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   22725篇
  免费   351篇
  国内免费   31篇
教育   16311篇
科学研究   2023篇
各国文化   204篇
体育   1743篇
综合类   34篇
文化理论   216篇
信息传播   2576篇
  2022年   136篇
  2021年   232篇
  2020年   376篇
  2019年   513篇
  2018年   710篇
  2017年   791篇
  2016年   739篇
  2015年   434篇
  2014年   593篇
  2013年   4264篇
  2012年   580篇
  2011年   639篇
  2010年   493篇
  2009年   460篇
  2008年   524篇
  2007年   504篇
  2006年   442篇
  2005年   387篇
  2004年   365篇
  2003年   329篇
  2002年   383篇
  2001年   425篇
  2000年   400篇
  1999年   402篇
  1998年   211篇
  1997年   230篇
  1996年   257篇
  1995年   215篇
  1994年   214篇
  1993年   195篇
  1992年   304篇
  1991年   301篇
  1990年   329篇
  1989年   311篇
  1988年   295篇
  1987年   248篇
  1986年   256篇
  1985年   323篇
  1984年   266篇
  1983年   256篇
  1982年   196篇
  1981年   206篇
  1980年   176篇
  1979年   240篇
  1978年   214篇
  1977年   194篇
  1976年   160篇
  1975年   128篇
  1974年   120篇
  1973年   147篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
Abstract

Ludwig Wittgenstein suggests that ‘A serious and good philosophical work could be written consisting entirely of jokes’. The idea for this dialogue comes from a conversation that Michael Peters and Morwenna Griffiths had at the Philosophy of Education of Great Britain annual meeting at the University of Oxford, 2011. It was sparked by an account of an assessment of a piece of work where one of the external examiners unexpectedly exclaimed ‘I knew Jean-Paul Sartre’, trying to trump the discussion. This conversation is a dialogue about comedy and humor as a basis for philosophy, education and pedagogy that provides an introduction to recent works and a context for ongoing research. The concluding section provides further reflection on some of the main themes, drawing attention to the significance of humor in dialogues within philosophy and education, and suggesting that it has a particular role in resisting managerialism at all levels of educational institutions.  相似文献   
942.
Throughout his distinguished career of over 40 years, Robin Hochstrasser has made significant contributions to several areas of science in the fields of chemical and biochemical physics. He has been at the forefront and made fundamental contributions to the fields of photochemistry, solid-state chemistry, ultra-fast laser spectroscopies, and protein dynamics. He has been a prolific researcher, producing over 560 publications. His work has been characterized by experts in the fields as “a constant stream of experiments of lasting significance” (J. Phys. Chem. 100 (1996) 11791).Robin began his career in the 1960s using a variety of magnetic and electric field measurements to study crystals at low temperatures to understand spin quantization in solids and electron exchanged-mediated energy transfer. This work, described as a “classic contribution” (J. Phys. Chem. 100 (1996) 11791) was the basis for much of the subsequent experimental and theoretical work on the effect of magnetic fields on molecular spectra and on the measurements of dipole moments.In the late 1970s, Robin recognized the power of laser technology for the study of molecules and soon became a leader in the field investigating solid, gas phase, and condensed phase systems. He developed and applied various ultra-fast laser techniques to study the structure and dynamics of complex molecules in liquid phase, chemical, and biochemical reactions. He made seminal contributions to the development of two-dimensional infrared spectroscopy (2D IR) on a time scale of a picosecond or less. This 2D IR spectroscopy measures coupling between two functional groups in a large molecule and can thus be used to measure distances, as for example, two amide carbonyl groups in a peptide molecule. On the ultra-fast timescale, one application of 2D IR is to gain information on the rate of protein folding and unfolding in solution. Some of Robin's greatest contributions to understanding biomolecules are said to be in the experimental studies on the picosecond and femtosecond dynamics of heme proteins. Using techniques he developed he was able to observe the interactions of oxygen, carbon monoxide, and nitric oxide with hemoglobin inside the protein.  相似文献   
943.
Metabolic abnormalities were investigated in 44 stone patients with first time (group 1) and 56 with 2 times stone formation (group 2), and in 25 normal individuals. 24hr urine was analysed spectrophotometrically for oxalate, calcium, magnesium, citrate, uric acid, phosphate and creatinine. Hypocitraturia and hyperoxaluria were the common abnormalities in the stone formers. Stone patients had significantly higher urinary oxalate, calcium and uric acid and lower phosphate than normal individuals. Citrate/calcium and magnesium/calcium ratio were significantly high in normal individuals than stone formers. Patients in group 2 excreted significantly higher urinary calcium and lower citrate that patients in group 1. Citrate/calcium ratio was higher in group 1 than group 2. Hypocitraturia, hyperoxaluria, hypercalciuria and increased citrate/calcium and magnesium/calcium ratio seem to be an essential risk factor for stone formation. Patients with recurrent stone formation could be distinguished from patients with first time stone formation on the basis of urinary calcium and citrate.  相似文献   
944.
945.
We examine engagement in commercial activities (consulting, patenting, and founding) among more than 2200 German and UK life scientists. We test hypotheses that include attributes of individuals, their material and social resources, and perceptions about values and reputation. We find that characteristics reflecting professional security, advantage and productivity are strong predictors for a greater breadth of participation in academic entrepreneurship, but not for all forms of technology transfer that we are able to test. For such academics, science and commerce go hand in hand, as they are best poised to straddle the boundary between industry and academy. We find strong support, however, that scientists perceive the value of patenting differently, and the level of reputational importance placed on scientific compared to commercial achievements matters in shaping commercial involvement.  相似文献   
946.
Heart failure (HF) is a frequent chronic disease in elderly people and represents a major health and economic burden. The accurate diagnosis of HF and the identification of high risk patients is mandatory to select the appropriate therapy and care. HF is associated to cardiac remodeling and inflammation and to the release of neurohormones. If natriuretic peptides remain the biomarkers of choice for the diagnosis and the prognosis of HF, several biomarkers related to cardiac remodeling and inflammation are available for testing and may add valuable information for the risk estimation of HF patients and for the selection of the most appropriated therapy. Furthermore, the quest for new efficient biomarkers of cardiac remodeling and inflammation is still ongoing and new candidates have been identified for a potential use in daily clinical practices. However, before their potential translation to routine parameters several challenges ranging form the analytical validation to the cost-effectiveness estimation should be considered.  相似文献   
947.
948.
Salivary β-glucuronidase activity was studied in 20 healthy subjects without habits and 10 with habits, 38 untreated patients of advanced head and neck cancer and 21 patients after treatment either after surgery or radiation. Salivary β-glucuronidase activity was elevated in untreated cases of head and neck cancer (p<0.001), with a fall in the activity after treatment. The post operative fall in the activity of salivary β-glucuronidase activity was highly significant (p<0.001) as compared to post radiation. This test can be utilized in the diagnosis and also for monitoring the course of the disease.  相似文献   
949.
Curcumin is a natural anti-inflammatory and antioxidant with several potential health benefits. Although it has been examined in several metals toxicity studies, but its role in the protection against copper toxicity has not been investigated. In this study; the detoxification and antioxidant effect of curcumin were examined to determine its prophylactic/therapeutic role experimentally in rats. Forty albino rats were divided into five groups; control, CuSO4 (4 mg/kg body weight), curcumin (80 mg/kg body weight), curcumin post-treatment (CuSO4 for 15 days followed by curcumin for the next 15 days) and curcumin co-treatment (CuSO4 plus curcumin for 30 days). All rats were treated orally by stomach tube for 30 days/once a day. Changes were observed in hepatic marker enzymes such as: aspartate aminotransferase (AST), alanine transaminase-(ALT), alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT), besides the serum total protein, urea and creatinine. Concentration of liver and kidney antioxidants such as: catalase (CAT), superoxide dismutase (SOD), reduced glutathione-(GSH) and malondialdehyde (MDA) were measured. An increased in the activities of liver marker enzymes, urea, creatinine and the MDA contents were detected after exposure to CuSO4. Meanwhile, the activities of serum total protein, hepatic and renal antioxidants were decreased. Changes in all biochemical parameters were alleviated by the post-treatment and co-treatment of curcumin. Our finding suggests that the curcumin showed protective effects on CuSO4-induced hepatotoxicity and nephrotoxicity.  相似文献   
950.
Elevated plasma triglyceride and non-esterified fatty acid concentrations may cause insulin resistance and type 2 diabetes mellitus. Lipoprotein lipase (LPL) is a rate-determining enzyme in lipid metabolism. A variant in the LPL gene has been identified which alters the penultimate amino acid Serine at 447 to a stop codon (S447X), and results in a truncated LPL molecule lacking the C-terminal dipeptide Ser–Gly. The present study was designed to evaluate the frequency of S447X variant in the LPL gene and its effect on the lipid and lipoprotein levels in type 2 diabetic subjects. The genotype frequency distributions of type 2 diabetes patients and controls were in Hardy–Weinberg equilibrium. Comparison of the genotype and allelic frequencies of S447X in subjects with type 2 diabetics compared to controls demonstrated no significant difference. In subjects with type 2 diabetics having hypertriglyceridemia (TG ≥ 150 mg/dl) compared to diabetics with TG level <150 mg/dl, significant difference in genotype frequency was found among these groups, while allelic frequency of X was significantly differed. Logistic regression analysis showed the negative association of LPL S447X variant with TG and VLDL cholesterol, while no association with total cholesterol, HDL cholesterol and LDL cholesterol was found. The lipid levels except for HDL cholesterol were found to be significantly lower in carriers for S447X than wild type in diabetes group. The decreased level of TG and TG rich lipoprotein in subjects with SNP S447X in LPL, predicts anti-atherogenic activity of carriers for S447X variant in general population as well as type 2 diabetic patients.  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