全文获取类型
收费全文 | 25351篇 |
免费 | 2157篇 |
国内免费 | 1009篇 |
出版年
2024年 | 47篇 |
2023年 | 595篇 |
2022年 | 621篇 |
2021年 | 1181篇 |
2020年 | 1026篇 |
2019年 | 1279篇 |
2018年 | 1152篇 |
2017年 | 904篇 |
2016年 | 962篇 |
2015年 | 1122篇 |
2014年 | 1776篇 |
2013年 | 2297篇 |
2012年 | 1340篇 |
2011年 | 1544篇 |
2010年 | 1081篇 |
2009年 | 1165篇 |
2008年 | 1177篇 |
2007年 | 1130篇 |
2006年 | 990篇 |
2005年 | 901篇 |
2004年 | 804篇 |
2003年 | 588篇 |
2002年 | 548篇 |
2001年 | 424篇 |
2000年 | 325篇 |
1999年 | 327篇 |
1998年 | 327篇 |
1997年 | 291篇 |
1996年 | 219篇 |
1995年 | 194篇 |
1994年 | 236篇 |
1993年 | 179篇 |
1992年 | 178篇 |
1991年 | 122篇 |
1990年 | 120篇 |
1989年 | 82篇 |
1988年 | 95篇 |
1987年 | 65篇 |
1986年 | 60篇 |
1985年 | 163篇 |
1984年 | 151篇 |
1983年 | 106篇 |
1982年 | 113篇 |
1981年 | 103篇 |
1980年 | 85篇 |
1979年 | 72篇 |
1978年 | 59篇 |
1977年 | 45篇 |
1976年 | 35篇 |
1974年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.
Yusuke Nakamura Michio Ogawa Takahiro Nishide Mitsuru Emi Goro Kosaki Seiichi Himeno Kenichi Matsubara 《Gene》1984,28(2):263-270
The nucleotide sequences of the cloned human salivary and pancreatic α-amylase cDNAs correspond to the continuous mRNA sequences of 1768 and 1566 nucleotides, respectively. These include all of the amino acid coding regions. Salivary cDNA contains 200 bp in the 5′-noncoding region and 32 in the 3′-noncoding region. Pancreatic cDNA contains 3 and 27 bp of 5′- and 3′-noncoding regions, respectively. The nucleotide sequence humology of the two cDNAs is 96% in the coding region, and the predicted amino acid sequences are 94% homologous.Comparison of the sequences of human α-amylase cDNAs with those previously obtained for mouse α-amylase genes (Hagenbuchle et al., 1980; Schibler et al., 1982) showed the possibility of gene conversion between the two genes of human α-amylase. 相似文献
22.
23.
24.
25.
Major knowledge gaps exist with respect to light-quality regimes in the coastal-zone Strandzha Quercus frainetto (Q.f.) forest region adjoining the southern Bulgarian Black Sea. This paper presents preliminary results that help narrow these
gaps. In conjunction with leaf area index (LAI) field campaigns we undertook measurements with an array of 7 broad-band (ca
40 nm) sensors covering the range 0.40–0.94 μm, plus 1 sensor for UVB (0.297 μm peak) and 1 for photosynthetically active
radiation (PAR). Measurements focused on inside-forest shade conditions at sites 0 to ca 15 km from the Black Sea and at altitudes
up to ca 120 m above sea level. Some of the sites were also studied using a high-resolution spectroradiometer. A sequential
measuring strategy was necessary. This involves potentially large uncertainties, here addressed through estimations of the
variability around the sinusoidal course of daylight. Light-quality regimes were found to be in general support of earlier
studies of deciduous forests. Our data from the broad-band sensors and from the spectroradiometer are mutually supportive.
They indicate a stronger red-shift below Q.f. canopies than below canopies in enclaves dominated by Fagus orientalis and Pinus sylvestris. Transmission in the range 0.50–0.55 μm increases beneath the three types of canopies, most pronounced in the Q.f. case. Analysis of relationships between the inside-forest to open-field irradiance ratio and LAI supports the use of Beer’s
Law. We found a fairly strong relationship between the red (0.66 μm) to far-red (0.73 μm) irradiance ratios (R/FR) and LAI
for the Q.f. forest. In quantitative terms, the result is new for this Q.f. region, and suggests further research to explore whether a two-sensor approach (0.66 and 0.73 μm) might offer possibilities
for further low-cost mapping of the spatio-temporal patterns of R/FR and LAI in Strandzha. Such mapping would assist in further
studies of the region’s forest biogeochemistry and vitality. 相似文献
26.
BackgroundComparative evidence on the burden, trend, and risk factors of cancer is limited. Using data from the Global Burden of Disease (GBD) study, we aimed to assess cancer burden – incidence, prevalence, mortality, disability-adjusted life years (DALYs) – and attributable risk factors for Australia between 1990 and 2015, and to compare them with those of 34 members of the Organisation for Economic Co-operation and Development (OECD).MethodsThe general GBD cancer estimation methods were used with data input from vital registration systems and cancer registries. A comparative risk assessment approach was used to estimate the population-attributable fractions due to risk factors.ResultsIn 2015 there were 198,880 (95% uncertainty interval [UI]: 183,908–217,365) estimated incident cancer cases and 47,562 (95% UI: 46,061–49,004) cancer deaths in Australia. Twenty-nine percent (95% UI: 28.2–29.8) of total deaths and 17.0% (95% UI: 15.0–19.1) of DALYs were caused by cancer in Australia in 2015. Cancers of the trachea, bronchus and lung, colon and rectum, and prostate were the most common causes of cancer deaths. Thirty-six percent (95% UI: 33.1–37.9) of all cancer deaths were attributable to behavioral risks. The age-standardized cancer incidence rate (ASIR) increased between 1990 and 2015, while the age-standardized cancer death rate (ASDR) decreased over the same period. In 2015, compared to 34 other OECD countries Australia ranked first (highest) and 24th based on ASIR and ASDR, respectively.ConclusionThe incidence of cancer has increased over 25 years, and behavioral risks are responsible for a large proportion of cancer deaths. Scaling up of prevention (using strategies targeting cancer risk factors), early detection, and treatment of cancer is required to effectively address this growing health challenge. 相似文献
27.
Andrew J. Sutherland-Smith 《Biophysical reviews》2011,3(1):15-23
The cytoskeleton framework is essential not only for cell structure and stability but also for dynamic processes such as cell migration, division and differentiation. The F-actin cytoskeleton is mechanically stabilised and regulated by various actin-binding proteins, one family of which are the filamins that cross-link F-actin into networks that greatly alter the elastic properties of the cytoskeleton. Filamins also interact with cell membrane-associated extracellular matrix receptors and intracellular signalling proteins providing a potential mechanism for cells to sense their external environment by linking these signalling systems. The stiffness of the external matrix to which cells are attached is an important environmental variable for cellular behaviour. In order for a cell to probe matrix stiffness, a mechanosensing mechanism functioning via alteration of protein structure and/or binding events in response to external tension is required. Current structural, mechanical, biochemical and human disease-associated evidence suggests filamins are good candidates for a role in mechanosensing. 相似文献
28.
F H Stephenson 《Gene》1985,35(3):313-320
29.
30.