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991.
992.
Key steps in type III secretion system (T3SS) towards translocon assembly with potential sensor at plant plasma membrane 下载免费PDF全文
Many plant‐ and animal‐pathogenic Gram‐negative bacteria employ the type III secretion system (T3SS) to translocate effector proteins from bacterial cells into the cytosol of eukaryotic host cells. The effector translocation occurs through an integral component of T3SS, the channel‐like translocon, assembled by hydrophilic and hydrophobic proteinaceous translocators in a two‐step process. In the first, hydrophilic translocators localize to the tip of a proteinaceous needle in animal pathogens, or a proteinaceous pilus in plant pathogens, and associate with hydrophobic translocators, which insert into host plasma membranes in the second step. However, the pilus needs to penetrate plant cell walls in advance. All hydrophilic translocators so far identified in plant pathogens are characteristic of harpins: T3SS accessory proteins containing a unitary hydrophilic domain or an additional enzymatic domain. Two‐domain harpins carrying a pectate lyase domain potentially target plant cell walls and facilitate the penetration of the pectin‐rich middle lamella by the bacterial pilus. One‐domain harpins target plant plasma membranes and may play a crucial role in translocon assembly, which may also involve contrapuntal associations of hydrophobic translocators. In all cases, sensory components in the target plasma membrane are indispensable for the membrane recognition of translocators and the functionality of the translocon. The conjectural sensors point to membrane lipids and proteins, and a phosphatidic acid and an aquaporin are able to interact with selected harpin‐type translocators. Interactions between translocators and their sensors at the target plasma membrane are assumed to be critical for translocon assembly. 相似文献
993.
994.
Runbi Ji Bin Zhang Xu Zhang Jianguo Xue Xiao Yuan Yongmin Yan Mei Wang Wei Zhu Hui Qian Wenrong Xu 《Cell cycle (Georgetown, Tex.)》2015,14(15):2473-2483
Mesenchymal stem cells (MSCs) play an important role in chemoresistance. Exosomes have been reported to modify cellular phenotype and function by mediating cell-cell communication. In this study, we aimed to investigate whether exosomes derived from MSCs (MSC-exosomes) are involved in mediating the resistance to chemotherapy in gastric cancer and to explore the underlying molecular mechanism. We found that MSC-exosomes significantly induced the resistance of gastric cancer cells to 5-fluorouracil both in vivo and ex vivo. MSC-exosomes antagonized 5-fluorouracil-induced apoptosis and enhanced the expression of multi-drug resistance associated proteins, including MDR, MRP and LRP. Mechanistically, MSC-exosomes triggered the activation of calcium/calmodulin-dependent protein kinases (CaM-Ks) and Raf/MEK/ERK kinase cascade in gastric cancer cells. Blocking the CaM-Ks/Raf/MEK/ERK pathway inhibited the promoting role of MSC-exosomes in chemoresistance. Collectively, MSC-exosomes could induce drug resistance in gastric cancer cells by activating CaM-Ks/Raf/MEK/ERK pathway. Our findings suggest that MSC-exosomes have profound effects on modifying gastric cancer cells in the development of drug resistance. Targeting the interaction between MSC-exosomes and cancer cells may help improve the efficacy of chemotherapy in gastric cancer. 相似文献
995.
Kang Yun Hee Ji Na Young Lee Chung Il Lee Hee Gu Kim Jae Wha Yeom Young IL Kim Dae Ghon Yoon Seung Kew Kim Jong Wan Park Pil Je Song Eun Young 《Amino acids》2011,40(3):1003-1013
Amino Acids - Endothelial cell-specific molecule-1 (ESM-1) is a secretory proteoglycan comprising a mature polypeptide of 165 amino acids and a single dermatan sulfate. The aim of this study was to... 相似文献
996.
Ji S Guo Q Yue Q Wang L Wang H Zhao J Dong R Liu J Jia J 《Biosensors & bioelectronics》2011,26(5):2067-2073
Fabrication of sub-monolayer array of Pt nanoparticles (PtNPs) assembled at nucleobases terminated layers and their application into H(2)O(2) and glucose sensing were reported. To prepare such a PtNPs assembly, 3-mercaptopropionic acid (MPA), Zr(4+), nucleotide-5'-monophosphate (NTMP including guanosine, adenosine, cytidine, uridine-5'-monophosphate, and abbreviations were GMP, AMP, CMP, UMP, respectively) were adsorbed onto Au substrate sequentially to form nucleobases terminated surface and Zr(4+) acted as binder to link carboxylic and phosphoric groups (NTMP/Zr(4+)/MPA/Au). Complexation of cisplatin, cis-Pt(NH(3))(2)Cl(2), with terminated nucleobases and following electrochemical reduction of surface-bound cisplatin gave PtNPs attached surface. Different PtNPs coverage or particle density was obtained depending on the NTMP used and decreased in the order: PtNPs/GMP/Zr(4+)/MPA/Au>PtNPs/AMP/Zr(4+)/MPA/Au>PtNPs/CMP/Zr(4+)/MPA/Au>PtNPs/UMP/Zr(4+)/MPA/Au. The surface loading of Pt was between 160 and 16 ng/cm(2). The as prepared PtNPs can be used as electrocatalysts for H(2)O(2) sensing (detection limit of H(2)O(2)<100 nM) and the sensitivity increased with decreasing PtNPs density. After adsorption of glucose oxidase, the modified electrode can be used as enzymatic electrode for glucose sensing and a detection limit of 38.5 μM was achieved. This study provided an example of fabricating PtNP arrays utilising surface complexation of cisplatin with nucleobases. The advantage of this method is that the NP density can be controlled through changing nucleobases or Pt complexes used to obtain suitable kinetics of the complexation reactions. Additionally, the PtNPs sub-monolayer as prepared has high sensitivity for H(2)O(2) sensing even at a very low loading of Pt. 相似文献
997.
The main goal of this research was to investigate how different factors influence membrane fouling. The impact of the different concentrations of activated sludge and the amount of extracellular polymer substances (EPS) were monitored. Two pilot plants with submerged membrane modules (hollow fiber and flat sheet) were operated and the raw wastewater was used.Humic substances were identified as the major components of EPS in the activated sludge (more than 34%) in both pilot plants. As the basic constituent in permeate, humic substances were identified as the most dominant components in the effluent (61%) in both pilot plants. Conversely, proteins were mostly analyzed in permeate and supernatant below the detection limit. The total amount of EPS [mg g−1 (VSS)] was similar for concentrations of activated sludge 6, 10 and 14 g L−1. Carbohydrates were identified as the component of EPS which tends most to clog membranes. 相似文献
998.
Ustilago maydis is known to produce glycolipid-type biosurfactants. Here, we show that U. maydis is able to efficiently convert biodiesel-derived crude glycerol to glycolipids. We have optimized the medium composition and environmental factors for bioconversion of crude glycerol to glycolipids. The synthetic medium (MinCG) contains 50 g L−1 crude glycerol and 20.3 mg L−1 ammonium citrate as the carbon and nitrogen sources, respectively. The supplementation of trace amount of amino acids, Group-B vitamins and precursors of glycolipids, mannose and erythritol, also improved the final yield. At pH 4.0 and 30 °C, 32.1 g L−1 total glycolipids was produced in a 8.2-day fed-batch bioprocess. Methanol at 2% or above severely inhibited cell growth and production of glycolipids. Our results suggest that U. maydis is an excellent host for the bioconversion of crude glycerol to value-added products. 相似文献
999.
Enzymatic catalysis has conflicting structural requirements of the enzyme. In order for the enzyme to form a Michaelis complex, the enzyme must be in an open conformation so that the substrate can get into its active center. On the other hand, in order to maximize the stabilization of the transition state of the enzymatic reaction, the enzyme must be in a closed conformation to maximize its interactions with the transition state. The conflicting structural requirements can be resolved by a flexible active center that can sample both open and closed conformational states. For a bisubstrate enzyme, the Michaelis complex consists of two substrates in addition to the enzyme. The enzyme must remain flexible upon the binding of the first substrate so that the second substrate can get into the active center. The active center is fully assembled and stabilized only when both substrates bind to the enzyme. However, the side-chain positions of the catalytic residues in the Michaelis complex are still not optimally aligned for the stabilization of the transition state, which lasts only approximately 10(-13) s. The instantaneous and optimal alignment of catalytic groups for the transition state stabilization requires a dynamic enzyme, not an enzyme which undergoes a large scale of movements but an enzyme which permits at least a small scale of adjustment of catalytic group positions. This review will summarize the structure, catalytic mechanism, and dynamic properties of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase and examine the role of protein conformational dynamics in the catalysis of a bisubstrate enzymatic reaction. 相似文献
1000.
Miao J Choi SE Seok SM Yang L Zuercher WJ Xu Y Willson TM Xu HE Kemper JK 《Molecular endocrinology (Baltimore, Md.)》2011,25(7):1159-1169