全文获取类型
收费全文 | 128274篇 |
免费 | 9099篇 |
国内免费 | 33篇 |
专业分类
137406篇 |
出版年
2023年 | 642篇 |
2022年 | 566篇 |
2021年 | 1309篇 |
2020年 | 1116篇 |
2019年 | 1208篇 |
2018年 | 3012篇 |
2017年 | 2680篇 |
2016年 | 3833篇 |
2015年 | 5704篇 |
2014年 | 5845篇 |
2013年 | 7852篇 |
2012年 | 9642篇 |
2011年 | 9084篇 |
2010年 | 5794篇 |
2009年 | 4429篇 |
2008年 | 7367篇 |
2007年 | 7318篇 |
2006年 | 6757篇 |
2005年 | 6338篇 |
2004年 | 6030篇 |
2003年 | 5622篇 |
2002年 | 5275篇 |
2001年 | 2406篇 |
2000年 | 2296篇 |
1999年 | 2051篇 |
1998年 | 1026篇 |
1997年 | 791篇 |
1996年 | 670篇 |
1995年 | 695篇 |
1994年 | 692篇 |
1993年 | 592篇 |
1992年 | 1369篇 |
1991年 | 1293篇 |
1990年 | 1158篇 |
1989年 | 1055篇 |
1988年 | 1006篇 |
1987年 | 870篇 |
1986年 | 800篇 |
1985年 | 911篇 |
1984年 | 801篇 |
1983年 | 677篇 |
1982年 | 576篇 |
1981年 | 572篇 |
1980年 | 490篇 |
1979年 | 654篇 |
1978年 | 545篇 |
1977年 | 493篇 |
1975年 | 492篇 |
1974年 | 549篇 |
1973年 | 539篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
51.
Regulation of G(1) cell-cycle progression by oncogenes and tumor suppressor genes. 总被引:13,自引:0,他引:13
Progression of resting quiescent G(0) cells into early G(1) and transition across the restriction point are highly regulated processes. Mutation of proto-oncogenes and tumor suppressor genes regulating these transitions are targeted during oncogenesis. Recent work has underscored the importance of the G(0) to early G(1) transition and metabolism to neoplastic cells. 相似文献
52.
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
53.
54.
Marianne E. Walsh Charles M. Collins Thomas F. Jenkins Alan D. Hewitt Jeff Stark Karen Myers 《Soil & Sediment Contamination》2003,12(5):631-645
Fort Greely, Alaska has an extensive complex of weapon training and testing areas located on lands withdrawn from the public domain under the Military Lands Withdrawal Act (PL106-65). The Army has pledged to implement a program to identify possible munitions contamination. Because of the large size (344,165,000 m2) of the high hazard impact areas, characterization of these constituents will be difficult. We used an authoritative sampling design to find locations most likely to contain explosives-residues on three impact areas. We focused our sampling on surface soils and collected multi-increment and discrete samples at locations of known firing events and from areas on the range that had craters, pieces of munitions, targets, or a designation as a firing point. In the two impact areas used primarily by the Army, RDX was the most frequently detected explosive. In the impact area that was also used by the Air Force, TNT was the most frequently detected explosive. Where detected, the explosives concentrations generally were low (<0.05 mg/kg) except in soils near low-order detonations, where the explosive-filler was in contact with the soil surface. These low-order detonations potentially can serve as localized sources for groundwater contamination if positioned in recharge areas. 相似文献
55.
56.
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
57.
J R David P Gibert G Pétavy B Moreteau 《Proceedings. Biological sciences / The Royal Society》2002,269(1487):127-135
We investigated body-size inheritance in interspecific sterile hybrids by crossing a Drosophila simulans strain with 13 strains of Drosophila melanogaster, which were of various origins and chosen for their broad range of genetic variation. A highly significant parent-offspring correlation was observed, showing that the D. melanogaster genes for size are still expressed in a hybrid background. Superimposed on to this additive inheritance, the size of hybrids was always less than the mid-parent value. This phenomenon, which at first sight might be described as dominance or overdominance, is more precisely interpreted as a consequence of a hybrid breakdown, that is, a dysfunction of the parental genes for size when put to work together. This interpretation is enforced by the fact that phenotypic variability was much more prevalent in hybrids than in parents. We also analysed body pigmentation inheritance in the same crosses and got a very different picture. There was no increase in the phenotypic variance of F(1) hybrids and only a low parent-offspring correlation. Apparent overdominance could be observed but in opposite directions, with no evidence of hybrid breakdown. Our data point to the possibility of analysing a diversity of quantitative traits in interspecific hybrids, and indicate that breakdown might be restricted to some traits only. 相似文献
58.
M Lebl E E Sugg G van Binst P Vander Elst D Tourwé J Slaninová V J Hruby 《International journal of peptide and protein research》1987,30(3):318-322
Analogs of deamino-oxytocin and deamino-oxypressin containing a CH2-NH group instead of an amide bond between positions 8 and 9 were synthesized. All tested compounds exhibit significantly lowered biological activities. 相似文献
59.
60.