arginine p-nitroanilide (BApNA) has a lower specificity (kcat/Km) than the same reaction catalysed by papain; (2), the pp omega-catalysed hydrolysis of a tripeptide substrate having phenylalanine at the second position (S2-site) showed a more similar specificity to that catalysed by papain; (3), the significant difference between the two enzymes is that steady state kinetics with both L-BApNA and a tripeptide enables the identification in pp omega of other ionizations affecting binding. The active sites of papain and pp omega can therefore be distinguished by pH-dependence of kcat/Km. 相似文献
5.
While Beck asserts that agility is only possible through greater discipline on the part of everyone involved, Boehm counters that you don't broaden the definition of "discipline" by rejecting parts of it. Yet, from inside extreme programming, it seems that the only way to achieve the desired results is to view the world in 'both-and" terms instead of "either-or" terms. 相似文献
6.
The capacity to store water in a reservoir declines as it traps sediment. A river entering a reservoir forms a prograding delta. Coarse sediment (e.g., sand) deposits in the fluvial topset and avalanching foreset of the delta, and is typically trapped with an efficiency near 100%. The trap efficiency of fine sediment (e.g., mud), on the other hand, may be below 100%, because some of this sediment may pass out of the reservoir without settling out. Here, a model of trap efficiency of mud is developed in terms of the mechanics of a turbidity current that plunges on the foreset. The dam causes a sustained turbidity current to reflect and form a muddy pond bounded upstream by a hydraulic jump. If the interface of this muddy pond rises above any vent or overflow point at the dam, the trap efficiency of mud drops below 100%. A model of the coevolution of topset, foreset, and bottomset in a reservoir that captures the dynamics of the internal muddy pond is presented. Numerical implementation, comparison against an experiment, and application to a field-scale case provide the basis for a physical understanding of the processes that determine reservoir trap efficiency. 相似文献
7.
8.
Berninger Virginia W.; Vaughan Katherine; Abbott Robert D.; Brooks Allison; Abbott Sylvia P.; Rogan Laura; Reed Elizabeth; Graham Steve 《Canadian Metallurgical Quarterly》1998,90(4):587
Poor spellers in 2nd grade (n?=?128) participated in 24 20-min sessions that included (a) direct instruction in the alphabet principle (most frequent phoneme-spelling connections); (b) modeling of different approaches, singly and in combination, for developing connections between spoken and written words for 48 words ordered by sound-spelling predictability; and (c) practice in composing. Results of this multilayered intervention showed that (a) more than 1 way of developing sound-spelling connections is effective in teaching spelling but that after training in the alphabet principle, combining whole word and onset-rime training is most effective in achieving transfer of the alphabet principle across word contexts; (b) functional spelling units of not only a single letter but also 2 or more letters are important in beginning spelling; and (c) training in spelling transfers to composition and word recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
A sensitive method for measurement of the volume of blood flow through the skin, based on the kinetics of reheating after localised cooling, is described in this paper. This method has been used to study the tuberculin reaction as a model of cutaneous delayed-type hypersensitivity (DHS) in man. Over the positive reaction there is accelerated reheating similar in kinetics and extent to that seen after maximal hyperaemia induced by intradermal injection of histamine or prostaglandin E2. The earlier phase of reheating (10-100 s) is more dependent on blood flow, whereas the later phase (100-300 s) is apparently more dependent on non-perfusion heat exchange mechanisms, including conduction. The reheat kinetic method is largely dependent on blood flow in the deep dermal vessels (diameter > 50 microns), whereas the alternative approach of measurement of the velocity of flow of erythrocytes in the microcirculation by laser Doppler (LD) flowmetry gives results biased towards the most superficial dermal circulation. Previous studies with LD flowmetry have shown that the blood velocity is greatest at the centre of weak and strong reactions, while in the most intense reactions it is raised at the centre but maximal at the periphery (central relative slowing, CRS) raising the possibility of central ischaemia. The reheat kinetics approach has now indicated that the deep dermal circulation is not impaired in CRS reactions. It is concluded that there must be partial obstruction of the parts of the microcirculation communicating between the deep and superficial dermal plexuses, presumably from the accumulation of exudate oedema in the most intense tuberculin reactions. 相似文献
10.
The choice of a highly resistive substrate for silicon millimeter-wave integrated circuits (SIMMWIC) imposed by the requirement of low RF-substrate losses requires the adaptation of a CMOS process on float zone silicon (FZ). A comparison of n- and p-channel devices realized on high resistivity substrate (p-type, 5000 Ω·cm) and standard CMOS substrates (CZ, n-type, 4-6 Ω·cm) is given. Using careful process design, we obtained device characteristics on FZ-substrates that are closely similar to those on standard material, thus allowing direct transfer of existing circuit designs 相似文献