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   2861篇
  免费   64篇
耳鼻咽喉   3篇
儿科学   12篇
妇产科学   1931篇
基础医学   41篇
口腔科学   35篇
临床医学   195篇
内科学   199篇
皮肤病学   4篇
神经病学   38篇
特种医学   28篇
外科学   241篇
综合类   4篇
预防医学   140篇
眼科学   4篇
药学   18篇
中国医学   2篇
肿瘤学   30篇
  2013年   27篇
  2012年   20篇
  2011年   31篇
  2010年   19篇
  2009年   34篇
  2008年   22篇
  2007年   24篇
  2006年   19篇
  2004年   21篇
  2003年   19篇
  2002年   20篇
  2001年   31篇
  2000年   44篇
  1999年   162篇
  1998年   146篇
  1997年   164篇
  1996年   171篇
  1995年   120篇
  1994年   161篇
  1993年   96篇
  1992年   100篇
  1991年   118篇
  1990年   52篇
  1989年   96篇
  1988年   80篇
  1987年   64篇
  1986年   79篇
  1985年   92篇
  1984年   68篇
  1983年   66篇
  1982年   69篇
  1981年   72篇
  1980年   49篇
  1979年   42篇
  1978年   28篇
  1977年   39篇
  1976年   43篇
  1975年   38篇
  1974年   34篇
  1973年   43篇
  1972年   30篇
  1971年   26篇
  1970年   43篇
  1969年   36篇
  1967年   13篇
  1966年   11篇
  1964年   10篇
  1961年   16篇
  1960年   19篇
  1958年   10篇
排序方式: 共有2925条查询结果,搜索用时 15 毫秒
61.
To determine if acute stress activates pancreatic noradrenergic nerves, pancreatic norepinephrine (NE) output (spillover) was measured in halothane-anesthetized dogs. Central neuroglucopenia, induced by intravenous 2-deoxy-D-glucose [( 2-DG] 600 mg/kg + 13.5 mg/kg-1 per min-1) increased pancreatic NE output from a baseline of 380 +/- 100 to 1,490 +/- 340 pg/min (delta = +1,110 +/- 290 pg/min, P less than 0.01). Surgical denervation of the pancreas reduced this response by 90% (delta = +120 +/- 50 pg/min, P less than 0.01 vs. intact innervation), suggesting that 2-DG activated pancreatic nerves by increasing the central sympathetic outflow to the pancreas rather than by acting directly on nerves within the pancreas itself. These experiments provide the first direct evidence of stress-induced activation of pancreatic noradrenergic nerves in vivo. In contrast, neither hemorrhagic hypotension (50 mmHg) nor hypoxia (6-8% O2) increased pancreatic NE output (delta = +80 +/- 110 and -20 +/- 60 pg/min, respectively, P less than 0.01 vs. neuroglucopenia) despite both producing increases of arterial plasma NE and epinephrine similar to glucopenia. The activation of pancreatic noradrenergic nerves is thus stress specific. Furthermore, because both glucopenia and hypotension increased arterial NE, yet only glucopenia activated pancreatic nerves, it is suggested that a regionally selective pattern of sympathetic activation can be elicited by acute stress, a condition in which sympathetic activation has traditionally been thought to be generalized and nondiscrete.  相似文献   
62.
The regulation of mevalonic acid synthesis requires both nonsterol isopentenoid and sterol regulatory signal molecules. A primary target of this multivalent control process is the enzyme which catalyzes mevalonate synthesis: 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (EC 1.1.1.34). In this report Staphylococcus aureus alpha-toxin perforated Chinese hamster ovary cells were used to facilitate the identification of isopentenoidogenic reactions and metabolites required for mevalonate-mediated loss of HMG-CoA reductase activity. alpha-Toxin-perforated cells retained the capacity to decrease, upon demand, HMG-CoA reductase activity and protein in response to mevalonate or isopentenoid pyrophosphate esters. Also, it was deduced with highly specific metabolic inhibitors, that conversion of farnesyl 1-diphosphate to squalene was required for mevalonate-mediated suppression of reductase activity. Since squalene (2 microM) did not downregulate reductase activity, pre-squalene pyrophosphate or a derivative, or polyprenyl-1-pyrophosphate-generated inorganic pyrophosphate, or a combination of these metabolites are proposed as candidate regulatory nonsterol isopentenoid signal molecules.  相似文献   
63.
Very low density lipoproteins from guinea pig plasma, endogenously labeled with 3H in both the esterified and free cholesterol moieties, were obtained from serum collected 20 hr after the intravenous injection of 3H-cholesterol into donor animals. When these lipoproteins were injected into recipient guinea pigs, the esterified 3H-cholesterol was rapidly cleared from the plasma; 24% was in the liver in 5 min and 54% in 15 min. A smaller fraction of the esterified cholesterol appeared in other plasma lipoprotein fractions, with 3H in the low density lipoproteins reaching a peak of 9%-18% of the injected esterified 3H-cholesterol between 30 and 60 min after the injection. The results indicate that most of the esterified cholesterol in very low density lipoproteins of guinea pig plasma is removed directly by the liver and a minor fraction is transferred to low density lipoproteins. The pattern of labeling of cholesteryl esters of high density lipoproteins in these experiments suggests that their low concentration in the guinea pig is accompanied by a rapid turnover rate.  相似文献   
64.
To study the hemostyptic effect of aprotinin (Trasylol) in patients undergoing extracorporeal circulation for coronary artery bypass operations, we randomized 12 of 24 patients to receive aprotinin in high dosage (about 800 mg) during extracorporeal circulation. From the resulting two groups each, one patient was excluded from the study because of postoperative myocardial infarction (control group) and surgical hemorrhage (aprotinin group) leading to a second operation. Although heparin was used for anticoagulation in all 22 patients, all had a marked increase in plasma levels of thrombin-antithrombin III complexes during extracorporeal circulation, indicating an intravasal activation of coagulation. By monitoring the plasma levels of fibrin degradation products in patients without aprotinin therapy, we recorded a concomitant hyperfibrinolysis significantly less pronounced in patients receiving aprotinin (p less than 0.005). The mean total postoperative blood loss was lower in patients receiving aprotinin (620 ml) than in control patients (1000 ml; p less than 0.03). The results confirm previous reports of a hemostyptic effect of aprotinin in cardiac operations. This effect is probably due to a prevention of hyperfibrinolysis.  相似文献   
65.
66.
67.
Summary. Slow-release nifedipine has been used in the treatment of severe hypertension in 23 pregnant women. In 22 this was in combination with other drugs, in 18 including atenolol. Good control of blood pressure was achieved in 20 women. The perinatal mortality of the group was 130/1000, with a high caesarean section rate (71% of live-births), a high rate of abnormal CTGs, a high rate of premature delivery, and a high rate of infants who were small-for-dates. Whether this is due to the disease process or the medication is uncertain. For the present time these combinations should only be used in severe hypertensives or in the context of a controlled trial.  相似文献   
68.
    
Zusammenfassung Zur Prüfung der Wertigkeit von Akutphasenproteinen und Komplementfaktoren in der Frühdiagnose der intraabdominalen Infektion, wurden bei 60 Patienten nach abdominalchirurgischen Eingriffen die Antiproteasen alpha-l-Antitrypsin, alpha-2-Macroglobin, Transferrin und Antithrombin III, sowie der Komplementfaktoren C3 und C4 postoperativ bestimmt. Patienten, die eine intraabdominelle Infektion entwickelten, hatten bereits am 2. postoperativen Tag signifikant erhöhte alpha-1-Antitrypsin Plasmakonzentrationen im Vergleich zu Patienten mit unkompliziertem postoperativen Verlauf. Mittels der linearen Diskriminanzanalyse war es bereits am 2. postoperativen Tag möglich, eine kommende intraabdominele Infektion in 84% der Fälle richtig vorauszusagen.  相似文献   
69.
70.
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