全文获取类型
收费全文 | 123697篇 |
免费 | 10012篇 |
国内免费 | 5002篇 |
专业分类
138711篇 |
出版年
2023年 | 1108篇 |
2022年 | 2570篇 |
2021年 | 4463篇 |
2020年 | 2930篇 |
2019年 | 3540篇 |
2018年 | 3707篇 |
2017年 | 2817篇 |
2016年 | 3955篇 |
2015年 | 5598篇 |
2014年 | 6566篇 |
2013年 | 7252篇 |
2012年 | 8461篇 |
2011年 | 7691篇 |
2010年 | 4720篇 |
2009年 | 4303篇 |
2008年 | 5094篇 |
2007年 | 4739篇 |
2006年 | 4313篇 |
2005年 | 3604篇 |
2004年 | 3131篇 |
2003年 | 2788篇 |
2002年 | 2534篇 |
2001年 | 3989篇 |
2000年 | 3723篇 |
1999年 | 3020篇 |
1998年 | 1320篇 |
1997年 | 1257篇 |
1996年 | 1198篇 |
1995年 | 1062篇 |
1994年 | 994篇 |
1993年 | 786篇 |
1992年 | 1977篇 |
1991年 | 1686篇 |
1990年 | 1623篇 |
1989年 | 1431篇 |
1988年 | 1280篇 |
1987年 | 1277篇 |
1986年 | 1085篇 |
1985年 | 1112篇 |
1984年 | 788篇 |
1983年 | 725篇 |
1979年 | 787篇 |
1978年 | 592篇 |
1975年 | 593篇 |
1974年 | 702篇 |
1973年 | 674篇 |
1972年 | 672篇 |
1971年 | 641篇 |
1970年 | 581篇 |
1969年 | 604篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
153.
154.
F S Apple M A Rogers D C Casal L Lewis J L Ivy J W Lampe 《European journal of applied physiology and occupational physiology》1987,56(1):49-52
Total creatine kinase (CK) and CK MB activities were determined in gastrocnemius muscle and serum obtained from 14 female marathon runners. The level of CK MB in muscle increased significantly (p less than 0.05) after chronic exercise training from 5.3% to 10.5% of the total CK activity, but not after acute exercise (post-marathon 8.9%). No significant differences in total CK activities were detected. However, the total CK activity in the muscles were significantly (p less than 0.05) less than those previously reported from the muscle of men runners (1800 U/g, 3000 U/g respectively). No significant correlation existed between fiber type and muscle CK MB activity. Additionally, trace amounts of mitochondrial CK and CK BB were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (597 UL-1) and CK MB (23 UL-1) activities 24 h after the race (r = 0.97, p less than 0.05). These results suggest that gastrocnemius muscle in women adapts to training with increased CK MB activities and imply that skeletal muscle is the major source of elevated serum CK MB activities in women marathon runners. 相似文献
155.
Abstract Azide, an inhibitor of ATPase, and a specific inhibitor of protein export was used in order to select for protein secretion mutants in Acinetobacter calcoaceticus A2. Two such mutants were isolated that were azide-resistant and defective in the general protein transport system. The mutation also conferred additional phenotypic changes, including an inability to grow on minimal media or at 40°C. The existence of protein secretion mutants with a selectable phenotype may be useful for the genetic study of protein export. 相似文献
156.
G. P. Polovinko O. N. Yaroslavtseva Z. A. Teshebaeva V. Yu. Kryukov 《Contemporary Problems of Ecology》2010,3(5):515-521
The paper studies mycobiota of the dead insects in West Siberia, Primorsky krai, and Kyrgyzstan. Ascomycetes anamorphs of
13 genera are revealed. In all regions Beauveria bassiana (Bals.-Criv.) Vuill. dominated comprising on average 68% of the total number of isolates. The fungus hosts list the insects
of 7 orders and 32 families with Coleoptera, Lepidoptera, and Hemiptera dominating. The rarely found entomopathogens include
Tolypocladium inflatum Gams (primarily on Lepidoptera), Metarhizium anisopliae (Metschn.) Sorokin (on Coleoptera). The mortality rate of the insects due to micromycetes is observed mainly on enzootic
level. The study of the pathogenic properties of the dominating species (B. bassiana) show the absence of specificity of its environmental isolates for a number of representatives of Orthoptera, Lepidoptera,
Coleoptera, and Diptera. 相似文献
157.
Z A Bendukidze A N Lopatin V B Ignat'eva S N Sokolova 《Biulleten' eksperimental'no? biologii i meditsiny》1985,99(6):762-764
A method for isolation of guinea-pig cardiomyocytes with pronase has been developed. The method has been assessed in hearts perfused with solutions containing pronase (1 U/ml) and 200 microM Ca2+. Eighty per cent of the cells released were rod-shaped and 1.2 mM Ca2+ tolerant. Enriched medium 199 was used for all solutions. Sodium and slow inward currents recorded from cells dispersed with pronase were similar to those recorded from cells isolated after prolonged exposure to collagenase. Two principal factors are to be marked: (a) presence of high enough amounts of Ca2+ in enzyme solution (up to 200 microM); (b) use of the enriched medium in all the stages of the procedure. 相似文献
158.
Studies were performed in the laboratory, greenhouse and field to assess the potential of Agrotis ipsilon multicapsid nucleopolyhedrovirus (AgipMNPV) and a viral enhancing agent, M2R, for suppression of Agrotis ipsilon (Hufnagel). In laboratory droplet feeding bioassays, AgipMNPV was shown to be highly active against third-instar A. ipsilon. The optical brightener M2R significantly reduced LD50 estimates by approximately 160-fold, but had no direct effect on survival time estimates. In greenhouse trials, spray and bait formulations of AgipMNPV significantly reduced feeding damage to corn seedlings caused by third-instar A. ipsilon. In two sets of replicated field trials, bait formulations of AgipMNPV significantly reduced feeding damage to corn seedlings by third-instar A. ipsilon. However, there were no beneficial effects attributable to the inclusion of M2R in AgipMNPV formulations under greenhouse or field conditions. It seems likely that in an appropriately designed pest management program AgipMNPV could be used to suppress field populations of early and mid-instar A. ipsilon. 相似文献
159.
160.