全文获取类型
收费全文 | 98645篇 |
免费 | 622篇 |
国内免费 | 901篇 |
专业分类
100168篇 |
出版年
2022年 | 34篇 |
2021年 | 67篇 |
2019年 | 42篇 |
2018年 | 11875篇 |
2017年 | 10713篇 |
2016年 | 7519篇 |
2015年 | 707篇 |
2014年 | 473篇 |
2013年 | 541篇 |
2012年 | 4451篇 |
2011年 | 13073篇 |
2010年 | 12125篇 |
2009年 | 8344篇 |
2008年 | 10015篇 |
2007年 | 11592篇 |
2006年 | 500篇 |
2005年 | 781篇 |
2004年 | 1188篇 |
2003年 | 1254篇 |
2002年 | 1041篇 |
2001年 | 487篇 |
2000年 | 406篇 |
1999年 | 203篇 |
1998年 | 104篇 |
1997年 | 79篇 |
1996年 | 61篇 |
1995年 | 55篇 |
1994年 | 61篇 |
1993年 | 81篇 |
1992年 | 143篇 |
1991年 | 173篇 |
1990年 | 112篇 |
1989年 | 113篇 |
1988年 | 139篇 |
1987年 | 112篇 |
1986年 | 91篇 |
1985年 | 85篇 |
1984年 | 67篇 |
1983年 | 80篇 |
1982年 | 47篇 |
1980年 | 37篇 |
1979年 | 49篇 |
1978年 | 45篇 |
1976年 | 31篇 |
1975年 | 41篇 |
1974年 | 32篇 |
1973年 | 37篇 |
1972年 | 266篇 |
1971年 | 308篇 |
1970年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Johannes W. S. A. Osterloh Arjan C. Videler Gina M. P. Rossi Sebastiaan P. J. van Alphen 《Tijdschrift voor gerontologie en geriatrie》2018,49(5):210-212
Behavioural counselling by nurses can enhance quality of life in elderly with a personality disorder. Although nurses have a crucial role in day-to-day treatment, there is a lack of evidence-based approaches. Based on the cognitive therapy, the treatment protocol Cognitive Model for Behavioural Interventions (CoMBI) provides an alternative nursing approach for personality disorders. 相似文献
133.
Background
Understanding the adaptive changes that alter the function of proteins during evolution is an important question for biology and medicine. The increasing number of completely sequenced genomes from closely related organisms, as well as individuals within species, facilitates systematic detection of recent selection events by means of comparative genomics. 相似文献134.
Numerous empirical studies have examined ontogenetic trajectories in plant defenses but only a few have explored the potential
mechanisms underlying those patterns. Furthermore, most documented ontogenetic trajectories in plant defenses have generally
concentrated on aboveground tissues; thus, our knowledge regarding whole plant trends in plant defenses throughout development
or potential allocation constraints between growth and defenses is limited. Here, we document changes in plant biomass, nutritional
quality and chemical defenses for below- and aboveground tissues across seven age classes of Plantago lanceolata (Plantaginaceae) to evaluate: (1) partial and whole plant ontogenetic trajectories in constitutive chemical defenses and
nutritional quality, and (2) the role of resource allocation constraints, namely root:shoot (R:S) ratios, in explaining whole
plant investment in chemical defenses over time. Overall investment in iridoid glycosides (IGs) significantly increased, while
water and nitrogen concentrations in shoot tissues decreased with plant age. Significant variation in IG content between shoot
and root tissues across development was observed: allocation of IGs into root tissues linearly increased from younger to older
plants, while non-linear shifts in allocation of IGs during ontogeny were observed for shoot tissues. Finally, R:S ratios
only weakly explained overall allocation of resources into defenses, with young stages showing a positive relationship, while
older stages showed a negative relationship between R:S ratios and IG concentrations. Ontogenetic trajectories in plant quality
and defenses within and among plant tissues can strongly influence insect herbivores’ performance and/or predation risk; thus,
they are likely to play a significant role in mediating species interactions. 相似文献
135.
Eric Letouzé Yves Allory Marc A Bollet François Radvanyi Frédéric Guyon 《Genome biology》2010,11(7):R76
We present a computational method, TuMult, for reconstructing the sequence of copy number changes driving carcinogenesis,
based on the analysis of several tumor samples from the same patient. We demonstrate the reliability of the method with simulated
data, and describe applications to three different cancers, showing that TuMult is a valuable tool for the establishment of
clonal relationships between tumor samples and the identification of chromosome aberrations occurring at crucial steps in
cancer progression. 相似文献
136.
137.
Dinh-Toi Chu Yang Tao Le Hoang Son Duc-Hau Le 《Journal of physiology and biochemistry》2016,73(3):315-321
Recent investigations have showed that the functional thermogenic adipocytes are present in both infants and adult humans. Accumulating evidence suggests that the coexistence of classical and inducible brown (brite) adipocytes in humans at adulthood and these adipocytes function to generate heat from energy resulting in reducing body fat and improving glucose metabolism. Human thermogenic adipocytes can be differentiated in vitro from stem cells, cell lines, or adipose stromal vascular fraction. Pre-activated human brite adipocytes in vitro can maintain their thermogenic function in normal or obese immunodeficient mice; therefore, they improve glucose homeostasis and reduce fat mass in obese animals. These key findings have opened a new door to use in vitro thermogenic adipocytes as a cell therapy to prevent obesity and related disorders. Thus, this paper intends to highlight our knowledge in aspects of in vitro human brite/brown adipocytes for the further studies. 相似文献
138.
Zhang H Cai J Dong J Zhang D Huang L Xu Z Cen P 《Applied microbiology and biotechnology》2011,92(2):295-303
Poly (β-l-malic acid) (PMLA) is a water-soluble polyester with many attractive properties in chemical industry and medicine development.
However, the low titer of PMLA in the available producer strains limits further industrialization efforts and restricts its
many potential applications. In order to solve this problem, a new strain with the distinguished high productivity of PMLA
was isolated from fresh plants samples. It was characterized as the candidate of Aureobasidium pullulans based on the morphology and phylogenetic analyses of the internal transcribed spacer sequences. After the optimization of
culture conditions, the highest PMLA concentration (62.27 g l−1) could be achieved in the shake flask scale. In addition, the contribution of the carbon flux to exopolysaccharide (EPS)
and PMLA could be regulated by the addition of CaCO3 in the medium. This high-level fermentation process was further scaled up in the 10 l benchtop fermentor with a high PMLA
concentration (57.2 g l−1) and productivity (0.35 g l−1 h−1), which are the highest level in all the literature. Finally, the suitable acid hydrolysis conditions of PMLA were also investigated
with regard to the production of l-malic acid, and the kinetics of PMLA acid hydrolysis was modeled to simulate the whole degradation process. The present work
paved the road to produce this multifunctional biomaterial (PMLA) at industrial scale and promised one alternative method
to produce l-malic acid in the future. 相似文献
139.
Ines Hammami Bassem Jaouadi Abir Ben Bacha Ahmed Rebai Samir Bejar Xavier Nesme Ali Rhouma 《Biotechnology and Bioprocess Engineering》2012,17(1):41-49
Bacillus subtilis strain 14B was used to produce a novel antimicrobial peptide (bacteriocin) called Bac 14B. Pure bacteriocin was obtained
after heat and acidic treatments (80°C and pH 4), precipitation by ammonium sulfate, and chromatography on Sephadex G-50 and
Mono Q Sepharose columns. Based on MALDI-TOF mass spectrometry analysis, purified Bac 14B is a monomer protein with a molecular
mass of 20110.13 Da. N-terminal sequencing allowed for the straightforward identification of its first 12 residues, which
were of a pure bacteriocin. It also revealed that this bacteriocin contained a unique sequence, namely M-L-K-A-N-L-Q-N-P-L-N-A,
suggesting the identification of a novel compound. Bac 14B was stable for 1 h at temperatures up to 80°C and pH of 4 ∼ 8.
It also proved sensitive to various proteases, which demonstrated its protein nature. Bac 14B displayed a bacteriolytical
mode of action and a broad range of inhibitory spectra toward Gram-positive and -negative pathogens. Interestingly, based
on conventional agronomic seed vigor parameters, the application of Bac 14B (500 activity units/mL) to various crops revealed
that this bacteriocin was a potent exogenous enhancer of growth that stimulated the seedling vigor of tomatoes and muskmelons.
Compared to those of the control, the germination percentage, shoot weight, shoot height, and root length were all significantly
enhanced in Bac 14B-treated plant seeds. Bac 14B also exhibited effective disinfectant properties against a wide range of
seedborne diseases and significant effects on the control of damping off diseases, particularly at the pregermination stage.
It also proved to be effective against root rot diseases caused by Alternaria solani and other bacterial seedborne pathogens such as wilt diseases. The findings indicate that Bac 14B is the first B. subtilis-produced bacteriocin ever reported to exhibit such promising biological properties. 相似文献
140.
Ravinder Kaur Grewal Monika Lulsdorf Janine Croser Sergio Ochatt Albert Vandenberg Thomas D. Warkentin 《Plant cell reports》2009,28(8):1289-1299
This is the first report on the production of double-haploid chickpea embryos and regenerated plants through anther culture
using Canadian cultivar CDC Xena (kabuli) and Australian cultivar Sonali (desi). Maximum anther induction rates were 69% for
Sonali and 63% for CDC Xena. Under optimal conditions, embryo formation occurred within 15–20 days of culture initiation with
2.3 embryos produced per anther for CDC Xena and 2.0 embryos per anther for Sonali. For anther induction, the following stress
treatments were used: (1) flower clusters were treated at 4°C for 4 days, (2) anthers were subjected to electric shock treatment
of three exponentially decaying pulses of 50–400 V with 25 μF capacitance and 25 Ω resistance, (3) anthers were centrifuged
at 168–1,509g for 2–15 min, and finally (4) anthers were cultured for 4 days in high-osmotic pressure (563 mmol) liquid medium. Anthers
were then transferred to a solid embryo development medium and, 15–20 days later, embryo development was observed concomitant
with a small amount of callus growth of 0.1–3 mm. Anther-derived embryos were regenerated on plant regeneration medium. Electroporation
treatment of anthers enhanced root formation, which is often a major hurdle in legume regeneration protocols. Cytological
studies using DAPI staining showed a wide range of ploidy levels from haploid to tetraploid in 10–30-day-old calli. Flow cytometric
analysis of calli, embryos and regenerated plants showed haploid profiles and/or spontaneous doubling of the chromosomes during
early regeneration stages. 相似文献