全文获取类型
收费全文 | 4911篇 |
免费 | 462篇 |
国内免费 | 311篇 |
专业分类
5684篇 |
出版年
2024年 | 21篇 |
2023年 | 150篇 |
2022年 | 198篇 |
2021年 | 239篇 |
2020年 | 224篇 |
2019年 | 262篇 |
2018年 | 237篇 |
2017年 | 200篇 |
2016年 | 227篇 |
2015年 | 213篇 |
2014年 | 272篇 |
2013年 | 366篇 |
2012年 | 188篇 |
2011年 | 266篇 |
2010年 | 159篇 |
2009年 | 225篇 |
2008年 | 192篇 |
2007年 | 234篇 |
2006年 | 179篇 |
2005年 | 150篇 |
2004年 | 158篇 |
2003年 | 130篇 |
2002年 | 127篇 |
2001年 | 95篇 |
2000年 | 87篇 |
1999年 | 79篇 |
1998年 | 86篇 |
1997年 | 90篇 |
1996年 | 70篇 |
1995年 | 103篇 |
1994年 | 73篇 |
1993年 | 45篇 |
1992年 | 31篇 |
1991年 | 30篇 |
1990年 | 24篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 29篇 |
1983年 | 23篇 |
1982年 | 27篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1973年 | 7篇 |
排序方式: 共有5684条查询结果,搜索用时 0 毫秒
991.
Alessandra Cesano Sophie Visonneau Livia Cioé Steven C. Clark Daniela Santoli 《Cancer immunology, immunotherapy : CII》1995,40(3):139-151
The TALL-104 cell line, originally derived from a patient with T cell leukemia, can be maintained indefinitely in culture in the presence of interleukin-2 (IL-2) and is endowed with a highly potent major-histocompatibilitycomplex (MHC)-non-restricted tumoricidal activity both in vitro and in animal models. The present study analyzes in detail the short- and long-term effects of irradiation and cyclosporin A (CsA) treatment on the growth and tumoricidal function of this T cell clone as compared to polyclonal lymphokine-activated killer (LAK) cell preparations from healthy donors. DNA and RNA syntheses by both TALL-104 and LAK cells were irreversibly arrested a few hours after irradiation with 40 Gy. However, 4-h51Cr-release assays, performed on different days (day 1 to day 7) after irradiation, showed that the cytotoxic efficiency of TALL-104 cells against hematopoietic and solid tumor targets was only modestly reduced, whereas that of LAK cells was severely inhibited. Moreover, the cytotoxic responses to recombinant human IL-2 and IL-12, measured 18 h after irradiation and cytokine addition, were normal in the case of TALL-104 cells but were abolished in the case of LAK cells. Co-culture of IL-2-or IL-12-preactivated TALL-104 cells with a tumor target for 5 days in the absence of cytokines resulted in a lower efficiency of lysis, as compared to the non-irradiated effectors, especially if the initial stimulus was IL-12. These findings suggest the requirement of multiple cytokine stimulation for optimal expression of tumoricidal activity by lethally irradiated TALL-104 cells. CsA, while abrogating TALL-104 cell proliferation at the low dose of 0.5 g/ml, inhibited their cytotoxic function marginally only at high doses (100 g/ml). By contrast, CsA reduced dose-dependently the cytotoxicity of LAK cells starting at very low doses (0.5 g/ml). CsA did not impair the ability of TALL-104 and LAK cells to produce interferon (IFN), tumor necrosis factor (TNF) , and granulocyte/macrophage-colony-stimulatory factor (GM-CSF) in response to IL-2, IL-12, or tumor targets. Irradiation reduced drastically IFN production by LAK, but not TALL-104 cells; release of TNF and GM-CSF by either type of effector was inhibited by 10%–50%, depending on the stimulus. The high resistance of the TALL-104 cells' tumoricidal function to irradiation and immunosuppressive drugs renders this immortal T cell clone a potentially safe and effective reagent for new adoptive-transfer approaches to cancer in MHC-incompatible recipients. 相似文献
992.
在 0 .5 0 μmol/ml氨基酸标准溶液中 ,分别加入衍生剂 1 0 .0 ,1 2 .5 ,1 5 .0 ,1 7.5 μl进行衍生 ,并与标准方法的2 0 .0 μl进行对照 ,测定各种氨基酸的峰面积 ,方差分析表明 ,衍生剂加入量为 1 5 .0 μl和 1 7.5 μl时 ,峰面积与对照无显著差异 ,加入 1 0 .0 μl和 1 2 .5 μl时与对照有极显著差异 ,因此 ,在实际样品分析中 ,只加入 1 5 μl衍生剂 ,已完全能够满足常规分析的需要 ,而可以节省 1 /4的衍生剂用量 相似文献
993.
长江江豚感染铜绿假单胞菌肺炎的诊治 总被引:1,自引:0,他引:1
本文记录了一例患急性铜绿假单胞菌肺炎的长江江豚诊断、治疗和预后观察过程。病原学鉴定采用鲜血琼脂平板对该江豚鼻腔拭子,在37℃下进行细菌需氧、厌氧培养和分离,并对所分离的细菌种类进行细菌学鉴定,结合血常规和血生化的检测结果,判定病原为铜绿假单胞菌(Pseudomonas aeruginosa,PA)。依据病原菌的药敏试验结果对患病江豚进行治疗,预后良好。通过对整个过程的资料分析以及预后观察,得到如下提示:1)应做好饲养环境的消毒措施,防止江豚出现获得性PA感染;2)对江豚日常呼吸道和粪便中PA的检测,有利于疾病的早期预防和控制;3)江豚呼吸系统疾病的治愈依赖于准确的病原鉴定和及时的治疗,药敏试验对于PA感染的治疗非常必要;4)行为学的改变在江豚呼吸道疾病发病初期以及预后有重要的指示作用。 相似文献
994.
Phage and colicin-resistant mutants were derived from Escherichia coli K-12P678. Two classes of phage T6 and colicin K-resistant mutants (genotype tsx) were isolated. Tsx-2 mutants, which demonstrated mucoid growth and increased sensitivities to many antibiotics, became sensitive to colicin K when pretreated with ethylenediaminetetraacetate (EDTA), whereas Tsx-1 mutants did not. Reassociation of EDTA-released material partially restored resistance to colicin K for Tsx-2 mutants. When EDTA-released material from strain P678 was associated with either class of K-resistant mutant, an increase in colicin K sensitivity resulted. Observations suggest that colicin K can act on its target site once it penetrates the cell surface. In addition, results suggest that functional colicin K receptors can be transferred from sensitive to resistant strains, thus conferring colicin sensitivity.Non-standard Abbreviations SDS
sodium dodecyl sulfate 相似文献
995.
An alternative procedure to obtain the parameters of Monod's growth model in batch culture is presented. It is based on the integral kinetic analysis methodology, employs a one-dimensional Golden Section search optimization method and is implemented on a spread-sheet programme. The procedure is discussed in detail and is illustrated by analysis of batch substrate consumption data by an aerobic bacterial consortium. 相似文献
996.
Application of Image Analysis Techniques in Activated Sludge Wastewater Treatment Processes 总被引:1,自引:0,他引:1
Liwarska-Bizukojc E 《Biotechnology letters》2005,27(19):1427-1433
Image analytical techniques have been extensively developed to evaluate complex microbial aggregates such as sludge flocs
and biofilms. This review covers the latest contributions concerning the application of image analysis to the activated sludge
systems with respect to the most frequently used morphological parameters and relations between them and traditional wastewater
treatment parameters. Recent developments have indicated that image analysis can be successfully used for the quantification
of flocs and filamentous bacteria in the operating wastewater treatment plants, which enables prediction of bulking events
and pinpoint flocs formation. 相似文献
997.
Ashara Pengnoo Ruedeekorn Wiwattanapattapee Amornrat Chumthong Mana Kanjanamaneesathian 《World journal of microbiology & biotechnology》2006,22(1):9-14
Summay Soil samples were taken from 48 fields in the southern part of Thailand in which either bambara groundnut (Vigna subterranea) or groundnut (Arachis hypogeae) had been planted. Bacillus spp. were isolated using soil dilution plates and heat treatment to screen for endospore-producing bacteria. Among 342 Bacillus spp. isolates tested, 168 isolates were not antagonistic to Bradyrhizobium sp. strain NC-92 using dual culture technique. Further testing found 16 isolates of Bacillus spp. had the ability to inhibit mycelial growth of Rhizoctonia solani, a causal agent of leaf blight of bambara groundnut. Among these isolates, Bacillus spp. isolate TRV 9-5-2 had the greatest activity in anti-microbial tests against R. solani. This isolate was later identified as B. firmus. A powder formulation of B. firmus was developed by mixing bacterial endospores, talcum, sodium carboxymethylcellulose (SCMC) and polyvinylpyrolidone (PVP).
The formulations contained bacterial levels ranging from 108 to 1010 c.f.u./g and the viability of bacteria in all formulations remained high after 1 year storage at room temperature (26–32 °C).
All formulations showed satisfactory effectiveness in vitro in suppressing mycelial growth of R. solani using dual culture technique. The application of formulations as seed treatment showed that these formulations did not cause
abnormality of seedling shape and had no effect on the germination of bambara groundnut seeds. 相似文献
998.
目的探讨老年肺癌非手术治疗患者医院内获得性肺炎的临床特点及对策。方法对2006年1月至2008年12月住院的275例非手术治疗老年肺癌的医院内获得性肺炎(Hospital-acquired pneumonia,HAP)情况进行回顾性分析。结果本组病例发生院内获得性肺炎165例。以中央型肺癌、鳞癌易发院内获得性肺炎;由革兰阴性菌导致的HAP明显高于革兰阳性菌与真菌;放疗加化疗HAP感染率高于单纯放疗或化疗;随着白细胞下降,感染率明显增高,特别是粒细胞〈1.0×10^9/L者感染率最高。结论根据老年肺癌非手术治疗院内获得性肺炎的临床特点把HAP的预防作为根本措施,一旦出现感染应及时治疗。 相似文献
999.
Fikret Kargi 《Biotechnology letters》2002,24(19):1569-1572
Biological treatment of saline wastewater by conventional activated sludge culture usually results in low removal of chemical oxygen demand (COD) because of plasmolysis of the organisms at high salt concentrations. Since salt removal operations by physicochemical processes before biological treatment are costly, a salt-tolerant organism (Halobacter halobium) was used for effective biological treatment of saline wastewater in this study. Halobacter halobium was used in activated sludge culture for COD removal from saline wastewater (1–5% salt) by fed-batch operation of an aeration tank. Inclusion of Halobacter halobium into activated sludge culture improved the rate and extent of COD removals especially with salt above 2% (w/v). 相似文献
1000.
Zoya Tahergorabi Majid Khazaei Mitra Moodi Elham Chamani 《Cell biochemistry and function》2016,34(8):533-545
Nowadays, obesity is considered as a serious and growing global health problem. It is documented that the overweight and obesity are major risk factors for a series of noncommunicable diseases, and in recent years, the obesity‐cancer link has received much attention. Numerous epidemiological studies have shown that obesity is associated with increased risk of several cancer types, including colon, breast, endometrium, liver, kidney, esophagus, gastric, pancreatic, gallbladder, and leukemia, and can also lead to poorer treatment. We review here the epidemiological and experimental evidences for the association between obesity and cancer. Specifically, we discuss potential mechanisms focusing how dysfunctional angiogenesis, chronic inflammation, interaction of proinflammatory cytokines, endocrine hormones, and adipokines including leptin, adiponectin insulin, growth factors, estrogen, and progesterone and strikingly, cell metabolism alteration in obesity participate in tumor development and progression, resistance to chemotherapy, and targeted therapies such as antiangiogenic and immune therapies. 相似文献