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   253459篇
  免费   21255篇
  国内免费   8155篇
耳鼻咽喉   1873篇
儿科学   4695篇
妇产科学   3466篇
基础医学   36957篇
口腔科学   4611篇
临床医学   20619篇
内科学   50899篇
皮肤病学   3592篇
神经病学   17599篇
特种医学   6423篇
外国民族医学   54篇
外科学   20119篇
综合类   31720篇
现状与发展   24篇
一般理论   6篇
预防医学   12825篇
眼科学   2468篇
药学   35396篇
  125篇
中国医学   9407篇
肿瘤学   19991篇
  2024年   2412篇
  2023年   5269篇
  2022年   10279篇
  2021年   12610篇
  2020年   10039篇
  2019年   9437篇
  2018年   8966篇
  2017年   8203篇
  2016年   7857篇
  2015年   9073篇
  2014年   14199篇
  2013年   15449篇
  2012年   13244篇
  2011年   15265篇
  2010年   12484篇
  2009年   12832篇
  2008年   12390篇
  2007年   11397篇
  2006年   10259篇
  2005年   8957篇
  2004年   7519篇
  2003年   6806篇
  2002年   5400篇
  2001年   4563篇
  2000年   3933篇
  1999年   3547篇
  1998年   3275篇
  1997年   3035篇
  1996年   2686篇
  1995年   2378篇
  1994年   2118篇
  1993年   1840篇
  1992年   1574篇
  1991年   1441篇
  1990年   1169篇
  1989年   982篇
  1988年   949篇
  1987年   799篇
  1986年   709篇
  1985年   1974篇
  1984年   2685篇
  1983年   1739篇
  1982年   1881篇
  1981年   1695篇
  1980年   1406篇
  1979年   1219篇
  1978年   1020篇
  1977年   862篇
  1976年   963篇
  1975年   668篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
ABSTRACT: The culture supernatant of the TTK-1 cell line, established from human decidual tissue, was found to contain a factor that strongly suppressed the mixed lymphocyte reaction (MLR). The mechanism of the MLR-suppressive activity as well as the biochemical characterization of this factor was analyzed. The TTK-1 supernatant suppressed the MLR much more strongly than the culture supernatants of the three other malignant cell lines examined. The molecular weight of this factor was estimated to be between 43 kilodaltons (kd) and 67 kd by gel filtration chromatography. The TTK-1 supernatant also suppressed the proliferation of the interleukin 2 (IL-2)-dependent T cell lines, but did not suppress that of the IL-2-independent T cell lines, suggesting that the TTK-1 supernatant inhibited the action of IL-2 and subsequently suppressed the MLR. The fact that the TTK-1 cell line originated from human decidual tissue might imply the important role of this factor in immunological fetomaternal balance.  相似文献   
22.
Abstract — The concentrations of IgA, lysozyme and β-microglobulin (β2-m) were quantitated in wax-stimulated mixed saliva from 28 patients with severe periodontitis and from 28 healthy controls. The mutual correlations between IgA, lysozyme and β2-rn were determined. In patients with periodontitis decreased lysozyme concentrations were detected when compared with controls (P<0.05). The correlation between IgA and β2-m concentrations was highly significant in both groups studied (P<0.0001, and P <0.002), whereas β2-m and lysozyme concentrations were positively correlated in patients but not in controls. In addition, a significant correlation between IgA and lysozyme was found only in periodontal patients ( P <0.001).  相似文献   
23.
Objective To investigate the best way to control the blood sugar level during the perioperation of bone fracture patients with type 2 diabetes(T2DM).Methods Bone fracture patients with T2DM were randomly divided into three groups:continuous subcutaneous insulin infusion group(insulin aspart,group CSII,n=20),glargine treatment group(insulin aspart+insulin glargine,group GA,n=20),and NPH treatment(insulin aspart+rh-insulin,group NA,n=20).The levels of fasting plasma glucose(FPG)and the 2 hours postprandial glucose(2h PG),blood glucose fluctuation(BGF),insulin dosage(ID),good effective time(GET),incidence of hypoglycemia,dawn phenomenon and infection,average time of stitches removal(ATSR),average hospitalized length(AHL)of three groups were compared.Results FPG and 2hPG,ID in group CSII[(6.32±1.18)mmol/L,(7.72±1.53)mmol/L,(35.40±1.60)IU]and group GA [(6.25±0.88)mmol/L,(7.32±1.17)mmol/L,(36.20±0.80)IU]were significantly lower than those of group NA [(7.44±1.36)mmol/L,(8.52±0.76)mmol/L,(40.50±2.40)IU,all P<0.05],simulaneously,BGF,GET incidence of complications,ATSR,AHL of group CSII and GA were significantly lower than those of group NA(all P<0.05).There were not significant difference between group CSII and group GA.Compared with group CSII,group GA had less costs in-hospital and better practicability.Conclusion Both CSII and insulin glargine combined with insulin aspart can effectively,safely,rapidly and stablely control hyperglycemia.and might be the first choice to control blood sugar for bone fracture patients with T2DM in perioperation.  相似文献   
24.
X Dong  M He  X Song  B Lu  Y Yang  S Zhang  N Zhao  L Zhou  Y Li  X Zhu  R Hu 《Diabetic medicine》2007,24(12):1482-1486
AIMS: Our aim was to assess performances of the Cockcroft-Gault and simplified Modification of Diet in Renal Disease (MDRD) formulae in estimating glomerular filtration rate (GFR) in Chinese diabetic populations and their association with vascular risks. METHODS: A total of 1009 patients with Type 2 diabetes were categorized into low estimated GFR groups (GFR < 60 ml/min/1.73 m(2)) and control groups by the two equations. The performances of these formulae were assessed at different stages of kidney function. Carotid artery intima-media thickness (IMT) and the prevalence of diabetic retinopathy or albuminuria were compared among the groups. The ability of these formulae to identify established vascular risk markers using sensitivity, specificity, positive and negative predictive values were also compared. RESULTS: The prevalence of low estimated GFR was 32.7% with the Cockcroft-Gault formula and 5.2% with the MDRD formula, respectively. In low estimated GFR subjects by the MDRD formula, IMT was significantly thicker than those by the Cockcroft-Gault formula (1.2 mm vs. 1.0 mm; P < 0.05), with a higher prevalence of albuminuria (78.4 vs. 52.8%, P < 0.05) and diabetic retinopathy (46.5 vs. 30.5%; P < 0.05). The Cockcroft-Gault formula gave a specificity of 71.7% and a sensitivity of 37.0%, and the MDRD formula gave a specificity of 96.6% and a sensitivity of 7.9% in estimating low GFR relevant for established vascular risks. CONCLUSIONS: These formulae performed differently in Chinese diabetic populations. The simplified MDRD formula is minimally superior to the Cockcroft-Gault formula for its high specificity and positive predictive values in estimating low GFR relevant for vascular risks.  相似文献   
25.
Exposure of captodative enone systems to deuterium in the presence of Crabtree's catalyst ( 1 ) results in deuteration at the vinylic site β‐ to the ketone carbonyl, as well as at any accessible ortho‐position. β‐exchange is also observed during the reduction of ethyl cinnamate ( 3 ) catalyzed by 1 . Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
26.
AIMS: To study the time and cost involved in the care of newly registered outpatients with Type 2 diabetes mellitus (DM), compared with patients with hypertension and/or hyperlipidaemia (HTL). METHODS: A total of 313 patients with DM and 58 patients with HTL without diabetes were registered on their first visits to 11 diabetes clinics across Japan. The time and cost involved in their care was recorded over the following 5 months. RESULTS: In the first 3 months, there was an extensive time commitment to both groups. The time spent by physicians was 1.5 times longer for DM than for HTL. The total care time spent by all the care providers for DM was twice that for HTL. The cost of DM care was twice that for HTL, with the cost of medicines excluded. However, half of the cost for DM was for laboratory tests. When these were excluded, and the remaining cost divided by the time spent, the amount for DM was half of that for HTL. Over the 5 months, mean glycated haemoglobin (HbA(1c)) in DM patients improved from 8.0% to 6.5%, and 72% of DM patients achieved the glycaemic target of HbA(1c) < or = 6.5%. CONCLUSIONS: DM care in a diabetes clinic requires a great deal more time and resources than HTL to achieve the best outcome. An educational system for self care, presently lacking in the primary care setting in Japan, would improve glycaemic control for DM patients in the community.  相似文献   
27.
28.
V Dave  G W Gordon  K D McCarthy 《Glia》1991,4(5):440-447
Very little information is available concerning the pharmacology of type 2 astroglia. During the past decade it has become apparent that two distinct lineages of astroglial cells can be defined in vitro. These two lineages are commonly referred to as type 1 and type 2 and are distinguished from each other on the basis of their morphological features and antigenic phenotypes. In contrast to type 1 astroglia, very little is known about the pharmacology of type 2 astroglia. The lack of information concerning the responsiveness of these cells stems primarily from difficulties encountered in isolating large numbers of type 2 astroglia free of other cell types. In the present study video- and photometer-based imaging systems were used to monitor the influence of a series of neuroligands on the intracellular calcium levels of individual cerebral type 2 astroglia in order to assess their expression of calcium-mobilizing receptors. The responses of 85 immunocytochemically identified cerebral type 2 astroglia to bradykinin (BK), norepinephrine (NE), histamine (HIST), carbachol (CARB), 2-methyl-thio ATP (2MT-ATP), glutamate (GLUT), and serotonin (5-HT) were analyzed. Approximately 50% of cerebral type 2 astroglia responded to BK, NE, HIST, CARB, and 2MT-ATP whereas only 16% and 9% of the cells responded to GLUT and 5-HT, respectively. The number of neuroligands that increased calcium in individual cells ranged from 0 to 6. These responses are quite similar to those previously demonstrated in cultured cerebral type 1 astroglia. No pattern of receptor co-expression was observed for the different neuroligands tests.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
29.
Monoclonal antibodies against human and bovine 2′:3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) were generated by fusing FOX-NY myeloma cells with spleen cells from RBF/Dn mice previously immunized with the purified brain antigens. The enzyme isolated from bovine brain was quite basic, with an isoelectric point of 9.71 and both the bovine and human enzymes consisted of a closely spaced doublet at approximately 44 and 46 kDa on SDS-PAGE. Six monoclonals were identified as strongly recognizing the enzyme on both ELISA plates and on immunoblots of whole brain protein. Four monoclonals very weakly cross-reacted with guinea pig myelin basic protein. In contrast with two previous reports, some of our monoclonal antibodies did immunostain 2 or 3 protein bands in peripheral nerve, two bands closely corresponding to those immunostained in central nervous system (CNS) myelin, the Wolfgram protein fraction and in acetone powders of whole brain. Each of the 6 monoclonals reacting strongly on immunoblots recognized the enzyme in from 2 to 5 of the species examined (human, bovine, rat, mouse and rabbit). In addition, all 6 monoclonals that immunostained the enzyme in whole brain, myelin and Wolfgram protein immunoblots recognized both CNP1 (44 kDa) and CNP2 (46 kDa). The two closely spaced protein bands observed on SDS-PAGE and previously stained on immunoblots of CNS CNPase using polyvalent rabbit anti-bovine CNPase antisera, and now different monoclonal antibodies, appear to be immunologically related and to contain highly conserved sequences.  相似文献   
30.
AIM: To investigate the participation of adenosine receptors in the adenosine 5'-triphosphate (ATP)-induced relaxation in the corpus cavernosum penis (CCP) of rabbits. METHODS: The ATP-induced relaxation was assessed on the noradrenaline precontracted CCP of rabbits in the presence and absence of 8-(3-chlorostyryl)caffeine (CSC); an adenosine A(2A) receptor antagonist; alloxazine and MRS1754; adenosine A(2B) receptor antagonists; and ARL67156, an inhibitor of ecto-nucleoside triphosphate diphosphohydrolases. RESULTS: Adenosine and ATP relaxed the noradrenaline precontracted CCP of rabbits in a concentration-dependent manner. The adenosine- and ATP-induced relaxations were suppressed by alloxazine and MRS1754, but not by 8-(3-chlorostyryl)caffeine. ARL67156 potentiated the ATP-induced relaxation but not the adenosine-induced one. MRS1754 suppressed the ATP-induced relaxation potentiated by ARL67156. CONCLUSIONS: The above results suggest that, in the CCP of rabbits, the adenosine receptor mediating adenosine-induced relaxation is of the A(2B) receptor and the ATP directly causes relaxation through the A(2B) receptor on the CCP.  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