全文获取类型
收费全文 | 10643篇 |
免费 | 598篇 |
国内免费 | 538篇 |
专业分类
耳鼻咽喉 | 86篇 |
儿科学 | 182篇 |
妇产科学 | 121篇 |
基础医学 | 1739篇 |
口腔科学 | 156篇 |
临床医学 | 626篇 |
内科学 | 1696篇 |
皮肤病学 | 101篇 |
神经病学 | 1133篇 |
特种医学 | 201篇 |
外科学 | 689篇 |
综合类 | 1566篇 |
现状与发展 | 2篇 |
预防医学 | 429篇 |
眼科学 | 114篇 |
药学 | 1737篇 |
中国医学 | 629篇 |
肿瘤学 | 572篇 |
出版年
2023年 | 56篇 |
2022年 | 129篇 |
2021年 | 146篇 |
2020年 | 152篇 |
2019年 | 149篇 |
2018年 | 167篇 |
2017年 | 173篇 |
2016年 | 211篇 |
2015年 | 252篇 |
2014年 | 489篇 |
2013年 | 635篇 |
2012年 | 581篇 |
2011年 | 728篇 |
2010年 | 588篇 |
2009年 | 623篇 |
2008年 | 704篇 |
2007年 | 755篇 |
2006年 | 696篇 |
2005年 | 625篇 |
2004年 | 685篇 |
2003年 | 609篇 |
2002年 | 507篇 |
2001年 | 408篇 |
2000年 | 322篇 |
1999年 | 252篇 |
1998年 | 222篇 |
1997年 | 194篇 |
1996年 | 143篇 |
1995年 | 109篇 |
1994年 | 74篇 |
1993年 | 64篇 |
1992年 | 34篇 |
1991年 | 29篇 |
1990年 | 20篇 |
1989年 | 14篇 |
1988年 | 23篇 |
1987年 | 21篇 |
1986年 | 11篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1972年 | 6篇 |
1968年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
目的探讨谷氨酸是否能够影响腺苷A2A受体对一氧化氮合酶(NOS)活力的调节。方法用1000ng/ml脂多糖(LPS)刺激小胶质细胞,分别加入100nmol/L A2A受体激动剂CGS21680以及不同浓度的谷氨酸(0,1,0,25,0,5mmol/L)干预,观察NOS活力变化。结果LPS诱导NOS活力增高,激活A2A受体可以产生抑制作用;0,25及0.5mmoL/L谷氨酸和A2A受体激动剂同时存在时,NOS活力进一步增高。结论高浓度谷氨酸可逆转腺苷A2A受体激动剂抑制升高NOS活力的作用。 相似文献
2.
S. NIKOLOVSKI D. L. FAULKNER T. N. PALMER P. A. FOURNIER 《Acta physiologica (Oxford, England)》1996,157(4):427-434
During recovery from high intensity exercise, substantial and rapid muscle glycogen repletion from endogenous carbon sources is reported in a variety of vertebrate species, the rat being the only reported exception. The major aim of this study was to re-examine the process of glycogen repletion during recovery from high intensity exercise in the rat. In response to 3 min of vigorous swimming, muscle glycogen concentrations decrease markedly from initial levels of 20.2±1.5 and 21.2±0.9 μmol g-1 to 6.4±1.1 and 7.9±1.4 μmol g-1 in the tibialis anterior and plantaris muscles respectively. The equivalent of 58% of the glycogen carbons mobilized during exercise by the plantaris and 73% of that mobilized by the tibialis anterior muscle is repleted within 1 h following exercise. Using the hepatectomized rat as experimental model, a secondary aim of the study was to evaluate whether the liver is essential for the repletion of muscle glycogen. Although the absence of significant differences in the magnitude of post-exercise muscle glycogen repletion between sham-operated and hepatectomized rats suggests that the resynthesis of muscle glycogen can take place in the absence of hepatic gluconeogenesis, the present study identifies several limitations in the use of acute hepatectomy. Overall, the present study indicates that, in contrast to published views, the rat resembles other vertebrates in that it can support extensive muscle glycogen repletion from endogenous carbon sources during the recovery phase following high intensity exercise. 相似文献
3.
Despite the widespread use of botulinum toxin to treat muscle dystonias, no method exists to quantify muscle paralysis in either human or nonhuman models. In this study we examined how the location, dose, and volume of botulinum injection affects paralysis in the rat tibialis anterior muscle. Paralysis was quantified by electrically stimulating the nerve to the tibialis anterior and then staining sections of the muscle for glycogen. The areas of glycogen-containing fibers represented regions of botulinum action. The results showed that the most important injection technique is to inject botulinum directly into the motor endplate region of a muscle. Injections only 0.5 cm from the motor endplate resulted in a 50% decrease in paralysis. Increases in dose increased paralysis, however, some of that increase was simply due to the increased volume of injection. Thus, delivering toxin in small volumes near the MEP band of a muscle should produce the most effectiveparalysis. © 1993 John Wiley & Sons, Inc. 相似文献
4.
放射性肝纤维化过程的定量研究 总被引:6,自引:0,他引:6
经^60Coγ线照射大鼠肝区,通过光镜、电镜和图像分析仪、宣研究了照后1年肝脏的病理改变。结果表明,30Gy组在照射后1年内逐渐发生了放射性肝纤维化病变。在肝纤维化发生过程中,肝细胞内糖原颗凿含量进行性减少,间质中胶原纤维含量进行性增加,网状纤维于照射1-3个月呈进行性增加。 相似文献
5.
6.
R. Berkels A. Bertsch T. Zuther S. Dhein K. Stockklauser P. Rsen R. Rsen 《European journal of haematology》1997,58(5):307-313
Abstract: We tried to characterize the porcine platelet nitric oxide (NO) synthase and its L-arginine (L-arg)/NO metabolism. Using RT-PCR we could show a constitutive endothelial NOS (ecNOS) and an inducible NOS (iNOS) similar mRNA in platelets. The NOS protein could be evidenced by an ecNOS specific antibody which also bound in platelets. This finding could be confirmed by Western blot showing an ecNOS in the membrane but not the cytosolic fraction; iNOS protein could not be detected. Using NADPH-diaphorase staining we could show NO synthase in preactivated platelets but not in resting platelets, indicating that the platelet NOS may be activated during platelet activation/aggregation. Porcine L-arg plasma levels (9.31 × 10–5 mol/l ± 10%) could be shown to be in the same range as human plasma levels. Moreover, we could show that the NO precursor L-arg and hydroxy-L-arginine (OHarg) concentration dependently inhibited collagen induced platelet aggregation. Summarizing these results confirm the existence of and further characterize porcine platelet NO synthases. 相似文献
7.
Rolf W. Hartmann Martin Frotscher Dorothea Ledergerber Gerald A. Wchter Gertrud L. Grün Tom F. Sergejew 《Archiv der Pharmazie》1996,329(5):251-261
In search of potential drugs for the treatment of estrogen- and androgen-dependent cancer as well as the prophylaxis of metastases, tetralones, tetralins, and dihydronaphthalenes bearing a OCH3 substituent at the benzene nucleus and an imidazol-4-yl, imidazol-1-yl, or 1,2,4-triazol-1-yl substituent in 2-position were synthesized with and without C1-spacer between the rings (compounds 2 – 26 ). The compounds were tested in vitro for inhibition of the three target enzymes P450 arom (human placental microsomes), P450 17 (rat testicular microsomes), and P450 TxA2 (citrated human whole blood). To examine selectivity, some compounds were further tested in vitro for inhibition of P450 18 (bovine adrenal mitochondria), P450 see (bovine adrenal mitochondria) and corticoid formation (aldosterone, corticosterone; ACTH stimulated rat adrenal tissue). In vivo, selected compounds were examined in Sprague Dawley rats regarding P450 TxA2 inhibition, reduction of plasma testosterone concentration, antiuterotrophic activity (inhibition of the uterotrophic activity of androstenedione), reduction of plasma estradiol concentration (pregnant mares' serum gonadotropin-primed rats), and mammary tumor inhibiting activity (dimethylbenzanthracene-induced tumor; pre- and postmenopausal model). In the series of imidazol-4-yl compounds, which represent a novelty in the field of azole inhibitors of steroidogenic P450 enzymes, strong inhibitors of P450 arom and/or P450 17 were found: 7-OCH3-2-(imidazol-4-ylmethylene)-1-tetralone ( 4 ) and 7-OCH3-2-(imidazol-4-ylmethyl)-tetralin ( 12 ) are among the most potent inhibitors of P450 arom in vitro known so far. Compound 4 is a selective inhibitor, whereas 12 shows in addition strong inhibition of P450 17. In contrast to 12 , the 6-OCH3 derivative (compound 11 ) is a selective inhibitor of P450 17, being 50 times more potent than ketoconazole. Some imidazol-1-yl compounds show a marked inhibition of P450 TxA2: 2-(imidazol-1-ylmethyl)-1-tetralone ( 13 ) is a selective inhibitor of P450 TxA2, whereas 7-OCH3-2-(imidazol-1-ylmethyl)-tetralin ( 17 ) as well as 2-(imidazol-1-ylmethyl)-tetralin ( 16 ) and 7-OCH3-2-imidazol-1-yl-3,4-dihydronaphthalene ( 25 ) additionally show strong inhibition of P450 arom and P450 17. Regarding the other steroidogenic P450 enzymes as well as corticosterone formation, the compounds show only little inhibitory activity. Aldosterone formation, however, is inhibited at low concentrations. Nevertheless, 4 and 12 are more selective, i.e. inhibit aldosterone synthesis less than the well known inhibitor of P450 arom fadrozole. The compounds show activity in the aforementioned in vivo tests. 相似文献
8.
D. Ramsbottom J.M. Scott A. Molloy D. G. Weir P. N. Kirke J. L. Mills P. M. Gallagher A. S. Whitehead 《Clinical genetics》1997,51(1):39-42
Mildly elevated maternal plasma homocysteine (Hcy) levels (hyperhomocysteinemia) have recently been observed in some neural tube defect (NTD) pregnancies. Plasma levels of Hcy are governed by both genetic and nutritional factors and the aetiology of NTDs is also known to have both genetic and nutritional components. We therefore examined the frequency of relatively common mutations in the enzyme cystathionine β-synthase (CBS), which is one of the main enzymes that controls Hcy levels, in the NTD population. Neither the severely dysfunctional G307S CBS allele nor the recently reported 68 bp insertion/I278T CBS allele was observed at increased frequency in the cases relative to controls. We therefore conclude that loss of function CBS alleles do not account for a significant proportion of NTDs in Ireland. 相似文献
9.
H. Faber-Zuschratter T. Seidenbecher K. Reymann G. Wolf 《Journal of neural transmission (Vienna, Austria : 1996)》1996,103(7):807-817
Summary The distribution of the enzyme nitric oxide synthase (NOS) was investigated at the ultrastructural level in synaptic structures of the hippocampal formation in relation to long-term potentiation (LTP), based on the histochemical NADPH-diaphorase (NADPH-d) staining with the tetrazolium salt BSPT. BSPT-formazan, the osmiophilic reaction product, was found to be selectively distributed and predominantly attached to membranes of the endoplasmic reticulum. In synaptic regions mainly the presynaptic sides showed labeling. Although several groups have demonstrated a principal involvement of NO in the LTP-mechanism, we found only a low, statistically insignificant increase in NADPH-d stained presynaptic areas of the dentate gyrus, where LTP was evoked. Postsynaptic elements also did not show any noticeable differences. Based on the present results, the predominantly presynaptic localization of NOS should be preferably considered in models describing a functional role of NO in LTP formation, despite the fact that we failed to reveal any indications for an LTP-related change in synaptically located NADPH-d. 相似文献
10.