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221.
L. Mika 《Experimental Thermal and Fluid Science》2011,35(6):939-947
The paper presents the results of the experimental research on the ice slurry loss coefficient during its flow through sudden contractions. Experimental studies were conducted using a few of the most common contractions of copper pipes. Six contraction ratios were covered: 0.500, 0.615, 0.650, 0.769, 0.800 and 0.813. In the experimental research, the mass fraction of solid particles in the slurry ranged from 20 to 30 (20%, 25%, 30%). Research results allow for determining the theoretical correlation for the ice slurry, in order to calculate the loss coefficient in contractions during laminar flow. The results of experimental investigations also confirmed that the loss coefficients in contractions in turbulent (transitional) flow of the ice slurry are the same as in the case of Newtonian liquids. The paper also presents original theoretical correlation for calculating the kinetic energy correction factor in the laminar range flow of liquid in the Bingham model. This correlation is used in this work for calculation of the ice slurry flow through contractions. 相似文献
222.
已有的土壤有机质含量估测模型大多以光谱特征波段、线性和非线性模型为基础,较少考虑通过拓展样本数据建模集来提高模型的估测能力。为进一步提高土壤有机质高光谱反演模型估测精度,提出利用生成式对抗网络(GAN)合成伪高光谱数据和有机质含量的动态估测模型。选取湖南省长沙市及周边区域的水稻田为研究对象,采集土样和实测高光谱数据(350~2 500 nm),室内化学测定有机质含量。以高光谱数据和有机质含量为基础,利用生成式对抗网络生成等量新数据, 结合原始数据建模集组成增强建模集。在GAN正式训练中,每轮训练完成后,设置4个观测点(对应增强建模集中含50,100,150和239个生成样本),动态构建交叉验证岭回归(RCV)、偏最小二乘回归(PLSR)和BP神经网络(BPNN)土壤有机质含量估测模型(分别简称GAN-RCV,GAN-PLSR和GAN-BPNN),并在相同测试集上实施模型评估。实验结果表明:(1)原始数据建模集上拟合的估测模型中,交叉验证岭回归表现最佳,决定系数(R2)和均方根误差(RMSE)分别为0.831 1和0.189 6;(2)GAN的150轮正式训练中,增强建模集上动态构建的GAN-RCV,GAN-PLSR和GAN-BPNN模型性能显著提高,具体表现为:GAN-RCV的R2取得最大值0.890 9(RMSE 0.153 7)、最小值0.850 5 (RMSE 0.18)与平均值0.868 7(RMSE 0.168 6),最大R2比建模集上拟合的RCV提高了7.2%(RMSE降低了18.9%),GAN-PLSR获得R2最大值0.855 4(RMSE 0.176 9)、最小值0.727 0 (RMSE 0.243 2)与平均值0.780 1 (RMSE 0.217 7),最大R2比建模集上拟合的PLSR提高了20.6%(RMSE降低了29.5%),GAN-BPNN表现最佳,R2取得最大值0.905 2(RMSE 0.143 3)、最小值0.801 7(RMSE 0.207 3)与平均值0.868 1(RMSE 0.168 6),最大R2比建模集上拟合的BPNN提高了30.8%(RMSE降低了44.5%);(3)随着增强建模集中生成样本数量增加,模型精度提升效果呈先升后降趋势,4个观测点中第3个观测点的模型性能提升最显著。充分的实验表明:基于GAN动态构建的有机质含量估测模型显著改善了模型预测性能。依据测试集上的评估结果,可择优使用最佳模型进行后续土壤有机质含量估测。 相似文献
223.
Atom interferometry gravity-gradiometer for the determination of the Newtonian gravitational constant G 总被引:1,自引:0,他引:1
A. Bertoldi G. Lamporesi L. Cacciapuoti M. de Angelis M. Fattori T. Petelski A. Peters M. Prevedelli J. Stuhler G. M. Tino 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(2):271-279
We developed a gravity-gradiometer based on atom interferometry for the determination of the Newtonian gravitational constant
G.
The apparatus, combining a Rb fountain, Raman interferometry and a juggling scheme for fast launch of two atomic clouds, was
specifically
designed to reduce possible systematic effects. We present instrument performances and preliminary results for the measurement
of G with a relative uncertainty of 1%. A discussion of projected accuracy for G measurement using this new scheme shows
that the results of the experiment will be significant to discriminate between previous inconsistent values. 相似文献
224.
Jean-Louis Féménias 《Journal of Molecular Spectroscopy》2005,232(1):80-101
Applications of the χ2 test, the F test, the Durbin-Watson d test, and the f (or Sign) test, to examples of correlated data treatment, show important drawbacks with the d test and (apparently) with the f test. An analytical approach based on residual analysis suggests an improvement in their use that leads to better results at lowest order; it also points out a distinction between goodness-of-fit tests, as the f test, and goodness-of-modeling tests, as the χ2 and F tests. The residual analysis method is applied to the same examples; it looks faster, simpler, and often more accurate than the classical ones. 相似文献
225.
Gui-Jun Ding Rong-Gang Ping Mu-Lin Yan 《The European Physical Journal A - Hadrons and Nuclei》2006,28(3):351-360
X(1835) has been treated as a baryonium with sizable gluon content, and to be almost flavor singlet. This picture allows us
to rationally understand X(1835) production in J/ψ radiative decays, and its large couplings with pˉ, η′ππ. The processes ϒ(1S) → γX(1835) and J/ψ → ωX(1835) have been examined. It has been found that Br(ϒ(1S) → γX(1835))Br(X(1835) → pˉ) < 6.45×10-7, which is compatible with CLEO's recent experimental result (Phys. Rev. D 73, 032001 (2006) hep-ex/0510015). The branching fractions Br(J/ψ → ωX(1835)), Br(J/ψ → ρX(1835)) with X(1835) → pˉ and X(1835) → η′π+π- have been estimated by the quark-pair creation model. We show that they are heavily suppressed, so the signal of X(1835) is very difficult, if not impossible, to be observed in these processes. The experimental checks for these estimations
are expected. The existence of the baryonium nonet is conjectured, and a model-independent derivation of their production
branching fractions is presented. 相似文献
226.
P. Bonifazi 《Il Nuovo Cimento C》1990,13(1):35-47
Summary The data obtained with three highly sensitive gravitational wave antennas have been used to establish an improved observational
upper limit on the flux of impulsive gravitational waves. Preliminary results under the assumption of a source located in
the center of the Galaxy are also reported.
To speed up publication, the proofs were not sent to the authors and were superised by the Scientific Committee. 相似文献
227.
The goal of this research was to determine whether there is any interaction between the type of constitutive equation used and the degree of mesh refinement, as well as how the type of constitutive equation might affect the convergence and quality of the solution, for a planar 4:1 contraction in the finite eiement method. Five constitutive equations were used in this work: the Phan-Thien–Tanner (PTT), Johnson–Segalman (JS), White–Metzner (WM), Leonov-like and upper convected Maxwell (UCM) models. A penalty Galerkin finite element technique was used to solve the system of non-linear differential equations. The constitutive equations were fitted to the steady shear viscosity and normal stress data for a polystyrene melt. In general it was found that the convergence limit based on the Deborah number De and the Weissenberg number We varied from model to model and from mesh to mesh. From a practical point of view it was observed that the wall shear stress in the downstream region should also be indicated at the point where convergence is lost, since this parameter reflects the throughput conditions. Because of the dependence of convergence on the combination of mesh size and constitutive equation, predictions of the computations were compared with birefringence data obtained for the same polystyrene melt flowing through a 4:1 planar contraction. Refinement in the mesh led to better agreement between the predictions using the PTT model and flow birefringence, but the oscillations became worse in the corner region as the mesh was further refined, eventually leading to the loss of convergence of the numerical algorithm. In comparing results using different models at the same wall shear stress conditions and on the same mesh, it was found that the PTT model gave less overshoot of the stresses at the re-entrant corner. Away from the corner there were very small differences between the quality of the solutions obtained using different models. All the models predicted solutions with oscillations. However, the values of the solutions oscillated around the experimental birefringence data, even when the numerical algorithm would not converge. Whereas the stresses are predicted to oscillate, the streamlines and velocity field remained smooth. Predictions for the existence of vortices as well as for the entrance pressure loss (ΔPent) varied from model to model. The UCM and WM models predicted negative values for ΔPent. 相似文献
228.
In this paper, we present a framework and two linear time algorithms for obtaining circular drawings of graphs. The first technique produces circular drawings of biconnected graphs and finds a zero crossing circular drawing if one exists. The second technique finds multiple embedding circle drawings. Techniques for the reduction of edge crossings are also discussed. Results of experimental studies are included. 相似文献
229.
An HPLC method has been developed for the separation of valdecoxib and a degradation product consisting of α and β-N-lactosyl sulfonamide, i.e. α and β anomers (SC-77852). Best results were achieved with a Chromolith Performance RP-18e column (100 mm × 4.6 mm), macropore size 2 μm, mesopore size 13 nm, with an eluent of methanol:water containing a 1% solution of TEA (36:64 v/v), pH 7.4 (adjusted with 85% orthophosphoric acid), at 22 °C. Detection was at 220 nm. The method was validated for its selectivity, linearity, precision (repeatability) and robustness. Quantitation and detection limits were determined for both valdecoxib and SC-77852. Method robustness was further evaluated by performing 23 full factorial design experiments. The final step, optimisation of the variables, was performed using response surface design. The validated method was used for assay of valdecoxib and SC-77852 in Bextra® film-coated tablets. 相似文献
230.
Predicting the vibro-acoustic behaviour of a structure is usually done by using the well established finite element (FE) method and boundary element method. This paper presents a vibro-acoustic prediction case performed on a metal box using less accurate but simplified methods: sub-structuring for the calculation of the dynamic response of the structure, and a monopole distribution for the radiated noise calculation. Both are less accurate but faster methods than previous ones. An experimental validation was performed. It led to the conclusion that these methods give precise results and are sufficient for the pre-design of structures in the low frequency domain. However, this conclusion must be moderated by the fact that in spite of the simplicity of the structure, the FE model had to be adjusted to the experiments to yield to a result close to the experiments. 相似文献