全文获取类型
收费全文 | 1064513篇 |
免费 | 112623篇 |
国内免费 | 391篇 |
出版年
2018年 | 10176篇 |
2017年 | 9778篇 |
2016年 | 13716篇 |
2015年 | 17824篇 |
2014年 | 21099篇 |
2013年 | 30795篇 |
2012年 | 34332篇 |
2011年 | 35174篇 |
2010年 | 23937篇 |
2009年 | 22229篇 |
2008年 | 31466篇 |
2007年 | 32537篇 |
2006年 | 30657篇 |
2005年 | 29298篇 |
2004年 | 29116篇 |
2003年 | 27945篇 |
2002年 | 27327篇 |
2001年 | 45351篇 |
2000年 | 44985篇 |
1999年 | 36555篇 |
1998年 | 13642篇 |
1997年 | 13458篇 |
1996年 | 12819篇 |
1995年 | 12239篇 |
1994年 | 12031篇 |
1993年 | 12048篇 |
1992年 | 30287篇 |
1991年 | 29550篇 |
1990年 | 28935篇 |
1989年 | 28439篇 |
1988年 | 26150篇 |
1987年 | 25070篇 |
1986年 | 23399篇 |
1985年 | 23436篇 |
1984年 | 19308篇 |
1983年 | 16914篇 |
1982年 | 12877篇 |
1981年 | 11623篇 |
1980年 | 11015篇 |
1979年 | 18347篇 |
1978年 | 14437篇 |
1977年 | 13020篇 |
1976年 | 12390篇 |
1975年 | 13737篇 |
1974年 | 14631篇 |
1973年 | 14452篇 |
1972年 | 13156篇 |
1971年 | 11841篇 |
1970年 | 10385篇 |
1969年 | 10039篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
The effect of a 30-day treatment with Madiol was studied on the activity of some enzymes, nucleic acids, protein and glycogen content of the liver of adult female rats and youngs born from mothers treated during pregnancy. Madiol caused a significant increase in SDH and Atp-ase activity, and decreased glycogen and acid phosphatase. 相似文献
962.
Inflammatory responses mediated by activated microglia play a pivotal role in the pathogenesis of human immunodeficiency virus type 1 (HIV-1)-associated neurocognitive disorders. Studies on identification of specific targets to control microglia activation and resultant neurotoxic activity are imperative. Increasing evidence indicate that voltage-gated K+ (Kv) channels are involved in the regulation of microglia functionality. In this study, we investigated Kv1.3 channels in the regulation of neurotoxic activity mediated by HIV-1 glycoprotein 120 (gp120)-stimulated rat microglia. Our results showed treatment of microglia with gp120 increased the expression levels of Kv1.3 mRNA and protein. In parallel, whole-cell patch-clamp studies revealed that gp120 enhanced microglia Kv1.3 current, which was blocked by margatoxin, a Kv1.3 blocker. The association of gp120 enhancement of Kv1.3 current with microglia neurotoxicity was demonstrated by experimental results that blocking microglia Kv1.3 attenuated gp120-associated microglia production of neurotoxins and neurotoxicity. Knockdown of Kv1.3 gene by transfection of microglia with Kv1.3-siRNA abrogated gp120-associated microglia neurotoxic activity. Further investigation unraveled an involvement of p38 MAPK in gp120 enhancement of microglia Kv1.3 expression and resultant neurotoxic activity. These results suggest not only a role Kv1.3 may have in gp120-associated microglia neurotoxic activity, but also a potential target for the development of therapeutic strategies. 相似文献
963.
Forty strains of ureolytic bacteria were isolated from the caecal content and soft faeces of seven rabbits by the anaerobic roll tube method and were characterized. The isolates were identified with Clostridium coccoides, Cl. innocuum, Peptostreptococcus productus, P. micros, Peptococcus magnus, Fusobacterium russii and Fusobacterium sp. Urease activity of representative strains of the various species was also determined. The study indicated that strongly-ureolytic anaerobic bacteria are present in the caecum of the rabbit. 相似文献
964.
Many commercial preparations of [32P]orthophosphate contain radioactive impurities that interfere with binding and transport studies in biological systems. One type of impurity is micro-particulate whereas another may be pyrophosphate. Methods of removing these impurities from radiolabeled orthophosphate solutions are described. 相似文献
965.
L L Kiseleva G N Novodarova M E Vol'pin A D Vinogradov 《Biokhimii?a (Moscow, Russia)》1982,47(11):1877-1882
The effects of the decamethyloctadehydrocorrine-cobalt complex (Co-C) on respiration and the ATP-synthetase activity of rat liver mitochondria were investigated. The Co-C complex was found to be an effective shunt of the respiratory chain. It accepts electrons from ubiquinone and donates them directly to O2. The Co-C complex inhibits the ATPase and ATP-synthetase activities of mitochondria. 相似文献
966.
967.
A new micronucleus test using peripheral blood erythrocytes of the newt Pleurodeles waltl to detect mutagens in fresh-water pollution 总被引:4,自引:0,他引:4
A model micronucleus test system using peripheral blood erythrocytes from larvae of Pleurodeles waltl is described. The most suitable larval stage for testing chemical treatments was determined. Larvae were reared in water containing one of the 4 compounds: benzo[a]pyrene (BaP), ethyl methanesulphonate (EMS), diethyl sulphate (DES) and N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). Response curves as a function of treatment duration over a period of 16 days were plotted for 3 different concentrations of the 4 compounds in order to optimize conditions for a low dose micronucleus test. This model can be used as a monitoring system for the detection of fresh water pollution and can also be employed for clastogen screening of chemical compounds. The test is sensitive, reliable and easy to use. 相似文献
968.
Large deformation mechanics of the enucleated eyeball 总被引:1,自引:0,他引:1
L A Taber 《Journal of biomechanical engineering》1984,106(3):229-234
Large deformation of enucleated pig eyeballs under rigid cylindrical indenters was studied analytically and experimentally. The analytic model for the eyeball consists of a fluid-filled spherical membrane composed of an incompressible, elastic material with an exponential strain energy function. The Rayleigh-Ritz technique provided an approximate solution via a potential energy formulation. Comparison with results from tests on eyeballs and a water-filled rubber (Mooney-Rivlin) shell shows good agreement at large deflection, where membrane action dominates. Due to the highly nonlinear stress-strain relations for the sclera, the load remains relatively small until the indenter displacement approaches 40-60 percent of the eyeball radius, and then the load increases rapidly. Depending on the indenter size, either a perforation or a rupture type of failure occurs. 相似文献
969.
970.
L Chrobák D Radochová K Smetana F Mat?ja M Kout J Polák P Dít? J Pribrosky I Dvorácková 《Folia haematologica (Leipzig, Germany : 1928)》1980,107(4):628-640
These siblings of a Czech family aged 21, 19 and 6 years, respectively, with congenital dyserythropoietic anemia, type II, (HEMPAS) are reported. In two elder siblings ferrokinetic studies revealed a rapid plasma 59Fe clearance, markedly decreased erythrocyte incorporation and shortened 51Cr red-cell survival. Direct anti-globulin test was found positive in one of them. Further investigations revealed low values of blood plasma cholesterol, total lipids, beta-lipoproteins, beta-carotine and vitamin E and A as well as low values of the prothrombin complex. Liver biopsy demonstrated siderosis and disseminated intravascular coagulation in the liver in both patients. The possible reasons for these humoral aberrations are discussed. 相似文献