全文获取类型
收费全文 | 33275篇 |
免费 | 1335篇 |
国内免费 | 119篇 |
专业分类
电工技术 | 399篇 |
综合类 | 237篇 |
化学工业 | 7069篇 |
金属工艺 | 686篇 |
机械仪表 | 671篇 |
建筑科学 | 1098篇 |
矿业工程 | 102篇 |
能源动力 | 1066篇 |
轻工业 | 4669篇 |
水利工程 | 279篇 |
石油天然气 | 192篇 |
武器工业 | 10篇 |
无线电 | 2426篇 |
一般工业技术 | 4802篇 |
冶金工业 | 6513篇 |
原子能技术 | 252篇 |
自动化技术 | 4258篇 |
出版年
2024年 | 120篇 |
2023年 | 290篇 |
2022年 | 944篇 |
2021年 | 1241篇 |
2020年 | 725篇 |
2019年 | 748篇 |
2018年 | 852篇 |
2017年 | 937篇 |
2016年 | 877篇 |
2015年 | 687篇 |
2014年 | 1049篇 |
2013年 | 1686篇 |
2012年 | 1524篇 |
2011年 | 1873篇 |
2010年 | 1370篇 |
2009年 | 1410篇 |
2008年 | 1297篇 |
2007年 | 1141篇 |
2006年 | 920篇 |
2005年 | 955篇 |
2004年 | 996篇 |
2003年 | 895篇 |
2002年 | 868篇 |
2001年 | 746篇 |
2000年 | 582篇 |
1999年 | 577篇 |
1998年 | 2111篇 |
1997年 | 1376篇 |
1996年 | 973篇 |
1995年 | 638篇 |
1994年 | 495篇 |
1993年 | 549篇 |
1992年 | 224篇 |
1991年 | 293篇 |
1990年 | 234篇 |
1989年 | 195篇 |
1988年 | 210篇 |
1987年 | 167篇 |
1986年 | 172篇 |
1985年 | 189篇 |
1984年 | 137篇 |
1983年 | 97篇 |
1982年 | 128篇 |
1981年 | 127篇 |
1980年 | 128篇 |
1979年 | 100篇 |
1978年 | 81篇 |
1977年 | 142篇 |
1976年 | 241篇 |
1975年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Renata Cardoso Magagnin Maria Solange Gurgel de Castro Fontes Rosio Fernandez Baca Salcedo 《土木工程与建筑:英文版》2014,(12):1567-1574
This paper presents an assessment of the spatial quality of a pedestrian street located in downtown Bauru, S~o Paulo State, Brazil, from the application of some urban sustainability indicators. Multi-method was used to evaluate the thermal comfort quality of users, urban accessibility and preservation of architectural heritage. The results show that the sustainability indicators, apart from being effective tools in identifying problems, can assist local managers in decision making, planning and monitoring of pedestrian public space. These indicators contribute to a broad diagnosis of the pedestrian street and also the formulation of programs, projects and municipal policies, aimed at providing a better life quality for pedestrians. 相似文献
23.
The current study is developed based on one of the types of subgrade rupture risk suggested by Selig and Waters (1994). It aims to evaluate subgrade stability railroad, which consists of the slope stability analysis of a railway yard embankment subjected to a wagon load type gondola parked on this track. This proposed analysis was taken into consideration because there are Brazilian railroads in high deterioration level. In some of these lines the tracks are submitted to increasing amount of load every year. The adopted model slope stability to the studied railroad embankments considers the rupture on circular line. It was applied the Geoslope-Slope/W software, version 6, to the evaluation of the platform-slope system. Several situations are adopted to reach the minimum safety slope, permitting to analyze the platform stability to keep railroad traffic under adequate safety level. 相似文献
24.
25.
Ksenia Skobeleva Alexey Shalygin Elena Mikhaylova Irina Guzhova Maria Ryazantseva Elena Kaznacheyeva 《International journal of molecular sciences》2022,23(23)
Alzheimer’s disease (AD) is the most common cause of age-related dementia. Neuronal calcium homeostasis impairment may contribute to AD. Here we demonstrated that voltage-gated calcium (VGC) entry and store-operated calcium (SOC) entry regulated by calcium sensors of intracellular calcium stores STIM proteins are affected in hippocampal neurons of the 5xFAD transgenic mouse model. We observed excessive SOC entry in 5xFAD mouse neurons, mediated by STIM1 and STIM2 proteins with increased STIM1 contribution. There were no significant changes in cytoplasmic calcium level, endoplasmic reticulum (ER) bulk calcium levels, or expression levels of STIM1 or STIM2 proteins. The potent inhibitor BTP-2 and the FDA-approved drug leflunomide reduced SOC entry in 5xFAD neurons. In turn, excessive voltage-gated calcium entry was sensitive to the inhibitor of L-type calcium channels nifedipine but not to the T-type channels inhibitor ML218. Interestingly, the depolarization-induced calcium entry mediated by VGC channels in 5xFAD neurons was dependent on STIM2 but not STIM1 protein in cells with replete Ca2+ stores. The result gives new evidence on the VGC channel modulation by STIM2. Overall, the data demonstrate the changes in calcium signaling of hippocampal neurons of the AD mouse model, which precede amyloid plaque accumulation or other signs of pathology manifestation. 相似文献
26.
Roxana Nemteanu Irina Ciortescu Corina Elena Hincu Andreea Clim Liliana Gheorghe Anca Trifan Alina Plesa 《International journal of molecular sciences》2022,23(23)
Without a doubt, a majority of diseases are food-pattern-related. However, one disease stands out as an increasingly more common autoimmune-mediated enteropathy triggered by the ingestion of gluten. Celiac disease (CD) is an old disease, with changing clinical patterns, affecting any age, including infancy and adolescence, and becoming more frequent among the elderly. The gluten-free diet (GFD) has been the sole provider of clinical, serological, and histological improvement for patients with CD for more than seven decades. Nowadays, complete avoidance of dietary gluten is rarely possible because of the wide availability of wheat and other processed foods that contain even more gluten, to the detriment of gluten-free products. Undeniably, there is a definite need for replacing the burdensome GFD. An add-on therapy that could control the dietary transgressions and inadvertent gluten consumption that can possibly lead to overt CD should be considered while on GFD. Nevertheless, future drugs should be able to provide patients some freedom to self-manage CD and increase food independence, while actively reducing exposure and mucosal damage and alleviating GI symptoms. Numerous clinical trials assessing different molecules have already been performed with favorable outcomes, and hopefully they will soon be available for patient use. 相似文献
27.
Leonel Pekarek Basilio De la Torre-Escuredo Oscar Fraile-Martinez Cielo García-Montero Miguel A. Saez David Cobo-Prieto Luis G. Guijarro Jose V. Saz Patricia De Castro-Martinez Diego Torres-Carranza Tatiana Pekarek Ana Clara Carrera Melchor Alvarez-Mon Miguel A. Ortega 《International journal of molecular sciences》2022,23(23)
Osteosarcoma represents a rare cause of cancer in the general population, accounting for <1% of malignant neoplasms globally. Nonetheless, it represents the main cause of malignant bone neoplasm in children, adolescents and young adults under 20 years of age. It also presents another peak of incidence in people over 50 years of age and is associated with rheumatic diseases. Numerous environmental risk factors, such as bone diseases, genetics and a history of previous neoplasms, have been widely described in the literature, which allows monitoring a certain group of patients. Diagnosis requires numerous imaging tests that make it possible to stratify both the local involvement of the disease and its distant spread, which ominously determines the prognosis. Thanks to various clinical trials, the usefulness of different chemotherapy regimens, radiotherapy and surgical techniques with radical intent has now been demonstrated; these represent improvements in both prognosis and therapeutic approaches. Osteosarcoma patients should be evaluated in reference centres by multidisciplinary committees with extensive experience in proper management. Although numerous genetic and rheumatological diseases and risk factors have been described, the use of serological, genetic or other biomarkers has been limited in clinical practice compared to other neoplasms. This limits both the initial follow-up of these patients and screening in populations at risk. In addition, we cannot forget that the diagnosis is mainly based on the direct biopsy of the lesion and imaging tests, which illustrates the need to study new diagnostic alternatives. Therefore, the purpose of this study is to review the natural history of the disease and describe the main biomarkers, explaining their clinical uses, prognosis and limitations. 相似文献
28.
Elena Jimnez-Ortega Egle Narmontaite Beatriz Gonzlez-Prez Francisco J. Plou María Fernndez-Lobato Julia Sanz-Aparicio 《International journal of molecular sciences》2022,23(23)
Rhodotorula dairenensis β-fructofuranosidase is a highly glycosylated enzyme with broad substrate specificity that catalyzes the synthesis of 6-kestose and a mixture of the three series of fructooligosaccharides (FOS), fructosylating a variety of carbohydrates and other molecules as alditols. We report here its three-dimensional structure, showing the expected bimodular arrangement and also a unique long elongation at its N-terminus containing extensive O-glycosylation sites that form a peculiar arrangement with a protruding loop within the dimer. This region is not required for activity but could provide a molecular tool to target the dimeric protein to its receptor cellular compartment in the yeast. A truncated inactivated form was used to obtain complexes with fructose, sucrose and raffinose, and a Bis-Tris molecule was trapped, mimicking a putative acceptor substrate. The crystal structure of the complexes reveals the major traits of the active site, with Asn387 controlling the substrate binding mode. Relevant residues were selected for mutagenesis, the variants being biochemically characterized through their hydrolytic and transfructosylating activity. All changes decrease the hydrolytic efficiency against sucrose, proving their key role in the activity. Moreover, some of the generated variants exhibit redesigned transfructosylating specificity, which may be used for biotechnological purposes to produce novel fructosyl-derivatives. 相似文献
29.
30.
Sergey O. Bachurin Elena F. Shevtsova Galina F. Makhaeva Alexey Yu. Aksinenko Vladimir V. Grigoriev Tatiana V. Goreva Tatiana A. Epishina Nadezhda V. Kovaleva Natalia P. Boltneva Sofya V. Lushchekina Elena V. Rudakova Darya V. Vinogradova Pavel N. Shevtsov Elena A. Pushkareva Ludmila G. Dubova Tatiana P. Serkova Ivan M. Veselov Vladimir P. Fisenko Rudy J. Richardson 《International journal of molecular sciences》2022,23(22)
The development of multi-target-directed ligands (MTDLs) would provide effective therapy of neurodegenerative diseases (ND) with complex and nonclear pathogenesis. A promising method to create such potential drugs is combining neuroactive pharmacophoric groups acting on different biotargets involved in the pathogenesis of ND. We developed a synthetic algorithm for the conjugation of indole derivatives and methylene blue (MB), which are pharmacophoric ligands that act on the key stages of pathogenesis. We synthesized hybrid structures and performed a comprehensive screening for a specific set of biotargets participating in the pathogenesis of ND (i.e., cholinesterases, NMDA receptor, mitochondria, and microtubules assembly). The results of the screening study enabled us to find two lead compounds (4h and 4i) which effectively inhibited cholinesterases and bound to the AChE PAS, possessed antioxidant activity, and stimulated the assembly of microtubules. One of them (4i) exhibited activity as a ligand for the ifenprodil-specific site of the NMDA receptor. In addition, this lead compound was able to bypass the inhibition of complex I and prevent calcium-induced mitochondrial depolarization, suggesting a neuroprotective property that was confirmed using a cellular calcium overload model of neurodegeneration. Thus, these new MB-cycloalkaneindole conjugates constitute a promising class of compounds for the development of multitarget neuroprotective drugs which simultaneously act on several targets, thereby providing cognitive stimulating, neuroprotective, and disease-modifying effects. 相似文献