全文获取类型
收费全文 | 104221篇 |
免费 | 1352篇 |
国内免费 | 550篇 |
专业分类
化学 | 41808篇 |
晶体学 | 1059篇 |
力学 | 7462篇 |
数学 | 34371篇 |
物理学 | 21423篇 |
出版年
2023年 | 150篇 |
2022年 | 345篇 |
2021年 | 620篇 |
2020年 | 485篇 |
2019年 | 488篇 |
2018年 | 10745篇 |
2017年 | 10546篇 |
2016年 | 6772篇 |
2015年 | 1514篇 |
2014年 | 1215篇 |
2013年 | 1949篇 |
2012年 | 5649篇 |
2011年 | 12537篇 |
2010年 | 6930篇 |
2009年 | 7143篇 |
2008年 | 8334篇 |
2007年 | 10257篇 |
2006年 | 1848篇 |
2005年 | 2694篇 |
2004年 | 2767篇 |
2003年 | 3008篇 |
2002年 | 1973篇 |
2001年 | 850篇 |
2000年 | 839篇 |
1999年 | 534篇 |
1998年 | 437篇 |
1997年 | 388篇 |
1996年 | 510篇 |
1995年 | 342篇 |
1994年 | 310篇 |
1993年 | 322篇 |
1992年 | 237篇 |
1991年 | 203篇 |
1990年 | 207篇 |
1989年 | 190篇 |
1988年 | 150篇 |
1987年 | 148篇 |
1986年 | 125篇 |
1985年 | 163篇 |
1984年 | 120篇 |
1983年 | 98篇 |
1982年 | 129篇 |
1981年 | 128篇 |
1980年 | 98篇 |
1979年 | 119篇 |
1978年 | 96篇 |
1977年 | 76篇 |
1976年 | 79篇 |
1975年 | 71篇 |
1973年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
21.
Experimental Mechanics - Insufficient data are available to fully understand the effects of metal additive manufacturing (AM) defects for widespread adoption of the emerging technology.... 相似文献
22.
Solid‐state 31P NMR investigation on the status of guanine nucleotides in paclitaxel‐stabilized microtubules
下载免费PDF全文
![点击此处可从《Magnetic resonance in chemistry : MRC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ga Hyang Lee Su Young Oh Kwon Joo Yeo Taslima Ferdous Meeyeon Cho Younkee Paik 《Magnetic resonance in chemistry : MRC》2015,53(5):330-336
Microtubule dynamics is a target for many chemotherapeutic drugs. In order to understand the biochemical effects of paclitaxel on the GTPase activity of tubulin, the status of guanine nucleotides in microtubules was investigated by 31P cross‐polarization magic angle spinning (CPMAS) NMR. Microtubules were freshly prepared in vitro in the presence of paclitaxel and then lyophilized in sucrose buffer for solid‐state NMR experiments. A 31P CPMAS NMR spectrum with the SNR of 25 was successfully acquired from the lyophilized microtubule sample. The broadness of the 31P spectral lines in the spectrum indicates that the molecular environments around the guanine nucleotides inside tubulin may not be as crystalline as reported by many diffraction studies. Deconvolution of the spectrum into four spectral components was carried out in comparison with the 31P NMR spectra obtained from five control samples. The spectral analysis suggested that about 13% of the nucleotides were present as GTP and 37% as GDP in the β‐tubulin (E‐site) of the microtubules. It was found that most of the GDPs were present as GDP‐Pi complex in the microtubules, which seems to be one of the effects of paclitaxel binding. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
23.
24.
25.
26.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
27.
28.
Four kinds of red phosphorescent organic light-emitting devices were fabricated and compared to investigate the effect of interfacial layers for hole transport and electron injection. 1 nm-thick LiF in the device A and C and 1 nm-thick Cs2CO3 in the device B and D were deposited as an electron injection layer between the anode and the electron transport layer, and 5 nm-thick layer of dipyrazion[2,3-f:2′,2′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile[HATCN] was inserted as a hole transport interfacial layer between the hole injection layer and the hole transport layer only in the device C and D. Under a luminance of 1000 cd/m2, the power efficiencies were 7.6 lm/W and 8.5 lm/W in the device A and B, and 8.6 lm/W and 13.4 lm/W in the device C and D. The quantum efficiency of the device D was 15.8% under 1000 cd/m2 which was somewhat lower than those of the device A and C, but a little higher than that of the device B. The luminance of the device D was much higher than those of the other devices at a given votage. The luminance of the device D at 7 V was 23,710 cd/m2, which was 13.0, 3.4, and 4.0 times higher than those of the device A, B, and C at the same voltage, respectively. 相似文献
29.
Sung Hwan Koo Dong Jun Li Taeyeong Yun Dong Sung Choi Kyung Eun Lee Gil Yong Lee Youngtak Oh Joonwon Lim Suchithra Padmajan Sasikala Ho Jin Lee In Ho Kim Hong Ju Jung Rishabh Jain Sang Ouk Kim 《Particle & Particle Systems Characterization》2019,36(7)
Efficient water electrolysis catalyst is highly demanded for the production of hydrogen as a sustainable energy fuel. It is reported that cobalt derived nanoparticle (CoS2, CoP, CoS|P) decorated reduced graphene oxide (rGO) composite aerogel catalysts for highly active and reliable hydrogen evolution reaction electrocatalysts. 7 nm level cobalt derived nanoparticles are synthesized over graphene aerogel surfaces with excellent surface coverage and maximal expose of active sites. CoS|P/rGO hybrid aerogel composites show an excellent catalytic activity with overpotential of ≈169 mV at a current density of ≈10 mA cm?2. Accordingly, efficient charge transfer is attained with Tafel slope of ≈52 mV dec?1 and a charge transfer resistance (Rct) of ≈12 Ω. This work suggests a viable route toward ultrasmall, uniform nanoparticles decorated graphene surfaces with well‐controlled chemical compositions, which can be generally useful for various applications commonly requiring large exposure of active surface area as well as robust interparticle charger transfer. 相似文献
30.
Peter T. Smith Younghoon Kim Dr. Bahiru Punja Benke Prof. Kimoon Kim Prof. Christopher J. Chang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4932-4937
We report a supramolecular strategy for promoting the selective reduction of O2 for direct electrosynthesis of H2O2. We utilized cobalt tetraphenylporphyrin (Co-TPP), an oxygen reduction reaction (ORR) catalyst with highly variable product selectivity, as a building block to assemble the permanently porous supramolecular cage Co-PB-1(6) bearing six Co-TPP subunits connected through twenty-four imine bonds. Reduction of these imine linkers to amines yields the more flexible cage Co-rPB-1(6). Both Co-PB-1(6) and Co-rPB-1(6) cages produce 90–100 % H2O2 from electrochemical ORR catalysis in neutral pH water, whereas the Co-TPP monomer gives a 50 % mixture of H2O2 and H2O. Bimolecular pathways have been implicated in facilitating H2O formation, therefore, we attribute this high H2O2 selectivity to site isolation of the discrete molecular units in each supramolecule. The ability to control reaction selectivity in supramolecular structures beyond traditional host–guest interactions offers new opportunities for designing such architectures for a broader range of catalytic applications. 相似文献