全文获取类型
收费全文 | 4522篇 |
免费 | 155篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 44篇 |
综合类 | 6篇 |
化学工业 | 965篇 |
金属工艺 | 45篇 |
机械仪表 | 110篇 |
建筑科学 | 354篇 |
矿业工程 | 12篇 |
能源动力 | 132篇 |
轻工业 | 468篇 |
水利工程 | 50篇 |
石油天然气 | 11篇 |
武器工业 | 1篇 |
无线电 | 294篇 |
一般工业技术 | 681篇 |
冶金工业 | 601篇 |
原子能技术 | 26篇 |
自动化技术 | 879篇 |
出版年
2023年 | 31篇 |
2022年 | 46篇 |
2021年 | 66篇 |
2020年 | 54篇 |
2019年 | 80篇 |
2018年 | 91篇 |
2017年 | 91篇 |
2016年 | 108篇 |
2015年 | 74篇 |
2014年 | 143篇 |
2013年 | 311篇 |
2012年 | 200篇 |
2011年 | 308篇 |
2010年 | 213篇 |
2009年 | 218篇 |
2008年 | 224篇 |
2007年 | 230篇 |
2006年 | 187篇 |
2005年 | 180篇 |
2004年 | 134篇 |
2003年 | 107篇 |
2002年 | 126篇 |
2001年 | 73篇 |
2000年 | 86篇 |
1999年 | 80篇 |
1998年 | 91篇 |
1997年 | 87篇 |
1996年 | 92篇 |
1995年 | 58篇 |
1994年 | 53篇 |
1993年 | 54篇 |
1992年 | 50篇 |
1991年 | 37篇 |
1990年 | 35篇 |
1989年 | 42篇 |
1988年 | 33篇 |
1987年 | 42篇 |
1986年 | 38篇 |
1985年 | 39篇 |
1984年 | 51篇 |
1983年 | 47篇 |
1982年 | 44篇 |
1981年 | 38篇 |
1980年 | 40篇 |
1979年 | 34篇 |
1978年 | 29篇 |
1977年 | 22篇 |
1976年 | 31篇 |
1975年 | 31篇 |
1973年 | 19篇 |
排序方式: 共有4679条查询结果,搜索用时 15 毫秒
1.
2.
3.
Ian G. Richardson Adrian R. Brough Rik Brydson Geoffrey W. Groves Christopher M. Dobson 《Journal of the American Ceramic Society》1993,76(9):2285-2288
Solid-state 27 Al and 29 Si magic angle spinning NMR spectroscopy has been combined with electron energy loss spectroscopy carried out in the transmission electron microscope to determine the location of Al substituting in a semicrystalline C-S-H gel present in a hydrated synthetic slag glass. The gel is found to contain mainly pentameric silicate chains in which the central silicon is substituted by aluminum. 相似文献
4.
Ian Haywood 《Cities》1985,2(3):186-197
Khartoum is the capital of a country whose creation resulted more from colonial politicians' desires for straight boundaries than from local social or political realities. This profile traces Khartoum's history of growth and planning legislation since its establishment as an administrative capital at the turn of the century. The city, developed from three separate towns, grew rapidly after independence as administrative functions grew and industrial development started. However, lack of an effective mechanism for planning and control of the city's growth has meant that a pattern of sprawling low-density land uses has developed, with inadequate services and deteriorating environmental standards. What planning control does exist operates through land-use zoning and building byelaws, though often arbitrarily applied. Planning problems are exacerbated by high population growth rates and national economic problems. 相似文献
5.
Lewinsohn Peter M.; Roberts Robert E.; Seeley John R.; Rohde Paul; Gotlib Ian H.; Hops Hyman 《Canadian Metallurgical Quarterly》1994,103(2):302
In a prospective study of adolescent depression, adolescents (N?=?1,508) were assessed at Time 1 and after 1 yr (Time 2) on psychosocial variables hypothesized to be associated with depression. Most psychosocial variables were associated with current (n?=?45) depression. Formerly depressed adolescents (n?=?217) continued to differ from never depressed controls on many of the psychosocial variables. Many of the depression-related measures also acted as risk factors for future depression (n?=?112), especially past depression, current other mental disorders, past suicide attempt, internalizing behavior problems, and physical symptoms. Young women were more likely to be, to become, and to have been depressed. Controlling for the psychosocial variables eliminated the gender difference for current and future but not for past depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
Terasa Kubala Baldev Gambhir S. Ian Borst 《Drug development and industrial pharmacy》1993,19(7):749-757
A high performance liquid chromatography method is described for the determination of diclofenac sodium, its related compounds and degradation products in commercial sources of raw materials and solid dosage forms. This method is specific, accurate and stability indicating. The method employs a reverse-phase octylsilane (C18) column with a mobile phase composed of acetonitrile/methanol/pic B-6 (25:25:50) and detection at 229 nm. The method resolves six principal related compounds with quantitation in the range 0.3-1.5%. Assay recoveries by spiking commercial formulations with diclofenac sodium were 99.64 ± 1.30%. Drug content in several commercial formulations are reported. Accelerated stability tests were conducted on raw materials and drug products and 1-(2,6-dichlorophenyl)-2-indolin-2-one was identified for the first time as a degradation product in solid dosage forms which are stressed under humidity and heat. 相似文献
7.
The inhibition of Ca2+ channel currents by endogenous brain steroids was examined in freshly dissociated pyramidal neurons from the adult guinea pig hippocampal CA1 region. The steady-state inhibition of the peak Ca2+ channel current evoked by depolarizing steps from -80 to -10 mV occurred in a concentration-dependent manner with the following IC50 values: pregnenolone sulfate (PES), 11 nM; pregnenolone (PE), 130 nM; and allotetrahydrocorticosterone (THCC), 298 nM. THCC, PE, and PES depressed a fraction of the Ca2+ channel current with a maximal inhibition of 60% of the total current. However, substitution of an acetate group for the sulfate group on PES resulted in a complete loss of activity. Progesterone had no effect (4% inhibition at 100 microM). Intracellular dialysis of PES had no effect on the Ca2+ current; concomitant extracellular perfusion of PES showed normal inhibitory activity, suggesting that the steroid binding site can only be accessed extracellularly. Analysis of tail currents at -80 mV demonstrated that THCC and PES slowed the rate of Ca2+ current activation and deactivation with no change in the voltage dependence of activation. Inhibition of the Ca2+ channel current by THCC and PES was voltage dependent. THCC primarily inhibits the omega-conotoxin (CgTX)-sensitive or N-type Ca2+ channel current. PE was nonselective in inhibiting both the CgTX- and the nifedipine (NIF)-sensitive Ca2+ channel current. These neurosteroids had no effect on the CgTX/NIF-insensitive current. In neurons isolated from pertussis toxin (PTX)-treated animals by chronic intracerebroventricular infusion (1000 ng/24 hr for 48 hr), the Ca2+ channel current inhibition by PES, PE, and THCC was significantly diminished. Intracellular dialysis with GDP-beta-S (500 microM) also significantly diminished the neurosteroid inhibition of the Ca2+ channel current. Intracellular dialysis with the general kinase inhibitors H-7 (100 microM), staurosporine (400 nM), and a 20 amino acid protein kinase inhibitor (1 microM) also significantly prevented the THCC and PES inhibition of the Ca2+ channel current. Intracellular dialysis with the more specific inhibitors of protein kinase C (PKC), the pseudosubstrate inhibitor (PKCI 19-36) (1-2 microM) and bisindolylmaleimide (1 microM) significantly diminished the THCC and PE inhibition of the Ca2+ channel current. Rp- cAMP (100 microM), a specific inhibitor of cAMP-dependent protein kinase (PKA), had no effect on the THCC and PE inhibition of the Ca2+ current.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
8.
9.
Research has continued in the field sidechain liquid crystal polymers over recent years, but it is becoming clearer that this research is being directed away from the traditional technology areas of electro-optic devices and researchers are developing new and exciting applications for this novel state of matter. 相似文献
10.
Salvatore A. Bruno Donald K. Swanson Ian Burn 《Journal of the American Ceramic Society》1993,76(5):1233-1241
Advantages of chemically prepared powders for electronic ceramics have been demonstrated for a number of multilayer capacitor (MLC) dielectrics. A cost-efficient precipitation process was developed to produce undoped or doped crystalline barium titanate powder with a narrow particle size distribution close to 0.5 μm. More complex compositions, e.g., barium-neodymium titanate, were amorphous as precipitated but could be crystallized by calcination below 1000°C. Additional compositional modifications, to adjust electrical properties or to lower sintering temperature, were accomplished by doping the surface of the powder particles using a solution coating process. Exceptional fired densities and electrical performance were obtained. 相似文献