全文获取类型
收费全文 | 4055篇 |
免费 | 245篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 59篇 |
儿科学 | 86篇 |
妇产科学 | 24篇 |
基础医学 | 637篇 |
口腔科学 | 75篇 |
临床医学 | 298篇 |
内科学 | 746篇 |
皮肤病学 | 141篇 |
神经病学 | 476篇 |
特种医学 | 304篇 |
外科学 | 587篇 |
综合类 | 22篇 |
一般理论 | 1篇 |
预防医学 | 169篇 |
眼科学 | 90篇 |
药学 | 240篇 |
中国医学 | 6篇 |
肿瘤学 | 355篇 |
出版年
2023年 | 20篇 |
2022年 | 45篇 |
2021年 | 81篇 |
2020年 | 51篇 |
2019年 | 64篇 |
2018年 | 63篇 |
2017年 | 50篇 |
2016年 | 88篇 |
2015年 | 103篇 |
2014年 | 144篇 |
2013年 | 190篇 |
2012年 | 300篇 |
2011年 | 303篇 |
2010年 | 156篇 |
2009年 | 159篇 |
2008年 | 255篇 |
2007年 | 223篇 |
2006年 | 205篇 |
2005年 | 200篇 |
2004年 | 181篇 |
2003年 | 199篇 |
2002年 | 180篇 |
2001年 | 90篇 |
2000年 | 92篇 |
1999年 | 84篇 |
1998年 | 61篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 16篇 |
1992年 | 35篇 |
1991年 | 35篇 |
1990年 | 31篇 |
1989年 | 47篇 |
1988年 | 39篇 |
1987年 | 27篇 |
1986年 | 29篇 |
1985年 | 28篇 |
1984年 | 35篇 |
1983年 | 24篇 |
1982年 | 23篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 24篇 |
1978年 | 23篇 |
1977年 | 14篇 |
1975年 | 15篇 |
1974年 | 10篇 |
1935年 | 16篇 |
排序方式: 共有4316条查询结果,搜索用时 15 毫秒
41.
Bhatia E Choudhuri G Sikora SS Landt O Kage A Becker M Witt H 《Gastroenterology》2002,123(4):1020-1025
BACKGROUND & AIMS: Tropical calcific pancreatitis (TCP) is a chronic pancreatitis unique to developing countries in tropical regions. The cause of TCP is obscure. Whereas environmental factors, such as protein energy malnutrition and ingestion of cassava, have been implicated, a genetic predisposition to the disease also may be important. In the present study we report on mutations in the serine protease inhibitor, Kazal type 1 (SPINK1) gene in north Indian patients with TCP. METHODS: We studied 66 unrelated TCP patients (44 men, 49 with diabetes, and 6 with family history of TCP), 25 relatives, and 92 healthy control subjects. Samples were analyzed for SPINK1 variants (-53C>T, L14P, N34S, P55S, and 272T>C) and cationic trypsinogen (PRSS1) variants (A16V, K23R, N29I, and R122H) by melting curve analysis. RESULTS: Twenty-nine patients (44%) carried the N34S missense mutation, of whom 9 (14%) were homozygotes. In contrast, only 2 (2.2%) control subjects were N34S heterozygotes (prevalence ratio 20.2; 95% confidence interval 5.0-81.8; P < 0.0001 vs. TCP). The severity of pancreatitis did not differ between TCP patients with or without N34S, or among those heterozygous or homozygous for N34S. Among TCP patients with or without diabetes, the frequency of N34S carriers (43% vs. 47%) and N34S homozygotes (14% vs. 12%) was similar. CONCLUSIONS: TCP is highly associated with the SPINK1 N34S mutation. The high prevalence of N34S in TCP patients with and without diabetes suggests that these 2 subtypes have a similar genetic predisposition. The genetic predisposition to TCP resembles, at least in part, the idiopathic chronic pancreatitis found in industrialized countries. 相似文献
42.
David Pfister Giuseppe Storti Francesca Tancini Liborio I. Costa Massimo Morbidelli 《Macromolecular chemistry and physics.》2015,216(21):2141-2146
A new synthetic pathway for the polymerization of furan based polyesters is reported in this work. First, poly(butylene 2,5‐furandicarboxylate) cyclic oligoesters (COEs) are chemically synthesized by semi‐batch esterification. The structure of the COEs is confirmed by infrared spectroscopy, 1H, and 13C‐NMR, while the molecular weight distribution of the COEs is determined by matrix‐assisted laser desorption/ionization time of flight mass spectroscopy. The cyclic oligoesters are then successfully polymerized via ring‐opening polymerization using tetrakis(2‐ethylhexyl)‐titanate as catalyst. Differential scanning calorimetry and 1H‐NMR analysis unambiguously proves the formation of polymeric species. Both end‐group analysis from 1H‐NMR spectrum and calculation through Flory–Fox equation give comparable estimates of the number average molecular weight: 5.8 × 103 g mol?1 and 7.8 × 103 g mol?1, respectively.
43.
44.
3D matrix‐embedding inhibits cycloheximide‐mediated sensitization to TNF‐alpha‐induced apoptosis of human endothelial cells 下载免费PDF全文
Michael Saemisch Markus Nickmann Lisa Riesinger Elazer R. Edelman Heiko Methe 《Journal of tissue engineering and regenerative medicine》2018,12(4):1085-1096
The programmed form of cell death (apoptosis) is essential for normal development of multicellular organisms. Dysregulation of apoptosis has been linked with embryonal death and is involved in the pathophysiology of various diseases. Others and we previously demonstrated endothelial biology being intertwined with biochemical and structural composition of the subendothelial basement membrane. We now demonstrate that a three‐dimensional growing environment significantly shields endothelial cells from cytokine‐induced apoptosis. Detailed analysis reveals differences in intracellular signaling pathways in naive endothelial cells and cytokine‐stimulated endothelial cells when cells are grown within a three‐dimensional collagen‐based matrix compared to cells grown on two‐dimensional tissue culture plates. Main findings are significantly reduced p53 expression and level of p38‐phosphorylation in three‐dimensional grown endothelial cells. Despite similar concentrations of focal adhesion kinase, three‐dimensional matrix‐embedded endothelial cells express significantly less tyrosine‐phosphorylated focal adhesion kinase. Pretreatment with antibodies against integrin αvβ3 partially reversed the protective effect of three‐dimensional matrix‐embedding on endothelial apoptosis. Our findings provide detailed insights into the mechanisms of endothelial apoptosis with respect to the spatial matrix environment. These results enhance our understanding of endothelial biology and may otherwise help in the design of tissue‐engineered materials. Furthermore, findings on focal adhesion kinase phosphorylation might enhance our understanding of clinical studies with tyrosine kinase inhibitors. 相似文献
45.
46.
47.
The present study investigated the role of arachidonic acid and acetylcholine in mediating endothelium-dependent relaxations of rabbit aorta. Isolated thoracic aortic rings were precontracted with a submaximal concentration of norepinephrine, and the effect of various agents on arachidonic acid- and acetylcholine-induced relaxations was examined. Arachidonic acid elicited a concentration-related relaxation that was potentiated by the cyclooxygenase inhibitor indomethacin. Treatment with the lipoxygenase inhibitor nordihydroguaiaretic acid completely blocked but the cytochrome P450 inhibitor metyrapone had no effect on arachidonic acid-induced relaxation. NG-Monomethyl-L-arginine and nitro-L-arginine, compounds that inhibit the nitric oxide-like endothelium-derived relaxing factor, had little or no effect on arachidonic acid-induced relaxations. In contrast, nordihydroguaiaretic acid, metyrapone, NG-monomethyl-L-arginine, and nitro-L-arginine all attenuated the relaxation to acetylcholine; however, indomethacin had no effect on acetylcholine-induced relaxations. Arachidonic acid and acetylcholine had no effect on denuded rabbit aorta. Incubation of rabbit aorta with [14C]arachidonic acid resulted in the synthesis of major radioactive metabolites that comigrated with the prostaglandins and hydroxyeicosatetraenoic acids. Indomethacin selectively inhibited prostaglandin formation, nordihydroguaiaretic acid attenuated both prostaglandins and hydroxyeicosatetraenoic acids, and metyrapone blocked the epoxyeicosatrienoic acids. Additionally, acetylcholine elicited a twofold increase in tissue cyclic guanosine monophosphate content in contrast to a 59% reduction in cyclic guanosine monophosphate content observed with arachidonic acid. Therefore, these data suggest that in rabbit aorta, arachidonic acid-induced relaxations are mediated by an endothelium-dependent factor (or factors) that differs from the factor (or factors) released by acetylcholine. These results support the existence of multiple endothelium-derived relaxing factors. 相似文献
48.
Summary
Conclusion
Proteinase-activated receptor-2 (PAR-2)-mediated effects contribute to the intracellular signaling network in pancreatic tumor
cells. A role of PAR-2 as negative regulator in human pancreatic tumor growth might be implied.
Background Using the human pancreatic tumor cell line MIA PaCa-2, we evaluated cellular effects of trypsin and the PAR-2-activating peptide
SLIGRL on [Ca2+]i mobilization, Ins(1,4,5)P3 level, and protein kinase (PKC) activation. Furthermore, PAR-2 involvement in the regulation of cell proliferation has been
estimated by measurement of [3H]thymidine incorporation in MIA PaCa-2 cells.
Results Trypsin and the PAR-2 synthetic peptide agonist SLIGRL induced [Ca2+]i mobilization, transient increase in inositol (1,4,5) triphosphate level, and PKC translocation in MIA PaCa-2 cells. In addition,
SLIGRL induced a decrease in DNA synthesis in MIA PaCa-2 cells. 相似文献
49.
Heiko?AselmannEmail authorView authors OrcID profile Jan-Niclas?Kersebaum Alexander?Bernsmeier Jan?Henrik?Beckmann Thorben?M?ller Jan?Hendrik?Egberts Clemens?Schafmayer Christoph?R?cken Thomas?Becker 《International journal of colorectal disease》2018,33(11):1575-1581
Aim
Robotic surgery allows for a better visualization and more precise dissection especially in the narrow male pelvis and mid and lower third of the rectum. However, superiority to laparoscopic TME has yet to be proven. We therefore analyzed short-term outcomes of laparoscopic and robotic low anterior rectal resection for rectal cancer.Patients and methods
From 2011 to 2016, 44 robotic (RTME) and 41 laparoscopic (LTME) low anterior rectal resection with total mesorectal excision were performed at a single institution. Specimen quality was assessed and reported by an independent pathologist following international guidelines.Results
The groups did not differ significantly regarding gender, age, ASA stage, BMI, and distance of the lower tumor margin from the anal verge. More patients in the RTME group underwent preoperative chemoradiation (43.2 vs. 19.5%, p?=?0.019). The quality of the TME specimen was significantly better in the RTME group (complete/nearly complete/incomplete for RTME 97/0/3% and for LTME 78/17/5%, p?=?0.03). The conversion rate tended to be lower in the RTME group (7 vs. 17%, p?=?0.143). There was no difference in CRM positivity between the groups.Conclusion
Robotic surgery is safe and can improve the quality of TME for rectal cancer compared to laparoscopy. Any effect on long-term survival remains to be established.50.
Markus Janczyk Roland Pfister Wilfried Kunde 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2013,231(1):97-106
Human–Computer Interactions pose special demands on the motor system, especially regarding the virtual tool transformations underlying typical mouse movements. We investigated whether such virtual tool-transformed movements are similarly resistant to irrelevant variation of a target object as skilled natural movements are. Results show that such irrelevant information deteriorates performance in perceptual tasks, whereas movement parameters remain unaffected, suggesting that the control of virtual tools draws on the same mechanisms as natural actions do. The results are discussed in terms of their practical utility and recent findings investigating unskilled and transformed movements in the framework of the action/perception model and the integration of tools into the body schema. 相似文献