全文获取类型
收费全文 | 39359篇 |
免费 | 15761篇 |
国内免费 | 51篇 |
专业分类
化学 | 52490篇 |
晶体学 | 18篇 |
力学 | 1081篇 |
数学 | 1112篇 |
物理学 | 470篇 |
出版年
2024年 | 423篇 |
2023年 | 4240篇 |
2022年 | 1397篇 |
2021年 | 2399篇 |
2020年 | 4672篇 |
2019年 | 2214篇 |
2018年 | 2363篇 |
2017年 | 602篇 |
2016年 | 5533篇 |
2015年 | 5491篇 |
2014年 | 4906篇 |
2013年 | 5016篇 |
2012年 | 3012篇 |
2011年 | 943篇 |
2010年 | 3292篇 |
2009年 | 3234篇 |
2008年 | 970篇 |
2007年 | 660篇 |
2006年 | 101篇 |
2005年 | 49篇 |
2004年 | 41篇 |
1997年 | 46篇 |
1996年 | 47篇 |
1995年 | 111篇 |
1994年 | 70篇 |
1993年 | 185篇 |
1992年 | 66篇 |
1991年 | 58篇 |
1989年 | 46篇 |
1988年 | 79篇 |
1987年 | 64篇 |
1986年 | 46篇 |
1985年 | 46篇 |
1984年 | 59篇 |
1983年 | 65篇 |
1982年 | 74篇 |
1981年 | 85篇 |
1980年 | 105篇 |
1979年 | 97篇 |
1978年 | 99篇 |
1977年 | 166篇 |
1976年 | 184篇 |
1975年 | 185篇 |
1974年 | 194篇 |
1973年 | 114篇 |
1972年 | 153篇 |
1971年 | 122篇 |
1970年 | 208篇 |
1969年 | 125篇 |
1968年 | 133篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Carl Philipp Rosenau Dr. Benson J. Jelier Dr. Alvar D. Gossert Prof. Dr. Antonio Togni 《Angewandte Chemie (International ed. in English)》2018,57(30):9528-9533
Fluorine chemistry has taken a pivotal role in chemical reaction discovery, drug development, and chemical biology. NMR spectroscopy, arguably the most important technique for the characterization of fluorinated compounds, is rife with highly inconsistent referencing of fluorine NMR chemical shifts, producing deviations larger than 1 ppm. Herein, we provide unprecedented evidence that both spectrometer design and the current unified scale system underpinning the calibration of heteronuclear NMR spectra have unintentionally led to widespread variation in the standardization of 19F NMR spectral data. We demonstrate that internal referencing provides the most robust, practical, and reproducible method whereby chemical shifts can be consistently measured and confirmed between institutions to less than 30 ppb deviation. Finally, we provide a comprehensive table of appropriately calibrated chemical shifts of reference compounds that will serve to calibrate 19F spectra correctly. 相似文献
952.
Photocontrolled Multidirectional Differentiation of Mesenchymal Stem Cells on an Upconversion Substrate 下载免费PDF全文
Zhengqing Yan Hongshuang Qin Prof. Jinsong Ren Prof. Xiaogang Qu 《Angewandte Chemie (International ed. in English)》2018,57(35):11182-11187
The effective guidance of mesenchymal stem cell (MSC) differentiation on a substrate by near‐infrared (NIR) light is particularly attractive for tissue engineering and regenerative medicine. However, most of current substrates cannot control multidirectional differentiation of MSCs like natural tissues. Herein, a photocontrolled upconversion‐based substrate was designed and constructed for guiding multidirectional differentiation of MSCs. The substrate enables MSCs to maintain their stem‐cell characteristics due to the anti‐adhesive effect of 4‐(hydroxymethyl)‐3‐nitrobenzoic acid modified poly(ethylene glycol) (P1) attached on the upconversion substrate. Upon NIR irradiation, the P1 is released from the substrate by photocleavage. The detachment of P1 can change cell–matrix interactions dynamically. Moreover, MSCs cultured on the upconversion substrate can be specifically induced to differentiate to adipocytes or osteoblasts by adjusting the NIR laser. Our work provides a new way of using NIR‐based upconversion substrate to modulate the multidirectional differentiation of MSCs. 相似文献
953.
Niels Weidmann Marthe Ketels Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2018,57(33):10748-10751
The first sodiations of (hetero)arenes in continuous flow using NaDA (sodium diisopropylamide) in Me2EtN are reported. This flow procedure enables sodiation of functionalized arenes and heteroarenes that decompose under batch‐sodiation conditions. The resulting sodiated (hetero)arenes react instantly with various electrophiles, such as ketones, aldehydes, isocyanates, alkyl bromides, and disulfides, affording polyfunctionalized (hetero)arenes in high yields. Scale‐up is possible without further optimization. 相似文献
954.
Monochalcoplatin: An Actively Transported,Quickly Reducible,and Highly Potent PtIV Anticancer Prodrug 下载免费PDF全文
Dr. Lili Ma Na Wang Rong Ma Cai Li Zoufeng Xu Dr. Man‐Kit Tse Prof. Dr. Guangyu Zhu 《Angewandte Chemie (International ed. in English)》2018,57(29):9098-9102
Recently, PtIV prodrugs have attracted much attention as the next generation of platinum‐based antineoplastic drug candidates. Here we report the discovery and evaluation of monochalcoplatin, a monocarboxylated PtIV prodrug that is among the most cytotoxic PtIV prodrugs to date. Compared with its dicarboxylated counterpart chalcoplatin, monochalcoplatin accumulates astonishingly effectively and rapidly in cancer cells, which is not ascribed to its lipophilicity. The prodrug is quickly reduced, causes DNA damage, and induces apoptosis, resulting in superior cytotoxicity with IC50 values in the nanomolar range in both cisplatin‐sensitive and ‐resistant cells; these IC50 values are up to 422‐fold higher than that of cisplatin. A detailed mechanistic study reveals that monochalcoplatin actively enters cells through a transporter‐mediated process. Moreover, monochalcoplatin shows significant antitumor activity in an in vivo colorectal tumor model. Our study implies a practical strategy for the design of more effective PtIV prodrugs to conquer drug resistance by tuning both cellular uptake pathways and activation processes. 相似文献
955.
Steric Effect of Carboxylate Ligands on Pd‐Catalyzed Intramolecular C(sp2)–H and C(sp3)–H Arylation Reactions 下载免费PDF全文
Yutaka Tanji Naoya Mitsutake Prof. Dr. Tetsuaki Fujihara Prof. Dr. Yasushi Tsuji 《Angewandte Chemie (International ed. in English)》2018,57(32):10314-10317
A bulky carboxylic acid bearing three cyclohexylmethyl substituents at the α‐position, namely, tri(cyclohexylmethyl)acetic acid, is demonstrated to act as an efficient ligand source in Pd‐catalyzed intramolecular C(sp2)?H and C(sp3)?H arylation reactions. The reactions proceed smoothly under mild reaction conditions, even at room temperature due to the steric bulk of the carboxylate ligands, which accelerates the rate‐determining C?H bond activation step in the catalytic cycle. 相似文献
956.
A Microporous Covalent–Organic Framework with Abundant Accessible Carbonyl Groups for Lithium‐Ion Batteries 下载免费PDF全文
Zhiqiang Luo Luojia Liu Jiaxin Ning Kaixiang Lei Yong Lu Prof. Fujun Li Prof. Jun Chen 《Angewandte Chemie (International ed. in English)》2018,57(30):9443-9446
A key challenge faced by organic electrodes is how to promote the redox reactions of functional groups to achieve high specific capacity and rate performance. Here, we report a two‐dimensional (2D) microporous covalent–organic framework (COF), poly(imide‐benzoquinone), via in situ polymerization on graphene (PIBN‐G) to function as a cathode material for lithium‐ion batteries (LIBs). Such a structure favors charge transfer from graphene to PIBN and full access of both electrons and Li+ ions to the abundant redox‐active carbonyl groups, which are essential for battery reactions. This enables large reversible specific capacities of 271.0 and 193.1 mAh g?1 at 0.1 and 10 C, respectively, and retention of more than 86 % after 300 cycles. The discharging/charging process successively involves 8 Li+ and 2 Li+ in the carbonyl groups of the respective imide and quinone groups. The structural merits of PIBN‐G will trigger more investigations into the designable and versatile COFs for electrochemistry. 相似文献
957.
Experimental Evidence for a Triboluminescent Antiperovskite Ferroelectric: Tris(trimethylammonium) catena‐Tri‐μ‐chloro‐manganate(II) Tetrachloromanganate(II) 下载免费PDF全文
Dr. Peng‐Fei Li Dr. Yuan‐Yuan Tang Dr. Wei‐Qiang Liao Dr. Ping‐Ping Shi Dr. Xiu‐Ni Hua Dr. Yi Zhang Dr. Zhenhong Wei Dr. Hu Cai Prof. Ren‐Gen Xiong 《Angewandte Chemie (International ed. in English)》2018,57(37):11939-11942
The perovskite structure is rich in ferroelectricity. In contrast, ferroelectric antiperovskites have been scarcely confirmed experimentally since the discovery of M3AB‐type antiperovskites in the 1930s. Ferroelectricity is now revealed in an organic–inorganic hybrid X3AB antiperovskite structure, which exhibits a clear ferroelectric phase transition 6/mmmF6mm with a high Curie point of 480 K. The physical properties across the phase transition are obviously changed along with the symmetry requirements, providing solid experimental evidence for the ferroelectric phase transition. More interestingly, the discovered antiperovskite shows intense photoluminescence and triboluminescence properties. The confirmation of the triboluminescent ferroelectric antiperovskite will open new avenues to explore excellent optoelectronic properties in the antiperovskite family. 相似文献
958.
The β‐Agostic Structure in (C5Me5)2Sc(CH2CH3): Solid‐State NMR Studies of (C5Me5)2Sc−R (R=Me,Ph, Et) 下载免费PDF全文
Damien B. Culver Winn Huynh Dr. Hosein Tafazolian Dr. Ta‐Chung Ong Prof. Dr. Matthew P. Conley 《Angewandte Chemie (International ed. in English)》2018,57(30):9520-9523
Multinuclear solid‐state NMR studies of Cp*2Sc?R (Cp*=pentamethylcyclopentadienyl; R=Me, Ph, Et) and DFT calculations show that the Sc?Et complex contains a β‐CH agostic interaction. The static central transition 45Sc NMR spectra show that the quadrupolar coupling constants (Cq) follow the trend of Ph≈Me>Et, indicating that the Sc?R bond is different in Cp*2Sc?Et compared to the methyl and phenyl complexes. Analysis of the chemical shift tensor (CST) shows that the deshielding experienced by Cβ in Sc?CH2CH3 is related to coupling between the filled σC‐C orbital and the vacant orbital. 相似文献
959.
Yong Li Yingzheng Shu Muwen Liang Dr. Xilei Xie Dr. Xiaoyun Jiao Prof. Xu Wang Prof. Bo Tang 《Angewandte Chemie (International ed. in English)》2018,57(38):12415-12419
Carbon monoxide (CO) is proposed as an active pharmaceutical agent with promising pharmaceutical prospects, as it has been involved in multifaceted modulation of diverse physiological and pathological processes. However, questions remain for therapeutic application of inhaled CO attributed to the inherent great affinity between CO and hemoglobin. Therefore, a robust platform with the function of CO transport and controllable release, depending on the local status of an organism, is of prominent significance for effectively avoiding the side effects of CO inhalation and optimizing the biological regulation function of CO. Utilizing the oxidative stress biomarker H2O2 as a trigger and combining with photo‐control, a two‐photon H2O2‐activated CO photoreleaser, FB, featuring highly sensitive and specific H2O2 sensing and photocontrollable CO release, was developed and the vasodilation effect of CO against angiotensin II was demonstrated. 相似文献
960.
Stress‐Transfer‐Induced In Situ Formation of Ultrathin Nickel Phosphide Nanosheets for Efficient Hydrogen Evolution 下载免费PDF全文
Shao‐Hai Li Dr. Nan Zhang Dr. Xiuqiang Xie Prof. Dr. Rafael Luque Prof. Dr. Yi‐Jun Xu 《Angewandte Chemie (International ed. in English)》2018,57(40):13082-13085
Ultrathin two‐dimensional (2D) nanostructures have attracted increasing research interest for energy storage and conversion. However, tackling the key problem of lattice mismatch inducing the instability of ulreathin nanostructures during phase transformations is still a critical challenge. Herein, we describe a facile and scalable strategy for the growth of ultrathin nickel phosphide (Ni2P) nanosheets (NSs) with exposed (001) facets. We show that single‐layer functionalized graphene with residual oxygen‐containing groups and a large lateral size contributes to reducing the lattice strain during phosphorization. The resulting nanostructure exhibits remarkable hydrogen evolution activity and good stability under alkaline conditions. 相似文献