全文获取类型
收费全文 | 6995篇 |
免费 | 557篇 |
国内免费 | 1篇 |
专业分类
7553篇 |
出版年
2023年 | 42篇 |
2022年 | 47篇 |
2021年 | 107篇 |
2020年 | 76篇 |
2019年 | 97篇 |
2018年 | 214篇 |
2017年 | 212篇 |
2016年 | 263篇 |
2015年 | 412篇 |
2014年 | 328篇 |
2013年 | 456篇 |
2012年 | 586篇 |
2011年 | 568篇 |
2010年 | 324篇 |
2009年 | 231篇 |
2008年 | 369篇 |
2007年 | 329篇 |
2006年 | 335篇 |
2005年 | 305篇 |
2004年 | 293篇 |
2003年 | 254篇 |
2002年 | 218篇 |
2001年 | 195篇 |
2000年 | 193篇 |
1999年 | 143篇 |
1998年 | 64篇 |
1997年 | 29篇 |
1996年 | 37篇 |
1995年 | 45篇 |
1994年 | 24篇 |
1993年 | 29篇 |
1992年 | 84篇 |
1991年 | 52篇 |
1990年 | 55篇 |
1989年 | 50篇 |
1988年 | 46篇 |
1987年 | 60篇 |
1986年 | 42篇 |
1985年 | 42篇 |
1984年 | 46篇 |
1983年 | 18篇 |
1982年 | 22篇 |
1979年 | 16篇 |
1977年 | 14篇 |
1975年 | 19篇 |
1974年 | 29篇 |
1973年 | 17篇 |
1970年 | 11篇 |
1969年 | 10篇 |
1968年 | 15篇 |
排序方式: 共有7553条查询结果,搜索用时 8 毫秒
101.
A Sánchez González J S Casas J Sordo U Russo M I Lareo B J Regueiro 《Journal of inorganic biochemistry》1990,39(3):227-235
We report the synthesis of new complexes with the general formula (R2SnX2)y.H2BiIm, where y = 1 or 2; R = Me, Et, Bun; X = Cl or Br (for R = Et) and H2BiIm = 2,2'-Biimidazole. The complexes have been characterized by elemental analysis and M?ssbauer, infra-red and 1H n.m.r. spectroscopy and tested (like the ligand, Me2SnCl2 and Et2SnCl2) against P388D1 leukemic cells. 相似文献
102.
J M González-Ma?as F M Go?i M Tribout S Paredes 《Archives of biochemistry and biophysics》1990,282(2):239-243
The kinetics of purple membrane dark adaptation were studied at pH 5 and 7, in the presence and absence of the nonionic detergent Triton X-100. The effect of both sublytic and lytic surfactant concentrations has been considered. Our results show that: (a) dark adaptation is faster at pH 5 than at pH 7, (b) dark adaptation is slower, and of smaller amplitude, in the presence than in the absence of Triton X-100. The data may be interpreted in terms of a simple first-order kinetic model, according to which light-dark adaptation would depend basically on the equilibrium between the 13-cis- and the all-trans-isomers. The experiments also suggest that at pH 5, but not at pH 7, solubilizing surfactant concentrations produce a considerable increase in the velocity of the dark adaptation reaction, perhaps through changes in the microenvironment of a protonable group. 相似文献
103.
104.
González-Diez B Cavia M Torres G Abaigar P Camarero V Muñiz P 《Molecular biology reports》2012,39(1):629-634
In the last few years haemodiafiltration with on-line regeneration of ultrafiltrate (HFR) has been shown to have a positive
impact on inflammation and oxidative stress biomarkers, but its effect on antioxidant levels and on oxidative damage to biomolecules
in the long-term is still unknown. This is a randomised clinical study over 12 months involving 40 patients on haemodialysis,
comparing the effect of HFR (n = 25) dialysis with haemodialysis with polysulfone (HD-PS, n = 15) on oxidative stress. Total antioxidant capacity, enzymatic antioxidant [superoxide dismutase (SOD), catalase and glutathione
peroxidase], non-enzymatic (GSH) and biomarkers of oxidative stress (TBARs, carbonyl groups and 8-OH-dG) were evaluated. The
antioxidant activity decreased in the lymphocytes of patients dialysed with HFR, with a significant decrease in the enzyme
SOD. In the oxidative stress biomarkers, an increase was seen in the levels of 8-OH-dG in patients on HD-PS dialysis but not
in those treated with HFR. Throughout the year the changes in antioxidant levels and biomarkers of oxidative damage in patients
dialysed with HFR were generally more modest and fluctuated less than those dialysed with HD-PS. Our study indicates that,
in general, long-term dialysis with HFR does not modified antioxidant parameters or increases the oxidative damage to biomolecules.
The HFR showed to be a biocompatible technique for long-term dialysis. 相似文献
105.
Daniel R. Henríquez Felipe J. Bodaleo Carolina Montenegro-Venegas Christian González-Billault 《PloS one》2012,7(12)
Microtubule-associated protein 1B (MAP1B) is a neuronal protein involved in the stabilization of microtubules both in the axon and somatodendritic compartments. Acute, genetic inactivation of MAP1B leads to delayed axonal outgrowth, most likely due to changes in the post-translational modification of tubulin subunits, which enhances microtubule polymerization. Furthermore, MAP1B deficiency is accompanied by abnormal actin microfilament polymerization and dramatic changes in the activity of small GTPases controlling the actin cytoskeleton. In this work, we showed that MAP1B interacts with a guanine exchange factor, termed Tiam1, which specifically activates Rac1. These proteins co-segregated in neurons, and interact in both heterologous expression systems and primary neurons. We dissected the molecular domains involved in the MAP1B-Tiam1 interaction, and demonstrated that pleckstrin homology (PH) domains in Tiam1 are responsible for MAP1B binding. Interestingly, only the light chain 1 (LC1) of MAP1B was able to interact with Tiam1. Moreover, it was able to increase the activity of the small GTPase, Rac1. These results suggest that the interaction between Tiam1 and MAP1B, is produced by the binding of LC1 with PH domains in Tiam1. The formation of such a complex impacts on the activation levels of Rac1 confirming a novel function of MAP1B related with the control of small GTPases. These results also support the idea of cross-talk between cytoskeleton compartments inside neuronal cells. 相似文献
106.
Dilution experiments were performed to estimate phytoplankton growth and microzooplankton grazing rates during two Lagrangian surveys in inner and eastern locations of the Eastern North Atlantic Subtropical Gyre province (NAST-E). Our design included two phytoplankton size fractions (0.2–5 µm and >5 µm) and five depths, allowing us to characterize differences in growth and grazing rates between size fractions and depths, as well as to estimate vertically integrated measurements. Phytoplankton growth rates were high (0.11–1.60 d−1), especially in the case of the large fraction. Grazing rates were also high (0.15–1.29 d−1), suggesting high turnover rates within the phytoplankton community. The integrated balances between phytoplankton growth and grazing losses were close to zero, although deviations were detected at several depths. Also, O2 supersaturation was observed up to 110 m depth during both Lagrangian surveys. These results add up to increased evidence indicating an autotrophic metabolic balance in oceanic subtropical gyres. 相似文献
107.
108.
Francisco Javier Blancas Mercedes González Macarena Lozano-Oyola Fátima Pérez 《Ecological Indicators》2010,10(2):484-492
This paper introduces an indicator system to evaluate sustainability in established coastal tourism destinations, applying the recommendations and definitions of the World Tourism Organization (WTO). We also develop a new synthetic indicator to simplify the measurement of sustainability and facilitate the comparative analysis of destination ranking. This measurement was obtained by applying a procedure to reduce the number of subjective decisions made by the analyst, using a novel two-stage aggregation methodology based on principal component analysis and on the distance to a reference point. The synthetic indicator obtained was applied to Spanish coastal destinations, and the results serve as a guideline for tourism planning. The conclusions of this research can be extrapolated to the study of other tourism destinations. 相似文献
109.
Limnology - Lake Cuitzeo is Mexico’s second-largest lake (~ 425 km2). The West Basin is shallow, seasonally astatic and alkaline, and it contains saltwater; it is in this... 相似文献
110.
López-González Manuel Víctor González-García Marta Peinado-Aragonés Carlos Antonio Barbancho Miguel Ángel Díaz-Casares Amelia Dawid-Milner Marc Stefan 《Journal of physiology and biochemistry》2020,76(4):561-572
Journal of Physiology and Biochemistry - Connections between the midbrain dorsolateral periaqueductal grey (dlPAG) and the pontine A5 region have been shown. The stimulation of both regions evokes... 相似文献