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   5168篇
  免费   520篇
  国内免费   88篇
耳鼻咽喉   33篇
儿科学   161篇
妇产科学   79篇
基础医学   743篇
口腔科学   88篇
临床医学   773篇
内科学   1040篇
皮肤病学   55篇
神经病学   262篇
特种医学   396篇
外科学   655篇
综合类   114篇
一般理论   1篇
预防医学   493篇
眼科学   45篇
药学   324篇
肿瘤学   514篇
  2021年   78篇
  2019年   78篇
  2018年   59篇
  2017年   73篇
  2016年   91篇
  2015年   89篇
  2014年   113篇
  2013年   145篇
  2012年   200篇
  2011年   205篇
  2010年   157篇
  2009年   157篇
  2008年   170篇
  2007年   215篇
  2006年   187篇
  2005年   198篇
  2004年   157篇
  2003年   138篇
  2002年   137篇
  2001年   136篇
  2000年   151篇
  1999年   135篇
  1998年   144篇
  1997年   121篇
  1996年   146篇
  1995年   128篇
  1994年   122篇
  1993年   94篇
  1992年   120篇
  1991年   106篇
  1990年   116篇
  1989年   120篇
  1988年   104篇
  1987年   93篇
  1986年   105篇
  1985年   119篇
  1984年   78篇
  1983年   61篇
  1982年   60篇
  1981年   45篇
  1980年   49篇
  1979年   42篇
  1978年   44篇
  1977年   64篇
  1976年   47篇
  1973年   43篇
  1972年   44篇
  1971年   48篇
  1970年   57篇
  1968年   43篇
排序方式: 共有5776条查询结果,搜索用时 15 毫秒
101.
Antagonist properties of d-LSD at 5-hydroxytryptamine2 receptors   总被引:1,自引:0,他引:1  
The hallucinogenic agent d-lysergic acid diethylamide (d-LSD) interacts with a number of serotonin (5-hydroxytryptamine [5-HT]) receptor subtypes in the central nervous system. It has been hypothesized that hallucinosis is produced by agonist activity at 5-HT2 receptors. There exist, however, numerous data from radioligand binding, cellular, smooth muscle, and behavioral studies that suggest that d-LSD is a potent 5-HT2 antagonist. These data are reviewed in this report. In addition, d-LSD displays agonist activity at 5-HT1A and 5-HT1C receptor subtypes, as determined in biochemical studies. At the present time, agonist interactions at 5-HT1C receptors, as opposed to 5-HT2 receptors, appears to be a more likely "common mechanism of action" of hallucinogenic agents.  相似文献   
102.
103.
Although reliable antibodies are available that distinguishhuman suppressor T (Ts) cells from CTL and other T cells, feware available for murine Ts cells. We have developed a mAb (984D4.6.5)that, in the presence of complement, depletes alloantigen-specificTs cells but not CTL. This antibody recognizes activated TTscells but not their precursors. In these studies, flow cytometricanalysis demonstrates that 984D4.6.5 reacts with several Tscell hybridomas, cloned Th cell lines and WEHI-3 (a myelomonocytictumor cell line). Reactivity was not detected with BW5147, Thcell hybridomas, cloned Th cells, CTL lines and hybridomas,B cell lines, thymocytes, splenocytes, bone marrow cells nora variety of tumor cells. Among 984D4.6.5 positive lines, expressionis heterogeneous and the number of cells expressing high levelsof the epitope is increased when the hybridomas are maintainedat a relatively high cell density. Neuriminidase and pronasedeplete the epitope recognized by mAb 984D4.6.5. Protein synthesisand glycosylation inhibitors also reduce expression of thisepitope. These observations suggest that the epitope recognizedby 984D4.6.5 is a carbohydrate linked to a polypeptide. Thisantibody was tested by ELISA for binding to a large panel ofcarbohydrates and glycollpids coupled to BSA. The only one thatbound 984D4.6.5 was LS tetrasaccharide c (NeuNAc2-6Galpß1-4GIcNAcß1-3GaIß1-4Glc),an O-linked carbohydrate. Comparative analysis shows that boththe sequence and the linkage of these sugars are essential tothe reactivity with the 984D4.6.5 antibody. This epitope isexpressed by a glycoprotein of-200 kDa, as shown by Westernblots. The identity of this glycoprotein remains to be determined,but indirect evidence suggests that it is not CD45.  相似文献   
104.
105.
106.
Pierce C 《Health data management》1995,3(8):65-6, 69-70
A growing number of the nation's 67 Blue Cross and Blue Shield plans, many of which are dominant health insurers in their markets, are attempting to expand their electronic health care transactions business. At least a dozen plans have created claims clearinghouses designed to handle claims and other electronic transactions destined for any payer.  相似文献   
107.
The purpose of this investigation was to study the efficacy of two dietary supplements on measures of body mass, body composition, and performance in 42 American football players. Group CM (n = 9) received creatine monohydrate, Group P (n = 11) received calcium pyruvate, Group COM (n = 11) received a combination of calcium pyruvate (60%) and creatine (40%), and Group PL received a placebo. Tests were performed before (T1) and after (T2) the 50 week supplementation period, during which the subjects continued their normal training schedules. Compared to P and PL, CM and COM showed significantly greater increases for body mass, lean body mass, 1 repetition maximum (RM) bench press, combined 1 RM squat and bench press, and static vertical jump (SVJ) power output. Peak rate of force development for SVJ was significantly greater for CM compared to P and PL. Creatine and the combination supplement enhanced training adaptations associated with body mass/composition, maximum strength, and SVJ; however, pyruvate supplementation alone was ineffective.  相似文献   
108.
We investigated predictors of change in plasma carotenoids from baseline to 3 y and examined plasma carotenoid concentrations at 1 and 3 y in response to a high vegetable diet. Participants were 56 women diagnosed with breast cancer and enrolled in a randomized feasibility study for a trial examining the effect of a diet high in vegetables and fruits on the risk of breast cancer recurrence. Independent t test analysis revealed that the intervention group had significantly higher vegetable and fruit servings and fiber at 12 mo and significantly higher vegetable servings at 36 mo compared with the control group (P < 0.05). Energy intake from fat was significantly lower in the intervention group at 12 and 36 mo. The intervention group had significantly higher consumption of beta-carotene, alpha-carotene, lutein and beta-cryptoxanthin at 12 mo (P < 0.05). beta-Carotene, alpha-carotene and lutein intakes also were significantly higher at 36 mo (P < 0.05). At 36 mo, the intervention group had significantly higher plasma concentrations of alpha-carotene and beta-carotene compared with the control group. Repeated-measures ANOVA revealed that the intervention group had significantly increased (P < 0.05 with Bonferroni correction) plasma beta-carotene, alpha-carotene, lutein and lycopene concentrations at 12 and 36 mo compared with baseline. Baseline carotenoid concentrations were significantly inversely predictive (P < 0.05) of plasma carotenoid change. In addition, change in body mass index (BMI) and plasma cholesterol concentrations were predictive of plasma carotenoid change from baseline to 3 y. Results of this study demonstrate that change in plasma carotenoid concentrations is associated with change in BMI, change in plasma cholesterol and baseline carotenoid concentrations. Plasma carotenoid response can be an indicator of long-term high vegetable intake for women at risk of breast cancer recurrence.  相似文献   
109.
110.
为探讨体外循环(CPB)导致心脏植物神经系统(CAS)损伤的机理,了解温血心停跳液能否防止CPB后心率变异性(HRV)的降低,采用对照方法观察了温血心停跳液与冷晶体心停跳液对狗HRV的影响。结果显示:CPB后温血心停跳液组(WB组)和冷晶体心停跳液组(CC组)的全频谱(TP)、低频(LF)和高频(HF)均较术前明显降低(P<0.05),而且CC组比WB组降低更明显(P<0.05),但LF/HF在组内及组间均无明显变化(P>0.05)。CPB后24小时平均心率(MHR)明显增加(P<0.05),且CC组高于WB组(P<0.05)。本研究表明:采用温血心停跳液或冷晶体心停跳液的CPB不会干扰CAS平衡,但均能使HRV降低,温血心停跳液不能防止HRV损害。  相似文献   
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