全文获取类型
收费全文 | 5185篇 |
免费 | 625篇 |
国内免费 | 2篇 |
专业分类
5812篇 |
出版年
2021年 | 51篇 |
2018年 | 62篇 |
2017年 | 51篇 |
2016年 | 92篇 |
2015年 | 156篇 |
2014年 | 157篇 |
2013年 | 202篇 |
2012年 | 223篇 |
2011年 | 237篇 |
2010年 | 149篇 |
2009年 | 129篇 |
2008年 | 185篇 |
2007年 | 163篇 |
2006年 | 183篇 |
2005年 | 155篇 |
2004年 | 151篇 |
2003年 | 124篇 |
2002年 | 184篇 |
2001年 | 170篇 |
2000年 | 159篇 |
1999年 | 148篇 |
1998年 | 68篇 |
1997年 | 45篇 |
1996年 | 62篇 |
1995年 | 82篇 |
1994年 | 59篇 |
1993年 | 72篇 |
1992年 | 134篇 |
1991年 | 117篇 |
1990年 | 137篇 |
1989年 | 98篇 |
1988年 | 119篇 |
1987年 | 109篇 |
1986年 | 91篇 |
1985年 | 100篇 |
1984年 | 81篇 |
1983年 | 74篇 |
1982年 | 76篇 |
1981年 | 73篇 |
1980年 | 67篇 |
1979年 | 95篇 |
1978年 | 91篇 |
1977年 | 67篇 |
1976年 | 64篇 |
1975年 | 56篇 |
1973年 | 49篇 |
1972年 | 58篇 |
1971年 | 50篇 |
1968年 | 40篇 |
1967年 | 43篇 |
排序方式: 共有5812条查询结果,搜索用时 0 毫秒
141.
Antimicrobial susceptibility monitoring of dermatological bacterial pathogens isolated from diseased dogs and cats across Europe (ComPath results) 下载免费PDF全文
C. Ludwig A. de Jong H. Moyaert F. El Garch R. Janes U. Klein I. Morrissey J. Thiry M. Youala 《Journal of applied microbiology》2016,121(5):1254-1267
142.
Ohne Zusammenfassung 相似文献
143.
Yingjuan Lu Nikki Parker Paul J Kleindl Vicky A Cross Kristin Wollak Elaine Westrick Torian W Stinnette Mark A Gehrke Kevin Wang Hari Krishna R Santhapuram Fei You Spencer J Hahn Jeremy F Vaughn Patrick J Klein Iontcho R Vlahov Philip S Low Christopher P Leamon 《Molecular medicine (Cambridge, Mass.)》2015,21(1):584-596
Folate receptor (FR)-β has been identified as a promising target for antimacrophage and antiinflammatory therapies. In the present study, we investigated EC0565, a folic acid–derivative of everolimus, as a FR-specific inhibitor of the mammalian target of rapamycin (mTOR). Because of its amphiphilic nature, EC0565 was first evaluated for water solubility, critical micelle formation, stability in culture and FR-binding specificity. Using FR-expressing macrophages, the effect of EC0565 on mTOR signaling and cellular proliferation was studied. The pharmacokinetics, metabolism and bioavailability of EC0565 were studied in normal rats. The in vivo activity of EC0565 was assessed in rats with adjuvant arthritis, a “macrophage-rich” model with close resemblance to rheumatoid arthritis. EC0565 forms micellar aggregates in physiological buffers and demonstrates good water solubility as well as strong multivalent FR-binding capacity. EC0565 inhibited mTOR signaling in rat macrophages at nanomolar concentrations and induced G0/G1 cell cycle arrest in serum-starved RAW264.7 cells. Subcutaneously administered EC0565 in rats displayed good bioavailability and a relatively long half-life (~12 h). When given at 250 nmol/kg, EC0565 selectively inhibited proliferating cell nuclear antigen expression in thioglycollate-stimulated rat peritoneal cells. With limited dosing regimens, the antiarthritic activity of EC0565 was found superior to that of etanercept, everolimus and a nontargeted everolimus analog. The in vivo activity of EC0565 was also comparable to that of a folate-targeted aminopterin. Folate-targeted mTOR inhibition may be an effective way of suppressing activated macrophages in sites of inflammation, especially in nutrient-deprived conditions, such as in the arthritic joints. Further investigation and improvement upon the physical and biochemical properties of EC0565 are warranted. 相似文献
144.
145.
Cell-mediated lymphocytotoxicity was generated in four strain combinations differing only by the cell-surface expression of the class II E molecule controlled by the H-2 complex. The four combinations were: B10.D2(R107) anti-B10.A(3R), B10.A(4R) anti-B10.A(2R), B10.GD anti-B10.D2(R101), and B10.S(7R) anti-B10.S(9R). In all four of these combinations, the stimulator expresses E molecules on the cell surface, while the responder does not. The cytolytic T lymphocytes generated in the B10.D2(R107) anti-B10.A(3R) and B10.A(4R) anti-B10.A(2R) combinations reacted not only with the stimulator but also with strains that do not express cell-surface E molecules, in particular, strains carrying the H-2
f
and H-2
q
haplotypes. The cross-reactivity with E-negative strains could be blocked by monoclonal antibodies specific for the Af or Aq molecules but not by antibodies recognizing determinants on E or class I (K) molecules. The anti-H-2f cross-reactivity could be inhibited by H-2
q
cold targets and, reciprocally, the anti-H-2q reactivity could be blocked by H-2
f
cold targets. These findings are interpreted as indicating that the cytolytic T lymphocytes stimulated by E molecules can recognize and lyse cells lacking E molecules but expressing A molecules. The observed E-A cross-reactivity supports the notion of structural and functional relatedness between the A and E molecules and suggests a common evolutionary origin of the A- and E-encoding loci. 相似文献
146.
J E Morley C Klein W J Kalk B I Joffe D Saffer L A Distiller H C Seftel 《Hormones et métabolisme》1978,10(3):231-237
The pituitary responses to the intravenous administration of 200 mg of Thyrotropin Releasing Hormone were investigated in 14 poorly controlled insulin dependent diabetic males and in nine matched controls. The mean TSH and prolactin responses in the two groups were similar although both tended to be lower in the diabetics. There was a small FSH rise in 11 of the 23 subjects. 相似文献
147.
We investigated the long-term effects of divorce and early separation from one parent on HPA axis reactivity, in young adults without psychopathology. Participants were 44 young subjects, 22 whose parents divorced before they reached age 10, and 22 controls. Psychiatric symptomatology was measured with the Brief Symptom Inventory (BSI), family perceived stress by the Dyadic Adjustment Scale (DAS), and bonding by the Parental Bonding Instrument (PBI). Assessment of HPA axis function included baseline morning cortisol and ACTH and cortisol response to a CRH stimulation test. No baseline or stimulated group differences were observed for ACTH. Cortisol levels were consistently but insignificantly lower in the divorce group throughout the CRH stimulation reaching statistical significance only at 5 min (p<0.03). Group by time effect reached a trend level (p<0.06). A correlation was found between psychiatric symptomatology and PBI scores; however, both parameters did not correlate with HPA axis activity. A significant correlation was found between DAS scores and ACTH. A regression model revealed a contributing effect for both family stress and child-parent bonding to stimulated ACTH levels. These preliminary findings suggest that even in the absence of adult psychopathology, a history of childhood separation from one parent due to divorce may lead to detectable, albeit mild, long-term alterations in HPA axis activity. Furthermore, they suggest that level of stress at home and parental bonding are important determinants of this effect. It is likely that divorce has significant and sustained effects on children's HPA axis only in the context of a traumatic separation. 相似文献
148.
Richard G. Klein 《Evolutionary anthropology》2019,28(4):179-188
It has been proposed that a multiregional model could describe how Homo sapiens evolved in Africa beginning 300,000 years ago. Multiregionalism would require enduring morphological or behavioral differences among African regions and morphological or behavioral continuity within each. African fossils, archeology, and genetics do not comply with either requirement and are unlikely to, because climatic change periodically disrupted continuity and reshuffled populations. As an alternative to multiregionalism, I suggest that reshuffling produced novel gene constellations, including one in which the additive or cumulative effect of newly associated genes enhanced cognitive or communicative potential. Eventual fixation of such a constellation in the lineage leading to modern H. sapiens would explain the abrupt appearance of the African Later Stone Age 50–45 thousand years ago, its nearly simultaneous expansion to Eurasia in the form of the Upper Paleolithic, and the ability of fully modern Upper Paleolithic people to swamp or replace non‐modern Eurasians. 相似文献
149.
Effect of high temperature on calcium uptake by suspension-cultured pear fruit cells 总被引:9,自引:0,他引:9 下载免费PDF全文
Uptake of Ca2+ by suspension-cultured pear (Pyrus communis L. cv Passe Crassane) cells and protoplasts was significantly enhanced by exposure to 38°C compared to 25°C. The increased uptake was specific for Ca2+ and was not due to cell wall binding. Tissues pretreated at 38°C showed increased uptake even upon return to 25°C. Treatment with carbonylcyanide m-chlorophenylhydrazone, salicylhydroxamic acid + KCN, or arsenite also increased Ca2+ content of cells. Results are discussed with regard to membrane permeability changes, the cellular control of Ca2+, and heat treatments used to inhibit softening of fruit during postharvest storage. 相似文献
150.