全文获取类型
收费全文 | 868942篇 |
免费 | 90181篇 |
国内免费 | 600篇 |
专业分类
959723篇 |
出版年
2018年 | 8404篇 |
2017年 | 8078篇 |
2016年 | 12611篇 |
2015年 | 19072篇 |
2014年 | 21081篇 |
2013年 | 27886篇 |
2012年 | 30215篇 |
2011年 | 28421篇 |
2010年 | 19832篇 |
2009年 | 18209篇 |
2008年 | 24141篇 |
2007年 | 24666篇 |
2006年 | 23326篇 |
2005年 | 27771篇 |
2004年 | 26529篇 |
2003年 | 24102篇 |
2002年 | 21228篇 |
2001年 | 38899篇 |
2000年 | 38723篇 |
1999年 | 31320篇 |
1998年 | 10914篇 |
1997年 | 11294篇 |
1996年 | 10579篇 |
1995年 | 9911篇 |
1994年 | 9652篇 |
1993年 | 9407篇 |
1992年 | 25803篇 |
1991年 | 25161篇 |
1990年 | 24662篇 |
1989年 | 23992篇 |
1988年 | 22307篇 |
1987年 | 20827篇 |
1986年 | 19306篇 |
1985年 | 19187篇 |
1984年 | 15752篇 |
1983年 | 13061篇 |
1982年 | 9797篇 |
1981年 | 8749篇 |
1980年 | 8174篇 |
1979年 | 14185篇 |
1978年 | 10983篇 |
1977年 | 9861篇 |
1976年 | 8995篇 |
1975年 | 10089篇 |
1974年 | 10848篇 |
1973年 | 10758篇 |
1972年 | 9605篇 |
1971年 | 8818篇 |
1970年 | 7566篇 |
1969年 | 7343篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
991.
K M Raines 《The Journal of parasitology》1989,75(4):601-605
Prairie voles, Microtus ochrogaster, were infected with Eimeria ochrogasteri and exposed to 2 environmental temperatures, 5 and 22 C. Dry weights of the small and large intestines increased by 33% and 19%, respectively, in infected animals. Infected animals also exhibited a 14% decrease in cecal length compared to uninfected animals. The interaction between temperature and infection affected the length of the small intestine. Infected animals maintained at 5 C had longer small intestines than both infected animals housed at 22 C, and uninfected animals at 22 or 5 C. Furthermore, the dry weight of the small intestine was affected by a 3-way interaction (infection, temperature, and sex). Temperature affected stomach and liver dry weights, as well as lengths of the small intestine and cecum. Stomach and liver dry weights, as well as small intestine lengths, were greater in those animals held at 5 C, whereas cecum lengths decreased. Prepatency, patency, and total oocyst production were not affected by temperature; however, infected animals held at 5 C exhibited diarrhea during the patent period. 相似文献
992.
The cytotoxic and radiosensitizing effects of hyperthermia was shown on Ehrlich ascites tumor cells heated in vitro. The effect of hyperthermia resulted in the formation of local lesions in membranes of dying cells. 相似文献
993.
H Zitzer H H H?nck D B?chner D Richter H J Kreienkamp 《The Journal of biological chemistry》1999,274(46):32997-33001
By using the yeast two-hybrid system we identified a novel protein from the human brain interacting with the C terminus of somatostatin receptor subtype 2. This protein termed somatostatin receptor interacting protein is characterized by a novel domain structure, consisting of six N-terminal ankyrin repeats followed by SH3 and PDZ domains, several proline-rich regions, and a C-terminal sterile alpha motif. It consists of 2185 amino acid residues encoded by a 9-kilobase pair mRNA; several splice variants have been detected in human and rat cDNA libraries. Sequence comparison suggests that the novel multidomain protein, together with cortactin-binding protein, forms a family of cytoskeletal anchoring proteins. Fractionation of rat brain membranes indicated that somatostatin receptor interacting protein is enriched in the postsynaptic density fraction. The interaction of somatostatin receptor subtype 2 with its interacting protein was verified by overlay assays and coimmunoprecipitation experiments from transfected human embryonic kidney cells. Somatostatin receptor subtype 2 and the interacting protein display a striking overlap of their expression patterns in the rat brain. Interestingly, in the hippocampus the mRNA for somatostatin receptor interacting protein was not confined to the cell bodies but was also observed in the molecular layer, suggesting a dendritic localization of this mRNA. 相似文献
994.
995.
996.
V T Kondakov A B Okulov M A Filippkin R Z Tandilava I U Artamonov O A Voronenko A N Sazonov 《Vestnik rentgenologii i radiologii》1991,(4):31-35
The paper is concerned with analysis of the results of intraoperative phlebotesticulography, performed in 50 patients with varicocele of degree I-II during Ivanissevich's operation. The effect of surgical intervention was shown to depend upon the quality of ligation of the testicular vein, some parts of which are anastomosed between themselves. The localization of this anastomosis is revealed by means of intraoperative phlebotesticulography, which permits increasing the results of surgical treatment and predicting a course of a postoperative period. 相似文献
997.
998.
Toxicity of Dopamine to Striatal Neurons In Vitro and Potentiation of Cell Death by a Mitochondrial Inhibitor 总被引:8,自引:2,他引:6
B. A. McLaughlin †D. Nelson †‡M. Ereciska † M.-F. Chesselet 《Journal of neurochemistry》1998,70(6):2406-2415
Abstract: Intrastriatal injections of the mitochondrial toxins malonate and 3-nitropropionic acid produce selective cell death similar to that seen in transient ischemia and Huntington's disease. The extent of cell death can be attenuated by pharmacological or surgical blockade of cortical glutamatergic input. It is not known, however, if dopamine contributes to toxicity caused by inhibition of mitochondrial function. Exposure of primary striatal cultures to dopamine resulted in dose-dependent death of neurons. Addition of medium supplement containing free radical scavengers and antioxidants decreased neuronal loss. At high concentrations of the amine, cell death was predominantly apoptotic. Methyl malonate was used to inhibit activity of the mitochondrial respiratory chain. Neither methyl malonate (50 µ M ) nor dopamine (2.5 µ M ) caused significant toxicity when added individually to cultures, whereas simultaneous addition of both compounds killed 60% of neurons. Addition of antioxidants and free radical scavengers to the incubation medium prevented this cell death. Dopamine (up to 250 µ M ) did not alter the ATP/ADP ratio after a 6-h incubation. Methyl malonate, at 500 µ M , reduced the ATP/ADP ratio by ∼30% after 6 h; this decrease was not augmented by coincubation with 25 µ M dopamine. Our results suggest that dopamine causes primarily apoptotic death of striatal neurons in culture without damaging cells by an early adverse action on oxidative phosphorylation. However, when combined with minimal inhibition of mitochondrial function, dopamine neurotoxicity is markedly enhanced. 相似文献
999.
The results of recent randomized trials to test the influence of antioxidants on coronary-event rates and prognosis in patients
with coronary-artery disease were disappointing. In none of these studies did the use of vitamin E improve prognosis. In contrast,
treatment of coronary-artery disease with angiotensin-converting-enzyme (ACE) inhibitors reduced coronary-event rates and
improved prognosis. ACE inhibition prevents the formation of angiotensin II, which has been shown to be a potent stimulus
of superoxide-producing enzymes in atherosclerosis. The findings suggest that inhibition of superoxide production at enzymatic
levels, rather than symptomatic superoxide scavenging, may be the better choice of treatment. 相似文献
1000.