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901.
Computational fluid dynamics techniques employing primarily steady Reynolds-Averaged Navier-Stokes (RANS) methodology have been recently used to characterize the transitional/turbulent flow field in human airways. The use of RANS implies that flow phenomena are averaged over time, the flow dynamics not being captured. Further, RANS uses two-equation turbulence models that are not adequate for predicting anisotropic flows, flows with high streamline curvature, or flows where separation occurs. A more accurate approach for such flow situations that occur in the human airway is Large Eddy Simulation (LES). The paper considers flow modeling in a pharyngeal airway model reconstructed from cross-sectional magnetic resonance scans of a patient with obstructive sleep apnea. The airway model is characterized by a maximum narrowing at the site of retropalatal pharynx. Two flow-modeling strategies are employed: steady RANS and the LES approach. In the RANS modeling framework both k-epsilon and k-omega turbulence models are used. The paper discusses the differences between the airflow characteristics obtained from the RANS and LES calculations. The largest discrepancies were found in the axial velocity distributions downstream of the minimum cross-sectional area. This region is characterized by flow separation and large radial velocity gradients across the developed shear layers. The largest difference in static pressure distributions on the airway walls was found between the LES and the k-epsilon data at the site of maximum narrowing in the retropalatal pharynx. 相似文献
902.
In an acid medium solution, proteins such as bovine serum albumin, human serum albumin, ovalbumin, hemoglobin, lysozyme, γ‐globulin, α‐chymotrypsin and papain could react with [PdI4]2? by virtue of electrostatic attraction and hydrophobic force to form ion‐association complexes. As a result, the resonance Rayleigh scattering (RRS) and resonance nonlinear scattering such as second‐order scattering (SOS) and frequency doubling scattering (FDS) intensities were enhanced greatly and new scattering spectra appeared. The maximum scattering peaks of RRS, SOS and FDS were at 367, 720 and 370 nm, respectively. The enhanced RRS, SOS and FDS intensities were directly proportional to the concentrations of proteins. The detection limits for the different proteins were 2.4–11.8 ng/mL for RRS method, 9.5–47.9 ng/mL for SOS method and 4.6–18.5 ng/mL for FDS method. In this work, the influences of the interaction of [PdI4]2? with proteins on spectral characteristics of RRS, SOS and FDS were investigated and the optimum conditions were tested. Meanwhile, the effects of coexisting substances were tested and the results showed that the method exhibited a good selectivity. Based on the above research, a highly sensitive, simple and rapid method for the determination of trace amounts of proteins by resonance light scattering technique has been developed. It can be applied to the determination of proteins in tablet, human serum and urine samples. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
903.
Yawen Zeng Luxiang Wang Juan Du Jiafu Liu Shuming Yang Xiaoying Pu Fenghui Xiao 《植物学报(英文版)》2009,51(5):466-475
The phylogenetic relationship for classification traits and eight mineral elements in brown rice (Oryza sativa L.) from Yunnan Province in China was carried out using microwave assisted digestion followed by inductively coupled plasma atomic emission spectroscopy, and the analytical procedures were carefully controlled and validated. In general, the results show that the mean levels of K, Ca, Mg, Fe and Cu in brown rice for 789 accessions of rice landraces was distinctly lower than that of improved cultivars. They further demonstrate that Ca plays an important role in the differentiation of subspecies indica-japonica, especially to enhance adaptation of cold stress, and that five mineral elements in brown rice enhance the eurytopicity from landrace to improved cultivar. Hierarchical cluster analysis, using average linkage from SPSS software based on eight mineral elements in brown rice, showed that Yunnan rice could be grouped into rice landrace and improved cultivar, with the rice landrace being further clustered into five subgroups, and that, interestingly, purple rice does not cluster with either of the groups. Our present data confirm that indica is the closest relative of late rice and white rice, and that they constitute rice landraces together, whereas japonica is the closest relatives of non-nuda, early-mid and glutinous rice. It is further shown that japonica, non-nuda, early-mid, glutinous, white and red rice might be more primitive than indica, nuda, late, non-glutinous and purple rice, respectively. 相似文献
904.
ent-Kaurene diterpenoids, phyllostachysins D-H (1-5), together with nine known compounds, rabdoloxins A-B (6-7), rabdoinflexin B (8), amethystoidin A (9), rabdokunmin D (10), macrocalyxin E (11), 5,7-dihydroxy-4'-hydroxylflavone (12), oleanolic acid (13) and daucosterol (14), were isolated from aerial parts of Isodon phyllostachys. Structures were elucidated on the basis of spectroscopic methods, especially using 2D-NMR spectroscopic analyses. All ent-kaurenoids were tested for their cytotoxic effects against K562 cells. Compound 9 was the most potent with an IC50 value of 0.69 microg/ml. 相似文献
905.
906.
A method for quantitative analysis of spatially variable physiological processes across leaf surfaces 总被引:1,自引:0,他引:1
Many physiological processes are spatially variable across leaf surfaces. While maps of photosynthesis, stomatal conductance,
gene expression, water transport, and the production of reactive oxygen species (ROS) for individual leaves are readily obtained,
analytical methods for quantifying spatial heterogeneity and combining information gathered from the same leaf but with different
instruments are not widely used. We present a novel application of tools from the field of geographical imaging to the multivariate
analysis of physiological images. Procedures for registration and resampling, cluster analysis, and classification provide
a general framework for the analysis of spatially resolved physiological data. Two experiments were conducted to illustrate
the utility of this approach. Quantitative analysis of images of chlorophyll fluorescence and the production of ROS following
simultaneous exposure of soybean leaves to atmospheric O3 and soybean mosaic virus revealed that areas of the leaf where the operating quantum efficiency of PSII was depressed also
experienced an accumulation of ROS. This correlation suggests a causal relationship between oxidative stress and inhibition
of photosynthesis. Overlaying maps of leaf surface temperature and chlorophyll fluorescence following a photoinhibition treatment
indicated that areas with low operating quantum efficiency of PSII also experienced reduced stomatal conductance (high temperature).
While each of these experiments explored the covariance of two processes by overlaying independent images gathered with different
instruments, the same procedures can be used to analyze the covariance of information from multiple images. The application
of tools from geographic image analysis to physiological processes occurring over small spatial scales will help reveal the
mechanisms generating spatial variation across leaves. 相似文献
907.
908.
909.
为从高表达苯丙氨酸解氨酶(PAL)的基因工程乳酸乳球菌NZ3900/pNZ8149-palxt中有效提取所表达的PAL酶,针对乳酸乳球菌的特点,结合各种物理、化学、生物学等方法,探索出一条简便、高效的技术路线.对提取物进行了酶活性测定、分析及细菌活性鉴定.结果表明,该混合法可以完全导致细菌死亡,所提取的酶蛋白结构完整,其酶活性达到了等量活菌的92.5%,且该方法中所用到的各种试剂对体外培养细胞的生长无明显影响,为PAL酶在科研及生物医药领域的应用提供了可靠来源. 相似文献
910.