全文获取类型
收费全文 | 58898篇 |
免费 | 4327篇 |
国内免费 | 140篇 |
出版年
2021年 | 407篇 |
2020年 | 366篇 |
2019年 | 397篇 |
2018年 | 976篇 |
2017年 | 915篇 |
2016年 | 1400篇 |
2015年 | 2201篇 |
2014年 | 2354篇 |
2013年 | 3030篇 |
2012年 | 3720篇 |
2011年 | 3491篇 |
2010年 | 2153篇 |
2009年 | 1632篇 |
2008年 | 2902篇 |
2007年 | 2894篇 |
2006年 | 2868篇 |
2005年 | 2662篇 |
2004年 | 2583篇 |
2003年 | 2405篇 |
2002年 | 2385篇 |
2001年 | 1607篇 |
2000年 | 1704篇 |
1999年 | 1353篇 |
1998年 | 517篇 |
1997年 | 432篇 |
1996年 | 404篇 |
1995年 | 377篇 |
1994年 | 395篇 |
1993年 | 359篇 |
1992年 | 836篇 |
1991年 | 801篇 |
1990年 | 787篇 |
1989年 | 736篇 |
1988年 | 696篇 |
1987年 | 621篇 |
1986年 | 606篇 |
1985年 | 556篇 |
1984年 | 497篇 |
1983年 | 456篇 |
1982年 | 397篇 |
1981年 | 394篇 |
1979年 | 513篇 |
1978年 | 391篇 |
1977年 | 332篇 |
1975年 | 386篇 |
1974年 | 377篇 |
1973年 | 347篇 |
1972年 | 363篇 |
1971年 | 326篇 |
1968年 | 314篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Acetobacter acetii DSMZ3508 and related bacteria converted 2,2-dimethyl-1,3-propanediol into 3-hydroxypivalic acid (2,2-dimethyl-3-hydroxypropionic acid; 3HP) during submerged cultivation in mineral salt medium. The maximum yield of 3-hydroxypivalic acid was 24.4% of the fed substrate after 18 days. Cultivation parameters, as pH, cell density, optimal substrate concentration, and oxygen supply for the bioconversion process were determined. 相似文献
132.
Sabrina Forveille Heng Zhou Allan Sauvat Lucillia Bezu Kevin Müller Peng Liu Laurence Zitvogel Gérard Pierron ?ystein Rekdal Oliver Kepp Guido Kroemer 《Cell cycle (Georgetown, Tex.)》2015,14(21):3506-3512
The oncolytic peptide LTX-315 has been designed for killing human cancer cells and turned out to stimulate anti-cancer immune responses when locally injected into tumors established in immunocompetent mice. Here, we investigated the question whether LTX-315 induces apoptosis or necrosis. Transmission electron microscopy or morphometric analysis of chromatin-stained tumor cells revealed that LTX-315 failed to induce apoptotic nuclear condensation and rather induced a necrotic phenotype. Accordingly, LTX-315 failed to stimulate the activation of caspase-3, and inhibition of caspases by means of Z-VAD-fmk was unable to reduce cell killing by LTX-315. In addition, 2 prominent inhibitors of regulated necrosis (necroptosis), namely, necrostatin-1 and cycosporin A, failed to reduce LTX-315-induced cell death. In conclusion, it appears that LTX-315 triggers unregulated necrosis, which may contribute to its pro-inflammatory and pro-immune effects. 相似文献
133.
134.
Oat (Avena sativa L.) mesophyll protoplasts were recently demonstrated to be capable of dedifferentiation, repeated divisions, and colony formation. Since the development of oat mesophyll protoplasts is decisively influenced by the nature of the used feeder culture (species, variety and concentration), we conducted a systematic study of this parameter. Generally, graminaceous feeders promoted protoplast proliferation, while dicot species repressed protoplast divisions. The beneficial effect of those feeders that promote divisions was counterbalanced by a factor that causes necrosis. The correct balance between promotion of divisions or necrosis depended on the nature of the feeder and its plating density. 相似文献
135.
1. Within the range of the given conditions of measuring static and dynamic properties of the rabbit gastrocnemius muscle the following results were obtained: a) the dependence of the maxima of isotonic shortening upon the relative length of the muscle at constant load is linear; b) the parameters of the non-linear dependence of the passive elastic force of the muscle upon its relative length (measured in series) were identified using asymptotic regression; c) the time course of isotonic contractions (at an interval from 0 to 0.3 s after the beginning of stimulation) could be satisfactorily approximated by responses of a linear system to a step-function; d) the time course of isometric contractions (at an interval from 0 to 0.3 s after the beginning of stimulation) could be closely approximated by responses of a linear system to a step-function. 2. The time constants of isotonic and isometric contractions were determined as the parameters of the corresponding linear systems. 3. The maximum rates of the isometric and isotonic contractions were determined as maxima of the first derivatives of the responses of the corresponding models. 4. The experimental set-up made it possible to compare the values of the parameters concomitantly followed at various muscle lengths and at various loads. 相似文献
136.
Paola A Gilardoni Stefan Schuck Ruth Jüngling Björn Rotter Ian T Baldwin Gustavo Bonaventure 《BMC plant biology》2010,10(1):66
Background
Plants trigger and tailor defense responses after perception of the oral secretions (OS) of attacking specialist lepidopteran larvae. Fatty acid-amino acid conjugates (FACs) in the OS of the Manduca sexta larvae are necessary and sufficient to elicit the herbivory-specific responses in Nicotiana attenuata, an annual wild tobacco species. How FACs are perceived and activate signal transduction mechanisms is unknown. 相似文献137.
Fr. Antoine 《Plant Systematics and Evolution》1874,24(10):309-310
Ohne Zusammenfassung 相似文献
138.
139.
140.
R Würmli S Wolffram E Scharrer 《Comparative biochemistry and physiology. A, Comparative physiology》1987,88(1):127-129
1. The influence of nitrate and nitrite on net absorption of electrolytes (Na+, K+, Cl-) and water from ligated loops was studied at various intestinal sites in rats. 2. Nitrate strikingly reduced Cl- absorption in rat proximal and distal colon, whereas Na+ absorption was reduced only moderately. Nitrite also reduced Cl- absorption in the colon. 3. Nitrate showed no significant effect on electrolyte absorption in the small intestine. 4. The results suggest that Cl-/HCO3- on exchange is the major route of Cl- absorption in the colon, whereas this mechanism seems not to be of importance for Cl- absorption by the small intestine. 相似文献