全文获取类型
收费全文 | 38309篇 |
免费 | 3875篇 |
国内免费 | 3494篇 |
出版年
2024年 | 24篇 |
2023年 | 429篇 |
2022年 | 597篇 |
2021年 | 1479篇 |
2020年 | 1374篇 |
2019年 | 1653篇 |
2018年 | 1670篇 |
2017年 | 1260篇 |
2016年 | 1697篇 |
2015年 | 2626篇 |
2014年 | 2956篇 |
2013年 | 3080篇 |
2012年 | 3686篇 |
2011年 | 3428篇 |
2010年 | 2152篇 |
2009年 | 1972篇 |
2008年 | 2277篇 |
2007年 | 2041篇 |
2006年 | 1838篇 |
2005年 | 1549篇 |
2004年 | 1483篇 |
2003年 | 1258篇 |
2002年 | 1048篇 |
2001年 | 683篇 |
2000年 | 539篇 |
1999年 | 509篇 |
1998年 | 341篇 |
1997年 | 307篇 |
1996年 | 276篇 |
1995年 | 241篇 |
1994年 | 201篇 |
1993年 | 135篇 |
1992年 | 149篇 |
1991年 | 117篇 |
1990年 | 124篇 |
1989年 | 102篇 |
1988年 | 70篇 |
1987年 | 67篇 |
1986年 | 42篇 |
1985年 | 36篇 |
1984年 | 39篇 |
1983年 | 24篇 |
1982年 | 30篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1967年 | 3篇 |
1950年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
Bong Jin Kim Kyung Seob Song Hyun-Hee Kong Hee-Jae Cha Meesun Ock 《The Korean journal of parasitology》2014,52(1):85-87
We encountered a patient with heavy Hymenolepis nana infection. The patient was a 44-year-old Korean man who had suffered from chronic hepatitis (type B) for 15 years. A large number of H. nana adult worms were found during colonoscopy that was performed as a part of routine health screening. The parasites were scattered throughout the colon, as well as in the terminal ileum, although the patient was immunocompetent. Based on this study, colonoscopy may be helpful for diagnosis of asymptomatic H. nana infections. 相似文献
2.
An advanced electro-active dry adhesive,which was composed of a mushroom-shaped fibrillar dry adhesive array actuated by an Ionic Polymer Metal Composite (IPMC) artificial muscle reinforced with nitrogen-doped carbon nanocages (NCNCs),was developed to imitate the actuation of a gecko's toe.The properties of the NCNC-reinforced Nafion membrane,the electromechanical properties of the NCNC-reinforced IPMC,and the related electro-active adhesion ability were investigated.The NCNCs were uniformly dispersed in the 0.1 wt% NCNC/Nafion membrane,and there was a seamless connection with no clear interface between the dry adhesive and the IPMC.Our 0.1 wt% NCNC/Nafion-IPMC actuator shows a displacement and force that are 1.6-2 times higher than those of the recast Nafion-IPMC.This is due to the increased water uptake (25.39%) and tensile strength (24.5 MPa) of the specific 3D hollow NCNC-reinforced Nafion membrane,as well as interactions between the NCNCs and the sulfonated groups of the Nafion.The NCNC/Nafion-IPMC was used to effectively actuate the mushroom-shaped dry adhesive.The normal adhesion forces were 7.85 mN,12.1 mN,and 51.7 mN at sinusoidal voltages of 1.5 V,2.5 V,and 3.5 V,respectively,at 0.1 Hz.Under the bionic leg trail,the normal and shear forces were approximately 713.5 mN (159 mN·cm-2) and 1256.6 mN (279 mN·cm-2),respectively,which satisfy the required adhesion.This new electro-active dry adhesive can be applied for active,distributed actuation and flexible grip in robots. 相似文献
3.
4.
5.
6.
针对抗虫耐除草剂大豆转基因品系MON89788,从转基因植物基因组DNA的提取、核酸模板的质量和浓度控制、引物探针的筛选、PCR反应过程的建立等方面建立了一套完整的转基因大豆芯片式dPCR定量检测方法。本实验也对该方法的重复性和定量检测限进行考察。10组5%转基因品系大豆MON89788样品定量重复性RSD在1.17%-9.97%之间,均满足国际上转基因定量结果RSD小于25%的要求。用该方法对转基因含量为5%、1%、0.1%的大豆MON89788进行定量检测,其定量结果为5.20%、0.94%和0.11%,RSD分别为6.2%、3.6%和15.2%。该检测方法的定量限达到0.1%,能满足欧盟对转基因定量标识0.9%的要求。将本实验建立的方法用于转基因大豆的定量检测,能为规范我国转基因监管工作的实施提供强有力的技术支撑。 相似文献
7.
8.
The value of harmful algal bloom predictions to the nearshore commercial shellfish fishery in the Gulf of Maine 总被引:1,自引:0,他引:1
In this study, we develop a framework for measuring the value of harmful algal bloom (HAB) predictions. The framework captures the effects of both private and public responses to HABs. Using data from the New England nearshore commercial shellfish fishery and impact estimates for a large-scale HAB event in 2005, we illustrate how the potential value of HAB forecasts may be estimated. The results of our study suggest that the long-term value of a HAB prediction and tracking system for the Gulf of Maine is sensitive to the frequency of HAB events, the accuracy of predictions, the choice of HAB impact measures, and the effectiveness of public and private responses. 相似文献
9.
Oily water treatment has attracted the attention of many researchers.The development of effective and cheap oil/water separation materials is urgent for treating this problem.Herein,inspired by superhydrophobic typical plant leaves such as lotus,red rose and marigold,superhydrophobic and superoleophilic copper mesh was fabricated by etching and then surface modification with 1-dodecanethiol (HS(CH2)11CH3).A rough silver layer is formed on the mesh surface after immersion.The obtained mesh surface exhibits superhydrophobicity and superoleophilicity and the static water contact angle was 153° ± 3°.In addition,the as-prepared copper mesh shows self-cleaning character with water and chemical stability.The as-prepared copper foam can easily remove the organic solvents either on water or underwater.We demonstrate that by using the as-prepared mesh,oils can be absorbed and separated,and that high separation efficiencies of larger than 92% are retained for various oils.Thus,such superhydrophobic and superoleophilic copper mesh is a very promising material for the application of oil spill cleanup and industrial oily wastewater treatment. 相似文献
10.
Bing Wen Xi Peng Li Qing Chun Liu Kai Chen Tao Teng Jun Xie 《Systematic parasitology》2017,94(1):73-80
Actinosporean infection of oligochaetes living in the mud of a commercial gibel carp pond with myxosporean disease was studied. Six actinospore types were detected exclusively from the oligochaete Branchiura sowerbyi Beddard with very high prevalence (18%). Five out of the six types were identified as the same actinosporeans described in previous reports, the sixth actinosporean was identified as a new Neoactinomyxum type and described here based on morphological and molecular characterisation. Spore body of the actinospore was globular, much smaller than caudal processes. Three caudal processes were disc-like in apical view, hemispherical in side view, closer together and encircling the spore body. The number of sporoplasm cells was detected as eight in one specimen. The new actinosporean markedly differed from other Neoactinomyxum types in literature having much bigger caudal processes. DNA sequence analyses further confirmed the morphological identification, and revealed the actinosporean described here (KU641392) possessed less than 94% sequence similarity with myxozoans available in the GenBank database. 相似文献