全文获取类型
收费全文 | 9251篇 |
免费 | 560篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 133篇 |
综合类 | 18篇 |
化学工业 | 2367篇 |
金属工艺 | 170篇 |
机械仪表 | 208篇 |
建筑科学 | 357篇 |
矿业工程 | 36篇 |
能源动力 | 230篇 |
轻工业 | 407篇 |
水利工程 | 70篇 |
石油天然气 | 28篇 |
无线电 | 790篇 |
一般工业技术 | 2336篇 |
冶金工业 | 982篇 |
原子能技术 | 111篇 |
自动化技术 | 1589篇 |
出版年
2024年 | 65篇 |
2023年 | 190篇 |
2022年 | 374篇 |
2021年 | 459篇 |
2020年 | 336篇 |
2019年 | 246篇 |
2018年 | 302篇 |
2017年 | 255篇 |
2016年 | 350篇 |
2015年 | 297篇 |
2014年 | 440篇 |
2013年 | 553篇 |
2012年 | 548篇 |
2011年 | 624篇 |
2010年 | 424篇 |
2009年 | 413篇 |
2008年 | 433篇 |
2007年 | 420篇 |
2006年 | 324篇 |
2005年 | 253篇 |
2004年 | 223篇 |
2003年 | 201篇 |
2002年 | 191篇 |
2001年 | 122篇 |
2000年 | 113篇 |
1999年 | 120篇 |
1998年 | 193篇 |
1997年 | 157篇 |
1996年 | 106篇 |
1995年 | 84篇 |
1994年 | 74篇 |
1993年 | 90篇 |
1992年 | 54篇 |
1991年 | 50篇 |
1990年 | 52篇 |
1989年 | 37篇 |
1988年 | 45篇 |
1987年 | 42篇 |
1986年 | 34篇 |
1985年 | 42篇 |
1984年 | 37篇 |
1983年 | 32篇 |
1982年 | 27篇 |
1981年 | 27篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 28篇 |
1977年 | 25篇 |
1976年 | 60篇 |
1975年 | 27篇 |
排序方式: 共有9832条查询结果,搜索用时 0 毫秒
11.
Massimiliano Cazzaniga Giordano Bruno Zonzini Francesco Di Pierro Sara Moricoli Alexander Bertuccioli 《International journal of molecular sciences》2022,23(20)
Metabolic disorders, mainly characterized as the marked alteration of the lipid and carbohydrate profile, in addition to the clinical presence of the direct consequences of these alterations, are pathological conditions that have considerably increased in prevalence in recent years. They are directly linked to the onset of various pathologies, including cancer, particularly breast cancer, and are hormone-responsive. Alongside the known conditions responsible for this scenario, such as nutrition and lifestyle in general, the importance of both the colonic microbiota and the various organs and systems is becoming increasingly evident. In fact, it is now evident that microbial dysbiosis plays a fundamental role in the onset of these metabolic disorders, and therefore how these conditions are indirectly responsible for the onset and progression of neoplasms. Indirect mechanisms such as an altered Firmicutes/Bacteroidetes ratio; the formation of metabolites such as short-chain fatty acids (SCFAs), in particular, butyrate, which is capable of acting as a tumor suppressor; and the glucuronidase activity of estroboloma (bacteria responsible for estrogen metabolism) are just some of the most important mechanisms that contribute to the history of breast cancer. It is therefore understandable that in clinical terms, it is essential to associate the modulation of metabolic disorders and the microbial conditions that contribute to generating them with common therapies, preferably using compounds and solutions that are effective and acceptable for the patient without side effects. Nutraceuticals such as berberine (active both in metabolic scenarios and in the microbiota) and interventions modulating the microbial structure such as the use of probiotics and prebiotics seem to be ideal solutions for these preventive and no-longer-ignorable strategies in the light of numerous data now present in the literature. 相似文献
12.
Ekaterina M. Dvorianinova Nadezhda L. Bolsheva Elena N. Pushkova Tatiana A. Rozhmina Alexander A. Zhuchenko Roman O. Novakovskiy Liubov V. Povkhova Elizaveta A. Sigova Daiana A. Zhernova Elena V. Borkhert Dmitry N. Kaluzhny Nataliya V. Melnikova Alexey A. Dmitriev 《International journal of molecular sciences》2022,23(21)
High-quality genome sequences help to elucidate the genetic basis of numerous biological processes and track species evolution. For flax (Linum usitatissimum L.)—a multifunctional crop, high-quality assemblies from Oxford Nanopore Technologies (ONT) data were unavailable, largely due to the difficulty of isolating pure high-molecular-weight DNA. This article proposes a scheme for gaining a contiguous L. usitatissimum assembly using Nanopore data. We developed a protocol for flax nuclei isolation with subsequent DNA extraction, which allows obtaining about 5 μg of pure high-molecular-weight DNA from 0.5 g of leaves. Such an amount of material can be collected even from a single plant and yields more than 30 Gb of ONT data in two MinION runs. We performed a comparative analysis of different genome assemblers and polishers on the gained data and obtained the final 447.1-Mb assembly of L. usitatissimum line 3896 genome using the Canu—Racon (two iterations)—Medaka combination. The genome comprised 1695 contigs and had an N50 of 6.2 Mb and a completeness of 93.8% of BUSCOs from eudicots_odb10. Our study highlights the impact of the chosen genome construction strategy on the resulting assembly parameters and its eligibility for future genomic studies. 相似文献
13.
Alexander Beletskiy Ekaterina Positselskaya Aliya Kh. Vinarskaya Yulia S. Spivak Yulia V. Dobryakova Iliya Tyulenev Vladimir A. Markevich Alexey P. Bolshakov 《International journal of molecular sciences》2022,23(17)
We performed RNA sequencing of the dorsal and ventral parts of the hippocampus and compared it with previously published data to determine the differences in the dorsoventral gradients of gene expression that may result from biological or technical variability. Our data suggest that the dorsal and ventral parts of the hippocampus differ in the expression of genes related to signaling pathways mediated by classical neurotransmitters (glutamate, GABA, monoamines, etc.) as well as peptide and Wnt ligands. These hippocampal parts also diverge in the expression of axon-guiding molecules (both receptors and ligands) and splice isoforms of genes associated with intercellular signaling and cell adhesion. Furthermore, analysis of differential expressions of genes specific for astrocytes, microglia, oligodendrocytes, and vascular cells suggests that non-neuronal cells may also differ in the characteristics between hippocampal parts. Analysis of expression of transposable elements showed that depletion of ribosomal RNA strongly increased the representation of transposable elements in the RNA libraries and helped to detect a weak predominance of expression of these elements in the ventral hippocampus. Our data revealed new molecular dimensions of functional differences between the dorsal and ventral hippocampus and points to possible cascades that may be involved in the longitudinal organization of the hippocampus. 相似文献
14.
Elena Mikhalchik Liliya Yu. Basyreva Sergey A. Gusev Oleg M. Panasenko Dmitry V. Klinov Nikolay A. Barinov Olga V. Morozova Alexander P. Moscalets Liliya N. Maltseva Lyubov Yu. Filatova Evgeniy A. Pronkin Julia A. Bespyatykh Nadezhda G. Balabushevich 《International journal of molecular sciences》2022,23(18)
Nano- and microparticles enter the body through the respiratory airways and the digestive system, or form as biominerals in the gall bladder, salivary glands, urinary bladder, kidney, or diabetic pancreas. Calcium, magnesium, and phosphate ions can precipitate from biological fluids in the presence of mucin as hybrid nanoparticles. Calcium carbonate nanocrystallites also trap mucin and are assembled into hybrid microparticles. Both mucin and calcium carbonate polymorphs (calcite, aragonite, and vaterite) are known to be components of such biominerals as gallstones which provoke inflammatory reactions. Our study was aimed at evaluation of neutrophil activation by hybrid vaterite–mucin microparticles (CCM). Vaterite microparticles (CC) and CCM were prepared under standard conditions. The diameter of CC and CCM was 3.3 ± 0.8 µm and 5.8 ± 0.7 µm, with ƺ-potentials of −1 ± 1 mV and −7 ± 1 mV, respectively. CC microparticles injured less than 2% of erythrocytes in 2 h at 1.5 mg mL−1, and no hemolysis was detected with CCM; this let us exclude direct damage of cellular membranes by microparticles. Activation of neutrophils was analyzed by luminol- and lucigenin-dependent chemiluminescence (Lum-CL and Luc-CL), by cytokine gene expression (IL-6, IL-8, IL-10) and release (IL-1β, IL-6, IL-8, IL-10, TNF-α), and by light microscopy of stained smears. There was a 10-fold and higher increase in the amplitude of Lum-CL and Luc-CL after stimulation of neutrophils with CCM relative to CC. Adsorption of mucin onto prefabricated CC microparticles also contributed to activation of neutrophil CL, unlike mucin adsorption onto yeast cell walls (zymosan); adsorbed mucin partially suppressed zymosan-stimulated production of oxidants by neutrophils. Preliminary treatment of CCM with 0.1–10 mM NaOCl decreased subsequent activation of Lum-CL and Luc-CL of neutrophils depending on the used NaOCl concentration, presumably because of the surface mucin oxidation. Based on the results of ELISA, incubation of neutrophils with CCM downregulated IL-6 production but upregulated that of IL-8. IL-6 and IL-8 gene expression in neutrophils was not affected by CC or CCM according to RT2-PCR data, which means that post-translational regulation was involved. Light microscopy revealed adhesion of CC and CCM microparticles onto the neutrophils; CCM increased neutrophil aggregation with a tendency to form neutrophil extracellular traps (NETs). We came to the conclusion that the main features of neutrophil reaction to mucin–vaterite hybrid microparticles are increased oxidant production, cell aggregation, and NET-like structure formation, but without significant cytokine release (except for IL-8). This effect of mucin is not anion-specific since particles of powdered kidney stone (mainly calcium oxalate) in the present study or calcium phosphate nanowires in our previous report also activated Lum-CL and Luc-CL response of neutrophils after mucin sorption. 相似文献
15.
Vladimir Burmistrov Christophe Morisseau Denis A. Babkov Tatiana Golubeva Dmitry Pitushkin Elena V. Sokolova Vladimir Vasipov Yaroslav Kuznetsov Sergey V. Bazhenov Uliana S. Novoyatlova Nikolay A. Bondarev Ilya V. Manukhov Victoria Osipova Nadezhda Berberova Alexander A. Spasov Gennady M. Butov Bruce D. Hammock 《International journal of molecular sciences》2022,23(18)
The inhibitory potency of the series of inhibitors of the soluble epoxide hydrolase (sEH) based on the selenourea moiety and containing adamantane and aromatic lipophilic groups ranges from 34.3 nM to 1.2 μM. The most active compound 5d possesses aliphatic spacers between the selenourea group and lipophilic fragments. Synthesized compounds were tested against the LPS-induced activation of primary murine macrophages. The most prominent anti-inflammatory activity, defined as a suppression of nitric oxide synthesis by LPS-stimulated macrophages, was demonstrated for compounds 4a and 5b. The cytotoxicity of the obtained substances was studied using human neuroblastoma and fibroblast cell cultures. Using these cell assays, the cytotoxic concentration for 4a was 4.7–18.4 times higher than the effective anti-inflammatory concentration. The genotoxicity and the ability to induce oxidative stress was studied using bacterial lux-biosensors. Substance 4a does not exhibit genotoxic properties, but it can cause oxidative stress at concentrations above 50 µM. Put together, the data showed the efficacy and safety of compound 4a. 相似文献
16.
Alexander D. Volodin Alexander F. Smolyakov Alexander A. Korlyukov 《International journal of molecular sciences》2022,23(16)
The structure, thermodynamic parameters, and the character of thermal motion in octamethylcyclotetrasiloxane (D4) were investigated using the combination of experimental (single-crystal X-ray diffraction, thermochemistry) and theoretical (density functional theory calculations, ab initio molecular dynamics and metadynamics) methods. Single crystals of D4 were grown in a glass capillary in situ and the structures of high- (238–270 K) and low-temperature (100–230 K) phases were studied in detail. In the temperature interval 230–238 K, a phase transition with rather low enthalpy (−1.04(7) kcal/mol) was detected. It was found that phase transition is accompanied by change of conformation of cyclosiloxane moiety from boat-saddle (cradle) to chair. According to PBE0/6-311G(d,p) calculation of isolated D4, such conformation changes are characterized by a low barrier (0.07 kcal/mol). The character of molecular thermal motion and the path of phase transition were established with combination of periodic DFT calculations, including molecular dynamics and metadynamics. The effect of crystal field led to an increase in the calculated phase transition barrier (4.27 kcal/mol from low- to high-temperature phase and 3.20 kcal/mol in opposite direction). 相似文献
17.
18.
Assuming from a consideration of silicate minerals that aluminum should replace silicon in silicates, the authors investigated the system Na2O-CaO-SiO2-Al2O3. Densities and refractive indices have been determined and molecular refractions have been calculated. Partial molecular refractivities of Al2O3 indicate a coordination number of 4 for aluminum and deviate appreciably from values for compounds in which aluminum has a coordination number of 6. Interionic distances have been calculated for Si—O and Al—O. As a result of these studies, it is concluded that the aluminum atom isomorphously replaces the silicon atom in the random fetrahedral network. With this replacement, Ca++ can increasingly replace Na+ in the interstices of the open structure. 相似文献
19.
A disk of barium titanate was fired to 1350°C. for six hours in an electric furnace. Silvered electrodes were then fired on the disk at 650°C. A cathode-ray oscillograph measurement was made of the dielectric properties in order to analyze the whole charging and discharging cycle. The material showed saturation of the dielectric flux density or charge with increase of field strength or voltage and is therefore a new type of ferroelectric material. The dielectric properties of such a nonlinear circuit element was studied over a temperature range from –175° to +140°C. at field strengths of 59, 134,234, 580, and 4300 volts per cm. Peaks in the dielectric constant were observed near –70°, +10°, and 120°C. As the field strength was increased, the two lower peaks increased in magnitude and all peaks shifted slightly to lower temperature. 相似文献
20.
Maurice L. Huggins K.uan-Ran Sun Alexander Silverman 《Journal of the American Ceramic Society》1943,26(12):393-398
The difficulty of defining the vitreous state in a rigorous manner, the existence of many borderline cases, and the theoretical requirements which must be met if a substance is to be vitreous are discussed. Silicate glasses and certain other typical classes of vitreous substances are treated in some detail with especial reference to the relation between their structures and vitreous properties. 相似文献