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Using polyclonal and monoclonal antibodies to visualize under a confocal microscope type-1 cannabinoid receptors (CB1) and acetylcholine (ACh) receptors, respectively, or α-bungarotoxin conjugated to Alexa-Fluor 555 for Ach receptors, we found that they colocalize on twitch muscle fibers in the frog (Rana pipiens). We show that both the CB1 and ACh receptors are present on the fast skeletal muscle motor end-plate. The CB1 receptor is present along the entire membrane of the muscle fiber, whereas the ACh receptor is expressed primarily at the motor end-plate. Analysis of the colocalization produced a cross-correlation coefficient of 0.519 ± 0.021 (n = 9) for both receptors at the muscle motor end-plate. This study suggests a close proximity between these two types of receptor proteins and that they could interact. CB1 could function at some stage of excitation–contraction coupling in these muscle fibers. However, further investigation is needed in order to clarify these issues.  相似文献   
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Cytoplasmic dynein play an important role in transporting various intracellular cargos by coupling their ATP hydrolysis cycle with their conformational changes. Recent experimental results showed that the cytoplasmic dynein had a highly variable stepping pattern including “hand-over-hand”, “inchworm” and “nonalternating-inchworm”. Here, we developed a model to describe the coordinated stepping patterns of cytoplasmic dynein, based on its working cycle, construction and the interaction between its leading head and tailing head. The kinetic model showed how change in the distance between the two heads influences the rate of cytoplasmic dynein under different stepping patterns. Numerical simulations of the distribution of step size and striding rate are in good quantitative agreement with experimental observations. Hence, our coordinated stepping model for cytoplasmic dynein successfully explained its diverse stepping patterns as a molecular motor. The cooperative mechanism carried out by the two heads of cytoplasmic dynein shed light on the strategies adopted by the cytoplasmic dynein in executing various functions.  相似文献   
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【目的】比较敲除meq基因的马立克氏病毒(MDV)与标准疫苗株CVI988/Rispens对MDV超强毒GX0101攻毒的免疫保护作用。【方法】本实验将1日龄SPF鸡120只随机分成4组,每组30只,分别饲养在正压过滤空气的SPF动物饲养隔离罩内。1日龄时,第1组鸡以2000PFU/只的剂量颈部皮下接种SC9-1;第2组鸡以2000PFU/只的剂量颈部皮下接种CVI988/Rispens;第3、4组为不免疫攻毒对照组。免疫接种后5 d后,第1、2、3组分别以2000PFU/只的剂量腹腔接种MDV GX0101。饲养至90日龄,记录死亡情况,对死亡鸡只剖检,并取疑似马立克特有病变脏器做病理切片。期间,检测不同免疫状态下病毒GX0101的增殖动态以及禽流感、新城疫灭活苗在鸡体诱导产生抗体的水平。对含有MDV母源抗体的海蓝褐鸡的试验方案与SPF鸡一致。【结果】SC9-1株免疫对感染MDV GX0101攻击SPF鸡、海兰褐鸡均提供100%的免疫保护作用;CVI988/Rispens对SPF鸡、海兰褐鸡分别提供86.7%、93%的免疫保护作用。未免疫SPF鸡攻毒组死亡率为53.3%,肿瘤率为16.7%;未免疫海兰褐鸡攻毒组死亡率为36.7%,肿瘤率为6.67%;相比,空白对照组鸡只没有任何病变及死亡。荧光定量结果显示,淋巴细胞和羽毛囊DNA中,SC9-1免疫组鸡体内GX0101的病毒拷贝数显著低于CVI988/Rispens免疫组。血凝抑制试验结果显示,SC9-1免疫攻毒组鸡的产生的AIV、NDV抗体水平高于CVI988/Rispens免疫攻毒组。【结论】SC9-1株免疫无论在SPF鸡还是含有MDV母源抗体的海兰褐鸡均能提供比CVI988/Rispens更好的免疫保护效果。  相似文献   
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A temperature sensor based on hollow fiber (HF) filled with graphene-Ag composite nanowire and liquid is presented. The coupling properties and sensing performance are numerically analyzed by finite element method using wavelength and amplitude interrogations. Results show that the sensor exhibiting strong birefringence with x-polarized peak provides much higher sensitivities and better signal-to-noise ratio (SNR) than y-polarized, which is more suitable for temperature detection. The graphene-Ag composite nanowire can not only solve the oxidation problem but also avoid the metal coating. Moreover, it provides better performance than other similar works like Au-Ag nanowire-filled, Au nanowire-filled, and Ag nanowire-filled sensors. Contrary to the blue shift of traditional SPR temperature sensors, the resonance peak shifts to the longer wavelength in our device when temperature increases and the high sensitivity 9.44 nm/ °C is obtained. The influences of nanowire diameter, grapheme-layer thickness on the designed sensor, are also investigated. This work can provide a reference for developing a high sensitivity, real-time, remote sensing, and distributed temperature SPR sensor.  相似文献   
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The effects of drought on plant growth and development are occurring as a result of climate change and the growing scarcity of water resources. Hippophae rhamnoides has been exploited for soil and water conservation for many years. However, the outstanding drought‐resistance mechanisms possessed by this species remain unclear. The protein, physiological, and biochemical responses to medium and severe drought stresses in H. rhamnoides seedlings are analyzed. Linear decreases in photosynthesis rate, transpiration rate, and the content of indole acetic acid in roots, as well as a linear increase in the contents of abscisic acid, superoxide dismutase, glutathione reductase, and zeatin riboside in leaves are observed as water potential decreased. At the same time, cell membrane permeability, malondialdehyde, stomatal conductance, water use efficiency, and contents of zeatin riboside in roots and indole acetic acid in leaves showed nonconsistent changes. DIGE and MS/MS analysis identified 51 differently expressed protein spots in leaves with functions related to epigenetic modification and PTM in addition to normal metabolism, photosynthesis, signal transduction, antioxidative systems, and responses to stimuli. This study provides new insights into the responses and adaptations in this drought‐resistant species and may benefit future agricultural production.  相似文献   
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Growth hormone is a positive regulator of mammary gland development. Dairy animals that are administered growth hormone display enhanced lactation performance, a desirable agricultural trait. The objective of the current research was to generate an improved milk production phenotype in a large animal model using over-expressed GH in the mammary gland to promote mammogenesis. To this end, we constructed a mammary gland-specific expression vector, pcGH, and demonstrated effective GH expression in goat mammary epithelial cells in vitro by ELISA. Then, to produce transgenic offspring that were capable of stable GH expression in vivo, the linearized pcGH vector was electroporated into goat fetal fibroblasts. Cell colonies that were positive for GH were used as donors for nuclear transfer to enucleated oocytes. A total of 253 morulae or blastocytes developed from the reconstructed embryos were transferred to 56 recipients, resulting in 24 pregnancies at day 35. Finally, six transgenic goats were born. PCR detection confirmed the success of the cloning procedure. To observe the mammogenesis of dairy goats, the GH transgenic goats were mated with a completely healthy buck. In the later pregnancy period, the mammary gland of the GH transgenic goats were extensive than non-transgenic goats. These experiments indicated that the pcGH vector was incorporated into the transgenic goats and affected mammogenesis, which laid a solid foundation for elucidating the impact of GH on mammogenesis and lactation performance.  相似文献   
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Functional screening of a metagenomic library constructed with DNA extracted from the rumen contents of a grass/hay-fed dairy cow identified a protein, β-glucosidase/β-xylosidase/α-arabinosidase gene (Bgxa1), with high levels of β-glucosidase activity. Purified Bgxa1 was highly active against p-nitrophenyl-β-d-glucopyranoside (pNPG), cellobiose, p-nitrophenyl-β-d-xylopyranoside (pNPX) and p-nitrophenyl-α-d-arabinofuranoside (pNPAf), suggesting it is a multifunctional β-glucosidase/β-xylosidase/α-arabinosidase. Kinetic analysis of the protein indicated that Bgxa1 has the greatest catalytic activity against pNPG followed by pNPAf and pNPX, respectively. The catalytic efficiency of β-glucosidase activity was 100× greater than β-xylosidase or α-arabinosidase. The pH and temperature optima for the hydrolysis of selected substrates also differed considerably with optima of pH 6.0/45 °C and pH 8.5/40 °C for pNPG and pNPX, respectively. The pH dependence of pNPAf hydrolysis displayed a bimodal distribution with maxima at both pH 6.5 and pH 8.5. The enzyme exhibited substrate-dependent responses to changes in ionic strength. Bgxa1 was highly stable over a broad pH range retaining at least 70 % of its relative catalytic activity from pH 5.0–10.0 with pNPG as a substrate. Homology modelling was employed to probe the structural basis of the unique specificity of Bgxa1 and revealed the deletion of the PA14 domain and insertions in loops adjacent to the active site. This domain has been found to be an important determinant in the substrate specificity of proteins related to Bgxa1. It is postulated that these indels are, in part, responsible for the multifunctional activity of Bgxa1. Bgxa1 acted synergistically with endoxylanase (Xyn10N18) when incubated with birchwood xylan, increasing the release of reducing sugars by 168 % as compared to Xyn10N18 alone. Examination of Bgxa1 and Xyn10N18 synergy with a cellulase for the saccharification of alkali-treated straw revealed that synergism among the three enzymes enhanced sugar release by 180 % as compared to cellulase alone. Our results suggest that Bgxa1 has a number of properties that make it an interesting candidate for the saccharification of lignocellulosic material.  相似文献   
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Listeria monocytogenes serotype 4b has frequently been implicated in sporadic as well as epidemic listeriosis. On the basis of pulsed-field fingerprinting, serotype 4b strains, along with strains of serotypes 4d and 4e, constitute one genomic cluster (IIB). We have identified two genomic regions essential for the expression of surface antigens which previously were shown to be specific to cluster IIB strains. A DNA probe of 1.1 kb derived from one of the regions (probe 1) hybridized only with strains of serotypes 4b, 4d, and 4e in Southern blots and dot blots. A different DNA probe of 0.3 kb (probe 2), derived from the other region, hybridized with all serovar 4 strains (serotypes 4b, 4a, 4c, 4d, and 4e). All other L. monocytogenes serotypes were negative with probe 1 or 2. Use of probe 1 in Southern blots of EcoRI-digested genomic DNA revealed a restriction fragment length polymorphism in serotype 4b strains, with the hybridizing EcoRI fragments being 4.5 kb (strains of the epidemic clone) and either 4.5 or 5.0 kb (all other serotype 4b strains). Although the probes hybridized with a special group of Listeria innocua strains which also expressed the surface antigens, the latter could be readily distinguished by the size of the hybridizing EcoRI fragment with probe 1 (ca. 2.2 kb). These data suggest that the combined use of these probes with L. monocytogenes can readily and specifically identify cluster IIB strains as well as the entire serovar 4 complex.  相似文献   
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