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131.
132.
Y2O3和CeO2复合掺杂ZrO2纳米晶的制备与表征 总被引:2,自引:0,他引:2
以ZrOCl2.8H2O,Y2O3,Ce(NO3)3.5.5H2O为原料,NH3.H2O作沉淀剂,少量表面活性剂PE作分散剂,采用反向共沉淀-喷雾干燥法,结合物理、化学分散技术,成功地制备了Y2O3,CeO2复合掺杂ZrO2纳米粉末。通过DSC-TG,XRD,XPS,BET和SEM等方法对所制得粉末进行了表征。结果表明:以Ce0.1Y0.1Zr0.8O1.95化学计量比制备的多元氢氧化物胶体经过喷雾干燥处理后,在500℃基本完成水合氧化物的分解,577℃附近完成由非晶相向立方相的转变;经过580-1000℃煅烧后,CeO2和Y2O3已经完全固溶到ZrO2中,形成类质同相体,该粉末系列均属于立方相萤石结构;掺杂进入ZrO2晶格中的Ce呈+4价形式存在;比表面积由22.0 m^2.g^-1(580℃煅烧)减至4.97 m^2.g^-1(1000℃煅烧);SEM结果显示800℃煅烧的该粉末颗粒尺寸分布均匀,多呈类球状,且粒径在50-80 nm。 相似文献
133.
Jiang‐Tao Chen Hai‐Zhou Li Dong Wang Ying‐Jun Zhang Chong‐Ren Yang 《Helvetica chimica acta》2006,89(7):1442-1448
Three new dammarane monodesmosides, named notoginsenosides Ft1 ( 1 ), Ft2 ( 2 ), and Ft3 ( 3 ), together with three known ginsenosides, were obtained from a mild acidic hydrolysis of the saponins from notoginseng (Panax notoginseng (Burk .) F. H. Chen ) leaves. Their structures were elucidated to be (3β,12β,20R)‐12,20‐dihydroxydammar‐24‐en‐3‐yl O‐β‐D ‐xylopyranosyl‐(1 → 2)‐O‐β‐D ‐glucopyranosyl‐(1 → 2)‐β‐D ‐glucopyranoside ( 1 ), (3β,12β)‐12,20,25‐trihydroxydammaran‐3‐yl O‐β‐D ‐xylopyranosyl‐(1 → 2)‐O‐β‐D ‐glucopyranosyl‐(1 → 2)‐β‐D ‐glucopyranoside ( 2 ), and (3β,12β,24ξ)‐12,20,24‐trihydroxydammar‐25‐en‐3‐yl O‐β‐D ‐xylopyranosyl‐(1 → 2)‐O‐β‐D ‐glucopyranosyl‐(1 → 2)‐β‐D ‐glucopyranoside ( 3 ), by means of spectroscopic evidences. The known ginsenosides Rh2 and Rg3 4 – 6 were obtained as the major products from this acidic deglycosylation. 相似文献
134.
135.
Min-zhi Chen Xiao-liang Wang Fang-fang Tao Qi Xue Ping-chuan 《高分子科学》2007,(1):107-111
The concept of entanglement provides the basis of our current understanding of the flow behavior of polymer melts, Current techniques developed to investigate the degree of interpenetration of polymer chains only provide indirectly the information of the degree of entanglement in a relatively large scale (several to tens of nanometer). In this article, we report ^1H-NMR spectroscopy with dipolar filters under fast magic angle spinning for probing chain interpenetration of polymer glasses at the molecular level. 相似文献
136.
The sorption and desorption isotherms of untreated calcareous soil and three treated soils to remove CaCO3, organic matter (OM) and both CaCO3 and OM were determined and analyzed with the Freundlich equation at pH 7.8, moderate concentrations of NpO2
+ (~10-5mol/l), in the presence of 0.01 mol/l CaCl2 and under ambient aerobic conditions. The relative contribution of CaCO3 and OM to the neptunium(V) sorption on calcareous soil and the sorption/desorption hysteresis is discussed. The effects of adding fulvic acid (FA) and carbonate in to the solution on the sorption of neptunium(V) on the soils were also studied. The sorption and desorption characteristics of NpO2
+, Zn2+, Sr2+ and Cs+ on the soils are compared. 相似文献
137.
以硅胶球为基质键合γ-GOPS并各接枝上具有络合功能的三种配体,邻位氨基吡啶、间酰氨基吡啶及对酰氨基吡啶,再和TiCl_4络合成固载化的Lewis酸催化剂,将这些催化剂进行缩醛、缩酮及酯化反应,有很好的催化活性,重复使用多次不失效.本文在合成此类催化剂的过程中利用热失重(TG)法及等离子光谱法(ICP)等检测方法对合成此类催化剂的每一步进行跟踪检测,得到键合反应,开环反应及络合反应过程中的键合量,开环相量和TiCl_4络合量的定量数据.对固载化催化剂表面的接枝量有所了解,从而可进一步检测此类催化剂的催化效应并得到一些启示. 相似文献
138.
Tao He Ying‐Fang Zou Cai‐Yuan Pan 《Journal of polymer science. Part A, Polymer chemistry》2002,40(20):3367-3378
Comb‐shaped graft copolymers with poly(methyl methacrylate) as a handle were synthesized by the macromonomer technique in two steps. First, polytetrahydrofuran acrylate (A‐PTHF), prepared by the living cationic ring‐opening polymerization of tetrahydrofuran, underwent homopolymerization with 1‐(ethoxycarbonyl)prop‐1‐yl dithiobenzoate as an initiator under 60Co γ irradiation at room temperature; Second, the handle of the comb‐shaped copolymers was prepared by the block copolymerization of methyl methacrylate with P(A‐PTHF) as a macroinitiator under 60Co γ irradiation. The two‐step polymerizations were proved to be controlled with the following evidence: the straight line of ln[M]0/[M] versus the polymerization time, the linear increase in the number‐average molecular weight with the conversion, and the relatively narrow molecular weight distribution. The structures of the P(A‐PTHF) and final comb‐shaped copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3367–3378, 2002 相似文献
139.
[reaction: see text] Reactions of the bifunctional allylstannane 2-(chloromethyl)-3-(tributylstannyl)propene with aldehydes have been examined. These generally occur in high yields using Lewis acid promoters and the products can be isolated and purified without incident. Good yields and high enantioselectivities are also realized in catalytic asymmetric allylations (CAA reactions) using the previously described BITIP catalyst system. Protection of the free hydroxyl can be accomplished without cyclization to the derived tetrahydrofuran, although this transformation is also facile. The utility of the incorporated allyl chloride functionality allows for the obvious use of such products in reactions with nucleophiles. Use of these products in a less obvious connective strategy is demonstrated in the synthesis of the C12-C27 segment of bryostatin 1 where a connective, or "lynchpin", double-allylation process was employed. The beta-hydroxy allyl chloride obtained from an initial chelation-controlled allylation of aldehyde 16 was converted to allylstannane 19 and applied in a second allylation reaction, thus allowing for a highly convergent synthesis of the bryostatin C ring backbone in a stereoselective fashion. 相似文献
140.