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   7784篇
  免费   372篇
  国内免费   36篇
耳鼻咽喉   114篇
儿科学   196篇
妇产科学   263篇
基础医学   889篇
口腔科学   145篇
临床医学   528篇
内科学   2295篇
皮肤病学   148篇
神经病学   845篇
特种医学   227篇
外科学   1135篇
综合类   11篇
一般理论   3篇
预防医学   258篇
眼科学   157篇
药学   369篇
中国医学   28篇
肿瘤学   581篇
  2023年   69篇
  2022年   118篇
  2021年   215篇
  2020年   126篇
  2019年   164篇
  2018年   207篇
  2017年   142篇
  2016年   160篇
  2015年   172篇
  2014年   267篇
  2013年   325篇
  2012年   513篇
  2011年   508篇
  2010年   298篇
  2009年   275篇
  2008年   468篇
  2007年   426篇
  2006年   402篇
  2005年   443篇
  2004年   393篇
  2003年   333篇
  2002年   315篇
  2001年   203篇
  2000年   171篇
  1999年   154篇
  1998年   76篇
  1997年   56篇
  1996年   56篇
  1995年   63篇
  1994年   53篇
  1993年   36篇
  1992年   106篇
  1991年   110篇
  1990年   79篇
  1989年   85篇
  1988年   68篇
  1987年   56篇
  1986年   53篇
  1985年   49篇
  1984年   56篇
  1983年   47篇
  1982年   32篇
  1980年   24篇
  1979年   38篇
  1978年   20篇
  1976年   16篇
  1975年   19篇
  1974年   15篇
  1972年   13篇
  1967年   13篇
排序方式: 共有8192条查询结果,搜索用时 15 毫秒
91.
92.
Reliable chemical sensors with high selectivity and sensitivity toward specific target molecules require rational synthesis of receptors, in-depth characterization of their complexation abilities and highly efficient transduction of the molecular recognition event. Here we report a steady-state and time-resolved fluorescence investigation of EtQxBox, a fluorescent conformationally blocked quinoxaline-based cavitand, aimed at assessing its selectivity toward aromatic versus non-aromatic analytes in solution. Fluorescence quenching of the EtQxBox in acetone is observed at increasing concentration of both aromatic (i.e. benzonitrile) and aliphatic (i.e. acetonitrile) compounds. The combination with fluorescence lifetime measurements permits to discriminate the predominantly static quenching of the aromatic analyte, due to non-fluorescent host–guest complex formation, from the mostly dynamic quenching of the non-aromatic compound, resulting from aspecific diffusive collisions between the fluorophore and the quencher. The equilibrium association constants for both the complexes have been estimated using Stern–Volmer model.

We investigate the role of combined static and dynamic quenching in fluorescence transduction of benzonitrile and acetonitrile complexation by a rigid quinoxaline-based cavitand.  相似文献   
93.
Cardiovascular Drugs and Therapy - Sacubitril/valsartan, vericiguat, and the sodium-glucose co-transporter-2 inhibitors (SGLT2i) dapagliflozin and empagliflozin proved effective in phase 3 trials...  相似文献   
94.
The long-term changes of liver stiffness (LS) in patients who achieve viral clearance after direct-acting anti-HCV therapy remain undefined. We conducted a multicentre prospective study to investigate this aspect. Patients with HCV infection treated with DAAs were enrolled from six Italian centres; they underwent clinical, biochemical, ultrasound and transient elastography evaluations before treatment (T0), 12 weeks (SVR12) and 24 months (T24) after the end of therapy. Among the 516 consecutive patients enrolled, 301 had cirrhosis. LS significantly decreased from T0 to SVR (14.3 vs 11.1 kPa, p = .002), with a progressive reduction until T24 (8.7 kPa, p < .001). However, only patients with steatosis and those who developed HCC did not experience a late improvement in LS. Multivariate analysis of baseline and follow-up variables identified steatosis as the only independent predictor of failure of LS improvement (OR 1.802, p = .013). ROC curve analysis of the association of LS with the risk of developing HCC showed that SVR12 ≥14.0 kPa had the highest accuracy (sensitivity 82%, specificity 99%; AUC: 0.774). Multivariate analysis revealed that LS was the only variable independently associated with an increased risk of developing HCC (OR 6.470, p = .035). Achieving an SVR was associated with a progressive, long-term decline of LS, suggesting a late improvement in liver fibrosis, besides the resolution of inflammation. Fatty liver and the development of HCC interfered with late reduction of LS. Patients with an LS ≥14 kPa at 12 weeks after the end of treatment were at higher risk for developing HCC.  相似文献   
95.
Journal of Interventional Cardiac Electrophysiology - Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, occurring in 1–2% of the general population. Catheter ablation...  相似文献   
96.
97.
The identification of patients with von Hippel-Lindau (VHL) disease dictates accurate genetic counseling of family members, whereas screening for early detection of visceral and neurological involvement is usually performed by a combination of radiological and nuclear medicine techniques such as ultrasonography or contrast-enhanced computed tomography of the upper abdomen, magnetic resonance imaging of the central nervous system and 131I-metaiodobenzylguanidine-scintigraphy. The role of 111-indium-diethylenetriaminepentaacetic acid [111In-DTPA0] octreotide scintigraphy in this clinical context has never been investigated. Here, we report imaging findings in a VHL patient and in 3 consecutive family members undergoing clinical and radiological screening that included [111In-DTPA0] octreotide scintigraphy in addition to the above-mentioned procedures. Somatostatin receptor expression was investigated in vitro by immunohistochemistry in pancreatic tumor sections. On the basis of in vivo and in vitro findings, octreotide long-acting release treatment followed by 90Y-1,4,7,10-Tetraazacyclododecane-N,N',N',N'-tetraacetic acid (DOTA0)-Tyr3-octreotide led to a lack of progression in this patient although this result is a possibility which needs to be proved by further investigation and longer follow-up. The results of this study suggest that [111In-DTPA0] octreotide scintigraphy may be helpful in the routine work-up of VHL patients for diagnostic and therapeutic purposes.  相似文献   
98.
The absence or very low levels of plasminogen cause a rare disabling disease called ligneous conjunctivitis, characterized by the growth of fibrin-rich pseudomembranes in the conjunctiva and on other mucosal surfaces. Several mutations have been detected in the plasminogen gene of patients affected with ligneous conjunctivitis. The human plasminogen gene, located on chromosome 6, has a marked homology with the genes belonging to the plasminogen-apo(a) family, and with a number of pseudogenes and plasminogen-like genes located on chromosome 2. This work describes a series of nucleotide variations related to genes other than the plasminogen one, found during the genetic characterization of plasminogen defect in two unrelated patients with ligneous conjunctivitis. The results of automated sequences of each exon and intron-exon boundaries were compared with those of the human plasminogen gene from the NCBI gene bank. In particular, a co-amplified gene on chromosome 2 mimicking a 14 bp deletion in exon 5 of the plasminogen gene was identified by sequencing two different bands obtained from a long run of the PCR exon 5 product in NuSieve agarose gel, and by PstI restriction enzyme analysis of the same amplicons. Moreover, 21 single nucleotide exchanges due to plasminogen-like genes co-amplification were observed, namely one in exon 1, two in exon 4, three in exons 3, 5 and 16, four in exon 13, and five in exon 17. In conclusion, these data confirm the difficulty of plasminogen genetic analysis and may help researchers to better identify the true plasminogen gene mutations causing molecular defects.  相似文献   
99.
100.
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