全文获取类型
收费全文 | 30984篇 |
免费 | 1650篇 |
国内免费 | 325篇 |
专业分类
电工技术 | 609篇 |
综合类 | 552篇 |
化学工业 | 6789篇 |
金属工艺 | 685篇 |
机械仪表 | 993篇 |
建筑科学 | 1192篇 |
矿业工程 | 189篇 |
能源动力 | 881篇 |
轻工业 | 3563篇 |
水利工程 | 317篇 |
石油天然气 | 230篇 |
武器工业 | 27篇 |
无线电 | 3027篇 |
一般工业技术 | 4549篇 |
冶金工业 | 4442篇 |
原子能技术 | 215篇 |
自动化技术 | 4699篇 |
出版年
2023年 | 200篇 |
2022年 | 680篇 |
2021年 | 1130篇 |
2020年 | 590篇 |
2019年 | 708篇 |
2018年 | 755篇 |
2017年 | 780篇 |
2016年 | 832篇 |
2015年 | 707篇 |
2014年 | 1019篇 |
2013年 | 1763篇 |
2012年 | 1465篇 |
2011年 | 1759篇 |
2010年 | 1316篇 |
2009年 | 1412篇 |
2008年 | 1325篇 |
2007年 | 1285篇 |
2006年 | 1072篇 |
2005年 | 899篇 |
2004年 | 926篇 |
2003年 | 1092篇 |
2002年 | 1365篇 |
2001年 | 1140篇 |
2000年 | 711篇 |
1999年 | 643篇 |
1998年 | 1536篇 |
1997年 | 1018篇 |
1996年 | 756篇 |
1995年 | 517篇 |
1994年 | 391篇 |
1993年 | 427篇 |
1992年 | 232篇 |
1991年 | 190篇 |
1990年 | 179篇 |
1989年 | 167篇 |
1988年 | 154篇 |
1987年 | 138篇 |
1986年 | 133篇 |
1985年 | 166篇 |
1984年 | 105篇 |
1983年 | 117篇 |
1982年 | 99篇 |
1981年 | 113篇 |
1980年 | 115篇 |
1979年 | 79篇 |
1978年 | 60篇 |
1977年 | 119篇 |
1976年 | 202篇 |
1975年 | 56篇 |
1973年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 984 毫秒
21.
The n-type thermoelectric Bi1.9Lu0.1Te3 was prepared by microwave-solvothermal method and spark plasma sintering. The magnetic field and temperature dependences of transverse magnetoresistance measured within temperature 2–200 K interval allow finding the peculiarities characteristic for strongly disordered and inhomogeneous semiconductors. The first peculiarity is due to appearance of linear-in-magnetic field contribution to the total magnetoresistance reflected in a crossover from quadratic magnetoresistance at low magnetic fields to linear magnetoresistance at high magnetic fields. The linear magnetoresistance can result from the Hall resistance picked up from macroscopically distorted current paths due to local variations in stoichiometry of the compound studied. The second peculiarity is that both linear magnetoresistance magnitude and crossover field are functions of carrier mobility which is in agreement with the Parish and Littlewood model developed for disordered and inhomogeneous semiconductors. An increase in the mobility due to a decrease in temperature is accompanied by an increase in the magnetoresistance magnitude and a decrease in the crossover field. Finally, the third peculiarity is related to the remarkable deviation of the total magnetoresistance measured at various temperatures from the Kohler's rule. Presence of strong inhomogeneity and disorder in the Bi1.9Lu0.1Te3 structure concluded from the magnetoresistance peculiarities can be responsible for the remarkable reduction in the total thermal conductivity of this compound. 相似文献
22.
Scientometrics - Current knowledge on peer review consists of general formulations of its goals and micro level accounts of its practice, while journals’ attempts to guide and shape peer... 相似文献
23.
24.
25.
Maria Luisa Calabr Nayana Lazzari Giulia Rigotto Marco Tonello Antonio Sommariva 《International journal of molecular sciences》2020,21(23)
The mechanisms by which neoplastic cells disseminate from the primary tumor to metastatic sites, so-called metastatic organotropism, remain poorly understood. Epithelial–mesenchymal transition (EMT) plays a role in cancer development and progression by converting static epithelial cells into the migratory and microenvironment-interacting mesenchymal cells, and by the modulation of chemoresistance and stemness of tumor cells. Several findings highlight that pathways involved in EMT and its reverse process (mesenchymal–epithelial transition, MET), now collectively called epithelial–mesenchymal plasticity (EMP), play a role in peritoneal metastases. So far, the relevance of factors linked to EMP in a unique peritoneal malignancy such as pseudomyxoma peritonei (PMP) has not been fully elucidated. In this review, we focus on the role of epithelial–mesenchymal dynamics in the metastatic process involving mucinous neoplastic dissemination in the peritoneum. In particular, we discuss the role of expression profiles and phenotypic transitions found in PMP in light of the recent concept of EMP. A better understanding of EMP-associated mechanisms driving peritoneal metastasis will help to provide a more targeted approach for PMP patients selected for locoregional interventions involving cytoreductive surgery and hyperthermic intraperitoneal chemotherapy. 相似文献
26.
27.
Antonio Mancini Carmine Bruno Edoardo Vergani Claudia dAbate Elena Giacchi Andrea Silvestrini 《International journal of molecular sciences》2021,22(4)
The pathophysiology of Polycystic Ovary Syndrome (PCOS) is quite complex and different mechanisms could contribute to hyperandrogenism and anovulation, which are the main features of the syndrome. Obesity and insulin-resistance are claimed as the principal factors contributing to the clinical presentation; in normal weight PCOS either, increased visceral adipose tissue has been described. However, their role is still debated, as debated are the biochemical markers linked to obesity per se. Oxidative stress (OS) and low-grade inflammation (LGI) have recently been a matter of researcher attention; they can influence each other in a reciprocal vicious cycle. In this review, we summarize the main mechanism of radical generation and the link with LGI. Furthermore, we discuss papers in favor or against the role of obesity as the first pathogenetic factor, and show how OS itself, on the contrary, can induce obesity and insulin resistance; in particular, the role of GH-IGF-1 axis is highlighted. Finally, the possible consequences on vitamin D synthesis and activation on the immune system are briefly discussed. This review intends to underline the key role of oxidative stress and low-grade inflammation in the physiopathology of PCOS, they can cause or worsen obesity, insulin-resistance, vitamin D deficiency, and immune dyscrasia, suggesting an inverse interaction to what is usually considered. 相似文献
28.
Iratxe Perez-Arnedo María J. Cantalejo Alba Martínez-Laorden Elena Gonzalez-Fandos 《International Journal of Food Science & Technology》2021,56(4):1855-1864
Microbiological contamination of chicken meat depends on the conditions under which the animals are reared, slaughtered and processed. The aim of this study was to determine the influence of farm origin and processing stages at slaughterhouse on the microbial safety and quality of chicken. Samples of chicken carcasses from three different farms were taken from a slaughterhouse. Mesophiles, Escherichia coli, coagulase positive Staphylococcci counts, presence of Listeria monocytogenes,Campylobacter and Salmonella were determined at five sampling points: after defeathering, after evisceration, after washing, after chilling and after cutting. Chilling reduced log numbers of mesophiles, coagulase positive Staphylococci and E. coli by 0.85, 1.52 and 2.2 log units, respectively. Salmonella was not detected after chilling. High prevalence of Campylobacter spp was observed at all the stages ranging between 84% and 100%. L. monocytogenes was not detected in chicken carcasses after defeathering. However, it was detected after evisceration and after washing and chilling. The most critical stage for L. monocytogenes contamination was the portioning operation, the prevalence in breast and legs being 88% and 84%, respectively. 相似文献
29.
Lorenzo Zallocco Laura Giusti Maurizio Ronci Andrea Mussini Marco Trerotola Maria Rosa Mazzoni Antonio Lucacchini Laura Sebastiani 《International journal of molecular sciences》2021,22(9)
The autonomic nervous system (ANS) plays a crucial role both in acute and chronic psychological stress eliciting changes in many local and systemic physiological and biochemical processes. Salivary secretion is also regulated by ANS. In this study, we explored salivary proteome changes produced in thirty-eight University students by a test stress, which simulated an oral exam. Students underwent a relaxation phase followed by the stress test during which an electrocardiogram was recorded. To evaluate the effect of an olfactory stimulus, half of the students were exposed to a pleasant odor diffused in the room throughout the whole session. Saliva samples were collected after the relaxation phase (T0) and the stress test (T1). State anxiety was also evaluated at T0 and T1. Salivary proteins were separated by two-dimensional electrophoresis, and patterns at different times were compared. Spots differentially expressed were trypsin digested and identified by mass spectrometry. Western blot analysis was used to validate proteomic results. Anxiety scores and heart rate changes indicated that the fake exam induced anxiety. Significant changes of α-amylase, polymeric immunoglobulin receptor (PIGR), and immunoglobulin α chain (IGHA) secretion were observed after the stress test was performed in the two conditions. Moreover, the presence of pleasant odor reduced the acute social stress affecting salivary proteome changes. Therefore, saliva proteomic analysis was a useful approach to evaluate the rapid responses associated to an acute stress test also highlighting known biomarkers. 相似文献
30.