全文获取类型
收费全文 | 5842篇 |
免费 | 456篇 |
国内免费 | 2篇 |
出版年
2022年 | 32篇 |
2021年 | 68篇 |
2020年 | 50篇 |
2019年 | 51篇 |
2018年 | 80篇 |
2017年 | 71篇 |
2016年 | 119篇 |
2015年 | 185篇 |
2014年 | 261篇 |
2013年 | 343篇 |
2012年 | 351篇 |
2011年 | 385篇 |
2010年 | 263篇 |
2009年 | 253篇 |
2008年 | 346篇 |
2007年 | 367篇 |
2006年 | 343篇 |
2005年 | 346篇 |
2004年 | 305篇 |
2003年 | 288篇 |
2002年 | 305篇 |
2001年 | 69篇 |
2000年 | 59篇 |
1999年 | 83篇 |
1998年 | 109篇 |
1997年 | 88篇 |
1996年 | 74篇 |
1995年 | 59篇 |
1994年 | 63篇 |
1993年 | 66篇 |
1992年 | 50篇 |
1991年 | 56篇 |
1990年 | 42篇 |
1989年 | 59篇 |
1988年 | 45篇 |
1987年 | 32篇 |
1986年 | 43篇 |
1985年 | 36篇 |
1984年 | 33篇 |
1983年 | 25篇 |
1982年 | 55篇 |
1981年 | 35篇 |
1980年 | 33篇 |
1979年 | 23篇 |
1978年 | 17篇 |
1977年 | 23篇 |
1976年 | 16篇 |
1975年 | 22篇 |
1974年 | 15篇 |
1972年 | 15篇 |
排序方式: 共有6300条查询结果,搜索用时 0 毫秒
961.
N-Acetyl-β-d-hexosaminidase component A. Different forms in human tissues and fluids 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
1. Hexosaminidase A of human serum was resolved into two components, a minor form with properties identical with those of the single hexosaminidase A component of human liver, and a major form with significantly different properties. 2. The major serum hexosaminidase A form was eluted from a DEAE-cellulose column at a lower salt concentration than that required to elute the liver form. 3. A multiple-pass technique was used to elute the major serum enzyme A from a Sephadex G-150 column before that of liver enzyme A. 4. Clostridium perfringens neuraminidase converted the major component of serum hexosaminidase A into a form that was held less tightly by DEAE-cellulose, but the minor component of the A enzyme of serum, and the A enzyme of liver were not affected. 5. The hexosaminidase A from tears was similar to the A enzyme from serum, whereas those from several human tissues and from urine and lymph were similar to the liver form. 6. The A enzyme from serum may be derived from the A enzyme from liver by glycosylation before secretion. 相似文献
962.
963.
964.
965.
966.
Pia Gruber Filipe Carvalho Marco P. C. Marques Brian O'Sullivan Fabiana Subrizi Dragana Dobrijevic John Ward Helen C. Hailes Pedro Fernandes Roland Wohlgemuth Frank Baganz Nicolas Szita 《Biotechnology and bioengineering》2018,115(3):586-596
967.
Few multiyear precipitation–reduction experiments find a shift in the productivity–precipitation relationship
下载免费PDF全文
![点击此处可从《Global Change Biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Marc Estiarte Sara Vicca Josep Peñuelas Michael Bahn Claus Beier Bridget A. Emmett Philip A. Fay Paul J. Hanson Roland Hasibeder Jaime Kigel Gyorgy Kröel‐Dulay Klaus Steenberg Larsen Eszter Lellei‐Kovács Jean‐Marc Limousin Romà Ogaya Jean‐Marc Ourcival Sabine Reinsch Osvaldo E. Sala Inger Kappel Schmidt Marcelo Sternberg Katja Tielbörger Albert Tietema Ivan A. Janssens 《Global Change Biology》2016,22(7):2570-2581
Well‐defined productivity–precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity–precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation–reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation–manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity–precipitation relationship downward the spatial fit. The majority of experiments (72%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land‐model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation–reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with multiple, including more extreme, dry treatments, to identify the precipitation boundaries within which the current temporal fits remain valid. 相似文献
968.
969.
Roland Abi Nahed Guillaume Martinez Jessica Escoffier Sandra Yassine Thomas Karaouzène Jean-Pascal Hograindleur John Turk George Kokotos Pierre F. Ray Serge Bottari Gérard Lambeau Sylviane Hennebicq Christophe Arnoult 《The Journal of biological chemistry》2016,291(6):3076-3089
Phospholipase A2 (PLA2) activity has been shown to be involved in the sperm acrosome reaction (AR), but the molecular identity of PLA2 isoforms has remained elusive. Here, we have tested the role of two intracellular (iPLA2β and cytosolic PLA2α) and one secreted (group X) PLA2s in spontaneous and progesterone (P4)-induced AR by using a set of specific inhibitors and knock-out mice. iPLA2β is critical for spontaneous AR, whereas both iPLA2β and group X secreted PLA2 are involved in P4-induced AR. Cytosolic PLA2α is dispensable in both types of AR. P4-induced AR spreads over 30 min in the mouse, and kinetic analyses suggest the presence of different sperm subpopulations, using distinct PLA2 pathways to achieve AR. At low P4 concentration (2 μm), sperm undergoing early AR (0–5 min post-P4) rely on iPLA2β, whereas sperm undergoing late AR (20–30 min post-P4) rely on group X secreted PLA2. Moreover, the role of PLA2s in AR depends on P4 concentration, with the PLA2s being key actors at low physiological P4 concentrations (≤2 μm) but not at higher P4 concentrations (∼10 μm). 相似文献
970.