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   2687篇
  免费   122篇
  国内免费   16篇
耳鼻咽喉   38篇
儿科学   55篇
妇产科学   60篇
基础医学   353篇
口腔科学   58篇
临床医学   144篇
内科学   687篇
皮肤病学   111篇
神经病学   191篇
特种医学   68篇
外科学   405篇
综合类   5篇
预防医学   51篇
眼科学   5篇
药学   274篇
中国医学   17篇
肿瘤学   303篇
  2023年   11篇
  2022年   27篇
  2021年   42篇
  2020年   39篇
  2019年   23篇
  2018年   37篇
  2017年   32篇
  2016年   45篇
  2015年   50篇
  2014年   56篇
  2013年   80篇
  2012年   101篇
  2011年   130篇
  2010年   69篇
  2009年   58篇
  2008年   112篇
  2007年   151篇
  2006年   152篇
  2005年   156篇
  2004年   130篇
  2003年   147篇
  2002年   152篇
  2001年   62篇
  2000年   63篇
  1999年   84篇
  1998年   44篇
  1997年   31篇
  1996年   44篇
  1995年   44篇
  1994年   30篇
  1993年   40篇
  1992年   58篇
  1991年   47篇
  1990年   41篇
  1989年   43篇
  1988年   46篇
  1987年   40篇
  1986年   39篇
  1985年   34篇
  1984年   24篇
  1983年   22篇
  1982年   14篇
  1981年   15篇
  1980年   14篇
  1979年   15篇
  1973年   11篇
  1971年   12篇
  1970年   12篇
  1969年   11篇
  1967年   9篇
排序方式: 共有2825条查询结果,搜索用时 31 毫秒
51.
52.
53.
The purpose of our study was to evaluate the diagnostic accuracy of the ultrasound-guided attenuation parameter (UGAP) for the detection of hepatic steatosis in comparison with the controlled attenuation parameter (CAP), using histopathology as the reference standard. We prospectively analyzed 163 consecutive chronic liver disease patients who underwent UGAP, CAP, computed tomography and a liver biopsy on the same day between April 2016 and July 2017. Radiofrequency signals corresponding to the images were compensated by the reference signal previously measured from the uniform phantom with known attenuation (0.44 dB/cm/MHz). The attenuation coefficient was calculated from the signals’ decay slope. The median attenuation coefficient values in patients with S0 (n?=?62), S1 (n?=?63), S2 (n?=?23) and S3 grade (n?=?15) were 0.485, 0.560, 0.660 and 0.720, respectively. Significant correlations were found between attenuation coefficient and percentage steatosis, CAP values and liver-to-spleen computed tomography attenuation ratio (p < 0.001). The areas under the receiver operating characteristic curve of UGAP for identifying ≥S1, ≥S2 and ≥S3 were 0.900, 0.953 and 0.959, respectively, which were significantly better than the results obtained with CAP for identifying ≥S2 and ≥S3. In conclusion, UGAP had high diagnostic accuracy for detecting hepatic steatosis in patients with chronic liver disease  相似文献   
54.
The DNA sliding clamp is a multifunctional protein involved in cellular DNA transactions. In Archaea and Eukaryota, proliferating cell nuclear antigen (PCNA) is the sliding clamp. The ring‐shaped PCNA encircles double‐stranded DNA within its central hole and tethers other proteins on DNA. The majority of Crenarchaeota, a subdomain of Archaea, have multiple PCNA homologues, and they are capable of forming heterotrimeric rings for their functions. In contrast, most organisms in Euryarchaeota, the other major subdomain, have a single PCNA forming a homotrimeric ring structure. Among the Euryarchaeota whose genome is sequenced, Thermococcus kodakarensis is the only species with two genes encoding PCNA homologues on its genome. We cloned the two genes from the T. kodakarensis genome, and the gene products, PCNA1 and PCNA2, were characterized. PCNA1 stimulated the DNA synthesis reactions of the two DNA polymerases, PolB and PolD, from T. kodakarensis in vitro. PCNA2, however, only had an effect on PolB. We were able to disrupt the gene for PCNA2, whereas gene disruption for PCNA1 was not possible, suggesting that PCNA1 is essential for DNA replication. The sensitivities of the Δpcna2 mutant strain to ultraviolet irradiation (UV), methyl methanesulfonate (MMS) and mitomycin C (MMC) were indistinguishable from those of the wild‐type strain.  相似文献   
55.
This study was undertaken to determine the effect of synthetic chicken vasoactive intestinal peptide (VIP) on pancreatic blood flow, exocrine and endocrine secretions of the pancreas, and biliary secretion in dogs. The effect of synthetic chicken VIP on pancreatic blood flow and systemic arterial pressure was identical to that of natural chicken VIP in dogs. The present study demonstrated that synthetic chicken VIP induces significant increases in pancreatic blood flow, pancreaticobiliary secretion, and blood levels of insulin and glucose in dogs. Both the volume of pancreatic juice and blood levels of insulin were increased in consonance with the increase of pancreatic blood flow. This study suggests that the stimulatory effects of synthetic chicken VIP on exocrine and endocrine secretions of the pancreas may be related to the increased pancreatic blood flow elicited by synthetic chicken VIP.  相似文献   
56.
Pyoderma gangrenosum is an intractable skin disorder characterized by the development of erythematous pustules or nodules that rapidly progress to destructive, necrotizing, non-infective ulcers. We assessed the efficacy of granulocyte and monocyte adsorption apheresis (GCAP) therapy in two new patients, a 67-year-old man with ulcerations on his lower leg, and a 44-year-old man with turgid erythematous lesions with burrowing abscesses and sinus formation on his hip, groin, and thighs. Both patients received 10 GCAP treatments at 5-day intervals. Their skin lesions responded well. The 9 cmx6 cm ulcer on the lower right leg of the 67-year-old patient was completely covered by regenerated skin at the completion of therapy. The turgid skin lesions containing pustules and ulcers of the other patient showed amelioration and a marked decrease in the volume of exudate. Our results suggest that GCAP is a useful treatment modality for pyoderma gangrenosum.  相似文献   
57.
Ceramide has been confirmed to be a signal mediator of apoptosis that is induced by tumor necrosis factor-alpha (TNF-alpha). It has also been reported that ceramide may induce insulin resistance as well as TNF-alpha. We investigated the effect of ceramide on insulin signaling pathways, such as insulin receptor (IR) beta-subunit, insulin receptor substrate 1 (IRS-1), phosphatidylinositol 3-kinase (PI3K), and protein kinase Czeta (PKCzeta) in rat adipocytes. We examined insulin-stimulated [(3)H]2-deoxyglucose (2-DOG) uptake in rat adipocytes pretreated with N-hexanoylsphingosine (C(6)-ceramide, 10 to 30 micromol/L). Insulin-induced 2-DOG uptake was significantly reduced by C(6)-ceramide pretreatment. We also examined the effect of various concentrations of C(6)-ceramide pretreatment on insulin-induced autophosphorylation of the IR beta-subunit, tyrosine phosphorylation of IRS-1, enzyme activity of PI3K, and membrane-associated PKCzeta immunoreactivity. Pretreatment with C(6)-ceramide significantly reduced autophosphorylation of the IR beta-subunit, tyrosine phosphorylation of IRS-1, and enzyme activity of PI3K. Moreover, membrane-associated PKCzeta immunoreactivity and immunoprecipitable PKCzeta enzyme activity, downstream of PI3K, were significantly suppressed by C(6)-ceramide pretreatment. These results suggest that ceramide may induce insulin resistance via the suppression of IRS-1-PI3K signaling, and subsequent activation of PKCzeta.  相似文献   
58.
Digestive Diseases and Sciences - NLRP3 inflammasomes have been reported to have a key role in the initiation and perpetuation of inflammatory bowel diseases (IBD). Here we investigated the effects...  相似文献   
59.
A G-to-A (UCSNP-43) polymorphism of the calpain-10 gene was significantly associated with type 2 diabetes (DM) in Mexican-American, and was postulated, together with a T-to-C (UCSNP-44) polymorphism, as a risk factor for DM. We examined the association of these genotypes with DM in Japanese. Eighty-one subjects with DM and 81 non-diabetic subjects (NGT) were recruited. The number of subjects with genotypes UCSNP-43 G/G, G/A and A/A were 76, 5 and 0, respectively, for the DM and NGT groups. The number of subjects with genotypes UCSNP-44 T/T, T/C and C/C were 66, 14 and 1 for the DM group and 64, 17 and 0 for the NGT group. There was no difference between the groups in terms of frequency of any genotype combinations. No association between the genotypes and DM was observed. We next examined the differences between the genotypes or genotype combinations in terms of the traits related to DM, obesity, hypertension and dyslipidemia. No differences were observed between the genotypes UCSNP43 G/G and G/A, between UCSNP-44 T/T and the others, or between the genotype combination UCSNP-43 G/G and UCSNP-44 T/T and the others, except that the individuals with the genotype combination had significantly increased serum cholesterol levels (212.6 +/- 34.3 vs. 198.5 +/- 29.9, P=0.020). The genotype combination might be a risk factor, not for DM, obesity and hypertension, but for increased serum cholesterol.  相似文献   
60.
We examined which relapse criteria best predict the mortality risk of treated male alcoholics. The subjects were 172 male alcoholics who had previously been hospitalized. Using three criteria which defined relapse as failure to maintain abstinence from alcohol, alcohol abuse, or dependence, the relapse of each subject had been evaluated during a previous 3-year outcome study. Relative mortality risks in the next 3 years classified by the three relapse criteria were compared. The follow-up rate was 93.6% and 31 subjects died. The age-corrected relative mortality risk for subjects failing to maintain abstinence compared with abstainers was 5.32, while the relative mortality risks for the group abusing alcohol and for the group suffering alcohol dependence were 2.23 and 2.56, respectively. These results suggest that relapse defined as failure to maintain abstinence predicts a higher relative mortality risk than do criteria defining in terms of alcohol abuse and alcohol dependence.  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