全文获取类型
收费全文 | 1209篇 |
免费 | 54篇 |
国内免费 | 1篇 |
专业分类
1264篇 |
出版年
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 26篇 |
2020年 | 19篇 |
2019年 | 18篇 |
2018年 | 28篇 |
2017年 | 18篇 |
2016年 | 16篇 |
2015年 | 49篇 |
2014年 | 54篇 |
2013年 | 94篇 |
2012年 | 98篇 |
2011年 | 102篇 |
2010年 | 52篇 |
2009年 | 44篇 |
2008年 | 57篇 |
2007年 | 80篇 |
2006年 | 72篇 |
2005年 | 57篇 |
2004年 | 53篇 |
2003年 | 52篇 |
2002年 | 38篇 |
2001年 | 20篇 |
2000年 | 17篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1972年 | 3篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有1264条查询结果,搜索用时 15 毫秒
81.
Veerasamy Sejian Rajendra Swaroop Srivastava 《Journal of physiology and biochemistry》2010,66(4):339-349
The purpose of the investigation was to observe the pineal–adrenal–immune system relationships and their influence on non-specific
immune response in female goats under short-term thermal stress. Six female goats had been exposed to 40°C and 60% relative
humidity in the psychrometric chamber for 17 days. Blood samples were obtained on days 0 and 10 to establish control and thermal
stress effects, respectively. Chemical adrenalectomy was achieved by injecting metyrapone (100 mg/kg body weight) followed
by exogenous melatonin treatment (0.1 mg/kg body weight) from 11th to 17th day of experiment. Thermal stress significantly
(P ≤ 0.05) altered the physiological responses. Metyrapone and melatonin treatment significantly (P ≤ 0.05) reduced the thermal-stress-induced increase in plasma concentrations of cortisol and corticosterone while significantly
(P ≤ 0.05) increased the plasma melatonin on days 11 and 17. Furthermore, these treatments significantly (P < 0.05) increased the phagocytic activity of neutrophils as compared to both control and thermal exposure values from 11–17 days
of experiment. The data generated from this study help us to understand the functional relationship between pineal, adrenal,
and immune system, and how this relationship modifies the non-specific immune response for the well being of goats during
thermal stress. 相似文献
82.
Interactions between quercetin and Warfarin for albumin binding: A new eye on food/drug interference
The interaction between quercetin, a popular antioxidant flavonoid, and human serum albumin (HSA) is investigated and characterized by means of induced circular dichroism and saturation transfer difference NMR. These techiques demonstrate the reversible binding of quercetin to the carrier protein, which is responsible for its dissolution in aqueous medium. Competition experiments with two classical probes for HSA binding sites, namely Ibuprofen and Warfarin (a common anticoagulant coumarin), demonstrate that quercetin has a primary binding site located in the subdomain IIA, where coumarins are hosted. The affinity for this site is large and we found that quercetin may effectively displace warfarin from HSA. This may have relevant consequences in rationalizing the interferences of common dietary compounds and food supplements to anticoagulant treatments. Chirality, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
83.
This paper describes the development of a two-dimensional, spatially distributed model to simulate coupled hydrologic and phosphorus (P) biogeochemical processes in a 147-ha cell of a 1544-ha stormwater treatment wetland designed to help protect the greater Everglades, FL, USA. The model was used to assess the effects of a suite of feasible management alternatives on the long-term ability of the wetland to sustain total P (TP) removal. The spatial and temporal dynamics of TP retention were simulated under historical (1995–2000) conditions, and under assumptions of removal of short-circuiting channels and ditches, changes in external hydraulic and TP loading, and long-term (>20 years) impacts on soil and water column TP dynamics under current and reduced load conditions. Internal hydrology and transport processes were calibrated against measured tracer concentrations, and subsequently validated against outflow discharge and spatial chloride concentration data. Cycling of P was simulated as first-order uptake and release, with different uptake coefficients for open water/sparse submerged aquatic vegetation (SAV) areas (0.2 day?1) and dense SAV areas (0.4 day?1), and a much lower, uniform release coefficient (1.97 × 10?4 day?1). The calibration and validation of the P model showed good agreement with field measurements of water column TP concentrations measured at the wetland outlet (calibration RMSE = 10.5 μg L?1; validation RMSE = 15.6 μg L?1). Under simulated conditions of preferential channels eliminated, average annual TP treatment effectiveness increased by 25%. When inflow TP loads were assumed to be eliminated after 6 years of loading, the release of accumulated soil P sustained predicted annual average outlet concentrations above 6.7 μg L?1 for 18 years, decreasing at a rate of 0.16 μg L?1 yr?1. Sensitivity analyses indicate that the most critical model input factors include flow resistance parameters, initial soil TP content, and P cycling parameters compared to initial water level, initial TP concentration in water column, ET and transport parameters. 相似文献
84.
Kenjiro Asagoshi Yuan Liu Aya Masaoka Li Lan Rajendra Prasad Julie K. Horton Ashley R. Brown Xiao-hong Wang Hussam M. Bdour Robert W. Sobol John-Stephen Taylor Akira Yasui Samuel H. Wilson 《DNA Repair》2010,9(2):109-119
We examined a role for DNA polymerase β (Pol β) in mammalian long patch base excision repair (LP BER). Although a role for Pol β is well known in single-nucleotide BER, information on this enzyme in the context of LP BER has been limited. To examine the question of Pol β involvement in LP BER, we made use of nucleotide excision repair-deficient human XPA cells expressing UVDE (XPA-UVDE), which introduces a nick directly 5′ to the cyclobutane pyrimidine dimer or 6-4 photoproduct, leaving ends with 3′-OH and 5′-phosphorylated UV lesion. We observed recruitment of GFP-fused Pol β to focal sites of nuclear UV irradiation, consistent with a role of Pol β in repair of UV-induced photoproducts adjacent to a strand break. This was the first evidence of Pol β recruitment in LP BER in vivo. In cell extract, a 5′-blocked oligodeoxynucleotide substrate containing a nicked 5′-cyclobutane pyrimidine dimer was repaired by Pol β-dependent LP BER. We also demonstrated Pol β involvement in LP BER by making use of mouse cells that are double null for XPA and Pol β. These results were extended by experiments with oligodeoxynucleotide substrates and purified human Pol β. 相似文献
85.
Dev Chandran Kolli Bhaktavatsala Reddy Shahana Pallichera Vijayan Parthasarthy Sugumar Gudavalli Sudha Rani Ponsekaran Santha Kumar Lingala Rajendra Villuppanoor Alwar Srinivasan 《Indian journal of microbiology》2010,50(3):266-274
Peste des Petits Ruminants (PPR) is a highly contagious animal disease caused by the Peste des Petits Ruminants virus (PPRV) belonging to the genus morbillivirus and family Paramyxoviridae. The disease results in high morbidity and mortality
in goats, sheep and in some small wild ruminants. The presence of large number of small ruminants reared in endemic areas
makes PPR a notorious disease threatening the livelihood of poor farmers. Conventional vaccination using a live, attenuated
vaccine gives adequate protection but cannot be used in case of eradication of the disease due to difficulty in differentiation
of infected animals from the vaccinated ones. 相似文献
86.
Acetylcholine (ACh) is an important neurotransmitter whose non-neuronal biological roles are being widely accepted. ACh and components of its metabolism are present in plants. ACh and some inhibitors of acetylcholinesterase (AChE) share structural similarity (quaternary ammonium group) with some inhibitors of biosynthesis of a plant hormone, gibberellic acid (GA); e.g., 2-Isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride (AMO-1618) inhibits GA biosynthesis as well as AChE. The present study explores the possibility that ACh and antiAChE may inhibit GA biosynthesis. Seeds of barley var. Jyoti were germinated in the presence of ACh, its breakdown products - choline and acetate, and two antiAChE - neostigmine and physostigmine (all 10(-5) M). Alpha amylase activity in germinating seeds was measured as a reliable indicator of the level of GA biosynthesis. Alpha amylase activity in barley seeds was significantly reduced after 72 h of treatment with antiChE but not by ACh or its breakdown products. Since germinating barley seeds contain AChE, much of the ACh may have been broken down before its uptake. Quaternary ammonium antiChE neostigmine was more effective (50% inhibition at 10(-5) M) as compared to tertiary ammonium physostigmine (15% inhibition at 10(-5) M). ACh, choline, acetate, neostigmine and physostigmine (all 10(-5) M) did not affect formation of starch-iodine complex or activity of alpha-amylase per se. Our results indicate that quaternary ammonium inhibitors of AChE may inhibit GA biosynthesis. 相似文献
87.
King AJ Olivier NB Mohankumar PS Lee JS Padmanabhan V Fink GD 《American journal of physiology. Endocrinology and metabolism》2007,292(6):E1837-E1841
Polycystic ovary syndrome (PCOS), a leading cause of infertility, affects approximately 10% of women of reproductive age. The etiology and pathophysiology of PCOS are poorly understood. PCOS is multifaceted and includes reproductive abnormalities and components of the metabolic syndrome such as insulin resistance, obesity, dyslipidemia, and hypertension. Exposure to excess testosterone (T) during the prenatal period may predispose individuals to PCOS phenotype. The goal of this study was to determine whether hypertension and dyslipidemia occur in a well-characterized model of PCOS produced by prenatal treatment of sheep with T. Radiotelemetry was used to measure blood pressure over a 24-h period in conscious, undisturbed animals. To normalize circulating estradiol levels across treatment, control (n = 4) and prenatal T-treated (100 mg T propionate im twice weekly from days 30 to 90 of fetal life, n = 4) 2-yr-old females were ovariectomized, instrumented with a radiotelemetry transmitter, and clamped with early follicular phase levels of estrogen using an implant. Six days later, a 24-h recording period commenced. Prenatal T-treated sheep were hypertensive compared with control sheep, and heart rate tended to be higher. T-treated sheep had hyperglycemia, insulin resistance, hypernatremia, and hyperchloremia, and both total and LDL cholesterol tended to be higher. Plasma aldosterone and epinephrine were significantly lower in T-treated sheep, whereas norepinephrine was unchanged. This first-ever use of radiotelemetric blood pressure recordings in sheep demonstrates that mild hypertension, a risk factor reported in some women with PCOS, is also a feature of the sheep model of PCOS produced by prenatal T treatment. 相似文献
88.
Jha A Mukherjee C Prasad AK Parmar VS Clercq ED Balzarini J Stables JP Manavathu EK Shrivastav A Sharma RK Nienaber KH Zello GA Dimmock JR 《Bioorganic & medicinal chemistry》2007,15(17):5854-5865
A series of E,E,E-3,5-bis(arylidene)-1-(4-arylamino-4-oxo-2-butenoyl)-4-piperidones 4 (phenylidene) and 5 (4-nitrophenylidene) were prepared in order to explore the structural features of the N-acyl group which affects the cytotoxic potency. Evaluation toward human Molt 4/C8 and CEM T-lymphocytes revealed that many of the IC(50) figures were submicromolar and lower than melphalan. Marked inhibitory potencies toward murine leukemia L1210 cells were also noted. When evaluated against a panel of human tumor cell lines, three representative compounds in series 4 displayed selective toxicity to leukemia and colon cancer cell lines and were significantly more potent than the reference drug melphalan. Molecular modeling of representative compounds in both series 4 and the analogs, in which the configuration of the olefinic double bond was changed from E to Z (series 3), revealed that the torsion angles of the arylidene aryl rings and locations of the terminal arylaminocarbonyl groups may have contributed to the greater cytotoxic properties displayed in 3. Compounds 4c (3,4-dichlorophenylamino), d (4-methylphenylamino) and 5c (3,4-dichlorophenylamino), d (4-methylphenylamino) inhibited the activity of human N-myristoyltransferase by approximately 50% at concentrations of 50-100 microM. The compounds in series 4 and 5 were well tolerated in a short-term toxicity study in mice. 相似文献
89.
Dwivedi S Sharma A Patrick B Sharma R Awasthi YC 《Redox report : communications in free radical research》2007,12(1):4-10
Available evidence from a multitude of studies on the effects of 4-hydroxynonenal (HNE) on cellular processes seem to converge on some common themes: (i) concentration-dependent opposing effects of HNE on key signaling components (e.g. protein kinase C, adenylate cyclase) predict that certain constitutive levels of HNE may be needed for normal cell functions - lowering of this constitutive HNE level in cells promotes proliferative machinery while an increase in this level promotes apoptotic signaling; (ii) HNE is a common denominator in stress-induced apoptosis caused by H(2)O(2), superoxide, UV, heat or oxidant chemicals such as doxorubicin; and (iii) HNE can modulate ligand-independent signaling by membrane receptors such as EGFR or Fas (CD95) and may act as a sensor of external stimuli for eliciting stress-response. Against a backdrop of various reported effects of HNE, in vitro and in vivo, we have critically evaluated the above mentioned hypotheses suggesting a key role of HNE in signaling. 相似文献
90.
Saima Khanam Pilankatta Rajendra Navin Khanna Sathyamangalam Swaminathan 《BMC biotechnology》2007,7(1):10