全文获取类型
收费全文 | 3941篇 |
免费 | 337篇 |
国内免费 | 1篇 |
出版年
2023年 | 17篇 |
2022年 | 25篇 |
2021年 | 58篇 |
2020年 | 34篇 |
2019年 | 40篇 |
2018年 | 83篇 |
2017年 | 53篇 |
2016年 | 92篇 |
2015年 | 164篇 |
2014年 | 210篇 |
2013年 | 202篇 |
2012年 | 296篇 |
2011年 | 263篇 |
2010年 | 175篇 |
2009年 | 155篇 |
2008年 | 220篇 |
2007年 | 247篇 |
2006年 | 209篇 |
2005年 | 220篇 |
2004年 | 172篇 |
2003年 | 205篇 |
2002年 | 175篇 |
2001年 | 42篇 |
2000年 | 30篇 |
1999年 | 33篇 |
1998年 | 47篇 |
1997年 | 37篇 |
1996年 | 31篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 27篇 |
1992年 | 15篇 |
1991年 | 30篇 |
1990年 | 40篇 |
1989年 | 23篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 17篇 |
1985年 | 18篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 25篇 |
1981年 | 24篇 |
1980年 | 21篇 |
1978年 | 15篇 |
1977年 | 16篇 |
1974年 | 14篇 |
1969年 | 13篇 |
1968年 | 13篇 |
1967年 | 15篇 |
排序方式: 共有4279条查询结果,搜索用时 15 毫秒
161.
Georg Imsiecke Marcio Custodio Radovan Borojevic Renate Steffen Mohamed A. Moustafa Werner E. G. Müller 《Cell biology international》1995,19(12):995-1000
The genome size of the marine sponges Suberites domuncula and Geodia cydonium has been determined by flow cytofluorometric analysis using diamidino-phenylindole [DAPI]. Using human lymphocytes as reference the amount of DNA in cells from S. domuncula has been determined to be 3.7 pg and that of G. cydonium 3.3 pg. While no chromosomes could be identified in G. cydonium, the karyotype of the Suberites domuncula is 32 chromsomes in the diploid state. The size of the chromosomes was between 0.25 and 1.0 μm. No pronounced banding pattern was visible. 相似文献
162.
163.
Andreas Schoofs Ulrike Hanslik Senta Niederegger Hans‐Georg Heinzel Roland Spieß 《Journal of morphology》2010,271(8):969-979
We describe the anatomy of the nerves that project from the central nervous system (CNS) to the pro‐ and mesothoracic segments and the cephalopharyngeal skeleton (CPS) for third instar Calliphora larvae. Due to the complex branching pattern we introduce a nomenclature that labels side branches of first and second order. Two fine nerves that were not yet described are briefly introduced. One paired nerve projects to the ventral arms (VAs) of the CPS. The second, an unpaired nerve, projects to the ventral surface of the cibarial part of the esophagus (ES). Both nerves were tentatively labeled after the structures they innervate. The antennal nerve (AN) innervates the olfactory dorsal organ (DO). It contains motor pathways that project through the frontal connectives (FC) to the frontal nerve (FN) and innervate the cibarial dilator muscles (CDM) which mediate food ingestion. The maxillary nerve (MN) innervates the sensory terminal organ (TO), ventral organ (VO), and labial organ (LO) and comprises the motor pathways to the mouth hook (MH) elevator, MH depressor, and the labial retractor (LR) which opens the mouth cavity. An anastomosis of unknown function exists between the AN and MN. The prothoracic accessory nerve (PaN) innervates a dorsal protractor muscle of the CPS and sends side branches to the aorta and the bolwig organ (BO) (stemmata). In its further course, this nerve merges with the prothoracic nerve (PN). The architecture of the PN is extremely complex. It innervates a set of accessory pharyngeal muscles attached to the CPS and the body wall musculature of the prothorax. Several anastomoses exist between side branches of this nerve which were shown to contain motor pathways. The mesothoracic nerve (MeN) innervates a MH accessor and the longitudinal and transversal body wall muscles of the second segment. J. Morphol. 271:969–979, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
164.
Markus Albert Anna K. Jehle Martin Lipschis Katharina Mueller Yi Zeng Georg Felix 《European journal of cell biology》2010,89(2-3):200-207
In this review we focus on pattern recognition receptors in plants that detect extracellular signals indicative for pathogen attack and injury. We start out with a discussion on FLS2, which binds and responds to bacterial flagellin, and then concentrate on ligand–receptor interactions as initial steps in the molecular receptor activation process. Comparison with other receptor kinases, whether involved in plant immunity or regulation of other cellular programs, might indicate common principles of receptor activation. 相似文献
165.
Quantitative detection of siRNA and single-stranded oligonucleotides: relationship between uptake and biological activity of siRNA 总被引:2,自引:2,他引:0
The quantitative detection of oligomeric nucleic acids including short double-stranded RNA in cells and tissues becomes increasingly important. Here, we describe a method for the detection of siRNA in extracts prepared from mammalian cells, which is based on liquid hybridization with a 32P-labelled probe followed by a nuclease protection step. The limit of detection of absolute amounts of siRNA is in the order of 10–100 amol. This methodology is suited to quantitatively follow the spontaneous uptake of siRNA by mammalian cells, i.e. without the use of carrier substances. This protocol may also be used to detect extremely low amounts of other kinds of short nucleic acids, including antisense oligonucleotides. 相似文献
166.
167.
Role of endothelial nitric oxide synthase in endothelial activation: insights from eNOS knockout endothelial cells 总被引:3,自引:0,他引:3
Kuhlencordt PJ Rosel E Gerszten RE Morales-Ruiz M Dombkowski D Atkinson WJ Han F Preffer F Rosenzweig A Sessa WC Gimbrone MA Ertl G Huang PL 《American journal of physiology. Cell physiology》2004,286(5):C1195-C1202
The objective of this study was to determine whether absence of endothelial nitric oxide synthase (eNOS) affects the expression of cell surface adhesion molecules in endothelial cells. Murine lung endothelial cells (MLECs) were prepared by immunomagnetic bead selection from wild-type and eNOS knockout mice. Wild-type cells expressed eNOS, but eNOS knockout cells did not. Expression of neuronal NOS and inducible NOS was not detectable in cells of either genotype. Upon stimulation, confluent wild-type MLECs produced significant amounts of NO compared with N-monomethyl-L-arginine-treated wild-type cells. eNOS knockout and wild-type cells showed no difference in the expression of E-selectin, P-selectin, intracellular adhesion molecule-1, and vascular cell adhesion molecule-1 as measured by flow cytometry on the surface of platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31)-positive cells. Both eNOS knockout and wild-type cells displayed the characteristics of resting endothelium. Adhesion studies in a parallel plate laminar flow chamber showed no difference in leukocyte-endothelial cell interactions between the two genotypes. Cytokine treatment induced endothelial cell adhesion molecule expression and increased leukocyte-endothelial cell interactions in both genotypes. We conclude that in resting murine endothelial cells, absence of endothelial production of NO by itself does not initiate endothelial cell activation or promote leukocyte-endothelial cell interactions. We propose that eNOS derived NO does not chronically suppress endothelial cell activation in an autocrine fashion but serves to counterbalance signals that mediate activation. vascular biology; atherosclerosis; mouse models 相似文献
168.
169.
170.
The simulations in this paper show that exposure measurement error affects the parameter estimates of the biologically motivated two-stage clonal expansion (TSCE) model. For both Berkson and classical error models, we show that likelihood-based techniques of correction work reliably. For classical errors, the distribution of true exposures needs to be known or estimated in addition to the distribution of recorded exposures conditional on true exposures. Usually the exposure uncertainty biases the model parameters toward the null and underestimates the precision. But when several parameters are allowed to be dependent on exposure, e.g. initiation and promotion, then their relative importance is also influenced, and more complicated effects of exposure uncertainty can occur. The application part of this paper shows for two different types of Berkson errors that a recent analysis of the data for the Colorado plateau miners with the TSCE model is not changed substantially when correcting for such errors. Specifically, the conjectured promoting action of radon remains as the dominant radiation effect for explaining these data. The estimated promoting action of radon increases by a factor of up to 1.2 for the largest assumed exposure uncertainties. 相似文献