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排序方式: 共有522条查询结果,搜索用时 78 毫秒
41.
W.C. Sperry G.A. Beer M.S. Dixit S.K. Kim J.A. MacDonald G.R. Mason A. Olin R.M. Pearce C. Sabev C. Wiegand 《Physics letters. [Part B]》1979,86(1):29-30
The intensity per stopped π?of|Δn|=2 pionic X-rays are observed to have larger variations with atomic number Z than do the |Δn|=1. The 6–4 intensity has a well-defined maximum at Z=34 with a FWHM of ΔZ ~10. 相似文献
42.
Bulk d.c. conductivities of the electronically conducting transition metal oxide glasses in the system xV2O550B2O3(50?x)TeO2 were measured at different temperatures in the range 310–623 K. The dependence of conductivity on composition is explained on the basis of the role of TeO2 as a modifier or impurity. The observed kink in the log σ vs 1/T characteristic of the glasses is interpreted as being due to switching over of the conduction mechanism from one type to the other. The activation energies are fitted in a linear relation of the type Eg = A ? BP, where A and B are constants and P, the composition parameter. Comparing the results obtained with those of previous workers in the V2O5P2O5 and V2O5B2O3 systems, a physical analysis is presented. 相似文献
43.
E. Olusegun George Govind S. Mudholkar 《Annals of the Institute of Statistical Mathematics》1981,33(1):125-129
Summary A functional form of the characteristic function of the sample median of three variates is shown to characterize the logistic
distribution. A consequence of this is a characterization of the logistic in terms of the Laplace distribution.
Research sponsored in part by the Air Force Office of Scientific Research, Air Force Systems Command, USAF under Grant No.
AFOSR-77-3360. The United States Govenment is authorized to reproduce and distribute reprints for governmental purposes notwith-standing
any copyright notation hereon. 相似文献
44.
Dewald EL Suter LJ Landen OL Holder JP Schein J Lee FD Campbell KM Weber FA Pellinen DG Schneider MB Celeste JR McDonald JW Foster JM Niemann C Mackinnon AJ Glenzer SH Young BK Haynam CA Shaw MJ Turner RE Froula D Kauffman RL Thomas BR Atherton LJ Bonanno RE Dixit SN Eder DC Holtmeier G Kalantar DH Koniges AE Macgowan BJ Manes KR Munro DH Murray JR Parham TG Piston K Van Wonterghem BM Wallace RJ Wegner PJ Whitman PK Hammel BA Moses EI 《Physical review letters》2005,95(21):215004
The first hohlraum experiments on the National Ignition Facility (NIF) using the initial four laser beams tested radiation temperature limits imposed by plasma filling. For a variety of hohlraum sizes and pulse lengths, the measured x-ray flux shows signatures of filling that coincide with hard x-ray emission from plasma streaming out of the hohlraum. These observations agree with hydrodynamic simulations and with an analytical model that includes hydrodynamic and coronal radiative losses. The modeling predicts radiation temperature limits with full NIF (1.8 MJ), greater, and of longer duration than required for ignition hohlraums. 相似文献
45.
Embryogenic tissues of Dioscorea bulbifera were cryopreserved using the encapsulation-dehydration technique. Genetic stability of plants regenerated from cryopreserved embryogenic tissues was assessed using molecular, biochemical and morphological analysis. The random amplified polymorphic DNA (RAPD) analysis of 60 cryopreserved-derived and 20 in vitro grown (control) plantlets showed that 10 primers produced 62 clear reproducible DNA fragment profiles. The amplification products were monomorphic for all the plantlets except one. A total of 4960 DNA fragments were obtained from this study showing no variation in RAPD profiles. The diosgenin content of cryopreserved-derived plants, analyzed using HPLC, was similar to that of control plants. Morphology and the ability to form microtuber were also found to be unaltered in cryopreserved embryo-derived plantlets. Thus, the D. bulbifera plants regenerated from cryopreserved embryogenic tissues were genetically stable at the molecular, biochemical and morphological levels. 相似文献
46.
Vishalkumar R. More Umesh S. Mote Shivajirao R. Patil Govind B. Kolekar 《Journal of solution chemistry》2010,39(1):97-106
The binding of riboflavin (RBF) to norfloxacin (NF) was investigated by spectroscopic techniques. The results revealed that
RBF caused the fluorescence quenching of NF by complex formation. The binding parameters and corresponding thermodynamic parameters ΔH, ΔG and ΔS at different temperatures were calculated. The negative enthalpy (ΔH) and positive entropy (ΔS) values indicated that both hydrogen bond and hydrophobic forces played major roles in the binding of RBF to NF. The distance
r between donor (NF) and acceptor (RBF) was obtained according to the Forster’s theory of non-radiative energy transfer. The
method of quenching was successfully applied for the determination of riboflavin from pharmaceutical samples. 相似文献
47.
Experimental measurements of power spectra of a single longitudinal and transverse mode ring dye laser are presented that reveal the critical slowing down of the laser near threshold. External pump noise serves as a probe of the frequency response of the dye laser. Detailed comparisons of the spectral characteristics with computer simulations and an approximate analytic theory are given. The dynamics of spatial pattern formation in a multimode dye laser is examined through measurements of first-passage-time distributions. A comparison of the experiments with computer simulations based on a simple theoretical model of the two-mode laser shows qualitative agreement. These measurements indicate that there are a variety of complex phenomena associated with the transverse mode pattern formation dynamics that need to be addressed theoretically and studied further experimentally. 相似文献
48.
Rahul P. Dixit Chandrashekhar R. Barhate Mangal S. Nagarsenker 《Chromatographia》2008,67(1-2):101-107
Simvastatin and ezetimibe are used to treat hyperlipidemia. A simple, selective and stability-indicating HPTLC method has
been established for analysis of simvastatin and ezetimibe. The method has been validated so that both drugs can routinely
be analyzed simultaneously. The method uses aluminum-backed silica gel 60F254 TLC plates as stationary phase with n-hexane–acetone 6:4 (v/v) as mobile phase. Densitometric analysis of both drugs was carried out in absorbance mode at 234 nm. This system was found
to give compact bands for simvastatin and ezetimibe (R
F 0.39 ± 0.05 and 0.50 ± 0.05, respectively). Linear relationships were obtained between response and amount of drug in the
range 200–1,600 ng per band with high correlation coefficients (r
2 = 0.9917 ± 0.0018 for simvastatin and r
2 = 0.9927 ± 0.0021 for ezetimibe). The method was validated for precision, robustness, and recovery. The limits of detection
and quantitation were 25 and 150 ng per band, respectively. Simvastatin and ezetimibe were subjected degradation by acid,
pH 6.8 phosphate buffer, oxidation, dry heat, and wet heat. The degradation products were well resolved from the pure drug
with significantly different R
F values. Because the method could effectively separate the drug from its degradation products, it can be used for stability-indicating
analysis. 相似文献
49.
Govind V. Waghmare Abhishek Chatterji Virendra K. Rathod 《Applied biochemistry and biotechnology》2017,183(3):792-806
This work illustrates the enzymatic synthesis of cinnamyl butyrate by esterification of butyric acid and cinnamyl alcohol. Experiments were performed to study the various operating parameters such as molar ratio, enzyme concentration, temperature, and speed of agitation. Also, the suitable kinetic model for esterification reaction was predicted and the various kinetic parameters were determined. It has been observed that the experimental results agree well with the simulated results obtained by following the ping-pong bi-bi mechanism with dead-end inhibition by both the substrate acid and alcohol. The highest 90% conversion of butyric acid was observed after 12 h at the following reaction conditions: substrate molar ratio 1:2 (butyric acid/cinnamyl alcohol), temperature 50 °C, enzyme loading 2% (with respect to the weight of the substrates), and agitation speed 250 rpm. Diffusional mass transfer limitations between substrate and enzyme surface do not show significant effect on reaction kinetics. Enzyme reusability study reveals that it retains 85% of its catalytic activity after five consecutive cycles. 相似文献
50.