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   2299篇
  免费   155篇
  国内免费   49篇
耳鼻咽喉   20篇
儿科学   84篇
妇产科学   33篇
基础医学   229篇
口腔科学   74篇
临床医学   258篇
内科学   401篇
皮肤病学   29篇
神经病学   93篇
特种医学   193篇
外科学   256篇
综合类   233篇
预防医学   198篇
眼科学   21篇
药学   209篇
中国医学   76篇
肿瘤学   96篇
  2023年   13篇
  2022年   23篇
  2021年   49篇
  2020年   28篇
  2019年   20篇
  2018年   34篇
  2017年   35篇
  2016年   38篇
  2015年   56篇
  2014年   86篇
  2013年   111篇
  2012年   138篇
  2011年   153篇
  2010年   106篇
  2009年   101篇
  2008年   143篇
  2007年   105篇
  2006年   95篇
  2005年   95篇
  2004年   86篇
  2003年   75篇
  2002年   74篇
  2001年   75篇
  2000年   71篇
  1999年   55篇
  1998年   37篇
  1997年   40篇
  1996年   35篇
  1995年   23篇
  1994年   20篇
  1993年   20篇
  1992年   24篇
  1991年   28篇
  1990年   21篇
  1989年   35篇
  1988年   41篇
  1987年   28篇
  1986年   37篇
  1985年   36篇
  1984年   24篇
  1983年   13篇
  1982年   14篇
  1981年   18篇
  1980年   13篇
  1979年   17篇
  1978年   12篇
  1977年   13篇
  1975年   15篇
  1973年   10篇
  1972年   6篇
排序方式: 共有2503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.
3.
W G Luttge  M E Rupp  S M Emadian 《Endocrinology》1989,124(4):1813-1821
Incubation of [3H]aldosterone-type I receptor complexes in mouse brain cytosol with the chaotropic anion thiocyanate increased the fraction of receptors retained by DNA-cellulose from less than 10% to over 40%, whereas it decreased the fraction retained by protamine sulfate from more than 90% to less than 10%. Thiocyanate-induced transformation to the DNA-binding species was also accompanied by a 2.1-fold decrease in the rate of [3H]aldosterone dissociation from type I receptors as well as by an increase in the apparent positive charge and hydrophobicity of the surface of these receptors, as revealed by DEAE Bio-Gel ion exchange and pentyl agarose hydrophobic interaction chromatography. Sucrose density gradient sedimentation and Sephacryl S-300 gel exclusion chromatography revealed a reduction in the sedimentation coefficient and Stokes radius of the steroid-receptor complex from 9.6S and 8.0 nm before to 4.7S and 6.1 nm after transformation, respectively. These changes in hydrodynamic parameters were found to correspond to a 2.8-fold reduction in the apparent molecular mass from 331,000 before to 120,000 after transformation. In view of these various findings as well as the known differential affinity of protamine sulfate for the 90K heat shock protein, we suggest that thiocyanate-induced transformation is initiated by the dissociation of two molecules of heat shock protein from each steroid/DNA-binding type I receptor subunit.  相似文献   
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.
7.
In this report we compare the bioactivities of pure, human monocyte-derived interleukin 1 (IL-1) alpha and beta in the standard murine thymocyte proliferation assay, a human dermal fibroblast proliferation assay, and in an assay measuring stimulation of prostaglandin E2 (PGE2) release from human rheumatoid synoviocytes. In each case the different species of IL-1 produced saturable stimulation and gave similar dose response curves. Half-maximal stimulation was observed at average IL-1 concentrations of 29 pM in the thymocyte assay, 2 pM in the dermal fibroblast proliferation assay, and 5 pM in the synovial cell assay. Our results show that native, monocyte-derived IL-1 alpha and IL-1 beta are both potent stimulators of connective tissue cells and that the specific bioactivities of these molecules are similar to each other in tests on human connective tissue cells, as well as on murine lymphoid cells.  相似文献   
8.
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   
9.
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   
10.
As a result of inflammatory processes, plaque formation on dental titanium implants often leads to clinically pathogenic situations. This special biofilm formation on (bio)materials in contact with saliva is initiated by ionic and protein interactions. In this interfacial process, albumin becomes a main constituent of dental pellicle. Interfacial reactions change the surface characteristics. They determine the following steps of macromolecular adsorption and bacterial adhesion. This work focuses on the dynamic contact angle analysis (DCA), which is a tool for online measurements of dynamic changes of wettability without disturbing the interface during detection. Repeatability of the DCA method has been assessed according to the Bland and Altman method. The kinetics and equilibrium data of shifts in the wetting tension hysteresis indicate ionic influences at the titanium/bovine serum albumin (BSA) interface: the Ca-mediated increase of the BSA adsorption on titanium and the adsorption maximum at the isoelectric point (IEP) of BSA. Ti was surface modified by Teflon AF polymeric coatings. The result of the assessment gives reason to consider Teflon AF as a reference material for DCA repeatability studies. This surface modification caused drastic changes in the dynamic interfacial reactions. Shifts in the wetting tensions during DCA adsorption-desorption experiments clearly demonstrated the partially irreversible adsorption of BSA on Teflon AF. In contrast, reversible adsorption behavior was detected on pure Ti surfaces. These findings strengthen the hypothesis that the analysis of dynamic changes in wetting tension and wetting tension hysteresis is a sensitive analytical method for the detection of dynamic interfacial changes at biomaterial/biosystem interfaces during the initial steps of biofilm formation.  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