全文获取类型
收费全文 | 11493篇 |
免费 | 781篇 |
专业分类
12274篇 |
出版年
2023年 | 64篇 |
2022年 | 81篇 |
2021年 | 258篇 |
2020年 | 161篇 |
2019年 | 209篇 |
2018年 | 321篇 |
2017年 | 284篇 |
2016年 | 433篇 |
2015年 | 633篇 |
2014年 | 660篇 |
2013年 | 862篇 |
2012年 | 1006篇 |
2011年 | 880篇 |
2010年 | 566篇 |
2009年 | 485篇 |
2008年 | 637篇 |
2007年 | 631篇 |
2006年 | 532篇 |
2005年 | 447篇 |
2004年 | 518篇 |
2003年 | 421篇 |
2002年 | 443篇 |
2001年 | 223篇 |
2000年 | 188篇 |
1999年 | 156篇 |
1998年 | 112篇 |
1997年 | 81篇 |
1996年 | 67篇 |
1995年 | 57篇 |
1994年 | 60篇 |
1993年 | 42篇 |
1992年 | 106篇 |
1991年 | 74篇 |
1990年 | 63篇 |
1989年 | 52篇 |
1988年 | 48篇 |
1987年 | 44篇 |
1986年 | 41篇 |
1985年 | 45篇 |
1984年 | 38篇 |
1983年 | 29篇 |
1982年 | 23篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 12篇 |
1978年 | 15篇 |
1975年 | 12篇 |
1974年 | 16篇 |
1973年 | 16篇 |
1972年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The relations between the saccus lacrimalis and different portions of the musculus orbicularis oculi were studied in orbital regions of human fetuses sectioned into numbered series. No insertions of the pars lacrimalis or Horner's muscle on the saccus were found. These muscular fibres pass along the dorsal wall of the saccus and are separated from it by the reflex tendon of the ligamentum palpebrale mediale. The only muscular fibres that insert on the saccus are those that approach the anterior face of the saccus and the fornix. The fibres that insert on the anterior face proceed from the deep bundles of the pars preseptalis of the lower eyelids, and those that insert on the fornix derive from the deep bundles of the pars preseptalis of the upper eyelid. 相似文献
2.
E. Molina Grima J. A. Sánchez Pérez F. García Camacho F. G. Acién Fernández J. M. Fernández Sevilla F. Valdés Sanz 《Biotechnology letters》1994,16(10):1035-1040
Summary Eicosapentaenoic acid (EPA) volumetric productivity from an outdoor chemostat culture ofPhaeodactylum tricornutum UTEX 640 in a 50-l tubular photobioreactor varies with dilution rate, reaching a maximum of 47.8 mg l–1 d–1 at D=0.36 d–1. Continuous culture at high dilution rates' is proposed as the most adequate operating mode to maximize polyunsaturated fatty acid production. 相似文献
3.
4.
5.
6.
Hermógenes Fernández-Marín David R. Nash Sarah Higginbotham Catalina Estrada Jelle S. van Zweden Patrizia d'Ettorre William T. Wcislo Jacobus J. Boomsma 《Proceedings. Biological sciences / The Royal Society》2015,282(1807)
Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors'' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants'' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens. 相似文献
7.
Léniz A. Portillo M. P. Fernández-Quintela Alfredo Macarulla M. T. Sarasua-Miranda A. del Hoyo M. Díez-López I. 《Journal of physiology and biochemistry》2019,75(3):311-319
Journal of Physiology and Biochemistry - Infants born small for gestational age (SGA) are at increased risk of perinatal morbidity, persistent short stature, and metabolic alterations in later... 相似文献
8.
Marta Tejera-Alhambra Armanda Casrouge Clara de Andrés Ansgar Seyfferth Rocío Ramos-Medina Bárbara Alonso Janet Vega Lidia Fernández-Paredes Matthew L. Albert Silvia Sánchez-Ramón 《PloS one》2015,10(6)
Multiple sclerosis, the most common cause of neurological disability in young population after trauma, represents a significant public health burden. Current challenges associated with management of multiple sclerosis (MS) patients stem from the lack of biomarkers that might enable stratification of the different clinical forms of MS and thus prompt treatment for those patients with progressive MS, for whom there is currently no therapy available. In the present work we analyzed a set of thirty different plasma cytokines, chemokines and growth factors present in circulation of 129 MS patients with different clinical forms (relapsing remitting, secondary progressive and primary progressive MS) and 53 healthy controls, across two independent cohorts. The set of plasma analytes was quantified with Luminex xMAP technology and their predictive power regarding clinical outcome was evaluated both individually using ROC curves and in combination using logistic regression analysis. Our results from two independent cohorts of MS patients demonstrate that the divergent clinical and histology-based MS forms are associated with distinct profiles of circulating plasma protein biomarkers, with distinct signatures being composed of chemokines and growth/angiogenic factors. With this work, we propose that an evaluation of a set of 4 circulating biomarkers (HGF, Eotaxin/CCL11, EGF and MIP-1β/CCL4) in MS patients might serve as an effective tool in the diagnosis and more personalized therapeutic targeting of MS patients. 相似文献
9.
10.