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   95810篇
  免费   480篇
  国内免费   813篇
  2022年   22篇
  2021年   35篇
  2020年   24篇
  2019年   27篇
  2018年   11872篇
  2017年   10693篇
  2016年   7485篇
  2015年   657篇
  2014年   365篇
  2013年   431篇
  2012年   4338篇
  2011年   12950篇
  2010年   12073篇
  2009年   8277篇
  2008年   9887篇
  2007年   11463篇
  2006年   368篇
  2005年   608篇
  2004年   1053篇
  2003年   1128篇
  2002年   876篇
  2001年   372篇
  2000年   256篇
  1999年   108篇
  1998年   39篇
  1997年   47篇
  1996年   39篇
  1995年   22篇
  1994年   31篇
  1993年   54篇
  1992年   71篇
  1991年   94篇
  1990年   63篇
  1989年   67篇
  1988年   68篇
  1987年   62篇
  1986年   47篇
  1985年   37篇
  1984年   34篇
  1983年   57篇
  1982年   30篇
  1981年   23篇
  1979年   33篇
  1977年   27篇
  1973年   18篇
  1972年   260篇
  1971年   297篇
  1970年   29篇
  1965年   18篇
  1962年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
172.
Statins effectively lower low-density lipoprotein-cholesterol (LDL-C) and reduce cardiovascular risk in people with dyslipidemia and cardiometabolic diseases such as Metabolic syndrome (MetS) or type 2 diabetes (T2D). In addition to elevated levels of LDL-C, people with these conditions often have other lipid-related risk factors, such as high levels of triglycerides, low levels of high-density lipoprotein-cholesterol (HDL-C), and a preponderance of highly atherogenic, small, dense low-density lipoprotein particles. The optimal management of dyslipidemia in people with MetS or T2D should therefore address each of these risk factors in addition to LDL-C. Although statins typically have similar effects on LDL-C levels, differences in chemical structure and pharmacokinetic profile can lead to variations in pleiotropic effects, adverse event profiles and drug-drug interactions. The choice of statin should therefore depend on the characteristics and needs of the individual patient. Compared with other statins, pitavastatin has distinct pharmacological features that translate into a broad range of actions on both apolipoprotein-B-containing and apolipoprotein-A-containing lipoproteins. Studies show that pitavastatin 1 to 4 mg is well tolerated and significantly improves LDL-C and triglyceride levels to a similar or greater degree than comparable doses of atorvastatin, simvastatin or pravastatin, irrespective of diabetic status. Moreover, whereas most statins show inconsistent effects on HDL-C levels, pitavastatin-treated patients routinely experience clinically significant elevations in HDL-C that are maintained and even increased over the long term. In addition to increasing high-density lipoprotein quantity, pitavastatin appears to improve high-density lipoprotein function and to slow the progression of atherosclerotic plaques by modifying high-density lipoprotein-related inflammation and oxidation, both of which are common in patients with MetS and T2D. When choosing a statin, it is important to note that patients with MetS have an increased risk of developing T2D and that some statins can exacerbate this risk via adverse effects on glucose regulation. Unlike many statins, pitavastatin appears to have a neutral and even beneficial effect on glucose regulation, making it a useful treatment option in this high-risk group of patients. Together with pitavastatin’s beneficial effects on the cardiometabolic lipid profile and its low potential for drug-drug interactions, this suggests that pitavastatin might be a useful lipid-lowering option for people with cardiometabolic disease.  相似文献   
173.
Wastewaters are a rich source of nutrients for microorganisms. However, if left unattended the biodegradation may lead to severe environmental hazards. The wastewaters can thus be utilized for the production of various value added products including bioenergy (H2 and CH4). A number of studies have reported utilization of various wastewaters for energy production. Depending on the nature of the wastewater, different reactor configurations, wastewater and inoculum pretreatments, co-substrate utilizations along with other process parameters have been studied for efficient product formation. Only a few studies have reported sequential utilization of wastewaters for H2 and CH4 production despite its huge potential for complete waste degradation.  相似文献   
174.
It has been shown that both IAA and ethylene application inhibit flower induction in the short-day plant Pharbitis nil. However application of IAA has elevated ethylene production in this plant, as well. Strong enhancement of ethylene production is also correlated with the night-break effect, which completely inhibits flowering. In order to determine what the role of IAA and ethylene is in the photoperiodic flower induction in Pharbitis nil, we measured changes in their levels during inductive and non-inductive photoperiods, and the effects of ethylene biosynthesis and action inhibitors on inhibition of flowering by IAA. Our results have shown that the inhibitory effect of IAA on Pharbitis nil flowering is not physiological but is connected with its effect on ethylene biosynthesis.  相似文献   
175.
Software for fitting of NMR spectra in MATLAB is presented. Spectra are fitted in the frequency domain, using Fourier transformed lineshapes, which are derived using the experimental acquisition and processing parameters. This yields more accurate fits compared to common fitting methods that use Lorentzian or Gaussian functions. Furthermore, a very time-efficient algorithm for calculating and fitting spectra has been developed. The software also performs initial peak picking, followed by subsequent fitting and refinement of the peak list, by iteratively adding and removing peaks to improve the overall fit. Estimation of error on fitting parameters is performed using a Monte-Carlo approach. Many fitting options allow the software to be flexible enough for a wide array of applications, while still being straightforward to set up with minimal user input.  相似文献   
176.
177.
178.
A patent foramen ovale is a common intracardiac finding that is located between the left and right atrium. It can cause right-to-left shunting and has a high prevalence in patients who suffer a cryptogenic stroke. Earlier trials did not show superiority of percutaneous patent foramen ovale closure with standard medical therapy over standard medical therapy alone in the treatment of cryptogenic stroke. Interestingly, several meta-analyses show positive results regarding closure, suggesting underpowering of the individual trials. Recently, two large prospective trials and one long-term follow-up study showed benefit of percutaneous closure over standard medical therapy in treatment of cryptogenic stroke. A larger right-to-left shunt or the presence of an atrial septal aneurysm were predictors for a recurrent event. Therefore, percutaneous patent foramen ovale closure after cryptogenic stroke should be recommended over antiplatelet therapy alone in patients younger than 55 years of age with a high-risk patent foramen ovale.  相似文献   
179.
Molecular Genetics and Genomics - Ribosomal protein S1 from a newly isolated Escherichia coli mutant has a molecular weight of about 54,000 which is smaller than the wild type S1 (M.W. 65,000). The...  相似文献   
180.
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