全文获取类型
收费全文 | 1623036篇 |
免费 | 28196篇 |
国内免费 | 7074篇 |
专业分类
电工技术 | 34894篇 |
综合类 | 6503篇 |
化学工业 | 277135篇 |
金属工艺 | 65981篇 |
机械仪表 | 46073篇 |
建筑科学 | 48618篇 |
矿业工程 | 11668篇 |
能源动力 | 50568篇 |
轻工业 | 127904篇 |
水利工程 | 16292篇 |
石油天然气 | 38012篇 |
武器工业 | 150篇 |
无线电 | 199723篇 |
一般工业技术 | 302817篇 |
冶金工业 | 222815篇 |
原子能技术 | 34376篇 |
自动化技术 | 174777篇 |
出版年
2021年 | 15696篇 |
2020年 | 12070篇 |
2019年 | 14832篇 |
2018年 | 18131篇 |
2017年 | 17495篇 |
2016年 | 22671篇 |
2015年 | 17701篇 |
2014年 | 28953篇 |
2013年 | 88429篇 |
2012年 | 38620篇 |
2011年 | 53044篇 |
2010年 | 45064篇 |
2009年 | 52739篇 |
2008年 | 48872篇 |
2007年 | 46632篇 |
2006年 | 47238篇 |
2005年 | 42412篇 |
2004年 | 44112篇 |
2003年 | 43779篇 |
2002年 | 42426篇 |
2001年 | 39804篇 |
2000年 | 37860篇 |
1999年 | 37947篇 |
1998年 | 63649篇 |
1997年 | 50437篇 |
1996年 | 42717篇 |
1995年 | 35117篇 |
1994年 | 32333篇 |
1993年 | 32229篇 |
1992年 | 27326篇 |
1991年 | 24571篇 |
1990年 | 24776篇 |
1989年 | 23882篇 |
1988年 | 22476篇 |
1987年 | 20570篇 |
1986年 | 20027篇 |
1985年 | 23366篇 |
1984年 | 22948篇 |
1983年 | 20939篇 |
1982年 | 19739篇 |
1981年 | 19946篇 |
1980年 | 18551篇 |
1979年 | 18966篇 |
1978年 | 18171篇 |
1977年 | 18972篇 |
1976年 | 21614篇 |
1975年 | 16293篇 |
1974年 | 15795篇 |
1973年 | 15886篇 |
1972年 | 13375篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
892.
893.
Tissue engineered grafts show great potential as regenerative implants for diseased or injured tissues within the human body. However, these grafts suffer from poor nutrient perfusion and waste transport, thus decreasing their viability post-transplantation. Graft vascularization is therefore a major area of focus within tissue engineering because biologically relevant conduits for nutrient and oxygen perfusion can improve viability post-implantation. Many researchers used microphysiological systems as testing platforms for potential grafts owing to an ability to integrate vascular networks as well as biological characteristics such as fluid perfusion, 3D architecture, compartmentalization of tissue-specific materials, and biophysical and biochemical cues. Although many methods of vascularizing these systems exist, microvascular self-assembly has great potential for bench-to-clinic translation as it relies on naturally occurring physiological events. In this review, the past decade of literature is highlighted, and the most important and tunable components yielding a self-assembled vascular network on chip are critically discussed: endothelial cell source, tissue-specific supporting cells, biomaterial scaffolds, biochemical cues, and biophysical forces. This paper discusses the bioengineered systems of angiogenesis, vasculogenesis, and lymphangiogenesis and includes a brief overview of multicellular systems. It concludes with future avenues of research to guide the next generation of vascularized microfluidic models. 相似文献
894.
Dr. Vlastimil Jirasko Dr. Nils-Alexander Lakomek Dr. Susanne Penzel Dr. Marie-Laure Fogeron Prof. Dr. Ralf Bartenschlager Prof. Dr. Beat H. Meier Dr. Anja Böckmann 《Chembiochem : a European journal of chemical biology》2020,21(10):1453-1460
Proton-detected 100 kHz magic-angle-spinning (MAS) solid-state NMR is an emerging analysis method for proteins with only hundreds of microgram quantities, and thus allows structural investigation of eukaryotic membrane proteins. This is the case for the cell-free synthesized hepatitis C virus (HCV) nonstructural membrane protein 4B (NS4B). We demonstrate NS4B sample optimization using fast reconstitution schemes that enable lipid-environment screening directly by NMR. 2D spectra and relaxation properties guide the choice of the best sample preparation to record 2D 1H-detected 1H,15N and 3D 1H,13C,15N correlation experiments with linewidths and sensitivity suitable to initiate sequential assignments. Amino-acid-selectively labeled NS4B can be readily obtained using cell-free synthesis, opening the door to combinatorial labeling approaches which should enable structural studies. 相似文献
895.
Rahul Sasidharan Pillai Matteo Frasnelli Vincenzo M. Sglavo 《Ceramics International》2018,44(2):1328-1333
The present work focuses on the fabrication of βTCP (β-tricalcium phosphate) and HA/βTCP (hydroxyapatite/β-tricalcium phosphate) composite coatings by plasma spraying. The starting powders were produced via solid-state method using 2 wt% MgO to stabilize βTCP phase. The synthesized powders were preliminarily granulated to be used by the plasma spray process. Coatings obtained on titanium substrates are uniform and well adherent but due to the high temperature and cooling rate typical for plasma spraying process, βTCP phase is almost totally transformed into the α allotrope. Thermal treatment at 800 °C allows the reconversion of the phase αTCP→ βTCP. It is therefore possible to produce coatings with tuneable dissolution properties by selecting the proper initial powder mixture and the specific thermal treatment. 相似文献
896.
Crossover designs are an extremely useful tool to investigators, and group sequential methods have proven highly proficient at improving the efficiency of parallel group trials. Yet, group sequential methods and crossover designs have rarely been paired together. One possible explanation for this could be the absence of a formal proof of how to strongly control the familywise error rate in the case when multiple comparisons will be made. Here, we provide this proof, valid for any number of initial experimental treatments and any number of stages, when results are analyzed using a linear mixed model. We then establish formulae for the expected sample size and expected number of observations of such a trial, given any choice of stopping boundaries. Finally, utilizing the four-treatment, four-period TOMADO trial as an example, we demonstrate that group sequential methods in this setting could have reduced the trials expected number of observations under the global null hypothesis by over 33%. 相似文献
897.
898.
899.
Prof. Michael Murray Dr. Ariane Roseblade Dr. Yongjuan Chen Kirsi Bourget Dr. Tristan Rawling 《ChemMedChem》2020,15(2):247-255
Targeting the tumor cell mitochondrion could produce novel anticancer agents. We designed an aryl−urea fatty acid ( 1 g ; 16({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}amino)hexadecanoic acid) that disrupted the mitochondrion and decreased MDA-MB-231 breast cancer cell viability. To optimize the aryl−ureas the present study evaluated mitochondrial targeting by 1 g analogues containing alkyl chains between 10–17 carbons. Using the dye JC-1, the C12−C17 analogues efficiently disrupted the mitochondrial membrane potential (IC50s 3.5±1.2 to 7.6±1.1 μM) and impaired ATP production; shorter analogues were less active. 7-Aminoactinomycin D/annexin V staining and flow cytometry showed that these agents activated the killing mechanisms of necrosis and apoptosis to varying extents (7-aminoactinomycin D/annexin V staining ratios 4.3–6.0). Indeed, 1 g and its C17 analogue preferentially activated necrosis and apoptosis, respectively (ratios 2.1 and 16). Taken together, alkyl chain length is a determinant of mitochondrial targeting by aryl−ureas and can be varied to develop analogues that activate apoptosis or necrosis in a regulated fashion. 相似文献
900.
The solvent-dependent polymorphism of the active pharmaceutical ingredient (API) carbamazepine is interpreted from calculations of the solid-state and API-solvent intermolecular interactions. These simulations suggested that apolar solute-solute interactions could be disrupted by apolar solvents. In contrast, the polar solute-solute interactions were found to be easily disrupted by polar and protic solvents. This is consistent with experimental observations that the crystallization of the metastable form II is more dominant in apolar solvents. The Mercury program remains the gold standard in terms of usability; however, further expansion into more complex simulation techniques could make this package of even greater use in pharmaceutical manufacturing workflows. 相似文献