全文获取类型
收费全文 | 143866篇 |
免费 | 10053篇 |
国内免费 | 21篇 |
出版年
2023年 | 785篇 |
2022年 | 904篇 |
2021年 | 2043篇 |
2020年 | 1660篇 |
2019年 | 1918篇 |
2018年 | 3631篇 |
2017年 | 3301篇 |
2016年 | 4676篇 |
2015年 | 6731篇 |
2014年 | 7059篇 |
2013年 | 9359篇 |
2012年 | 11053篇 |
2011年 | 10303篇 |
2010年 | 6700篇 |
2009年 | 5207篇 |
2008年 | 8062篇 |
2007年 | 7936篇 |
2006年 | 7382篇 |
2005年 | 6699篇 |
2004年 | 6329篇 |
2003年 | 5756篇 |
2002年 | 5339篇 |
2001年 | 2795篇 |
2000年 | 2694篇 |
1999年 | 2343篇 |
1998年 | 1123篇 |
1997年 | 881篇 |
1996年 | 781篇 |
1995年 | 786篇 |
1994年 | 731篇 |
1993年 | 606篇 |
1992年 | 1480篇 |
1991年 | 1384篇 |
1990年 | 1220篇 |
1989年 | 1109篇 |
1988年 | 1032篇 |
1987年 | 921篇 |
1986年 | 825篇 |
1985年 | 871篇 |
1984年 | 810篇 |
1983年 | 658篇 |
1982年 | 529篇 |
1981年 | 494篇 |
1980年 | 428篇 |
1979年 | 651篇 |
1978年 | 505篇 |
1977年 | 439篇 |
1975年 | 477篇 |
1974年 | 517篇 |
1973年 | 502篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
B Alexandre F Thiébaut M Allary E Boschetti C Séné J Saint-Blancard 《Revue fran?aise de transfusion et immuno-hématologie》1987,30(1):57-66
In this work the human plasma fibronectin was purified by affinity chromatography using a tandem column system. The first affinity column was filled with gelatin-Trisacryl whereas the second one contained heparin-Trisacryl. This double affinity chromatography demonstrated its high efficiency in term of purity and yield. Several analytical methods (electrophoresis, immunoelectrophoresis, F.P.L.C. and adhesion assay on cultured eucaryotic cells) evidenced in fact the high purity of the preparation as well as its biological behaviour in term of cell adhesion and spreading. The performances of the sorbents used facilitate the scaling up when large quantities of FNP are needed. 相似文献
62.
F Krizsa Z Borbényi E Arokszállásy I Cserháti 《Folia haematologica (Leipzig, Germany : 1928)》1980,107(4):683-687
The thrombopoietic serum activity was examined in rats during thrombocytopenia produced by bleeding or after treatment with antithrombocyte serum (ATS). 6 hours after both treatments the thrombopoietic activity of the serum, i.e. its content of thrombopoietin, is increased. After the ATS treatment of nephrectomized animals a similar increase of thrombopoietic activity as in normal animals could be achieved. In contrast to that, no similar increase of thrombopoietic activity was observed in nephrectomized animals after blood loss. According to the results of the authors the increase of thrombopoietic activity produced by different stimuli can be attributed to different mechanisms. 相似文献
63.
64.
Valentina Isetta Josep M. Montserrat Raquel Santano Alison J. Wimms Dinesh Ramanan Holger Woehrle Daniel Navajas Ramon Farré 《PloS one》2016,11(3)
Bench testing is a useful method to characterize the response of different automatic positive airway pressure (APAP) devices under well-controlled conditions. However, previous models did not consider the diversity of obstructive sleep apnea (OSA) patients’ characteristics and phenotypes. The objective of this proof-of-concept study was to design a new bench test for realistically simulating an OSA patient’s night, and to implement a one-night example of a typical female phenotype for comparing responses to several currently-available APAP devices. We developed a novel approach aimed at replicating a typical night of sleep which includes different disturbed breathing events, disease severities, sleep/wake phases, body postures and respiratory artefacts. The simulated female OSA patient example that we implemented included periods of wake, light sleep and deep sleep with positional changes and was connected to ten different APAP devices. Flow and pressure readings were recorded; each device was tested twice. The new approach for simulating female OSA patients effectively combined a wide variety of disturbed breathing patterns to mimic the response of a predefined patient type. There were marked differences in response between devices; only three were able to overcome flow limitation to normalize breathing, and only five devices were associated with a residual apnea-hypopnea index of <5/h. In conclusion, bench tests can be designed to simulate specific patient characteristics, and typical stages of sleep, body position, and wake. Each APAP device behaved differently when exposed to this controlled model of a female OSA patient, and should lead to further understanding of OSA treatment. 相似文献
65.
66.
Feasible mechanisms for algal digestion in the king angelfish 总被引:1,自引:0,他引:1
To determine the ability of the king angelfish Holacanthus passer to digest algae, three algal species were immersed in acidic conditions similar to that found in the stomach of fish. Only one of them was not susceptible to acidic lysis; two were affected after 40 and 60 min at pH 2·0. King angelfish have an expanded region of the intestine called here the hindgut chamber (HC) containing populations of micro-organisms. Some of these micro-organisms have the capacity to grow in cellulose, agar, and alginic acid; the main components of algal cell walls. Micro-organisms grew in carboxymethylcellulose cultures under aerobic and micro-aerobic conditions. The HC is highly vascularized, which could increase absorptive efficiency of material digested in it. 相似文献
67.
Francisco Gutirrez‐Corchero M. Victoria Arruga Lourdes Sanz Cristina García M. Angeles Hernndez Francisco Campos 《Molecular ecology resources》2002,2(1):75-77
FTA® cards were used for long‐term storage of avian blood samples. Blood DNA was extracted by a simple method and used in PCR for sex identification of adult and nestling Great Grey Shrikes Lanius excubitor. 相似文献
68.
69.
F García J Sánchez J Planas 《Comparative biochemistry and physiology. A, Comparative physiology》1987,87(4):947-950
1. Male quails submitted 20 and 120 days to a low iron diet (7 ppm) were compared to female laying quails, exposed for 30 days to the same low iron regime, in order to compare the response of the iron metabolic control under a single (erythropoiesis) or a doubled (erythropoiesis and egg formation) iron demand. 2. Iron deposit in storage organs, the classical hematology and the intestinal iron absorption were analyzed in these animals. 3. In males, after 120 days, the iron deposits were reduced 50 and 75%, but hematological values (hematocrit and hemoglobin concentration) were normal, although in laying quails, after 30 days, an anemic condition was evident in both blood parameters and iron deposits, provoking an iron deficient erythropoiesis. 4. The enhancement of the intestinal iron uptake, confirms the anemic character of these birds. 相似文献
70.
A Rhalem K Bekhti C Bourdieu G Luffau P Péry 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1989,309(1):19-23
Proteins are released from the surface of sporozoites of Eimeria falciformis during their in vitro incubation in a detergent solution. Some of these proteins reacted with antibodies from infected mice and specifically stimulated the proliferation of mesenteric lymph node cells of these mice. Oral immunization of mice with liposome encapsulated sporozoite surface antigens protected mice against a challenge infection. Two proteins (M.W. 27 and 180 K) induced an antibody synthesis in these vaccinated mice. 相似文献