全文获取类型
收费全文 | 2645篇 |
免费 | 154篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 50篇 |
综合类 | 7篇 |
化学工业 | 722篇 |
金属工艺 | 67篇 |
机械仪表 | 67篇 |
建筑科学 | 171篇 |
矿业工程 | 2篇 |
能源动力 | 57篇 |
轻工业 | 215篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 238篇 |
一般工业技术 | 532篇 |
冶金工业 | 223篇 |
原子能技术 | 14篇 |
自动化技术 | 428篇 |
出版年
2022年 | 23篇 |
2021年 | 55篇 |
2020年 | 37篇 |
2019年 | 50篇 |
2018年 | 51篇 |
2017年 | 70篇 |
2016年 | 72篇 |
2015年 | 81篇 |
2014年 | 96篇 |
2013年 | 139篇 |
2012年 | 118篇 |
2011年 | 175篇 |
2010年 | 115篇 |
2009年 | 119篇 |
2008年 | 132篇 |
2007年 | 121篇 |
2006年 | 106篇 |
2005年 | 85篇 |
2004年 | 69篇 |
2003年 | 72篇 |
2002年 | 51篇 |
2001年 | 51篇 |
2000年 | 54篇 |
1999年 | 44篇 |
1998年 | 80篇 |
1997年 | 59篇 |
1996年 | 51篇 |
1995年 | 37篇 |
1994年 | 30篇 |
1993年 | 32篇 |
1992年 | 25篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 27篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 27篇 |
1985年 | 23篇 |
1984年 | 24篇 |
1983年 | 19篇 |
1982年 | 16篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 20篇 |
1978年 | 22篇 |
1977年 | 26篇 |
1976年 | 21篇 |
1975年 | 14篇 |
1974年 | 15篇 |
1973年 | 14篇 |
排序方式: 共有2801条查询结果,搜索用时 15 毫秒
121.
CeO2 samples doped with 10, 1.0, and 0.1 mol% Y2 O3 and undoped CeO2 samples of high purity were studied by impedance spectroscopy at temperatures <800°C and under various oxygen partial pressures. According to microstructural investigations by SEM and analytical STEM (equipped with EDXS), the grain boundaries were free of any second phase, providing direct grain-to-grain contacts. An amorphous siliceous phase was detected at only a few triple junctions, if at all; as a result, its contribution to the grain-boundary resistance was negligible. Nevertheless, the specific grain-boundary conductivities were still 2–7 orders of magnitude lower than the bulk conductivities, depending on dopant concentration, temperature, and oxygen partial pressure. The charge carrier transport across the grain boundaries occurred only through the grain-to-grain contacts, whose properties were then determined by the space-charge layer. The space-charge potential in acceptor-doped CeO2 was positive, causing the simultaneous depletion of oxygen vacancies and accumulation of electrons in the space-charge layer. The very low grain-boundary conductivities can be accounted for by the oxygen-vacancy depletion; the accumulation of electrons became evident in weakly doped and undoped CeO2 at high temperatures and under low oxygen partial pressures. 相似文献
122.
Thomas Diemant Zhong Zhao Hubert Rauscher Joachim Bansmann R. Jürgen Behm 《Topics in Catalysis》2007,44(1-2):83-93
The interaction of CO with structurally well-defined, planar Au/TiO2 model catalysts at elevated pressures (up to 50 mbar) was studied in-situ by polarization-modulated infrared reflection absorption spectroscopy and ex-situ by X-ray photoelectron spectroscopy performed before and after CO exposure. The results indicate a CO-induced partial reduction
of the oxide surface, which is evidenced by a low frequency C–O vibration at 2060 cm−1, combined with a spreading of the Au nanoparticles due to a modification of the Au-oxide interface energy. In a 2:1 CO:O2 atmosphere, TiO2 support reduction was not observed, and a pre-reduced surface was re-oxidized. The consequences of these results for the
understanding of the CO oxidation mechanism on Au/TiO2 (model) catalysts are discussed. 相似文献
123.
Development of Diaminoquinazoline Histone Lysine Methyltransferase Inhibitors as Potent Blood‐Stage Antimalarial Compounds
下载免费PDF全文
![点击此处可从《ChemMedChem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Sandeep Sundriyal Dr. Nicholas A. Malmquist Dr. Joachim Caron Scott Blundell Dr. Feng Liu Xin Chen Nitipol Srimongkolpithak Prof. Jian Jin Prof. Susan A. Charman Prof. Artur Scherf Dr. Matthew J. Fuchter 《ChemMedChem》2014,9(10):2360-2373
Modulating epigenetic mechanisms in malarial parasites is an emerging avenue for the discovery of novel antimalarial drugs. Previously we demonstrated the potent in vitro and in vivo antimalarial activity of (1‐benzyl‐4‐piperidyl)[6,7‐dimethoxy‐2‐(4‐methyl‐1,4‐diazepin‐1‐yl)‐4‐quinazolinyl]amine (BIX01294; 1 ), a known human G9a inhibitor, together with its dose‐dependent effects on histone methylation in the malarial parasite. This work describes our initial medicinal chemistry efforts to optimise the diaminoquinazoline chemotype for antimalarial activity. A variety of analogues were designed by substituting the 2 and 4 positions of the quinazoline core, and these molecules were tested against Plasmodium falciparum (3D7 strain). Several analogues with IC50 values as low as 18.5 nM and with low mammalian cell toxicity (HepG2) were identified. Certain pharmacophoric features required for antimalarial activity were found to be analogous to the previously published SAR of these analogues for G9a inhibition, thereby suggesting potential similarities between the malarial and human HKMT targets of this chemotype. Physiochemical, in vitro activity, and in vitro metabolism studies were also performed for a select set of potent analogues to evaluate their potential as antimalarial leads. 相似文献
124.
Chandolia RK Luetjens CM Wistuba J Yeung CH Nieschlag E Simoni M 《Reproduction (Cambridge, England)》2006,132(2):355-363
Data on pubertal maturation in male marmoset, a model for human reproduction, are scant and conflicting. We collected data on novel parameters to characterize puberty. Twenty-five marmoset monkeys were assigned to five age groups by weeks (wk): 21 (pre-pubertal), 43 (onset of puberty), 52 (fully pubertal), 70 (mature), and 116 (fully adult). Serum and intratesticular testosterone and pituitary bioactive chorionic gonadotropin (bioCG) were measured. Testicular development was assessed by ultrasonography, histology, and flow cytometry. Three consecutive blood samples revealed extreme fluctuations in testosterone concentrations, suggesting an erratic secretion. Age-related changes in serum testosterone and pituitary bioCG concentrations were observed. Intratesticular androgens (ITAs) showed high fluctuations within groups at all ages and were high in some animals by 21 wk. Unexpectedly, no correlation between pituitary bioCG and serum testosterone or ITAs was found, but these parameters significantly correlated with testicular weight and volume. These observations were consistent a dependence on the testis growth on bioCG. Unfortunately, the low serum levels of bioCG were not measurable in this study. At 43 wk, the animals reached puberty. At 52 wk of age, animals attained maximum body and epididymal weights and qualitatively normal spermatogenesis, but testes continued growing, reaching a maximum of all parameters at 70 wk of age, without further major changes at the age of 116 wk. It is concluded that (1) gonadal activation is evident at wk 21, (2) the male marmoset reaches the pubertal threshold around 43 wk of age, attains qualitative parameters at 52 wk, matures further to sexual maturity at 70 wk, and (3) serum testosterone and ITAs are highly variable without any identifiable correlation with pituitary bioCG. 相似文献
125.
Kollmann Immel Holdheide M. Antonoff H. Mayer-Wegelin Frey-Wyssling Eidmann Thiele J. S. Cammerer A. v. Wacek Klauditz Scheer A. Nowak Gumz Vorreiter Finkbeiner Müller Munds E. Becker A. Kraus Fessel Keylwerth A. Troche Graf B. Thunell Tiemann Bäseler 《Holz als Roh- und Werkstoff》1942,5(10):363-371
Ohne Zusammenfassung 相似文献
126.
Fessel Thiele Egner A. Troche Kraemer F. Wachholiz W. Wenharl 《Holz als Roh- und Werkstoff》1941,4(5):196-197
Ohne Zusammenfassung 相似文献
127.
Ohne Zusammenfassung 相似文献
128.
v. Pohl R. Trendelenburg Zimmermann E. Brüche S. Nickel Zycha Liese Schulz Graf A. Troche T. Perkitny M. Lüdtke Frey-Wyssling K. Storch Otto Kratky A. v. Wacek Finkbeiner K. Storch Munds Paula Sarten Ernst Tschanter A. Kraus R. Lechner Schaile Thiele W. Küch Kräß Hengerer Kollmann A. Nowak 《Holz als Roh- und Werkstoff》1940,3(4):128-136
Ohne Zusammenfassung 相似文献
129.
R. Trendelenburg Frey-Wyssling O. Kratky Gertraude Körner-Hennig Egner v. Pohl M. Lüdtke K. Storch Klar Zimmermann B. Thunell L. Metz Thiele Kollmann W. Wenhart A. Troche 《Holz als Roh- und Werkstoff》1940,3(6):202-207
Ohne Zusammenfassung 相似文献
130.
Kräß af Ekenstam R. Trendelenburg Zeller Frey-Wyssling M. Wolf G. Becker Liese Thienhaus Graf A. Troche A. v. Wacek O. Kratky M. Lüdtke Gustav G. Klem Schulz K. Storch Müller E. Becker Klauditz K. Nising A. Nowak L. Metz Egner Fessel Thiele Kraemer Lehnartz Kaiser Tiemann B. Thunell 《Holz als Roh- und Werkstoff》1940,3(11):383-393
Ohne Zusammenfassung 相似文献