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951.
This study explored a consumer-resource model including reproductive and nonreproductive subpopulations of the consumer to
consider whether resource-dependent reproductive adjustment by the consumer would stabilize consumer-resource dynamics. The
model assumed that decreasing (increasing) resource availability caused reproductive suppression (facilitation), and that
the reproductive consumer had a higher mortality rate than the nonreproductive one (i.e., a trade-off between reproduction
and survival). The model predicted that the variability would be reduced when the consumer had a strong tendency to suppress
reproduction in response to low resource availability or when the cost of reproduction was high, although consumer extinction
became more likely. Furthermore, when the consumer-resource dynamics converged to limit cycles, reproductive adjustment enhanced
the long-term average of the consumer density. It was also predicted that if reproductive suppression enhanced resource consumption
efficiency (i.e., a trade-off between reproduction and foraging), then it would destabilize the system by canceling the stabilizing
effect of the reproductive adjustment itself. These results suggest that it is necessary not only to identify the costs of
reproduction, but also to quantify the changes in individual-level performances due to reproduction in order to understand
the ecological consequences of reproductive adjustment. 相似文献
952.
Liu Y Yu Y Yang S Zeng B Zhang Z Jiao G Zhang Y Cai L Yang R 《Cancer immunology, immunotherapy : CII》2009,58(5):687-697
An elevated number of Gr-1+CD11b+ myeloid-derived suppression cells (MDSCs) has been described in mice and human bearing tumor and associated with immune suppression.
Arginase I production by MDSCs in the tumor environment may be a central mechanism for immunosuppression and tumor evasion.
In this study and before, we found that Gr-1+CD11b+ MDSCs from ascites and spleen of mice bearing ovarian 18D carcinoma express a high level of PD-1, CTLA-4, B7-H1 and CD80
while other co-stimulatory molecules, namely CD40, B7-DC and CD86 are not detected. Further studies showed that PD-1 and CTLA-4
on the Gr-1+CD11b+ MDSCs regulated the activity and expression of arginase I. The blockage and silencing of PD-1, CTLA-4 or both PD-1 and CTLA4
molecules could significantly reduce arginase I activity and expression induced with tumor-associated factor. Similar results
were also observed while their ligands B7-H1 and/or CD80 were blocked or silenced. Furthermore, CD80 deficiency also decreased
the arginase I expression and activity. Antibody blockade or silencing of PD-1, CTLA-4 or both reduced the suppressive potential
of PD-1+CTLA-4+MDSCs. Blockade of PD-1, CTLA-4 or both also slowed tumor growth and improved the survival rate of tumor-bearing
mice. Thus, there may exist a coinhibitory and costimulatory molecules-based immuno-regulating wet among MDSCs.
This research was supported by Nankai University grant, NSFC grant “30771967”, “985” grant,The Ministry of Science and Technology
grant “2006AA020502”“06C26211200695”, Tianjin Grant “07JCZDJC03300” and “06ZHCXSH04800”. 相似文献
953.
The existence and implications of alternative stable states in ecological systems have been investigated extensively within
deterministic models. However, it is known that natural systems are undeniably subject to random fluctuations, arising from
either environmental variability or internal effects. Thus, in this paper, we study the role of noise on the pattern formation
of a spatial predator–prey model with Allee effect. The obtained results show that the spatially extended system exhibits
rich dynamic behavior. More specifically, the stationary pattern can be induced to be a stable target wave when the noise
intensity is small. As the noise intensity is increased, patchy invasion emerges. These results indicate that the dynamic
behavior of predator–prey models may be partly due to stochastic factors instead of deterministic factors, which may also
help us to understand the effects arising from the undeniable susceptibility to random fluctuations of real ecosystems. 相似文献
954.
Kiyoon Kang Sangkyu Park Young Soon Kim Sungbeom Lee Kyoungwhan Back 《Applied microbiology and biotechnology》2009,83(1):27-34
Serotonin derivatives belong to a class of phenylpropanoid amides found at low levels in a wide range of plant species. Representative
serotonin derivatives include feruloylserotonin (FS) and 4-coumaroylserotonin (CS). Since the first identification of serotonin
derivatives in safflower seeds, their occurrence, biological significance, and pharmacological properties have been reported.
Recently, serotonin N-hydroxycinnamoyl transferase (SHT), which is responsible for the synthesis of serotonin derivatives, was cloned from pepper
(Capsicum annuum) and characterized in terms of its enzyme kinetics. Using the SHT gene, many attempts have been made to either increase the
level of serotonin derivatives in transgenic plants or produce serotonin derivatives de novo in microbes by dual expression of key genes such as SHT and 4-coumarate-CoA ligase (4CL). Due to the strong antioxidant activity
and other therapeutic properties of serotonin derivatives, these compounds may have high potential in treatment and prophylaxis,
as cosmetic ingredients, and as major components of functional foods or feeds that have health-improving effects. This review
examines the biosynthesis of serotonin derivatives, corresponding enzymes, heterologous production in plants or microbes,
and their applications. 相似文献
955.
Ectomycorrhizal (ECM) syntheses between four ECM fungi, Laccaria amethystina, Hebeloma mesophaeum, Thelephora terrestris, and Tomentella sp., and Populus maximowiczii seedlings that are known to form ECM at a denuded area of Mt. Usu were performed in volcanic debris in a controlled growth
chamber. The percentage of ECM colonization and seedling growth were determined 3 months after inoculation. Seedlings were
successfully colonized by the inoculated ECM fungi with low contamination ratios. Seedling height and biomass were larger
in the inoculated seedlings than in the control, although the effects of inoculation on seedling growth varied with the ECM
fungus. 相似文献
956.
Ligia Noronha 《EcoHealth》2004,1(2):SU16
This article briefly discusses the evolution of ecosystem approaches, and illustrates the use of ecosystem approaches to assess human health and well-being in a mining context. It discusses the various elements that help distinguish such approaches from other approaches. Well-being here is understood broadly in terms of its “constituents” and “determinants,” of which health is an important constituent. Ecological, health, and social assessments highlighted a number of impacts from mining activity in Goa, India. These generated a list of issues of concern that were validated by stakeholders—community, industry, and government—which served as a basis for the development of tools to track mining-induced changes in health and well-being. The article concludes by reflecting on some of the challenges posed by the use of ecosystem approaches to assessing human health and well-being. 相似文献
957.
Yocum D 《Arthritis research & therapy》2004,6(Z2):S24-S30
Tumor necrosis factor (TNF) antagonists are biologic response modifiers that have significantly improved functional outcomes in patients with rheumatoid arthritis (RA). RA is a progressive disease in which structural joint damage can continue to develop even in the face of symptomatic relief. Before the introduction of biologic agents, the management of RA involved the use of disease-modifying antirheumatic drugs (DMARDs) early in the course of disease. This focus on early treatment, combined with the availability of the anti-TNF agents, has contributed to a shift in treatment paradigms favoring the early and timely use of DMARDs with biologic therapies. Improvement in symptom control does not always equate to a reduction in disease progression or disability. With the emergence of structure-related outcome measures as the primary means for assessing the effectiveness of antirheumatic agents, the regular use of X-rays is recommended for the continued monitoring and evaluation of patients. In addition to the control of symptoms and improvement in physical function, a reduction in erosions and joint-space narrowing should be considered among the goals of therapy, leading to a better quality of life. Adherence to therapy is an important element in optimizing outcomes. Durability of therapy with anti-TNF agents as reported from clinical trials can also be achieved in the clinical setting. Concomitant methotrexate therapy might be important in maintaining TNF antagonist therapy in the long term. Overall, the TNF antagonists have led to improvements in clinical and radiographic outcomes in patients with RA, especially those who have failed to show a complete response to methotrexate. 相似文献
958.
Inflorescence apices are suitable explants for the rapid in vitro propagation of Musa spp. However, the diploid and triploid banana cultivars showed different in vitro responses with respect to the hormone combinations
in Murashige and Skoog medium. The diploid cultivar (Sannachenkadali, AA) induced a maximum number of multiple shoots in 8.9 μM
6-benzyl adenine (BA) whereas the triploid cultivar (Red banana, AAA) exhibited maximum multiplication in 22.2 μM 6-benzyl
adenine. MS medium supplemented with 11.4 μM indole acetic acid and 17.8 μM BA was also suitable for shoot proliferation in
triploid cultivar but not in the diploid cultivar. The regenerated shoots were rooted in Murashige and Skoog basal medium
within 10–15 days. The rooted plantlets were transferred to vermiculite and maintained at a temperature of 25 ± 2°C for 10 days
and then at room temperature (30–32°C) for 2 weeks before transferring to potted soil compost mixture. The plantlets showed
100% survival. 相似文献
959.
A recurrent mutation in type II collagen gene causes Legg-Calvé-Perthes disease in a Japanese family
Miyamoto Y Matsuda T Kitoh H Haga N Ohashi H Nishimura G Ikegawa S 《Human genetics》2007,121(5):625-629
Legg-Calvé-Perthes disease (LCPD) is a common childhood hip disorder characterized by sequential stages of involvement of
the capital femoral epiphyses, including subchondral fracture, fragmentation, re-ossification and healing with residual deformity.
Most cases are sporadic, but familial cases have been described, with some families having multiple affected members. Genetic
factors have been implicated in the etiology of LCPD, but the causal gene has not been identified. We have located a missense
mutation (p.G1170S) in the type II collagen gene (COL2A1) in a Japanese family with an autosomal dominant hip disorder manifesting as LCPD and showing considerable intra-familial
phenotypic variation. This is the first report of a mutation in hereditary LCPD. COL2A1 mutations may be more common in LCPD patients than currently thought, particularly in familial and/or bilateral cases. 相似文献
960.
Jane M. Caffrey Michael C. Murrell Cathleen Wigand Richard McKinney 《Biogeochemistry》2007,82(3):251-264
Coastal marshes represent an important transitional zone between uplands and estuaries. One important function of marshes
is to assimilate nutrient inputs from uplands, thus providing a buffer for anthropogenic nutrient loads. We examined the effects
of nitrogen (N) and phosphorus (P) fertilization on biogeochemical and microbial processes during the summer growing season
in a Spartina patens (Aiton (Muhl.)) marsh in the Narragansett Bay National Estuarine Research Reserve on Prudence Island (RI). Quadruplicate
1 m2 plots were fertilized with N and P additions, N-only, P-only, or no additions. N-only addition significantly stimulated bacterial
production and increased pore water NH4+ and NO3− concentrations. Denitrification rates ranged from 0 to 8 mmol m−2 day−1. Fertilization had no apparent effect on soil oxygen consumption or denitrification measured in the summer in intact cores
due to high core-to-core variation. P fertilization led to increased pore water dissolved inorganic phosphorus (DIP) concentrations
and increased DIP release from soils. In contrast the control and N-only treatments had significant DIP uptake across the
soil-water interface. The results suggest that in the summer fertilization has no apparent effect on denitrification rates,
stimulates bacterial productivity, enhances pore water nutrient concentrations and alters some nutrient fluxes across the
marsh surface. 相似文献