全文获取类型
收费全文 | 9051篇 |
免费 | 708篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 88篇 |
儿科学 | 261篇 |
妇产科学 | 79篇 |
基础医学 | 1153篇 |
口腔科学 | 208篇 |
临床医学 | 1031篇 |
内科学 | 1997篇 |
皮肤病学 | 79篇 |
神经病学 | 838篇 |
特种医学 | 309篇 |
外科学 | 1470篇 |
综合类 | 117篇 |
一般理论 | 8篇 |
预防医学 | 763篇 |
眼科学 | 180篇 |
药学 | 688篇 |
中国医学 | 3篇 |
肿瘤学 | 522篇 |
出版年
2023年 | 58篇 |
2022年 | 88篇 |
2021年 | 262篇 |
2020年 | 127篇 |
2019年 | 230篇 |
2018年 | 282篇 |
2017年 | 180篇 |
2016年 | 205篇 |
2015年 | 202篇 |
2014年 | 347篇 |
2013年 | 453篇 |
2012年 | 664篇 |
2011年 | 714篇 |
2010年 | 391篇 |
2009年 | 366篇 |
2008年 | 595篇 |
2007年 | 600篇 |
2006年 | 565篇 |
2005年 | 607篇 |
2004年 | 533篇 |
2003年 | 507篇 |
2002年 | 456篇 |
2001年 | 99篇 |
2000年 | 93篇 |
1999年 | 85篇 |
1998年 | 101篇 |
1997年 | 79篇 |
1996年 | 62篇 |
1995年 | 52篇 |
1994年 | 44篇 |
1993年 | 42篇 |
1992年 | 42篇 |
1991年 | 41篇 |
1990年 | 55篇 |
1989年 | 39篇 |
1988年 | 27篇 |
1987年 | 29篇 |
1986年 | 32篇 |
1985年 | 31篇 |
1984年 | 41篇 |
1983年 | 36篇 |
1982年 | 26篇 |
1981年 | 31篇 |
1980年 | 26篇 |
1979年 | 29篇 |
1978年 | 18篇 |
1977年 | 23篇 |
1976年 | 19篇 |
1975年 | 12篇 |
1974年 | 17篇 |
排序方式: 共有9794条查询结果,搜索用时 15 毫秒
101.
102.
Clinical cerebral microdialysis: a methodological study 总被引:21,自引:0,他引:21
Hutchinson PJ O'Connell MT Al-Rawi PG Maskell LB Kett-White R Gupta AK Richards HK Hutchinson DB Kirkpatrick PJ Pickard JD 《Journal of neurosurgery》2000,93(1):37-43
OBJECT: Clinical microdialysis enables monitoring of the cerebral extracellular chemistry of neurosurgical patients. Introduction of the technique into different hospitals' neurosurgical units has resulted in variations in the method of application. There are several variables to be considered, including length of the catheter membrane, type of perfusion fluid, flow rate of perfusion fluid, and on-line compared with delayed analysis of samples. The objects of this study were as follows: 1) to determine the effects of varying catheter characteristics on substance concentration; 2) to determine the relative recovery and true extracellular concentration by varying the flow rate and extrapolating to zero flow; and 3) to compare substance concentration obtained using a bedside enzyme analyzer with that of off-line high-performance liquid chromatography (HPLC). METHODS: A specially designed bolt was used to conduct two adjacent microdialysis catheters into the frontal cortex of patients with head injury or poor-grade subarachnoid hemorrhage who were receiving ventilation. One reference catheter (10-mm membrane, perfused with Ringer's solution at 0.3 microl/minute) was constant for all studies. The other catheter was varied in terms of membrane length (10 mm or 30 mm), perfusion fluid (Ringer's solution or normal saline), and flow rate (0.1-1.5 microl/minute). The effect of freezing the samples on substance concentration was established by on-line analysis and then repeated analysis after storage at -70 degrees C for 3 months. Samples assayed with the bedside enzyme analyzer were reassessed using HPLC for the determination of glutamate concentrations. CONCLUSIONS: Two adjacent microdialysis catheters that were identical in membrane length, perfusion fluid, and flow rate showed equivalent results. Variations in perfusion fluid and freezing and thawing of samples did not result in differences in substance concentration. Catheter length had a significant impact on substance recovery. Variations in flow rate enabled the relative recovery to be calculated using a modification of the extrapolation-to-zero-flow method. The recovery was approximately 70% at 0.3 microl/minute and 30% at 1 microl/minute (10-mm membrane) for all analytes. Glutamate results obtained with the enzyme analyzer showed good correlation with those from HPLC. 相似文献
103.
During drug discovery, it is important to optimise the affinity for the biomolecular target and also the properties of molecules that influence absorption, distribution, metabolism, excretion, and toxicity (ADMET). The goal is to improve the properties of a lead compound and select highly ‘developable’ candidates. Efficient pharmaceutical property profiling operations are now run in parallel to potency screening during lead optimization and provide data for compound prioritization and for the selection of compounds for in vivo studies. The main components of a profiling strategy suitable for early discovery are the measurement of selected physicochemical properties together with in vitro screening for metabolic stability. In addition, enzyme or cellular assays may be deployed for investigation of cellular permeability (including active and passive transport), plasma protein binding, toxicity, and the potential for drug-drug interactions. The four principal physicochemical parameters measured are lipophilicity, dissociation constant, permeability through artificial membranes, and aqueous solubility. An objective of property-based design is the identification of structure property relationships for ADMET that can suggest structural modifications that will also promote or retain high affinity for the biomolecular target. Sometimes this is not possible and new lead molecules may need to be identified to provide new starting points. A sub-optimal in vitro profile may be acceptable as long as there is a reasonable probability of achieving an adequate in vivo profile for clinical studies. In these cases, the application of composite models that can relate in vitro to in vivo behavior is important. Full ‘physiologically based pharmacokinetic’ (PBPK) models can be used; however, there are also simpler approaches available that may be adequate and more easily applied for ranking compounds within a series. Reliable in vitro—in vivo correlation is still very difficult because of the multiplicity of mechanisms involved. For the future, there is a need to develop better criteria for making mechanistically based classifications to develop differentiated models that are appropriate for different types of compound. It is also difficult to correct models for non-specific binding of drugs to membranes and proteins and we need better lipophilicity measures for accurately estimating the affinity of drugs for tissues. PBPK modeling leads to the exciting concept of the ‘virtual human’; however, PBPK models suitable for drug discovery applications are still in their infancy and it will be some time before their promise is fulfilled. 相似文献
104.
Menglin Ma Abhijit Gurjar James R. Theoret Jorge P. Garcia Juliann Beingesser John C. Freedman Derek J. Fisher Bruce A. McClane Francisco A. Uzal 《Infection and immunity》2014,82(7):2958-2970
The ability of Clostridium perfringens type C to cause human enteritis necroticans (EN) is attributed to beta toxin (CPB). However, many EN strains also express C. perfringens enterotoxin (CPE), suggesting that CPE could be another contributor to EN. Supporting this possibility, lysate supernatants from modified Duncan-Strong sporulation (MDS) medium cultures of three CPE-positive type C EN strains caused enteropathogenic effects in rabbit small intestinal loops, which is significant since CPE is produced only during sporulation and since C. perfringens can sporulate in the intestines. Consequently, CPE and CPB contributions to the enteropathogenic effects of MDS lysate supernatants of CPE-positive type C EN strain CN3758 were evaluated using isogenic cpb and cpe null mutants. While supernatants of wild-type CN3758 MDS lysates induced significant hemorrhagic lesions and luminal fluid accumulation, MDS lysate supernatants of the cpb and cpe mutants caused neither significant damage nor fluid accumulation. This attenuation was attributable to inactivating these toxin genes since complementing the cpe mutant or reversing the cpb mutation restored the enteropathogenic effects of MDS lysate supernatants. Confirming that both CPB and CPE are needed for the enteropathogenic effects of CN3758 MDS lysate supernatants, purified CPB and CPE at the same concentrations found in CN3758 MDS lysates also acted together synergistically in rabbit small intestinal loops; however, only higher doses of either purified toxin independently caused enteropathogenic effects. These findings provide the first evidence for potential synergistic toxin interactions during C. perfringens intestinal infections and support a possible role for CPE, as well as CPB, in some EN cases. 相似文献
105.
106.
107.
108.
109.
Derek Milne Orli Gorenski Colin Westerman Caroline Leek Dominique Keegan 《American journal of psychiatric rehabilitation》2013,16(2):259-281
Abstract Staff training is a necessary component in psychiatric rehabilitation programs, providing the basis of a skilled and integrated workforce. However, it has been found repeatedly that training is not sufficient to result in an improved quality of care for clients. What is required to make training effective is a parallel emphasis upon the organizational context within which these trained skills are to be applied. The present paper provides a review of the contextual factors that contribute to training effectiveness. A case study of the transfer of staff training (N=10) in psychiatric rehabilitation skills illustrates several of these factors. Conclusions are drawn about the factors that contribute to successful transfer of training, and about future research requirements. 相似文献
110.
Derek G. Steward 《The Physician and sportsmedicine》2013,41(3):171-174
A former world-class athlete found that exercise did not protect him from coronary artery disease, and he speculates about the reasons. 相似文献