全文获取类型
收费全文 | 12538篇 |
免费 | 1476篇 |
国内免费 | 1篇 |
出版年
2022年 | 103篇 |
2021年 | 216篇 |
2020年 | 125篇 |
2019年 | 183篇 |
2018年 | 177篇 |
2017年 | 175篇 |
2016年 | 268篇 |
2015年 | 494篇 |
2014年 | 526篇 |
2013年 | 653篇 |
2012年 | 806篇 |
2011年 | 793篇 |
2010年 | 496篇 |
2009年 | 441篇 |
2008年 | 653篇 |
2007年 | 608篇 |
2006年 | 570篇 |
2005年 | 544篇 |
2004年 | 521篇 |
2003年 | 448篇 |
2002年 | 421篇 |
2001年 | 275篇 |
2000年 | 220篇 |
1999年 | 193篇 |
1998年 | 133篇 |
1997年 | 137篇 |
1996年 | 126篇 |
1995年 | 104篇 |
1994年 | 109篇 |
1993年 | 109篇 |
1992年 | 165篇 |
1991年 | 151篇 |
1990年 | 150篇 |
1989年 | 165篇 |
1988年 | 137篇 |
1987年 | 142篇 |
1986年 | 119篇 |
1985年 | 159篇 |
1984年 | 157篇 |
1983年 | 106篇 |
1982年 | 131篇 |
1981年 | 156篇 |
1980年 | 130篇 |
1979年 | 117篇 |
1978年 | 94篇 |
1977年 | 113篇 |
1976年 | 106篇 |
1975年 | 78篇 |
1974年 | 93篇 |
1969年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Li Zhang Mark Morrison Páraic ó Cuív Paul Evans Claire M. Rickard 《Journal of bacteriology》2012,194(23):6639
In recent years, Staphylococcus epidermidis has become a major nosocomial pathogen and the most common cause of intravascular catheter-related bacteremia, which can increase morbidity and mortality and significantly affect patient recovery. We report a draft genome sequence of Staphylococcus epidermidis AU12-03, isolated from an intravascular catheter tip. 相似文献
3.
4.
The ultrasonic calls produced by three day old mice when separated from the nest mother and siblings increase in number when naloxone is injected. 相似文献
5.
1. Male Japanese quail were given 2.20 x 10(-4)-14.53 mg uranium/kg intravenously as uranyl ion (235U label). 2. The relationship between dosage and the 18-hr accumulation of U in leg bones, liver, kidneys and testes was linear. 3. Increases in U deposition with increased dosage were approximately 1:1, except for kidneys where 10-fold increases in dosage resulted in 25-fold increases in deposition. 4. Estradiol-17 beta increased U deposition in bones by 15-fold thereby providing some protection for the kidneys as now the ratio of dosage to accumulation was 1:1. 相似文献
6.
Margot Tertrais Claire Bigot Emmanuel Martin Renaud Poincloux Arnaud Labrousse Isabelle Maridonneau-Parini 《European journal of cell biology》2021,100(4):151161
Phagocytosis consists in ingestion and digestion of large particles, a process strictly dependent on actin re-organization. Using synchronized phagocytosis of IgG-coated latex beads (IgG-LB), zymosan or serum opsonized-zymosan, we report the formation of actin structures on both phagocytic cups and closed phagosomes in human macrophages. Their lifespan, size, protein composition and organization are similar to podosomes. Thus, we called these actin structures phagosome-associated podosomes (PAPs). Concomitantly to the formation of PAPs, a transient disruption of podosomes occurred at the ventral face of macrophages. Similarly to podosomes, which are targeted by vesicles containing proteases, the presence of PAPs correlated with the maturation of phagosomes into phagolysosomes. The ingestion of LB without IgG did not trigger PAPs formation, did not lead to podosome disruption and maturation to phagolysosomes, suggesting that these events are linked together. Although similar to podosomes, we found that PAPs differed by being resistant to the Arp2/3 inhibitor CK666. Thus, we describe a podosome subtype which forms on phagosomes where it probably serves several tasks of this multifunctional structure. 相似文献
7.
R Philipp J O McIntyre B H Robinson H Huth W Trommer S Fleischer 《Biochimica et biophysica acta》1984,790(3):251-258
Calcium efflux and EGTA-induced calcium release from an internal platelet membrane fraction have been studied after the oxalate-supported calcium uptake had reached steady state. Increasing external calcium concentrations stimulate the calcium efflux velocity, with an apparent half-maximal stimulation at about 5 microM outside calcium concentration and a maximal velocity of calcium efflux of 4.66 +/- 2.32 nmol X min-1 X mg-1. Moreover, the ratio of the liberated calcium on the loaded calcium seems to be independent of the increasing external calcium concentration. Increasing the calculated internal calcium concentration by varying the oxalate potassium concentration from 10 mM to 1 mM results in an increase of the liberated calcium from the membrane vesicles from 7.4% to 63%, respectively, without changing the calcium efflux velocity. Similar conclusions can be drawn from the observation of results from the calcium efflux and EGTA-induced calcium release methods. Moreover, calcium pump reversal does not seem to be responsible for the calcium efflux or calcium release. All these different points added to the previously described regulation of calcium efflux by the catalytic subunit of cAMP protein kinase suggest us that the mechanism of calcium liberation by the platelet membranes is different from the calcium uptake. 相似文献
8.
9.
Predator detection and avoidance by starlings under differing scenarios of predation risk 总被引:3,自引:0,他引:3
Devereux Claire L.; Whittingham Mark J.; Fernandez-Juricic Esteban; Vickery Juliet A.; Krebs John R. 《Behavioral ecology》2006,17(2):303-309
Practically all animals must find food while avoiding predators.An individual's perception of predation risk may depend on manyfactors, such as distance to refuge and group size, but it isunclear whether individuals respond to different factors ina similar manner. We tested whether flocks of foraging starlingsresponded in the same way to an increased perception of predationrisk by assessing three factors: (1) neighbor distances, (2)habitat obstruction, and (3) recent exposure to a predator.We found that in all three scenarios of increased risk, starlingsreduced their interscan intervals (food-searching bouts), whichincreased the frequency of their vigilance periods. We thenexamined how one of these factors, habitat obstruction, affectedescape speed by simulating an attack with a model predator.Starlings were slower to respond in visually obstructed habitats(long grass swards) and slower when they had their head downin obstructed habitats than when they had their head down inopen habitats. In addition, reaction times were quicker whenstarlings could employ their peripheral fields of vision. Ourresults demonstrate that different sources of increased riskcan generate similar behavioral responses within a species.The degree of visibility in the physical and social environmentaffects both the actual and perceived risk of predation. 相似文献
10.
Ferdinand Bohlmann Elena Tsankova Jasmin Jakupovic Robert M. King Harold Robinson 《Phytochemistry》1983,22(2):557-560
The investigation of Encelia canescens afforded, in addition to several known compounds, four new dimeric p-hydroxyacetophenone derivatives, two epimeric chromene dimers and two epimeric mixed dimers of euparin and encecalin. Furthermore, derivatives of tremetone and of encecalin were present. The structures were elucidated hy high field 1H NMR spectroscopy. 相似文献