全文获取类型
收费全文 | 20411篇 |
免费 | 983篇 |
国内免费 | 101篇 |
专业分类
化学 | 13073篇 |
晶体学 | 120篇 |
力学 | 420篇 |
数学 | 2894篇 |
物理学 | 3404篇 |
无线电 | 1584篇 |
出版年
2023年 | 138篇 |
2022年 | 178篇 |
2021年 | 310篇 |
2020年 | 424篇 |
2019年 | 431篇 |
2018年 | 281篇 |
2017年 | 269篇 |
2016年 | 646篇 |
2015年 | 594篇 |
2014年 | 701篇 |
2013年 | 1084篇 |
2012年 | 1189篇 |
2011年 | 1318篇 |
2010年 | 787篇 |
2009年 | 735篇 |
2008年 | 1096篇 |
2007年 | 1081篇 |
2006年 | 1008篇 |
2005年 | 924篇 |
2004年 | 832篇 |
2003年 | 695篇 |
2002年 | 651篇 |
2001年 | 349篇 |
2000年 | 323篇 |
1999年 | 309篇 |
1998年 | 270篇 |
1997年 | 259篇 |
1996年 | 291篇 |
1995年 | 276篇 |
1994年 | 243篇 |
1993年 | 232篇 |
1992年 | 215篇 |
1991年 | 186篇 |
1990年 | 189篇 |
1989年 | 184篇 |
1988年 | 162篇 |
1987年 | 135篇 |
1986年 | 120篇 |
1985年 | 175篇 |
1984年 | 173篇 |
1983年 | 134篇 |
1982年 | 159篇 |
1981年 | 165篇 |
1980年 | 141篇 |
1979年 | 145篇 |
1978年 | 166篇 |
1977年 | 127篇 |
1976年 | 108篇 |
1975年 | 121篇 |
1974年 | 96篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Martin Breugst 《Nachrichten aus der Chemie》2015,63(12):1180-1183
993.
Residual stresses are important by the manufacturing of the most components. The analysis of residual stresses using the hole-drilling method is complicated and is based at the moment solely on strain measurement on the surface. Now, an approach is described where the residual stresses can be calculated on the basis of strain measured in several plains. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
994.
Andrea Thom Tim Ricken Joachim Bluhm Renatus Widmann Martin Denecke Tobias Gehrke 《PAMM》2015,15(1):433-434
To simulate the processes of methane oxidation in landfill cover layers, a new computational model was created. The purpose of the model is to allow a forecast on the performance of methanotrophic activity in landfill cover layers under changing environmental conditions. Therefore, a thermodynamic consistent model based on the well-known Theory of Porous Media (TPM) combined with the mixture theory was developed, which analyzes the relevant gas productions of methane, oxygen and carbon dioxide. Diffusion, advection and conversion processes are considered as well as the energy production during methane oxidation. With the help of the thermal imaging technique a new experimental setup was developed in order to validate the coupled model in terms of the heat generation. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
995.
In this contribution main aspects of material characterization and modelling of a curing adhesive are denoted. It is pointed out how to deal with the exothermic heat generation during curing, both, how to obtain it experimentally as well as how to account for it in the continuum mechanical an FE-modelling framework. Furthermore, a strategy to simulate spatially graded gelation processes in ANSYS® is presented. An academic simulation example completes this work. By the help of this simulation tool a better understanding of a novel manufacturing process of smart semi-finished light weight structures is ensured. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
996.
Petr Tůma Martin Jaček Blanka Sommerová Pavel Dlouhý Radka Jarošíková Jitka Husáková Veronika Wosková Vladimíra Fejfarová 《Electrophoresis》2022,43(11):1129-1139
Determination of the broad-spectrum antibiotics amoxicilline (AMX) and ceftazidime (CTZ) in blood serum and microdialysates of the subcutaneous tissue of the lower limbs is performed using CE with contactless conductivity detection (C4D). Baseline separation of AMX is achieved in 0.5 M acetic acid as the background electrolyte and separation of CTZ in 3.2 M acetic acid with addition of 13% v/v methanol. The CE-C4D determination is performed in a 25 µm capillary with suppression of the EOF using INST-coating on an effective length of 18 cm and the attained migration time is 4.2 min for AMX and 4.4 min for CTZ. The analysis was performed using 20 µl of serum and 15 µl of microdialysate, treated by the addition of acetonitrile in a ratio of 1/3 v/v and the sample is injected into the capillary using the large volume sample stacking technique. The LOQ attained in the microdialysate is 148 ng/ml for AMX and 339 ng/ml for CTZ, and in serum 143 ng/ml for AMX and 318 ng/ml for CTZ. The CE-C4D method is employed for monitoring the passage of AMX and CTZ from the blood circulatory system into the subcutaneous tissue at the sites of diabetic ulceration in patients suffering from diabetic foot syndrome and also for measuring the pharmacokinetics following intravenous application of bolus antibiotic doses. 相似文献
997.
Vrbková Eva Sekerová Lada Vyskočilová Eliška Zapletal Martin Červený Libor 《Research on Chemical Intermediates》2022,48(4):1403-1421
Research on Chemical Intermediates - Several types of modified zeolite BETA38 with different iron loading were prepared. Prepared materials were characterized using different techniques (XRD, XRF,... 相似文献
998.
Dr. Ádám Eördögh Annabell Martin Prof. Dr. Pablo Rivera-Fuentes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202832
Single-molecule localization microscopy (SMLM) can reveal nanometric details of biological samples, but its high phototoxicity hampers long-term imaging in live specimens. A significant part of this phototoxicity stems from repeated irradiations that are necessary for controlled switching of fluorophores to maintain the sparse labeling of the sample. Lower phototoxicity can be obtained using fluorophores that blink spontaneously, but controlling the density of single-molecule emitters is challenging. We recently developed photoregulated fluxional fluorophores (PFFs) that combine the benefits of spontaneously blinking dyes with photocontrol of emitter density. These dyes, however, were limited to imaging acidic organelles in live cells. Herein, we report a systematic study of PFFs that culminates in probes that are functional at physiological pH and operate at longer wavelengths than their predecessors. Moreover, these probes are compatible with HaloTag labeling, thus enabling timelapse, single-molecule imaging of specific protein targets for exceptionally long times. 相似文献
999.
Christoph Peschel Stefan van Wickeren Yves Preibisch Verena Naber Denis Werner Lars Frankenstein Dr. Fabian Horsthemke Prof. Dr. Urs Peuker Prof. Dr. Martin Winter Dr. Sascha Nowak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(22):e202200485
Herein we report on an analytical study of dry-shredded lithium-ion battery (LIB) materials with unknown composition. Samples from an industrial recycling process were analyzed concerning the elemental composition and (organic) compound speciation. Deep understanding of the base material for LIB recycling was obtained by identification and analysis of transition metal stoichiometry, current collector metals, base electrolyte and electrolyte additive residues, aging marker molecules and polymer binder fingerprints. For reversed engineering purposes, the main electrode and electrolyte chemistries were traced back to pristine materials. Furthermore, possible lifetime application and accompanied aging was evaluated based on target analysis on characteristic molecules described in literature. With this, the reported analytics provided precious information for value estimation of the undefined spent batteries and enabled tailored recycling process deliberations. The comprehensive feedstock characterization shown in this work paves the way for targeted process control in LIB recycling processes. 相似文献
1000.
Dr. Frederik Schleife Dr. Clément Bonnot Dr. Jean-Claude Chambron Dr. Martin Börner Prof. Dr. Berthold Kersting 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(21):e202104255
The syntheses and properties of expanded 4-tert-butyl-mercaptocalix[4]arenes, in which the methylene linkers are replaced by −CH2NRCH2− or −CH2NRCH2− and −CH2NRCH2CH2CH2NRCH2− units, are described. The new macrocycles were obtained in a step-wise manner, utilizing fully protected, i. e. S-alkylated, derivatives of the oxidation-sensitive thiophenols in the cyclisation steps. Reductive cleavage of the macrobicyclic or macrotricyclic intermediates ( 6 , 7 , 11 ) afforded the free thiophenols (H4 8 , H4 9 , and H4 12 ) in preparative yields as their hydrochloride salts. The protected proligands can exist in two conformations, resembling the “cone” and “1,3-alternate” conformations found for the parent calix[4]arenes. The free macrocycles do not show conformational isomerism, but are readily oxidized forming intramolecular disulfide linkages. Preliminary complexation experiments show that these expanded mercaptocalixarenes can serve as supporting ligands for tetranuclear thiolato clusters. 相似文献