全文获取类型
收费全文 | 7429篇 |
免费 | 530篇 |
国内免费 | 1篇 |
出版年
2023年 | 98篇 |
2022年 | 61篇 |
2021年 | 136篇 |
2020年 | 131篇 |
2019年 | 141篇 |
2018年 | 247篇 |
2017年 | 233篇 |
2016年 | 316篇 |
2015年 | 292篇 |
2014年 | 347篇 |
2013年 | 586篇 |
2012年 | 479篇 |
2011年 | 502篇 |
2010年 | 429篇 |
2009年 | 297篇 |
2008年 | 268篇 |
2007年 | 254篇 |
2006年 | 247篇 |
2005年 | 188篇 |
2004年 | 201篇 |
2003年 | 183篇 |
2002年 | 159篇 |
2001年 | 128篇 |
2000年 | 131篇 |
1999年 | 100篇 |
1998年 | 85篇 |
1997年 | 66篇 |
1996年 | 72篇 |
1995年 | 73篇 |
1994年 | 76篇 |
1993年 | 65篇 |
1992年 | 68篇 |
1991年 | 74篇 |
1990年 | 61篇 |
1989年 | 58篇 |
1988年 | 56篇 |
1987年 | 43篇 |
1986年 | 45篇 |
1985年 | 66篇 |
1984年 | 56篇 |
1983年 | 52篇 |
1982年 | 52篇 |
1981年 | 55篇 |
1980年 | 40篇 |
1979年 | 39篇 |
1977年 | 40篇 |
1975年 | 40篇 |
1974年 | 42篇 |
1972年 | 42篇 |
1969年 | 40篇 |
排序方式: 共有7960条查询结果,搜索用时 296 毫秒
1.
2.
El-Hadi Ibrahim Adil Denizli Sema Bekta
mer Gen Erhan Pi
kin 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,720(1-2):217-224
Poly(2-hydroxyethylmethacrylate–ethyleneglycoldimethacrylate) [poly(HEMA–EGDMA)] microspheres carrying Cibacron Blue F3GA and/or thionein were prepared and used for the removal of cadmium ions Cd(II) from human plasma. The poly(HEMA–EGDMA) microspheres, in the size range of 150–200 μm in diameter, were produced by a modified suspension copolymerization of HEMA and EGDMA. The reactive triazinyl dye-ligand Cibacron Blue F3GA was then covalently incorporated into the microspheres. The maximum dye incorporation was 16.5 μmol/g. Then, thionein was bound onto the Cibacron Blue F3GA-incorporated microspheres under different conditions. The maximum amount of thionein bound was 14.3 mg/g. The maximum amounts of Cd(II) ions removed from human plasma by poly(HEMA–EGDMA)–Cibacron Blue F3GA and poly(HEMA–EGDMA)–Cibacron Blue F3GA–thionein were of 17.5 mg/g and 38.0 mg/g, respectively. Cd(II) ions could be repeatedly adsorbed and desorbed with both types of microspheres without significant loss in their adsorption capacity. 相似文献
3.
The production of L-lysine fromDL-α-amino-ε-caprolactam (DL-ACL) by new strains producingL-α-amino-ε-caprolactamase and aminocaprolactam racemase is described. Optimal conditions for hydrolysis ofL-ACL byCryptococcus sp. and for racemization of ACL by cells of a strain isolated in nature and identified asPseudomonas sp. were determined. Synthesis ofL-α-amino-ε-caprolactamase is induced byDL-ACL orL-lysine with the same effectivity. A positive effect of phosphates (potassium salts) on reduction of the induction lag was
detected, the synthesis of this enzyme was found to be repressed by glucose and some possibilities of the reversion of this
repressive effect were demonstrated. Under conditions optimal for the production of both enzymes a quantitative theoretical
conversion of 10 % aqueousDL-ACL toL-lysine by a mixture of native cells in a mass ratio of 1: 2 (producer of ACL-hydrolase to producer of ACL-racemase) occurred
in 8 h at 40 °C and pH 8.0 相似文献
4.
5.
Allopatric isolation in glacial refugia has caused differentiation and speciation in many taxa globally. In this study, we investigated the nuclear and mitochondrial genetic differentiation of the long fingered bat, Myotis capaccinii during the ice ages in south-eastern Europe and Anatolia. The mitochondrial DNA (mtDNA) analyses indicated a suture zone similar to those recorded in other animal species, including bats, suggesting the association of more than one refugium with the region. Contrary to most of the other species where a suture zone was seen in Anatolia, for M. capaccinii the geographical location of the genetic break was in south-eastern Europe. This mitochondrial differentiation was not reflected in the nuclear microsatellites, however, suggesting that the lack of contact during the ice ages did not result in reproductive isolation. Hence taxonomically, the two mitochondrial clades cannot be treated as separate species. 相似文献
6.
7.
DNA was efficiently and quantitatively isolated from extremely small quantities of mycelia (0.1–10 mg) of different phytopathogenic
moulds by grinding freeze-dried mycelia with glass beads and then using a commercial DNA extraction kit. The efficiency of
disruption of the mycelia and the quantitative DNA extraction was proved by microscopy and the quantification of isolated
DNA by real time PCR.
Presented at the 27th Mykotoxin-Workshop, Dortmund, Germany, June 13–15, 2005
Financial support: German Research Foundation (DFG grant Pr 708/2). J.M. thanks the Cusanuswerk for a doctoral scholarship 相似文献
8.
J Matousek 《Animal genetics》1994,25(Z1):45-50
Injection of mouse scrotum with the bull seminal ribonuclease (BS RNase) isolated from bull seminal vesicle fluid inhibited spermatogenesis and caused a decrease in the weight of the testes. Long-term injection of BS RNase evoked the production of antibodies which reached the titre 524448. These antibodies did not prevent the aspermatogenic action of BS RNase in vivo when a twofold higher amount of this enzyme was injected into mouse scrotum. Aspermatogenesis was reversible in both the first and second part of the experiment. During the period of aspermatogenesis the males were sterile. Increasing the amount of BS RNase injections in the second part of experiments caused aspermatogenesis around 3 months. No malformations were observed among offspring of males recovered from the first stage of aspermatogenesis. The antigen—antibody complex prepared in vitro and injected into testes of mice evoked the same degree of aspermatogenesis as the enzyme itself. 相似文献
9.
Jan Suchá?ek Petr Sed’a Václav Friedrich Renata Wachowiak-Smolíková Mark P. Wachowiak 《PloS one》2016,11(11)
Media, and particularly TV media, have a great impact on the general public. In recent years, spatial patterns of information and the relevance of intangible geographies have become increasingly important. Gatekeeping plays a critical role in the selection of information that is transformed into media. Therefore, gatekeeping, through national media, also co-forms the generation of mental maps. In this paper, correspondence analysis (a statistical method) combined with cloud lines (a new visual analytics technique) is used to analyze how individual major regional events in one of the post-communist countries, the Czech Republic, penetrate into the media on a national scale. Although national news should minimize distortions about regions, this assumption has not been verified by our research. Impressions presented by the media of selected regions that were markedly influenced by one or several events in those regions demonstrate that gatekeepers, especially news reporters, functioned as a filter by selecting only a few specific, and in many cases, unusual events for dissemination. 相似文献
10.
CECILIA A. L. DAHLSJÖ 《Ecological Entomology》2016,41(6):741-744
1. Termites are one of the most important invertebrate ecosystem engineers in tropical regions, which may be quantified using termite biomass data. However, biomass data are particularly difficult to collect as they rely on termites being weighed in the field, which may neither be possible nor convenient. Local scale linear regression models, based on termite head widths (mm) and body masses (mg), have been used in the past to estimate termite biomass using head width and abundance data. However, these models represent very limited numbers of termite taxa from single sites. In the present study, I provide one of the most representative linear regression models available based on 90 samples from three different countries (Peru, Kenya, and Malaysia). 2. Although the linear regression model under‐ or overestimated body weights of taxa with characteristic features (e.g. large heads of Odontotermes workers or elongated abdomens of Kalotermitidae) it provides a robust method for estimating termite biomass at the community level. Additionally, while there are limitations related to the general model, which may be solved by focusing on taxa specific data and the use of higher accuracy equipment, it is the first model to facilitate termite biomass estimates using the head with and abundance data only. 3. This study encourages the use of termite biomass data to gain a better understanding of termites in ecosystem processes and calls for comparative data to be gathered for the purpose of creating models that may be representative of the variability among termite taxa. 相似文献