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941.
The reaction of 1‐(trimethylsilyloxy)cyclopentene ( 9 ) with (±)‐1,3,5‐triisopropyl‐2‐(1‐(RS)‐{[(1E)‐2‐methylpenta‐1,3‐dienyl]oxy}ethyl)benzene ((±)‐ 4a ) in SO2/CH2Cl2 containing (CF3SO2)2NH, followed by treatment with Bu4NF and MeI gave a 3.0 : 1 mixture of (±)‐(2RS)‐2{(1RS,2Z,4SR)‐2‐methyl‐4‐(methylsulfonyl)‐1‐[(RS)‐1‐(2,4,6‐triisopropylphenyl)ethoxy]pent‐2‐en‐1‐yl}cyclopentanone ((±)‐ 10 ) and (±)‐(2RS)‐2‐{(1RS,2Z)‐2‐methyl‐4‐[(SR)‐methylsulfonyl]‐1‐[(SR)‐1‐(2,4,6‐triisopropylphenyl)ethoxy]pent‐2‐en‐1‐yl}cyclopentanone ((±)‐ 11 ). Similarly, enantiomerically pure dienyl ether (−)‐(1S)‐ 4a reacted with 1‐(trimethylsilyloxy)cyclohexene ( 12 ) to give a 14.1 : 1 mixture of (−)‐(2S)‐2‐{(1S,2Z,4R)‐2‐methyl‐4‐(methylsulfonyl)‐1‐[(S)‐1‐(2,4,6‐triisopropylphenyl)ethoxy]pent‐2‐enyl}cyclohexanone ((−)‐ 13a ) and its diastereoisomer 14a with (1S,2R,4R) or (1R,2S,4S) configuration. Structures of (±)‐ 10 , (±)‐ 11 , and (−)‐ 13a were established by single‐crystal X‐ray crystallography. Poor diastereoselectivities were observed with the (E,E)‐2‐methylpenta‐1,3‐diene‐1‐ylethers (+)‐ 4b and (−)‐ 4c bearing ( 1 S )‐1‐phenylethyl and (1S)‐1‐(pentafluorophenyl)ethyl groups instead of the Greene's auxiliary ((1S)‐(2,4,6‐triisopropylphenyl)ethyl group). The results demonstrate that high α/β‐syn and asymmetric induction (due to the chiral auxiliary) can be obtained in the four‐component syntheses of the β‐alkoxy ketones. The method generates enantiomerically pure polyfunctional methyl sulfones bearing three chiral centers on C‐atoms and one (Z)‐alkene moiety. 相似文献
942.
943.
Thomas Kolber Kurt Piplits Leopold Palmetshofer Herbert Hutter 《Mikrochimica acta》2000,135(1-2):105-111
The distribution of the relevant elements within TiN coatings, made with two different physical deposition methods as the
conventional dc vacuum arc method and the filtered high current pulsed arc method (Φ-HCA) are characterized and finally compared.
Despite the rougher surface of the dc-arc produced TiN layer, which is due to accumulated droplets, there is no evidence of
different stoechiometric composition of Ti and N on the surface. The interface of the dc-arc produced TiN layer (600 nm) is
10 times wider than the one made with the new filtered high current pulsed arc method (60 nm). However the TiN layer made
by Φ-HCA shows an inhomogeneous distribution of aluminum and chlorine in the vertical direction, whereas the dc-arc sample
is homogeneous. Furthermore, the TiN layer made by Φ-HCA shows vertically an obvious local maximum of chlorine at a depth
of about 130 nm. This vertical local maximum has an homogeneous distribution in horizontal direction, which means that a thin,
chlorine enriched layer has been incorporated inside the TiN layer. Nevertheless, quantification by SIMS shows that aluminum
as well as chlorine concentrations of both samples are too low to influence any TiN properties.
Received January 3, 2000. Revision April 4, 2000. 相似文献
944.
Naka Seidel Klaus Jacob Axel K. Fischer Kurt Merzweiler Christoph Wagner Marco Fontani Piero Zanello 《Journal of organometallic chemistry》2001,630(2):149-156
The diorganomercurial bis[2-(N,N-dimethylaminomethyl)ferrocenyl]mercury(II), (FcN)2Hg (3), can be obtained by the symmetrisation of the heteroleptic (FcN)HgCl (2) with Na2S2O3 or in the transmetallation reaction of 2 with (FcN)Li. By crystallisation only the crystals of rac-(FcN)2Hg were obtained. X-ray diffraction analysis revealed linear coordinated mercury atom with two η1-bonded FcN ligands. Additionally, weak chelate interactions exist between mercury and nitrogen atoms of the ---CH2NMe2 side chains. According to the 1H-NMR findings, these interactions are not preserved in solution. Diorganomercurial 3 appears in solution as a mixture of two diastereomers with rac/meso-(FcN)2Hg ratio of 1:1. This diastereomeric ratio in solution remains constant within a wide temperature range and in different solvents. The NMR spectroscopic data of the heteroleptic organomercurials [(FcN)HgCl]2·H2O (1) and (FcN)HgCl (2) indicate the chelate-free structure of this compounds in solution within the studied temperature interval (−80 to 90 °C). 相似文献
945.
Astrid Netz Kurt Polborn Thomas J. J. Müller 《Journal of organometallic chemistry》2001,640(1-2):41-49
The (phenyl)Cr(CO)3-complex substituted propargyl cation 4 significantly deviates in the chemoselectivity of the nucleophilic attack of thiols from the previously reported planar chiral ortho-substituted arene complexes and furnishes allenyl thioethers 5. This peculiar behavior can be rationalized assuming a subsequent base catalyzed propargyl–allenyl isomerization in acidic medium (!). An X-ray structure analysis of allenyl thioether 5c recrystallized from acetonitrile over weeks reveals that the [2+2] cyclodimer 10 has been formed. Thiolate adds to 5c to give a single diastereomer of the allyl compound 15 in good yield. 相似文献
946.
An analytical method has been developed for the determination of selenious acid, selenic acid, trimethylselenonium ion, and selenomethionine. The four selenium compounds were separated by HPLC on a column (25 cm×4 mm I.D.) of the anion-exchanger ESA Anion III with a mobile phase (1.5 ml/min) of 0.0055 M ammonium citrate (pH 5.5). Detection was carried out using an on-line inductively coupled plasma mass spectrometer (ICP-MS) or a flame atomic absorption spectrometer (FAAS) as the selenium-specific detector. The chromatographic parameters and the chemical factors affecting the separation of the selenium species were optimized. The four selenium compounds could be separated within 8 minutes. The detection limits of the coupled HPLC–FAAS system were approximately 1 mg Se/l for each compound (100 μl injection), estimated as three times the base-line noise of the chromatograms. More powerful selenium detection was achieved with an ICP-MS. Selenium was measured at m/z 78. To increase the nebulization efficiency, the Meinhard concentric glass nebulizer was replaced by an ultrasonic nebulizer. The ICP-MS signal intensity was increased with the ultrasonic nebulization by a factor of 7 times for selenious acid and 24 to 31 times for trimethylselenonium ion, selenomethionine, and selenic acid compared to that with the Meinhard nebulization. The detection limits achieved by the HPLC–ICP-MS with the ultrasonic nebulization were 0.08 μg Se/l for trimethylselenonium ion, 0.34 μg Se/l for selenious acid, 0.18 μg Se/l for selenomethionine, and 0.07 μg Se/l for selenic acid, respectively. 相似文献
947.
Bis(N‐acetyltriethylphosphaneiminium)‐tetraacetato‐dichloro‐dicuprate(II), [MeC(O)N(H)PEt3]2[Cu2(O2C–Me)4Cl2] The title compound has been prepared by the reaction of Me3SiNPEt3 with [Cu2(O2C–Me)4] and MeC(O)Cl in dichloromethane solution to give colourless crystals which include four molecules CH2Cl2 per formula unit. The complex is characterized by IR spectroscopy and by a crystal structure determination. [MeC(O)N(H)PEt3]2[Cu2(O2C–Me)4Cl2] · 4 CH2Cl2: Space group P21/n, Z = 2, lattice dimensions at –70 °C: a = 794.1(1), b = 2356.9(6), c = 1327.3(2) pm; β = 91.00(1)°; R1 = 0.0597. The structure consists of N‐acetyltriethylphosphaneiminium cations and dianions [Cu2(O2C–Me)4Cl2]2– which form an iontriple with N–H…Cl hydrogen bridges. 相似文献
948.
Crystal Structure of K[F5W(≡NCl)] Orange single crystals of K[F5W(≡NCl)] have been formed as a by‐product from the reaction of tungsten nitrido chloride, WNCl3, with Me3SnF in the presence of potassium fluoride in toluene suspension. K[F5W(≡NCl)] crystallizes in the monoclinic space group P21/c with four formula units per unit cell. Lattice dimensions at –83 °C: a = 1145.9(3), b = 770.4(2), c = 772.5(2) pm, β = 99.91(1)°, R1 = 0.0742. The compound forms an ionic structure with octahedral [F5W(≡NCl)]– ions with a nearly linear arrangement of the N‐chloroimido ligand group W≡N–Cl (bond angle 173°, WN distance 174 pm). The K+ ions link the anions via K…F contacts and coordination number eight to form double layers along [100]. The layers itself are associated by short bounding Cl…F contacts of 279 pm. 相似文献
949.
950.
Kurt Leschonski Bernd Benker Harald Powitz 《Particle & Particle Systems Characterization》2000,17(3):105-112
In assessing the quality of two instruments for particle size analysis, a diffraction pattern analyser and an X‐ray sedimentation centrifuge have been used in multiple analysis of two size distributions of spherical and irregularly shaped particles. As expected the distributions differ due to shape influence caused by different particle characteristics and due to different evaluation algorithms in the case of spheres. The reproducibility of the diffraction data is approximately five to ten times higher than the corresponding centrifugal data. Different mixtures of the basic materials have been analysed and the size distributions thus obtained have been compared with the distributions calculated from the basic data. The experiments showed that the X‐ray centrifuge determines the size distributions, the size dependent mixing ratio and the overall mixing ratio with a comparatively small error. The measurement showed that the mass balances applied represent a sensitive test on instrument performance. 相似文献