首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   376410篇
  免费   41486篇
  国内免费   274篇
  2018年   3700篇
  2017年   3541篇
  2016年   5128篇
  2015年   7282篇
  2014年   8349篇
  2013年   11696篇
  2012年   13364篇
  2011年   13340篇
  2010年   8809篇
  2009年   7723篇
  2008年   11534篇
  2007年   11953篇
  2006年   11231篇
  2005年   10822篇
  2004年   10797篇
  2003年   10358篇
  2002年   10268篇
  2001年   15591篇
  2000年   15618篇
  1999年   12600篇
  1998年   4587篇
  1997年   4613篇
  1996年   4388篇
  1995年   4222篇
  1994年   4232篇
  1993年   4069篇
  1992年   10528篇
  1991年   10056篇
  1990年   9868篇
  1989年   9570篇
  1988年   8894篇
  1987年   8506篇
  1986年   7713篇
  1985年   7810篇
  1984年   6489篇
  1983年   5689篇
  1982年   4559篇
  1981年   4070篇
  1980年   3801篇
  1979年   6541篇
  1978年   4903篇
  1977年   4584篇
  1976年   4230篇
  1975年   4640篇
  1974年   4975篇
  1973年   5016篇
  1972年   4672篇
  1971年   4350篇
  1970年   3653篇
  1969年   3565篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
We have used a preparation of rat liver plasma membranes to study the binding of rat apolipoprotein E-deficient HDL to rat liver. The membranes were found to bind HDL by a saturable process that was competed for by excess unlabeled HDL. The binding was temperature-dependent and was 85% receptor-mediated when incubated at 4, 22 and 37 degrees C. The affinity of the binding site for the HDL was consistent at all temperatures, while the maximum binding capacity increased at higher temperatures. The specific binding of HDL to the membranes did not require calcium and was independent of the concentration of NaCl in the media. The effect of varying the pH of the media on HDL binding was small, being 30% higher at pH 6.5 than at pH 9.0. Both rat HDL and human HDL3 were found to compete for the binding of rat HDL to the membranes, whereas rat VLDL remnants and human LDL did not compete. At 4 degrees C, complexes of dimyristoylphosphatidylcholine (DMPC) and apolipoproteins A-I, A-IV and the C apolipoproteins, but not apolipoprotein E, competed for HDL binding to the membranes. At 22 and 37 degrees C, all DMPC-apolipoprotein complexes competed to a similar extent, DMPC vesicles that contained no protein did not compete for the binding of HDL. These results suggest that the rat liver possesses a specific receptor for apolipoprotein E-deficient HDL that recognizes apolipoproteins A-I, A-IV and the C apolipoproteins as ligands.  相似文献   
952.
The paper presents the results of theoretical and experimental studies of the radiative properties of plasmas produced by heating and compression of various materials to high energy densities. The specific features of the theoretical plasma model known as the ion model, which is used to calculate the radiative characteristics of plasmas of complex chemical composition, are discussed. The theoretical approach based on this model is applied to the plasma produced during the explosion of the X-pinch wires. The theoretical estimate of the radiation efficiency is compared with the experimental data on the total energy yield from an X-pinch made of two different wires (NiCr and Alloy 188). The radiative characteristics of (C12 H16 O8) and (C8 H12 O6) plasmas are calculated for the temperature diagnostics of plasmas produced from porous targets employed in inertial confinement fusion experiments with the use of laser radiation and heavy-ion beams.  相似文献   
953.
954.
955.
956.
957.
The work shows that fibronectin obtained from human plasma is capable of binding with streptococci of different groups with almost equal effectiveness. Fibronectin bound to bacterial cells inhibits the adhesion of group A streptococci onto vaginal cells, but it produces no effect on the adhesion of group B streptococci. The binding constant of fibronectin 125I is equal to 10(6) -M-1, which indicates that the level of the specificity of interaction is not sufficiently high.  相似文献   
958.
Summary. Blood samples from a female sheep-goat hybrid and its back-cross male offspring were tested for electrophoretic variants of plasma albumin, transferrin and esterase, and of red cell carbonic anhydrase, nucleoside phosphorylase, NADH-diaphorase, 'X'-protein, superoxide dismutase, malic enzyme and haemoglobin. Red cells were also tested for blood group antigens. Both animals showed variants that could not be attributed to either sheep or goat alone, thus confirming previous chromosomal data that the female was a genuine sheep-goat hybrid.  相似文献   
959.
The compound p-mercuribenzenefulfonate was found to affect the self-association behavior of both spectrin and actin. The reagent brings about the depolymerization of F-actin, as judged from the decrease in the fluorescence of an attached pyrene label, with a second-order rate constant an order of magnitude less than that for the disruption of isolated erythrocyte cytoskeletons. Therefore, it is unlikely that the depolymerization of actin is the rate-determining step in the mercurial-dependent disruption of the erythrocyte cytoskeleton. Low reagent concentrations caused an initial rapid dissociation of spectrin tetramers at a rate comparable with that of cytoskeleton disruption. Prolonged incubation, or higher reagent concentrations, resulted in subsequent aggregation of spectrin. The reagent also prevented the interaction between spectrin and actin, presumably through its depolymerization of actin and its effects on spectrin. The early event in the disruption of isolated erythrocyte cytoskeletons by p-mercuribenzenesulfonate thus appears to be the dissociation of spectrin oligomers. Subsequent depolymerization of actin brought about by the reagent then results in total disruption of the cytoskeleton.  相似文献   
960.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号