全文获取类型
收费全文 | 2580篇 |
免费 | 27篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 22篇 |
综合类 | 3篇 |
化学工业 | 154篇 |
金属工艺 | 15篇 |
机械仪表 | 19篇 |
建筑科学 | 10篇 |
矿业工程 | 4篇 |
能源动力 | 47篇 |
轻工业 | 36篇 |
水利工程 | 4篇 |
无线电 | 76篇 |
一般工业技术 | 167篇 |
冶金工业 | 1983篇 |
原子能技术 | 8篇 |
自动化技术 | 66篇 |
出版年
2024年 | 5篇 |
2023年 | 6篇 |
2022年 | 17篇 |
2021年 | 42篇 |
2020年 | 34篇 |
2019年 | 35篇 |
2018年 | 28篇 |
2017年 | 31篇 |
2016年 | 29篇 |
2015年 | 26篇 |
2014年 | 21篇 |
2013年 | 50篇 |
2012年 | 29篇 |
2011年 | 46篇 |
2010年 | 32篇 |
2009年 | 34篇 |
2008年 | 29篇 |
2007年 | 19篇 |
2006年 | 24篇 |
2005年 | 14篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 51篇 |
1998年 | 589篇 |
1997年 | 312篇 |
1996年 | 250篇 |
1995年 | 153篇 |
1994年 | 109篇 |
1993年 | 111篇 |
1992年 | 24篇 |
1991年 | 43篇 |
1990年 | 35篇 |
1989年 | 19篇 |
1988年 | 31篇 |
1987年 | 33篇 |
1986年 | 30篇 |
1985年 | 37篇 |
1984年 | 2篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1978年 | 5篇 |
1977年 | 30篇 |
1976年 | 106篇 |
1975年 | 7篇 |
1973年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有2614条查询结果,搜索用时 31 毫秒
191.
Basak AK; Kroone RC; Lubsen NH; Naylor CE; Jaenicke R; Slingsby C 《Protein engineering, design & selection : PEDS》1998,11(5):337-344
The 2-domain gammaS-crystallin, a highly conserved early evolutionary
off-shoot of the gamma-crystallin family, is located in the water-rich
region of eye lenses. The expressed C-terminal domain, gammaS-C, has been
crystallized and the 2.56 A X-ray structure determined. There are two
domains in the asymmetric unit which pair about a distorted twofold axis.
One of the domains has an altered conformation in a highly conserved region
of the protein, the tyrosine corner. The distorted gammaS-C dimer of
domains is compared with the highly symmetrical, equivalent recombinant
dimer of C-terminal domains from gammaB- crystallin. Sequence changes close
to the interface, that distinguish gammaS from the other gamma-crystallins,
are examined in order to evaluate their role in symmetrical domain pairing.
相似文献
192.
Preeti Gangadharan Jaya N. Sahu Bhim C. Meikap 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(10):1282-1288
BACKGROUND: Ammonia is applied to increase the efficiency of an electrostatic precipitator for fly ash removal from a flue gas stream from a boiler using fossil fuel. In the present work, the hydrolysis of urea to generate ammonia for flue gas conditioning, with the help of aluminium oxide catalyst, has been studied. RESULTS: The effect of temperature, catalyst and initial concentration on the conversion was studied. Conversion was found to increase exponentially with temperature. Addition of catalyst resulted in an increase in conversion. Experiments were conducted with different doses of catalyst, and the optimum dosage of catalyst for a particular feed concentration was determined. A decrease in conversion was observed when the initial concentration of ammonia was increased. CONCLUSION: A study of reaction kinetics showed the effect of reaction time on conversion of urea to ammonia. The catalytic hydrolysis of urea, using aluminium oxide behaved as a first‐order reaction; the rate constant at different temperatures was found, and the activation energy determined. Copyright © 2011 Society of Chemical Industry 相似文献
193.
In this work, we report electronic structure calculations aimed at computing the linear optical absorption spectrum and static
dipole polarizablity of a newly proposed boron-based planar aromatic compound borozene (B
12
H
6). For the purpose, we use the semiempirical INDO model Hamiltonian, accompanied by large-scale correlation calculations using
the multi-reference singles-doubles configuration-interaction (MRSDCI) approach. We present detailed predictions about the
energetics, polarization properties, and the nature of many-particle states contributing to various peaks in the linear absorption
spectrum. Our results can be used to characterize this material in future optical absorption experiments. We also argue that
one can deduce the aromaticity of the cluster from the optical absorption and static polarizability results. 相似文献
194.
The influence of polymer surface-protein binding affinity on protein ion signals in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is examined. The surfaces of poly(vinylidene fluoride) and poly(ethylene terephthalate) polymer substrates are modified by pulsed rf plasma deposition of allylamine. By varying the on/off duty cycle of the pulsed rf plasma, the polymer substrate surfaces are coated with thin films having varying densities of surface amine groups. The varying surface amine density is shown to lead to systematic changes in the surface binding affinity for the 125I-radiolabeled peptides angiotensin I and porcine insulin. Unlabeled angiotensin I and porcine insulin are then deposited on the pulsed rf plasma-modified substrates and analyzed by MALDI mass spectrometry. The experimental approach involves applying the peptide to the modified polymer surface in an aqueous phosphate-buffered saline solution and allowing the peptide solution to dry completely under ambient conditions. Subsequently, the MALDI matrix alpha-cyano-4-hydroxycinnamic acid in methanol and 10% trifluoroacetic acid in water are added to the peptide-coated modified polymer surfaces. The results of these studies demonstrate that, for the sample preparation method employed, increases in the surface peptide binding affinity lead to decreases in the peptide MALDI ion signal. 相似文献
195.
196.
197.
Tobias Schröder Satya Narayan Sahu Dario Anselmetti Jochen Mattay 《Israel journal of chemistry》2011,51(7):725-742
Self-assembly by H-bonding and by metal-coordination of functionalized calix[4]arenes and cavitands to large supramolecular capsules is described. In addition, a new method of analyzing supramolecular recognition processes at the single molecule level is discussed. By measuring interaction forces in a hydrogen-bonded assembly using single-molecule force spectroscopy (SMFS), the dynamics of the self-assembly process can be evaluated. In the future, consequent application of this new technique will influence supramolecular design principles and the use of non-covalent interactions as construction elements in the field of nanotechnology. 相似文献
198.
We study the buoyancy-induced interpenetration of two immiscible fluids in a tilted channel by a two-phase lattice Boltzmann method using a non-ideal gas equation of state well-suited for two incompressible fluids. The method is simple, elegant and easily parallelizable. After first validating the code for simulating Rayleigh–Taylor instabilities in a unstably-stratified flow, we applied the code to simulate the buoyancy-induced mixing in a tilted channel at various Atwood numbers, Reynolds numbers, tilt angles, and surface tension parameters. The effects of these parameters are studied in terms of the flow structures, front velocities, and velocity profiles. For one set of parameters, comparisons have also been made with results of a finite volume method. The present results are seen to agree well with those of a finite volume method in the interior of the flow; however near the boundary there is some discrepancy. 相似文献
199.
The amelioration effect of dietary high protein and vitamin C against stress was evaluated in spotted murrel, Channa punctatus, exposed to endosulfan. Two hundred and forty fish (average weight: 27.01 g/fish), distributed equally into 4 different groups (control, T1, T2, and T3), each with 6 replicates were fed with control (40% crude protein, CP and 0.1% vitamin C), T1 (40% CP and 0.1% vitamin C), T2 (50% CP and 0.1% vitamin C), and T3 (50% CP and 0.2% vitamin C) diets for 90 days. Groups fed T1, T2, and T3 diets were exposed to sublethal endosulfan concentration, whereas the control was maintained without endosulfan exposure. Results indicated significant reduction in the growth performance, survival, and activities of lactate dehydrogenase (liver and muscle), malate dehydrogenase (liver and muscle), enzymes of protein metabolism (aspartate amino transferase in liver and alanine amino transferase in liver and muscle), acetyl choline esterase (brain), alkaline phosphatase activity (liver), and ATPase (gill) enzymes of group fed control diet and exposed to endosulfan. However, endosulfan exposed fish fed high CP and vitamin C diet exhibited significant (P < 0.05) improvement in their growth performance and metabolic enzyme activities. Further, high CP and vitamin C diet reduced endosulfan accumulation in the muscle. Overall results indicate that vitamin C (0.2%) supplementation in high CP (50%) diet improves growth, metabolism, and reduce endosulfan bioaccumulation in C. punctatus. 相似文献
200.
Amidated forms of gastrin are derived by post-translational processing of a large precursor peptide and stimulate gastric acid secretion via the gastrin/CCK(B) receptor. Non-amidated biosynthetic intermediates may exert biological effects through other mechanisms, but their effect on gastric acid secretion is unclear. Amidated gastrins stimulate acid secretion mainly by releasing histamine from mucosal enterochromaffin-like cells. This study examines the effects on histamine release from the vascularly perfused rat stomach of amidated gastrin-17, COOH-terminal glycine-extended gastrin-17, gastrin-17 extended at the COOH-terminal including the remaining progastrin sequence, and carboxy-terminal progastrin fragments (SAEDEN and GRRSAEDEN). Carboxy-terminal extended gastrins induced histamine release which was inhibited by the gastrin/CCK(B) antagonist L-740,093, but had to be given in concentrations 100-fold higher than amidated gastrin-17 to produce comparable effects. These progastrin-derived peptides are found in high concentrations in some patients with the Zollinger-Ellison syndrome and may contribute to acid hypersecretion and other gastrin/CCK(B) receptor mediated responses. 相似文献