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971.
Yan Zhang Phani Morisetti Jeffery Kim Lynelle Smith Hai Lin 《Theoretical chemistry accounts》2008,121(5-6):313-319
Theoretical studies are presented into the experimentally observed regioselectivity difference of testosterone hydroxylation by cytochrome P450 3A4 at the 1β, 2β, 6β, and 15β positions. Such regioselectivity is investigated by density functional theory calculations on a model system. The barrier heights of hydrogen abstraction, which are corrected by zero-point vibrational energies, are computed to be about 10.1, 13.6, 14.4, and 16.2 kcal/mol for the 6β-, 2β-, 15β-, and 1β-positions, respectively. The calculated barriers suggest the regioselectivity preference of 6β ? 2β > 15β > 1β, which is in good agreement with experimental findings. 相似文献
972.
Kiran Kumarvarma Chakrahari Rhone P. Brocha Silalahi Tzu‐Hao Chiu Xiaoping Wang Nadia Azrou Samia Kahlal Yu‐Chiao Liu Ming‐Hsi Chiang Jean‐Yves Saillard C. W. Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):4997-5001
The structurally precise Cu‐rich hydride nanoclusters [PdCu14H2(dtc/dtp)6(C≡CPh)6] (dtc: di‐butyldithiocarbamate ( 1 ); dtp: di‐isopropyl dithiophosphate ( 2 )) were synthesized from the reaction of polyhydrido copper clusters [Cu28H15(S2CNnBu2)12]+ or [Cu20H11{S2P(OiPr)2}9] with phenyl acetylene in the presence of Pd(PPh3)2Cl2. Their structures and compositions were determined by single‐crystal X‐ray diffraction and the results supported by ESI‐mass spectrometry. Hydride positions in 1 were confirmed by single‐crystal neutron diffraction. Each hydride is connected to one Pd0 and four CuI atoms in slightly distorted trigonalbipyramidal geometry. The anatomies of clusters 1 and 2 are very similar and DFT calculations allow rationalizing the interactions between the encapsulated [PdH2]2? unit and its Cu14 bicapped icosahedral cage. As a result, Pd has the highest coordination number (14) so far recorded. 相似文献
973.
974.
氧化态Co/γ-Al_2O_3催化剂的结构与反应性能研Ⅰ.活性及体相、表相结构表征 总被引:1,自引:0,他引:1
采用等量浸渍法 ,制得 5 0 0、 6 0 0、 75 0和 95 0℃焙烧的 Co/ γ- Al2 O3催化剂 ;考察了它们对 CO氧化和乙烯选择还原 NO的反应性能 ;用 XRD和 XPS方法表征了催化剂的体相与表相结构 .活性测试结果表明 ,随焙烧温度升高 ,样品对 CO的氧化活性呈下降趋势 ;对乙烯选择还原 NO反应 ,活性先上升 ,而后又有所下降 (当焙烧温度高于 75 0℃时 ) .从硝酸钴制得的样品 ,其氧化活性要高于从醋酸钴制得的样品 ,但对乙烯选择还原 NO,后者的活性更好 .结构表征结果表明 ,催化剂中钴物种的存在形式与原料盐类及焙烧温度密切相关 .在 Co/ γ- Al2 O3催化剂中主要存在两种钴相 ,即 Co3O4和非化学计量的 Cox Al( 8/ 3- 2 x/ 3) O4尖晶石相 ,前者为完全氧化活性中心 ,后者是 NO选择还原的活性中心 .在相同焙烧温度下 ,以醋酸钴为原料时 ,更容易形成 Cox Al( 8/ 3- 2 x/ 3) O4尖晶石相 .随着焙烧温度提高 ,活性组分与载体的相互作用加强 ,Co3O4相逐步向 Cox Al( 8/ 3- 2 x / 3) O4尖晶石相转化 ,这可能是样品氧化活性下降和选择还原活性升高的主要原因 .在更高焙烧温度下 ,随着 Cox Al( 8/ 3- 2 x / 3) O4尖晶石相颗粒度的增加和晶形改变 ,以及钴离子由表相向体相的迁移 ,使样品比表面积下降 ,表面氧空位及活性位减少 , 相似文献
975.
976.
Yiyue Yang Ming Yang Tong Zhao Lingyi Pan Li Jia Lufei Zheng 《Molecules (Basel, Switzerland)》2022,27(17)
This study describes the variation in residue behavior of fluopyram in soil, carrot root, and carrot leaf samples after the application of fluopyram (41.7% suspension, Bayer) by foliar spray or root irrigation at the standard of 250.00 g active ingredient per hectare (a.i./ha) and double-dose treatment (500.00 g a.i./ha). Fluopyram and its metabolite fluopyram-benzamide were extracted and cleaned up using the QuEChERS method and subsequently quantified with LC-QQQ-MS/MS. The LOD and LOQ of the developed method were in the range of 0.05–2.65 ug/kg and 0.16–8.82 ug/kg, respectively. After root irrigation, the final residues detected in edible parts were 0.60 and 1.80 mg/kg, respectively, when 250.00 and 500.00 g a.i./ha were applied, which is much higher than the maximum residue limit in China (0.40 mg/kg). In contrast, after spray application, most of the fluopyram dissipated from the surface of carrot leaves, and the final residues in carrot roots were both only 0.05 mg/kg. Dietary risk assessments revealed a 23–40% risk quotient for the root irrigation method, which was higher than that for the foliar spray method (8–14%). This is the first report comparing the residue behavior of fluopyram applied by root irrigation and foliar spray. This study demonstrates the difference in risk associated with the two application methods and can serve as a reference for the safe application of fluopyram. 相似文献
977.
FU Qiang YANG Ming CHEN Bin WANC En-Bo XIE De-Min JIANG Zhong-Ming PENG Jun 《高等学校化学研究》1997,13(3):262-267
QuantumChemistryStudiesontheHeteropolyBluesofMolybdosilicSerieswithα-KegginStructureFUQiang,YANGMing,CHENBin,WANCEn-Bo,XIEDe-... 相似文献
978.
979.
Assisted Cloning and Orthogonal Complementing of an Arbitrary Unknown Two-Qubit Entangled State 总被引:1,自引:0,他引:1
Based on A.K. Pati‘s original idea [Phys. Rev. A 61 (2000) 022308] on single-qubit-state-assisted clone, very recently Zhan has proposed two assisted quantum cloning protocols of a special class of unknown two-qubit entangled states [Phys. Lett. A 336 (2005) 317]. In this paper we further generalize Zhan‘s protocols such that an arbitrary unknown two-qubit entangled state can be treated. 相似文献
980.