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排序方式: 共有1197条查询结果,搜索用时 31 毫秒
991.
We studied the dielectric relaxation behavior of low mass compounds (LMC) mixed in polystyrene (PS). Specifically, LMCs that are used are alkyl‐cyanobenzene (nCBz, n = 0), alkyl‐cyanobiphenyl (nCB, n = 0, 1, 3, 5, and 7), and alkyl‐cyanoterphenyl (nCT, n = 5), where n represents the number of carbon atoms of the normal alkyl groups of the LMCs. Owing to a much larger dipole moment of the cyano group than that of PS, only motions of the LMCs were observed. In a blend of 5CT (5 wt %)/PS, single relaxation process designated as α was observed. On the other hand, in nCB (5 wt %)/PS, partially overlapped two relaxation processes (α and β) were observed in the order of decreasing temperature. We assigned the α process to cooperative motions between the LMC molecules and the PS segments, and the β process to spatially restricted motions of the LMC molecules in the glassy state. In 0CBz (8 wt %)/PS, the α and β processes were observed in distinct temperature regions and the intensity of the α peak was comparable to that of pure PS, indicating that the 0CBz molecules do not move cooperatively with the PS segments. We conclude the existence of two critical sizes (I and II) of LMC in relation to cooperativity: when an LMC molecule is smaller than the size‐I, the motions of the LMCs and PS segments decouple each other, but above the size‐I, they become cooperative. Above the size‐II, the spatially restricted motion (β‐process) of LMC does not occur. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 967–974, 2006 相似文献
992.
M. Okinaka Y. Hamana T. Tokuda J. Ohta M. Nunoshita 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):473
Effect of lower growth temperature Ts on C incorporation to substitutional sites in Ge1−xCx/Si(0 0 1) grown by molecular beam epitaxy was investigated. To enhance the non-equilibrium growth condition, the temperature Ts was lowered from 600°C down to 300°C. The C incorporation into substitutional sites of GeC epilayers was very sensitive to Ts. X-ray diffraction (XRD) measurement indicated that the substitutional C composition x increased with decrease in Ts from 600°C to 400°C. At Ts350°C, the estimation of x by the XRD analysis was impossible because of polycrystallization. The Raman shift measurement enables to estimate x for Ts350°C, as consequently larger x than that grown at Ts=400°C was verified. The enhancement of non-equilibrium growth condition by decreasing Ts was important to increase x. 相似文献
993.
Teruaki Sakurai Masayuki Ochiai Chikara Kojima Takami Ohta Kitao Fujiwara 《应用有机金属化学》2005,19(2):226-230
In this study, we observed the first in vivo acute immunotoxicity of a trimethyl(2‐hydroxyethyl)arsonium cation, namely arsenocholine (AsCho), which is present in marine animals that are ingested daily as seafood in many countries. It has been reported that AsCho has significant acute in vivo toxicity. A high dose of the synthetic pure AsCho was administered to CDF1 mice intraperitoneally (0.1 g kg?1 mouse weight) or orally (a total of 10.0 g kg?1 mouse weight); its effect on the immune organs and immune effector cells was assessed. Administered AsCho, especially via the oral route, showed weak and partial, but significant, in vivo immunotoxicity in mice, although it did not cause any severe acute inflammatory responses. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
994.
Md. Nurul Amin Satoshi Kaneco Ken Nomura Tohru Suzuki Kiyohisa Ohta 《Mikrochimica acta》2003,141(1-2):87-91
A preconcentration method for antimony in waters involving adsorption on a tantalum wire, followed by electrothermal atomic
absorption spectrometry with a tungsten tube atomizer is described. The best pH for the adsorption of antimony was 2. The
optimal immersing time was 120 s. Under the optimal conditions, the detection limit for antimony by the tantalum wire preconcentration
method was 50 pg/mL (3S/N) and the relative standard deviation was 9.4%. The effects of large amounts of concomitants on the
preconcentration of antimony were evaluated. Even though 103–104 fold excess of matrix elements existed in water, the antimony response was not significantly affected by the matrix elements.
The method with preconcentration on a tantalum wire was applied to the determination of antimony in waters and proved to be
sensitive, simple, and convenient. This adsorption method can be utilized in in-situ sampling of ultra-trace antimony in environmental samples (water). Furthermore, after sampling it is easy to carry and store
the tantalum wire without contamination for a long time. The technique developed was shown to be useful for the determination
of Sb in waste waters at the 1–5 μg/L level.
Received March 20, 2002; accepted June 26, 2002 相似文献
995.
996.
Yasuo Ohta Hiroki Murase Takeji Hashimoto 《Journal of Polymer Science.Polymer Physics》2005,43(19):2639-2652
We investigated the tensile strength and modulus of ultrahigh‐strength polyethylene (UHSPE) fibers obtained by using the special two‐step‐drawing process of as‐spun fiber (ASFs) which were prepared by the so‐called gel‐spinning method. We have found that the higher the ASF's spinning speed is, the higher the attainable tensile strength σf and modulus E are. For all the fibers drawn from ASFs with various spinning speed except for 120 m/min, we have found a master curve for the inverse of σf which is plotted as a function of T1/4E?1/2, where T is the linear density of the drawn fibers, in consistent with the Griffith theory: a thicker fiber obtained with a lower spinning speed exhibits lower strength, although all the AFSs possess the same value of E. This also suggests that a thicker fiber contains more defects which would lead to the Griffith‐type crack propagation breakage. Moreover, from morphological observation of ASFs under transmission electron microscopy, the ASF obtained at a relatively low spinning speed possesses a heterogeneous cross‐sectional morphology, whereas that obtained at relatively high spinning speed possesses a relatively homogenous morphology. We propose that this morphological evidence may account for the experimental findings of the behavior of the mechanical properties described above. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2639–2652, 2005 相似文献
997.
Masataka Nojima Yoshihiro Ohta Tsutomu Yokozawa 《Journal of polymer science. Part A, Polymer chemistry》2014,52(18):2643-2653
Kumada‐Tamao coupling polymerization of 1,4‐dialkoxy‐2‐bromo‐5‐(2‐chloromagnesiovinyl)benzene ( 1 ) and 1,4‐dialkoxy‐2‐(2‐bromovinyl)‐5‐chloromagnesiobenzene ( 2 ) with a Ni catalyst and Suzuki‐Miyaura coupling polymerization of 2‐{2‐[(2,5‐dialkoxy‐4‐iodophenyl)]vinyl}‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane ( 3 ), its bromo counterpart 4 , and 2,5‐dialkoxy‐4‐(2‐bromovinyl)phenylboronic acid ( 5 ) with a Pd initiator were investigated under catalyst‐transfer condensation polymerization conditions for the synthesis of well‐defined poly(p‐phenylenevinylene) (PPV). The Kumada‐Tamao polymerization of vinyl Grignard‐type monomer 1 with Ni(dppp)Cl2 at room temperature did not proceed, whereas aryl Grignard‐type monomer 2 afforded oligomers of low molecular weight. Matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectra of the polymer obtained from 2 implied that the Grignard end group reacted with tetrahydrofuran to terminate polymerization. On the other hand, Suzuki‐Miyaura polymerization of vinyl boronic acid ester type monomers 3 and 4 and phenylboronic acid type monomer 5 with a Pd initiator and aqueous KOH at ?20 °C to room temperature yielded the corresponding PPV with high molecular weight within a few minutes. However, the molecular weight distribution was broad, and MALDI‐TOF mass spectra showed the peaks of polymers bearing no initiator unit at the chain end, as well as those of polymers with the initiator unit. These results indicated that intermolecular chain transfer of the Pd catalyst occurred. Dehalogenation and disproportionation of the growing end also took place as side reactions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2643‐2653 相似文献
998.
Targeting Cancer with PCPA‐Drug Conjugates: LSD1 Inhibition‐Triggered Release of 4‐Hydroxytamoxifen 下载免费PDF全文
Yosuke Ota Dr. Yukihiro Itoh Asako Kaise Dr. Kiminori Ohta Prof. Yasuyuki Endo Dr. Mitsuharu Masuda Dr. Yoshihiro Sowa Prof. Toshiyuki Sakai Prof. Takayoshi Suzuki 《Angewandte Chemie (International ed. in English)》2016,55(52):16115-16118
Targeting cancer with small molecule prodrugs should help overcome problems associated with conventional cancer‐targeting methods. Herein, we focused on lysine‐specific demethylase 1 (LSD1) to trigger the controlled release of anticancer drugs in cancer cells, where LSD1 is highly expressed. Conjugates of the LSD1 inhibitor trans‐2‐phenylcyclopropylamine (PCPA) were used as novel prodrugs to selectively release anticancer drugs by LSD1 inhibition. As PCPA‐drug conjugate (PDC) prototypes, we designed PCPA‐tamoxifen conjugates 1 a and 1 b , which released 4‐hydroxytamoxifen in the presence of LSD1 in vitro. Furthermore, 1 a and 1 b inhibited the growth of breast cancer cells by the simultaneous inhibition of LSD1 and the estrogen receptor without exhibiting cytotoxicity toward normal cells. These results demonstrate that PDCs provide a useful prodrug method that may facilitate the selective release of drugs in cancer cells. 相似文献
999.
Reika Fukuizumi Masahito Ohta Tohru Ozawa 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2008
We study the nonlinear Schrödinger equation with a delta-function impurity in one space dimension. Local well-posedness is verified for the Cauchy problem in H1(R). In case of attractive delta-function, orbital stability and instability of the ground state is proved in H1(R). 相似文献
1000.
Md. Nurul Amin Satoshi Kaneco Yukitake Nakano Hideyuki Katsumata Tohru Suzuki Kiyohisa Ohta 《Mikrochimica acta》2008,161(1-2):73-79
A multi-pumping flow system for the spectrophotometric determination of nitrite and nitrate is described. The determination
of nitrite is based on the Griess-Ilosvay reaction. Nitrate can be determined after its on-line reduction to nitrite using
hydrazine sulphate in alkaline medium. Calibration was linear up to 3 mg NO2
− L−1 with a limit of detection (3sb/S) of 0.013 mg NO2
− L−1 an injection throughput of 55 injections h−1 and a repeatability (RSD) of 0.5% for the direct determination of nitrite. Two calibration graphs within the ranges 0.039–7 mg
NO3
− L−1 and 0.026–5 mg NO2
− L−1 were run for the determination of nitrate and nitrite under reducing conditions, respectively. A limit of detection of 0.039 mg
NO3
− L−1 was obtained. An injection throughput of 27 injections h−1 and an RSD lower than 1.5% were achieved. The method was successfully applied to the determination of nitrite and nitrate
in water samples.
Correspondence: Víctor Cerdà, Department of Chemistry, University of the Balearic Islands, Carretera de Valldemossa Km7.5,
07122 Palma de Mallorca, Spain 相似文献