全文获取类型
收费全文 | 601篇 |
免费 | 72篇 |
国内免费 | 198篇 |
专业分类
871篇 |
出版年
2024年 | 7篇 |
2023年 | 7篇 |
2022年 | 12篇 |
2021年 | 24篇 |
2020年 | 13篇 |
2019年 | 23篇 |
2018年 | 14篇 |
2017年 | 15篇 |
2016年 | 20篇 |
2015年 | 22篇 |
2014年 | 26篇 |
2013年 | 30篇 |
2012年 | 55篇 |
2011年 | 47篇 |
2010年 | 46篇 |
2009年 | 48篇 |
2008年 | 43篇 |
2007年 | 40篇 |
2006年 | 29篇 |
2005年 | 33篇 |
2004年 | 28篇 |
2003年 | 22篇 |
2002年 | 27篇 |
2001年 | 26篇 |
2000年 | 17篇 |
1999年 | 17篇 |
1998年 | 19篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1994年 | 12篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1956年 | 3篇 |
1915年 | 2篇 |
排序方式: 共有871条查询结果,搜索用时 15 毫秒
91.
92.
目的了解临床主要L型致病菌的分布以及对目前常用性变化趋势.方法对2000年7月~2003年7月临床分离的753株药性进行回顾性分析.结果金黄色葡萄球菌、大肠埃希菌、最常见,它们共同对阿米卡星霉素敏感,敏感率达77%以上,共同对罗红霉素、氨苄西林、克林霉素、阿奇霉素耐药,耐药率均在45%以上.结论与我院5年前及10年前L型细菌耐药性对比,抗生素耐药性已发生变迁.掌握L型细菌耐药性的动态,合理使用抗生素. 相似文献
93.
Feng Liu Leona Bessonova Thomas H. Taylor Argyrios Ziogas Frank L. Meyskens Jr. Hoda Anton‐Culver 《Pigment cell & melanoma research》2013,26(1):128-135
Using US SEER17 Registry data, age‐specific melanoma incidence rates were calculated and comparisons were made between males and females. Relative Risk (RR) for males and females in each age group was computed and compared with that from Nordic Cancer Registry data set and to that for non‐melanoma skin cancer (NMSC). For age groups 44 and younger, females showed higher incidence rates, with a peak difference at age 20–24 (RR = 2.01, 95% CI = 1.21–3.33). Males exhibited higher incidence rates after age 44. The same bimodal gender difference was confirmed by the Nordic Cancer Registry data set, but it was not observed for NMSC, which is known to be strongly associated with cumulative exposure to solar UV radiation. We conclude that exposure to solar ultraviolet (UV) radiation is the major causative factor for melanoma at older age (>44 yr), but that other factors may play a role in early onset melanomas, particularly in females. 相似文献
94.
目的探讨胃息肉与幽门螺杆菌(Helicobacter pylori,H.pylori)感染关系。方法对1218例胃息肉同时进行H.pylori检查患者进行回顾性分析,分析胃息肉患者H.pylori感染率、胃息肉部位与H.pylori感染关系、胃息肉病理类型与H.pylori感染关系。结果发现胃息肉Hpylori感染患者532例,Hpylori感染率为43.7%。男性胃息肉患者H.pylori感染率为47.5%(216/455),女性Hpriori感染率感染率为41.4%(316/763)(P〉0.05),年龄〈20岁、20~39岁、40—59岁和≥60岁胃息肉H.priori感染率分别为41.7%、44.7%、41.6%和47.2%(P〉0.05);胃窦胃角息肉H.pylori感染率高于其他部位(胃体、胃底和贲门)(P〈0.05);炎性和增生性胃息肉H.priori感染率高于胃底腺和腺瘤性息肉(P〈0.05)。结论H.pylori感染可能与部分胃息肉发生有一定关系,需要进一步深入研究胃息肉的发生机制。 相似文献
95.
96.
Culver Mvumi Elizabeth Ngadze Diana Marais Elsa S. duToit Jameson Kugara 《Archives Of Phytopathology And Plant Protection》2013,46(7-8):432-444
AbstractThe study investigates the presence and quantity of antimicrobial sinigrin glucosinolates in tomato leaves after spraying them with moringa (Moringa oleifera) leaf extract (MLAE). Moringa concentrates (0.5, 0.75, 1.00 and 1.5?kg?L?1 (w v?1)) were prepared. Distilled water was the control. Sampled tomato leaves were air-dried, freeze-dried and extracted firstly using pure methanol in a hot water bath and then pellet re-extracted using 5?mL of hot aqueous methanol (70% v v?1). An ion exchange column, and sulphatase was used to achieve glucosiodesulphonation. High performance liquid chromatography (HPLC) was employed in the identification and quantitative analysis of the sinigrin glucosinolates. Tomato (Solanum lycopersicum) leaves treated with MLAE revealed highly significant (p?<?.001) content of sinigrin glucosinolates. The sinigrin standard and the desulphated sinigrin glucosinolates had a 7?s retention time difference; 5?kg?L?1 (w v?1) resulted in a superior amount of sinigrin in tomato leaves as compared to all the other MLAE concentrations. The study reveals that spraying MLAE on putatively diseased tomato leaves donates specific quantifiable glucosinolates like sinigrin, which may be involved in defense against tomato diseases and, hence, recommends use of 5?kg?L?1 (w v?1) for the highest sinigrin defense tag. 相似文献
97.
Peter Kozel Tanja Pipan Stefano Mammola David C. Culver Tone Novak 《Invertebrate Biology》2019,138(3)
Troglobionts are organisms that are specialized for living in a subterranean environment. These organisms reside prevalently in the deepest zones of caves and in shallow subterranean habitats, and complete their entire life cycles therein. Because troglobionts in most caves depend on organic matter resources from the surface, we hypothesized that they would also select the sections of caves nearest the surface, as long as environmental conditions were favorable. Over 1 year, we analyzed, in monthly intervals, the annual distributional dynamics of a subterranean community consisting of 17 troglobiont species, in relation to multiple environmental factors. Cumulative standardized annual species richness and diversity clearly indicated the existence of two ecotones within the cave: between soil and shallow subterranean habitats, inhabited by soil and shallow troglobionts; and between the transition and inner cave zones, where the spatial niches of shallow and deep troglobionts overlap. The mean standardized annual species richness and diversity showed inverse relationships, but both contributed to a better insight into the dynamics of subterranean fauna. Regression analyses revealed that temperatures in the range 7–10°C, high moisture content of substrate, large cross section of the cave, and high pH of substrate were the most important ecological drivers governing the spatiotemporal dynamics of troglobionts. Overall, this study shows general trends in the annual distributional dynamics of troglobionts in shallow caves and reveals that the distribution patterns of troglobionts within subterranean habitats may be more complex than commonly assumed. 相似文献
98.
Swanson David L. King Marisa O. Culver William Zhang Yufeng 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2019,189(3-4):451-462
Journal of Comparative Physiology B - Small birds in cold climates may show within-winter metabolic flexibility to match metabolic capacities to prevailing weather conditions. This flexibility may... 相似文献
99.
Lung volume and pleural pressure effects on ventricular function 总被引:1,自引:0,他引:1