全文获取类型
收费全文 | 10445篇 |
免费 | 558篇 |
国内免费 | 1047篇 |
专业分类
化学 | 9070篇 |
晶体学 | 134篇 |
力学 | 103篇 |
综合类 | 46篇 |
数学 | 1132篇 |
物理学 | 1565篇 |
出版年
2023年 | 71篇 |
2022年 | 135篇 |
2021年 | 179篇 |
2020年 | 171篇 |
2019年 | 527篇 |
2018年 | 260篇 |
2017年 | 493篇 |
2016年 | 289篇 |
2015年 | 301篇 |
2014年 | 335篇 |
2013年 | 642篇 |
2012年 | 562篇 |
2011年 | 649篇 |
2010年 | 460篇 |
2009年 | 671篇 |
2008年 | 738篇 |
2007年 | 656篇 |
2006年 | 612篇 |
2005年 | 532篇 |
2004年 | 552篇 |
2003年 | 472篇 |
2002年 | 434篇 |
2001年 | 314篇 |
2000年 | 269篇 |
1999年 | 211篇 |
1998年 | 195篇 |
1997年 | 183篇 |
1996年 | 171篇 |
1995年 | 169篇 |
1994年 | 136篇 |
1993年 | 114篇 |
1992年 | 121篇 |
1991年 | 68篇 |
1990年 | 57篇 |
1989年 | 36篇 |
1988年 | 43篇 |
1987年 | 34篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 28篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 21篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
This paper is concerned with the nonlinear Schrödinger equation with a harmonic potential which describes the attractive Bose–Einstein condensate under the magnetic trap. By combining the best constant of Gagliardo–Nirenberg's inequality with the characteristic of this equation, we derive out a global existence condition for the supercritical equation which coincides with the critical case. 相似文献
992.
气体绝缘开关设备(GIS)绝缘缺陷引发的放电会导致SF6分解,分解产生的低氟硫化物与设备内的微量H2O和O2反应生成具有腐蚀性的物质,影响设备正常运行,因此,研究SF6分解机理对GIS的安全运行具有重要意义。由于部分分解物在采样过程中发生转化,因此,实现SF6分解物的原位检测对于研究SF6分解机理是十分必要的。采用飞秒激光引导高压放电实现了高压放电空间和时间的精确控制,并利用飞秒激光引导高压放电产生的空间分辨光谱实现了SF6分解物的原位测量。首先研究证明了飞秒激光不会引起SF6的分解;其次,利用飞秒激光产生的等离子体通道实现了放电空间和时间的精确控制;最后,发现分解物中包含由于高能电子碰撞直接或间接产生的大量S和F的离子和原子。研究证明了基于飞秒激光引导高压放电可以实现SF6分解物的原位检测,为开展高压放电下SF6分解机理研究提供了一种新的研究手段。 相似文献
993.
Anna Luise Grab Dirk Hose Patrick Horn Elisabetta Ada Cavalcanti-Adam Anja Seckinger Martin Müller 《Particle & Particle Systems Characterization》2021,38(3):2000263
In the malignant plasma cell disease multiple myeloma (MM), bone lesions and resulting fractures caused by MM cell (MMC) accumulation represent a major cause of morbidity and mortality. Despite recent advantages in systemic treatment, residual MMCs remain, especially in bone lesions. Therefore an interfacial delivery system for local treatment of MM and induced bone disease based on polyelectrolyte complex nanoparticles (PEC NP) loaded with bone morphogenetic protein 6 (BMP-6) inducing de-novo bone formation and MMC apoptosis is presented herein. BMP-6 loaded PEC NP are fabricated by defined mixing bio-related cationic and anionic polysaccharides and BMP-6 according to molar ratio of BMP-6/PEC-NP of 1/3. BMP-6/PEC NP bound to a model substrate releases 10% BMP-6 sustainably within two weeks as accessed by infrared spectroscopy. BMP-6 loaded PEC NP adheres to cell membranes of MMCs and MSCs and activated phosphorylation of Smad 1/5. Osteogenic differentiation (ALP-concentration) is enhanced in MSCs (p < 0.05). All patient samples (10/10) of MMCs show significant induction of apoptosis (median 84%, p < 0.05). Finally, BMP-6/PEC NP are successfully integrated in a commercial hyaluronic acid based hydrogel material revealing MMC death as principal proof for the local treatment of MM induced bone lesions. 相似文献
994.
Syntheses,Structures, and Photophysical Properties of Two Coordination Polymers Based on 2,3‐Dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic Acid
下载免费PDF全文
![点击此处可从《无机化学与普通化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Two complexes based on the ligand 1,4‐dihydro‐2,3‐quinoxalinedione, namely [Mn(H2L)2(H2O)2]n ( 1 ) and {[Zn2(H2L)2(tz)2] · 5H2O}n ( 2 ) (H3L = 2,3‐dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic acid, Htz = 1,2,4‐triazole) were hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, as well as single‐crystal and powder X‐ray diffraction. Complex 1 exhibited a 1D comb‐like chain formed by H2L– anions linking MnII ions, whereas complex 2 was a 2D layer‐like structure with square‐shaped windows and outstretched arms built by combination of H2L– and tz– ligands with ZnII ions. The adjacent chains or layers connected with each other by intermolecular hydrogen bonding and π–π stacking to further extend to a 3D supermolecular framework. In addition, the thermal stabilities, luminescence properties, and optical energy gap of 1 and 2 were investigated in detail. 相似文献
995.
Crystal Structure,Magnetism, 89Y Solid State NMR,and 121Sb Mössbauer Spectroscopic Investigations of YIrSb
下载免费PDF全文
![点击此处可从《无机化学与普通化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Christopher Benndorf Lukas Heletta Theresa Block Hellmut Eckert Rainer Pöttgen 《无机化学与普通化学杂志》2017,643(4):294-298
The ternary antimonide YIrSb was synthesized from the binary precursor YIr and elemental antimony by a diffusion controlled solid‐state reaction. Single crystals were obtained by a flux technique with elemental bismuth as an inert solvent. The YIrSb structure (TiNiSi type, space group Pnma) was refined from single‐crystal X‐ray diffractometer data: a = 711.06(9), b = 447.74(5), c = 784.20(8) pm, wR2 = 0.0455, 535 F2 values, 20 variables. 89Y solid state MAS NMR and 121Sb Mössbauer spectra show single resonance lines in agreement with single‐crystal X‐ray data. YIrSb is a Pauli paramagnet. 相似文献
996.
Paulo A. Machicao Scott R. Burt Ryan K. Christensen Nathan B. Lohner J.D. Singleton Matt A. Peterson 《Tetrahedron letters》2017,58(24):2318-2321
Treatment of N-[(4-hydroxy-6-phenyl)pyrimidin-2-yl]cyanamide with 1° alkyl or arylamines in isopropyl alcohol for only 10 min at 110–120 °C under microwave conditions gave the corresponding N′-alkyl(aryl)guanidine derivatives in excellent yields (65–84%). Isolated yields were greatest when >1.0 equiv. of amines were employed, but excellent results were also obtained when aryl and alkylamines were reacted with a more atom-economical loading (1.0 equiv.; 70% and 72% ave. yields, respectively). Arylamines with either highly electron withdrawing substituents (e.g. CO2H) or pi-deficient heterocycles (e.g. variously substituted aminopyridines) did not work well under these conditions, and reaction with ureas and/or amino acids did not give detectable products. Work-up was exceedingly simple, and involved simple collection and washing of product on a sintered glass funnel. Products were obtained in analytically pure form and required approximately 1 h to prepare, start to finish. 相似文献
997.
Tsukiho Hayashi Ayumi Osawa Takehiro Watanabe Yoshiko Murata Atsushi Nakayama Kosuke Namba 《Tetrahedron letters》2017,58(20):1961-1964
1,3a,6a-Triazapentalene (TAP)-labeled enterobactin was developed as an iron ion sensor. 3-Acetylated-TAP was successfully introduced to the catechol ring of enterobactin, a well-recognized siderophore secreted by various Gram-negative bacteria. The fluorescence of TAP-labeled enterobactin decreased gradually as the amount of Fe3+ ion as an additive was increased, and 1.2 equiv of Fe3+ ion completely quenched the fluorescence. In clear contrast, when other metal ions were used, the fluorescence of TAP-labeled enterobactin remained even at 5.0 equiv. 相似文献
998.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(2):643-646
The homoleptic organocerium complex Ce{C(SiHMe2)3}3 ( 1 ) reacts with B(C6F5)3 to produce the zwitterionic bis(alkyl) hydridoborato Ce{C(SiHMe2)3}2HB(C6F5)3 ( 2 ). NMR and IR spectroscopy and X‐ray crystallography indicate that each alkyl ligand contains two bridging Ce↼H‐Si interactions in both 1 and 2 . Compound 2 serves as a precatalyst for the hydrosilylation of acrylates to give α‐silyl esters at room temperature with a turnover number of 2200. 相似文献
999.
1000.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(5):1234-1238
Hydrophobically capped nanocrystals of formamidinium lead bromide (FAPbBr3) perovskite (PNC) show bright and stable fluorescence in solution and thin‐film states. When compared with isolated PNCs in a solution, close‐packed PNCs in a thin film show extended fluorescence lifetime (ca. 4.2 μs), which is due to hopping or migration of photogenerated excitons among PNCs. Both fluorescence quantum efficiency and lifetime decrease in a PNC thin film doped with fullerene (C60), which is attributed to channeling of exciton migration into electron transfer to C60. On the other hand, quenching of fluorescence intensity of a PNC solution is not accompanied by any change in fluorescence lifetime, indicating static electron transfer to C60 adsorbed onto the hydrophobic surface of individual PNCs. Exciton migration among close‐packed PNCs and electron transfer to C60 places C60‐doped PNC thin films among cost‐effective antenna systems for solar cells. 相似文献