全文获取类型
收费全文 | 6530篇 |
免费 | 627篇 |
国内免费 | 4篇 |
出版年
2023年 | 46篇 |
2021年 | 193篇 |
2020年 | 124篇 |
2019年 | 139篇 |
2018年 | 157篇 |
2017年 | 144篇 |
2016年 | 201篇 |
2015年 | 333篇 |
2014年 | 351篇 |
2013年 | 365篇 |
2012年 | 527篇 |
2011年 | 506篇 |
2010年 | 261篇 |
2009年 | 267篇 |
2008年 | 362篇 |
2007年 | 329篇 |
2006年 | 303篇 |
2005年 | 283篇 |
2004年 | 237篇 |
2003年 | 224篇 |
2002年 | 203篇 |
2001年 | 99篇 |
2000年 | 70篇 |
1999年 | 65篇 |
1998年 | 57篇 |
1997年 | 48篇 |
1996年 | 34篇 |
1995年 | 36篇 |
1994年 | 30篇 |
1993年 | 34篇 |
1992年 | 60篇 |
1991年 | 47篇 |
1990年 | 42篇 |
1989年 | 34篇 |
1988年 | 44篇 |
1987年 | 47篇 |
1986年 | 47篇 |
1985年 | 51篇 |
1984年 | 41篇 |
1983年 | 48篇 |
1982年 | 41篇 |
1981年 | 50篇 |
1980年 | 28篇 |
1979年 | 34篇 |
1978年 | 30篇 |
1977年 | 35篇 |
1976年 | 28篇 |
1975年 | 33篇 |
1974年 | 32篇 |
1972年 | 29篇 |
排序方式: 共有7161条查询结果,搜索用时 187 毫秒
1.
2.
Sandra L. Almeyda Zambrano Eben N. Broadbent Sam Shanee Noga Shanee Anneke Deluycker Michael Steinberg Scott A. Ford Alma Hernndez Jaramillo Robin Fernandez‐Hilario Carolina Lagos Castillo Angelica M. Almeyda Zambrano 《American journal of primatology》2019,81(8)
Habitat loss is one of the main threats to wildlife. Therefore, knowledge of habitat use and preference is essential for the design of conservation strategies and identification of priority sites for the protection of endangered species. The yellow‐tailed woolly monkey (Lagothrix flavicauda Humboldt, 1812), categorized as Critically Endangered on the IUCN Red List, is endemic to montane forests in northern Peru where its habitat is greatly threatened. We assessed how habitat use and preference in L. flavicauda are linked to forest structure and composition. The study took place near La Esperanza, in the Amazonas region, Peru. Our objective was to identify characteristics of habitat most utilized by L. flavicauda to provide information that will be useful for the selection of priority sites for conservation measures. Using presence records collected from May 2013 to February 2014 for one group of L. flavicauda, we classified the study site into three different use zones: low‐use, medium‐use, and high‐use. We assessed forest structure and composition for all use zones using 0.1 ha Gentry vegetation transects. Results show high levels of variation in plant species composition across the three use zones. Plants used as food resources had considerably greater density, dominance, and ecological importance in high‐use zones. High‐use zones presented similar structure to medium‐ and low‐use zones; thus it remains difficult to assess the influence of forest structure on habitat preference. We recommend focusing conservation efforts on areas with a similar floristic composition to the high‐use zones recorded in this study and suggest utilizing key alimentation species for reforestation efforts. 相似文献
3.
S L Rakestraw W E Ford R G Tompkins M A Rodgers W P Thorpe M L Yarmush 《Biotechnology progress》1992,8(1):30-39
A set of anti-melanoma immunoconjugates were prepared which contained chlorin e6: antibody molar ratios of 18.9:1, 11.2:1, 6.8:1, and 1.7:1. All immunoconjugates retained antigen binding activity regardless of the chromophore:antibody substitution ratio that was attained. In contrast, the ground-state absorption spectra of the immunoconjugates showed features which appeared to be dependent on the chromophore:antibody molar ratio. In addition, the quantum yield of singlet oxygen generated by the conjugated chromophores was observed to be significantly less than that observed with the unbound dye. Time-resolved absorbance spectroscopy of the chromophore excited triplet state indicated that the loss of singlet oxygen quantum yield resulted from diminished chromophore triplet yield. Analysis of data obtained from in vitro photolysis of target melanoma cells, in combination with that obtained from the immunochemical and photochemical studies, indicates that the observed immunoconjugate phototoxicity can be reasonably quantitatively represented by (1) the ability of the immunoconjugate to bind SK-MEL-2 cell surface antigen, (2) the amount of chromophore localized at the target cells by immunoconjugate binding, (3) the delivered dose of light at 634 nm, and (4) the singlet oxygen quantum yield of the antibody-bound photosensitizer. Though these data argue strongly for photolysis by the cumulative dosage of singlet oxygen at the cell membrane, nonetheless, the concurrent photoinduced release of other cytotoxic agents should not be ruled out. 相似文献
4.
5.
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
6.
R. Munro Ford 《BMJ (Clinical research ed.)》1958,1(5075):887-888
7.
8.
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
9.
10.