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141.
日本沼虾Macrobrachium nipponense(de Haan)卵子附着机制研究I.卵膜及卵子附着的扫描电镜观察 总被引:2,自引:0,他引:2
用扫描电镜技术观察了日本沼虾(Macrobrachiumnipponense)成熟卵、人工授精卵及自然受精产出附着于腹肢上的卵。成熟卵只有初级卵膜,表面较光滑,上密布微孔,密度约1~2个/μm2;人工授精卵表面首先突起大小不同的颗粒,随后颗粒破裂并消失,同自然受精卵一样,卵表略光滑,呈波浪状起伏,微孔密度与未受精前大致相同;自然产出的受精卵,表面覆盖一层由雌体腹肢分泌的次级卵膜。次级卵膜具有保护、选择性渗透及隔离邻近受精卵的作用。腹肢不断摆动,受精卵在腹肢间滚动并形成卵与卵之间以及卵与刚毛之间两种“卵柄”,一种称为卵索(funiculus),不与刚毛相连。funiculus扁带状,与卵接触处较宽,约140~150μm,中间宽约30~40μm;另一种称为卵柄(eggstalk),由1~2根载卵刚毛(oose-tae)插入次级卵膜形成,与卵接触处次级卵膜突起呈锥状,基部宽约140~150μm。非载卵刚毛起辅助抱卵作用。 相似文献
142.
茴香原生质体培养研究 总被引:1,自引:0,他引:1
以茴香(FoeniculumvulgareL.)幼苗茎切段在MS附近2,4-D1mg/L、6-BA0.5mg/L的培养基上诱导产生愈伤组织,经4~5次继代后形成胚性愈伤组织。将胚性愈伤组织转至MS+NAA1mg/L+2,4-D0.5mg/L+6-BA0.25mg/L的液体培养基中培养,形成胚性细胞悬浮系。悬浮细胞在含有1.5%纤维素酶、1%果胶酶、0.5%蜗牛酶的混合酶液中酶解得到大量的原生质体,原生质体用修改的KM8P培养基中做液体浅层培养。2天后细胞发生一裂,两个月后形成0.5~1mm大小的小愈伤组织,转入含琼脂糖的固体培养基中3周后形成2~3mm的愈伤组织 相似文献
143.
A method of preparing Mo_2C via vacuum carbothermic reduction of MoS_2 in the temperature range of 1350–1550°C was proposed. The effects of MoS_2-to-C molar ratio(a, a = 1:1, 1:1.5, and 1:2.5) and reaction temperature(1350 to 1550°C) on the reaction were studied in detail. The phase transition, morphological evolution, and residual sulfur content of the products were analyzed by X-ray diffraction, field-emission scanning electron microscopy, and carbon–sulfur analysis, respectively. The results showed that the complete decomposition of MoS_2 under vacuum is difficult, whereas activated carbon can react with MoS_2 under vacuum to generate Mo_2C. Meanwhile, higher temperatures and the addition of more carbon accelerated the rate of carbothermic reduction reaction and further decreased the residual sulfur content. From the experimental results, the optimum molar ratio α was concluded to be 1:1.5. 相似文献
144.
I-Jung Tsai Chia-Hung Chou Yao-Hsu Yang Wei-Chou Lin Yen-Hung Lin Lu-Ping Chow Hsiao-Hui Lee Pei-Gang Kao Wan-Ting Liau Tzuu-Shuh Jou Yong-Kwei Tsau 《Cellular and molecular life sciences : CMLS》2015,72(16):3157-3171
Childhood nephrotic syndrome is mainly caused by minimal change disease which is named because only subtle ultrastructural alteration could be observed at electron microscopic level in the pathological kidney. Glomerular podocytes are presumed to be the target cells whose protein sieving capability is compromised by a yet unidentified permeability perturbing factor. In a cohort of children with non-hereditary idiopathic nephrotic syndrome, we found the complement fragment C5a was elevated in their sera during active disease. Administration of recombinant C5a induced profound proteinuria and minimal change nephrotic syndrome in mice. Purified glomerular endothelial cells, instead of podocytes, were demonstrated to be responsible for the proteinuric effect elicited by C5a. Further studies depicted a signaling pathway involving Rho/Rho-associated kinase/myosin activation leading to endothelial cell contraction and cell adhesion complex breakdown. Significantly, application of Rho-associated kinase inhibitor, Y27632, prevented the protein leaking effects observed in both C5a-treated purified endothelial cells and mice. Taken together, our study identifies a previously unknown mechanism underlying nephrotic syndrome and provides a new insight toward identifying Rho-associated kinase inhibition as an alternative therapeutic option for nephrotic syndrome. 相似文献
145.
一个面向对象的工程数据库管理系统章国宝,周伯鑫,居荣(东南大学自动控制工程系,南京210018)1数据模型建立满足工程应用环境需求的数据模型是研制工程数据库管理系统的关键.面向对象的数据模型因其直观、语义丰富而成为工程数据库的首选模型[1,2].但是... 相似文献
146.
本文报道了阳离子交换树脂催化的邻苯二甲酸二丁酯的合成方法,比传统的酸催化酯化方法简便,无设备腐蚀现象。 相似文献
147.
Effects of specific surface area of metallic nickel particles on carbon deposition kinetics 下载免费PDF全文
Zhi-yuan Chen Liu-zhen Bian Zi-you Yu Li-jun Wang Fu-shen Li Kuo-Chih Chou 《矿物冶金与材料学报》2018,25(2):226-235
Carbon deposition on nickel powders in methane involves three stages in different reaction temperature ranges. Temperature programing oxidation test and Raman spectrum results indicated the formation of complex and ordered carbon structures at high deposition temperatures. The values of I(D)/I(G) of the deposited carbon reached 1.86, 1.30, and 1.22 in the first, second, and third stages, respectively. The structure of carbon in the second stage was similar to that in the third stage. Carbon deposited in the first stage rarely contained homogeneous pyrolytic deposit layers. A kinetic model was developed to analyze the carbon deposition behavior in the first stage. The rate-determining step of the first stage is supposed to be interfacial reaction. Based on the investigation of carbon deposition kinetics on nickel powders from different resources, carbon deposition rate is suggested to have a linear relation with the square of specific surface area of nickel particles. 相似文献
148.
循环流化床技术是国内外最新锅炉清洁燃烧技术。该项技术“中华人民共和国节约能源法”及国内配套法律法规中列为重点推广的技术之一。其突出优点是:能源使用效率高,锅炉效率可达80%以上,炉渣含炭量小于7%以下,低温燃烧炉内脱硫效果好和氮氧化合物排量少。炉渣是很好的建材原料,由于煤种适应性广,可使用劣质燃料,运行成本大大降低,企业可获得显著经济效益。 相似文献
149.
Chun-ming Lin Hsien-lung Tsai Chang-lin Lee Di-shiang Chou Sun-fen Lee Jen-ching Huang Jyun-wei Huang 《矿物冶金与材料学报》2012,19(12):1114-1120
This study investigated the microstructural characteristics, metallurgy, microhardness, and tensile strength of AZ31 and AZ61 magnesium alloy weldments, fabricated in a CO2 laser welding process with the adjustment of various parameters. The results show that the AZ31 weldment contains equiaxed grains within the fusion zone (FZ). By contrast, the FZ of the AZ61 weldment contains refined cellular grains and the partially melted zone (PMZ) contains bulk grains. We infer that the difference in aluminum content between the two magnesium alloys results in different supercooling rates and solid grain structures. For both weldments, the ultimate tensile strength (UTS) decreases following the CO2 laser welding process. However, no significant difference is noted between the UTS of the two weldments, suggesting that tensile strength is insensitive to the Al content of the magnesium alloy. The CO2 laser welding process is shown to increase the microhardness of both magnesium alloys. Furthermore, grain refinement is responsible for the maximum hardness in the FZ of both weldments. The AZ61 weldment has a higher content of Al, resulting in a greater grain refinement. 相似文献
150.
纳米TiN粉改性Ti(C,N)基金属陶瓷的制备工艺 总被引:1,自引:0,他引:1
在基体中添加纳米TiN粉(质量分数为0.05)的条件下,用三点弯曲法和扫描电镜等研究了粉末单向冷模压压制工艺和烧结技术对Ti(C,N)基金属陶瓷的力学性能和微观组织的影响.实验结果表明:烧结坯的抗弯强度先随生坯的压制压力(≤150 MPa)增加而增加,随后(210 MPa~600 MPa)增加缓慢,最后(≥600MPa)下降;烧结坯的变形率则随生坯的压制压力(≥300 MPa)增加而增大;最佳生坯的压制压力范围是150MPa~210 MPa.实验结果表明:两阶段烧结法优于传统烧结法,烧结坯的微观组织均匀,抗弯强度增加. 相似文献