全文获取类型
收费全文 | 65562篇 |
免费 | 5591篇 |
国内免费 | 46篇 |
出版年
2023年 | 214篇 |
2022年 | 433篇 |
2021年 | 1269篇 |
2020年 | 690篇 |
2019年 | 920篇 |
2018年 | 1354篇 |
2017年 | 1073篇 |
2016年 | 1862篇 |
2015年 | 3103篇 |
2014年 | 3450篇 |
2013年 | 3982篇 |
2012年 | 5297篇 |
2011年 | 5098篇 |
2010年 | 3195篇 |
2009年 | 2799篇 |
2008年 | 4065篇 |
2007年 | 3810篇 |
2006年 | 3467篇 |
2005年 | 3123篇 |
2004年 | 3018篇 |
2003年 | 2698篇 |
2002年 | 2305篇 |
2001年 | 1728篇 |
2000年 | 1572篇 |
1999年 | 1265篇 |
1998年 | 592篇 |
1997年 | 511篇 |
1996年 | 417篇 |
1995年 | 410篇 |
1994年 | 314篇 |
1993年 | 310篇 |
1992年 | 644篇 |
1991年 | 518篇 |
1990年 | 478篇 |
1989年 | 480篇 |
1988年 | 405篇 |
1987年 | 393篇 |
1986年 | 320篇 |
1985年 | 329篇 |
1984年 | 272篇 |
1983年 | 227篇 |
1982年 | 196篇 |
1981年 | 167篇 |
1980年 | 162篇 |
1979年 | 223篇 |
1978年 | 197篇 |
1977年 | 179篇 |
1976年 | 172篇 |
1974年 | 197篇 |
1972年 | 158篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
The influence of limb alignment and transfemoral amputation technique on muscle capacity during gait
Ellyn C. Ranz Jason M. Wilken Donald A. Gajewski 《Computer methods in biomechanics and biomedical engineering》2017,20(11):1167-1174
Many factors influence successful outcomes following transfemoral amputation. One factor is surgical technique. In this study, the influence of limb alignment and surgical technique on a muscle’s capacity to generate force was examined using musculoskeletal modeling. Non-amputee and transfemoral amputee models were analyzed while hip adduction, femur length, and reattached muscle wrap position, tension and stabilization technique were systematically varied. With muscle tension preserved, wrap position and femur length had little influence on muscle capacity. However, limb alignment, muscle tension and stabilization technique notably influenced muscle capacity. Overall, myodesis stabilization provided greater muscle balance and function than myoplasty stabilization. 相似文献
113.
114.
Jason C. White 《Arts Education Policy Review》2016,117(1):55-64
While there are many educational and experiential benefits to attending professional higher arts education programs, students who incur excessive student loan debt during their studies may experience unanticipated or poor professional outcomes either over the course of their artistic careers, shortly after the expiration of a loan grace period, or after they can no longer defer payments. To date, little to no research exists on the effects of an excessive student loan debt burden on professional arts careers. To address this gap in the higher arts education literature, and in an effort to facilitate scholarly discussion on the topic, this article identifies concerns, consequences, and potential interventions. 相似文献
115.
116.
The purpose of this review is to provide an overview of the effects of adenovirus and influenza virus infections on obesity in various experimental models. We reviewed studies that were conducted within the past 10 years and were related to virus infection and obesity prevalence. Here, we discuss a different causal relationship between adenovirus and influenza infections with obesity. Adenovirus infection can cause obesity, whereas obesity can be a risk factor for increasing influenza virus infection and increases the risk of morbidity and mortality. The prevalence of obesity due to adenovirus infections may be due to an increase in glucose uptake and reduction in lipolysis caused by an increase in corticosterone secretion. Adenovirus infections may lead to increases in appetite by decreasing norepinephrine and leptin levels and also cause immune dysfunction. The relationship between obesity and influenza virus infection could be summarized by the following features: decreases in memory T-cell functionality and interferon (IFN)-α, IFN-β, and IFN-γ mRNA expression, increases in viral titer and infiltration, and impaired dendritic cell function in obese individuals. Moreover, leptin resistance may play an important role in increasing influenza virus infections in obese individuals. In conclusion, prevention of adenovirus infections could be a good approach for reducing obesity prevalence, and prevention of obesity could reduce influenza virus infections from the point of view of viral infections and obesity. 相似文献
117.
This paper describes a generic algorithm for finding restrictionsites within DNA sequences. The genericity ofthe algorithm is made possible through the use of set theory.Basic elements of DNA sequences, i.e. nucleotides (bases), arerepresented in sets, and DNA sequences, whether specific, ambiguousor even protein-coding, are represented as sequences of thosesets. The set intersection operation demonstrates its abilityto perform pattern-matching correctly on various DNA sequences.The performance analysis showed that the degree of complexityof the pattern matching is reduced from exponential to linear.An example is given to show the actual and potential restrictionsites, derived by the generic algorithm, in the DNA sequencetemplate coding for a synthetic calmodulin.
Received on October 2, 1990; accepted on December 18, 1990 相似文献
118.
The 24-h time budget of a takh harem stallion (Equus ferus przewalskii) pre- and post-reintroduction
Lee Boyd 《Applied animal behaviour science》1998,60(4):291-299
Focal animal sampling was used to determine the 24-h time budget of a takh harem stallion (Equus ferus przewalskii) during the 2 weeks prior to, and the two weeks following, reintroduction into the Hustain Nuruu Steppe Reserve, Mongolia. Both before and after release, the stallion spent approximately 47% of his time grazing, 6% standing, and 5% in recumbent rest. The biggest changes to the time budget after release were a 4-fold increase in the amount of time spent moving, and a 50% decrease in the amount of time spent resting in a standing position. During the middle of the day when the temperatures were hottest, the stallion exhibited less grazing and more standing resting behaviour than in the morning or evening hours. Recumbent rest invariably occurred in the hours before dawn. 相似文献
119.
120.