全文获取类型
收费全文 | 12266篇 |
免费 | 1152篇 |
国内免费 | 2篇 |
出版年
2022年 | 117篇 |
2021年 | 203篇 |
2020年 | 113篇 |
2019年 | 147篇 |
2018年 | 172篇 |
2017年 | 147篇 |
2016年 | 305篇 |
2015年 | 543篇 |
2014年 | 587篇 |
2013年 | 764篇 |
2012年 | 942篇 |
2011年 | 852篇 |
2010年 | 550篇 |
2009年 | 490篇 |
2008年 | 754篇 |
2007年 | 742篇 |
2006年 | 690篇 |
2005年 | 650篇 |
2004年 | 618篇 |
2003年 | 548篇 |
2002年 | 560篇 |
2001年 | 170篇 |
2000年 | 126篇 |
1999年 | 154篇 |
1998年 | 190篇 |
1997年 | 111篇 |
1996年 | 117篇 |
1995年 | 98篇 |
1994年 | 121篇 |
1993年 | 101篇 |
1992年 | 94篇 |
1991年 | 80篇 |
1990年 | 111篇 |
1989年 | 91篇 |
1988年 | 80篇 |
1987年 | 59篇 |
1986年 | 63篇 |
1985年 | 75篇 |
1984年 | 70篇 |
1983年 | 64篇 |
1982年 | 68篇 |
1981年 | 63篇 |
1980年 | 50篇 |
1979年 | 47篇 |
1978年 | 47篇 |
1977年 | 35篇 |
1976年 | 54篇 |
1975年 | 45篇 |
1974年 | 39篇 |
1973年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
21.
B. A. Uijtewaal E. Posthumus L. C. J. M. Suurs E. Jacobsen J. G. Th. Hermsen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,74(4):451-458
Summary Plant growth performance was studied in 118 potato monohaploids and in their diploid parents. Of these monohaploids 76 were also investigated at the protoplast level and eight of these were used in protoplast fusion experiments as well. No correlation was found between relative performance of greenhouse grown and in vitro grown plants. No or only weak correlations were found between different in vitro characteristics such as plant growth, protoplast yield per gram plant material, plating efficiency and callus growth. This indicates the unpredictability of these characters.The protoplast fusion experiments indicated that only in some genotype combinations increased callus growth rates may be found. However, it is not clear whether such calli were hybrids or not. In protoplast monocultures only diploid and tetraploid regenerants were obtained. After fusion, tetraploids but also some triploids could be regenerated. The finding of triploids indicates that monoploid protoplasts were involved in fusion. Isozyme analysis and morphological assessment of the plants pointed out that the majority of the fusion regenerants were hybrids. The implications of these results are discussed. 相似文献
22.
23.
24.
Ruth Holland 《BMJ (Clinical research ed.)》1986,293(6553):1010
25.
26.
Mutations in the conserved C-terminal sequence in thyroid hormone receptor dissociate hormone-dependent activation from interference with AP-1 activity. 总被引:4,自引:2,他引:2 下载免费PDF全文
27.
28.
Eva Hammarskj?ld Karin Harms-Ringdahl 《European journal of applied physiology and occupational physiology》1992,64(5):402-409
The purpose of the study was to analyse the effect of arm-shoulder fatigue on manual performance. Ten experienced carpenters performed three standardized tasks (nailing, sawing and screwing). Electromyographic activity was recorded from six arm-shoulder muscles and the performances were video-filmed. After 45 min of standardized arm-cranking (arm-shoulder-fatiguing exercise of approximately 70%-80% maximal oxygen consumption), the tasks were repeated. The number of work movements and the time taken for each task were recorded and the quality of the work performed was compared. After the fatiguing exercise, only nailing was perceived as being harder and more mistakes were made during nailing and sawing. Movement performance was not influenced during nailing but was slightly slower during sawing and faster during screwing. However, there were increased mean EMG amplitudes in the upper trapezius and biceps muscles during nailing, in the upper trapezius, anterior deltoid and infraspinatus muscles during sawing and in the anterior deltoid muscle during screwing. Of the muscles studied the upper trapezius and anterior deltoid muscles increased their activity most after the arm-shoulder-fatiguing exercise. 相似文献
29.
D A Keire P Anton K F Faull E Ruth J H Walsh P Chew D Quisimoro M Territo J R Reeve 《The Journal of biological chemistry》2001,276(52):48847-48853
The structure of a small-molecule, non-peptide chemotactic factor has been determined from activity purified to apparent homogeneity from Helicobacter pylori supernatants. H. pylori was grown in brucella broth media until one liter of solution had 0.9 absorbance units. The culture was centrifuged, and the bacteria re-suspended in physiological saline and incubated at 37 degrees C for 4 h. A monocyte migration bioassay revealed the presence of a single active chemotactic factor in the supernatant from this incubation. The chemotactic factor was concentrated by solid phase chromatography and purified by reverse phase high pressure liquid chromatography. The factor was shown to be indistinguishable from diethyl phthalate (DEP) on the basis of multiple criteria including nuclear magnetic resonance spectroscopy, electron impact mass spectroscopy, UV visible absorption spectrometry, GC and high pressure liquid chromatography retention times, and chemotactic activity toward monocytes. Control experiments with incubated culture media without detectable bacteria did not yield detectable DEP, suggesting it is bacterially derived. It is not known if the bacteria produce diethyl phthalate de novo or if it is a metabolic product of a precursor molecule present in culture media. DEP produced by H. pylori in addition to DEP present in man-made products may contribute to the high levels of DEP metabolites observed in human urine. DEP represents a new class of chemotactic factor. 相似文献
30.
Paola A Gilardoni Stefan Schuck Ruth Jüngling Björn Rotter Ian T Baldwin Gustavo Bonaventure 《BMC plant biology》2010,10(1):66