全文获取类型
收费全文 | 1671篇 |
免费 | 149篇 |
出版年
2023年 | 14篇 |
2022年 | 13篇 |
2021年 | 68篇 |
2020年 | 25篇 |
2019年 | 31篇 |
2018年 | 59篇 |
2017年 | 45篇 |
2016年 | 77篇 |
2015年 | 73篇 |
2014年 | 111篇 |
2013年 | 107篇 |
2012年 | 135篇 |
2011年 | 106篇 |
2010年 | 75篇 |
2009年 | 67篇 |
2008年 | 81篇 |
2007年 | 76篇 |
2006年 | 60篇 |
2005年 | 67篇 |
2004年 | 74篇 |
2003年 | 71篇 |
2002年 | 44篇 |
2001年 | 20篇 |
2000年 | 25篇 |
1999年 | 16篇 |
1998年 | 21篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1969年 | 7篇 |
1968年 | 9篇 |
1966年 | 6篇 |
排序方式: 共有1820条查询结果,搜索用时 15 毫秒
1.
Nabiel A.M. Saleh Zeinab A.R. El-karemy Ragaa M.A. Mansour Abdel-Aziz A. Fayed 《Phytochemistry》1983,22(11):2501-2505
The flavonoids of five Geranium, fourteen Erodium and four Monsonia species were studied. Quercetin was the most common aglycone with lesse 相似文献
2.
A noninvasive measurement of pharyngeal cross-sectional area (CSA) during sleep would be advantageous for research studies. We hypothesized that CSA could be calculated from the measured pharyngeal pressure and flow by finite element analysis (FEA). The retropalatal airway was visualized by using a fiber-optic scope to obtain the measured CSA (mCSA). Flow was measured with a pneumotachometer, and pharyngeal pressure was measured with a pressure catheter at the palatal rim. FEA was performed as follows: by using a three-dimensional image of the upper airway, a mesh of finite elements was created. Specialized software was used to allow the simultaneous calculation of velocity and area for each element by using the measured pressure and flow. In the development phase, 677 simultaneous measurements of CSA, pressure, and flow from one subject during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep were entered into the software to determine a series of equations, based on the continuity and momentum equations, that could calculate the CSA (cCSA). In the validation phase, the final equations were used to calculate the CSA from 1,767 simultaneous measurements of pressure and flow obtained during wakefulness, NREM, and REM sleep from 14 subjects. In both phases, mCSA and cCSA were compared by Bland-Altman analysis. For development breaths, the mean difference between mCSA and cCSA was 0.0 mm2 (95% CI, -0.1, 0.1 mm2). For NREM validation breaths, the mean difference between mCSA and cCSA was 1.1 mm2 (95% CI 1.3, 1.5 mm2). Pharyngeal CSA can be accurately calculated from measured pharyngeal pressure and flow by FEA. 相似文献
3.
4.
5.
6.
7.
8.
Structure and expression of the herpes simplex virus type 2 glycoprotein gB gene. 总被引:21,自引:17,他引:4 下载免费PDF全文
L L Stuve S Brown-Shimer C Pachl R Najarian D Dina R L Burke 《Journal of virology》1987,61(2):326-335
The gene for glycoprotein gB2 of herpes simplex virus type 2 strain 333 was cloned, sequenced, and expressed in mammalian cells. The gB2 protein had an overall nucleotide and amino acid sequence homology of 86% with the cognate gB1 protein. However, of the 125 amino acid substitutions or deletions, only 12.5% were conservative replacements. These differences were clustered within an NH2-terminal region, a central region, and a COOH-terminal region, resulting in domains of near identity broken by small regions of marked divergence. Regions of greatest homology included a 90-amino-acid stretch starting at residue 484 and 39 amino acids spanning residues 835 to 873, which cover a rate-of-entry locus mapped to Ala-552 and a syn locus mapped to Arg-857, respectively, in gB1 by Bzik et al. (D. J. Bzik, B. A. Fox, N. A. DeLuca, and S. Person, Virology 133:301-314, 1984). Pellett et al. (P. E. Pellett, K. G. Kousoulas, L. Pereira, and B. Roizman, J. Virol. 53:243-253, 1985) mapped the mutations in three monoclonal antibody-resistant gB1 mutants between amino acids 273 and 443. These epitopes are included in a region of 98 residues identical between gB1 and gB2. The identity of this protein was verified by placing a truncated gene lacking the 303 carboxyl-terminal amino acids of gB2 into mammalian COS and CHO cells. Expression was demonstrated by immunofluorescence and radioimmunoprecipitation. This protein will be purified from the stable CHO cell lines and compared with gB1 for immunogenicity and protective efficacy in animal challenge models. 相似文献
9.
A scheme was developed to classify muscles according to their primary, secondary and tertiary functions, e.g. a muscle which produces primarily a flexion moment may also produce secondary abduction and tertiary internal rotation moments. The functions of muscles crossing the hip and knee joints were computed based upon the changing relative positions of joint centers and muscle origins and insertions during one gait cycle. The function of several of the major muscles crossing the hip and knee joints is reported for the different limb positions corresponding to normal gait. It was found that the amount of force necessary to produce a given moment about a joint was dependent upon the limb position. In addition, the muscle functions changed significantly with limb position. Electrical stimulation of muscles of a paralyzed subject gave qualitative support to the results. 相似文献
10.
Summary A cloned human cDNA for cholinesterase (ChE) was used as a probe for in situ hybridization to spread lymphocyte chromosomes to map the structural human CHE genes to distinct chromosomal regions. The recent genetic linkage assignment of the CHE1 locus of the CHE gene to chromosome 3q was confirmed and further refined to 3q21-q26, close to the genes coding for transferrin (TF) and transferrin receptor (TFRC). The CHE1 allele localizes to a 3q region that is commonly mutated and then associated with abnormal megakaryocyte proliferation in acute myelodysplastic anomalies. In view of earlier findings that ChE inhibitors induce megakaryocytopoiesis in culture, this localization may indicate that ChEs are involved in regulating the differentiation of megakaryocytes. A second site for ChEcDNA hybridization was found on chromosome 16q11-q23, demonstrating that the CHE2 locus of the cholinesterase gene, which directs the production of the common C5 variant of serum ChE, also codes for a structural subunit of the enzyme and is localized on the same chromosome with the haptoglobin (HP) gene, both genes being found on the long arm of chromosome 16. The finding of two sites for ChEcDNA hybridization suggests that the two loci coding for human ChEs may include nonidentical sequences responsible for the biochemical differences between ChE variants. 相似文献