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1.
Carotenoids are an essential component of cashew and can be used in pharmaceuticals, cosmetics, natural pigment, food additives, among other applications. The present work focuses on optimizing and comparing conventional and ultrasound-assisted extraction methods. Every optimization step took place with a 1:1 (w:w) mixture of yellow and red cashew apples lyophilized and ground in a cryogenic mill. A Simplex-centroid design was applied for both methods, and the solvents acetone, methanol, ethanol, and petroleum ether were evaluated. After choosing the extractor solvent, a central composite design was applied to optimize the sample mass (59–201 mg) and extraction time (6–34 min). The optimum conditions for the extractor solvent were 38% acetone, 30% ethanol, and 32% petroleum ether for CE and a mixture of 44% acetone and 56% methanol for UAE. The best experimental conditions for UAE were a sonication time of 19 min and a sample mass of 153 mg, while the CE was 23 min and 136 mg. Comparing red and yellow cashews, red cashews showed a higher carotenoid content in both methodologies. The UAE methodology was ca. 21% faster, presented a more straightforward composition of extracting solution, showed an average yield of superior carotenoid content in all samples compared to CE. Therefore, UAE has demonstrated a simple, efficient, fast, low-cost adjustment methodology and a reliable alternative for other applications involving these bioactive compounds in the studied or similar matrix. 相似文献
2.
Photocatalytic CO2 reduction to C1 fuels is considered to be an important way for alleviating increasingly serious energy crisis and environmental pollution. Due to the environment-friendly, simple preparation, easy formation of highly-stable metal-nitrogen(M-Nx) coordination bonds, and suitable band structure, polymeric carbon nitride-based single-atom catalysts(C3N4-based SACs) are expected to become a potential for CO2 reduction under visible-light irradiation. In this review, we summarize the recent advancement on C3N4-based SACs for photocatalytic CO2 reduction to C1 products, including the reaction mechanism for photocatalytic CO2 reduction to C1 products, the structure and synthesis methods of C3N4-based SACs and their applications toward photocatalytic CO2 reduction reaction(CO2RR) for C1 production. The current challenges and future opportunities of C3N4-based SACs for photoreduction of CO2 are also discussed. 相似文献
3.
Shai Shechter 《Journal of Pure and Applied Algebra》2019,223(10):4384-4425
Let be a complete discrete valuation ring with finite residue field of odd characteristic, and let G be a symplectic or special orthogonal group scheme over . For any let denote the ?-th principal congruence subgroup of . An irreducible character of the group is said to be regular if it is trivial on a subgroup for some ?, and if its restriction to consists of characters of minimal -stabilizer dimension. In the present paper we consider the regular characters of such classical groups over , and construct and enumerate all regular characters of , when the characteristic of is greater than two. As a result, we compute the regular part of their representation zeta function. 相似文献
4.
Johannes Wittmann 《Mathematische Nachrichten》2019,292(7):1627-1635
Let M be a closed spin manifold and let N be a closed manifold. For maps and Riemannian metrics g on M and h on N, we consider the Dirac operator of the twisted Dirac bundle . To this Dirac operator one can associate an index in . If M is 2‐dimensional, one gets a lower bound for the dimension of the kernel of out of this index. We investigate the question whether this lower bound is obtained for generic tupels . 相似文献
5.
In 2001, J.-M. Le Bars disproved the zero-one law (that says that every sentence from a certain logic is either true asymptotically almost surely (a.a.s.), or false a.a.s.) for existential monadic second order sentences (EMSO) on undirected graphs. He proved that there exists an EMSO sentence ? such that does not converge as (here, the probability distribution is uniform over the set of all graphs on the labeled set of vertices ). In the same paper, he conjectured that, for EMSO sentences with 2 first order variables, the zero-one law holds. In this paper, we disprove this conjecture. 相似文献
6.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
7.
Durairaj Gopalakrishnan Santhanam Srinath Baburaj Baskar Nattamai S.P. Bhuvanesh Mani Ganeshpandian 《应用有机金属化学》2019,33(3)
Two organometallic Ru(II)‐p‐cymene complexes of the type [Ru(η6‐p‐cymene)(L)Cl]PF6 1 and 2 , where L is N,N‐bis(4‐isopropylbenzylidene)ethane‐1,2‐diamine (bien, L1 ) or N,N‐bis (pyren‐2‐ylmethylene)ethane‐1,2‐diamine (bpen, L2 ) have been prepared and characterized well. Because of appended pyrenyl groups in coordinated bpen ligand, the complex 2 exhibits higher DNA and protein binding than complex 1 in which isopropylbenzyl groups are incorporated. Interestingly, the luminescent characteristic complex 2 is unique in displaying DNA cleavage after light activation by UVA light at 365 nm through oxygen dependent mechanism. AFM analysis attests the photo‐induced DNA fragmentation ability of complex 2 . Also, the complex 2 cleaves the protein after light exposure in a non‐specific manner suggesting that it can act as a protein photo cleaving agent. In contrast to the trend of DNA and protein interaction of complexes, the complex 1 exhibits cytotoxic activity against human breast carcinoma ( MCF‐7 ) and liver carcinoma ( HepG2 ) with potency higher than that of complex 2 due to enhanced hydrophobicity of isopropyl groups present in p‐cymene and bien ligands. Indeed, complex 2 is inactive against MCF‐7 and HepG2 cancer cell lines even up to 200 μM concentration. The AO/EB staining assay reveals that the complex 1 is able to induce late apoptotic mode of cell death in breast cancer cells, which is further confirmed by inter‐nucleosomal DNA cleavage. Furthermore, the complexes 1 and 2 are evaluated for their catalytic activities and found to be working well for the β‐carboline directed C–H arylation to afford the desired products in good yield (40–47%). 相似文献
8.
Pierre Thureau Simone Sturniolo Miri Zilka Fabio Ziarelli Stéphane Viel Jonathan R. Yates Giulia Mollica 《Magnetic resonance in chemistry : MRC》2019,57(5):256-264
Structure determination of functional organic compounds remains a formidable challenge when the sample exists as a powder. Nuclear magnetic resonance crystallography approaches based on the comparison of experimental and Density Functional Theory (DFT)-computed 1H chemical shifts have already demonstrated great potential for structure determination of organic powders, but limitations still persist. In this study, we discuss the possibility of using 13C-13C dipolar couplings quantified on powdered theophylline at natural isotopic abundance with the help of dynamic nuclear polarization, to realize a DFT-free, rapid screening of a pool of structures predicted by ab initio random structure search. We show that although 13C-13C dipolar couplings can identify structures possessing long range structural motifs and unit cell parameters close to those of the true structure, it must be complemented with other data to recover information about the presence and the chemical nature of the supramolecular interactions. 相似文献
9.
缪正武 《浙江大学学报(理学版)》2019,46(6):680-685
提出利用拉格朗日乘子法重新证明σ 2 ![]()
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算子的最优凹性,并定义了一个凸锥Γ 3 ? = λ = ( λ 1 , λ 2 , ? , λ n ) ∈ R n : σ 1 ( λ ) > 0 , σ 2 ( λ | i ) > 0 , 1 ≤ i ≤ n ![]()
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。利用σ 2 ![]()
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算子的最优凹性,给出了σ 2 H e s s i a n 方 程 P o g o r e l o v ![]()
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型C 2 ![]()
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内估计,进而证明了σ 2 ( D 2 u ( x ) ) = 1 , x ∈ R n ![]()
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的满足二次多项式增长条件的Γ 3 ? - ![]()
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凸整解为二次多项式。 相似文献
10.
Monika Kořenková Dr. Ing. Martin Hejda Prof. Milan Erben Dr. Ing. Robert Jirásko Prof. Dr. Roman Jambor Prof. Aleš Růžička Dr. Elena Rychagova Prof. Sergey Ketkov Prof. Libor Dostál 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(56):12884-12888
The reaction of N,C,N-chelated stibinidene ArSb ( 1 ) (Ar=C6H3-2,6-(CH=NtBu)2) with selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing an antimony atom at the bridgehead position, fused with a 6-membered benzene and a 5-membered N-alkyl/aryl-pyrrolidine ring. These compounds were completely characterized. More importantly, additional studies showed that these reactions are reversible in solution, thereby representing an unprecedented reversible activation of a C=C bond by an antimony(I) compound. 相似文献