全文获取类型
收费全文 | 5644篇 |
免费 | 548篇 |
国内免费 | 4篇 |
出版年
2023年 | 46篇 |
2022年 | 89篇 |
2021年 | 182篇 |
2020年 | 112篇 |
2019年 | 135篇 |
2018年 | 156篇 |
2017年 | 138篇 |
2016年 | 192篇 |
2015年 | 317篇 |
2014年 | 327篇 |
2013年 | 330篇 |
2012年 | 479篇 |
2011年 | 475篇 |
2010年 | 251篇 |
2009年 | 239篇 |
2008年 | 324篇 |
2007年 | 294篇 |
2006年 | 279篇 |
2005年 | 239篇 |
2004年 | 219篇 |
2003年 | 170篇 |
2002年 | 159篇 |
2001年 | 65篇 |
2000年 | 42篇 |
1999年 | 46篇 |
1998年 | 38篇 |
1997年 | 29篇 |
1996年 | 34篇 |
1995年 | 22篇 |
1994年 | 28篇 |
1993年 | 26篇 |
1992年 | 42篇 |
1991年 | 50篇 |
1990年 | 45篇 |
1989年 | 38篇 |
1988年 | 38篇 |
1987年 | 33篇 |
1986年 | 28篇 |
1985年 | 25篇 |
1984年 | 26篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 27篇 |
1980年 | 19篇 |
1979年 | 27篇 |
1977年 | 18篇 |
1976年 | 21篇 |
1975年 | 15篇 |
1974年 | 23篇 |
1973年 | 17篇 |
排序方式: 共有6196条查询结果,搜索用时 15 毫秒
1.
Eliot C. Bush Anne E. Clark Chris M. DeBoever Lillian E. Haynes Sidra Hussain Singer Ma Matthew M. McDermott Adam M. Novak John S. Wentworth 《PloS one》2012,7(11)
A significant proportion of enzymes display cooperativity in binding ligand molecules, and such effects have an important impact on metabolic regulation. This is easiest to understand in the case of positive cooperativity. Sharp responses to changes in metabolite concentrations can allow organisms to better respond to environmental changes and maintain metabolic homeostasis. However, despite the fact that negative cooperativity is almost as common as positive, it has been harder to imagine what advantages it provides. Here we use computational models to explore the utility of negative cooperativity in one particular context: that of an inhibitor binding to an enzyme. We identify several factors which may contribute, and show that acting together they can make negative cooperativity advantageous. 相似文献
2.
3.
Emily Olfson Catherine E. Cottrell Nicholas O. Davidson Christina A. Gurnett Jonathan W. Heusel Nathan O. Stitziel Li-Shiun Chen Sarah Hartz Rakesh Nagarajan Nancy L. Saccone Laura J. Bierut 《PloS one》2015,10(9)
The American College of Medical Genetics and Genomics (ACMG) recommends that clinical sequencing laboratories return secondary findings in 56 genes associated with medically actionable conditions. Our goal was to apply a systematic, stringent approach consistent with clinical standards to estimate the prevalence of pathogenic variants associated with such conditions using a diverse sequencing reference sample. Candidate variants in the 56 ACMG genes were selected from Phase 1 of the 1000 Genomes dataset, which contains sequencing information on 1,092 unrelated individuals from across the world. These variants were filtered using the Human Gene Mutation Database (HGMD) Professional version and defined parameters, appraised through literature review, and examined by a clinical laboratory specialist and expert physician. Over 70,000 genetic variants were extracted from the 56 genes, and filtering identified 237 variants annotated as disease causing by HGMD Professional. Literature review and expert evaluation determined that 7 of these variants were pathogenic or likely pathogenic. Furthermore, 5 additional truncating variants not listed as disease causing in HGMD Professional were identified as likely pathogenic. These 12 secondary findings are associated with diseases that could inform medical follow-up, including cancer predisposition syndromes, cardiac conditions, and familial hypercholesterolemia. The majority of the identified medically actionable findings were in individuals from the European (5/379) and Americas (4/181) ancestry groups, with fewer findings in Asian (2/286) and African (1/246) ancestry groups. Our results suggest that medically relevant secondary findings can be identified in approximately 1% (12/1092) of individuals in a diverse reference sample. As clinical sequencing laboratories continue to implement the ACMG recommendations, our results highlight that at least a small number of potentially important secondary findings can be selected for return. Our results also confirm that understudied populations will not reap proportionate benefits of genomic medicine, highlighting the need for continued research efforts on genetic diseases in these populations. 相似文献
4.
Ernest I. Onyishi Piotr Sorokowski Agnieszka Sorokowska R. Nathan Pipitone 《Evolution and human behavior》2012,33(6):771-774
Previous research has demonstrated that having more children decreases marital satisfaction among parents. However, the universality of these findings is limited since the vast majority of the studies have been conducted in Western countries. In the present study, 374 people from the Igbo ethnic group (Nigeria) were assessed for levels of marital satisfaction and the number of children. In contrast to almost all previous findings, we found a positive relationship between the number of children and marital satisfaction among parents. Number of children was the strongest predictor of marital satisfaction even when compared to other variables like wealth and education. Our results suggest that the negative relationship between the number of children and marital satisfaction is not culturally universal and probably only characterizes developed, individualistic Western countries. We discuss our findings from a sociocultural and evolutionary perspective. 相似文献
5.
J. K. Bush 《Plant Ecology》2006,183(2):215-225
This study evaluated the relationships among soil moisture, soil salinity, and soil oxygen on the growth of Helianthus paradoxus (Asteraceae), a threatened inland salt marsh species of western North America. The study was conducted in large growth boxes
(1×2×0.3 m) tilted at an angle to achieve a saturated to dry water gradient similar to that found in the marsh. This experimental
design allowed the evaluation of major abiotic factors (soil moisture and soil salinity) which have been shown to be potentially
important for this species, while removing major biotic factors, such as competition from other community dominants. Maximum
aboveground biomass occurred in the middle rows of the boxes, where surface soil water was reduced and subsurface soil water
was intermediate in the gradient. Regression analyses indicated that H. paradoxus would grow best where surface soil water is approximately 5%, subsurface soil water ranges from 20 to 30%, and where surface
soil salinity is less than 0.5 g kg−1. Edaphic variables, particularly soil moisture and soil salinity, affect the growth of H. paradoxus. Data presented here suggest that the survival of this species depends on maintenance of the hydrologic regime. 相似文献
6.
7.
8.
Eva Decru Nathan Vranken Pedro H. N. Bragança Jos Snoeks Maarten Van Steenberge 《Journal of fish biology》2020,96(5):1186-1201
Based on literature, museum collections and three recent expeditions, an annotated species list of the Lake Edward, East Africa, drainage system is presented, excluding the endemic haplochromines. A total of 34 non-Haplochromis species belonging to 10 families and 21 genera are recorded from the system. Three of these are endemic and two others have been introduced in the region. Six species are new records for the Lake Edward system. A species accumulation curve indicates that we probably covered most of the non-Haplochromis species in the area sampled during the recent expeditions, but undetected species might still be present in the Congolese part of the system, which is poorly sampled. A comparison of the species list with those of neighbouring basins confirmed the placement of the Lake Edward system within the east-coast ichthyofaunal province. 相似文献
9.
Spectroscopic data and conformational energy calculations are reported for eight oligosaccharides from ovarian cyst mucins and from human milk, the nonreducing terminals of which have fucose (α1 → 2)galactose linked either (β1 → 3) (type I) or (β1 → 4)(type II) to N-acetylglucosamine or in (β1 → 3) linkage to galactosaminitol. The fully assigned proton nmr spectra are reported along with nuclear Overhauser enhancement (NOE) data. Amide proton coupling constants and vacuum-uv CD spectra provide information on the amide plane orientation and amide environment. Our results imply that the fucosidic dihedral angles are similar for all three cases and that the substantial differences in the chemical shifts of the fucosyl protons of type I, type II, and 3-ol chains result from different perturbations by the amide group of the residue to which the β-galactose is linked. Stereopair diagrams of conformational models for both type I and II H chains are presented that are consistent with NOE, coupling constants, conformational energy calculations, and the CD data. While the temperature dependence of the observed NOE of penta- and hexasaccharides indicates that their rotational correlation times are strongly temperature dependent, we conclude that the conformations are essentially independent of temperature. 相似文献
10.
Techniques are described for capturing and marking redtail monkeys (Cercopithecus ascanius). An air-powered darting rifle and syringe darts loaded with a Ketamine-Rompun mixture were used for capture. Ketamine was used for maintaining anesthesia. Monkeys were darted 48 times and captured 27 times. In 24 of the 27 captures, the monkeys were released unharmed. Adult males were marked with radiotransmitters attached to collars of nylon webbing. Females received nylon webbing collars with colorcoded plastic washers for identification. 相似文献