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991.
Lingyan Cao Jerome A. Werkmeister Jing Wang Veronica Glattauer Keith M. McLean Changsheng Liu 《Biomaterials》2014
Although rhBMP-2 has excellent ability to accelerate the repair of normal bone defects, limitations of its application exist in the high cost and potential side effects. This study aimed to develop a composite photopolymerisable hydrogel incorporating rhBMP-2 loaded 2-N, 6-O-sulfated chitosan nanoparticles (PH/rhBMP-2/NPs) as the bone substitute to realize segmental bone defect repair at a low growth factor dose. Firstly rhBMP-2 loaded 2-N, 6-O-sulfated chitosan nanoparticles (rhBMP-2/NPs) were prepared and characterized by DLS and TEM. Composite materials, PH/rhBMP-2/NPs were developed and investigated by SEM-EDS as well as a series of physical characterizations. Using hMSCs as an in vitro cell model, composite photopolymerisable hydrogels incorporating NPs (PH/NPs) showed good cell viability, cell adhesion and time dependent cell ingrowth. In vitro release kinetics of rhBMP-2 showed a significantly lower initial burst release from the composite system compared with the growth factor-loaded particles alone or encapsulated directly within the hydrogel, followed by a slow release over time. The bioactivity of released rhBMP-2 was validated by alkaline phosphatase (ALP) activity as well as a mineralization assay. In in vivo studies, the PH/rhBMP-2/NPs induced ectopic bone formation in the mouse thigh. In addition, we further investigated the in vivo effects of rhBMP-2-loaded scaffolds in a rabbit radius critical defect by three dimensional micro-computed tomographic (μCT) imaging, histological analysis, and biomechanical measurements. Animals implanted with the composite hydrogel containing rhBMP-2-loaded nanoparticles underwent gradual resorption with more pronounced replacement by new bone and induced reunion of the bone marrow cavity at 12 weeks, compared with animals implanted with hydrogel encapsulated growth factors alone. These data provided strong evidence that the composite PH/rhBMP-2/NPs are a promising substitute for bone tissue engineering. 相似文献
992.
Xiaohua He Liyuan Liang Meiran Xie Yiqun Zhang Shaoliang Lin Deyue Yan 《Macromolecular chemistry and physics.》2007,208(16):1797-1802
A new strategy to synthesize a series of well‐defined amphiphilic PEO‐b‐PS‐b‐PCL block copolymers is presented. First, bromine‐terminated diblock copolymers PEO‐b‐PS‐Br are prepared by ATRP of styrene, and converted into azido‐terminated PEO‐b‐PS‐N3 diblock copolymers. Then propargyl‐terminated PCL is prepared by ROP of ε‐caprolactone. The PEO‐b‐PS‐b‐PCL triblock copolymers with from 1.62 × 104 to 1.96 × 104 and a narrow PDI from 1.09 to 1.19 are finally synthesized from these precursors. The structures of these triblock copolymers and their precursors have been characterized by NMR, IR, and GPC analysis.
993.
该文研究的新型舌图像客观化采集装置,主要用于采集患者舌体的图像。与国内外同类产品相比,该装置提出了动态采集的新概念,通过嵌入式系统控制摄像头运动实现对舌面的垂直拍摄。该采集方式下,舌图像具有更高的保真度,更加完整清晰的舌体特征,以及更加逼近自然光照射下的舌面色泽。较好地克服了原先由于静态采集带来的舌体信息反映不完全的弊端。 相似文献
994.
Kinetics of hydroxyapatite precipitation at pH 10 to 11 总被引:8,自引:0,他引:8
The mechanism and kinetics of hydroxyapatite (HAP) precipitation from aqueous solution at the conditions of pH 10-11 and at calcium ion concentrations of more than 0.5 mol/l were investigated. The results show that the reaction undergoes the following process: transferring from octacalcium phosphate (OCP) to amorphous calcium phosphate (ACP) rapidly, and then from ACP to calcium-deficient hydroxyapatite (DAP) and HAP. DAP was the non-stoichiometric material that ACP converts to HAP. Reaction temperature greatly affects the reaction rate of the conversion from ACP to HAP. It takes about 24 h to form pure-phase HAP at 25 degrees C while it takes only 5 min at 60 degrees C. The temperature also has a great deal of influence on the particle size and morphology of precipitated hydroxyapatite. The reaction of transformation from ACP to DAP was second order and the activation energy was 95 kJ/mol (22.7 kCal/mol) and therefore it was inferred that the conversion reaction was a surface control process. 相似文献
995.
《Anaesthesia and Intensive Care Medicine》2008,9(10):451-453
Drugs that lower blood glucose are used to treat diabetes mellitus, the major clinical use of drugs affecting blood sugar. Type 1 diabetes is treated with insulin, of which the human sequence or analogues thereof are more commonly used than the bovine or porcine varieties. Insulin may also be used for non-insulin-dependent diabetes (type 2) when the oral hypoglycaemic drugs are inadequate to control the hyperglycaemia. These include the sulphonylureas, for example chlorpropamide, glibenclamide, and the meglitinides, for example repaglinide, nateglinide, which stimulate insulin release. The biguanide metformin and the glitazones increase glucose uptake into tissue thus reducing insulin insensitivity. α-Glucosidase inhibitors, for example acarbose, delay glucose absorption from the gut. Drugs that raise blood glucose include the natural hormone glucagon and the drug diazoxide; both of which are used to treat hypoglycaemia which occurs as a result of an insulinoma or excessive use of hypoglycaemic agents. 相似文献
996.
997.
Seher Ozkan Dilhan M. Kalyon Xiaojun Yu Craig A. McKelvey Michael Lowinger 《Biomaterials》2009,30(26):4336-4347
Here we demonstrate the use of a twin screw extrusion/spiral winding (TSESW) process to generate protein-encapsulated tissue engineering scaffolds. Bovine serum albumin (BSA) was distributed into PCL matrix using both wet and hot melt extrusion methods. The encapsulation efficiency and the time-dependent release rate, as well as the tertiary structure of BSA (via circular dichroism), were investigated as a function of processing method and conditions. Within the relatively narrow processing window of this demonstration study it was determined that the wet extrusion method gave rise to greater stability of the BSA on the basis of circular dichroism data. The rate of proliferation of human fetal osteoblast (hFOB) cells and the rate of mineral deposition were found to be greater for wet extruded scaffolds, presumably due to the important differences in surface topographies (smoother scaffold surfaces upon wet extrusion). Overall, these findings suggest that the twin screw extrusion/spiral winding (TSESW) process offers significant advantages and flexibility in generating a wide variety of non-cytotoxic tissue engineering scaffolds with controllable distributions of porosity, physical and chemical properties and protein concentrations that can be tailored for the specific requirements of each tissue engineering application. 相似文献
998.
Biomolecules–carbon nanotube (CNT) interactions are of great importance in CNT-based drug delivery systems and biomedical devices. In this study, a spontaneous encapsulation of a globular protein into the CNT was observed through molecular dynamics simulation. The free energy of the system was found to be decreased after the encapsulation, which is the most fundamental reason for this spontaneous process. The system enthalpy decrease was found to make a dominant contribution to the free-energy change, and the system entropy increase also contributes to the spontaneous process. During the insertion, the protein makes a stepwise conformational change to maximize its affinity to the CNT walls as well as the protein–CNT interactions, mainly resulting in the deformation of the β-sheets in the protein. As a whole, the CNT was considered to attract protein molecules nonspecifically although the groups with high hydrophobicity and/or aromatic rings show great affinity. 相似文献
999.
Background
Gallbladder cancer is the most common billiary tract malignancy and carries a very poor prognosis. Somatostatin was recently shown to play an important role in the development of various tumors. In the current study, we evaluated the effect of doxorubicin on the chemosensitivity of gallbladder cancer cells and xenograft growth after treatment with somatostatin. 相似文献1000.
《Neural networks》2007,20(1):139-152
Canonical correlation analysis (CCA) is a classical tool in statistical analysis to find the projections that maximize the correlation between two data sets. In this work we propose a generalization of CCA to several data sets, which is shown to be equivalent to the classical maximum variance (MAXVAR) generalization proposed by Kettenring. The reformulation of this generalization as a set of coupled least squares regression problems is exploited to develop a neural structure for CCA. In particular, the proposed CCA model is a two layer feedforward neural network with lateral connections in the output layer to achieve the simultaneous extraction of all the CCA eigenvectors through deflation. The CCA neural model is trained using a recursive least squares (RLS) algorithm. Finally, the convergence of the proposed learning rule is proved by means of stochastic approximation techniques and their performance is analyzed through simulations. 相似文献