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   333696篇
  免费   37263篇
  国内免费   190篇
  371149篇
  2018年   2855篇
  2017年   2714篇
  2016年   3900篇
  2015年   5378篇
  2014年   6290篇
  2013年   8810篇
  2012年   10075篇
  2011年   10041篇
  2010年   6844篇
  2009年   6182篇
  2008年   8908篇
  2007年   9349篇
  2006年   8633篇
  2005年   8322篇
  2004年   8026篇
  2003年   7793篇
  2002年   7785篇
  2001年   18149篇
  2000年   18375篇
  1999年   14109篇
  1998年   4236篇
  1997年   4501篇
  1996年   4304篇
  1995年   4007篇
  1994年   3945篇
  1993年   3783篇
  1992年   11490篇
  1991年   11125篇
  1990年   10680篇
  1989年   10245篇
  1988年   9493篇
  1987年   8844篇
  1986年   8078篇
  1985年   7962篇
  1984年   6395篇
  1983年   5564篇
  1982年   4106篇
  1981年   3593篇
  1980年   3355篇
  1979年   6114篇
  1978年   4571篇
  1977年   4125篇
  1976年   3760篇
  1975年   4331篇
  1974年   4497篇
  1973年   4390篇
  1972年   4092篇
  1971年   3503篇
  1970年   3170篇
  1969年   2970篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
973.
974.
975.
Restriction fragment length polymorphisms (RFLPs) were described for the porcine loci for β-glucosidase (GBA) and the β-polypeptide 1 of the Na+, K+-transporting ATPase (ATP1B1). Linkage analyses using a three-generation pedigree provided evidence for the assignment of ATP1B1, GBA and two microsatellite loci (S0001 and S0067) to a previously described linkage group comprising the loci for blood group L (EAL) and an anonymous microsatellite (S0097). The linear order of the six markers was determined with confidence by multipoint analyses and the length of the linkage group was estimated at 88 CM. This linkage group was assigned to pig chromosome 4 on the basis of a previous physical localization of the ATP1B1 gene. In situ hybridization data for S0001 presented in this study were consistent with a localization on chromosome 4 and suggested a regional localization to 4pl2-pl3. The present study reveals conflicting data concerning the genetic localization of the K88 loci controlling the expression of the receptors for the E. coli pilus antigens. One group has reported data suggesting a loose linkage between K88 and EAL, now mapped to chromosome 4, whereas two other groups have found linkage between K88 and the transferrin locus (TF), mapped to chromosome 13 by in situ hybridization.  相似文献   
976.
Abstract Monoclonal antibodies have been developed and used as specific probe to locate and identify a 29-kDa molecule of axenic Entamoeba histolytica trophozoites. Monoclonal antibody produced by clone C8 (MoAb C8) strongly agglutinated the amoebic trophozoites. THe immunofluorescence of live E. histolytica trophozoites and surface fluorescence of acetone-fixed trophozoites by MoAb C8 indicated existence of a 29-kDa molecule on surface-associated plasma membrane of E. histolytica . The monoclonal antibody belonged to IgG1 isotype. The prior treatment of E. histolytica trophozoites with MoAb C8 resulted in significant ( P < 0.01) reduction in adherence of amoebic trophozoites to cultured Chinese Hamster Ovary cells and significant ( P < 0.01) reduction in cytotoxicity to cultured Baby Hamster Kidney cells. Pretreatment of amoebic trophozoites with MoAb C8 prior to cultivation in TPS-1 medium resulted in significant ( P < 0.01) reduction in growth of the parasite. Thus, the data suggested that the surface-exposed 29-kDa molecule may be one of the receptors involved in E. histolytica host cell interactions and may possibly modulate amoebic disease processes.  相似文献   
977.
Based on quantitative measurement of components of field resistance of potatoes to late blight, a multiple linear regression equation is derived for laboratory estimation of Area Under Disease Progress Curve. The equation accounts for 82% of variation in Area Under Disease Progress Curve. Transformation of data or inclusion of more terms do not improve the equation significantly. The method is suggested as a replacement or supplement to field testing.  相似文献   
978.
In vitro incubation of thymocytes with [2-14C]acetate results in a more intensive label incorporation into chromatin lipids as compared to nuclear lipids. The deleterious effect of gamma-irradiation leads to specific changes in [2-14C]acetate incorporation into the total fraction of phosphatidylcholine-phosphatidylserine and chromatin sphingomyelin. This is paralleled with an increase in the ratio of specific radioactivities of chromatin cardiolipin and nuclear cardiolipin. The changes in specific radioactivities of sphingomyelin, phosphatidylcholine-phosphatidylserine and cardiolipin suggest a role of phospholipids in the mechanisms of regulating the activity of intranuclear structures.  相似文献   
979.
Custom prefabrication of free flaps provides an unlimited variety of applications, since flaps can be created with expendable tissues and without restriction to naturally occurring vascular territories. These principles also can be used to customize flaps that could not be completed by conventional means. We report a case of scalp reconstruction using a random-pattern abdominal flap in which a radial artery fascial flap was induced to serve as the vascular carrier. In addition to providing durable scalp coverage, the prefabricated free flap enabled salvage of an abdominal flap that would otherwise have been aborted after intermediate transfer to the forearm.  相似文献   
980.
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