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   47211篇
  免费   3333篇
  国内免费   1461篇
耳鼻咽喉   279篇
儿科学   918篇
妇产科学   445篇
基础医学   7111篇
口腔科学   600篇
临床医学   2505篇
内科学   6228篇
皮肤病学   954篇
神经病学   4898篇
特种医学   673篇
外国民族医学   4篇
外科学   4067篇
综合类   4569篇
现状与发展   2篇
预防医学   2250篇
眼科学   549篇
药学   9943篇
  7篇
中国医学   1666篇
肿瘤学   4337篇
  2024年   107篇
  2023年   988篇
  2022年   2002篇
  2021年   1953篇
  2020年   1510篇
  2019年   1903篇
  2018年   1725篇
  2017年   1582篇
  2016年   1263篇
  2015年   1459篇
  2014年   2249篇
  2013年   2743篇
  2012年   2162篇
  2011年   2653篇
  2010年   2255篇
  2009年   2141篇
  2008年   2210篇
  2007年   2042篇
  2006年   1871篇
  2005年   1582篇
  2004年   1519篇
  2003年   1351篇
  2002年   995篇
  2001年   759篇
  2000年   826篇
  1999年   686篇
  1998年   706篇
  1997年   640篇
  1996年   557篇
  1995年   519篇
  1994年   448篇
  1993年   430篇
  1992年   420篇
  1991年   373篇
  1990年   317篇
  1989年   295篇
  1988年   240篇
  1987年   244篇
  1986年   231篇
  1985年   490篇
  1984年   596篇
  1983年   390篇
  1982年   447篇
  1981年   401篇
  1980年   346篇
  1979年   320篇
  1978年   274篇
  1977年   184篇
  1976年   165篇
  1975年   133篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
3,5-diBr-PADAP直接光度法测定血清锌   总被引:2,自引:0,他引:2  
目的 建立一种不去除血清蛋白、简便灵敏的直接光度法测定血清锌。方法 以新的有机试剂2 -(3 ,5 二溴 -2 -吡啶偶氮 ) -5 -二乙氨基酚 (3 ,5 diBr -PADAP)为显色剂 ,在有表面活性剂存在的Tris-HC1介质中 ,手工分析法和自动分析法测定血清锌。结果 该法线性范围 0~ 80 μmol/L ,手工分析法和自动分析法平均回收率为 99 9%和 10 0 2 % ,批内变异系数 (CV)和批间变异系数分别为 0 0 18、 0 0 17和 0 0 2 8、0 0 2 6,与原子吸收分光光度法比较具有良好的相关性 ,线性回归方程和相关系数分别为Y =1 0 0 4X -0 12 6,r=0 9912和Y =1 0 0 6X -0 195 ,r =0 0 992 8。 89例健康人血清锌含量分别为 8 96~ 2 2 5 2 μmol/L和 8 63~2 2 43 μmol/L (x± 2s)。结论 用 3 ,5 diBr-PADAP直接光度法测定血清锌方法简便、灵敏可靠 ,适合临床应用。  相似文献   
72.
The aim of this study was to investigate markers of serotonin and immune function in suicidal patients. Cytotoxic activity of natural killer cells (NK) and CD16 lymphocytes were studied in 28 suicide attempters and 26 healthy controls, and related in patients to 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF). Patients with CSF 5-HIAA below the median had significantly lower NK cell activity than other patients. CD16 cell frequency was significantly lower in patients than in controls, and patients also tended to have lower NK cell cytotoxicity than healthy controls. There were no statistically significant correlations between 4-hydroxy-3methoxyphenyl glycol (HMPG), homovanillic acid (HVA), CSF cortisol and NK cell activity. The results support the hypothesis of compromised immune function in suicidal patients with evidence of disordered serotonin function.  相似文献   
73.
Conventional PCR-SSP, which is based on an agarose gel-based read-out, has the disadvantages of time-consuming post-PCR steps and low potential for automation. The aim of our study was to sort out these drawbacks by establishing a fluorescence-based PCR-SSP system for HLA-C. The assay relies on the sequence-specific identification of amplicons with individually labeled probes that are cleaved during successful PCR by the 5'-3' exonuclease activity of the Taq-DNA Polymerase. The oligonucleotides are labeled with a unique and spectrally resolvable fluorescent reporter dye at the 5' terminus (FAM or TET) and a common quencher dye at the 3' terminus (TAMRA). In case of amplification, the reporter escapes from the quenching control caused by the physical separation of the dyes, resulting in a significant increase of the reporter fluorescence. This allows simultaneous and differential detection of the specific HLA (FAM) and internal control (TET) product. The HLA-C fluorotyping information is based on the individual reporter fluorescence released by 18 PCR primer mixes. Using this method, we analyzed 145 samples previously typed with conventional PCR-SSP and found a concordance rate of 100%. Furthermore, fluorotyping revealed quantitative results that may indicate the presence of homozygosity by high signal intensities. This provided extra protection not to miss new alleles which are not amplified by the current primer mixes. These features as well as the capability of high sample throughput and the possibility of automation makes fluorotyping an attractive tool for PCR-based HLA typing.  相似文献   
74.
本文报告口服Sumatriptan 100mg对偏头痛急性发作119例次的治疗结果。治疗后4h内显效91例次(76.5%),好转16例次(13.4%),无效12例次(10.1%),总有效率为89.9%。对偏头痛伴随症状恶心、呕吐和畏光、畏声的缓解率分别为94.2%、96%和94.3%。  相似文献   
75.
The mapping of 5-HT2 receptors in the brain using functional imaging techniques has been limited by a relative lack of selective radioligands. Iodine-123 labelled 4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]-5-iodo-2-methoxybenzamide (123I-5-I-R91150 or123I-R93274) is a new ligand for single-photon emission tomography (SPET), with high affinity and selectivity for 5-HT2A receptors. This study reports on preliminary123I-5-I-R91150 SPET, wholebody and blood distribution findings in five healthy human volunteers. Maximal brain uptake was approximately 2% of total body counts at 180 min post injection (p.i.). Dynamic SPET sequences were acquired with the brain-dedicated, single-slice multi-detector system SEM-810 over 200 min p.i. Early peak uptake (at 5 min p.i.) was seen in the cerebellum, a region free from 5HT2A receptors. In contrast, radioligand binding in the frontal cortex increased steadily over time, up to a peak at approximately 100–120 min p.i. Frontal cortex-cerebellum activity ratios reached values of 1.4, and remained stable from approximately 100 min p.i. onwards. Multi-slice SPET sequences showed a pattern of regional variation of binding compatible with the autoradiographic data on the distribution of 5-HT2A receptors in (cerebral cortex>striatum>cerebellum). These findings suggest that123I-5-I-R91150 may be used for the imaging of 5-HT2A receptors in the living human brain with SPET.  相似文献   
76.
77.
Activities of the xenobiotic metabolizing enzymes were measured in the liver, kidney, duodenum and lung microsomes and cytosol fractions of Wistar rats after subchronic administration of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a potent bacterial mutagen in chlorinated drinking water. MX was administered by gavage at the dose level of 30 mg/kg for 18 weeks (low dose), or at the dose level which was raised gradually from 45 mg/kg for 7 weeks via 60 mg/kg for 2 weeks to a clearly toxic dose of 75 mg/kg for 5 weeks (high dose). Microsomal and cytosolic preparations were made and the activities of 7-ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-dealkylase (PROD), NADPH-cytochrome-c-reductase, UDP-glucuronosyltransferase (UDPGT) and glutathione-S-transferase (GST) were measured. Kidneys were affected most. A dose-dependent decrease was observed in EROD (90% in males, 80% in females at the high dose) and in PROD (58% in females, at the high dose) in kidneys. An increase was, however, detected in kidney NADPH-cytochrome-c-reductase (66% in females at high dose), UDPGT (89% in males and 97% in females at high dose) and GST activities (56% in males and 50% in females at high dose). MX caused only a few changes in the enzyme activities of the liver. The EROD activity was decreased 25% to 37%, both in the livers of males and females, but the total content of P450s was not altered. Hepatic GST activity was elevated in females in a dose-dependent manner (31% and 44%). GST activity was elevated in duodenum in females (59%) at the high dose. There were no marked changes in the enzyme activities in the lungs. MX was a weak inhibitor of EROD activity both in the liver and kidney microsomes in vitro, decreasing the EROD activity by 53% and 43%, respectively at the concentration of 0.9 mM. The results indicate that MX decreases the activity of phase I metabolism enzymes, but induces phase II conjugation enzyme activities, particularly in kidneys in vivo. It is possible that these changes contribute to metabolism of MX in kidneys and renders them susceptible to MX in the course of repeated exposure.  相似文献   
78.
气功对冠心病人CM_5ST段/心率斜率的影响   总被引:1,自引:0,他引:1  
37名冠心病患者随机分为气功治疗组(22人)和对照组(15人)。气功治疗组接受12周动功治疗,对照组接受安慰剂治疗,治疗前后均测定CM_5 ST段/心率斜率。结果发现动功治疗组CM_5 ST段/心率斜率减少,而对照组不变或增大,两组有显著性差异,ST段下移及常规分级运动试验其它指标在两组间无显著差异。表明CM_5ST段/心率斜率是一个敏感的心肌缺血指标。  相似文献   
79.
80.
小檗碱对大鼠阴茎海绵体磷酸二酯酶5mRNA水平的影响   总被引:3,自引:0,他引:3  
目的 :检测大鼠阴茎海绵体中磷酸二酯酶 5 (PDE5 )mRNA的表达 ,进而探讨小檗碱 (berberine ,Ber)的分子作用机制。 方法 :通过逆转录酶链反应 (RT PCR)技术检测大鼠阴茎海绵体中PDE5mRNA的表达。 结果 :大鼠阴茎海绵体中有PDE5A1和PDE5A2mRNA的表达 ,以PDE5A2为主要的异构酶。与内参照 β 肌动蛋白相比 ,对照组、Ber孵育 1和 3h组的PDE5A1及PDE5A2基因mRNA的相对表达量分别为 :0 .2 2± 0 .0 2 ,0 .4 1± 0 .0 1 ;0 .1 5± 0 .0 1 ,0 .34± 0 .0 2 ;0 .1 0± 0 .0 1 ,0 .1 2± 0 .0 1。与对照组相比 ,PDE5A1、PDE5A2的mRNA表达 ,在Ber孵育 1h组降低了 32 %和 1 7%,3h组降低了 5 5 %和 71 %,其中尤以应用Ber 3h后PDE5A2的mRNA减少最为明显 (n =5 ,P <0 .0 1 )。 结论 :Ber对NO cGMP信号通路的下游关键酶 (PDE5 )具有一定的调控作用 ,尤其是抑制PDE5A2的mRNA表达 ,为Ber治疗勃起功能障碍的分子机制之一。  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