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   582篇
  免费   32篇
  国内免费   114篇
耳鼻咽喉   3篇
儿科学   28篇
妇产科学   3篇
基础医学   45篇
口腔科学   10篇
临床医学   139篇
内科学   144篇
皮肤病学   23篇
神经病学   7篇
特种医学   96篇
外科学   32篇
综合类   48篇
预防医学   30篇
眼科学   15篇
药学   79篇
中国医学   4篇
肿瘤学   22篇
  2021年   2篇
  2020年   6篇
  2019年   6篇
  2018年   9篇
  2017年   7篇
  2016年   5篇
  2015年   18篇
  2014年   16篇
  2013年   41篇
  2012年   17篇
  2011年   20篇
  2010年   26篇
  2009年   36篇
  2008年   9篇
  2007年   74篇
  2006年   30篇
  2005年   18篇
  2004年   8篇
  2003年   5篇
  2002年   9篇
  2001年   11篇
  2000年   9篇
  1999年   12篇
  1998年   38篇
  1997年   31篇
  1996年   30篇
  1995年   24篇
  1994年   25篇
  1993年   18篇
  1992年   9篇
  1991年   10篇
  1990年   14篇
  1989年   18篇
  1988年   24篇
  1987年   11篇
  1986年   3篇
  1985年   8篇
  1984年   3篇
  1983年   3篇
  1982年   5篇
  1981年   7篇
  1980年   8篇
  1978年   3篇
  1977年   4篇
  1976年   5篇
  1975年   5篇
  1958年   14篇
  1955年   4篇
  1951年   1篇
  1945年   1篇
排序方式: 共有728条查询结果,搜索用时 15 毫秒
131.
据文献记载和作者的调查,我国产麻黄属(Ephedra)植物共有13种3变种1变型。本文报道我国北方生产的7种麻黄生药形态组织学比较研究结果。7种麻黄是:草麻黄Ephedra sinica Stapf、木贼麻黄E.equisetina Bunge、中麻黄E.intermedia Schrenk ex Mey.、膜果麻黄E.przewalskii Stapf,单子麻黄E.monosperma Gmel.ex Mey.、雌雄麻黄E.fedtschenkoae Pauls和细子麻黄E.reaeliana Florin。文中附有生药性状与组织构造特征比较表及生药组织图  相似文献   
132.
Moderate and severe reactions in blood donors   总被引:2,自引:0,他引:2  
During the period April 1985 to March 1986, 217 blood donors were found to have moderate (syncopal) to severe (convulsive) reactions. This population was compared to 5630 randomly selected donors who did not have reactions. An examination of demographic, physical, and societal/emotional factors was conducted to determine if any were predictive of reactions in donors. The results of the research supported the hypothesis that first-time donors have a higher frequency of reactions (1.7%) than do repeat donors (0.19%). A review of the above predictive factors documented that, with regard to demographic factors, 1) the number of prior donations was inversely proportional to the risk of reaction; 2) the gender of the donor was not predictive; and 3) youth was a predictor of reactions. An analysis of the physical factors revealed that donors who reacted were of lower weight (mean, 153.7 lb) than those who did not (mean, 166.4 lb) and that systolic blood pressure was slightly lower in the group with reactions. Although the difference was significant (3 torr), it was not thought to be significant clinically. In a comparison of a group with systolic blood pressure ranging from 80 to 100 torr and a group with systolic blood pressure ranging from 120 to 140 torr, the first group had a 70-percent higher risk of reaction. Finally, with regard to the last category of societal or emotional factors, the research demonstrates 1) that the ingestion of caffeinated beverages was associated with a reduced risk of reactions; 2) that the food intake of donors who reacred was significantly different from that of those who had no reaction, but this difference was not thought to be clinically significant; and 3) that the duration between registration and the onset of phlebotomy was directly predictive of reaction status. The research indicates that first-time donor status and several specific demographic, physical, and societal or emotional factors are predictors of donor reactions.  相似文献   
133.
To investigate the influence of asymptomatic bacteriuria inchildhood on subsequent pregnancy, we reviewed the outcome of139 pregnancies in 88 women who were first identified duringa programme of screening schoolgirls for asymptomatic bacteriuriacarried out between 1970–1972 [1]. Data were analysedfor the following groups: 50 pregnancies in 28 women with knownrenal scars (group 1); 16 pregnancies in 14 women with normalkidneys and reflux (group 2); 73 pregnancies in 46 women withnormal urinary tracts (group 3); 139 healthy controls. Women in group 1 had a 3.3-fold increased relative risk of hypertension(p < 0.01) and a 7.6-fold increased risk of pre-eclampsia(p< 0.05) compared to controls, and a higher rate of obstetricinterventions, including emergency caesarean section. Womenin groups 2 and 3 appeared to carry a slightly increased riskof hypertension during the last trimester (RR = 1.8) but therewere no significant differences in this or the incidence ofpre-eclampsia or mode of delivery. Bacteriuria was more prevalentin all index groups compared to controls (37 per cent vs. 8per cent, p < 0.01) and included four cases of acute pyelonephritisin the study group. Fetal outcome was satisfactory in all cases.These results suggest that women with renal scars are at riskof hypertension and pre-eclampsia during pregnancy but thatmodern obstetric care minimizes these risks.  相似文献   
134.
苦楝化学成份的研究   总被引:7,自引:0,他引:7  
从苦楝(Melia azedarach L.)果中分得苦楝新醇(Ⅰ),苦楝醇(Ⅱ)、苦楝酮(Ⅲ)、苦楝二醇(Ⅳ)、香草醛(Ⅴ)和香草酸(Ⅵ)。根据波谱(IR,MS,1HNMR,13CNMR)分析和理化常数测定,确定了它们的结构。其中苦楝新醇(Ⅰ)为新化合物,对菜青小虫有一定的拒食活性。  相似文献   
135.
从苦楝(Melia azedarach L.)果中分得苦楝新醇(Ⅰ),苦楝醇(Ⅱ)、苦楝酮(Ⅲ)、苦楝二醇(Ⅳ)、香草醛(Ⅴ)和香草酸(Ⅵ)。根据波谱(IR,MS,~1HNMR,~(13)CNMR)分析和理化常数测定,确定了它们的结构。其中苦楝新醇(Ⅰ)为新化合物,对菜青小虫有一定的拒食活性。  相似文献   
136.
本文报道我国西南产麻黄——丽江麻黄Ephedra likiangensis Florin、匍枝丽江麻黄E.likiangensis f.mairei(Florin)C.Y.Cheng、藏麻黄E.saxatilis Royle ex Florin、山岭麻黄E.gerardiana Wall、垫状山岭麻黄E.gerardiana Var.congesta C.Y.Cheng、矮麻黄E.minuta Florin和异株矮麻黄E.minuta var.dioeca C.Y.Cheng,以及形态组织特征较特殊的宁夏产斑子麻黄E.lepidosperma C.Y.Cheng、新疆产窄膜麻黄E.lomatolepis Schrenk,西藏产西藏中麻黄E.intermedia var.tibetica Stapf的生药形态组织学研究结果。并根据对国产麻黄的生药形态组织学的系统研究结果,分别编写了各种国产麻黄(包括13种3变种1变型)的生药性状和生药显微特征检索表。  相似文献   
137.
Insulin receptors on leukemia and lymphoma cells   总被引:1,自引:0,他引:1  
Chen  PM; Kwan  SH; Hwang  TS; Chiang  BN; Chou  CK 《Blood》1983,62(2):251-255
Tumor cells obtained from leukemia and lymphoma patients were investigated for specific insulin receptors. Using radioactive 125I- labeled insulin, specific insulin binding sites were demonstrated on most acute lymphocytic leukemia (ALL) and acute myelocytic leukemia (AML) cells, including acute promyelocytic leukemia (APL), chronic myelocytic leukemia (CML), and acute monocytic leukemia (AMoL) cells. Insulin receptors were not found on chronic lymphocytic leukemia (CLL) and malignant lymphoma (ML) cells. Specific insulin binding sites were also found on monocytes and thymocytes after treatment with phytohemagglutinin (PHA-P), but not on inactivated tonsil cells, peripheral blood lymphocytes, or thymocytes. There was no inverse correlation between the content of insulin receptors and the basal level of circulating insulin. These data suggest that the insulin receptor may be a new marker of acute leukemia and chronic myelocytic leukemia.  相似文献   
138.
Ancylostoma tubaeforme was originally described as a separate species parasitizing the cat. The adults of A. tubaeforme are 7 to 12 mm long. A. tubaeforme can be differentiated from the adults of A. braziliense and A. ceylanicum by the presence of three teeth. Here we describe the first report of A. tubaeforme in a Persian young female leopard, 2–3 years old, with head and trunk length 120 centimeters, length of tail 98 centimeters and body weight 35 kilograms.  相似文献   
139.
140.
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