全文获取类型
收费全文 | 42614篇 |
免费 | 3033篇 |
国内免费 | 5729篇 |
专业分类
51376篇 |
出版年
2024年 | 227篇 |
2023年 | 935篇 |
2022年 | 1205篇 |
2021年 | 1411篇 |
2020年 | 1430篇 |
2019年 | 2004篇 |
2018年 | 1613篇 |
2017年 | 1459篇 |
2016年 | 1368篇 |
2015年 | 1323篇 |
2014年 | 2138篇 |
2013年 | 3086篇 |
2012年 | 1715篇 |
2011年 | 2015篇 |
2010年 | 1549篇 |
2009年 | 2022篇 |
2008年 | 1991篇 |
2007年 | 2186篇 |
2006年 | 1930篇 |
2005年 | 1761篇 |
2004年 | 1563篇 |
2003年 | 1417篇 |
2002年 | 1286篇 |
2001年 | 1015篇 |
2000年 | 898篇 |
1999年 | 821篇 |
1998年 | 802篇 |
1997年 | 703篇 |
1996年 | 598篇 |
1995年 | 570篇 |
1994年 | 546篇 |
1993年 | 498篇 |
1992年 | 487篇 |
1991年 | 466篇 |
1990年 | 355篇 |
1989年 | 347篇 |
1988年 | 354篇 |
1987年 | 282篇 |
1986年 | 316篇 |
1985年 | 541篇 |
1984年 | 637篇 |
1983年 | 355篇 |
1982年 | 510篇 |
1981年 | 496篇 |
1980年 | 428篇 |
1979年 | 332篇 |
1978年 | 241篇 |
1977年 | 253篇 |
1976年 | 217篇 |
1973年 | 188篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Janitha A. Liyanage David M. Taylor David R. Williams 《Chemical Speciation and Bioavailability》2013,25(2):73-75
ABSTRACTA method has been developed for impregnating alginate-based wound dressings with trace elements required for wound healing and for quantifying the transfer from these dressing to wound fluid (for which a substitute—blood serum—was used in these experiments). Under ideal conditions, up to 85% can be carried across from the tow to the wound fluid. 相似文献
112.
Olga A. Grishina Irina V. Kirillova Olga E. Glukhova 《Computer methods in biomechanics and biomedical engineering》2016,19(3):297-305
The biomechanical model of human coronary arteries was modified for improving the quality of diagnosis and surgical treatment for coronary heart disease. The problem of hemodynamics in the left coronary artery with multivessel bed disease – 45% stenosis of the anterior descending branch and 75% stenosis of the circumflex branch – was particularly considered. Numerical simulation of the coronary arterial bypass of the main trunk was carried out to estimate the functional condition of the coronary arteries after restoring myocardial blood supply by surgery. 相似文献
113.
Cynthia Nafula Wakhungu Isaiah Masinde Tabu O. Daniel Otaye Wafula Victor Wasike 《Archives Of Phytopathology And Plant Protection》2017,50(7-8):398-414
A study was carried out to determine Fusarium wilt distribution in Bambara nut farmers’ fields and its management using farm yard manure (FYM). Four villages in Busia County were purposively sampled for the study. The data generated were subjected to analysis of variance and treatment means separated by least significant difference test. Fusarium wilt incidence in the fields ranged from 14.63 to 43.56%. In the greenhouse, FYM reduced the disease incidence by 10.2% and severity by 9.5% on the black landrace and 1.9 and 12.8%, respectively, on the red landrace. In the field, FYM reduced disease incidence by 9.1% and severity by 6.9% on the black landrace and 10.4 and 10.4%, respectively, on the red landrace. Farm yard manure had the lowest area under disease progress curve irrespective of the landrace. The study confirmed the presence of the pathogen in the fields and the ability to manage the disease using FYM. 相似文献
114.
115.
116.
For flexible peptides, nuclear Overhauser Effects (NOE) experiments do not provide enough information to ensure a correct definition of their solution structure. The use of distance constraints, derived from the knowledge of proton chemical shifts, is developed to restrict the number of possible conformations. In the case of flexible molecules, randomization appears as an important factor of the correct estimation of the chemical shifts from the 3D structure. The refinement of the solution structure of the highly flexible AVP-like parallel dimer is described to illustrate this process. 相似文献
117.
Prof. D. S. Bhoj 《Biometrical journal. Biometrische Zeitschrift》1987,29(5):589-594
A statistic is proposed for testing the hypothesis of equality of the means of a bivariate normal distribution with unknown common variance and correlation coefficient when observations are missing on one of the variates. Expressions for the second and fourth central moments of the statistic are obtained. These moments are used to approximate the distribution of the statistic by a Student's t distribution under the null hypothesis. The powers of the test are computed and compared with those of the conventional paired t and the other known statistics. 相似文献
118.
Dinesh S. Bhoj 《Biometrical journal. Biometrische Zeitschrift》1989,31(3):279-288
Two statistics are proposed for testing the hypothesis of equality of the means of a bivariate normal distribution with unknown common variance and correlation coefficient when observations are missing on both variates. One of the statistics reduces to the one proposed by Bhoj (1978, 1984) when the unpaired observations on the variates are equal. The distributions of the statistics are approximated by well known distributions under the null hypothesis. The empirical powers of the tests are computed and compared with those of some known statistics. The comparison supports the use of one of the statistics proposed in this paper. 相似文献
119.
Dennis T. Villareal Caroline M. Apovian Robert F. Kushner Samuel Klein 《Obesity (Silver Spring, Md.)》2005,13(11):1849-1863
Obesity causes serious medical complications and impairs quality of life. Moreover, in older persons, obesity can exacerbate the age‐related decline in physical function and lead to frailty. However, appropriate treatment for obesity in older persons is controversial because of the reduction in relative health risks associated with increasing body mass index and the concern that weight loss could have potential harmful effects in the older population. This joint position statement from the American Society for Nutrition and NAASO, The Obesity Society reviews the clinical issues related to obesity in older persons and provides health professionals with appropriate weight‐management guidelines for obese older patients. The current data show that weight‐loss therapy improves physical function, quality of life, and the medical complications associated with obesity in older persons. Therefore, weight‐loss therapy that minimizes muscle and bone losses is recommended for older persons who are obese and who have functional impairments or medical complications that can benefit from weight loss. 相似文献
120.
A number of methods of construction of partially balanced incomplete block designs with nested rows and columns are developed and new balanced incomplete block designs with nested rows and columns are obtained as a by-product. 相似文献