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941.
Miconia howardiana, which is known only from a diverse moist montane forest in the vicinity of Loma Trocha de Pey (or “Monteada Nueva”), the
easternmost peak of the Sierra de Baoruco, is described and illustrated. It is compared to phenetically similar (and probably
phylogenetically related) species of theMiconia favosa complex, i.e.,M. favosa, M. xenotricha, M. campanensis M. Sintenisii, M. foveolata, andM. pycnoneura. The species of this complex are characterized by bullate leaves with frequently cordate bases and often six secondary veins.
Most species also have large berries and flowers, 5-locular ovaries, large inflorescence bracts and bracteoles, and more or
less dendritic multicellular hairs. 相似文献
942.
Cellular Basis and Developmental Timing in a Size Cline of Drosophila Melanogaster 总被引:2,自引:1,他引:1 下载免费PDF全文
We examined 20 Drosophila melanogaster populations collected from a 2600-km north-south transect in Australia. In laboratory culture at constant temperature and standard larval density, a genetic cline in thorax length and wing area was found, with both traits increasing with latitude. The cline in wing area was based on clines in both cell size and cell number, but was primarily determined by changes in cell number. Body size and larval development time were not associated among populations. We discuss our results in the context of selection processes operating in natural and experimental populations. 相似文献
943.
David A. Flemer Roman S. Stanley Barbara F. Ruth Charles M. Bundrick Paul H. Moody James C. Moore 《Hydrobiologia》1995,308(2):85-101
Two six-week laboratory experiments were conducted to evaluate effects of pesticides and microcosm size on benthic estuarine
macroinvertebrate recolonization. Sediments fortified with the pesticides (fenvalerate: controls, 5 (low) and 50 μg g−1 wet sediment (high); endosulfan: controls, 1 (low) and 10 μg g−1 wet sediment (high)) were fine-grained, organically rich (approximately 3.5% organic carbon and 22% dry weight) material.
Relative dominance of the four most abundant taxa in both experiments was consistent among treatments with few exceptions.
The amphipod,Corophium acherusicum, dominated abundance in both experiments.
In the fenvalerate experiment, large trays (400 cm2) contained significantly (p<0.05) more total number of taxa (TNT) than small microcosms (144 cm2) but tray size was not significantly related to total number of organisms (TNO). When size was adjusted to a common unit
area, small trays contained significantly more TNO than large containers. Adjusted abundance of small trays was 2.5 times
that of large containers; a ratio close to that of microcosm sizes (i.e., 2.8). This result suggests that larval supply may have been inadequate to ‘aturate’ the available sediment in large containers.
Fenvalerate significantly reduced abundance in the high treatment compared to both controls and low treatment but low treatment
was not significantly different from controls. The amphipod,Corophium acherusicum, accounted for most of the decrease in abundance in response to fenvalerate. The holothruroid,Leptosynpta sp. and the polychaete,Mediomastus ambiseta, increased in abundance significantly with increased concentration of fenvalerate.
Combined effects of actual microcosm size and concentration of endosulfan were not significant for TNO or TNT. As in the fenvalerate
experiment, adjusted abundance of small microcosms was 2.6 times that of large trays which approximated the ratio of unit
area between microcosm sizes. Abundance of a few taxa responded significantly to adjusted and unadjusted unit area. Abundance
of the tunicate,Molgula manhattensis, increased significantly with increased concentration of endosulfan. Abundance was affected by sample location (e.g., interiorvs exterior cores) within microcosms. Abundance adjusted to unit area resulted in significantly greater TNO in externalvs internal cores. This has importance for sequential sub-sampling of microcosms to determine temporal dynamics.
Statistically significant effects were measured in benthic community structure associated with microcosm size; however, the
magnitude was relatively small. There appears to be no major biological reason to select one microcosm size over the other
for screening for contaminant effects. Where feasible, the small trays provide savings in sample preparation and analysis,
allow more replicates where laboratory space is limiting and generate less chemical waste. These benefits may be off-set by
less ‘artifacts’ associated with edge effects of larger microcosms and the need for a larger mass of sediment to accommodate
additional analytical requirements (e.g., thin vertical surficial samples to refine contaminant exposure at the sediment/water
interface). 相似文献
944.
Paul G. Braunschweiger Vathsala S. Basrur Dayna Cameron Laura Sharpe Octavio Santos James P. Perras Bernd-Uwe Sevin Arnold M. Markoe 《Biotherapy》1997,10(2):129-137
The modulation of cisPlatin cytotoxicity by interleukin-1 (IL-1α) was studied in cultures of SCC-7 tumor cells with and without
tumor macrophages to examine potential mechanisms for the synergistic antitumor activity of cisPlatin and IL-1α in SCC-7 solid
tumors. Neither IL-1α nor tumor macrophages affected the survival of clonogenic tumor cells and IL-1α had no direct effect
on tumor cell growthin vitro. Macrophages had no direct effect on cisPlatin sensitivity (IC90=6.0 μM), but, the addition of IL-1α (500–2000U/ml) to co-cultures of cisPlatin pretreated tumor cells and resident tumor
macrophages increased cell killing (IC90=3.1 μM). Similar responses were seen in primary cultures treated with cisPlatin before IL-1α. The modulation of cisPlatin
cytotoxicity by IL-1α exhibited a biphasic dose response that paralleled the IL-1α dose dependent release of H2O2by resident tumor macrophages. Further, IL-1α modification of cisPlatin cytotoxicity was prompt and inhibited by catalase.
CisPlatin and exogenous H2O2 (50 μM) produced more than additive SCC-7 clonogenic cell kill and hydroxyl radicals played an important role in the response.
Interleukin-1 modulation of cisPlatin cytotoxicity was schedule dependent. IL-1α treatment for 24 hrs, before cisPlatin, produced
drug resistance (IC90=11.1 μM). Our study shows that IL-1α can stimulate tumor macrophages to release pro-oxidants that modify cellular chemosensitivity
in a schedule and dose dependent fashion. Our findings may also provide a mechanistic explanation for the synergistic antitumor
activity of cisPlatin and IL-1αin vivo. 相似文献
945.
The genusPereskia, which contains numerous morphological features considered relictual in the Cactaceae, has numerous anatomical features that
we consider to be relictual also. These were studied to establish a basis for determining the ways that morphogenic mechanisms
and anatomical characters diversified as the family evolved. ThesePereskia features may be relictual in the family: epidermis predominantly unistratose and lacking crystals; hypodermis absent or of
about three layers of weakly collenchymatous cells with druses; cortex thin and predominantly parenchyma with druses and mucilage
cells but lacking cortical bundles; secondary phloem without early differentiation of sclerenchyma but with secondary sclereids
developing later, either idioblastically or in clusters; ergastic substances lacking from old secondary phloem; wood with
a matrix of libriform fibers (mostly septate and nucleate), scanty paratracheal parenchyma, vessels solitary or in small clusters,
perforations simple, pitting circular, oval or very broad; wide-band tracheids absent; ray cells slightly thick-walled, lignified,
upright, isodiametric or procumbent; all primary rays narrow; pith without medullary bundles; leaves lacking hypodermis, with
only weak development of palisade mesophyll; veins of four orders, strongly distinct in size, none with fibers; vessels in
leaves narrower than those in stems. 相似文献
946.
A whole-genome radiation hybrid panel for bovine gene mapping 总被引:15,自引:0,他引:15
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