首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   329篇
  免费   5篇
  334篇
  2024年   1篇
  2023年   8篇
  2022年   13篇
  2021年   24篇
  2020年   8篇
  2019年   13篇
  2018年   12篇
  2017年   19篇
  2016年   13篇
  2015年   19篇
  2014年   25篇
  2013年   29篇
  2012年   18篇
  2011年   20篇
  2010年   18篇
  2009年   8篇
  2008年   19篇
  2007年   10篇
  2006年   9篇
  2005年   14篇
  2004年   3篇
  2003年   1篇
  2002年   4篇
  2001年   3篇
  1999年   2篇
  1998年   3篇
  1997年   1篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1984年   1篇
  1981年   1篇
  1976年   1篇
排序方式: 共有334条查询结果,搜索用时 14 毫秒
81.
82.
The aim of the study was to determine the interaction between the natural geochemistry and the anthropogenic effects through trace element profiles in one of the environmentally significant areas of the Gaza Strip. Five boreholes were dug in the area of the Gaza wastewater treatment plant. The geology, mineralogy, and geochemistry of the soil profiles were studied, and the geochemistry of wastewater, sludge, soil, and groundwater was identified by several analytical techniques. The study introduced the environmental baselines and the infrastructure needed for further research for the first time: the natural infiltration potential, the artificial recharge, and the agricultural activities of water and wastewater. The results of the geochemical investigations confirmed that the upper 40 cm of soil was found to be the affected zone by wastewater and sludge. Among 26 elements analyzed, only a few metals (As, Cd, Cr, Hg, Zn, and to a lesser extent Pb) showed relevance from the human health point of view. The metal accumulations in the soils were characterized by a large spatial variability, with some “hot spots” of Cu and Zn reaching topsoil concentrations of up to 240 and 2005 mg/kg, respectively. In spite of that, the results of the groundwater revealed that none of them was detected at concentrations that exceeded the WHO (World Health Organization) standards. Moreover, it was shown that both anthropogenic activities as well as seawater intrusion caused the high levels of nitrate and salinity.  相似文献   
83.
    
Infection by LP-BM5 murine leukemia virus (MuLV) produces an AIDS-like condition in mice. The viral infection suppressed the percentage of peripheral blood cells showing surface markers for macrophages, activated macrophages, T lymphocytes and activated lymphoid cells. High dietary vitamin A (retinyl palmitate) caused increased numbers of activated macrophages. It also increased the percentage of cells with markers for Ia+ cells and macrophages in the retrovirally infected mice compared to infected controls. In uninfected mice retinyl palmitate stimulated the percentage of cells with activated lymphocytes bearing IL-2R, and T cytotoxic cells. These were associated with a retarded death rate during infection with LP-BM5 murine leukemia in C57BL/6 mice. By 25 weeks of infection and 20 weeks of retinyl palmitate supplementation 71.3% survived, while 45.0% virally infected controls survived. The mice also had elevated numbers of B cells measured in the blood after 4 and 8 weeks of dietary treatment. Vitamin A stimulation may play a role in the slower death rate for retrovirally infected mice.  相似文献   
84.
The effects of high-peak-power, pulsed microwaves on a time perception and discrimination task were studied in rats. Exposures were performed with the TEMPO exposure system, which produces an 80 nanosecond pulse with peak-power levels in excess of 700 megawatts. The ability to expose animals to such fields within a controlled environment is unique. As determined by calorimetry, a maximal, whole-body-averaged, specificabsorption rate of 0.072 W/kg was produced. Thus exposures were well below a recommended SAR limit of 0.4 W/kg. Power levels of transmitted microwaves were varied over a 50 dB range to obtain ascending and descending dose-response functions for each of the behavioral measures. Measures of time perception, response bias, and total trials did not change with power level. Dose-response effects were observed for discriminability (ability to distinguish between durations), session time, and trial completions (null responses, failures to respond on a trial). Covarying sound and X-ray exposures produced by TEMPO did not reliably correlate with the observed microwave effects. The observation of repeatable dose-response effects on discriminability and null responses indicates that the microwave exposures were affecting cognitive function in the rats, particularly the decision-making process. © 1993 wiley-Liss, Inc.  相似文献   
85.
A simple approach to synthesize phospholipids to modulate drug release and track lipid-based particulate drug-carriers is described. We synthesized two ether lipids, 1 1-O-hexadecyl-2-pentadenoyl-sn-glycerol-3-phosphocholine (C(31)PC) and 2 1-O-hexadecyl-2-pentadenoyl-sn-glycerol-3-phosphomethanol (C(31)PM), and examined their ability to alter enzymatically triggered release of 6-carboxyfluorescein from liposomes incubated in TRIS buffer or fetal bovine serum solutions. Further, we demonstrated that odd-chain lipids, for example, C(31)PC, could be identified in rat plasma without interference of endogenous lipids. This approach can be adapted to synthesize a variety of lipids for use in developing and optimizing multifunctional drug-carriers.  相似文献   
86.
BACKGROUND: Adenoid cystic carcinoma is a very rare primary pulmonary neoplasm. Cytologic findings of pulmonary washing and brushing in 2 cases of primary bronchial adenoid cystic carcinoma with special histologic features are described, with an emphasis on some points that have not been reported previously, together with the diagnostic pitfalls. CASES: Two cases of primary adenoid cystic carcinoma of the lung were diagnosed on exfoliative cytology. The patients' ages were 55 and 65 years old. Cytologic findings included large and small clusters of small cells in both 2 and 3 dimensions with occasional cystlike spaces containing mucoid material. The cells were arranged in spherical, cylindrical, basaloid and rosettelike arrangements. There were also abundant small and large mucoid globules, cylinders of homogeneous, acellular, mucous material and cannon balls. Cytoplasmic and intranuclear round inclusions were noted in case 1. Rare findings of nuclear molding were noted. In case 2, chondromyxoid material and a bimorphic population of tumor cells caused diagnostic confusion with other salivary gland-type tumors of the lung. CONCLUSION: These cases showed characteristic cytologic findings of adenoid cystic carcinoma together with rare findings of intracellular and extracellular inclusionlike bodies, myxochondroid material, bimorphic populations and nuclear molding, which can cause diagnostic confusion with other lung tumors.  相似文献   
87.
BACKGROUND: Desmoplastic medulloblastoma is a rare subtype of medulloblastoma with astroglial differentiation. The cytomorphologic features in intraoperative imprint smears from 2 cases of desmoplastic medulloblastoma are described. CASE REPORTS: A 22-year-old man and 27-year-old woman with a cerebellar tumor underwent craniotomy and tumor resection. The imprint cytologic smears contained cellular zones and nodular hypocellular areas containing astroglial and oligodendrogliallike elements. The cytology was misinterpreted as glial tumors, while the final histologic diagnosis in both cases were desmoplastic medulloblastoma. CONCLUSION: Desmoplastic medulloblastoma shows distinctive cytology in intraoperative smears. However, the occurrence of this rare type in adults and the presence of astroglial elements in imprint smears may cause a cytologic misinterpretation as gliomas.  相似文献   
88.
89.
    
This study examined the impact of different cooking methods on fatty acid (FAs) composition of shrimp meat and the ability of these foods to protect against high cholesterol (HC) diet-induced non-alcoholic fatty liver disease (NAFLD) in rats. Shrimp were cooked for 10 min boiled, grilled, or fried in sunflower oil. Rats (n = 6/group) were fed a normal diet (ND)or high-cholesterol diet (HC) each containing boiled, grilled or fried shrimp powder (15% w/w) (NDBS, NDFS, NDGS for ND or HCBS, HCFS, HCDGS for HC diet). Frying alone significantly reduced total levels of saturated FAs (SFA) and increased total mono- and polyunsaturated FAs (MSFA, and PUFAs, respectively) in shrimp meat. It also increased levels of n-6 PUFAs and linoleic acid (LA) and decreased levels of n-3 PUFAs including eicosapentaenoic FAs (EPA) and docosahexaenoic fatty acid (DHA). When fed to HC rats, only diets containing the grilled and boiled shrimp powders significantly prevented the weight loss, lowered fasting and glucose levels, improved glucose and insulin tolerance, and prevented the increase in serum liver markers, ALT and AST. They also reduced hepatic fat accumulation, reduced serum levels and hepatic levels of cholesterol and triglycerides (TGs), reduced hepatic levels of MDA, tumor necrosis factor-alpha (TNF-α), and IL-6, and increased those of glutathione (GSH) and superoxide dismutase (SOD). No alterations in all these parameters were observed in HC-fed rats which fed fried shrimp. In conclusion, boiling and grilling but not frying are the best method to cook shrimp to preserve their fatty acid content and its nutritional value in ameliorating NAFLD.  相似文献   
90.
    
Jatropha mollissima is one of the ancient plants that known in Africa, Asia and Latin America for its high medicinal value. Previously we showed that the ethanolic leaves extract of J. mollissima was able to reverse the aminoglycoside antibiotics induced nephrotoxicity in only two weeks of administration. Here, we evaluated the phytochemicals, antioxidant and in vivo cytotoxicity of the ethanolic leaves extract in addition to the ability of reversing Cisplatin-induced nephrotoxicity in wistar albino rats. The results of phytochemical analysis showed the presence of flavonoids, phenols, tannins and saponins, with significantly high antioxidant activity. The treated rats did not show any cytotoxic signs; no anatomical, physiological and/or histopathological changes compared with the control group. Kidney, spleen and liver tissues appeared normal after two weeks administration of the maximum dose, with a possible alteration in distal tubules, proximal tubules and glomerulus of the kidney tissues. The results of nephrotoxicity and kidney function suggest promising potential for J. mollissima in kidney damage treatment.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号