全文获取类型
收费全文 | 6230篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 112篇 |
金属工艺 | 14篇 |
机械仪表 | 15篇 |
建筑科学 | 18篇 |
矿业工程 | 2篇 |
能源动力 | 22篇 |
轻工业 | 73篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 15篇 |
一般工业技术 | 77篇 |
冶金工业 | 5844篇 |
自动化技术 | 55篇 |
出版年
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 14篇 |
2014年 | 31篇 |
2013年 | 29篇 |
2012年 | 19篇 |
2011年 | 21篇 |
2010年 | 29篇 |
2009年 | 26篇 |
2008年 | 27篇 |
2007年 | 23篇 |
2006年 | 16篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 18篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 190篇 |
1998年 | 1926篇 |
1997年 | 1103篇 |
1996年 | 711篇 |
1995年 | 380篇 |
1994年 | 275篇 |
1993年 | 359篇 |
1992年 | 42篇 |
1991年 | 43篇 |
1990年 | 53篇 |
1989年 | 45篇 |
1988年 | 36篇 |
1987年 | 38篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 38篇 |
1980年 | 52篇 |
1979年 | 2篇 |
1978年 | 15篇 |
1977年 | 132篇 |
1976年 | 292篇 |
1975年 | 13篇 |
1973年 | 2篇 |
1955年 | 4篇 |
排序方式: 共有6256条查询结果,搜索用时 31 毫秒
11.
AM Pollock 《Canadian Metallurgical Quarterly》1995,310(6994):1580-1584
The Association of Metropolitan Authorities has recently proposed that responsibility for the NHS should pass from health authorities to local authorities. One of the fiercest debates at the outset of the NHS was whether the hospitals should be run by local authorities. In the end the minister for health, Aneurin Bevan, decided against local democracy and in favour of a national health service. His arguments included the fact that equality of treatment could not be guaranteed if facilities varied with local finances and that even the largest authorities were not big enough to pool risks and expertise. All these arguments still apply today, and the recent changes in community care provide an insight into how a market model of local authority control might work. The changes have been accompanied by a shift from public to private sector provision and the introduction of charges for services that the NHS once provided free. As important, the willingness and ability of local authorities to raise extra revenue from local taxes and charges affect the service they can provide, so leading to inequalities of provision. Local authorities have yet to make the case that they can preserve the fundamental principles and benefits of the NHS, including its reliance on central taxation and unified funding formulas. 相似文献
12.
Comparison of protein adsorption isotherms and uptake rates in preparative cation-exchange materials
Adsorption isotherms and effective diffusivities of lysozyme in a set of six preparative cation-exchange stationary phases were determined from batch uptake data in a stirred vessel. Both a pore diffusion and a homogeneous diffusion model were used in estimating diffusivities, with the isotherms fitted to a non-Langmuirian analytical isotherm equation. The capacities inferred from the isotherms are found to be correlated with the surface area accessible to lysozyme, the effective surface concentrations obtained being in agreement with values measured by different methods in various non-chromatographic systems. The pore diffusivities show systematic trends with protein and salt concentration, and effects of pore size and connectivity are also evident. Some trends in the homogeneous diffusivities are quite different to those in the pore diffusivities, but these differences largely disappear when the homogeneous diffusivities are rescaled to account for adsorption equilibrium behavior. Additional information is required to elucidate further the mechanisms of coupled diffusion and adsorption in stationary phases. 相似文献
13.
A Pierres H Feracci V Delmas AM Benoliel JP Thiery P Bongrand 《Canadian Metallurgical Quarterly》1998,95(16):9256-9261
We describe a method allowing quantitative determination of the interaction range and association rate of individual surface-attached molecules. Spherical beads (1.4 micro(m) radius) were coated with recombinant outer domains of the newly described classical type II cadherin 11, a cell adhesion molecule. Beads were driven along cadherin-coated surfaces with a hydrodynamic force of approximately 1 pN, i.e., much less than the mechanical strength of many ligand-receptor bonds. Spheres displayed periods of slow motion interspersed with arrests of various duration. Particle position was monitored with 50 Hz frequency and 0.025 micro(m) accuracy. Nearly 1 million positions were recorded and processed. Comparison between experimental and computer-simulated trajectories suggested that velocity fluctuations might be related quantitatively to Brownian motion perpendicular to the surface. The expected amplitude of this motion was of order of 100 nm. Theoretical analysis of the relationship between sphere acceleration and velocity allowed simultaneous determination of the wall shear rate and van der Waals attraction between spheres and surface. The Hamaker constant was estimated at 2.9 x 10(-23) J. The frequency of bond formation was then determined as a function of sphere velocity. Experimental data were consistent with the view that the rate of association between a pair of adhesion molecules was approximately 1.2 x 10(-3) s-1 and the interaction range was approximately 10 nm. It is concluded that the presented methodology allows sensitive measurement of sphere-to-surface interactions (with approximately 10 fN sensitivity) as well as the effective range and rate of bond formation between individual adhesion molecules. 相似文献
14.
Oligonucleotide N3'-->P5' phosphoramidates (3'-phosphoramidates) are DNA analogs that are presently under investigation as potential therapeutic agents. These compounds may also hold promise as a diagnostic tool. Here, we describe a rapid method for the analysis of single-stranded RNA fragments utilizing 3'-phosphoramidate oligonucleotides as probes in conjunction with capillary gel electrophoresis (CGE). 3'-Phosphoramidate 9-mers were mixed with complimentary RNA, and CGE was used to monitor duplex formation. Complimentary strands of RNA and 3'-phosphoramidate formed duplexes that gave unique relative mobilities based on an internal standard. The ability of CGE to discriminate between perfect duplexes and duplexes that contain a base mismatch was also investigated. However, the primary focus of this work was to determine CGE's ability to detect the presence of the 3'-phosphoramidates/RNA duplex under routine electrophoretic running conditions. Polyacrylamide gel electrophoresis analysis was utilized to verify duplex formation. 相似文献
15.
As with other forms of stress, surgery is a time of fluctuating haemodynamics, physiological shifts, intense metabolic changes, and protein catabolism and anabolism. At times, these changes can occur within hours. There is a reasonable body of literature concerning the adverse effects of surgery on gastric emptying, but not on the effects of surgery on the distribution, metabolism and excretion of drugs. Gastric emptying is diminished or absent following major procedures, which prevent the delivery of orally administered drugs to their major site of absorption, the small bowel. Changes in the paracellular absorption of drugs may occur postoperatively, although transcellular absorption appears to be unimpaired. Distribution is affected by changes in blood volume, alterations in circulation, increases in the extracellular fluid and changes in the circulating plasma protein levels, such as albumin and alpha 1-acid glycoprotein. Little is known about alterations in drug metabolism following surgery. However, it has been shown that systemic hypoxia alters the function of some of the cytochrome P450 (CYP) system and increased levels of cytokines have an effect on the metabolism of at least 1 drug. In addition, the renal elimination of drugs is affected in patients postoperatively, although the effects of biliary clearance in this period are difficult to determine. Despite the lack of research into pharmacokinetics during the postoperative period, and given the immense and often sudden changes observed in patients post-surgery, it is reasonable to recommend vigilance with respect to drug therapy during this period. 相似文献
16.
Catalysis Letters - The NdM0.25Ni0.75O3 (M?=?Cr, Fe) named NCN and NFN catalysts precursors were synthesized and characterized. The CO2 utilization in the feed was studied in the... 相似文献
17.
RG Ciocca DK Wilkerson DL Madson CT Andrew AM Graham 《Canadian Metallurgical Quarterly》1995,9(2):204-208
Congenital abnormalities of the aortic arch may lead to signs and symptoms of tracheal and esophageal obstruction secondary to a restrictive vascular ring. There are many case reports and monographs concerning the surgical management of dysphagia lusoria. This case provides the first example of long-term follow-up of surgical intervention for relief of dysphagia lusoria. A 45-year-old laborer presented with a several year history of episodic bilateral blindness and a more recent onset of "drop attacks." Notably this patient had presented at the age of 18 months with difficulty breathing and eating since birth. The patient also had frequent upper respiratory infections and episodes of pneumonia. Workup revealed a right-sided aortic arch with a left ligamentum arteriosum. When he was first seen in our clinic, history and physical examination revealed claudication and diminished pulses in the left upper extremity. Arteriography and duplex studies confirmed reversal of flow in the patient's left vertebral artery. The arteriogram demonstrated the presence of a right-sided aortic arch and descending aorta along with the proximal stump of the previously ligated left subclavian artery. He underwent left carotid to left axillary artery bypass for the treatment of symptomatic subclavian steal syndrome. His symptoms have resolved with return of antegrade vertebral flow and the presence of normal pulses in the left arm. Congenital aortic abnormalities that lead to tracheal and esophageal compromise are numerous and varied. Surgical management requires a thorough understanding of the person's anatomy and preoperative planning. The life expectancy of patients with dysphagia lusoria necessitates consideration of the long-term consequences of surgical intervention. 相似文献
18.
AM al-Senaidy 《Canadian Metallurgical Quarterly》1996,66(3):210-216
"Holistic therapy" can be just a slogan, a catchword. Two examples--the combination of behaviour therapy and pharmacotherapy on one side, the use of biofeedback in psychiatry on the other--shall present the possible integration of different therapeutic strategies into a holistic concept. The quality of different therapeutic concepts may be influenced by their possible combination. No more any therapeutic method (except some eclectic ones) can see itself as the one and only cure for everything. Of course this view has a consequence on psychopathology and diagnosis, which have to be more exact under these premisses. A holistic treatment requires more knowledge about details in psychopathology and diagnosis as well as about therapeutic methods. 相似文献
19.
This study attempted to induce a major shift in the utilization of endogenous substrates during exercise in men by the use of a potent inhibitor of adipose tissue lipolysis, Acipimox, and to see to what extent this affects the 13C/12C ratio in expired air CO2. Six healthy volunteers exercised for 3 h on a treadmill at approximately 45% of their maximum O2 uptake, 75 min after having ingested either a placebo or 250 mg Acipimox. The rise in plasma free fatty acids and glycerol was almost totally prevented by Acipimox, and no significant rise in the utilization of lipids, evaluated by indirect calorimetry, was observed. Total carbohydrate oxidation averaged 128 +/- 17 (placebo) and 182 +/- 21 g/3 h (Acipimox). Conversely, total lipid oxidation was 84 +/- 5 (placebo) and 57 +/- 6 g/3 h (Acipimox; P < 0.01). Under placebo, changes in expired air CO2 delta 13C were minimal, with only a 0.49/1000 significant rise at 30 min. In contrast, under Acipimox, the rise in expired air CO2 delta 13C averaged 1/1000 and was significant throughout the 3-h exercise bout; in these conditions calculation of a "pseudooxidation" of an exogenous sugar naturally or artificially enriched in 13C, but not ingested, would have given an erroneous value of 19.8 +/- 2.6 g/3 h. Thus under conditions of extreme changes in endogenous substrate utilization, an appropriate control experiment is mandatory when studying exogenous substrate oxidation by 13C-labeled substrates and isotope-ratio mass spectrometry measurements on expired air CO2. 相似文献
20.
Aligned multi-walled carbon nanotubes (MWCNTs) were produced with different diameters, according to the thickness of Ni catalyst layer, by microwave plasmas enhanced chemical vapor deposition, in N2/H2/CH4 environment. Raman spectroscopy, performed both on top and lateral surfaces, revealed that the relative intensity of the G′ band and the G and G′ bandwidths have high sensitivity to tube diameter distribution and also to structural variations along the tube axis. The D band present a distinct behavior: ID/IG is sensitive to structural organization, particularly along tube axis, while D bandwidth is sensitive to tube diameter distribution. This result may indicate D bandwidth as a parameter to correlate to the diameter of the aligned MWCNTs. 相似文献