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   1338篇
  免费   89篇
  国内免费   44篇
耳鼻咽喉   11篇
儿科学   70篇
妇产科学   6篇
基础医学   93篇
口腔科学   35篇
临床医学   132篇
内科学   194篇
皮肤病学   23篇
神经病学   17篇
特种医学   151篇
外国民族医学   1篇
外科学   99篇
综合类   231篇
预防医学   108篇
眼科学   14篇
药学   134篇
中国医学   76篇
肿瘤学   76篇
  2023年   7篇
  2022年   13篇
  2021年   28篇
  2020年   18篇
  2019年   8篇
  2018年   15篇
  2017年   28篇
  2016年   17篇
  2015年   37篇
  2014年   59篇
  2013年   71篇
  2012年   82篇
  2011年   101篇
  2010年   87篇
  2009年   74篇
  2008年   98篇
  2007年   76篇
  2006年   52篇
  2005年   45篇
  2004年   33篇
  2003年   40篇
  2002年   35篇
  2001年   36篇
  2000年   22篇
  1999年   20篇
  1998年   27篇
  1997年   31篇
  1996年   24篇
  1995年   17篇
  1994年   10篇
  1993年   14篇
  1992年   8篇
  1991年   17篇
  1990年   9篇
  1989年   19篇
  1988年   17篇
  1987年   17篇
  1986年   16篇
  1985年   15篇
  1984年   8篇
  1983年   16篇
  1982年   15篇
  1981年   13篇
  1980年   10篇
  1979年   9篇
  1978年   9篇
  1977年   11篇
  1976年   9篇
  1975年   9篇
  1968年   3篇
排序方式: 共有1471条查询结果,搜索用时 31 毫秒
1.
In an open, randomized cross-over study in 124 patients, we compared the efficacy, safety and patient preference of oral and subcutaneous sum triptan in the acute treatment of migraine. Patients were treated for 3 attacks or 3 months and then crossed over. Primary clinical efficacy was defined as a reduction in headache severity on a four-point self-rating scale from severe (3) or moderate (2) to mild (1) or none (0), or mild (1) to none (0). Efficacy was evaluated 2 h after the administration of subcutaneous and 4h after the administration of oral sumatriptan. Subcutaneous sumatriptan was significantly more effective than oral sumatriptan in relieving headache (over all three attacks 78% vs 61% improvement), improving clinical disability (55% vs 41 % improvement) and relieving nausea (69% vs 53%), vomiting (72% vs 32%) and phono- or photophobia (67% vs 49%). Median time to recurrence was shorter after subcutaneous (12.5 h) than after oral sumatriptan (18 h); the number of patients experiencing a recurrence was similar Patients reported more adverse events after subcutaneous sumatriptan (1.32 per attack) than after the oral form (0.85 per attack), but all adverse events were mild to moderate in intensity and of short duration. Patient opinion was more often positive after subcutaneous sumatriptan. These results may be useful in counselling patients to choose between the available marketed formulations of sumatriptan.  相似文献   
2.
The enantiomers of the positive inotropic and a1-adrenoceptor blocking agent saterinone (+/-)-1,2-dihydro-5-[4-[2-hydroxy-3- [4-(2-methoxyphenyl)-1-piperazinyl]propoxy] phenyl]-6-methyl-2-oxo-3-pyridine-carbonitrile, BDF 8634) have been investigated with in vitro and in vivo models in laboratory animals. In the guinea pig papillary muscle, saterinone enantiomers had equipotent inotropic activity and were also as potent as racemic saterinone; the (R)-enantiomer, however, exhibited a greater efficacy than the related compounds. Saterinone and its enantiomers were equipotent in the inhibition of phosphodiesterase PDE III activity in the guinea pig myocardium. The equipotent inotropic effects were also observed after parenteral and enteral administration in cats. In receptor binding studies, (S)-saterinone was 10-fold more potent than (R)-saterinone by inhibiting [3H]-prazosin binding to specific alpha 1-adrenoceptor sites in rat brain cortex membranes. However, in the isolated thoracic aorta of the rabbit, (S)-saterinone was only 3-fold more potent than (R)-saterinone at preventing the pressor effects of phenylephrine. When the enantiomers were tested in vivo against the pressor effects of phenylephrine in the pithed rat, (S)-saterinone was only 2-fold more potent than (R)-saterinone in its alpha 1-adrenoceptor blocking potency. Thus the enantiomers of saterinone do not display enantio-selectivity in their inotropic and PDE III inhibitory effects in vitro, nor in their cardiotonic effects in vivo. There is a slight enantio-selectivity at alpha 1-adrenoceptors in receptor binding studies, but this is reduced to biologically irrelevant magnitude in functional studies in vitro and in vivo.  相似文献   
3.
4.
目的:制备分散性良好的超细β-磷酸三钙(β-TCP)/聚-L-乳酸(PLLA)复合材料及新型可吸收骨折内固定器。方法:通过研磨方法制备β-TCP超细粒子,用一缩二乙二醇作分散剂研磨β-TCP后,再将β-TCP与PLLA超声混合,制得复合材料,经注塑加工制成可吸收骨钉,并采用扫描电镜等方法进行表征。结果与结论:用一缩二乙二醇作分散剂研磨β-TCP后再经超声混合,可以使β-TCP超细粒子在复合材料中分散均匀,粒子大小仅为300nm左右,β-TCP与PLlA基体之间结合良好。超细β-TCP/PLLA复合材料可加工成可吸收骨钉,弯曲强度达到100MPa左右,完全满足松质骨内固定的要求。  相似文献   
5.
BACKGROUND: Pemphigus vulgaris (PV) is a severe blistering disease involving the skin and mucous membranes. The most common causes of death in these patients are adverse effects of drugs, and infection. Skin lesions are one of the important sources of infection. Thus, any local treatment that could reduce healing time of lesions and consequently reduce the total dosage of drugs needed to treat is favourable. OBJECTIVE: To evaluate the efficacy of epidermal growth factor (EGF) in reducing healing time of lesions in patients with pemphigus vulgaris. METHODS: In this randomized, double-blind, within-patient, left/right, controlled trial, 20 hospitalized patients with pathologial and immunohistologial (direct and indirect immunoflourecence) proven pemphigus vulgaris (PV) were chosen. In addition, all patients had at least one appropriate pemphigus lesion on each side of the body that had not healed after 2-week systemic therapy and sterile saline washing. EGF (10 microg/g) in 0.1% silver sulfadiazine cream vs. 0.1% silver sulfadiazine cream alone was applied randomly on one side of the body. RESULTS: Kaplan-Meier survival analysis suggested that median time to heal with application of EGF plus silver sulfadiazine cream was 9 days, in comparison with 15 days for silver sulfadiazine cream alone (log-rank test, P=0.0003). No intervention-related adverse effect was observed during the study. CONCLUSIONS: EGF can significantly reduce healing time of skin lesions in patients with pemphigus vulgaris, at least when this cream base is applied (Cochrane skin group identifier: CSG20).  相似文献   
6.
Children with anomalous origin of the left coronary artery from the pulmonary artery are at risk for myocardial infarction and death. Surgical management of this condition in children has evolved significantly during the past 20 years. Between 1970 and 1990, a total of 20 of these patients underwent surgical intervention at two institutions. Age at operation ranged from 3 weeks to 11 years (mean, 26 months). Twelve patients had congestive heart failure, three were in cardiogenic shock, and two had cardiac murmurs. Operative techniques included ligation (n = 9), subclavian artery anastomosis (n = 5), aortic implantation (n = 3), internal mammary artery anastomosis (n = 1), intrapulmonary tunnel from aortopulmonary window to coronary artery (n = 1), and cardiac transplantation (n = 1). The three deaths in the series occurred at 3 weeks, at 2 months, and at 9 years after ligation. There have been no deaths after establishment of a two coronary artery system or after transplantation. Two of the five patients who had subclavian artery anastomosis to the anomalous coronary artery have severe anastomotic stenosis and collateralization. For patients with anomalous origin of the left coronary artery from the pulmonary artery, we recommend direct aortic implantation of the anomalous coronary artery at the time of diagnosis. Intrapulmonary tunnel from aortopulmonary window to coronary artery, or aorta-coronary bypass with internal mammary artery are recommended for children in whom aortic implantation is not anatomically feasible. Left coronary artery ligation is not indicated for these patients; those who have survived ligation should be considered for elective establishment of a two coronary artery system because of the risk of late death.  相似文献   
7.
Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system. While its etiology is not well understood, genetic factors are clearly involved. Until recently, most genetic studies in MS have been association studies using the case-control design testing specific candidate genes and studying only sporadic cases. The only consistently replicated finding has been an association with the HLA-DR2 allele within the major histocompatibility complex (MHC) on chromosome 6. Using the genetic linkage design, however, evidence for and against linkage of the MHC to MS has been found, fostering suggestions that sporadic and familial MS have different etiologies. Most recently, two of four genomic screens demonstrated linkage to the MHC, although specific allelic associations were not tested. Here, a dataset of 98 multiplex families was studied to test for an association to the HLA-DR2 allele in familial MS and to determine if genetic linkage to the MHC was due solely to such an association. Three highly polymorphic markers (HLA-DR, D6S273 and TNFbeta) in the MHC demonstrated strong genetic linkage (parametric lod scores of 4.60, 2.20 and 1.24, respectively) and a specific association with the HLA-DR2 allele was confirmed (TDT; P < 0.001). Stratifying the results by HLA-DR2 status showed that the linkage results were limited to families segregating HLA-DR2 alleles. These results demonstrate that genetic linkage to the MHC can be explained by the HLA-DR2 allelic association. They also indicate that sporadic and familial MS share a common genetic susceptibility. In addition, preliminary calculations suggest that the MHC explains between 17 and 62% of the genetic etiology of MS. This heterogeneity is also supported by the minority of families showing no linkage or association with loci within the MHC.   相似文献   
8.
X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.   相似文献   
9.
Fluoride controlled release tablets for intrabuccal use   总被引:1,自引:0,他引:1  
Diarra M  Pourroy G  Boymond C  Muster D 《Biomaterials》2003,24(7):1293-1300
We have developed a fluoride controlled release delivering system for intrabuccal use, permitting to reach high enough local concentrations for desirable therapeutic effect with minimal side effects. We have formulated tablets of 160-200mg intended to be fixed on a tooth. The tablets have a granular matrix composed of pure hydroxyapatite, Eudragit((R)) and/or ethylcellulose. NaF is added either by a mechanical mixing or an impregnation method. Profiles of continuous in vitro drug release in saline phosphate buffered solution were recorded by means of a fluoride selective electrode. Linear profiles are observed when ethylcellulose is used. The most reproducible results are obtained when the impregnation method is used. Eudragit((R)) increases the dissolution efficiencies while ethylcellulose decreases it.  相似文献   
10.
Muster W  Albertini S  Gocke E 《Mutagenesis》2003,18(4):321-329
In recent years genotoxicity testing has become more and more important in the process of early screening for potential development compounds. In the case that a pharmacologically interesting structure is found to be positive in an in vitro mutagenicity test a straightforward approach starts by sorting out what substructure is responsible for the activity observed in the test. The Ames test is a rapid, convenient test system which has been effectively used in structure-activity relationship studies for mutagenicity, since it can rapidly establish differences in the mutagenic action of isomers and chemical analogs. The lead compound with a benzodiazepine-like structure and close analogs exhibited weak, but unequivocal positive effects in the Ames test (strains TA1535 and TA 100) after metabolic activation by rat liver homogenate fraction (S9). To identify substances within this class of compounds devoid of mutagenic liability an extensive structure-activity investigation was undertaken. More than 50 compounds were tested in the two critical bacterial strains, using a standard plate incorporation and a preincubation modification. It quickly became evident that the benzodiazepine structure was not involved. First hints that the allyl side chain were responsible for the Ames activity had to be refined in a more complex, but clear-cut structure-activity relationship during the course of the experiments. It was shown that all compounds with an allyl side chain, independent of the heterocycle, but surprisingly also all compounds with a specific arrangement of the heteroatoms in the oxadiazole ring, showed positive effects in at least one strain. Based on these investigations it was possible to select pharmacologically active structures without mutagenic liability.  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